This paper investigates the detection of parameter variation in data-driven type self-tuning control systems. In the self-tuning of a controller, an extended output is used to update PID gains online without the mathematical model of a plant. Moreover, suitable control parameters for a PID controller are estimated by Kalman filtering. The estimate of the control parameters is adopted as PID gains. The performance of the self-tuning control approach is evaluated under the variation of plant parameters. Through simulation results, it is shown that when the natural angular frequency or damping ratio of a plant changes, output error estimate vibrates. By observing the vibration, the parameter variation can be detected.

This paper considers the anomaly detection of mobile robots in the consensus control, whose objective is to that states of all agents in a multi-agents system converge to common state value by exchanging information over a network. In the presented scheme, one class support vector machine, that is one of unsupervised learning approaches, is used and multiple classifiers are designed to deal with two cases: i) a failed robot does not move from the initial position and ii) a failed robot continues to move in a certain direction. Simulation and experiments with omnidirectional mobile robots show that anomaly detection accuracy is improved by using both two classifiers.

This paper gives a novel method to design less‐conservative robust PID control systems. The partial model matching method is a design method for PID control systems. That is a method to design a control system that matches a reference model as closely as possible. This method does not guarantee robust stability of a PID control system because it is assumed that there are no uncertainties on the coefficients of the lower‐order terms of the plant. Therefore, in our previous work, a robust design method based on the partial model matching method was proposed. However, the drawback of this conventional method is that the results of stability analysis are conservative. In this paper, we aim to reduce the conservativeness caused by the conventional method. To achieve this goal, we use a robust stability analysis method based on the Cremer–Leonhard–Mikhailov criterion and the mapping theorem. Moreover, we also propose a new method to update the value of a design parameter. A numerical example shown in this paper implies that the conservativeness is reduced by the proposed method. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

In this paper, we investigate power adjustment for multi‐agent systems in a wireless network where communication range is limited. The approach in which communication range is dynamically changed is utilized so as to save power consumption. However, since drawback of this approach is that agents cannot expand their communication range, it causes that communication between agents tends to be disconnected. To overcome this problem, we propose two power adjustment methods. In the first method, communication range is temporarily expanded in accordance with the number of neighboring agents. In the second method, agents change their communication range by using information on the total number of agents and relative distance between an agent and the farthest neighboring agent. Through numerical simulation, we show that the proposed power adjustment methods reduce power consumption and improve success rate for consensus. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Event-triggered stabilization of a discrete-time system via a data-rate limited channel is studied. We concern the data rate required for stabilizability and provide a sufficient number of bits transmitted from the sensor to the controller at each event. When the controller receives a packet, it can extract information on the plant state from the reception timing and the event-triggering condition in addition to the bits carried by the packet. While the amount of the information is impaired by the communication delay and the discrete-time manner of the sampling, we show that for some systems the required data rate becomes lower than that obtained by the well-known data-rate theorem established for time-triggered systems.

In this paper, we consider the $\mathcal{H}_{\infty}$ stabilization problem of the Furuta pendulum with backlash in the drive train and analyze the effect of fictitious bounded-disturbance approximately representing the nonlinearity. Based on the reachable set analysis of the disturbance with an $\mathcal{L}_{2}$ constraint, a subset of the reachable region with $\mathcal{L}_{\infty}$ constraint is computed. By estimating its volume in the state space, the performance against the backlash nonlinearity is evaluated. The behaviour of the closed-loop system is verified through numerical simulations of the time response.

This paper considers data-driven type generalized minimum variance control (GMVC) for p-inputs/q-outputs (p > q) multivariable systems with static nonlinearity. In the proposed approach, an autoencoder, which can extract the feature of input data, is used. First, an encoder converts input data with p dimensions into that with q dimensions. Then, a GMV controller is designed by using the dimension-reduced input data. Finally, the nonlinearity of a plant is compensated by a decoder, which reconstructs the input data with p dimensions. The effectiveness of the presented approach is evaluated using a numerical example.

This paper presents some stability remarks on the discretized diffusion process models. The motivation arises from our observation of stability preserving property in terms of a model reduction procedure of the 1D model. Before the stability analysis of the non-reduced order model, the state-space model is extended to multi-dimensional cases in a systematic manner. This formulation and the corresponding stability analysis are the first non-trivial contributions here. Then we clarify the fact behind the stability preserving property. As a consequence, one can employ arbitrary size of reduced order model based on the techniques such as the principal component analysis without any concern for the stability. The power of this reduction method is demonstrated via numerical examples for the 1D and 2D cases.

In this paper, a model-based design problem of tube pumps are considered to achieve an ultra-low flow rate pulsation. Starting from the modelling of conventional tube pumps having two rollers, we clarify the fact that even the 1 degree of freedom (DoF) structure can realize a flat flow rate by adjusting the rotation speed. Then, it is shown that the 2 DoF setting reduces the amount of the required acceleration of the pushing roller. Equivalently, this can be achieved by a deceleration of the leaving roller. An alternative way to realize it with a constant rotation speed is to modify the wall curve profile at the leaving sector. Its modelling and an optimal design procedure based on this model are given. Finally, we propose a control strategy combining a quasi-optimal wall curve with slight speed adjustment at the bottom of the periodic operation cycle to achieve an almost pulsation-free flow rate.

This paper considers the transmissibility reduction of central pattern generator (CPG) based control system for pneumatic anti-vibration apparatuses (AVAs). This control method is an attenuation method for the flow disturbance, which is the variation of compressed air pressure. A CPG-based controller generates control input, whose frequency is synchronized with the frequency of the flow disturbance. In the proposed method, the parameter in the CPG-based control system is tuned so that the air spring stiffness can be vanished. For this reason, the resonance frequency of the transmissibility can be reduced. It leads to the improvement of transmissibility. The effectiveness of the proposed approach is shown by simulation.

This paper considers a leader-follower type formation control problem under drop out of vehicle. In our approach, when in-degree of vehicles corresponding to follower vehicles is changed due to the drop out, a desired formation pattern is maintained so that relative distance between other vehicles can be kept constant. Simulation results show the effectiveness of the proposed approach.

Identifying the current gait phase is a key in the control of ankle-foot orthoses, which assist ankle motion during walking. We address the problem to estimate whether the foot is in a swing or stance phase only from the ankle angle. A recurrent neural network with long-short-term-memory architecture is developed and evaluated with experimental data.

In this paper, we propose a new method for the synthesis of robust proportional, integral, and derivative (PID) control systems. The proposed method is based on the idea of partial model matching. The stability feeler, a tool for robust stability analysis, is used to stabilize closed-loop systems with uncertainties. An advantage of the proposed method is that it guarantees robust stability of control systems. To clarify the effectiveness of the proposed method, two types of simulations are given. One is the case where the nominal plant is not stable. The other is the case where the plant is not robustly stable although the nominal plant is stable. The simulation results when the nominal plant is not stable show that the controller derived by the proposed method robustly stabilizes the closed-loop system, whereas that derived by conventional partial model matching method cannot stabilize it. Moreover, when the plant is not robustly stable, it can be seen that the controller by the proposed method can robustly stabilize the system. Therefore, it is shown that the proposed method enables one to derive PID controllers robustly stabilizing closed-loop systems. (c) 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

This paper addresses the compensation of the vibration caused by flow disturbance, which is the pressure fluctuation of compressed air supplied to a pneumatic anti-vibration apparatus (AVA). The pressure of the compressed air changes periodically during compression process. For this reason, proportional-integral-sinusoidal (PIS) control is utilized so that the flow disturbance can be attenuated. In this control method, a Sinusoidal compensator (S compensator) provides a periodic control input signal whose frequency is the same as the frequency of the disturbance. However, when the PIS control is applied to the vibration attenuation for the pneumatic AVA, there arise two practical problems that have to be solved. First, the vibration of an isolated table occurs in transient state at the start-up/shut-down of the S compensator. This is due to the switching of the S compensator. To deal with the first practical problem, soft switching approach is presented. Second, high-frequency vibration is observed in steady state after the S compensator is started up. Since the source of the high-frequency vibration is the phase-lag of the S compensator, a phase-lead type PIS compensator is employed. By using this compensator, the phase margin of a control system can be increased and the high-frequency vibration can be attenuated. Moreover, in this paper, vibration transmissibility is analyzed so as to investigate effects of the PIS control on the isolation from floor vibration. It is shown that 1) when the PIS control is used, anti-resonance and resonance are excited and 2) there is a trade-off between flow disturbance attenuation and vibration transmissibility reduction.

This paper considers the trade-off between flow disturbance attenuation and transmissibility reduction for pneumatic isolation tables. In the active control of the pneumatic isolation table, compressed air is supplied to air springs. However, the pressure of the compressed air fluctuates. This pressure fluctuation, which is called flow disturbance, causes the vibration of the isolation tables. Since the pressure fluctuation is periodic, repetitive control is utilized so as to compensate for the flow disturbance. The feedthrough term in a repetitive controller is usually designed as a static compensator. Although the flow disturbance is further attenuated by increasing the gain of the static compensator, the transmissibility becomes large in the frequency region of mechanical resonance of the isolation tables. Therefore, this paper focuses on the setting of the feedthrough term. In the proposed approach, a dynamic compensator is adopted as the feedthrough term instead of the static compensator. Two break-point frequencies of the dynamic compensator are tuned on the basis of the bandwidth of the pressure fluctuation and the mechanical resonance. It is shown that, by using the proposed setting method, the flow disturbance can be attenuated and the peak of the transmissibility can be reduced.

This paper studies selecting a subset of the system's output to minimize the state estimation mean square error (MSE). This results in the maximization problem of a set function defined on possible sensor selections subject to a cardinality constraint. We consider to solve it approximately by a greedy search. Since the MSE function is not submodular nor supermodular, the well-known performance guarantees for the greedy solutions do not hold in the present case. Thus, we use the quantities---the submodularity ratio and the curvature---to evaluate the degrees of submodularity and supermodularity of the objective function. By using the properties of the MSE function, we approximately compute these quantities and derive a performance guarantee for the greedy solutions. It is shown that the guarantee is less conservative than those in the existing results.

Classical analogy between mechanical and electrical systems has a small inconsistency in terms of the mass element. This leads to the invention of the inerter which makes the synthesis of arbitrary passive mechanical network possible based on the established circuit theory. In this paper, we attempt to improve the energy efficiency of periodic motion with a passive mechanism including the inerter. In the research of power assist control of electric bicycle, it is shown that a better energy efficiency is achieved by reducing the velocity fluctuation arising from the human pedaling torque pulsation thorough experiments. The same idea is extended to fully passive control of normal bicycle having an additional mechanical network in the drive train. We verify the effectiveness of the proposed design by the multi-body dynamics simulations.

This paper proposes the state and parameter estimation method in order to compensate for random communication delay. By using time-stamp information, particle filter can be available even in the presence of the delay. The numerical simulation verifies that estimation error can be reduced by using the proposed method.

This paper addresses the compensation problem of flow disturbance and floor vibration for pneumatic vibration isolators. In the proposed method, repetitive control is applied in order to attenuate the flow disturbance. When the tunable parameter of a repetitive controller is selected as high-gain static compensator, the performance of flow disturbance attenuation can be improved. However, in this approach, peak transmissibility increases. It leads to the performance degradation of floor vibration attenuation. In order to balance the trade-off between the flow disturbance attenuation and the peak transmissibility reduction, a phase-lag type dynamic compensator is adopted as the tunable parameter of the repetitive controller. Simulation and experimental results show that the effects of flow disturbance can be compensated and the transmissibility can be improved by means of the proposed method.

The application of Central Pattern Generator (CPG) has been realized in order to suppress flow disturbance caused by pressure variation of air supplied to pneumatic anti-vibration apparatus (AVA) with one degree-of-freedom. In this paper, CPG is applied to pneumatic AVA with two degrees-of-freedom. First, experimental results show that stable levitation of AVA is possible by using only CPG without PI compensator. Next, the suppression performances of PI compensator and CPG are compared. As a result, the superiority of performance by CPG is confirmed.