Electric Power Steering Controller Torque Compensation
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Solution Overview
Problem
Conventional electric power steering systems experience instability and vibrations when switching between periodic updating and holding of detected steering torque values, leading to an uncomfortable driving experience.
Innovation Solution
The system incorporates a controller that alternates between two control modes, adjusting compensation values and using a torque differential compensation unit, filter unit, and damping compensation unit to stabilize the control system, while also employing a steering return compensation unit to improve steering performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the controller alternately executes periodic updating and holding of the detected steering torque value, then the control system can operate in backup mode when the torque sensor is malfunctioning, but the control system becomes unstable and vibrations are generated in the steering mechanism
Solution Approach 1:
The patent changes the compensation value parameter when switching between first control (periodic updating) and second control (holding) modes. Specifically, when the second control is executed, the compensation value is adjusted to a value smaller than when the first control is executed. This parameter change compensates for the instability introduced by alternating between updating and holding operations, suppressing vibrations in the steering mechanism while maintaining backup control capability.
2Stability of the object's composition
If the compensation value is increased to suppress vibrations during mode switching, then control system stability improves, but the steering return performance is reduced
Solution Approach 1:
The patent dynamically adjusts the compensation value based on the control mode being executed. Rather than using a fixed compensation value, the system switches between different compensation value settings: a larger compensation value when first control (periodic updating) is executed to enhance steering return performance, and a smaller compensation value when second control (holding) is executed to suppress vibrations. This dynamic adjustment resolves the contradiction between stability and steering return performance.
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 approach reduces vibrations and enhances steering stability and comfort by adjusting compensation values and filter characteristics during mode switches, ensuring stable control even during backup operations.
Implementation Method 1
a magnetic circuit that applies magnetic flux corresponding to steering torque applied by a driver to the Hall IC
Implementation Method 2
a Hall IC and a magnetic circuit that applies magnetic flux corresponding to steering torque applied by a driver to the Hall IC
Implementation Method 3
a magnetic field generator that periodically applies a magnetic field to the torque sensor
Data Source
AI summary
There is provided an electric power steering system that makes it possible to reduce an uncomfortable feeling given to a driver even when a detected steering torque value is held. The controller (5) computes a detected steering torque value (τ) based on the detection signal (Sτ), and provides compensation based on a compensation value to a basic current command value based on the detected steering torque value (τ) to compute a current command value (I*). The controller (5) executes feedback control for causing a current value of the motor (30) to follow the current command value (I*). The controller (5) executes normal control in which the detected steering torque value (τ) is periodically updated and backup control in which periodic updating of the detected steering torque value (τ) and holding of the detected steering torque value (τ) are alternately executed. The controller (5) switches compensation value between a compensation value used during execution of the normal control and a compensation value used during execution of the backup control.