佐藤 孝雄

For the next generation of manufacturing, represented by Industrie 4.0, a multi-input controller is designed directly from controlled data, without using the mathematical plant model, where the ratio between the D/A conversion of multiple inputs and the A/D conversion of a single output is non-uniquely. With the proposed method, the fixed-structured controller is optimally designed by solving a model reference problem using one-shot data. Furthermore, to eliminate inter-sample ripples emerged by input oscillation, the deviation of the control inputs is also evaluated using the proposed method. As a result, a non-ripple data-driven controller is achieved. Numerical examples show that the proposed multi-rate data-driven method is superior than the conventional single-rate method.

A new data-driven model-reference robust Proportional-Integral-Derivative (PID) control is proposed for a regulator system. In the proposed method, the PID parameters are decided such that a prescribed robust stability is achieved. Furthermore, the disturbance rejection performance is optimized. Since the proposed method is designed as a model reference problem, where the reference model and the controller parameters are optimized, trade-off design between robust stability and regulator performance is achieved by selecting the prescribed robust stability. Finally, the effectiveness of the proposed method is demonstrated through numerical examples.

In this study, a data-driven design method is proposed for a dual-rate system, where the sampling interval of a plant output is restricted and is an integer multiple of the holding interval of a control input. In our proposed method, single-rate virtual reference feedback tuning (S-VRFT), where the holding interval is the same as the sampling interval, is extended to the dual-rate virtual reference feedback tuning (D-VRFT) system. In D-VRFT, a controller is decided using a set of input/output data used in S-VRFT, and it is easy to extend S-VRFT to D-VRFT and implement D-VRFT. In this study, intersample oscillations caused in such a dual-rate control system is prevented because a weighting filter is introduced for penalizing the control input deviation between the sampling instants. The filter is designed as an integrator for weighting the low-frequency domain. The improvement in fast-tracking performance as well as the ripple-free property are demonstrated through both the numerical and experimental results.

The dual-rate control system, in which the sampling interval is an integer multiple of the holding interval, is designed using the null-space of the steady-state characteristic of the controlled plant. In the proposed method, a dual-rate control law is extended independent of the steady-state discrete-time output response. As a result, the intersample ripples caused by the input oscillation are eliminated by reallocating the control input. The proposed method based on the steady-state characteristic is a simple strategy compared with conventional methods based on the dynamic characteristic. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

The present study discusses the design method for controlling a single-input/single-output linear time-invariant dual-rate system, where the sampling interval of the plant output is longer than the holding interval of the control input. In such a dual-rate system, the intersample output might oscillate even when the sampled output converges to the reference input in the steady state. In a conventional ripple-free method, an existing control law is extended by introducing an exogenous variable, which is independent of the discrete-time sampled response, and the exogenous variable is designed for eliminating the steady-state intersample ripples without changing the existing sampled response. In another method, since a control law is designed such that the intersample performance is optimized, the intersample ripples are eliminated in the transient as well as steady states. However, the preservation of an existing sampled response is not taken into account. The present study proposes a new design method for eliminating the intersample ripples subject to the existing sampled response. In the proposed method, the continuous-time index is optimized subject to the existing discrete-time response. As a result, the intersample ripples are eliminated in the transient as well as steady states, and the existing discrete-time sampled response is maintained. The proposed method is compared to the conventional dual-rate design methods in numerical examples, and the effectiveness of the method is demonstrated.

This study proposes a data-driven approach for controlling a dual-rate sampled-data system using the lifting technique, where the sampling interval of the plant output is longer than the holding interval of the control input. In the proposed method, the structure of the dual-rate controller is linearized to its controller parameter, and the controller parameter is optimized using noniterative correlation-based tuning. Furthermore, intersample ripples are eliminated because the difference in the control inputs between sampled outputs is weighted. The effectiveness of the proposed method is demonstrated through numerical and experimental examples.

A dual-rate sampled-data control system is designed in which the sampling interval of measured signals is twice as long as the holding interval of a control input. In the proposed method, a control law is extended based on the null space and intersample ripples are eliminated without changing the sampled output trajectory in the steady state. Polynomial and state-space approaches are conventional open-loop design methods based on the null space. However, conventional methods are ineffective for unstable systems and are unavailable when the null space of the plant model is only the zero vector because the controlled plant is not arbitrarily selectable. On the other hand, the proposed method is effective for unstable systems, as well as stable systems, even when the null space of the plant model is only the zero vector, because the proposed controller is designed based on a closed-loop system.

Depending on the load requirement, active vibration isolation table may equip with redundant actuators. For such the table, it may be difficult to isolate the faulty actuator due to the redundancy. This paper presents a design of active fault diagnosis for the redundant driven active vibration isolation tables. The simulation results show the effectiveness of the proposed active fault diagnosis system by comparing to the conventional passive fault diagnosis method.

The aim of the present study is to improve the understanding of the control engineering for university students through the experience of the control experiment, and hence an experimental device is developed. The students are educated the control engineering using the device, and the educational effect is evaluated. In the present study, the students take examinations for the control engineering before and after the experiment, and the effect is evaluated objectively.

In the design of simple adaptive control (SAC) using almost strictly positive real (ASPR), the feedback control system is stabilized by the output feedback with a high gain. Although ASPR is not, however, generally satisfied, it is achieved by introducing a parallel feedforward compensator (PFC). When SAC is designed for the augmented system which consists of an actual plant and PFC, not the actual plant output but the augmented system output converges to the reference input because of the influence of PFC. To resolve the problem, an extension method of the conventional SAC is proposed. In the proposed method, based on the null-space of an augmented plant, an exogenous input, which is independent of the augmented system output, is newly introduced. Because the exogenous input is designed so that PFC output is to be 0, the actual plant output is the same as the augmented system output in the steady state, and as a result, the actual plant output converges to the reference input. From a practical application point of view, the proposed method can easily improve the control performance of the conventional SAC with a PFC. In the proposed method, an exogenous input generated as the feedback signal of PFC output is only added to the conventional SAC control input. Therefore, the proposed method can be applied to various field in which the SAC method has been implemented, e.g., process control, mechanical systems, power systems, robotics, and others. In the present study, the effectiveness of the proposed method is also demonstrated through experiments for a motor control.

A new approach to the active fault diagnosis (AFD) for input redundant plants is presented in this paper. A test signal which helps the diagnosis is injected to the plant in addition to nominal control input in the AFD typically. One feature of the proposed AFD is adaptive allocation of the test signal. The adaptive allocator which distributes the test signal and injects it to the redundant actuators is introduced in this paper. A fault-diagnosis (FD) system that estimates fault location and its magnitude from adaptive parameter of the adaptive allocator is constructed with a simple neural network (NN) model. Furthermore, a A fault-tolerant adaptive control system which includes the adaptive test signal allocator is designed based on the model reference adaptive control (MRAC) technique. The adaptive laws of the adaptive allocator and controller are derived by using a suitable Lyapunov function. By performing experiments using a two-input redundant plant, we show the effectiveness and applicability of the proposed AFD and MRAC system.

The present study discusses the consensus control of dual-rate multi-agent systems, where the sampling/communication interval of quantized data is an integer multiple of the control interval. A conventional multi-agent system uses a dynamic quantizer which is designed in a single-rate system where the intervals are equal, i.e., the control interval length is the same as the communication interval length. However, a dynamic quantizer designed in a dual-rate system is expected to have improved control performance. In the present study, an objective function is divided into a quantization term, which is related to the quantization error, and the remaining term. The proposed dual-rate dynamic quantizer is designed such that the quantization term is minimized. Finally, in numerical examples, the proposed dual-rate method is quantitatively evaluated by comparing with the conventional single-rate method, and the effectiveness of the proposed method is demonstrated.

This paper proposes a method for determining a high accuracy posture for serial redundant manipulators with parametric uncertainty that suppresses the effect of the uncertainty. In the proposed method, the uncertainty variance is introduced as an index for quantifying the magnitude of the distribution of the end-effector coordinates of the manipulator caused by the uncertainty, and the posture is determined by using the uncertainty variance as an evaluation function of posture. In order to efficiently calculate the uncertainty variance, the method includes a calculation method based on the polynomial chaos theory. The effectiveness of the method is confirmed by a posture determination simulation of a serial redundant manipulator with uncertainty. In this simulation, it is confirmed that the calculation of the uncertainty variance can be achieved by the method using the polynomial chaos theory, and that the proposed method can determine the high-accuracy posture that suppresses the effect of the uncertainty.

The properties of most real systems vary every moment. For such systems, performance-adaptive control systems, which assess current control performance and tune their controller based on the assessment, are effective. This paper proposes a one-parameter tuning method as one of design methods of the performance-adaptive control systems. When the current control performance is diagnosed as being poor, the conventional performance-adaptive control systems redesign their controllers using the results of system re-identification. However, the system has a risk that the redesigned controller may cause further deterioration of the control performance depending on the identification accuracy of the estimated parameters. In the proposed method, the controller has a unique user-specified adjustable parameter. The controller can improve the control performance by adjusting only the parameter. However, only if the desired control performance cannot be maintained by adjusting the parameter because of drastic changes in the controlled object, the control system redesigns the controller using the estimated system parameters. Thanks to this strategy, the number of controller redesigns using the estimated system parameters is decreased when compared to the conventional performance-adaptive control system. It can also reduce the risk of further deterioration of the control performance because of the controller redesign. The effectiveness of the proposed method is evaluated by simulations and application to a weigh feeder that is one of food process systems.

<p>In this paper, we propose a null-space compensation control for linear first-order systems with redundant two input channels. In the input redundant systems, control input vector generally has null-space component of the plant parameter vector. The null-space component does not contribute to the generation of the control force which drives the plant state. If a control input that does not include the null-space component can be generated, efficient control is achieved from the viewpoint of minimizing the norm of the control input. In the proposed method, an adaptive control method is used to design a control system that compensates for the null-space component, even if the plant parameter vector is unknown. The effectiveness is shown by numerical examples.</p>

The present study discusses an optimal design method of a proportional integral derivative (PID) control system for a continuous-time second-order plus dead-time system (SOPDT) that includes an under-damping system. The proposed PID control system is designed to minimize the performance index defined as the tracking performance for the set-point or the regulation performance for the disturbance, where the assigned stability margin is also achieved in order to attain robust stability for the modeling error. Because of the relationship between tracking performance and robust stability, the PID parameters are decided such that the tracking performance is optimized subject to the user-specified stability margin. In the proposed design method, in order to obtain the most general optimal PID possible parameters for controlled plants, we discuss a design method based on a normalized plant model. As a result, the PID parameters are seamlessly optimized between over-damping, critical-damping, and under-damping systems. The effectiveness of the proposed method is demonstrated through numerical examples.

The present paper discusses a design method for a single-input single-output linear time-invariant dual-rate sampled-data control system, where the sampling interval of a plant output is longer than the holding interval of a control input. In such a control system, intersample output oscillation, called ripple, can occur even if the sampled output converges to the reference input. In order to resolve this problem, two design methods have been proposed such that the existing sampled output response is maintained: an open-loop system design method and a closed-loop system design method. However, the open-loop design method cannot be applied to systems for which the gain matrix of the control input is full rank. On the other hand, the closed-loop design method can be used for such systems, but the sampled output response is maintained only in the steady state. The present study proposes a new closed-loop design method in which ripples are eliminated and both the transient and steady-state responses are maintained. The effectiveness of the proposed method is demonstrated through numerical examples. © 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Solving the inverse kinematics of redundant manipulators is difficult, because knowledge of the manipulators and their evaluation functions is required. To solve this problem, we propose a novel method of enabling a neural network model to learn the inverse kinematics. The method achieves learning independent of the structure of the evaluation function, by combining multiple neural network models. The method can obtain the neural network models of the inverse kinematics via an automatic calculation process using only training data, which consist of the postures, end-points, and evaluation values. In this paper, the algorithm used by the method and its background is explained, and the effectiveness of the method is validated by a numerical simulation.

In this paper, we consider the consensus control of multiagent systems with quantized signal communication. In such a network system, when the static quantizer is used, the control performance is degraded because of the influence of the quantization error. To compensate the quantization error, in a conventional method, a probabilistic quantizer is used. On the other hand, in this paper, the dynamic quantizer is introduced instead of the static quantizer. Because the dynamic quantizer is optimally designed, the control performance of the proposed method can be improved better than the conventional methods. Finally, the effectiveness of the proposed method is demonstrated through numerical examples.

The present study proposes a novel proportional-integral-derivative (PID) control design method in discrete time. In the proposed method, a PID controller is designed for first-order plus dead-time (FOPDT) systems so that the prescribed robust stability is accomplished. Furthermore, based on the control performance, the relationship between the servo performance and the regulator performance is a trade-off relationship, and hence, these items are not simultaneously optimized. Therefore, the proposed method provides an optimal design method of the PID parameters for optimizing the reference tracking and disturbance rejection performances, respectively. Even though such a trade-off design method is being actively researched for continuous time, few studies have examined such a method for discrete time. In conventional discrete time methods, the robust stability is not directly prescribed or available systems are restricted to systems for which the dead-time in the continuous time model is an integer multiple of the sampling interval. On the other hand, in the proposed method, even when a discrete time zero is included in the controlled plant, the optimal PID parameters are obtained. In the present study, as well as the other plant parameters, a zero in the FOPDT system is newly normalized, and then, a universal design method is obtained for the FOPDT system with the zero. Finally, the effectiveness of the proposed method is demonstrated through numerical examples.

The present study proposes a new design method for a proportional-integral-derivative (PID) control system for first-order plus dead-time (FOPDT) and over-damped second-order plus dead-time (SOPDT) systems. What is presented is an optimal PID tuning constrained to robust stability. The optimal tuning is defined for each one of the two operation modes the control system may operate in: servo (reference tracking) and regulation (disturbance rejection). The optimization problem is stated for a normalized second-order plant that unifies FOPDT and SOPDT process models. Different robustness levels are considered and for each one of them, the set of optimal controller parameters is obtained. In a second step, suitable formulas are found that provide continuous values for the controller parameters. Finally, the effectiveness of the proposed method is confirmed through numerical examples.

We propose a new data-driven method for a single-input multi-output dual-rate system, in which the sampling interval of plant outputs is an integer multiple of the holding interval of a control input. In the proposed method, the dual-rate system is converted to a multi-input multi-output single-rate system, and controller parameters are optimized using one-shot closed-loop data. Furthermore, the ripple-free condition is clarified. Finally, the effectiveness of the proposed method is shown through a numerical example. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

In the present paper, we discuss a new design method for a proportional-integral-derivative (PID) control system using a model predictive approach. The PID compensator is designed based on generalized predictive control (GPC). The PID parameters are adaptively updated such that the control performance is improved because the design parameters of GPC are selected automatically in order to attain a user-specified control performance. In the proposed scheme, the estimated plant parameters are updated only when the prediction error increases. Therefore, the control system is not updated frequently. The control system is updated only when the control performance is sufficiently improved. The effectiveness of the proposed method is demonstrated numerically. Finally, the proposed method is applied to a weigh feeder, and experimental results are presented. © 2014 by ASME.

Most weigh feeders are controlled by a PID control method, and it is desirable to achieve high performance with this PID control. The present paper discusses the application of a generalized predictive control (GPC)-based PID controller to a weigh feeder. In conventional methods, GPC-based PID controllers are designed using a step-type reference signal, but in control of a weigh feeder, a reference input to be followed by a measured signal is a ramp-type signal because the measured signal is discharged mass. Hence, control of a weigh feeder using a GPC-based PID controller is enhanced for tracking a ramp-type signal. Because GPC can be expressed by PID parameters, the proposed method can be easily adopted in various industries. Experimental results show that a weigh feeder is well controlled using the enhanced GPC-based PID controller. (C) 2009 Elsevier Ltd. All rights reserved.