PMSM Speed Control via Disturbance Observer and Current Saturation
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Solution Overview
Problem
Existing speed control methods for permanent magnet synchronous motors face challenges such as current saturation, instability due to chattering in sliding mode control, and the need for expensive sensors to measure state variables, which affect control accuracy and safety.
Innovation Solution
A speed control method that considers current saturation and disturbance suppression, using a mathematical model to estimate and compensate for system uncertainties and unknown load torque disturbances, employing a super-twisting disturbance observer and quasi-integral signal to constrain motor current within safe limits without requiring direct measurement of state variables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sliding mode control strategies are used to suppress disturbances, then robustness against system disturbances is improved, but chattering phenomenon occurs which affects control accuracy and system stability
Solution Approach 1:
The patent introduces a disturbance observer as an intermediary component that estimates system disturbances and parameters uncertainties. This observer acts as a mediator between the control input and the plant, providing disturbance compensation without requiring high-gain switching actions. The estimated disturbances are fed back to compensate for the actual disturbances, achieving robustness while avoiding chattering.
Solution Approach 2:
The patent replaces the mechanical sliding mode control mechanism (which relies on high-gain signum function and switching actions) with an observer-based compensation mechanism. Instead of using discontinuous switching control to achieve robustness, the system uses continuous disturbance estimation and compensation, substituting the mechanical switching action with an intelligent observation and compensation strategy.
2Device complexity
If current saturation is not considered in control design, then control algorithm simplicity is maintained, but current exceeds safe limits causing motor damage or system instability
Solution Approach 1:
The patent performs preliminary action by designing the control law to explicitly consider current saturation constraints before implementing the control. The control algorithm incorporates current limits in its formulation, ensuring that the control input is designed to keep currents within safe operating ranges from the beginning, rather than adding protective measures after the fact.
Solution Approach 2:
The patent implements feedback mechanisms where the disturbance observer continuously monitors system states and estimates disturbances. This feedback information is used to adjust the control input in real-time, ensuring that current constraints are respected while maintaining control performance. The feedback loop provides continuous adjustment to prevent current saturation.
3Measurement precision
If expensive high-precision sensors are used to measure state variables, then measurement precision is improved, but system cost increases
Solution Approach 1:
The patent enables the system to self-service by using the disturbance observer to estimate unmeasured state variables and disturbances based on available measurements. Instead of requiring expensive sensors to directly measure all state variables, the system uses its own output measurements and a mathematical model to infer the missing information, making the system self-sufficient in terms of state estimation.
Solution Approach 2:
The patent substitutes expensive physical sensors with a virtual sensing mechanism implemented through the disturbance observer. Rather than using hardware sensors to directly measure state variables like load torque or parameters uncertainties, the system uses software-based estimation algorithms that process available measurements to infer the desired information, replacing costly mechanical/sensor systems with computational methods.
Data Source
AI summary
A speed control method for a permanent magnet synchronous motor considering current saturation and disturbance suppression aims to effectively ensure that a current of the motor is always within a given range to avoid the problem of control performance reduction caused by the fact that the current gets into a saturation state, ensure the safety of a system, do not need to use unavailable state variables such as motor acceleration and the like, effectively estimate and compensate disturbances including parameters uncertainty and unknown load torque disturbance existing in a permanent magnet synchronous motor system, and rapidly and accurately control a speed of the motor finally. There is no need to configure a plurality of sensors in practical industrial application, so system building costs can be reduced on the one hand, and the stability of the system can be improved on the other hand.