Electric Motor Current Superposition for Robust Torque Ripple Control
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Solution Overview
Problem
Existing electric motor control devices struggle to effectively suppress torque ripple due to errors in acquired electrical characteristics, as they do not account for variations in manufacturing and operating conditions, leading to incomplete torque ripple suppression.
Innovation Solution
An electric motor control device that includes a fundamental electric-current instruction generator, position dependency component generator, electric current correction instruction calculator, and controller, which calculates and superimposes d-axis and q-axis current correction instructions to reduce torque ripple sensitivity to errors in electrical characteristics, using a sensitivity setting-value to adjust the magnitude of these instructions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If torque ripple suppression control is implemented using preliminarily acquired electrical characteristics, then torque ripple can be suppressed under ideal conditions, but the suppression effect deteriorates when acquisition values deviate from true values due to manufacturing variations and operating state changes
Solution Approach 1:
The patent introduces a feedback mechanism where the actual torque ripple is detected and used to adjust the suppression control parameters. The controller monitors the torque ripple magnitude and dynamically modifies the current instruction values to compensate for deviations in electrical characteristics, ensuring consistent suppression effectiveness regardless of manufacturing variations or operating condition changes.
Solution Approach 2:
The patent changes the control parameters dynamically based on detected torque ripple characteristics. By adjusting the amplitude and phase of the compensation current instructions in real-time according to actual torque ripple measurements, the system maintains effective suppression even when preliminary electrical characteristic values are inaccurate.
2Device complexity
If only median values of electrical parameters are used for control, then the control system remains simple, but torque ripple suppression becomes insensitive to errors in electrical characteristic acquisition
Solution Approach 1:
The patent performs preliminary characterization of the torque ripple components by analyzing the electrical characteristics and predicting the suppression current requirements before actual operation. This preliminary action allows the system to pre-calculate compensation parameters that are robust to typical variations, reducing the need for complex real-time adjustments while maintaining suppression effectiveness.
Solution Approach 2:
The patent introduces dynamic adjustment capabilities that allow the control system to adapt its parameters based on actual operating conditions. The system can switch between different control strategies or adjust parameter sets depending on the detected torque ripple magnitude and frequency content, providing robustness without excessive complexity.
Data Source
AI summary
An electric motor control device, capable of suppressing a torque ripple even when electrical characteristics on a motor have errors or variations, comprises: a fundamental electric-current instruction generator for outputting d-axis and q-axis fundamental electric-current instructions for outputting fundamental torque from the motor having saliency; a position dependency component generator for outputting a position dependency component(s) of the motor according to its rotational position; an electric current correction instruction calculator for calculating d-axis and q-axis current correction instructions from the d-axis and q-axis fundamental electric-current instructions, and the position dependency component(s); an electric current correction instruction superposition unit for generating d-axis and q-axis current instructions by performing superposition of the d-axis and q-axis current correction instructions on the d-axis and q-axis fundamental electric-current instructions; and an electric current controller for controlling a current to flow through the motor by an inverter, based on the d-axis and q-axis current instructions.