Motor Control Apparatus Current Suppression
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Solution Overview
Problem
Existing motor control systems struggle to properly suppress power source current when it exceeds a target value, especially in systems with varying wiring resistance, leading to potential damage and discomfort in vehicular electric power steering applications.
Innovation Solution
A motor control apparatus that calculates a suppression gain to limit the power source current by multiplying a voltage command with a value between 0 and 1, ensuring the absolute value of the power source current does not exceed a predetermined target, thereby preventing damage and maintaining system functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the current command value is restricted based on power source voltage and motor rotational angular speed, then power drawn from the direct current power source is restricted, but the apparatus cannot restrict to a predetermined current when wiring resistance value changes
Solution Approach 1:
The control apparatus calculates the actual power source current based on the voltage command value and detects whether it exceeds the target value. This feedback mechanism allows the system to adjust and maintain accurate current restriction despite changes in wiring resistance, resolving the contradiction between power restriction and restriction accuracy.
Solution Approach 2:
The system changes the control parameter from restricting current command value based on pre-set relationships to directly calculating actual power source current from voltage command and detecting its magnitude. This parameter change enables accurate current restriction under varying wiring resistance conditions.
2Reliability
If the inverter stops driving when abnormal voltage is detected, then switching elements are protected, but the assistive function for lightening steering force does not work
Solution Approach 1:
Instead of stopping the inverter when voltage rises, the system skips the harmful effect by calculating and suppressing the voltage command value to prevent excessive power source current. This allows the steering assist function to continue operating while protecting switching elements from damage.
Solution Approach 2:
The system converts the potentially harmful regenerative current that causes voltage rise into a beneficial controlled process by calculating the voltage command value to suppress power source current. This transforms a harmful situation into an opportunity to maintain both protection and functionality.
3Use of energy by moving object
If regenerative current flows into the power source, then power is recovered, but voltage rises and may damage switching elements
Solution Approach 1:
The system changes the control approach by calculating the voltage command value based on actual power source current detection. This parameter change enables the system to maintain regenerative power recovery while suppressing voltage rise that could damage switching elements.
Data Source
AI summary
A motor control apparatus operates a power conversion circuit connected between a direct current power source and a motor, which performs mutual conversion between power at the direct current power source and power at the motor in response to a powering operation and a regenerative operation carried out by the motor. The motor control apparatus includes: a voltage command calculator that calculates a voltage command to the power conversion circuit; a suppression gain calculator that calculates a suppression gain such that an absolute value of an estimation value of a power source current or an absolute value of a detection value of the power source current is not more than a target value; and a voltage command suppressor that suppresses a voltage command by multiplying the suppression gain to the voltage command calculated by the voltage command calculator. Additionally, the suppression gain is within a range of 0 to 1.