Motor Control Device Dither Control for EPS Steering
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Solution Overview
Problem
In electric power steering apparatuses, defects in motors or inverters lead to unintended motor current chattering and torque vibration during deceleration, deteriorating the steering feeling for drivers, as conventional acceleration controls fail to prevent these issues effectively.
Innovation Solution
A motor control device and method that switches from n-phase to n-1 phase energization control, using a processor to generate current command values through dither control within specific electrical angle ranges, thereby performing n-1 phase energization to mitigate chattering and improve steering stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If n-1 phase energization control is performed after a winding defect occurs, then motor driving can be continued, but current chattering and torque vibration occur during deceleration
Solution Approach 1:
The patent applies periodic dither control by superimposing a high-frequency alternating current component on the basic current command value during deceleration. This periodic action prevents the motor current from settling into a chattering state by continuously introducing small controlled variations, thereby eliminating the harmful current chattering and torque vibration while maintaining n-1 phase energization control
Solution Approach 2:
The patent changes the current command parameters by adding a dither component to the basic current command. This parameter modification transforms the steady current command into a dynamically varying command that prevents chattering. The dither amplitude and frequency are carefully selected to suppress vibrations without affecting the overall motor performance during deceleration in n-1 phase operation
2Ease of operation
If acceleration control is executed in deceleration section, then non-smoothness in steering operation is suppressed, but current chattering occurs in n-1 phase energization control
Solution Approach 1:
The patent introduces dither control as an intermediary mechanism between the acceleration control and the motor current. This intermediary layer processes the current command and adds appropriate dither components, allowing acceleration control to maintain steering smoothness while the dither intermediary prevents the current chattering that would otherwise occur in n-1 phase energization during deceleration
Data Source
AI summary
To improve steering feeling felt by a driver, a motor control device includes a processor and a memory which stores a program for controlling an operation of the processor. According to the program, the processor executes: switching from n-phase (n is an integer of three or more) energization control to n−1 phase energization control in response to a switching signal; acquiring a torque command value, an electrical angle of a motor, and an actual current value of the motor; generating a pre-current command value on the basis of the torque command value, the electrical angle of the motor, and the actual current value of the motor which are acquired; generating a current command value by applying dither control to the pre-current command value in a dead point range of an electrical angle range from 0 to 2π; and performing the n−1 phase energization control on the basis of the current command value.