Stiction-Tolerant Brake Force Estimation in Aircraft Drivetrains
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Solution Overview
Problem
Aircraft braking systems face challenges in accurately estimating brake force due to stiction in the geared drivetrain, which can lead to momentary miscalculations and compromised feedback control, especially when direct force measurement is not desired due to component reliability concerns.
Innovation Solution
A method and system for stiction tolerant brake force estimation that involves calculating uncompensated and stiction compensated brake force estimates using motor states such as angular velocity, temperature, and supply voltage, with a rate of change limiter and integrator to adjust the brake force rate and compensate for stiction, ensuring accurate force application.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If stiction compensation is implemented using motor states and rate limiting, then brake force estimation accuracy is improved, but device complexity increases
Solution Approach 1:
The patent introduces intermediate calculations including uncompensated brake force estimates, stiction force estimates, and rate of change limits as mediators between the motor state measurements and the final compensated brake force estimate. These intermediaries break down the complex compensation task into manageable stages, improving accuracy without requiring a complete system redesign
Solution Approach 2:
The brake force estimation process is segmented into distinct computational stages: measuring motor states, calculating uncompensated force estimates, determining stiction compensation, applying rate limits, and integrating results. This segmentation allows each stage to be optimized independently and facilitates implementation within existing control architectures
2Measurement precision
If direct force measurement is used, then brake force accuracy is improved, but reliability deteriorates due to component concerns
Solution Approach 1:
The patent replaces direct mechanical force measurement with an indirect estimation approach using electrical motor state measurements (current, voltage, speed). This substitution eliminates the need for additional force sensors in the mechanical drivetrain, maintaining measurement accuracy through calculation while improving reliability by avoiding fragile force sensing components in harsh braking environments
Solution Approach 2:
The patent uses motor electrical parameters as intermediaries to infer brake force without direct mechanical measurement. By measuring motor current, voltage, and speed - which are more reliable in harsh environments - and calculating the resulting brake force through established relationships, the system achieves accurate force estimation without exposing force sensors to the harsh mechanical braking environment
3Measurement precision
If stiction compensation is applied, then brake force accuracy is improved, but response time deteriorates due to additional calculations
Solution Approach 1:
The patent performs preliminary calculations of uncompensated brake force estimates and stiction force models using pre-established relationships and lookup tables. By preparing these intermediate values in advance and organizing them for efficient processing, the system minimizes the computational burden during critical braking events while maintaining high accuracy
Solution Approach 2:
The patent transforms the complex stiction compensation problem into a series of simpler parameter adjustments. By changing the representation of brake force from a single direct measurement to a composite of multiple parameters (uncompensated force, stiction force, rate limits), the system achieves higher accuracy through calculations that can be executed efficiently using standard control computer operations
4Stability of the object's composition
If rate of change limiting is applied, then stability is improved, but productivity deteriorates due to constrained force adjustment
Solution Approach 1:
The patent implements dynamic rate limiting where the maximum allowed force change rate is not fixed but adapts based on current braking conditions, motor state, and flight phase. This dynamic adjustment allows the system to maintain stability during normal operation while permitting faster force application when conditions permit, effectively resolving the contradiction between stability and responsiveness
Solution Approach 2:
The patent calculates and stores rate of change limits in advance based on pre-determined safety margins and operational envelopes. By preparing these limits beforehand and organizing them for rapid access during braking events, the system can apply force adjustments at the maximum safe rate without real-time computational delays, maintaining both stability and productivity
Data Source
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AI summary
The present disclosure provides systems and methods for stiction tolerant brake force estimation. In various embodiments, a method for stiction tolerant brake force estimation may comprise receiving, by a controller, a first motor state at a first time (Step 502), calculating, by the controller, a first uncompensated brake force estimate based upon the first motor state (Step 504), calculating, by the controller, a first linear speed based upon the first motor state (Step 506), and calculating, by the controller, a first stiction compensated brake force estimate based upon at least one of the first linear speed and the first uncompensated brake force estimate (Step 508).