Electric Power Steering Control Device for Vibration Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing electric power steering systems experience vibration due to fluctuations in damping force, leading to a deterioration in steering feeling when end-abutting occurs, as the interaction between steering reaction force and angular velocity causes repetitive increases and decreases.
Innovation Solution
A control device that calculates a correction value for the steering assist torque based on the steering angular velocity, using a nonlinear steering reaction torque to reduce the rate of change of the steering reaction torque with respect to the angular velocity, thereby minimizing vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If damping force is calculated by multiplying steering angular velocity by gain, then impact at end-abutting is suppressed, but vibration occurs in the steering system due to fluctuation in steering reaction force
Solution Approach 1:
The patent changes the parameter relationship between steering reaction force and steering angular velocity from linear to nonlinear. Instead of using a constant gain multiplied by angular velocity, the patent uses a nonlinear function where the gain varies with steering angle, thereby stabilizing the steering reaction force and reducing vibration while still suppressing end-abutting impact.
Solution Approach 2:
The patent makes the damping force calculation dynamic by adjusting the gain based on the current steering angle. The gain is set to be larger when the steering angle is smaller and smaller when the steering angle is larger, creating a dynamic adjustment mechanism that adapts to different steering conditions and prevents vibration.
2Object-affected harmful factors
If steering reaction force increases to suppress end-abutting impact, then impact is reduced, but steering angular velocity decreases causing damping force to decrease and steering reaction force to increase again, creating vibration
Solution Approach 1:
The patent implements a feedback mechanism where the steering angle is continuously monitored and used to adjust the gain in the damping force calculation. This feedback loop ensures that as the steering angle changes, the damping force is adjusted accordingly to maintain stable steering angular velocity and prevent the oscillation between steering reaction force and angular velocity.
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
To reduce vibration occurring in a steering system when impact at the time of end-abutting is to be suppressed by torque depending on steering angular velocity. A control device includes a current command value calculation unit (31) configured to calculate a first current command value causing an actuator to generate steering assist torque, a correction value calculation unit (36) configured to, when an absolute value of steering angle is greater than or equal to a threshold value, calculate a correction value for suppressing increase in an absolute value of the steering angle by correcting the steering assist torque, a correction unit (37) configured to calculate a second current command value obtained by correcting the first current command value by the correction value, and a driving unit (32 to 35) configured to drive the actuator, based on the second current command value. The correction value calculation unit (36) calculates the correction value, based on first torque, the first torque changing nonlinearly with respect to steering angular velocity.