Electromechanical Brake Actuator Force Control Without Load Cell Feedback
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Solution Overview
Problem
Existing aircraft braking systems face challenges in maintaining accurate force control, particularly when load cell sensors fail, leading to unpredictable and inefficient braking performance.
Innovation Solution
The proposed brake system utilizes an electromechanical brake actuator with a ball screw mechanism, coupled with a set of stiffness curves representing force versus ball screw position for different worn states of the rotating discs. This system allows for precise force control by determining the appropriate ball screw position based on the worn state and stiffness curves, even in the absence of a functional load cell sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If load cell sensors are used for brake force measurement and feedback, then accurate force control is achieved, but system reliability deteriorates when the load cell sensor fails
Solution Approach 1:
The patent introduces an intermediary computational model (stiffness curve) that mediates between the actuator position and the actual brake force. This stiffness curve acts as a mathematical intermediary that maps ball screw positions to expected forces based on wear state, allowing the system to estimate force accurately even when the load cell sensor fails, thus maintaining reliability while preserving measurement precision through the model-based estimation
2Device complexity
If traditional brake systems operate without wear compensation, then device complexity is reduced, but manufacturing precision deteriorates due to unpredictable braking performance
Solution Approach 1:
The patent applies preliminary action by pre-characterizing the brake system's stiffness properties across different wear states during the manufacturing or initial operation phase. The stiffness curves for various wear states (new, partially worn, fully worn) are determined in advance and stored in the control system. This preliminary characterization allows the controller to compensate for wear effects without adding complex real-time sensing infrastructure, maintaining relatively simple device complexity while achieving high manufacturing precision through the pre-established wear compensation models
3Ease of operation
If the ball screw position is determined without wear state information, then ease of operation is improved, but measurement precision deteriorates leading to inaccurate force control
Solution Approach 1:
The patent applies parameter changes by utilizing the wear state as an additional parameter that modifies the relationship between ball screw position and applied force. Instead of using a single static position-force relationship, the system dynamically adjusts the interpretation of ball screw position based on the current wear state parameter. This allows the same physical position to correspond to different force levels depending on wear, enabling accurate force control while maintaining ease of operation through position-based control commands
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 enables accurate and predictable force application during braking, ensuring reliable performance even when load cell sensors fail, by using the stiffness curves to determine the necessary ball screw position and maintain effective braking control.
Implementation Method 1
a ball screw positioned between the electromechanical brake actuator and the pressure plate
Implementation Method 2
The electromechanical brake actuator is configured to extend the ball screw to a ball screw position to apply a requested force to the pressure plate towards the end plate thereby forcing the plurality of rotating discs together in an axial direction
Implementation Method 3
forcing the plurality of rotating discs together in an axial direction in order to reduce a rotational speed of the plurality of rotating discs
Data Source
AI summary
A brake system is disclosed herein. The brake system includes an electromechanical brake actuator, a pressure plate, an end plate, a ball screw positioned between the electromechanical brake actuator and the pressure plate, and a plurality of rotating discs positioned between the pressure plate and the end plate. The electromechanical brake actuator is configured to extend the ball screw to a ball screw position to apply a requested force to the pressure plate towards the end plate thereby forcing the plurality of rotating discs together in an axial direction in order to reduce a rotational speed of the plurality of rotating discs. The ball screw is extended by the electromechanical brake actuator to the ball screw position based on a worn state of the plurality of rotating discs and a stiffness curve for the electromechanical brake actuator that represents force versus ball screw position for the worn state.