佐藤 孝雄

This study aimed to develop a method for estimating indoor human locomotion to confirm safety of an elderly person. To achieve this, we considered a method using a microwave sensor. Microwaves are reflected by the human body, and pass through obstructions such as glass windows and walls. There have been some previous researches on this topic. However, in these researches, human locomotion was estimated using distances from sensor to human measured by multiple microwave sensors. Since typical microwave sensors are velocity sensors using Doppler effect, their use for measurement or calculation of distance causes cumulative errors. Thus, this paper proposes a new indoor human locomotion estimation method using a human's velocity data, which can be directly measured by the sensor. The method was realized using an Unscented Kalman filter, and is known as a state estimation method. A human locomotion estimation experiment was carried out to confirm its feasibility. © 2014 ICIC International.

This paper proposes a new design method for a drum boiler system, which is a benchmark problem for proportional-integral-derivative (PID) control. In this study, the boiler is divided into two single-input single-output (SISO) systems, and two control systems are designed, even though the boiler is a multi-input multi-output (MIMO) system with interference. As a result, the control system design for a SISO system is simpler than that of a MIMO system. In the proposed method, interference is considered a disturbance, and a controller is designed for each SISO system. Because the plant models are time-varying systems, the proposed control system is automatically updated based on generalized minimum variance control (GMVC) such that the user-specified control performance is achieved. © 2014 ICIC International.

In recent years, multirate control has been evaluated for various nonlinear models. This paper presents a multirate control method for a twin-rotor type model helicopter. It is known that a twin-rotor type model helicopter is not easily controlled because of its strong nonlinearity. Although a multirate control method for nonlinear models has already been proposed, a significant number of calculations are required. Thus, nonlinear theory is not practical for built-in computers with low computing power. Therefore, this paper proposes a new control method for a nonlinear plant. In the proposed method, a linear control law is designed based on a linearized nonlinear plant model. The experimental results show that the control objective can be achieved by 2DOF (degree-of-freedom) integral compensation, even if there is a modeling error, and the effectiveness of the proposed method is verified. © 2014 ISSN 1881-803X.

In this study, we design a Fault-Tolerant Control (FTC) system based on estimation of fault signals, using a discrete linear multi-input multi-output (MIMO) system model. The FTC system can maintain nominal performance if a fault occurs in one of its components. The existing FTC method has the following 3 steps: Fault-Diagnosis, Estimation of fault magnitude, and Generation a new control law to compensate for the fault effect. The existing FTC method assumes that actuator and sensor faults correspond to a loss of actuator effectiveness or fault sensor measurements. Therefore, it cannot maintain nominal tracking control performance when an actuator has a failure that suggests complete breakdown of function. In this paper, we present a new FTC method that is extended to deal with the failure of an actuator. We confirm the feasibility of the presented FTC method by FTC simulation by comparison with the existing method. © 2014 ISSN 1881-803X.

The present paper proposes a simple design method for a multirate sampleddata system, where the sampling interval of the plant output is an integer multiple of the hold interval of the control input. In the proposed method, a proportional-derivative (PD) compensator is based on a multirate generalized predictive control (GPC) law. Since the proposed control law can be designed independently of the sample response, intersample ripples are eliminated without changing the sample response. Therefore, in the proposed method, even if integral compensation is not used, the ripples between sampled plant outputs can be eliminated. Simulation results have revealed the effectiveness of the proposed method. © 2014 ISSN 1881-803X.

This paper discusses a design method for a Generalized Minimum Variance Control (GMVC)-based Proportional-Integral-Derivative (PID) control law in a two-degree-of-freedom (2DOF) system. The PID parameters of a PID control law are designed based on GMVC and are updated using the self-tuning method. In the conventional method, a 2DOF PID control law is based on GMVC with a feed-forward compensator (abbreviated as FF-type GMVC), and the feed-forward compensator is approximated by a PID compensator, but the structure of the PID compensator is restricted and the order of the feed-forward compensator is decided by the length of a dead-time. Therefore, the approximation accuracy deteriorates if the dead-time is long In this study, a 2DOF PID control law is newly designed based on a PC-type GMVC that 2DOF GMVC is designed using a pre-compensator, and the approximation error caused by the structure of a 2DOF system is investigated. Furthermore, it is clarified that the FF-type and PC-type GMVC-based PID control laws are not same although the PC-type and FF-type GMVC laws can be designed equivalently.

The present study discusses a model-free design method for control systems using fictitious reference input tuning (FRIT), which was originally designed based on one-shot control data. Moreover, FRIT has been extended to an online tuning method to cope with plant fluctuation. In the present study, the control quality is monitored using online FRIT. In the conventional online FRIT, the control system is always updated. In the proposed method, performance evaluation is introduced to the online FRIT. Consequently, quality monitoring can be implemented by online FRIT, and a control system can be updated only when a controlled plant fluctuates or the control performance deteriorates. The effectiveness of the proposed method is demonstrated through numerical examples.

The present paper discusses a new design method for a PID control system using 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 automatically selected to attain a user-specified control performance. In the proposed scheme, estimated plant parameters are updated only when the estimation error increases. Therefore, the control system is not updated frequently, The control system is updated only when the control performance is sufficiently improved. Numerical examples demonstrate the effectiveness of the proposed method.

The present paper proposes a new design method for a multirate system, in which the continuous-time plant is controlled by updating the discrete-time control input, in which the sampling interval of the plant output is an integer multiple of the hold interval of the control input. In the multirate system, the intersample response might oscillate even if the sample response converges to the reference response because the control input can vary between sampling instants. In the present paper, a multirate proportional-derivative control system is enhanced such that the steady-state intersample ripples are eliminated. In the proposed method, the intersample response can be improved independently of the sample response because an existing closed-loop response is maintained. Moreover, the control performance is not affected by the phase lag caused by the integral compensation because the integral compensation is not used for the elimination of the intersample ripples. Finally, in order to control a plant with unknown or time-varying parameters, the designed multirate control system is extended to a self-tuning controller. As a result, an unknown or time-varying plant can be controlled using the proposed method. © 2013 Inderscience Enterprises Ltd.

This paper discusses a design method of self-tuning control. In order to control a nonlinear system by using the linear control theory, a controlled plant assumed to be locally linear. Because the dynamic characteristics of an approximated linear model vary widely in response to operating environment, a plant model must be modified according to the changed environment. To obtain an accurate model, a lot of linear models are simultaneously identified, and a control system is designed based on one local linear model. To decide one local linear model from many linear models at sampling interval, the plant parameters of local linear model candidates are estimated using GPGPU (General-Purpose computing on Graphics Processing Units). © 2012 Intl Jrnal Advanced Mech.

This paper discusses a design method for a sampled-data control system, in which the sampling interval of the plant output is an integer multiple of the hold interval of the control input. To control such a control system, an adaptive multirate Proportional-Derivative(PD) control method is proposed. It is assumed that the sample response can stably follow its reference input by a multirate PD control law without the steady-state error, and the multirate PD control law is extended independently of the sample response such that intersample ripples are eliminated in the steady state. Furthermore, the extended multirate PD control system is enhanced with an adaptive law in order to achieve the control objective even if plant parameters are unknown or changed. In the proposed method, the transient response is not deteriorated by the integral compensation because the steady-state error and intersample ripples can be eliminated without the integral compensation. © 2012 Intl Jrnal Advanced Mech.

This paper deals with a multirate control system, where the sampling interval of the plant output is an integer multiple of the hold interval of the control input. In that multirate system, the intersample output may oscillate in steady state even if a sampled output converges to a set point. The oscillation is called ripple, and it causes a deterioration of the control performance. This paper proposes a new design method to suppress the ripple in the multirate system using the integral compensation. In the proposed control system, the integral compensation is revealed only when there is a modeling error or a disturbance. Therefore, the transient response is not deteriorated by the integrator if neither a modeling error nor a disturbance exists. A numerical example demonstrates the effectiveness of the proposed method. © 2012 Intl Jrnal Advanced Mech.

This paper proposes a new design method for a sampled-data multirate control system, in which the sampling interval of the plant output is an integer multiple of the hold interval of the control input. An existing control law which stabilizes a closed-loop system is extended such that the sample response is maintained and integral compensation is revealed only when there is a modeling error or a disturbance. The transient response is not deteriorated by the integral compensation when neither a modeling error nor a disturbance exists because the proposed method is designed as a two-degree-of-freedom system.

In the present paper, we discuss a new design method of a PI control system for controlling a weigh feeder. The PI parameters of a PI controller are based on generalized predictive control (GPC). Since the design parameters of GPC are selected in order to achieve a user-specified control performance, the PI parameters are adaptively updated such that the control performance is improved. In the proposed method, estimated plant parameters of a weigh feeder are updated only when the estimation error increases. Therefore, the control system is not updated frequently, and the control system is updated only when the control performance is sufficiently improved. The effectiveness of the proposed method is demonstrated through numerical examples and experimental results.

In the present paper, we discuss a design method for controlling a weigh feeder that has been widely used in industry. Since a control system is designed using a performance-adaptive method, the control parameters are adaptively updated based on user-specified control performance. In conventional performance-adaptive methods, control systems are designed such that the variance of the control error is less than or equal to a specified value and the variance of the differences in the control input is minimized without changing the acceptable variance value of the control error. On the other hand, since the design objective of the present study is to reduce energy consumption, the variance of the differences in the control input is first set, and then the variance of the control error is minimized without changing the acceptable variance value of the differences in the control input. Consequently, the variation of the control input can be substantially reduced. In the proposed method, a proportional-integral controller is designed based on generalized minimum variance control (GMVC) with steady-state predictive output (GMVCS). One of the design parameters in GMVCS is automatically decided such that a desired control performance can be attained, and the PI parameters of a PI control law are calculated based on a GMVCS law.

Proportional-Integral-Derivative (PID) control is the most widely used control method. Since, PID control performance can be adjusted by tuning the PID parameters, the selection of the PID parameters is very important, but optimal PID parameters are not easily obtained. Advanced control has high potential, but on-site engineers prefer PID control to advanced control. Hence, advanced control needs to be achieved by PID control. In this chapter, generalized predictive control (GPC) is attained by PID control. First, the technique that GPC law is approximated by a PID control law is introduced. Next, the obtained GPC-based PID control is applied to a weigh feeder. Finally, the design method of a GPC-based PID control system is extended to a multirate system in which the sampling interval is an integer multiple of the update interval.

The decision of sampling and hold intervals is an important issue in the design of sampled-data control systems, in which a continuous-time plant is controlled using a digital computer in discrete time, and the selection of intervals greatly influences the control quality. However, it is not easy to set these intervals arbitrarily because of hardware constraints. This paper proposes a new method for the design of a multi-rate single-input single-output sampled-data control system under the constraint that the sampling interval of the plant output in continuous time is an integer multiple of the hold interval of the control input, which is updated in discrete time. In the design of the multi-rate control system, the intersample plant output can possibly oscillate even if the sampled plant output converges to its reference input. In conventional design methods, to improve intersample ripples, both the sample and the intersample responses are simultaneously designed, and then, the original sample response might be deteriorated even though the intersample response is improved. In this study, a multi-rate control law, which stabilizes a closed-loop system, is extended on the basis of state-space representation, and the multi-rate control system is redesigned such that the steady-state intersample response is improved independently of the sample response. As a result, the sample response is maintained and the intersample response is improved in the steady state. Numerical examples demonstrate the effectiveness of the proposed method. © 2012 The Institute of Electrical Engineers of Japan.

The present paper proposes a new method for designing a weigh feeder control system. The model of a weigh feeder cannot be obtained accurately because its dynamic characteristics are time varying and its high frequency vibration modes are not easily identified. In the present paper, a weigh feeder is approximated as a first-order plus integrator system, and a self-tuning controller is designed on the basis of the approximated model to estimate its gain recursively. The purpose of this study is to design a controller to be actually employed in industry. To this end, a controller is assumed to consist of proportional gain for control error and steady state control input. As a result, the proposed controller has a simple structure and its controller parameters can be understood intuitively. Consequently, the proposed design method can be easily adopted in industry. Numerical and experimental results demonstrate its effectiveness. Copyright © 2011 Inderscience Enterprises Ltd.

This paper proposes a new design method for the positioning control system of a hard disk drive (HDD) head. To control the head in an HDD, the control input supplied to the voice coil motor is updated at a fast rate, but the sampling interval of the head position is restricted because of hardware constraints. Hence, the designed control system is a multirate system. In this study, the multirate control system designed for controlling the head in an HDD is extended, and the intersample response is improved independently of the sample response. The effectiveness of the proposed method is demonstrated by a numerical example. © 2011 Zhejiang University.

This paper proposes a new design method for controlling a head in a hard disk drive (HDD) system. In the HDD control system, the sampling interval of the head position is restricted, but the hold interval of the control input can be arbitrarily set. Hence, this study discusses a design method for a multi-rate control system, where the sampling and the hold intervals are not equal. In this study, a pole-assignment multi-rate control law is extended using newly introduced parameters such that the sample response of the plant output is maintained. Furthermore, intersample ripples in the steady state are eliminated using the new design parameters because those can be selected independently of the sample response. As a result, the intersample response can be improved independently of the sample response. The proposed method is applied to a benchmark problem of a HDD system, and its effectiveness is demonstrated. © 2011 IFAC.

In the petroleum and refinery industry, it is necessary to establish the performancedriven control strategy in order to improve productivity (where the control performance is first evaluated and then the controller is re-designed). This paper describes a design scheme of performance-driven controllers which are based on the control mechanism described above. The proposed control scheme is simulated and its performance is numerically examined. Also, the proposed method is applied to the weigh feeder and the control results are shown. © 2011 IFAC.

In the design of a weigh feeder control system, proportional and integral (PI) control is widely employed because parameter tuning is easy and the control parameter can be intuitively understood. Hence, it is desirable to achieve high control performance using PI control rather than advanced control methods. In this study, the control parameters of the PI control system are designed on the basis of generalised minimum variance control (GMVC), and the weighting parameter for the control deviation is adaptively updated according to the control performance. Because GMVC-based PI control is based on control performance, this method can be easily adopted in industry. Both the simulation and the experimental results demonstrate the effectiveness of the GMVC-based PI control. Copyright © 2011 Inderscience Enterprises Ltd.