Motor Control Bandwidth Compensation for Torque Ripple
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Solution Overview
Problem
Interior permanent magnet synchronous motors (IPMSMs) produce significant torque ripple, which is undesirable in applications like electric power steering, and existing methods to compensate for torque ripple are less effective at high motor velocities.
Innovation Solution
A motor control system that includes a torque ripple compensation controller and a bandwidth compensation controller, which calculate and apply ripple compensating currents to counteract torque ripple by determining current harmonics and phase outputs using look-up tables and PI compensation, effectively reducing torque ripple and noise at high velocities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If torque ripple compensation is applied using conventional methods, then torque ripple is reduced at low motor velocities, but compensation effectiveness diminishes at high motor velocities
Solution Approach 1:
The patent implements dynamic adaptation of compensation parameters based on motor velocity. The system switches between different compensation strategies: conventional torque ripple compensation at low velocities and bandwidth compensation with modified PI controller gains at high velocities. This dynamic switching ensures effective torque ripple reduction across the entire velocity range by adapting control parameters to operating conditions.
Solution Approach 2:
The system changes control parameters (PI controller gains, compensation current injection) based on motor velocity. At high velocities, the bandwidth compensation controller increases proportional gain and adjusts integral gain to maintain compensation effectiveness. This parameter adaptation allows the system to overcome the velocity-dependent limitation of conventional compensation methods.
2Ease of manufacture
If IPMSM is used for cost-effectiveness, then manufacturing cost is reduced, but torque ripple increases
Solution Approach 1:
The patent converts the inherent torque ripple characteristic of IPMSM into a compensatable signal. By identifying the torque ripple components through current harmonics and using look-up tables to determine compensation currents, the system transforms the harmful torque ripple effect into a measurable and compensatable parameter, allowing cost-effective IPMSM to meet low torque ripple requirements.
Solution Approach 2:
The system employs feedback mechanisms where torque ripple compensation currents are determined based on measured motor operating conditions (velocity, current harmonics). The bandwidth compensation controller continuously adjusts compensation signals based on feedback from the motor's actual performance, enabling the cost-effective IPMSM to achieve low torque ripple through active compensation rather than passive design changes.
3Object-generated harmful factors
If bandwidth compensation controller with high proportional gain is used at high velocities, then torque ripple compensation effectiveness is improved, but system stability may be compromised
Solution Approach 1:
The system dynamically adjusts PI controller gains based on motor velocity to maintain stability while improving compensation effectiveness. At high velocities, the bandwidth compensation controller increases proportional gain to enhance torque ripple compensation, while simultaneously adjusting integral gain to prevent instability. This coordinated parameter adaptation allows the system to achieve both high compensation effectiveness and stability across the velocity range.
Solution Approach 2:
The control system transitions from static to dynamic gain scheduling, where controller parameters are continuously adapted to operating conditions. The bandwidth compensation controller implements velocity-dependent gain adjustment that increases proportional gain at high velocities for better compensation while maintaining stability through coordinated integral gain adjustment. This dynamic approach resolves the trade-off between compensation effectiveness and stability.
Data Source
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AI summary
A motor control system for determining a ripple compensating current is provided. The motor control system includes a motor having a plurality of motor harmonics and a motor frequency, and a bandwidth compensation controller that is in communication with the motor. The bandwidth compensation controller is configured to determine a magnitude response compensation value and a phase compensation value for each of the plurality of motor harmonics. The magnitude response compensation value and the phase compensation value are both based on the motor frequency. The bandwidth compensation controller is configured to determine the ripple compensating current based on the magnitude response compensation value and the phase compensation value.