Electric Motor Circuit Control for Back-EMF Disturbance Rejection
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Solution Overview
Problem
Existing motor control systems fail to adequately compensate for voltage disturbances such as cross-coupling and back-EMF in Interior Permanent Magnet Synchronous Motors (IPMSM), leading to degraded static and dynamic performance.
Innovation Solution
A control system comprising a current controller, an observer, a feed-forward controller, and compensating means that generates modified voltage demands by combining idealized voltage demands with correction signals from the observer and feed-forward controller, using smooth estimates of motor currents and angular velocity to compensate for voltage disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feed-forward control is used to compensate for voltage disturbances, then disturbance compensation capability is improved, but sampling delay degrades control accuracy
Solution Approach 1:
The system calculates cross-coupling and back-EMF voltage disturbances in advance using the mathematical model and available measurements (currents, angular velocity) before they fully affect the motor output. This preliminary calculation allows compensation to be applied proactively rather than reactively, reducing the effective delay impact.
Solution Approach 2:
The system uses measured motor currents and angular velocity as feedback signals to continuously update the disturbance estimates in the mathematical model. This feedback mechanism ensures that the feed-forward compensation remains accurate despite model uncertainties and parameter variations.
2Reliability
If mathematical model is used for feed-forward control, then disturbance compensation is improved, but parameter variations degrade compensation accuracy
Solution Approach 1:
Measured motor currents and angular velocity serve as continuous feedback signals that update the disturbance estimates in the mathematical model. This feedback loop allows the system to adapt to parameter variations and model inaccuracies by continuously correcting the disturbance compensation based on actual system behavior.
Solution Approach 2:
The system accepts and adapts to parameter variations in motor inductances, resistances, and back-EMF constants by using measured currents and angular velocity to dynamically adjust the disturbance estimates. Rather than requiring fixed parameters, the system allows parameters to change and be compensated through continuous measurement and model updating.
3Device complexity
If simple feed-forward control is implemented, then device complexity is reduced, but control precision deteriorates due to unaddressed voltage disturbances
Solution Approach 1:
The system incorporates angular velocity measurements and current measurements as additional parameters in the mathematical model to calculate disturbance voltages. By utilizing these readily available parameters, the system achieves enhanced control precision without requiring complex additional sensors or hardware, maintaining relative simplicity while improving accuracy.
Data Source
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AI summary
A control system for an electric motor circuit comprises a current controller which produces a set of idealised voltage demands for the motor circuit, an observer which observes the inputs to the motor circuit and the outputs of the motor circuit and which generates from the observations estimates of the voltage disturbances within the motor circuit, the observer being arranged in use to output a first correction signal indicative of the voltage disturbances in the motor circuit, a feed-forward controller which receives as an input a measurement or estimate of the current flowing in the motor and calculates from the input a second correction signal. The first correction signal output from the observer and the second correction signal output from the feedforward controller are combined with the idealised voltage demands output from the controller to provide a set of modified voltages demands that are fed to the motor.