Second-Order Sliding Mode-Based Direct Torque Control of Variable-Flux Memory Machine

Abstract

The variable-flux memory machine (VFMM) exhibits high efficiency over a wide speed range because its airgap magnetic flux can easily be regulated by varying the magnetization state (MS) of the employed low coercivity force permanent magnets. This paper proposes a second-order sliding mode (SM)based direct torque control (DTC) strategy for the VFMM, which features a relatively low computational complexity and less dependence on machine parameters. The operating principle and mathematical model of the VFMM are first described and established. On this basis, a novel control scheme combining the DTC strategy with MS manipulation is proposed, in which the machine is controlled by utilizing the DTC strategy incorporating the i d = 0 condition, while the MS manipulation is implemented by energizing reference stator flux linkage pulses. A super-twisting second-order SM controller is subsequently developed to achieve strong robustness. The developed control structure avoids a complicated decoupling algorithm and is simpler than that of the conventional field-oriented control (FOC) method. Finally, the effectiveness of the proposed control scheme is validated by simulation and experimental results. INDEX TERMS Direct torque control, magnetization state, strong robustness, super-twisting sliding mode control, variable-flux memory machine.

A DSP-Controlled Permanent Magnet Synchronous Motor Control System for Hybrid Vehicles

“…e mathematical model was first established and the maximum torque current ratio control was proposed at a low speed [17]. e current control strategy of full speed domain controlled by a weak magnetic field is adopted at medium and high speed, and the mathematical model of solving each control is analyzed [18].…”

Design of Sensorless Speed Control System for Permanent Magnet Linear Synchronous Motor Based on Fuzzy Super-Twisted Sliding Mode Observer

“…. d ≤ k ed (7) where k ed is an ordinary constant and k ed > 0. Let v r be the specified speed of the system, then the speed tracking error is defined as:…”

“…While satisfying the control accuracy of the system, the system jitter was reduced. The authors of [6,7] combined a sliding mode control with direct torque theory, which improved the dynamic response capability of the system, but it increased the switching gain of the system and strengthened the system chattering. According to [8,9], in order to reduce the buffeting issue, the saturation function took the place of the sign function, the system switching was more stable, and the chattering of the system was reduced, but the sliding mode switching was difficult to achieve, and the anti-interference ability was weakened.…”

Numerical Simulation and Experimental Validation of a Flux Switching Permanent Magnet Memory Machine

“…After the work point changing of low-coercive-force permanent magnet materials, the air-gap flux density of FSPMM machine can be weakened or enhanced, thus the amplitude of back electromotive-force (EMF) waveform, speed, torque density and cogging force can be also changed. In this situation, the FSPMM machine is suitable for the domain of wide speed range and variable torque such as electric vehicle, aeronautics and astronautics, etc [6][7][8][9].…”