Keywords: maximum torque-per-ampere control, position sensorless vector control, permanent magnet synchronous motor, extended electromotive force This paper discusses a novel position sensorless vector control for permanent magnet synchronous motors. In this paper, we define a novel coordinate frame (hereafter, the maximum torque control frame), one axis of which is aligned with the current vector of the maximum torque-per-ampere (MTPA) control, and propose a sensorless control method for directly estimating the maximum torque control frame. In the conventional MTPA control method, the motor is operated with a current while the control frame (d-q frame) is estimated. The proposed method is robust against changes of motor parameter. In addition, the MTPA control is easily achieved. Fig. 1 illustrates the frames used in this paper. The estimated axes we propose are defined as the maximum torque control frame of dm-and qm-axes. The extended EMF model on the maximum torque control frame is represented in (1), and the second term on the right-hand side is defined as an extended EMF on the frame.where Therefore, the maximum torque control frame is estimated directly with this L qm . The MTPA control can be achieved with the control signal in the form of the γ-axis current (dm-axis current) remaining zero without considering the use of the reluctance torque. Fig. 2 shows L q and L qm against the q-axis current for the motor examined in consideration of magnetic saturation. The q-axis inductance L q was affected by magnetic saturation and markedly decreased with increasing q-axis current. On the other hand, the estimation parameter L qm did not change substantially. This indicated that the use of L qm , rather than the conventional L q , greatly reduces the effect of magnetic saturation on the position estimation. The reason is that L qm is less affected by the magnetic saturation caused by an increase in the q-axis current. Fig. 3 shows a current vector locus in the MTPA control and that in the proposed method, assuming L qm to be constant, when the magnetic saturation is considered. Excellent current vector loci are observed even when L qm is approximated by a constant value. Therefore the motor can be controlled thoroughly with almost MTPA control.

No abstract

A digital control system for a magnetic suspension device made as an experimental and demonstrative device for undergraduate students is described. Hardware and software of the control system are presented. Experimental results obtained in the application of three kinds of modern control algorithm are presented.

No abstract

Recently, the sinusoidal drive of a permanent magnet synchronous motor has been actively researched because of its low noise and low vibration. Moreover, the sinusoidal drive system which uses only a lowresolution position sensor without utilizing the current sensor is researched. This paper proposes the method for deciding the lead angle of the impressed voltage by an easy expression for current sensor-less sinusoidal drive system of a permanent magnet synchronous motor with a low-resolution position sensor. The method is a technique for indirectly controlling the current phase without the dq axis transformation. First, the control method of adjusting the current of d axis to almost 0 and the control method of the weakening magnetic flux were shown. And, the methods were examined in numerical analyses. Next, the effectiveness of the proposed phase control method was verified using an actual motor. In the control method of adjusting the d-axis current to almost 0, the locus of the current vector was confirmed and an excellent transient response for controlling the current of d axis was obtained. Moreover, it was confirmed that the increase of applied voltage was controlled and the range of the drive had expanded in the method of the flux-weakening control.