Motor Driving Device Current Limiting for Steering Systems
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Solution Overview
Problem
Motor driving devices face issues with inappropriate limiting of command current values, leading to decreased followability of motor currents with respect to command current changes, resulting in erroneous feedback operations and deteriorated motor controllability, causing unintentional sounds and vibrations.
Innovation Solution
A motor driving device that determines whether the motor current is in a less-response situation based on a relationship between the motor current and a calculation value, and adjusts the command current limit accordingly to prevent excessive deviations and maintain appropriate followability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the command current value is limited to prevent motor current exceeding, then the motor current followability with respect to command current changes deteriorates
Solution Approach 1:
The patent applies dynamics by making the current limitation value variable rather than fixed. The limitation value is dynamically adjusted based on the relationship between command current and actual motor current, allowing the system to adapt the limitation threshold in real-time to maintain both accuracy and followability under different operating conditions
Solution Approach 2:
The patent changes the parameter of current limitation value from a constant to a variable that depends on the ratio between command current and actual motor current. This parameter change allows the system to optimize the limitation threshold dynamically, improving both limitation accuracy and current followability
2Ease of operation
If feedback operation is performed based on deviation between command current and actual motor current, then motor controllability improves, but unintentional sounds and vibrations occur due to erroneous feedback
Solution Approach 1:
The patent uses feedback by continuously monitoring the actual motor current and comparing it with the command current. The feedback mechanism calculates the deviation and adjusts the limitation value accordingly, enabling precise control while preventing erroneous feedback operations that cause unwanted sounds and vibrations
Solution Approach 2:
The patent applies preliminary anti-action by proactively limiting the command current value before it can cause excessive motor current. The system predicts potential overcurrent conditions and preemptively adjusts the limitation threshold, preventing the harmful effects before they occur
Data Source
AI summary
In a motor driving device, a current detector detects a value of the motor current, and a limit variable calculator calculates a calculation value of a limit variable for limiting the command current. A determiner determines, based on a relationship between the value of the motor current and the calculation value of the limit variable, whether the motor current is in a less-response situation to change of the command current. A current limiter determines whether to limit a value of the command current based on the calculation value of the limit variable in accordance with a result of the determination of whether the motor current is in the less-response situation to change of the command current.