This invention relates to control mechanisms, e.g. radio control transmitters.
The background to the invention will be explained in relation to radio control transmitters used for controlling model aircraft. The reader may appreciate that the invention is applicable to other applications.
Almost all aircraft are provided with trimming devices which are used to offset the control surfaces so that the controls, e.g. stick and rudder bar, are in neutral positions when the aircraft is flying straight and level. The requirement to trim the controls is also present in model aircraft. Radio control model aircraft achieve the trim by an offset to the transmitted signal. The offset is generally set by a slider control. In general, the transmitter has input devices in the form of one or more joysticks. The aircraft is flown straight and level and the sliders are set so that this can be achieved with neutral stick input. Setting the sliders requires a degree of practiced skill, to the extent that when a model pilot is learning, an instructor will generally trim the aircraft before handing control to a pupil. Further, setting the sliders is not possible, or at least is not easy, with the hand that is controlling the associated stick and, especially, in the case of three channel control, e.g. aileron, elevator and rudder, at least on channel is left uncontrolled while the sliders are set for the other(s).
Against this background, in accordance with the invention, there is provided a remote control transmitter, comprising a first input device for providing an input signal to which the transmitter is responsive to provide a control signal to control proportionally an operating parameter of a controlled apparatus, the input device having a neutral state, in which the input signal has a value of zero, corresponding to a desired neutral value of the operating parameter; and a second input device operation of which causes the transmitter to provide an offset to the control signal in the same sense as any input to the first input device, said offset increasing in value until the first input device is in its neutral state when the operating parameter has the neutral value. In the exemplary application, when the aircraft is flying straight and level, the second input device, which may be a push button, is operated. The pilot continues to fly the aircraft straight and level. In doing so the stick input required reduces until the stick is in the neutral position. The increase in the value of the offset preferably takes place at a rate commensurate with the pilot remaining in control throughout.
In one form, the transmitter is responsive to the first input signal having a value less than a predetermined amount different from zero, to hold the value of the offset.
Another form includes means responsive to operation of the second input device to store the contemporaneous value of the input signal and is operative to provide an offset to the value of the control signal which increases in the same sense as the stored value until the effect of the offset differs by less than a predetermined amount from that corresponding to the stored value.
In a most preferred form the transmitter is a radio transmitter, the controlled apparatus is a model aircraft and the parameter is the position of a control surface thereof.
The invention also extends to a mechanism for controlling the orientation of one or more control members the orientation of which determines the attitude or direction of a vehicle, the mechanism having: a first input member which is manually movable in position and biased to a neutral position, the mechanism being arranged to control the orientation of the control member(s) dependent on the position of the input member; a detector for detecting that the position of the input member is not neutral, and a trimmer responsive to operation of a second input member to provide an offset to the control member(s) in a sense determined by the position of the input member, said offset increasing in magnitude until the position of the input member is neutral.
The bias may be provided by, for example, springs so that the neutral position is fixed. In operation the vehicle is controlled so that its direction or attitude is that which it is desired should correspond to the neutral position of the input member, for example in the case of an aircraft: straight and level. Presuming the vehicle to be out of trim, requiring non neutral input from the first input member, when the second input member, which may be a push switch, is operated, a gradually increasing offset is given to the orientation of the control member(s). The offset is in a sense to reduce the input required from the first input member until it reaches its (fixed) neutral position.
In an alternative, the bias may be provided by the control members. That is to say changing their orientation from a neutral one requires force which is reflected at the first input member. In, for example, motorcars, this is called “feel” at the steering wheel. In this case the vehicle is again controlled so that its direction or attitude is that which it is desired should correspond to the neutral position of the input member, for example in the case of an aircraft: straight and level. Presuming the vehicle to be out of trim, requiring non neutral input from the first input member, when the second input member is operated, the first input member remains in the same position as the offset increases, until the position of the first input member becomes the neutral position.