Motor Control Backup Switching for Steering Power Continuity
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Solution Overview
Problem
Conventional motor control devices fail to prevent the loss of motor output function when using a backup power supply with small capacity, leading to potential stops in motor operation, especially in electric power steering systems.
Innovation Solution
A motor control device with a power supply switching determination unit that switches between a main power supply and a backup power supply, employing a drive control unit to output calculated drive signals via feedback control, limiting power consumption to prevent the backup power supply from stopping, thereby maintaining motor function.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If a backup power supply with small capacity is used, then the size and cost of the power supply system is reduced, but the risk of power supply stopping increases
Solution Approach 1:
The control device dynamically changes operating parameters (current limits, torque commands) based on power supply state detection. When backup power supply is detected, the system adjusts current detection values and torque current limits to match the reduced capacity, preventing overdraw and ensuring continuous operation.
Solution Approach 2:
The system implements feedback control by detecting the power supply state and using this information to adjust control parameters. The control device continuously monitors whether main or backup power supply is active and modifies current commands and torque limits accordingly, creating a closed-loop system that adapts to power availability.
2Speed
If the current command value is increased to maintain motor speed during backup power supply, then the motor rotation speed is maintained, but the backup power supply stops due to excessive power consumption
Solution Approach 1:
The system changes current parameters based on power supply state. During backup power supply operation, the control device reduces current detection values and torque current limits compared to normal operation, ensuring power consumption remains within the backup supply's capacity while maintaining adequate motor function.
Solution Approach 2:
The system applies partial action by providing reduced but sufficient current during backup operation. Rather than attempting to maintain full performance levels, the system provides just enough current to maintain essential motor rotation and steering function within the backup power supply's limitations.
3Speed
If the d-axis current of field weakening control is increased to suppress voltage drop, then the motor rotation speed reduction is suppressed, but the power consumption exceeds the backup power supply capacity
Solution Approach 1:
The control device adjusts field weakening control parameters based on power supply state. During backup operation, the system modifies d-axis current commands and field weakening intensity to balance speed stability with power consumption constraints, preventing excessive energy draw while maintaining acceptable rotation speed.
4Reliability
If torque current limit value is restricted to prevent power supply stopping, then the backup power supply remains stable, but the motor output torque is reduced
Solution Approach 1:
The system dynamically changes torque current limit parameters based on detected power supply state. When backup power supply is active, the control device reduces torque current limits compared to normal operation, preventing power overload while maintaining sufficient torque for essential steering functions.
Solution Approach 2:
The system applies partial torque output during backup operation, providing just enough current and torque to maintain essential steering capability within the backup power supply's capacity, rather than attempting to maintain full torque output.
Data Source
AI summary
A main power supply having a large capacity and a backup power supply having a small capacity are switchable by a power supply switching determination unit in a system. A motor control device drives a motor by the main power supply or the backup power supply. A drive control unit outputs a drive signal, calculated by feedback control of the current detection value with respect to the current command value, to an inverter circuit. When the power supply switching determination unit switches from the main power supply to the backup power supply, the drive control unit moves from a normal control using the main power supply to a backup control that restricts an electric power consumption and prevents the backup power supply from stopping.