Shinji Doki

Sensorless estimation of rotor position of cylindrical brushless DC motors using eddy current

A rotor position estimation of a cylindrical brushless DC motor at a standstill has been difficult, and the realization has been desired. This paper proposes a simple processing of a rotor by pasting non-magnetic materials where eddy currents can flow on the rotor surface. This process causes a change of amplitude of the phase current according to the rotor position. The experimental results show that the rotor position estimation with maximum error of 26/spl deg/ electrical angle has been realized, which is useful for 120/spl deg/ conduction type cylindrical brushless DC motors.

Suppression of harmonic current in vector control for IPMSM by utilizing repetitive control

Generally, PMSM is driven by the vector control system based on the current control. However, in spite of using the vector control, there are harmonic components in the current control loop of vector control system due to several causes. Authors have proposed the suppression control method of harmonic current in the vector control system for IPMSM using the repetitive control with Fourier Transform. The proposed control method, however, was carried out individually for each harmonic current component with Fourier Transform and phase adjustment of compensational signals to stabilize the system, so that the process of learning compensation signal was complicated and required much calculation time on the DSP. In this paper, we propose a new control method suppressing all harmonic current components simultaneously without Fourier Transform and phase adjustment of compensational signal. So, the process of learning compensation signal and suppression harmonic currents becomes very simple and fast. The stability analysis shows that the new proposed control method keeps stability for all frequency domains. Experimental results are shown to confirm the effectiveness.

Position and velocity sensorless control of SynRMs using on-line parameter identification

This paper presents a novel on-line parameter identification system for position sensorless control of synchronous reluctance motors (SynRMs). The proposed identification system can identify motor parameters in position sensorless control. Therefore, there is no necessity of complicated measurements of motor parameters in advance. Under position sensorless control, since the mathematical model includes the position and velocity whose actual value is unknown, the estimated position and velocity are substituted for them. As a result, there is a possibility that identified parameters can be affected by the position and velocity estimation error. However, since the proposed system cancels position and velocity terms, identified parameters are not affected by them. The position sensorless control using identified motor parameters is realized, and the effectiveness of proposed system is verified by experimental results.

Sensorless control of synchronous reluctance motors based on an extended EMF model and initial position estimation

In this paper, we realize a sensorless control of synchronous reluctance motors based on a proposed extended EMF model. This proposed model can be used for all synchronous motors, so the estimation method applied for permanent magnet synchronous motors can be applied for synchronous reluctance motors without modification. At standstill state, since an amplitude of the extended EMF becomes zero, it is difficult to realize position estimation based on the extended EMF. In order to solve this problem, a system identification method for sensorless control is combined with it. Sensorless control of synchronous reluctance motors can be realized from standstill state to high-speed ranges by a combination of two methods.

Compensation method of stator iron loss of vector controlled induction motor using robust flux observer

A vector control system of an induction motor is proposed to suppress influence of iron loss. It is pointed out that the rotor flux estimator contributes more to torque control linearity than the current controller. Therefore, it is proposed that a rotor flux observer which can suppress the influence of some parameter deviations, (especially that of rotor resistance), can be applied to decrease the sensitivity to iron loss resistance. Finally, some experimental results of improved torque control linearity are shown to verify effectiveness of the proposed system.

Improvement of IPMSM sensorless control performance by suppression of harmonics on the vector control using Fourier transform and repetitive control

In the case of the sensorless control for the PMSM that estimates position and velocity from EMF using the model of a synchronous motor with the voltage and current, it is desirable for the voltage and current to be perfect sine waves. However, in fact, various harmonic components are contained in the voltage and current, and they have bad influence on the estimation performance of a sensorless control. In this paper, we propose an improving method of sensorless control performance for the IPMSM by suppression of harmonic component in the current control loop of the vector control using Fourier transform and repetitive control. To suppress harmonic components, compensation signals are acquired using Fourier transform and repetitive control, and feedforward control is implemented with acquired compensation signals. To evaluate our proposed system, the sensorless control system for the IPMSM is taken for instance. The system is constructed on the basis of the extended EMF disturbance observer with the current and voltage command whose harmonic components are suppressed. As a result, we can have a margin in pole assignment of the disturbance observer, and the performance of sensorless control can be improved. The effectiveness of the proposed method is confirmed by experimental results.

Harmonics suppression of PMSM using repetitive control and application to improvement of sensorless control performance

Using the repetitive control, Authors have proposed the suppression method of harmonic currents in the vector control system for PMSM. In this paper, we propose a new simplified harmonics suppression system and a method improving the stability margin of the control system and convergence speed of harmonics. With stability analysis and experimental results, we confirm the proposed method. Moreover, this paper shows that the proposed control system can be used for improvement of position/velocity sensorless control performance with voltage commands and currents that are purified by the repetitive control. To evaluate our proposed system, the sensorless control system which is constructed on the basis of the extended EMF disturbance observer is taken as an example, and the improvement effectiveness of the proposed control system is confirmed by experimental results.

Autonomous Motion Adaptation Against Structure Changes Without Model Identification

It is expected that humanoid robots provide various services to help human daily life such as household works, home security, medical care, welfare and so on(Dominey et al., 2007; Okada et al., 2003; 2005). In order to provide various services, humanoids have multi degree-of-freedom(DOF), sophisticated and complicated structure. These humanoid robots will work under human living environments which are not definable beforehand. So humanoids have to provide their given services under not only the designed environments but also unknown environments. Under unknown environments, robots cannot perform as planned, and they may fall or collide with obstacles. These impacts will wreak several unexpected structure changes such as gear cracks, joint locking, frame distortions and so on. Because of the designed motions are optimized to the robot structure, if the robot structure has changed, the services from robots cannot be provided. Because general users have no expertise knowledge of robots, thus, quick repairs under human living environments cannot be expected. Even in that case, it is expected that the robots should provide services to help human daily life as possible. In the case the humanoid robots cannot get rapid repair service, they have to provide the desired services with their broken body. In addition, using tools to provide some services can be considered as one of the structure changes. Therefore, it is necessary for future humanoids to obtain new motions which can provide the required services with changed structure. We propose an autonomous motion adaptation method which can be applied to sophisticated and complicated robots represented by humanoids. As a first step, we deal with the simple services based on trajectory control; services can be provided by following the correct path designed by experts. When robot structure has changed, achieving the designed trajectories on changed structure is needed. As the conventional methods, there are two typical approaches. One is the method based on model identification (El-Salam et al., 2005; Groom et al., 1999). Robots locate the occurred changes, identify the changed structure, recalculate inverse kinematics, and then obtain the proper motions. If the changed structure is identified, inverse kinematics leads the proper motions for new properties of changed structure. However, it is so difficult to identify the complicated structure changes in sophisticated robots. In additions, the available solving methods of inverse kinematics for multi DOF robots is non-existent according to the reference (The Robotics Society of Japan, 2005). So model identification method cannot be applied for humanoids. Another approach is Autonomous Motion Adaptation Against Structure Changes Without Model Identification 2