Steering Control Apparatus Torsion Bar Phase Compensation
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Solution Overview
Problem
The existing steering systems suffer from deterioration in steering feel due to the twist of torsion bars, leading to delayed motor response and phase discrepancies in steering operations.
Innovation Solution
A steering control apparatus with a command value calculation circuit and compensation circuit that adjusts the phase of motor command values based on torsion bar twist, using products of steering torque and speed, and torsion angle calculations to compensate for delays and improve steering feel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a torque sensor detects steering torque based on torsion bar twist, then steering torque detection is achieved, but the phase of the steered angle is delayed relative to the steering operation
Solution Approach 1:
The system performs preliminary action by calculating a compensation value based on the torsion angle and adding it to the steered angle command value in advance. This pre-compensation ensures that the motor's steered angle responds immediately to the steering operation without delay, counteracting the inherent time lag caused by torsion bar twist before it affects steering performance.
Solution Approach 2:
The system creates a virtual copy of the steering operation signal by calculating a compensation value that replicates the ideal steered angle response. This compensation signal is then combined with the actual steered angle command to produce a corrected command value that mirrors the desired steering behavior without the distortion introduced by torsion bar elasticity.
2Speed
If the phase of the steered angle command value is advanced based on torsion angle compensation, then steering response is improved, but the steering feel is deteriorated due to motor delay
Solution Approach 1:
The system applies dynamic adjustment by varying the compensation value based on the current steering state. The compensation amount is calculated as a product of the torsion angle and a gain value that changes according to steering conditions (such as steering angle, steering speed, or vehicle speed). This dynamic compensation optimizes both steering response speed and steering feel across different operating conditions, preventing motor delay deterioration while maintaining responsiveness.
Solution Approach 2:
The system changes parameters by adjusting the gain value used in compensation calculation based on steering conditions. By modifying this parameter dynamically, the system adapts the phase advancement amount to match current steering requirements, ensuring that compensation improves response without creating unnatural steering feel under varying operational scenarios.
3Loss of time
If a fixed compensation value is applied to the steered angle command, then phase delay is reduced, but steering feel varies under different steering conditions
Solution Approach 1:
The system transitions from static to dynamic compensation by making the compensation value variable rather than fixed. The compensation amount is calculated as a product of the torsion angle and a gain value that adapts to steering conditions such as steering angle magnitude, steering speed, or vehicle speed. This dynamic approach maintains consistent steering feel across different operating conditions while effectively reducing phase delay.
Solution Approach 2:
The system changes the compensation parameter (gain value) based on steering conditions to maintain adaptability. By adjusting this parameter dynamically, the system ensures that the compensation amount is appropriate for each specific steering scenario, preventing steering feel variations that would occur with a fixed compensation value while still reducing phase delay effectively.
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 configuration allows for adjustable motor control delays and enhanced steering feel by varying the apparent torsional stiffness of the torsion bar, effectively suppressing the negative effects of torsion bar twist during steering operations.
Implementation Method 1
a torque sensor configured to detect a steering torque based on a torsion amount of a torsion bar provided at the part of the steering shaft on the steering apparatus side
Data Source
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AI summary
Provided is a steering control apparatus capable of performing adjustment so as to suppress deterioration in a steering feel that is caused by a twist of a torsion bar. A torsional stiffness control circuit (70) includes a torsion angle calculation circuit (71), a gain calculation circuit (72), multiplication circuits (73, 74), and an addition circuit (75). The torsion angle calculation circuit (71) calculates a torsion angle (θtw) based on a steering torque (Th). The gain calculation circuit (72) calculates a gain (G) having a positive or negative value based on a value obtained by multiplying the steering torque (Th) and a steering speed (ω) together by the multiplication circuit (73). The multiplication circuit (74) calculates a compensation amount (θc) by multiplying the torsion angle (θtw) and the gain (G) together. The addition circuit (75) calculates a target pinion angle (θ2*) having a compensated phase by adding the compensation amount (θc) to a target steering angle (θ1*).