Electricity: motive power systems – Positional servo systems – With protective or reliability increasing features
Reexamination Certificate
1998-03-27
2001-06-05
Ro, Bentsu (Department: 2837)
Electricity: motive power systems
Positional servo systems
With protective or reliability increasing features
C318S625000, C318S626000
Reexamination Certificate
active
06242878
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to electronic control apparatus and in particular, but not exclusively, to an electronic throttle box for controlling an engine of an aircraft. The invention does however extend more widely to any electronic control apparatus in which a moveable control member exerts a control function either directly or indirectly.
2. Discussion of Prior Art
In an aircraft, the throttle box is a sophisticated item of equipment, allowing the pilot manually to control the aircraft thrust whilst giving him tactile feedback to indicate various conditions or operating regimes of the engine. In addition the throttle box should be designed so that the control member or “throttle top” is not moved inadvertently by vibration or acceleration experienced by the aircraft in use.
Thus the requirements imposed on a throttle box for it to be suitable for use in a modern fighter aircraft result in extremely complex mechanical designs which are expensive and difficult to produce, requiring as they do the services of skilled and highly trained personnel for their assembly and set up; for example the throttle box for use on a typical modern fighter aircraft might easily require a development outlay of around fifty thousand man hours. This complexity derives primarily from the requirement for tactile feedback implement base friction throughout the travel of the throttle top and mechanical detents to provide demarcation between distinct areas of operation such as dry and re-heat, whilst contending with the rigours of a cockpit environment—notably vibration.
SUMMARY OF THE INVENTION
According to one aspect of this invention there is provided an electronic control apparatus comprising:
a movable control member;
a positional servo loop means including at least one motor means and being operable to maintain the position of said control member at any one of a plurality of positions in the range of movement thereof in accordance with a demand signal;
force detection means for detecting a force applied to said control member and for providing to said servo loop means a demand signal which varies in accordance with at least one of the magnitude and direction of said applied force when it exceeds a preset threshold (which may be zero).
By this arrangement the force applied to the control member is detected and used to cause the positional servo loop means to move the control member in the appropriate direction. At rest, the position of the control member is maintained by the positional servo loop means (unless the applied force or torque exceeds the maximum force or torque available to the servo loop).
Preferably, the apparatus includes base friction threshold means for thresholding said force detection means whereby an applied force below a preset threshold does not cause said loop means to alter the position of the control member, thereby providing a base friction effect over at least part of the range of movement of said movable member. The threshold applied may of course be varied to adjust the base friction level or “stiffness” and this may be set at different levels at different parts of the range of movement of the movable control member.
The apparatus preferably also includes detent friction threshold means for locally thresholding said force detection means at one or more predetermined locations within the range of movement of said movable member, whereby an applied force above said localised threshold is required to alter the position of said movable control member, thereby to provide a detent effect.
The servo loop means may advantageously comprise two motor means operable in a normal mode selectively to move the movable member in respective opposed directions. Preferably said motor means are additionally operable in a fall-back mode to allow a selected one thereof to be actuable to move the movable member in either of said opposed directions.
The apparatus preferably includes electric bias means operable in said normal mode to supply a bias drive signal to each of said motors to bias the drive thereof in opposite directions, thereby to reduce or minimize backlash.
The force detection means may take various forms such as a force transducer but it is particularly preferred to monitor the drive signal to the, or at least one of the, motor means, thereby to determine the force transmitted by said movable member to said motor means.
Particularly where the electronic control apparatus is in an environment subject to high acceleration, it is preferred for said force detection means to include means for distinguishing between an acceleration-induced force and a control force manually or externally applied to said movable member, and for adjusting said demand signal in accordance with said manually or externally applied force. Thus, for example, an accelerometer means may be attached to a static part of the structure to detect the acceleration imparted thereto, thereby to determine the acceleration-induced force experienced by the unit as a whole, which can then be used to compensate the total force signal determined by said force detection means, to obtain a net force signal representing the manually or externally applied force.
The force detection means preferably includes counter means for being incremented or decremented in accordance with the force applied to said control member, the value held on said counter means being used to generate said demand signal.
The force detection means typically comprises pulse generating means such as an oscillator means for incrementing or decrementing said counter means. The pulse frequency of said pulse generating means is preferably variable in accordance with the rate of movement applied to said control member.
The electronic control apparatus is preferably operable either manually or automatically. In the case of automatic operation an auto-control signal may be externally generated in accordance with one or more parameters of the object or system being controlled and which identify a required position for said movable member. In this instance the apparatus preferably also includes automatic control means responsive to a positional signal representative of the position of said movable member and said externally generated auto-control signal to provide a demand signal for said positional servo loop means. Thus, in use, the movable control member is caused to move to or maintain the current position indicated by said auto-control signal.
Although the movable member itself may directly exert control, for example it may be secured to or linked to a valve member, in its preferred applications a position transducer, such as for example a potentiometer or position encoder, detects the position of said movable member and provides an output signal in accordance therewith.
In another aspect of this invention, there is provided an aircraft incorporating an electronic control apparatus as described above.
In yet another aspect, there is provided a method of controlling the relative position of a movable control member which comprises the steps of:
providing a positional servo loop means including at least one motor means to maintain the position of said control member at any one of a plurality of positions in the range of movement thereof;
detecting the force applied to said control member in use thereby to provide a demand signal, and
applying said demand signal as an input to said positional servo loop means.
Whilst the invention has been described above it extends to any inventive combination of the features set out above or in the following description.
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patent: 0 326 439 (1989-08-01), None
patent: 0 483 773
BAE Systems plc
Nixon & Vanderhye P.C.
Ro Bentsu
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