Yoshiyasu Takase

Development of stator-magnetless linear synchronous motor for sensorless control

Sensorless control technique is desired in applications of a long stroke linear synchronous motor (LSM) without using a linear scale. This paper discusses the development of a stator-magnetless LSM (no magnet mounted on the stator of LSM) for sensorless control technique that includes a high speed position estimation algorithm based on magnetic hysteresis phenomenon. This paper presents the new structure of a flux-switching LSM to achieve a high saliency ratio by designing a cutout which causes magnetic saturation in the armature core. The effect of sub-teeth to reduce cogging thrust is also presented. Furthermore, this paper also reports the analytical and experimental characteristics of inductance, thrust, cogging thrust, and sensorless control drive using a prototype.

Step climbing control of wheeled robot based on slip ratio taking account of work load shift by anti-dive force of suspensions and accerelation

This paper proposes a method which enables wheeled robot to climb a step that is higher than the radius of the wheel. In conventional method, the velocity at the moment of impact and impact force must be increased in order to climb the step, which causes troubles of wheeled robot. This paper proposes a method utilizing variable loads arised by changing speed and anti-dive force from suspension to climb the step more safely. Effectiveness of the proposed method is verified by simulations and experiments.

Development of a Stator-Magnetless Linear Synchronous Motor for Sensorless Control

Sensorless control technique is desired in applications of a long stroke linear synchronous motor (LSM) without using a linear scale. This paper discusses the development of a stator-magnetless LSM (no magnet mounted on the stator of LSM) for sensorless control technique that includes a high speed position estimation algorithm based on magnetic hysteresis phenomenon. This paper presents the new structure of a flux-switching LSM to achieve a high saliency ratio by designing a cutout which causes magnetic saturation in the armature core. The effect of sub-teeth to reduce cogging thrust is also presented. Furthermore, this paper also reports the analytical and experimental characteristics of inductance, thrust, cogging thrust, and sensorless control drive using a prototype.

Position sensorless control with accelerometer for linear and curvilinear synchronous motor

In the field of the manufacturing industry, it has been often discussed that high-mix low-volume manufacturing is required to meet a variety of customer needs. In such a situation, cellular manufacturing and U shaped production lines are often adopted. Linear synchronous motors (LSMs) are appropriate to realize U shaped automation lines because of its strong features such as flexibility of layout, high efficiency and position control performance. However, a problem seems to lie in the fact that LSMs need a position sensor which is expensive and has less durability. For this reason, the position sensorless control for LSMs is required. In addition, the method should be easy to apply to all kinds of LSMs. Specifically, the method should require no saliency and be apply to a LSM which has a complex track including curvilinear section. Based on such a background, this paper presents a position estimation method for a Linear and Curvilinear Synchronous Motor with an accelerometer which is inexpensive and easy to attach to LSMs. As the proposed method in this paper does not require any motor saliency, it can be quickly applied to all LSMs. In this paper, the proposed method is shown and verified by experimental results.

Proposal of position sensorless control and torque ripple compensation based on torque sensor feedback

This paper presents the following two methods based on torque sensor feedback: new position sensorless control method for surface-mounted permanent magnet synchronous machines (SPMSMs) and torque ripple compensation. The position sensorless techniques can be classified into two categories: the techniques based on the back electromotive force (back-EMF) and the techniques based on the high frequency injection (HFI). However, in general, the former category is weak in low speed, and the later one can not drive without the saliency. Furthermore, both of the categories have a problem that torque ripples are caused by transient position estimation errors. Meanwhile, in the field of robot research in recent years, the developments of torque sensors are active. This situation has suggested that small and reasonable torque sensors will be available in the foreseeable future. Therefore, we developed the torque sensor which can be attached to SPMSMs and the new position sensorless control method based on the torque sensor feedback. Using the proposed method, the position sensorlesss drive corresponding to the entire speed range including zero is achieved. Moreover, this method is applicable to SPMSMs which do not have saliency. In addition, the torque ripples are well suppressed. Effectiveness of the proposed method is verified by experimental results.

Proposal of step climbing of wheeled robot using slip ratio control

This paper proposes a method which enables wheeled robot to climb a step that is higher than the radius of the wheel. In conventional method, this is impossible, because driving force of front wheel is not enough. This paper proposes a method utilizing the moment of impact between the wheel and the step to maximize the normal force, and hence the driving force of the front wheel. Effectiveness of the proposed method is verified by simulations and experiments.

Robust active damping technique for three-phase PWM converter connected to power grid with unknown inductance

The PWM converter includes a low-pass filter in order to remove the high-frequency current that flows to the power grid. The low-pass filter is composed of two reactors and a capacitor (LCL-filter). The LCL-filter is the gain characteristic that attenuates by the high frequency band, and can eliminate the career ripple of the current. However, LCL-filter has a strong resonance characteristic. When the power grid current resonates with a high frequency, the equipments connected to the same power grid are harmfully affected. In order to control this resonance, passive damping and active damping are used. However, both methods suffer from several problems. A passive damping is a method of controlling the resonance by the damping resistance. The generation of heat by the loss of resistance becomes a problem often. The active damping is a control technology that controls the resonance without using the damping resistance. The active damping has both of the sensor method and the sensor-less method. The active damping methods with sensor require the use of an additional sensor. When active damping is used without a sensor, it becomes more sensitive to the power grids inductance changes. Especially, in the case of an extreme increase in the power grids inductance, problems with LCL resonance and ACR deterioration occur. When the ACR response is deteriorated, the power grid is affected by low frequency oscillation, making the power supply unstable. All equipment connected to this power grid is harmfully affected. There are few examples of low frequency oscillation in conventional active damping technologies. It is possible to control the resonance of the LCL-filter with the control approach proposed in this paper. Also, the deterioration in the current loops response can be prevented, even if the power grids inductance increases. And, thus, low frequency disturbances can be prevented. The proposed control method is achieved with tuning-less corresponding to the power grids inductance.