Brushless Motor Control Device Phase Difference Correction
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Solution Overview
Problem
In brushless motor control systems, a phase difference between the estimated and actual d-axis can cause the command current vector to diverge from the desired values, leading to torque and velocity deviations, which deteriorate controllability.
Innovation Solution
A motor control device that calculates a command current vector based on a command torque and adjusts its direction according to the phase difference between the estimated and actual d-axis, ensuring the vector remains within the voltage and current limit circles, thereby maintaining alignment with the actual motor currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the command current vector is calculated based on the command torque without phase difference correction, then the control calculation is simple, but the command current diverges from the actual current when phase difference is large, deteriorating controllability
Solution Approach 1:
The phase difference calculation unit calculates the phase difference between the estimated d-axis and the actual d-axis in advance, before the command current vector is applied to the motor. This preliminary calculation allows the change unit to pre-adjust the command current vector's direction, ensuring that even when a large phase difference exists, the adjusted command current aligns with the actual motor currents, thereby maintaining controllability without overly complicating the control system
Solution Approach 2:
The change unit modifies the direction parameter of the command current vector based on the calculated phase difference. By dynamically adjusting the angular parameter of the command current vector to compensate for the phase difference, the system ensures that the command currents (d-axis and q-axis) remain aligned with the actual motor currents, preventing divergence and maintaining reliable control even under varying operating conditions
2Reliability
If the phase difference is large, then the command current point may be located outside the voltage limit circle and current limit circle region, but adjusting the command current to stay within limits causes divergence from actual currents
Solution Approach 1:
The change unit rotates the command current vector by the calculated phase difference angle, adjusting its directional parameters to align with the actual d-axis and q-axis. This parameter adjustment ensures that even when the unadjusted command current point would fall outside the voltage and current limit circles, the adjusted command currents properly reflect the motor's actual current components, preventing torque and velocity deviations while maintaining control accuracy within the operational limits
Data Source
AI summary
A motor control device includes a command current derivation unit that derives a command current vector based on a command torque for a brushless motor, a phase difference derivation unit that derives a phase difference between a direction of a real d-axis of rotating coordinates of vector control and a direction of an estimated d-axis thereof, a change unit that changes a direction of the command current vector derived by the command current derivation unit according to the phase difference, and a drive control unit that drives the brushless motor based on the command current vector whose direction is changed by the change unit.