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Publication numberUS20100041529 A1
Publication typeApplication
Application numberUS 12/475,821
Publication dateFeb 18, 2010
Filing dateJun 1, 2009
Priority dateMay 30, 2008
Publication number12475821, 475821, US 2010/0041529 A1, US 2010/041529 A1, US 20100041529 A1, US 20100041529A1, US 2010041529 A1, US 2010041529A1, US-A1-20100041529, US-A1-2010041529, US2010/0041529A1, US2010/041529A1, US20100041529 A1, US20100041529A1, US2010041529 A1, US2010041529A1
InventorsBrian Weinberg, Azadeh Khanicheh, Constantinos Mavroidis, James Shannon, Don Consolini, George Galanis
Original AssigneeNortheastern University, Wgi D/B/A Westfield Gage Co. Overhaul And Repair
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Variable resistance hand rehabilitation device with linear smart fluid damper and dynometer capabilities
US 20100041529 A1
Abstract
A variable resistance hand rehabilitation device and corresponding system. Improvements over the prior art include: a new damping system or damper design, to reduce friction and increase maximum force output; a dynometer feature that enables converting the dynamic device to a static grip force measuring device; a closed-loop controller; and a new graphic user interface for the medical practitioner and new virtual reality game software that allow accurate and smooth operation of the device and increased patient motivation.
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Claims(31)
1. A variable resistance hand rehabilitation device adapted to provide a controllable velocity or a controllable resistive force during exercises of a mammalian extremity, the device comprising:
a support structure for providing strength and structure to the device;
a handle portion moveable in a single degree of freedom and by which the extremity performs the exercises;
a controllable damping system that is structured and arranged to provide a selectively controlled resistance to the extremity using an electro-rheological fluid having a resistivity that is continuously variable throughout a stroke cycle; and
at least one sensing device, each of which is mechanically coupled to the handle portion and each of which is adapted to provide measurement data for controlling the resistivity of the electro-rheological fluid.
2. The device as recited in claim 1, wherein the handle portion includes a first, movable handle portion and a second, fixed handle portion, the first, movable hand portion having a single degree of freedom of movement in the direction of the fixed handle portion.
3. The device as recited in claim 2, wherein the at least one sensing devices includes at least one of:
a linear potentiometer that is mechanically coupled to the movable handle portion and adapted to measure linear displacement of the handle portion during a stroke cycle; and
a linear force sensing device that is mechanically coupled to said movable handle portion and adapted to measure a force or pressure applied by a mammalian extremity throughout the stroke cycle.
4. The device as recited in claim 1 further comprising at least one of:
a locking mechanism that is adapted to lock the shaft in a fixed position so that the device provides static rather than dynamic data; and
a handle return force control system that is adapted to return the handle portion to a starting point of the stroke elastically.
5. The device as recited in claim 4, wherein the handle return force control system is structured and arranged to return the handle portion to a start position of the stroke after completion of the stroke cycle, the handle return system comprising:
a pair of notched scales having a plurality of positioning notches, each of the pair being disposed at a distal end of the support structure;
a pair of slidable mounts, each of the pair being slidably disposed on one of the pair of notched scales and being structured and arranged to be fixedly attachable at a desired, discrete positioning notch on the corresponding notched scale; and
a pair of elongate members, each of the pair being fixedly attached to one of the pair of slidable mounts at a first end and to one of the at least one sensing device at a second end.
6. The device as recited in claim 1, wherein the controllable damping system includes:
at least one electrode that is structured and arranged as coaxial, concentric cylinder, a gap for the transmission of the electro-rheological fluid being formed between adjacent electrodes or between a single electrode and another surface in the damping system; and
a protective damper case, the case including:
a center damper case having an inner bore that is adapted to provide a tight interference fit with an outermost electrode of said at least one electrode;
a case manifold that is releasably attachable to one end of the center damper case; and
a case end cover that is releasably attachable to another, opposite end of the center damper case.
7. The device as recited in claim 6, wherein the center damper case is precision manufactured of polyoxymethylene.
8. The device as recited in claim 6, wherein the case manifold includes at least one of:
at least one electrode alignment tab, each of said alignment tab having a thickness that is equal to the gap distance; and
a plurality of electrode alignment pin holes that are structured and arranged to be in registration with a corresponding plurality of alignment pin holes that are disposed on each end of each of the plurality of electrodes; and
a gland that is adapted for holding a sealing device.
9. The device as recited in claim 8, the sealing device being selected from a group comprising: an o-ring and a spring seal.
10. The device as recited in claim 6, wherein the case end cover includes at least one of:
at least one electrode alignment tab, each of said alignment tab having a thickness that is equal to the gap distance;
a plurality of electrical connection holes that are adapted to receive an electrical connection device;
at least one air trap, each of the at least one air trap being fluidly coupled to a corresponding slide valve;
a plurality of electrode alignment pin holes that are structured and arranged to be in registration with a corresponding plurality of alignment pin holes that are disposed on each end of each of the plurality of electrodes; and
a screw cap for sealing a top of a volume compression chamber.
11. The device as recited in claim 6, wherein the case end cover includes a volume compression chamber that is filled with a closed-cell foam.
12. The device as recited in claim 1, further comprising a controller for controlling the controllable damping system and for receiving measurement data from the at last one sensing device, the controller structured and arranged to vary a magnitude of voltage delivered to an electrode that is electrically coupled to the damping system or a duration of voltage delivery, said voltage being adapted to tune the resistivity of the electro-rheological fluid, to provide a desired isokinetic or isotonic response.
13. The device as recited in claim 1, wherein the at least one electrode includes an central bore electrode, a middle electrode, and an outer electrode.
14. The device as recited in claim 13, wherein the central bore electrode has a negative polarity, the middle electrode has a positive polarity, and the outer electrode has a negative polarity.
15. The device as recited in claim 13, wherein each of said at least one electrode has a height and the height of the middle electrode is less than the height of the central bore and outer electrodes.
16. The device as recited in claim 15, wherein a spacer is provided for fine tuning the damping system.
17. The device as recited in claim 11, wherein the closed-cell foam is buna-based or a neoprene-based closed-cell foam.
18. The device as recited in claim 12, wherein the controller is adapted to provide an isotonic or isokinetic motion to the movable handle portion.
19. The device as recited in claim 12, wherein the controller is adapted to account for any Stribeck effect.
20. The device as recited in claim 1, the at least one electrode being a single electrode and the damping system further comprising a choke assembly having a through hole through which the electro-rheological fluid is forced from the damping chamber to a volume compression chamber and vice versa.
21. The device as recited in claim 1, the device having a rolling diaphragm seal to provide a rolling seal.
22. The device as recited in claim 1 further comprising a second, spring-biased piston that is structured and arranged to act in an opposite direction as the damping piston.
23. The device as recited in claim 21, wherein an electro-rheological fluid valve is disposed between the damping piston and the spring-biased piston.
24. The device as recited in claim 23, wherein the electro-rheological fluid valve includes plural positive polarity members and plural negative polarity members.
25. A rotary damping system for providing a braking action using an electro-rheological fluid, the system comprising:
a body having a first, upper portion and a second, lower portion made from an electrically non-conductive material;
a first plurality of positive polarity electrodes having a variable first gap distance between adjacent negative polarity electrodes;
a second plurality of negative polarity electrodes having a variable second gap distance between adjacent positive polarity electrodes;
the upper portion of the body structured and arranged to accommodate the first plurality, which are rotatable, and the lower portion of the body structured and arranged to accommodate the second plurality, which are stationary,
the first plurality being disposed within the gap between adjacent negative polarity electrodes, and
the second plurality being disposed within the gap between adjacent positive polarity electrodes; and
a safe high voltage connection that is electrically coupled to a voltage source and to the plurality of first plurality of positive polarity electrodes.
26. The system as recited in claim 25, wherein each of the first plurality of positive polarity electrodes are substantially hollow cylinders that are coaxial and concentric to one another.
27. The system as recited in claim 25, wherein each of the second plurality of negative polarity electrodes are substantially hollow cylinders that are coaxial and concentric to one another.
28. The system as recited in claim 25, wherein each of the first and second pluralities of electrodes has a height, and the height of the first plurality differs from the height of the second plurality.
29. The system as recited in claim 25 further comprising an electrically-conductive, elongate body that is mechanically coupled to the first plurality of positive polarity electrodes.
30. The system as recited in claim 25 further comprising a controller for selectively controlling a voltage delivered to the first plurality of positive polarity electrodes, to activate the electro-rheological fluid between adjacent positive and negative polarity electrodes to cause the system to brake.
31. A system for providing a controllable velocity or resistive force during exercises of a mammalian extremity, the system comprising:
variable resistance hand rehabilitation device including:
a support structure for providing strength and structure to the device;
a handle portion by which the extremity performs the exercises through translating in a single degree of freedom;
a controllable damping system that is structured and arranged to provide a selectively controlled resistance to the extremity using an electro-rheological fluid having a resistivity that is continuously variable throughout a stroke cycle;
at least one sensing device, each of which is mechanically coupled to the handle portion and each of which is adapted to provide measurement data for controlling the resistivity of the electro-rheological fluid; and
a controller for controlling the controllable damping system and for receiving measurement data from the at last one sensing device, the controller structured and arranged to vary current flow to an electrode that is electrically coupled to the damping system, said current being adapted to tune the resistivity of the electro-rheological fluid, to provide a desired isokinetic or isotonic response.
Description
CROSS REFERENCE TO RELATED APPLICATIONS

The present utility patent application claims the benefit of priority to U.S. Provisional Patent Application No. 61/130,484 dated May 30, 2008 entitled “Variable Resistance Hand Rehabilitation Device With Linear Smart Fluid Damper And Dynometer Capabilities”.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

(Not applicable)

BACKGROUND OF THE INVENTION

A device for hand rehabilitation is disclosed, and, more particularly, a one degree-of-freedom hand rehabilitation device that provides controllable resistance during hand-gripping and hand-releasing exercises and that is compatible with magnetic resonance imaging (MRI) is disclosed.

Of the many impairments that result from stroke, perhaps the most disabling is hemiparesis of the upper limb because the impact on disability, independence, and quality of life is so marked. Stroke survivors typically receive intensive, hands-on physical and occupational therapy to encourage motor recovery. However, due to economic pressures on the U.S. health care industry, individuals, post stroke, are receiving less therapy and are being discharged from rehabilitation hospitals before rehabilitation is complete.

Robotic/force feedback training is a considerably new technology that has shown great potential for application in the field of neuro-rehabilitation as it has several advantages, e.g., motivation, adaptability, data collection, and the ability to provide intensive individualized repetitive practice. Studies on robotic/force feedback devices for post stroke upper extremity rehabilitation have shown significant increases in upper limb function, dexterity, and fine motor manipulations as well as improved proximal motor control.

Furthermore, functional Magnetic Resonance Imaging (fMRI), which maps brain hemodynamic changes, is being more widely used to study human brain mechanisms controlling voluntary movement and reorganization of the sensorimotor brain system in response to neurological injuries such as stroke. fMRI-compatible devices are required to study the brain mechanisms of motor performance in controllable dynamic environments; to enable clinicians to quantify and monitor the effect of motor retraining in stroke patients; and to improve the practice of neuro-rehabilitation.

Due to the nature of fMRI modality, which uses high energy magnetic fields, fast-switching magnetic field gradients and radio-frequency pulses, as well as being very sensitive to external noise, the development and use of MR-compatible devices are very challenging tasks. Despite these challenges, MR-compatible, force feedback interfaces have been introduced in the past few years. Embodiments of these interfaces have included: a manipulandum with actuators, force and/or motion sensing systems, and tactile stimulators, all of which enable neurologists to investigate motor performance and the mechanisms of neural recovery following neurological injuries such as stroke.

A force feedback rehabilitation device that can be used in fMRI studies to allow neurologists or other practitioners to evaluate patients for changes in brain activity associated with motor retraining is desirable. Moreover, a compact, force feedback rehabilitation device that facilitates retraining of hand grasp/release motor skills in patients recovering from neurological ailments, e.g., stroke, is also desired.

SUMMARY OF THE INVENTION

A variable resistance hand rehabilitation device and corresponding system are disclosed. Improvements over the prior art include: a new damping system or damper design, to reduce friction and increase maximum force output; a dynometer feature that enables converting the dynamic device to a static grip force measuring device; a closed-loop controller; and a new graphic user interface for the medical practitioner and new virtual reality game software that allow accurate and smooth operation of the device and increased patient motivation.

A controllable damper is the main component of the device. The controllable damper is an ERF-based, continuously variable, computer-controlled damping system that provides smooth resistance throughout a grip/release stroke cycle. Closed-loop control enables operational resistance to be isotonic (constant force), isokinetic (constant velocity), or to follow a predefined force profile.

The damper employs plural coaxial, concentric, hollow, cylindrical electrodes that are separated by gaps through which the ERF can be forced. In the absence of an electric field, the damper provides virtually zero resistance. However, when voltage is applied to at least one of the electrodes, an electric field is generated through the ERF, which results in a change in yield stress, producing a selectively tunable degree of resistivity.

The pressure on the piston generated by the ERF valve as well as the frictional force of a seal combine to form the baseline force that must be overcome in order for a patient/user to move the damper's output shaft.

To accommodate changes in volume within the damping chamber, a volume compensation chamber filled with closed-cell foam is provided. The volume compensation chamber (VCC) is filled with a closed-cell foam that compresses, e.g., elastically, as the output shaft connected to the damping piston translates back into the damping chamber during the return stroke. Use of closed-cell foam is advantageous over traditional volume compensation methods due to its simplicity, low cost, low spring rate, and durability. The VCC is further structured and arranged to facilitate evacuating and eliminating gases from the damping system, to prevent air bubbles and/or cavitation. A Buna-/Neoprene-based closed-cell foam is suitable for use due to its compatibility with oils, low spring rate, and good compression recovery.

To provide positional feedback to the software controller, a linear potentiometer is mounted to the moving handle portion. The linear potentiometer measures displacement of the moving handle portion. For force measurement, a load cell is mounted to the moving handle portion, to measure force as it is applied by the patient/user.

The device includes a return force control subsystem to control the level of return force once the patient/user has completed a stroke cycle. Use of a standard setup protocol that normalizes the return force to a known reference point, allows an adjustable, repeatable return force, which enables a practitioner to setup and repeat experiments/tests under the same or virtually the same conditions.

Optionally, the device also may include a dynometer-like locking mechanism. The locking mechanism is adapted to lock the output shaft in a desired position. Use of the dynometer changes the functionality of the device from a dynamic force- or velocity-controlled device to a static device that measures grip strength with the handles in any position.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is pointed out with particularity in the appended claims. However, the advantages of the invention described above, together with further advantages, may be better understood by referring to the following description taken in conjunction with the accompanying drawings. The drawings are not necessarily drawn to scale, and like reference numerals refer to the same parts throughout the different views.

FIG. 1 shows an illustration of a variable resistance hand rehabilitation device system in accordance with the present invention;

FIG. 2 shows an elevation view of a patient-actuated variable resistance hand rehabilitation device (VRHD) in accordance with the present invention;

FIG. 3 shows an isometric view of a first side of a patient-actuated variable resistance hand rehabilitation device (VRHD) in accordance with the present invention;

FIG. 4 shows an isometric view of a second side of a patient-actuated variable resistance hand rehabilitation device (VRHD) in accordance with the present invention;

FIG. 5 shows an illustration of a first joining means for a handle portion in accordance with the present invention;

FIG. 6 shows an illustration of a spherical joint for a handle portion in accordance with the present invention;

FIG. 7 shows an isometric view of a dynometer locking mechanism in accordance with the present invention;

FIG. 8 shows an exploded view of the dynometer locking mechanism shown in FIG. 7;

FIG. 9 shows a cross-section view of a damping system, volume compensation system, and return force control system in accordance with the present invention;

FIG. 10 shows a cross-section view of a damping system and volume compensation system in accordance with the present invention;

FIG. 11 shows an isometric view of the plural electrodes in accordance with the present invention;

FIG. 12 shows a detail of the air trap and slide valve on the case end cap in accordance with the present invention;

FIG. 13 shows the interior (A) and exterior (B) surfaces of the case end cap in accordance with the present invention;

FIG. 14 shows the interior (A) and exterior (B) surfaces of the case manifold in accordance with the present invention;

FIG. 15 shows a block diagram of an exemplary control algorithm for a PI controller;

FIG. 16 shows a representative force versus time graph of a grip-and-release stroke cycle;

FIG. 17 shows an embodiment of a miniature damping device using electro-rheological fluid;

FIG. 18 shows an illustrative embodiment of a diaphragm seal-based damping system in accordance with the present invention;

FIG. 19 shows a cut-away view of the diaphragm seal-based damping system of FIG. 18;

FIG. 20 shows isometric (A) and front elevation views (B) of an electro-rheological valve used in the damping system of FIG. 18;

FIG. 21 shows a diagram of a diaphragm seal and piston for use with the damping system of FIG. 18;

FIG. 22 shows a first plurality of rotatable electrodes and a second plurality of stationary electrodes; and

FIG. 23 shows cross-sectional views of a portable, rotary-type electro-rheological fluid-based brake that includes the electrodes of FIG. 22.

DETAILED DESCRIPTION OF THE INVENTION

A Variable Resistance Hand Rehabilitation Device (VRHD) and a system using the VRHD are disclosed. The VRHD is a patient-actuated device adapted for isotonic, isokinetic, and/or variable resistance grasp and release exercises for mammalian extremities, e.g., the human hand. Its principal functionality is derived from an electro-rheological fluid-based controllable damping system (or damper) that allows continuously variable modulation of dynamic resistance throughout its stroke. Indeed, a desirable feature of the device is the use of electro-rheological fluids (ERF) to achieve tunable, computer controlled, resistive force generation. For this purpose, a change in yield stress observed in an ERF in response to an electric field can be exploited to produce virtually zero resistance when idle and selectively-tunable resistivity when an electric field is applied to the ERF.

The VRHD is an improvement of a controllable damper that is the subject of U.S. patent application Ser. No. 11/886,342 commonly owned by Northeastern University of Boston, Mass. and included herein in its entirety by reference. The VRHD of the current invention, however, provides a resistive force for grasp and release hand exercises that is controllable, repeatable, and quantifiable.

Referring to FIG. 1, a hand rehabilitation system 10 is shown. The system 10 includes a patient-actuated device, i.e., a VRHD 2; control electronics 4, e.g., control hardware and corresponding control software, for controlling delivery of a desired force or velocity to the patient/user; a high-voltage power supply 6; and a software interface 8, e.g., a graphical user interface (GUI) and virtual reality (VR) game software, for displaying acquired patient data during manipulation or operation of the VRDH 2.

The power supply 6 provides power to the patient-actuated device 2 via a first voltage bus 1 and to the low-level control electronics 4 via a second voltage bus 9.

The control electronics 4 are in electrical communication with the patient-actuated device 2, to receive measurement data signals from at least one sensing device and to provide control signals thereto; as well as with the software interface 8, which can be disposed local to or remote from the patient-actuated device 2 and/or the control electronics 4.

The patient-actuated device 2 includes, inter alia, a sensing system and communication means 7 for transmitting measurement (data) signals to the control electronics 4, e.g., via radio frequency (RF) signals and/or via hardwire communication. The control electronics 4 include means for reformatting, processing, and filtering the data signals and means for transmitting the processed data 7 to a local or remote processor 5, e.g., a personal computer or microprocessor, that is electrically connected through the software interface 8, e.g., via RF signals of via hardwire communication.

The hardware of and/or software executable on the processor 5 is/are adapted to store in memory and/or to display the data from the control electronics 4 on a display device 3, e.g., a computer screen or monitor, that is electrically coupled to the processor 5. The data display 3 can take any shape or form desired by the practitioner or the patient/user.

Patient-Actuated Device

The patient-actuated, variable resistance hand rehabilitation device (VRHD) includes significant improvements over a system described in U.S. patent application Ser. No. 11/886,342, chief of which includes replacement of a rotary brake design details with a linear system. Linear handle motion, e.g., using a linear, electro-rheological fluid-based (ERF-based) damper, provides significant advantages to the rotary brake design. For example, a linear ERF-based damper is capable of generating larger resistive forces compared to a similarly sized rotary ERF damper. Moreover, increased resistive force output eliminates the need for gears. Elimination of gears reduces mechanical friction associated with the device, which translates into a much smaller zero voltage resistance. Furthermore, design is simpler, stronger, and includes fewer parts.

Linear translation of a moving handle portion (as opposed to rotary handle motion) greatly simplifies direct force measurement using a linear force sensing device, e.g., a load cell, that is disposed proximate the moving handle portion. In contrast, with a rotary brake, output rotary torque is extrapolated dimensionally using force measurements from two compression sensing devices and a known moment arm. Direct force measurement reduces systematic errors, which increases repeatability, simplifies related software algorithms, and reduces the quantity of sensors needed by one.

Referring to FIGS. 2-4, an embodiment of a patient-actuated VRHD 2 is shown. The VRHD 2 includes a support structure 16, a handle portion 20, a sensing system 50, a handle return force control system 17, a (dynometer) locking system 15, a controllable damping system 30, and a volume compensation system 40. The design of the present invention focuses on optimizing the linear system described in U.S. patent application Ser. No. 11/886,342.

To use the device, a patient/user would grasp the handle portion 20, which is at an at-rest, open position, and squeeze, exerting a rearward force or pressure on the moving handle portion 21. The damping system 30 modulates the resistance of the moving handle portion 21 to a preset level throughout the stroke cycle. After the stroke is complete, the damping system 30 deactivates and the handle return force control system 17 returns the handle back to the at-rest, open position.

The support structure 16 is configured and arranged to provide integrity to and support each of the other portions or sub-systems that make up the VRHD 2 so as to enhance the proper functioning and operation of each of the other portions or sub-systems as described in greater detail below. Those of ordinary skill in the art can appreciate that there exists a myriad of different structural support schemes, hence, the precise form of the support structure 16 is less important than the function it performs.

The support structure 16 for the embodied VRHD 2 disclosed herein includes a pair of horizontal support portions 16 a that are rigidly connected by a pair of support brackets 16 b and 16 c. The pair of horizontal support portions 16 a are elongate members such as rods and, more particularly, cylindrical rods. Each bracket of the pair of support brackets 16 b and 16 c is attached orthogonally or substantially orthogonally to the horizontal support portions 16 a and are positioned and arranged to maintain each of the support portions 16 a parallel or substantially parallel to one another in a horizontal or substantially horizontal plane.

According to the illustrative embodiment described herein, a first support bracket 16 b is disposed proximate to the locking mechanism 15. A second support bracket 16 c is disposed so as to be releasably attached to the damping system 30. More detailed description of the support structure 16 is provided below in the description of the operation of the VRHD 2.

The handle portion 20 of the VRHD 2 includes a first, moving handle portion 21 and a second, stationary handle portion 22, which, preferably, include ergonomic designs to conform to a human hand, to provide maximum user comfort. The moving handle portion 21 includes a first opening 23 and a second opening 24 that are each sized to accommodate low-friction, linear, plain bushings 29 and the elongate portions 16 a the support structure. The bushings 29, e.g., a low-friction, linear, plain bushing manufactured by Igus Limited of Northampton, England, enable the moving handle portion 21 to translate linearly with respect to and along the corresponding elongate portions 16 a with minimal frictional resistance between the bushings 29 and the peripheral surfaces of the openings 23 and 24 and/or with the corresponding elongate portions 16 a of the support structure.

As shown in FIG. 5, optionally, a handle position adjusting device 26, e.g., a nut/bolt combination, can be provided in the handle portion 20 for adjusting the relative positions of the handle portion 21 and the stationary handle portion 22.

The moving handle portion 21 is mechanically coupled to a sensing system 50, which can include, for example, a strain gauge-based load cell 12 and a linear potentiometer 11. The stain gauge-based load cell 12, e.g., a 150-lb. load cell manufactured by Interface Force Measurements Limited of Berkshire, England, is adapted to measure force applied to the moving handle portion 21 by the patient/user directly. The linear potentiometer 11, e.g., a custom linear potentiometer manufactured by Active Sensors, Inc. of Indianapolis, Ind., is structured and arranged to measure the absolute position of the moving handle portion 21.

Data from the sensing system 50 are transmitted to the controller 4 in real-time. The controller 4 uses the data for closed-loop control of the VRHD 2 and, furthermore, processes these data and transmits the processed data in a suitable format for displaying real-time performance information at the software interface 8 and/or for storing the data, so that said data can be viewed and analyzed at a later time by a researcher.

The strain gauge-based load cell 12 is attached to or mechanically mounted on the moving handle portion 21 and is releasably attached to an output shaft 39 of a piston (not shown) associated with the damping system 30 or an extension thereto and/or to a handle adjusting device 26. Wires (not shown) and/or a radio frequency (RF) device (not shown) are provided to electrically couple the strain gauge-based load cell 12 to the controller 4 so that measurement data from the load cell 12 can be transmitted to the controller 4 in real-time.

The linear potentiometer 11 can also be mechanically attached to the moving handle portion 21 and to one of the fixed brackets 16 b of the support structure. As shown in FIG. 3, a proximal end of the linear potentiometer 11 can be inserted in a notched area 14 provided for that purpose in the bracket portion 16 b of the support structure and a distal end of the linear potentiometer 11 can be fixedly or releasably attached to the moving handle portion 21, e.g., using machine screws, machine bolts, rivets, and the like 27. Wires (not shown) or an RF device (not shown) are provided to electrically couple the linear potentiometer 11 to the controller 4 so that measurement data from the potentiometer 11 can be transmitted to the controller 4 in real-time. To minimize electro-magnetic interference (EMI) when used in connection with MRI, all wires should be shielded.

As shown in FIG. 5 and FIG. 6, the strain gauge-based load cell 12 and/or the handle position adjusting device 26 can be releasably attached to the moving handle portion 21 using a nut and bolt combination 27 (FIG. 5) or using a spherical joint 49 (FIG. 6).

As shown in FIGS. 2-4, the handle portion 20 can include a removable stroke length scale 28 and handle motion stops 25. The stroke length scale 28 can be removably attached, e.g., clipped on, to an elongate portion 16 a of the support structure, to provide a visual measure of stroke lengths. The adjustable handle motion stops 25 can be used to delineate the limits of the stroke of the moving handle portion 21, which allows the patient/user or medical practitioner to adjust the start point and end point of each stroke cycle, to accommodate varying patient/user needs.

Each of the pair of adjustable handle motion stops 25 comprises adjustable shaft collars that are disposed on and releasably attachable to one of the elongate portions 16 a of the support structure, upstream and downstream of the direction of travel of the moving handle portion 21. The locations of these shaft collars can be set with some precision using the removable stroke length scale 28. Although the adjustable handle motion stops 25 are shown on the upper elongate portion 16 a, those skilled in the art can appreciate that adjustable handle motion stops 25 could also be disposed on the lower elongate portion 16 a.

The handle return force control system 17 controls speed of the moving handle portion 21 back to the start point of the stroke length after the patient/user has released or reduced the force on the moving handle portion 21 by modulating the elastic force with sliders 18 and a notched scale 34. The handle return force control system 17 is implemented as an elastic-based return system.

As shown in FIGS. 2-4, the handle return force control system 17 includes a pair of tubes 31, a pair of slidable elastic mounts 18, and a pair of notched scales 34. Each of the pair of tubes 31, e.g., surgical silicone tubes, is releasably attached, e.g., using ferrules 13, at a distal end to a bracket 32 mounted proximate to the strain gauge-based load cell 12 so that when the patient/user applies force to the moving handle portion 21, the bracket 32 applies force to the ferrules 13 and to the tubes 31, elastically displacing the tubes 31.

The other, proximal ends of the tubes 31 are each releasably attached to a corresponding, selectively positionable slidable elastic mount 18. Each of the sliding elastic mounts 18 is structured and arranged to control the preload of each tube 31. More specifically, each slidable elastic mount 18 controls the preload of each tube 31 using the mount's selectively fixed location, e.g., at a discrete positioning notch, on a corresponding notched scale 34.

Each of the notched scales 34 includes an inner opening into which one of the elongate portions 16 a of the support structure can be inserted, much like a grip on a bicycle handle bar. Each slidable mount 18 is structured and arranged to mate with a positioning notch on a corresponding notched scale 34. The functioning and interoperability of the handle return force control system 17 will be described in greater detail below.

The (dynometer) locking system 15 is a locking mechanism that is structured and arranged to lock the output shaft 39 into a pre-designated position, to change the functionality of the VRHD 2 from a dynamic measuring device to a static measuring device. The purpose of the locking system 15 is to prohibit movement of the output shaft 39 in a linear or a rotational direction. As a result, during static use, any force applied by the patient/user to the moving handle portion 21 produces data at the strain gauge-based load cell 12 that can be used to determine a patient's/user's maximum and sustained manual squeezing.

An illustrative embodiment of a locking system 15 is shown in FIG. 7 and FIG. 8 in an assembled and in an exploded view, respectively. Under normal, dynamic measuring conditions, the locking mechanism 15 does not impact the operation of the output shaft 39 with respect to the handle portion 20. However, when static measurements are desired, the locking mechanism 15 can be activated so that force applied to the moving handle portion 21 is not transmitted to output shaft 39 and/or the damping piston 35.

When static measurement functionality is desired, the locking mechanism 15 is engaged by applying a radial force (torque) to a lever 19 that can be inserted in and/or that protrudes from the outer periphery of the locking mechanism 15. The lever 19 acts as a moment arm to engage the locking mechanism. The locking mechanism includes a portion that is fixed to the structure support, a second portion that is screwed to the support structure with a course thread, and a plastic wedge that is forced against the output shaft when the second portion is tightened.

The locking force is directly related to the amount of torque applied to the lever 19 of the locking mechanism 15. Reversing the direction of this force will release the locking mechanism 15 so that the output shaft 39 will move freely. Because the locking system 15 is located between the load cell 12 and the damping piston (not shown), the force applied to the first handle portion 21 by the patient/user can also be read into the software. This functionality mimics that of a standard Hand Dynometer.

A controllable damping system 30 is shown in FIGS. 9-12. The controllable and tunable damping system 30 includes an air- and water-tight protective outer case and internal damping component. The working (damping) components of the controllable damping system 30 include a plurality of concentric and coaxial electrodes 33, 37, and 38, a piston 35, and an output shaft 39. Briefly, during operation, voltage is delivered to a middle electrode 37 to generate an electric field in the ERF between the middle electrode 37 and each of the central bore 33 and outer electrodes 38. The electric field affects the yield stress of the ERF, causing the ERF to thicken as it is activated. As the EFR thickens, it becomes more resistive to flow, increasing the overall resistivity of the damper 30 and making it more difficult for the piston 35 to force the ERF through the gaps 43.

The plurality of electrodes 33, 37, and 38 are hollow cylinders that, preferably, are manufactured from a thermally- and electrically-conductive material, such as aluminum. Although the drawings show three concentric and coaxial electrodes, this is done for illustrative purposes only. Theoretically, one or more electrodes could be used.

The plurality of electrodes includes a central bore electrode 33, which has a negative (n) (or ground) polarity, a middle electrode 37, which has a positive (p) polarity, and an outer electrode 38, which also has a negative (n) (or ground) polarity. Fluid gaps 43, whose purposes is described in greater detail below, are provided between the middle electrode 37 and each of the central bore 33 and outer electrodes 38. The gap 43 is between approximately 0.5 mm and 1.5 mm, depending on the application.

Each of the plurality of electrodes 33, 37, and 38 can have the same height. Alternatively, to provide additional means for adjusting the maximum and minimum force capabilities of the damper 30, the height of the middle electrode 37 can be adjusted, i.e., shortened with respect to the central bore 33 and outer electrodes 38. Shortening the middle electrode 37 will confine or limit the extent of the magnetic field generated by the electrodes only to the shortened length of the middle electrode 37. This will cause the resistivity to decrease. Consequently, the minimum, i.e., baseline, resistive force of the VRHD 2 and the maximum force of the VRHD 2 will decrease.

If the height of the middle electrode 37 is shortened, a spacer, e.g., a plastic spacer, can be added to fill the additional space between the electrode 37 and the case end cap 44. Accordingly and advantageously, by modifying the length of the middle electrode 36, the resistivity provided by the damper 30 can be fine tuned for any desired application.

Electrical connection to each of the electrodes 33, 37, and 38 is made via electrically-conductive socket head cap screws or bolts, which are removably attached to each of the electrodes. As shown in FIG. 11, each of the plurality of electrodes 33, 37, and 38 includes a tapped electrical connection screw hole 58 c into which the socket head cap screw or bolt can be inserted. FIG. 13 shows corresponding electrical connection holes 58 a and 58 b that are provided in the end cover cap 44 that are structured and arranged to be in registration with the tapped electrical connection screw holes 58 c on each of the plurality of electrodes 33, 37, and 38. The pair of screw holes 58 a in the end cover cap 44 are electrically coupled to the negative (n) (ground) pole and the single screw hole 58 b is electrically coupled to the positive (p) pole.

Referring to FIG. 10, an electrically-conductive metal, e.g., aluminum, screw or bolt (not shown) is disposed through and into each of the screw holes 58 a or 58 b and 58 c. An electrically-conductive wire (not shown) is coupled to a protruding end or head of the metal screws or bolts, e.g., using an eyelet. The electrically-conductive wire is further attached to a rod 57 that is mounted within an electrically-conductive metal, e.g., aluminum, adapter 61.

An electrical (female-type) connection or wire 62, e.g., a high-voltage panel connector such as those manufactured by Teledyne-Reynolds of Berkshire, England or ODU-USA of Camarilla, Calif., is electrically coupled to the metal adapter 61. The connector 62 is adapted to use the non-electrically conductive damping case as ground and to use a central pin 63 as a positive cathode. A mating (male-type) connector (not shown) is electrically coupled between the end portion of a coaxial wire extension from the female-type connection 62 and the high voltage power supply 6 (FIG. 1). The electrical connections preferably deliver low-amperage current to minimize any impact on the MRI machinery and electronics.

The concentric and coaxial electrodes 33, 37, and 38 are confined within a protective damper case that includes a center case 45, a removable case end cover or cap 44, and a case manifold 42. Mounting the electrodes within a damper case having a removable case end cover 44 allows easy access to the electrical connections without having to drain the ERF from the damping system 30.

The protective damper case can be made out of any electrically-insulative, i.e., non-conductive, material and is precision machined to maintain system concentricity. Preferably, each of the component parts of the protective damper case is manufactured of an insulative polymer such as polyoxymethylene (POM), e.g., DelrinŽ manufactured by DuPont.

As shown in FIG. 10 and FIG. 12, the outer periphery of the outer electrode 38 is in a tight interference fit with the inner peripheral surface of the center case 45. The protective damper case is completed by the case end cap 44 and the case manifold 42, which are releasably secured to the end portions of the center case 45, e.g., using machine or industrial screws or bolts and the like. Although the drawings show that the interior and exterior peripheral surfaces of the case center 45 and the outer peripheral surface of the outer electrode 38 are cylindrical, this is shown for illustrative purposes only. The peripheral surfaces could, alternatively, be polygonal.

Referring to FIG. 13 and FIG. 14, interior faces (A) and exterior faces (B) of an embodiment of a case end cap 44 and of a manifold 42, respectively, are shown. The interior faces (A) correspond to the portions of the case end cap 44 and of the case manifold 42 that interface with the center case 45 to form the a sealable damping system 30. The exterior faces (B) correspond to the portions of the case end cap 44 and of the case manifold 42 that are exterior to the damping system 30.

The case end cap 44 and the case manifold 42 each include a plurality of mounting holes 47 that are arranged to be in registration with corresponding pluralities of mounting openings 47 disposed on both end portions of the wall of the center case 45. The mounting holes/openings 47 are adapted to receive a fastening device (not shown), e.g., a machine screw or bolt, a socket-type screw of bolt, and the like, for releasably securing the center case 45 to each of the case end cap 44 and the case manifold 42, to provide an air- and water-tight damping chamber 36 therebetween.

The interior faces (A) of each of the case end cap 44 and of the case manifold 42 include a gland 51, a plurality of electrode alignment tabs 46, and a pin hole alignment portion 48 b. The gland 51 is adapted for retaining an annular sealing device (not shown), e.g., an O-ring. Moreover, the gland 51 is dimensioned to be in registration with the wall section of the center case 45 so that the wall section forms an air- and water-tight seal when pressed against the annular sealing device.

Each of the plurality of electrode alignment tabs 46 includes a first tab 46 a and a second tab 46 b. The first tab 46 a is precision machined to provide and to maintain the gap 43 between the outer electrode 38 and the middle electrode 37. The second tab 46 b is precision machined to provide and to maintain the gap 43 between the central bore electrode 33 and the middle electrode 37. The electrode alignment tabs 46 a and 46 b keep the electrodes aligned precisely, so that the dimensions of the gaps 43 between them are constant and, more particularly, so that the central bore electrode 33 remains concentric and coaxial with respect to piston 35, to minimize friction therebetween.

The alignment pin holes 48 b are also provided to properly align the electrodes within the protective damper case. More particularly, during assembly, alignment pin holes 48 a disposed on the end portions of each of the electrodes 33, 37, and 38 are placed in registration with the alignment pin holes 48 b. Alignment pins or screws (not shown) are inserted through the alignment pin holes 48 b in the case end cover 44 and in the electrode alignment pin holes 48 a, to fix the electrodes 33, 37, and 38 in place.

The interior face (A) of the case end cap 44 (FIG. 13) also includes plural air traps 54 and a volume compensation chamber 53, which will be described in greater detail below. Each of the air traps 54 is fluidly connected via a fluid conduit 65 to a corresponding slide valve 64. The slide valves 64 are provided to facilitate draining any air/gas that collects in the air traps 54 prior to and during the filling operation and/or during operation of the damper 30. As is well-known, air/gas has a significantly lower dielectric strength then ERF. Accordingly, any gas bubbles whose dimensions equal the gap 43 distance could induce arcing between adjacent electrodes. These features also allow the damping system 30 to be slightly pressurized to prevent cavitation and allow the damper 30 to operate in any orientation.

The interior face (A) of the case manifold 42 (FIG. 14) includes an opening 52 that is structured and arranged to accommodate the output shaft 39. The exterior face (B) of the case manifold 42 includes a gland 59 or groove. The gland 59 is concentric and coaxial with the opening 52 and with the output shaft 39. The gland 59 is adapted to retain an annular sealing device.

Preferably a Teflon-based, spring-loaded sealing device 56 is disposed within the seal gland 59 (FIG. 10), about the output piston 39. The spring-loaded sealing device 56 prevents fluid leakage and is custom designed for each application depending on whether low friction or, alternatively, durability is desirable. The sealing device 56 can be made up of three parts (not shown).

First, a stationary, flanged-nut having an external male thread can be mounted onto a base-plate. This first part is machined with a female tapered bore through which the shaft 39 traverses freely. Second, a TeflonŽ annular ring having a split-male taper with a slip that is dimensioned to that of the shaft 39, is mated with the taper of the stationary flanged-nut. Finally, the locking nut having an internal thread, is mated with the stationary-flanged nut. The locking nut also includes a through bore through which the shaft 39 traverses freely.

The locking nut contains, aligns, and compresses the Teflon taper, to create resistance along the peripheral surface of the shaft 39. The split-male taper is subsequently secured to a locking nut for release purposes. The magnitude of the torque applied to the shaft 39 determines the resistance to axial and radial movement

The piston 35 is machined to provide a radial clearance between approximately 0.002 in. and approximately 0.005 in. between the outer diameter of the piston 35 and the inner diameter of the central bore electrode 33. This close clearance eliminates friction associated with normal piston seals and reduces pressure leakage to a negligible amount. The inner peripheral surface of the central bore electrode 33 as well as the outer peripheral surface of the piston 35 also can be hard coated, e.g., with a low-friction, anodized material, to reduce friction if the piston 35 were to rub against the inner peripheral surface of the central bore electrode 33. Optionally, an annular sealing device (not shown) could be included in the outer periphery of the piston 35 to provide a tight seal between a first chamber 36 a and a second chamber 36 b.

A volume compensation system 40 is adapted to the damping system 30, and, more particularly, to the case end cap 44, for filling and draining the damper 30 but, more pertinently, to accommodate any change in volume inside the damping system 30 that results from temperature fluctuations and/or from the operation of the output shaft 39 and piston 35. The volume compensation system 40 includes a volume compensation chamber (VCC) 53, which is filled with an elastic, closed-cell foam, a screw cap 67, and a sealing device 68, e.g., an O-ring.

Preferably, the VCC 53 is filled with an elastic, closed-cell foam (not shown) such as Buna or neoprene, which is naturally adapted to accommodate a change in volume associated with movement of the output shaft 39 in and/or out of the damper chamber 36. Buna- and/or neoprene-based closed-cell foam is preferred for use due to its compatibility with oils, its low spring rate, and its good compression recovery.

The foam can be formed or tailored into any desired shape, e.g., cylindrical, polyhedral, and so forth, so that it tightly fits into the VCC 53. Small ledges or ridges (not shown) can be added to the inner peripheral surface of the VCC 53, to provide some frictional resistance, to restrict or restrain the foam from moving. Optionally, the foam can extend out from the limits of the VCC 53 into the upstream portion 36 b of the damper chamber 36. By extending the closed-cell foam, the amount of compressible volume of the foam would increase, however, the stroke length of the damper 30 would be reduced.

After closed-cell foam is inserted into the VCC 53, any air entrained in the closed-cell foam and/or in the damper chamber 36 should be evacuated before the damper chamber 36 is filled with an additional volume of ERF used to pressurize the damping system 30. Pressurization prevents degassing of the ERF and, furthermore, allows the damping system 30 to be operated in any orientation.

Closed-loop Controller

A typical grasp and release exercise consists of either an isokinetic (constant speed) or an isotonic (constant force) motion. Although a closed-loop controller 4 for the invention as claimed will be described in terms of an isotonic (constant force) exercise, this is done for the purpose of conciseness rather than limitation.

A major challenge in implementing a force-control algorithm in an ERF-based control device such as the VRHD 2, is that the VRHD 2 can only resist and, as a result, does not produce any “active” force. However, the VRHD 2 must, on occasion, also act as a brake in order to input a disturbance in the human motor loop so as, in the end, to finally exhibit a constant force. In short, the human being or other mammal must be capable of applying the force to the moving handling portion 21.

For example, suppose that during an isotonic exercise, it is desired that the force applied by the patient must, at all times, remain less than or equal to a pre-established force value, Fd. Initially, the applied force is zero, the velocity is zero, and device 2 remains at-rest. By design, as force is applied, as long as the applied force remains less than Fd, the VRHD 2 continues to remain at-rest. However, Newtonian physics and the laws of force, impulse, and momentum provide that as force is applied and as the VRHD 2 begins to translate, the force necessary to be applied by the patient/user to keep the VRHD 2 in motion decreases.

Problematically, with an isotonic system in which force remains constant, were the controller 4 to react too quickly to counteract any decrease in applied force, e.g., by countering the decrease in applied force by increasing the resistive force that the patient/user experiences, displacement of the VRHD 2 may stop altogether. Accordingly, it is desirable to take into account the Stribeck effect, which is well-known to those of ordinary skill in the art.

Referring to the block diagram of an exemplary, PI controller for isotonic exercises shown in FIG. 15, the force, Fd, corresponds to the desired force that is pre-set by the practitioner. The “measured force” and “measured velocity” are, respectively, the force and velocity measured and/or determined using data accumulated by the sensing devices. Zeros are respected, meaning that if all the inputs are zero (in natural units) then the output voltage 74 that is actually applied to the VRHD 2 equals zero Volts (0 V).

The feed-forward term 78, the proportional (P) force gain (Kp) 71, and the integral (I) force gain (Ki) 76, can be computed as non-linear functions of the position (or displacement), the velocity, and the desired force. Integral control with anti-windup has been investigated for the force loop.

The proportional force gain term (Kf) 71 changes the output such that it remains proportional to the force error value, i.e., the difference between the measured force and the desired force, Fd, at the force-error summation node 60. In other words, the proportional response is adjusted merely by multiplying the force error value 60 by the force gain constant 71, Kf.

The integral term 75, which is subsequently added (at summation node) 66 to the proportional term 69, accelerates the movement of the process towards a set-point and eliminates the residual steady-state error that occurs with a proportional only controller.

The magnitude of the contribution of the integral term 75 to the overall control action is determined by the integral gain 76, Ki. Integral anti-windup ensures that the integral 75 maintains a proper value, avoiding output voltage saturation.

The feed-forward term 78, Vmodel, was calculated experientially from open-loop testing using the equation:


V model=0.027*F d+0.29

The Vmodel term 78 generates the output voltage to the ERF linearly as a function of the input desired force, Fd. A damping factor 81 could also be used to control the system, to take into account the velocity dependence of the force generated by the system.

The control saturation term 74 corresponds to the high and low limit of the output voltage sent to the ERF.

To improve the performance of the PI Controller, gain scheduling was used, whereby individual gains were calculated for different intervals of force. After the stroke cycle is complete the damper 30 deactivates and the mechanical handle return force control system 17 brings the first handle portion 21 back to its at-rest, open position.

Several experiments using open-loop control of a VRHD, in which no control action was applied, were performed. The output force applied by the hand device, however, exhibited great variability, indicating a greater need for a closed-loop controller. During initial experimentation with the VRHD 2 using closed-loop force control, at the beginning of the stroke cycle, a small overshoot in the force manifests due to the transient from static to dynamic. To reduce this small overshoot, at the beginning of the stroke, the command voltage sent to the ERF can be ramped as a function of the stroke. Afterwards, the command voltage becomes the sum of the output from the PI controller and the desired voltage feed-forward term 78. Consequently, a VRHD 2 under closed-loop force control with the correction voltage in the beginning of the stroke eliminates the overshoot.

Three different control hardware configurations have been used to implement the control algorithm: a Field-Programmable Gate Array (FPGA) System; a Data Acquisition (DAQ) System, and a Real-Time (RT) System.

Operation of the VRHD and the VRHD System

Having described the structural elements of the present system 10, the operation and interoperability of this structure and of the VRHD 2 and the VRHD system 10 will now be described. Before the system 10 can be operated, however, it is important to properly prepare, i.e., fill, bleed, and pressurize, the damping system 30 with an electro-rheological fluid (ERF).

Filling the damper 30 is accomplished by first removing the screw cap 67 of the volume compensation system 40 and removing the closed-form foam contained therein. The exposed damper chamber 36 can then be filled with an appropriate ERF. After the level of the ERF reaches the bottom of the volume compensation chamber (VCC) 53, the closed-form foam is replaced in the VCC 53 and the screw cap 67 is replaced on the volume compensation system 40.

Due to the deleterious effect of air bubbles within the ERF, the damping system 30 should be bled. As previously described, air bubbles can result in arcing between electrodes or have other deleterious effects on operation of the damping system 30.

To bleed off any bubbles that may cause arcing, the piston 35 can be cycled several times within the damper chamber 36 while the slide valve(s) 64 that is fluidly coupled to one of the air traps 54 is open to the atmosphere and physically located at the highest elevation with respect to the damper chamber 36 as possible.

During a downward (compression) stroke, the piston 35 moves farthest away from air traps 54 and the least amount of the shaft 39 is contained in the damper chamber 36. Any air trapped in the damper chamber 36 or in the ERF will bleed out of the slide valve 64.

When all the air/gas has been bled out and nothing but ERF exits from the slide valve 64 during a compression stroke, a syringe containing additional ERF can be placed in or on the slide valve 64 and a small amount of ERF can be added back into the damping system 30, to slightly pressurize the system. The damping system 30 is then ready for operation.

With the damping system 30 ready to operate, as a patient/user grips the moving handle portion 21 and applies a force to the moving handle portion 21, the stain gauge-based load cell 12 senses the load (force) and the load potentiometer 11 is adapted to measure the displacement caused by the force.

Force on the moving handle portion 21 is transmitted down the output shaft 39 to the piston 35 in the damping chamber 36, causing the piston 35 to translate in the same direction as the exerted force. Referring to FIG. 10, as the piston 35 translates (in the direction of the arrow), the pressurized ERF is forced from a high-pressure zone 36 a in the damping chamber 36 though a plenum portion 79 in the case manifold 42 and, subsequently, into the plurality of concentric gaps 43 between adjacent electrodes 33, 37, and 38.

As the ERF travels through the gaps 43 between the electrodes 33, 37, and 38, the controller 4 signals the power source 6 to deliver a controlled, voltage to the middle electrode 37. The controlled voltage generates an electric field within the ERF, causing the yield stress of the ERF to increase, producing, thereby, greater resistance to further compression. Low-amperage current is desirable, especially when used in conjunction with MRI equipment and electronics.

The actions of the piston 35 and the transmission of the ERF through the gaps 43 produce a pressure drop, which acts on the piston 35 in a direction opposite to that of the direction of pull by the patient/user. As a result, resistivity to piston 35 motion is transmitted as feedback to the patient/user, which manifests as a resistance to translation. After the ERF passes along the entire heights of the electrodes and through the entire lengths of the gaps 43, it enters a plenum portion 55 of the case end cover 44, subsequently collecting in a low-pressure zone 36 b behind (upstream of) the piston 35. During the return stroke, after the patient/user has released his/her grip on the moving handle portion 21, the fluid path and high- and low-pressure zones are reversed.

As previously mentioned, the closed-cell, foam-based volume compensation system 40 is structured and arranged to compensate for the changes in volume due to changes in temperature and, more particularly, due to translation of the output shaft 39 and the accompanying change of volume. During the piston's return stroke (opposite direction as arrow on shaft), the closed-cell foam in the volume compensation chamber 53 compresses, to adjust or account for the added volume of the additional length and volume of shaft 39 within the damping chamber 36. Hence, as the piston 35 continues to move to the right (as pictured) and more of the shaft 39 enters the damping chamber 36, the volume compensation chamber 53 compensates for the volume increase by compressing. When the piston 35 operates in a compression mode, the closed-cell foam operates in the opposite manner.

Current solutions utilized in other devices include: secondary piston chambers with spring loaded piston, gas filled secondary chambers, diaphragms, bellows, and the like. In contrast, the present system's 40 foam-based implantation is simple, inexpensive, compact, and highly effective. The closed-cell foam is also easily removed to allow for quick filling and draining of the damping chamber 36.

Referring to FIG. 16, performance of a grasp and release test using the VRHD is represented by a graph of force versus time.

Miniature ERF Damping System

Referring to FIG. 17, a miniature ERF damping system using the aforementioned damping technology will be described. The damping system 90 was designed for a specific application, i.e., a damping force of 1.14 N with a compressed length of 1.5 in., and an extended length of 2.0 in. (hence, a stroke of 0.5 in.), and a cross-section of 0.5 in. by 0.5 in.

The mini-damper 90 includes a damping case 110, a single hollow, cylindrical electrode 92, and a damping piston 91 that is mechanically coupled to an output shaft 94. The damping case 110 includes, for example, a central case portion 95, a choke assembly 106, a case end cover 107, and a case manifold 105. A sealing device 108, e.g., a gasket, is provided at the interface between the central case portion 95 and the a choke assembly 106, between the choke assembly 106 and the case end cover 107, and between the central case portion 95 and the case manifold 105.

The central case portion 95 is manufactured from an electrically non-conductive material and can have a shape that is cylindrical, polygonal, rounded polygonal, and so forth. Preferably, the inner peripheral surface of the central case portion 95 is cylindrical, but non-cylindrical surfaces are possible. Particularly, the inner diameter of the inner peripheral surface is slightly larger than the outer diameter of the electrode 92. More specifically, the inner diameter of the inner diameter of the (cylindrical) central case portion 95 is larger than the outer diameter of the electrode 92 a distance that is equal to twice the desired gap 99 distance. As previously disclosed, the gap 99 distance is variable between approximately 0.5 mm to 1.5 mm.

The choke assembly 106 is also manufactured from an electrically non-conductive material and has a shape that is consistent with that of the central case portion 95. The choke assembly 106 is structured and arranged to provide a tight interference fit at a proximal end of the central case portion 95. A projection 114 and a ledge portion 115 are structured and arranged to abut against so as to align the outer peripheral surface of the electrode 92 properly. The projection 114 is machined and dimensioned to provide and to maintain the desired gap 99 distance between the inner peripheral surface of the central case portion 95 and the outer diameter of the electrode 92.

The choke assembly 106 includes a central portion 109 having a through hole, i.e., a choke 96. When assembled and ready for operation, the central portion 109 separates the volume compensation chamber (VCC) 93 from the choke assembly plenum 116. The choke 96 provides a fluid connection between the VCC 93 and the choke assembly plenum 116. The VCC 93 will be described in greater detail below. During operation of the device 90, the plenum 116 is fluidly coupled to the downstream portion 117 of the damping chamber 103 and contains a predetermined volume of ERF. The choke 96 provides a conduit for transmission of the ERF during a stroke cycle.

The choke assembly 106 also includes an electrical connection 112 that is structured and arranged to accommodate a electrically-conductive metal, e.g., aluminum, spring 100 and to provide an opening 113 through which an electrical contact (not shown) can be electrically coupled to a proximal end of the metal spring 100. The distal end of the metal spring 100 is electrically coupled to an electrical terminal (not shown) that is disposed on an end portion of the electrode 92.

The case end cover 107 is also manufactured from an electrically non-conductive material and has a shape that is consistent with that of the choke assembly 106, to which the case end cover 107 is mechanically coupled, e.g., using a plurality of machine screws, bolts, and the like. The case end cover 107 includes an electrical connection opening 104 and the VCC 93, in which a closed-cell foam can be disposed. A distal end 102 of the case end cover 107 includes a hole 99 for releasably attaching the case end cover 107 to another object.

The electrical connection opening 104 in the case end cover 107 is disposed to be in registration with the opening 113 in the choke assembly 106, for electrically coupling an electrical contact (not shown) to the proximal end of the metal spring 100.

The case manifold 105 is also manufactured from an electrically non-conductive material and has a shape that is consistent with that of the central case portion 95, to which the case end cover 107 is mechanically coupled. The case manifold 105 includes an opening 111 that is structured and arranged to accommodate frictionless translation of the output shaft 94. A gland 119 is also provided in the case manifold to accommodate a sealing device 98.

Optionally, the case manifold 105 further includes a plug portion 118 that is adapted to accommodate a plug 97 having a through hole 120 that is structured and arranged to accommodate frictionless translation of the output shaft 94.

The piston 91 and output shaft 94 are disposed coaxial to and within and the damping chamber 103 of the electrode 92. The piston 91 is precision manufactured to provide clearance between the outer periphery of the piston 91 and the inner peripheral surface of the electrode 92 as previously described. The output shaft 94 is successively disposed through the opening 111 in the case manifold 105, the sealing device 98, and the through hole 120 in the plug 97. A distal end 101 of the output shaft 94 includes a hole 99 for releasably attaching the output shaft 94 to another object.

Operation of the miniature ERF damping device 90 is essentially the same as previously described. However, there is only a single electrode 92 and a single gap 99. The electrode 92 is a positive (p) pole and is electrically coupled to a voltage source (not shown) via the metal spring 100 and an external electrical connection (not shown). The central case portion 95 is made of an electrically non-conductive material, e.g., DelrinŽ, and therefore serves as a ground. Accordingly, when increased resistivity is desired, the source voltage is delivered to the electrode 92, which generates an electrical field within the ERF, causing an increase in yield stress and a corresponding increase in resistivity.

Diaphragm Seal-Based VRHD

A diaphragm seal-based VRHD based on rolling seal technology will now be described. The preferential use of rolling seals reduces friction because the rolling seals, e.g., rolling seals manufactured by Dia-Com Corporation of Amherst, N.H., have no break-free friction, but rather exhibit a constant rolling resistance throughout a stroke cycle.

Referring to FIGS. 18-20, the embodied VRHD 150 includes a handle portion 20, a damping system 155, and at least one sensing device, e.g., a load cell 12.

The moving handle portion 21 of the handle portion 20 is mechanically coupled to the first ends of a pair of elongate members 151. The second, opposite ends of the elongate members 151 are mechanically coupled to a bracket 153 to which the load cell 12 sensing device is releasably attached.

The load cell 12 is mechanically coupled to the output shaft 158 of the damping system 155, which is mechanically coupled to a first damping piston 152. The first damping piston 152 is structured and arranged to translate along the longitudinal axis of a first, damping chamber 157. More specifically, the first damping piston 152 and rolling diaphragm seal 156 are adapted, during a gripping load, to force an ERF through the gaps 165 of an ERF valve 160 into a second chamber 159. During a release period, a second, spring-biased piston 156 is adapted to force the ERF back through the gaps 165 in the ERF valve 160 into the first, damping chamber 157. The ease with which the damping piston 152 forces the ERF through the ERF valve 160 is selectively variable, by applying a voltage to a plurality of positive polarity members 162 within the ERF valve 160, while maintaining negative polarity members 164 adjacent to the positive polarity members 162 at ground.

As previously described, voltage applied to the positive polarity members 162 generates an electric field within the ERF that is disposed within the gaps 165 between adjacent positive and negative polarity members 162, 164. The yield stress of the activated ERF increases, making it more difficult to force the ERF through the ERF valve 162. Because the magnitude of the voltage and the duration of its application to the positive polarity members 162 are controllable, the resistivity of the VRHD 90 is tunable.

A rolling diaphragm seal 156 is disposed at a distal end of the first piston 152. As shown in FIG. 21, the diaphragm seal 156 isolates the piston 156 from the ERF fluid that fills the first chamber 157. The peripheral edge 160 of the diaphragm seal 156 is releasably attached to or between the inner wall of the first chamber 157. When the first piston 152 is in a no-load, at-rest, retracted position, the excess diaphragm material is preserved as a diaphragm loop 164 that is disposed in the gap 162 between the first piston 152 and the inner diameter of the first damping chamber 160.

As the first, damping piston 152 is forced towards the distal end of the first chamber 157, the loop 164 decreases in size until it is displaced to the point of its greatest reach. When fully extended to the point of its greatest reach, the diaphragm seal 156 should not be stretched excessively beyond its elastic yield stress.

A second, spring-biased piston 154 is disposed in a second chamber 159, opposite the first piston 152. ERF forced through the ERF valve 160 by the action of the damping piston 152 and diaphragm 156 compresses the spring portion of the spring-biased piston 154, causing it to displace commensurate with the volume of ERF that is forced from the first chamber 157 to the second chamber 159. Once the patient/user releases his or her grip, the spring-biased piston 154 forces the ERF from the second chamber 159 back through the ERF valve 160, and back into the first, damping chamber 157. The ERF entering the damping chamber 157 exerts a force against the diaphragm 156 and the damping piston 152, returning each to their no-load, at-rest position.

During operation, as described above, as a patient/user applies a force to a moving handle portion 21, the load is transferred to the output shaft 158, causing the damping piston 152 and diaphragm seal 156 to force ERF through the ERF valve 160 into the second chamber 159. The ease with which the ERF passed from the first damping chamber 157 into the second chamber 159 can be controlled selectively by applying a voltage to positive polarity members in the ERF valve 160

As the ERF fluid passes into the second chamber 159, the force of the ERF exceeds the spring constant of the spring member (not shown) that biases the second piston 154, causing the second piston to displace, e.g., elastically, within the second chamber 159. When the patient/user ceases gripping the handle portion 21, the spring constant of the spring member biases the second piston 154 towards the ERF valve 160, forcing the ERF fluid back into the first, damping chamber 157 and further forcing the first, damping piston 152 and the diaphragm 156 back to their no-load, at-rest positions.

Portable, Rotary ERF Damping System

Referring to FIG. 22 and FIG. 23, embodiments of a portable, rotary ERF brake 130 using plural electrodes 125 and the ERF-based damping technology described herein, respectively, are shown. For this particular application, a rotary-type device 130 is preferred to a linear device because it can be made more compact and because of the open-loop performance advantage that rotary ERF devices inherently have over linear ERF devices. Indeed, rotary ERF devices operate more smoothly and lend themselves to a more user friendly demonstration because they can be handheld and do not require additional frame support or associated linear motion guides.

The brake body 121, which includes a first, upper portion 121 a and a second, lower portion 121 b, of the device 120 are, preferably, fabricated from an electrically non-conductive material, e.g., DelrinŽ. The upper portion 121 a of the brake body 121 is structured and arranged to accommodate a first plurality of rotatable electrodes 125 a and the lower portion 121 b of the brake body is structured and arranged to accommodate a second plurality of stationary electrodes 125 b.

Each electrode of the plurality electrodes 125 is manufactured as a hollow or substantially hollow cylinder out of an electrically conductive metal, such as aluminum. Each of the first plurality of rotatable electrodes 125 a and is structured and arranged to be mutually concentric and coaxial and each of the second plurality of stationary electrodes 125 b is structured and arranged to be mutually concentric and coaxial. The first plurality of rotatable electrodes 125 a includes a center hub 138 that is connected to each of the plurality of stationary electrodes 125 a via a circular or substantially circular bottom plate 126. The second plurality of stationary electrodes 125 b does not have a hub, however, each of the plurality of electrodes 125 b is connected to every other of the plurality of stationary electrodes 125 b via an annular circular bottom plate (not shown).

Preferably, the second plurality of electrodes 125 b is stationary and has a positive (p) polarity and the first plurality of electrodes 125 a is rotatable and has a negative (n) polarity, or ground. The gap distance 129 between each of the first plurality of electrodes 125 a and the gap distance 129 between the second plurality of electrodes 125 b are both equal to twice the desired gap distance between adjacent electrodes of opposite polarity. Those of ordinary skill in the art can appreciate, however, that the gap distances can be selectively chosen, which is to say, they can differ. The heights, or engagement lengths, of the electrodes, whether positive polarity or negative polarity also can be varied to provide additional tuning.

A safe high voltage (SHV) connector(s) 123 and a power cable, e.g., an RG58 coaxial cable (not shown), are provided in the lower portion 121 b of the body, to electrically couple the rotatable electrodes 125 a to the power source (not shown) and/or to a control box (not shown). To make the device 130 portable a custom battery-powered control box can be used.

To deliver power from the SHV connector(s) 123, which is disposed in the lower portion 121 b of the body, to the rotatable electrodes 125 a, which are disposed in the upper portion 121 a of the body, a rotatable, threaded, elongate body, e.g., a rod 122, is electrically coupled to the first plurality of electrodes 125 a and to the SHV connector(s) 123. The rod 122 is structured and arranged to operate frictionlessly within the central opening 138 of the hub 127.

An electrically non-conductive metal, e.g., brass, plain bearing(s) 124 is used for supporting and centering the rotating rod 122. The bearing(s) 124 and a conductive grease provides a stable, low-noise electrical pathway. An output shaft 135, e.g., a stainless steel shaft, is provided and mechanically coupled to a hand crank 133 at a first end and to the rotating rod 122 at a second end.

When assembled, the body is air- and water-tight so as to provide a suitable reservoir 137 for the ERF. When the reservoir 137 is filled, the ERF invades the gaps 129 between the electrodes 125 a and 125 b. Slide valves 128 are provided in the lower portion 121 b of the body and fluidly coupled to the reservoir 137, for draining, bleeding, and filling the reservoir 137 of the rotary device 120.

Operation and control of the portable, rotary ERF brake 130 is similar to that previously described above. A controller (not shown) for the device 130 slows, retards, or arrests rotation of the shaft 135 and the rod 124 as a function of the magnitude of the applied low-amperage current and the duration of the application of the current to the positive polarity electrodes 125 b. More specifically, when current is delivered to the stationary electrodes 125 b, an electrical filed is generated between adjacent electrodes 125 a and 125 b, which affects the yield stress of the ERF, making further rotation of the rotatable electrode 125 a more difficult.

Many changes in the details, materials, and arrangement of parts and steps, herein described and illustrated, can be made by those skilled in the art in light of teachings contained hereinabove. Accordingly, it will be understood that the following claims are not to be limited to the embodiments disclosed herein and can include practices other than those specifically described, and are to be interpreted as broadly as allowed under the law.

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US8025607Sep 16, 2010Sep 27, 2011Northeastern UniversityInstrumented handle and pedal systems for use in rehabilitation, exercise and training equipment
WO2013142872A1 *Mar 25, 2013Sep 26, 2013Northeastern UniversityApparatus with rolling contact handle
Classifications
U.S. Classification482/135
International ClassificationA63B21/00
Cooperative ClassificationA61H1/0285
European ClassificationA61H1/02M5
Legal Events
DateCodeEventDescription
Nov 3, 2009ASAssignment
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:WEINBERG, BRIAN;KHANICHEH, AZADEH;MAVROIDIS, CONSTANTINOS;SIGNING DATES FROM 20090529 TO 20090601;REEL/FRAME:023460/0519
Owner name: NORTHEASTERN UNIVERSITY,MASSACHUSETTS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:WEINBERG, BRIAN;KHANICHEH, AZADEH;MAVROIDIS, CONSTANTINOS;SIGNED BETWEEN 20090529 AND 20090601;US-ASSIGNMENT DATABASE UPDATED:20100218;REEL/FRAME:23460/519
Owner name: NORTHEASTERN UNIVERSITY,MASSACHUSETTS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:WEINBERG, BRIAN;KHANICHEH, AZADEH;MAVROIDIS, CONSTANTINOS;SIGNING DATES FROM 20090529 TO 20090601;REEL/FRAME:023460/0519