Fly-by-wire Control Stick Backlash Reduction via Three-Gimbal Linkage
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Solution Overview
Problem
Existing control sticks for aircraft, such as joysticks and side-sticks, face issues with mechanical linkages that introduce friction, backlash, and bulkiness, interfering with the smooth transmission of manual input signals and electrical signals in fly-by-wire systems.
Innovation Solution
The design incorporates a three-gimbal mechanism with a resilient column spring to remove backlash, position sensors, and a magnetic detent, along with eddy current dampers, to enable smooth, backlash-free movement and precise force feedback, allowing for improved control stick mechanisms and compound springs with unique force-to-displacement characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mechanical linkages are used to connect control sticks to airfoil surfaces, then the control system is simple and reliable, but the system becomes heavy and bulky, and friction and backlash interfere with smooth signal transmission
Solution Approach 1:
The patent replaces traditional mechanical linkages and cables with electrical transducers and wiring. The control stick position is sensed by transducers that convert mechanical displacement into electrical signals, which are then transmitted to flight control computers. This substitution eliminates heavy mechanical transmission components while maintaining control reliability through redundant electrical pathways.
2Reliability
If mechanical linkages are used to connect control sticks to airfoil surfaces, then the control system is simple and reliable, but the system becomes bulky and requires considerable space
Solution Approach 1:
The patent replaces traditional mechanical linkages and cables with electrical transducers and wiring. The control stick position is sensed by transducers that convert mechanical displacement into electrical signals, which are then transmitted to flight control computers. This substitution eliminates heavy mechanical transmission components while maintaining control reliability through redundant electrical pathways.
3Device complexity
If traditional mechanical linkages are used in control sticks, then the structure is simple, but friction and backlash interfere with smooth transmission of manual input signals
Solution Approach 1:
The patent replaces traditional mechanical linkages and cables with electrical transducers and wiring. The control stick position is sensed by transducers that convert mechanical displacement into electrical signals, which are then transmitted to flight control computers. This substitution eliminates heavy mechanical transmission components while maintaining control reliability through redundant electrical pathways.
Solution Approach 2:
The patent introduces transducers as intermediary devices between the control stick and the flight control system. These transducers convert mechanical stick position into electrical signals, serving as a mediator that eliminates direct mechanical linkage while preserving the control signal. The transducers include position sensors and force sensors that provide precise measurement without mechanical friction or backlash.
4Ease of operation
If passive side-stick units with springs are used to provide force feedback, then the pilot receives tactile sensation, but the springs add complexity to the control mechanism
Solution Approach 1:
The patent introduces transducers as intermediary devices between the control stick and the flight control system. These transducers convert mechanical stick position into electrical signals, serving as a mediator that eliminates direct mechanical linkage while preserving the control signal. The transducers include position sensors and force sensors that provide precise measurement without mechanical friction or backlash.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances the precision and reliability of control stick movements, reducing friction and bulkiness, enabling smoother signal transmission and improved tactile feedback, thus addressing the limitations of previous mechanical linkage systems.
Implementation Method 1
A resilient member (31), such as a column spring, is arranged to bias the direction of relative movement between the intermediate and lower members
Implementation Method 2
eddy current dampers, to enable smooth, backlash-free movement and precise force feedback
Implementation Method 3
a magnetic detent, along with eddy current dampers, to enable smooth, backlash-free movement and precise force feedback
Data Source
Figure 1~2
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Figure 5~6
AI summary
This invention provides an improvement in a control stick (e.g., joystick, side-stick, etc.) (20) adapted to control the movement of an object (e.g., an airfoil surface). The improvement includes: a support (21); an intermediately-pivoted upper member (23) mounted on the support, the upper member having an upper portion (24), and lower portion (25); an intermediate member (26) having an upper portion pivotally connected to the upper member lower portion, and having a lower portion; and a lower member (29) having a lower portion pivotally mounted on the support, and having an upper portion; and wherein the intermediate member lower portion is movably mounted on the lower member upper portion such that pivotal movement of the upper member upper portion relative to the support will produce pivotal movement of the intermediate and lower members relative to the support; and a resilient member (31) arranged to bias the direction of relative movement between the intermediate and lower members. The various pivotal connections may be provided by gimbals such that the various members are mounted for compound pivotal movement about two mutually-perpendicular axes.