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In this paper, a reliable control method is proposed for a position servo system using multiple loops. The position servo system has two minor-loops which are a speed loop and a currentt loop. If one minor feedback loop fails, such as a case of the speed sensor break down, the position servo system becomes unstable. To cope with this problem, the proposed method uses an equivalent transfer function (ETF) as an active redundancy compensation after the loop failure. The ETF is designed so that it does not change the transfer function of the whole system before and after the loop failure. Therefore, the stability of the position control system using this proposed method is guaranteed even if the speed feedback loop fails or the current feedback loop fails. The effectiveness of this proposed method is confirmed by the experimental results.

Speed regulators for motor drives can be classified into four types according to the degree of accuracy and the response time required for a given application. Formulas are presented which can be used to determine the number of bits and the sampling time which are required of a microprocessor for a thyristor drive microprocessor-based speed regulating system. A systematic approach is also proposed which application engineers can use to evaluate and select the most adequate microprocessor from those commercially available for different types of digital speed regulators.

A fully digitalized speed regulator is proposed which executes all regulatory processing by using a multimicroprocessor. The hardware configuration of the regulator is standardized. A vector control algorithm is used to perform fast response speed control of an induction motor. Microprocessors execute a PWM gate pulse generation and current component detection in addition to speed control processing. In applications of the regulator to a 1.5-kW induction motor drive system, Its effectiveness is confirmed.

A new state observer, which is suitable for microprocessor-based motor drives, and its application to suppression control of shaft torsional vibration are described. A distinct feature of the state observer is that a fast-response load torque estimation is obtained by processing the detected motor current and the encoder output pulses by a hardware circuit for each encoder pulse generation. Suppression control of the shaft torsional vibration is achieved by calculating a compensation signal from the estimated load torque with the microprocessor software. A microprocessor-based speed regulator for dc motor drives, which utilizes the state observer and suppression control of the shaft torsional vibration, was developed for evaluation purposes and tested with a 15-kW dc motor. The load torque of the motor can be estimated accurately, even with a 15-Hz vibration frequency, and the torsional vibration can be eliminated with the proposed suppression control.

A new current-control method that is suitable for microprocessor-based speed regulation of motor drives is described. The method achieves fast-response and high-accuracy performance by using a major current loop and an internal current rate loop. The former loop is used to control precisely the mean value of the motor current by employing a current feedback signal obtained from a smoothing filter of the rippled current. The latter loop is used to stabilize the major loop with a high gain and to limit the variation rate of the motor current by employing the current feedback signal obtained from the instantaneous current without time delay. A current controller using a microprocessor was trail-manufactured and tested with a thyristor-converter-driven dc motor. It was found that fast-controlled current response can be obtained, even with a relatively long sampling period.

A method for estimating instantaneous speed, suited for a microprocessor-based speed regulator for motor drives, and the characteristics of the speed control system are described. Features of the proposed method include the estimation of instantaneous speed at a real-time point using values of average speed detected by counting for a certain time the output pulses of an encoder as well as the estimated value as the speed feedback signal for the speed regulator. Since this method allows compensation to be made for the lag time of the feedback signal caused by detection of the mean value, it contributes to improved stability of the speed regulator. In particular, this provides a significant suppression of the vibrations that are generated in motor-driven machinery. >

A new control method is described in which a microprocessor is used to regulate the speed of a dc motor driven by antiparallel-connected three-phase dual thyristor converters. A distinct feature of this speed regulating system is that speed response is improved by using a fast-response current controller for the internal loop. A fast-response current controller is obtained by employing a nonlinear compensation subloop and a proportional plus integral compensation subloop. The nonlinear compensation subloop is used to linearize the nonlinear load characteristics of the thyristor converter, which are encountered under discontinuous conduction states of current. The proportional plus integral compensation subloop reduces the deviation of detected current from the current reference. With these two current-control subloops a fast motor speed response is achieved under discontinuous as well as continuous conduction states; hence the steady-state accuracy of speed is improved. A speed regulator using a microprocessor was trial manufactured and tested with a 20-kW dc motor. It was found that an extremely fast controlled current response can be obtained even with a relatively long sampling period. Further, normal action was confirmed in four-quadrant operation.

A new servo system suitable for robot control is proposed. An optical serial transmission is applied in its servo-control loops to reduce the number of signal cables and the cable length between the robot mechanism and the controlling equipment, as well as to increase flexibility for expanding control functions.

Although many studies of fluidization are available for use in design or operational procedures, the chemical engineering approach does not lead to a true understanding of a fluidized particle system. In this investigation, the nature and properties of a liquid system are used as a basis for deriving equations applicable to a fluidized system. Correlations based on experimental data were found for expansion, viscosity, surface tension, and miscibility. (auth)