Three-Phase Motor Offset Learning via Transmission Shift Control
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Solution Overview
Problem
The accuracy of offset learning for a rotational position sensor in a three-phase motor system is compromised at low motor speeds due to increased d-axis voltage command errors, leading to low-accuracy learning results.
Innovation Solution
Implementing learning shift control to maintain the transmission shift stage within a low vehicle speed-side predetermined range during offset learning, ensuring the motor operates at higher rotational speeds and minimizing torque command discrepancies, thereby enhancing learning accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If offset learning is carried out at low motor speeds, then the learning process can be completed, but the d-axis voltage command error increases and learning accuracy decreases
Solution Approach 1:
The patent changes the operating parameters during offset learning by controlling the transmission to maintain motor rotational speed within a predetermined range (avoiding low speeds). This parameter control ensures that the d-axis voltage command remains sufficiently large, thereby maintaining high learning accuracy while completing the offset learning process
2Measurement precision
If the transmission shift stage is not controlled during offset learning, then the learning procedure is simple, but the motor speed varies and learning accuracy deteriorates
Solution Approach 1:
The patent performs preliminary action by controlling the transmission shift stage before and during offset learning. The electronic control unit determines appropriate shift stages in advance and controls the transmission to maintain motor speed within the predetermined range, ensuring accurate offset learning before normal operation resumes
Solution Approach 2:
The patent implements feedback control by continuously monitoring motor rotational speed during offset learning and adjusting the transmission shift stage accordingly. The electronic control unit uses speed feedback to determine whether to maintain or change shift stages, ensuring the motor operates within the optimal speed range for accurate learning
Data Source
AI summary
With a motor in rotation, 0 is set as each of a d-axis current command and a q-axis current command, and offset learning is carried out. Then, in carrying out offset learning, a transmission is controlled such that a shift stage of the transmission falls within a low vehicle speed-side predetermined shift stage range. Thus, the rotational speed of the motor can be more reliably made high to a certain extent, and offset learning can be carried out. As a result, the accuracy of offset learning can be restrained from decreasing.