Inverter Output Ratio Control for Electric Power Steering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In electric power steering systems with multiple inverters, a failure in one inverter can lead to an abrupt increase in required steering force when the driver temporarily stops steering, as the remaining inverter cannot adequately compensate for the lost current, affecting vehicle controllability and safety.
Innovation Solution
The system diagnoses inverter failures and adjusts the output ratios of functioning and failed inverters to maintain total output, gradually lowering the limit value for the total output if steering is resumed after a failure, to prevent sudden increases in steering force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the output of the normally operating inverter is doubled to compensate for the failing inverter, then the total output is maintained, but the required steering force increases abruptly when steering operation is temporarily stopped and resumed
Solution Approach 1:
The patent applies dynamics by making the output ratio of inverters changeable over time. When a failure is detected, the system dynamically adjusts the output ratio of the normally operating inverter based on whether steering operation is currently being performed. During active steering, the output ratio is increased to maintain total output, but when steering is temporarily stopped, the output ratio is reduced to prevent overheating, and then gradually restored upon resumption of steering operation.
Solution Approach 2:
The patent applies preliminary action by detecting inverter failures in advance and preparing appropriate output ratio adjustments before steering operation is temporarily stopped. The system monitors inverter status continuously and pre-configures the output ratio adjustment strategy, so when steering operation is interrupted, the normally operating inverter's output can be appropriately reduced to prevent overheating, and then gradually increased upon resumption.
2Power
If the normally operating inverter supplies twice the current to compensate for the failing inverter, then the total current output is maintained, but the inverter may overheat and fail
Solution Approach 1:
The patent applies dynamics by making the output ratio of inverters changeable over time. When a failure is detected, the system dynamically adjusts the output ratio of the normally operating inverter based on whether steering operation is currently being performed. During active steering, the output ratio is increased to maintain total output, but when steering is temporarily stopped, the output ratio is reduced to prevent overheating, and then gradually restored upon resumption of steering operation.
Solution Approach 2:
The patent applies periodic action by implementing periodic monitoring of inverter operation status and temperature, and periodically adjusting the output ratio accordingly. The control unit continuously monitors whether steering operation is being performed and adjusts the output ratio in periodic intervals, reducing output during temporary stops and gradually increasing it upon resumption, thereby preventing overheating while maintaining reliability.
3Force
If the output ratio of the normally operating inverter is increased to maintain total output, then the steering assist force is maintained during failure, but the steering force increases abruptly when steering operation is temporarily stopped and resumed
Solution Approach 1:
The patent applies dynamics by making the output ratio of inverters changeable over time. When a failure is detected, the system dynamically adjusts the output ratio of the normally operating inverter based on whether steering operation is currently being performed. During active steering, the output ratio is increased to maintain total output, but when steering is temporarily stopped, the output ratio is reduced to prevent overheating, and then gradually restored upon resumption of steering operation.
Solution Approach 2:
The patent applies feedback by continuously monitoring the operation status of inverters and the state of steering operation, and using this feedback information to adjust the output ratio of the normally operating inverter. The control unit receives feedback on whether steering is being performed and adjusts the output ratio accordingly, ensuring that the steering assist force remains stable and consistent throughout the temporary stop and resumption cycle.
Data Source
AI summary
Provided is a control device 150 for an electric motor 140 which includes multiple energization systems each including an inverter and coils corresponding to different phases, and which generates a steering assist force in an electric power steering system. Control device 150 diagnoses whether any of inverters 1A and 1B fails, and, when either of the inverters is diagnosed as having failed, reduces the output ratio of the failing inverter to 0% while increasing the output ratio of the normally operating inverter to 100% so as to prevent a drop in the total output from all the inverters after the failure-positive diagnosis. If steering operation is performed after the failure-positive diagnosis, control device 150 performs overheat protection processing for gradually lowering the limit value for the total output from all the inverters in accordance with the sensed temperature of the normally operating inverter.