Electric Power Steering Velocity Estimation Using State Observer
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Solution Overview
Problem
Existing electric power steering (EPS) systems face challenges in accurately estimating motor velocity, especially at standstill conditions, due to sensitivity to motor parameter estimation errors and the open-loop nature of typical observer modules, which results in phase lag and low bandwidth signals.
Innovation Solution
The EPS system employs a state observer module that computes a base motor velocity estimate using a plant model and includes a delay compensation module to address phase lag issues, along with a standstill detection module to modify the velocity estimate when the handwheel is in standstill mode, without requiring additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a state observer module is used to estimate motor velocity without direct sensors, then hardware cost is reduced, but measurement precision deteriorates due to sensitivity to parameter estimation errors
Solution Approach 1:
The patent implements a closed-loop state observer that uses feedback from actual system outputs (current, position) to continuously correct and update the estimated velocity. This feedback mechanism compensates for parameter estimation errors and maintains high measurement precision without requiring additional sensors, thus resolving the contradiction between reduced hardware complexity and maintained velocity estimation accuracy.
2Device complexity
If an open-loop observer is used for velocity estimation, then device complexity is reduced, but reliability deteriorates due to phase lag and low bandwidth
Solution Approach 1:
The patent transitions from an open-loop to a closed-loop observer structure that continuously compares estimated outputs with actual measurements and adjusts estimates accordingly. This feedback mechanism eliminates phase lag and low bandwidth issues by dynamically correcting estimation errors, thereby improving reliability without significantly increasing control structure complexity.
3Reliability
If delay compensation is added to correct phase lag, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent merges the delay compensation functionality directly into the state observer module by incorporating prediction terms and acceleration-based compensation within the observer's mathematical model. This integration approach improves phase response accuracy and reliability while avoiding the need for separate delay compensation modules, thus minimizing the increase in overall device complexity.
Data Source
AI summary
Technical solutions are described for facilitating a steering system to determine a motor velocity estimate for a motor of the steering system. For example, the steering system may include a state observer module that computes a base motor velocity estimate of the motor based on a plant model of the steering system. The steering system may further include a delay compensation module that computes a delay compensated velocity estimate based on the base motor velocity estimate and an acceleration of the motor. The steering system may further include a standstill detection module that modifies the delay compensated velocity estimate in response to a handwheel of the steering system being in standstill mode.