Dual Sliding-Mode Observer for PMSM Sensorless Control

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Solution Overview

Problem

Existing sliding-mode observers for permanent magnet synchronous motors suffer from severe buffeting phenomena and poor load capability, leading to poor control performance, especially in medium and high-speed domains.

Innovation Solution

The implementation of an exponential piecewise sliding-mode function and a second-order sliding-mode controller based on a super-twisting algorithm, along with a load sliding-mode observer, to estimate rotational speed and rotor position, and improve load capability by fine-tuning PI controller parameters and providing feedforward compensation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a traditional sliding-mode observer is used to estimate rotor position and speed, then sensorless control can be achieved, but severe buffeting phenomenon and poor load capability occur

Engineering Contradiction:

Improvesensorless control reliabilityVSAvoidbuffeting phenomenon

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The patent transforms the traditional first-order sliding-mode observer into a second-order sliding-mode observer by changing the differential equation order and introducing a new sliding-mode surface definition. This parameter change in the observer structure fundamentally alters the system dynamics, eliminating buffeting while maintaining sensorless control functionality through modified state estimation equations

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces dynamic adaptation mechanisms including variable gain parameters and adaptive sliding-mode surfaces that adjust according to operating conditions. The observer gains and surface coefficients are dynamically modified based on speed and load conditions, enabling the system to maintain optimal performance across different operating ranges while suppressing buffeting

Inventive Principle:

Principle #15Dynamics

2Measurement precision

If a traditional sliding-mode observer is used, then rotor position estimation is possible, but control performance deteriorates under load

Engineering Contradiction:

Improverotor position estimation accuracyVSAvoidload capability

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent implements a dual-loop feedback structure where the second-order sliding-mode observer provides inner-loop state estimation feedback, and the PI controller provides outer-loop speed regulation feedback. This nested feedback architecture continuously corrects estimation errors and maintains accurate rotor position tracking even under varying load conditions through real-time error compensation

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent performs preliminary compensation by introducing feedforward terms based on predicted load variations and pre-calculated compensation currents. The controller anticipates load changes and applies corrective actions before they significantly impact performance, maintaining stable operation across different load levels

Inventive Principle:

Principle #10Preliminary action

3Ease of operation

If PI controller parameters are fixed, then control implementation is simple, but tracking performance is poor and parameter adjustment is difficult

Engineering Contradiction:

Improvecontrol implementation simplicityVSAvoidtracking performance

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The patent implements dynamic parameter adaptation where PI controller gains are automatically adjusted based on operating conditions such as speed and load. The controller transitions from fixed parameters to variable parameters that adapt in real-time, improving tracking performance across different operating ranges while maintaining ease of operation through automatic adaptation rather than manual tuning

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent enables the controller to self-adjust its parameters based on real-time system state feedback. The adaptive mechanism automatically optimizes PI gains without requiring external intervention or complex manual tuning, allowing the system to serve itself by continuously optimizing its own control parameters based on observed performance

Inventive Principle:

Principle #25Self-service

Data Source

PatentUS11522480B2SPMSM sensorless composite control method with dual sliding-mode observers

Publication Date: 2022.12.06 XIANGTAN UNIV

AI summary

A PMSM sensorless composite control method with dual sliding-mode observers is provided. In particular, two sliding-mode observers are designed, one provides an exponential piecewise sliding-mode function for observation of back electromotive force, and the other sliding-mode observer is for observation of load torque and fine-tuning parameters of a piecewise PI controller while introducing an estimated load torque onto a q-axis for feedforward compensation. A q-axis current inner loop is designed with a second-order sliding-mode controller, which can improve tracking performance of q-axis current and indirectly control an electromagnetic torque. The exponential piecewise sliding-mode function is more conductive to the observation of back electromotive force and can weaken the buffeting phenomenon. The sliding-mode observer for observing the load torque fine-tunes parameters of the piecewise PI controller while performing the feedforward compensation, the load capability of the system is improved. The second-order sliding-mode controller can reduce a torque ripple.