Motor Driving System Offset Correction
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Solution Overview
Problem
Existing motor driving systems face poor performance due to torque variation caused by current sensor offset, which cannot be corrected while the vehicle is traveling, leading to inaccurate feedback control.
Innovation Solution
A motor driving system that includes a control circuit with an offset value learning part, capable of learning current sensor offsets even when the vehicle is in motion by utilizing the relationship between induced motor voltage and input voltage to determine optimal phases for offset calculation, allowing for continuous offset correction without stopping the vehicle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the vehicle stops to correct current sensor offset, then offset correction accuracy is improved, but vehicle productivity deteriorates
Solution Approach 1:
The patent applies the dynamics principle by enabling offset correction to occur during vehicle operation rather than requiring the vehicle to stop. The system dynamically identifies correction opportunities by monitoring switching element off-states and induced voltage conditions, allowing continuous or near-continuous offset correction without interrupting vehicle productivity.
Solution Approach 2:
The patent implements preliminary action by proactively detecting and correcting current sensor offsets during appropriate moments in the operating cycle (when switching elements are off and induced voltage conditions are favorable). This prevents offset accumulation that would otherwise require vehicle stops for correction, maintaining both accuracy and productivity.
2Reliability
If the CPU is reset during vehicle travel, then system reliability is improved through error recovery, but offset value retention deteriorates
Solution Approach 1:
The patent applies beforehand cushioning by implementing a mechanism that continuously monitors for correction opportunities and maintains the capability to correct offsets even after CPU resets. The system prepares for potential offset loss by being ready to perform correction at the next appropriate moment, cushioning against the information loss caused by CPU resets.
Solution Approach 2:
The patent uses feedback by continuously monitoring current sensor readings and comparing them against expected values during switching off-states. This feedback mechanism detects offset conditions and triggers correction actions, ensuring that offset values are maintained across CPU reset cycles through continuous verification and correction.
3Ease of operation
If offset correction is performed only in neutral position, then correction simplicity is improved, but control performance deteriorates
Solution Approach 1:
The patent applies universality by expanding offset correction capability from the limited neutral position scenario to multiple operating conditions. The system can perform offset correction during any switching off-state when induced voltage conditions are appropriate, making the correction function universal across different vehicle operating modes including driving ranges, thereby maintaining simple operation while improving control performance.
Solution Approach 2:
The patent implements parameter changes by using induced voltage magnitude as a criterion to determine when offset correction can be performed. By monitoring the relationship between induced motor voltage and input voltage, the system identifies appropriate correction moments across various operating conditions, transitioning from fixed-position correction to condition-based correction that maintains simplicity while enhancing accuracy.
Data Source
AI summary
A motor driving system includes an offset value learning part, which learns offset values of current sensors, when all switching elements are in off-states and a motor driving circuit is in an off-state, in which the motor driving circuit generates no motor driving current. The offset value learning part includes a first learning part and a second learning part. The first learning part learns the offset value of the current sensor of each phase at an arbitrary motor rotation angle, when an induced motor voltage of a three-phase motor is smaller than an input voltage of the motor driving circuit. The second learning part sequentially learns the offset value of the current sensor of the phase, a phase voltage value of which varying with the motor rotation angle is intermediate, when the induced motor voltage is equal to or larger than the input voltage.