Active Damping Algorithm for EPS Motor Velocity Control
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Solution Overview
Problem
Electric Power Steering (EPS) systems face challenges in managing high rack loads, which lead to increased motor velocities and reduced available motor torque, causing undesirable high motor velocities due to the physics of electric motors, and existing solutions like modifying mechanical design or using larger motors are costly or degrade steering feel.
Innovation Solution
An active damping algorithm that generates a damping command based on motor velocity, t-bar torque, and vehicle speed signals to reduce motor velocity, utilizing a damping activation module, command calculation module, and damping calculation module to mitigate rack disturbances effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the motor capacity is increased to provide more reaction torque, then the available motor torque is improved, but the system cost increases significantly
Solution Approach 1:
The patent applies active damping control that dynamically adjusts the damping coefficient based on operating conditions (motor velocity, rack position, road surface detection). This parameter change approach allows the existing motor to operate more efficiently across different conditions, providing sufficient reaction torque without requiring a larger motor capacity, thus avoiding increased system cost
2Speed
If the EPS mechanical design is modified to reduce high motor velocities, then the motor velocity is reduced, but the steering feel is degraded
Solution Approach 1:
The patent implements a dynamic damping coefficient that changes based on motor velocity, rack position, and detected road surface conditions. At high velocities during off-road braking, increased damping reduces motor velocity. During normal driving conditions, the damping returns to standard levels, preserving steering feel. This dynamic adjustment resolves the contradiction between velocity control and steering quality
Solution Approach 2:
The active damping system automatically detects high rack load conditions through motor velocity monitoring and road surface detection, and self-adjusts the damping coefficient without requiring mechanical modifications. The system serves itself by using its own operational data to control its behavior, reducing velocity only when necessary while maintaining normal steering characteristics
3Speed
If active damping with high damping magnitudes is applied to prevent high motor velocities, then the motor velocity is reduced, but the steering performance is degraded under normal driving conditions
Solution Approach 1:
The patent applies damping intermittently based on detected conditions. The damping activation module monitors motor velocity, rack position, and road surface detection signals, activating high damping only during specific high-risk conditions (off-road braking with high rack load). During normal driving, standard damping levels are maintained, preserving steering performance. This periodic/conditional application resolves the contradiction between velocity control and steering quality
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
The active damping algorithm effectively reduces motor velocity and mitigates rack disturbances, preventing the cycle of increasing motor velocities and torque reduction, thereby improving steering performance without degrading steering feel or increasing costs.
Implementation Method 1
a damping calculation module that generates a damping command based on the damping activation signal and the calculated command, the damping command reducing a motor velocity of a motor of the power steering system to mitigate a rack disturbance
Data Source
AI summary
A system for actively damping a power steering system includes a damping activation module that generates a damping activation signal based on a motor velocity signal, a t-bar torque signal, and a final motor command; a command calculation module that generates a calculated command based on the motor velocity signal and a vehicle speed signal; and a damping calculation module that generates a damping command based on the damping activation signal and the calculated command, the damping command reduces a motor velocity of a motor of the power steering system to mitigate a rack disturbance.