Motor Torque Ripple Compensation Under Current Limit Constraints
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Solution Overview
Problem
Existing motor control methods fail to effectively suppress torque ripple when the torque command value approaches the output current limit, leading to unintended torque ripple and decreased average torque.
Innovation Solution
A motor control device that calculates a torque ripple compensation value based on electrical angular velocity and torque command, adjusts the amplitude of each frequency component within an amplitude limit, and corrects the torque command to minimize torque ripple while adhering to current constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a torque ripple compensation value is superimposed on the torque command value, then torque ripple is suppressed, but the output current may exceed the upper limit value
Solution Approach 1:
The patent applies dynamics by making the torque ripple compensation value adjustable based on operating conditions. The compensation value is determined dynamically according to the torque command value and electrical angular velocity, allowing the system to adapt the compensation amount to prevent current limits from being exceeded while still suppressing torque ripple when safe to do so
Solution Approach 2:
The patent changes parameters by adjusting the torque ripple compensation value based on the torque command value and electrical angular velocity. When the torque command value is high (close to upper limit), the compensation value is reduced or set to zero to prevent current limits from being exceeded, while at lower torque values, full compensation is applied to suppress torque ripple effectively
2Reliability
If the amplitude of torque ripple compensation value is limited to prevent current exceedance, then output current compliance is maintained, but unintended torque ripple may occur
Solution Approach 1:
The system dynamically adjusts the torque ripple compensation strategy based on real-time operating conditions. At high torque command values, compensation is limited or disabled to ensure current compliance, while at lower values, full compensation is applied, creating a dynamic transition that maintains both current safety and torque ripple suppression
3Reliability
If the torque command value is limited to maintain current within upper limit, then current compliance is ensured, but average torque decreases
Solution Approach 1:
The patent applies partial action by providing torque ripple compensation only when necessary (when torque command value allows). Instead of always applying full compensation or never applying it, the system partially applies compensation based on the operating point, achieving sufficient torque ripple suppression without consistently compromising the torque command
Data Source
AI summary
A motor control device includes a torque ripple compensation value computation unit that calculates a torque ripple compensation value for compensating for torque ripple occurring in a motor based on an electrical angular velocity of the motor and a torque command value; a ripple amplitude upper limit value calculating unit that calculates a ripple amplitude upper limit value which is an upper limit value for an amplitude of the torque ripple compensation value based on the torque command value and a torque upper limit value set for the motor; and an amplitude adjustment unit that adjusts an amplitude of each frequency component in the torque ripple compensation value based on the ripple amplitude upper limit value and calculates an amplitude-adjusted torque ripple compensation value.