DC motor drive systems are still widely used in many industrial applications because of their simpler controllers compared with AC motor systems. To realize the desired control performances, system parameters are important for modeling and analysis. Usually, some parameters of a motor are given by manufactures, and others can be measured or calculated by users. But from the standpoint of the entire systems, it is hard to measure the parameters collectively. Especially, since carbon brushes are used in DC motors, their contact resistance and voltage drop vary depending on running condition. In this paper, we propose a parameter estimation method on the basis of the theory of least mean square method. In this method, we use a model of DC motor which takes account of the voltage drop, and introduce block pulse functions which is one of the ways to approximate function as a linear combination of a set of orthogonal basis functions. The parameters of the entire system can be estimated on-line. We use a Transputer to realize on-line estimation. Experimental results shows the validity of the estimation method.

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The vector control of an induction motor is classified into direct and indirect types. Indirect vector control (slip frequency controlled type) is usually used because of its simplicity and superior characteristic at low speed operation. A defect of this type is sensitive influences by thermal variations of the secondary resistance. In order to improve the robustness against the parameter change, a flux observer based direct vector control has been proposed in the literature. In this paper, a flux observer based indirect vector control is proposed and the stability of the system is investigated.
At first, a flux observer based direct vector control is constructed by using a controlled current source. By considering the observer in a fixed co-ordinate system located on its secondary flux, an indirect type is presented. An observer gain matrix which is invariable according to the co-ordinate transformation is derived. The poles of the observer and those of the observer based vector control system are calculated analytically by neglecting the machine parameter change. Furthermore, a linear model of the observer based vector control system is proposed by taking into account the change of primary and secondary resistances. By using this model, the trajectories of the poles and zeros of the torque transfer function are computed and discussed.

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Slip frequency vector control is generally used for variable speed induction motor drives, due to its excellent response characteristics. It is however sensitive to the variation of motor parameters since the flux current and slip frequency commnands are computed using the motor parameters. As a result, the system performance will be degraded if the controller parameters do not match the motor parameters.
The authors propose a new approach of vector control in which quick responses and system robustness are concurrently obtained by the learning capabilities of neural network. In the newly developed method, controller parameters are learned in real-time at medium and high speeds. Using these learned parameters, the low speed performance of the controller can also be greatly improved.
This paper describes the theoretical analysis, simulation and experimental results of the proposed method.

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Recently, with the progress of robust control techniques, the resonance of mechanical systems becomes a more important problem. This paper presents a position control method to suppress the torsional vibration of a 2 mass resonant system. Here we propose a sensorless control of arm portion. In this case, it is necessary to estimate some states of the arm portion. When motor portion parameters are well known due to several identifications, the reaction torque caused by the shaft torsion can be estimated. This reaction torque feedback makes it possible to control the resonance frequency between the torque current and the motor position. Here, we introduce a new concept which is called “Resonance Ratio”. The resonance ratio is determined arbitrarily by the feedback of the reaction torque. The proposed method is a reasonable concept from a mechanical point of view.
The proposed control system is based on both the conventional PD control and the resonance ratio control. Then any sensor information of the arm portion is not used, and the proposed controller is a very simple structure. This is one of the remarkable points of the proposed method. We discuss an idea of the determination method of controller gains. The validity of the proposed method is also proved by several experiments.

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We have developed a new precision tension control system which can suppress the head-impact and transient tension alternation. This system is suitable for home-use digital VCRs which require thin tape to run stably.
In this system, a moving tape guide actuator is installed at the entrance side of a rotary drum, serves as a tension detector and a tension control actuator.
This moving tape guide actuator consists of a swing arm type voice-coil motor and a movable pin which stays in contact with the tape.
The tension control system which employs the tension detector based on the modern control theory (detection range: 1kHz) achieved the wide control band (170Hz).

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Various types of linear motor have been developed. However, most of them are only applied to positioning control. High compliance property of the linear motor has not been used effectively. Then there are few types of linear motor which can be applied to manufacturing unit.
In this study, we developed a differential linear motor which has some advantages suitable for manufacturing unit. The new type of the linear motor has been expected to be applied not only to positioning unit but also to active compliance unit of robot manipulators. Therefore, we applied pseudo diagonalization method to the position and compliance control of the developed differential linear motor. In the position control part dither signal was used after diagonalization. Amplitude of the dither signal was modified by error signals. In the compliance control part PID controller was used. The effectiveness of the proposed control system was shown through experiments.

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Pneumatic actuators are less expensive and have higher power/weight ratio than other types of actuators. On the other hand, it is very difficult to control the pneumatic actuators because of uncertainties caused by the nonlinear pneumatic circuit and large friction caused by mechanical contact between piston-ring and cylinder. Then the pneumatic actuator has hardly applied to precise positioning and smooth drive control.
In this paper we applied optimal control theory and model feedback control scheme to control of the pneumatic cylinder in order to realize both the precise positioning and the smooth driving. The effectiveness of the proposed control system is shown through experiments. Results of these experiments are compared with the results which were carried out by fuzzy control logic.

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It is well known that the direct drive systems not to use the reduction gears with the clearane and backlash are required for the highly precise position control, whose motor must have high torque at very low speed. The authors have developed a new motor for this purpose and named PM vernier motor.
In this paper, it is explained at first what is PM vernier motor, the construction and principle, and then the theory able to calculate the torque and how to control its speed are described. It is also shown that the calculated values of torque were agreed well with the experimental results.

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This paper describes low torque pulsation and high power control of parmanent magnet synchro-nous motor (PM motor) with distorted electromotive force (emf).
The experimental model of PM motor is 40kW, 190r/min, salient-pole, six-phase machine. An individual single-phase transistor inverter is connected to each phase of PM motor as a power source. By adopting full pitch and concentrated winding in the armature of the motor, the rate of flux utilization and output torque per mass can be increased. This winding causes trapezoidal distortion in the phase voltage waveform at no load. For realization of high peformance control of PM motor, the current waveform should be determined so as to minimize torque pulsation and maximize the output torque of the motor under the rated current.
This paper proposes the method to determine the optimum current waveform. The currents and emf's are expressed as N-dimensional vectors (N: the number of phase). Due to the characteristics of the paticular structure of the motor, the armature reaction is small enough to be neglected. In this case, the optimum current vector can be derived under two conditions; (1) the direction of the current vector always agrees with that of the emf vector, and (2) the scalar product of the two vectors is held constant. Supplying the optimum current vector provides no torque pulsation and the nearly maximum output torque under the rated current. This method also can derive the new optimum current corresponding to open-phase operation.
Validity of the method is experimentally confirmed. The characteristics of the experimental model of PM motor is also described in this paper.

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In this paper, the authors propose a current control system of a single-phase PWM AC/DC converter which eliminates detectors of the source phase angle and voltage. The sinusoidal input current and unity effective power factor are realized based on the estimated source voltage in the controller. The feature of the proposed estimation algorithm is that the estimations of the phase angle and crest value of the source voltage are independent each to each. The estimations are performed based on the current error between the actual and model currents. The orthogonal and in-phase components of the current error with respect to the estimated phase angle are proportional to the phase angle and crest value errors, respectively. Therefore, the estimations of them can be realized by feeding back the corresponding components of the current error.
The effectiveness of the proposed current control system was confirmed by experiments. The stable estimation and control were achieved.

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In this paper, an analysis of switching and conduction losses in hysteresis current-controlled inverters is presented. The switching frequency variation which is important in switching loss evaluation is first analyzed considering the voltage drop across the load impedance in series with the load counter emf. Based on this analysis, the expression for the switching losses is derived. As for the conduction losses, a concept of probabilities of the transistors receiving ON and OFF signals is introduced to calculate them since the switching instants of the power devices can not be predetermined. Experimental results are included to verify the proposed method.

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