Electric Motor Control Reducing Torque Ripple via Phase Adjustment
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Solution Overview
Problem
The steering device motor described in Patent Literature 1 experiences significant torque ripple when the system B group fails, leading to variations in torque generation positions in the circumferential direction due to the arrangement of system A-1 and A-2 facing each other.
Innovation Solution
A motor control device with a stator core and coil groups divided into two independent systems for each phase, where a control device outputs command values for three-phase AC currents to each coil group, and a phase difference adjusting unit ensures the second motor drive current has a phase difference from the first, reducing torque ripple and enhancing redundancy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coil groups of at least two systems are excited simultaneously to improve motor reliability and redundancy, then the motor can continue operating even if one system fails, but torque ripple increases due to variation in torque generation positions in the circumferential direction
Solution Approach 1:
The patent changes the phase parameter of the three-phase alternating currents supplied to different coil groups. By adjusting the phase difference between currents supplied to system A and system B coil groups, the torque ripple caused by simultaneous excitation is reduced, while maintaining the reliability benefit of having redundant systems.
2Device complexity
If system A-1 and system A-2 are arranged to face each other in the diameter direction to simplify motor structure, then the motor structure becomes more compact, but torque ripple increases due to large variation in torque generation positions
Solution Approach 1:
The patent applies phase parameter changes to the currents supplied to coil groups arranged in the diameter direction. By adjusting the phase difference of the three-phase currents, the torque ripple generated by this specific arrangement is reduced, allowing the compact structure to be maintained without suffering from excessive torque ripple.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively suppresses torque ripple when both coil groups are excited simultaneously, improving the motor's performance and reducing the likelihood of operator discomfort due to vibration, thereby providing a comfortable steering experience.
Implementation Method 1
a plurality of coil groups divided into a first coil group and a second coil group of at least two systems for each phase, and configured to excite the stator core by three-phase alternating currents
Data Source
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AI summary
A motor control device 100 includes a motor 10, a control device 40, and a motor drive circuit 50. The motor 10 includes a motor rotor 20, a motor stator 30, and a plurality of coil groups divided into a first coil group G1 and a second coil group G2 of at least two systems for each of three phases, and configured to excite a stator core 31 by three-phase alternating currents. In the motor drive circuit 50, a first motor drive circuit 50A supplies a three-phase AC first motor drive current to the first coil group G1 based on a command value, and a second motor drive circuit 50A supplies a three-phase AC second motor drive current having a phase difference from a phase of the first motor drive current, to the second coil group G2.