Electromechanical Brake Actuator Position Control at the Zero-Touch Point
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Solution Overview
Problem
Existing aircraft electromechanical brake systems face challenges in achieving predictable force control, especially at lower commanded forces, due to noise susceptibility in load cell signals from long wire lengths.
Innovation Solution
The proposed brake system incorporates an electromechanical brake actuator with a ball screw that can retract to a zero-touch point, determined using position sensors or load cell auto-zeroing, to improve force control and positioning accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If load cell signals are used for brake force measurement and feedback, then force control accuracy is improved, but noise susceptibility increases due to long wire lengths
Solution Approach 1:
The patent replaces the mechanical load cell signal transmission system with an optical encoder system. Instead of using load cells with long wire lengths that are susceptible to noise, the invention uses an optical encoder to directly measure the position of the brake actuator, thereby inferring force application without relying on noisy electrical signals from load cells.
Solution Approach 2:
The patent introduces an optical encoder as an intermediary measurement device. Rather than directly measuring force through load cells, the system uses the optical encoder to measure actuator position, which serves as an intermediate parameter to determine force application, thereby eliminating the noisy load cell signal path.
2Reliability
If the ball screw is retracted to the zero-touch point, then force control predictability is improved, but positioning precision requirements increase
Solution Approach 1:
The patent employs feedback from the optical encoder to continuously monitor the ball screw position and provide real-time data to the control system. This feedback mechanism enables the system to accurately determine when the zero-touch point is reached and maintain precise positioning, thereby achieving both predictable force control and high positioning precision through closed-loop control.
Solution Approach 2:
The patent implements preliminary positioning actions to bring the ball screw to the zero-touch point before force application begins. The optical encoder enables precise pre-positioning, ensuring that the actuator is exactly at the zero-touch point before braking force is applied, which improves force control predictability while managing positioning precision requirements through staged control.
Data Source
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AI summary
A brake system is disclosed herein. The brake system includes a pressure plate, an end plate, a plurality of rotating discs positioned between the pressure plate and the end plate, an electromechanical brake actuator controller, and an electromechanical brake actuator including a ball screw configured to extend to exert force on the pressure plate, the electromechanical brake actuator operatively coupled to the electromechanical brake actuator controller. Responsive to receiving a command from the electromechanical brake actuator controller, the electromechanical brake actuator is configured to retract the ball screw away from the pressure plate to at least a zero-touch point.