An improved self-tuning fuzzy PID controller, which has an ability to compensate for parameter variation, is proposed and applied to the speed control of the indirect vector-controlled induction motor. The controller gains are adjusted on-line using the tuning algorithm based on an artificial neural network (ANN). And a variable learning rate algorithm is proposed to improve the tracking performance while keeping the robustness. Simulation and experimental results confirm that good dynamic performance and high robustness to parameter variation and disturbance can be achieved by means of the proposed controller.
Three dimensional combined process model of electromagnetic field and heat transfer where electrically heated body is moving and forming mechanically is proposed to obtain the reasonable computer calculation time. The proposed method is that calculates the heat transfer by using 2-D section model with referring the joule heat distribution in 3-D electromagnetic field calculation in order to express the moving and forming of the heated body. As a result, we could obtain the calculation result that considered these phenomena in substantially short time in comparison with conventional method.
In recent years, legged robots are progressed and able to walk just like human beings. Hopping has a possibility of moving faster and avoiding larger obstacles than walking. Thus hopping becomes more significant. In this paper, to take account of torque limits of motors, we propose the method of controlling the hopping height by changing the leg length at bottom. Considering an actual environment, the environment will change as the robot moves around. Therefore we describe the way to estimate an actual thrust force. Using the estimated thrust force, command value of leg length in the landing phase is determined. The effectiveness of proposed method is confirmed by simulative and experimental results.
When the position error becomes small, in a conventional positioning system, its motor cannot obtain enough deceleration torque. Hence, the position response becomes slow. There is the other positioning system that is to design the position reference using a trapezoidal speed reference. When the load torque and the final goal position are known, this positioning system has a fine response. However, if the load torque and the final goal vary, its position response cannot have the desired response. In order to overcome these problems, this paper proposes a new high speed positioning system of AC servo motor considering both an unknown friction torque and a windup phenomenon. The proposed system always uses the maximum acceleration, deceleration torque and the maximum speed.
This paper proposes a novel method of suppressing the inrush current of transformers. A small-rated voltage-source PWM converter is connected in series to the transformers through a matching transformer. As the connected PWM converter performs a resistor for the source current, no inrush phenomena occurs. The required-ratings of the PWM converter, which performs the damping resistor for the inrush phenomena, is one-four-hundredth as compared to that of the main transformers in single-phase circuits. In three-phase circuits, it is one-nine-hundredth. The basic principle of the proposed method is discussed. Digital computer simulation is implemented to confirm the validity and excellent practicability of the proposed method using the PSCAD/EMTDC. A prototype experimental-model is constructed and tested. The experimental results demonstrate that the proposed method can perfectly suppress the inrush phenomena.
Switched reluctance type bearingless motors are characterized by integration of switched reluctance motors and magnetic bearings. Therefore, these motors can control radial rotor positions with magnetic force actively. Production of suspension force for rotor shaft magnetic suspension is explained with differential stator windings. In the previous paper, accurate theoretical formulae of instantaneous torque and suspension force generated by one phase excitation were derived from an assumption of simple permeance distribution. From the derived theoretical formulae, it is found that there exist cross coupling between the instantaneous torque and the suspension force. This paper derives a possible output area of the instantaneous torque and the suspension force considering the cross coupling in order to realize a stable operation. It is shown with experimental results that the possible output area of the proposed motors is very accurate in terms of practical application.
This paper describes a vibration control of flexible arm by multiple observer structure using the accelerations of the arm. In general, a flexible arm has several oscillation modes. In case the model of flexible arm can be described as a two-mass resonant system, the reaction torque feedback makes the flexible arm system stable. In the n-mass resonant system, it is known that the reaction torque feedback makes all oscillation modes, only the reaction torque feedback is not enough to make the system stable. The resonance ratio control with the arm disturbance observer has been proposed. The arm disturbance observer is good to suppress the disturbance applied to the tip, but it is not enough to the disturbance applied to other point on the arm. The aim is to make the control system robust against arm inertia variation and disturbance. This paper proposes vibration control of flexible arm by acceleration feedback, and disturbance rejection by multiple observer structure using the accelerations of the arm. The validity of the proposed method is also shown by simulations and experiments.
Aged people and disabled people who have difficulty in walking are increasing. As one of mobility support, significance of a power assisted wheelchair which assists driving force using electric motors and spreads their living areas has been enhanced. However, the increased driving force often causes a dangerous overturn of wheelchair. This paper proposes a novel control method to prevent power assisted wheelchair from overturning. The man-wheelchair system can be regarded as an inverse pendulum model when the front wheels are rising. The center-of-gravity (COG) angle of the model is the most important information directly-linked to overturn. Behavior of the system can be analyzed using phase plane as shown in this paper. The COG angle cannot be directly measured using a sensor, therefore, COG observer based on its velocity is proposed. On the basis of the analysis on phase plane, a novel control method with variable assistance ratio to prevent a dangerous overturn is proposed. The effectiveness of the proposed method is verified by the practical experiments on the flat ground and uphill slope.
This paper presents a consideration on the characteristics of d and q axes parameters of synchronous machines. When parameters of d/q axes equivalent circuits are determined from measured data, some approximations are often used. In this paper, a consideration on the accurate determination of d/q axes equivalent circuit parameters from measured data is presented with considering Canay inductance. This paper also presents a consideration on the effect of Canay inductance on the transient stability. It is well known that Canay inductance has much effects on the transient response of field current. However its effect on the transient stability has scarcely been studied so far. In this paper, simulation studies about transient stability are performed for a model system of synchronous generator with and without considering Canay inductance, and then the effect of Canay inductance on the transient stability is clarified.
Recently hundreds of large dc machines manufactured for steel rolling mills at the high growing period are on the verge of replacement due to insulation deterioration of their armature windings after more than thirty years of service operation. Insulation technologies for aged machine are different from those for new machine, including varnish impregnation technologies. In this paper, experimental study of basic impregnation characteristics for aged dc machine to extend its life is described. Experimental study of application of far infrared radiation for the process is also presented.
This paper describes a zero-power magnetic levitation using magnetostrictive (GMM)/piezoelectric (PZT) laminate devices. This magnetic force control is based on the inverse magnetostrictive effect of magnetostrictive material, where magnetization of GMM hence a magnetic force is control by the applied voltage to PZT. Because PZT is considered electrically capacitive in steady state, no electric energy is required to maintain constant magnetic force. We conducted a magnetic levitation using a magnetic force control device with there laminations of GMM and PZT. Zero-power consumption of the levitation system in keeping a constant gap was confirmed by the measurement of the input current to PZT.
In this paper, we propose flexible shoe system to apply passive walking manner to ordinary humanoid biped. In this system, 2DOF (FF & FB) control scheme is used and realize walking with less ankle torque. The effectiveness is confirmed by computer simulation and experimental result, so we call this system as “energy saving shoes".