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Using an agent-based traffic models, we analyze the manner in which the number of platoons within a traffic system is correlated with the appearance of traffic jams. Two definitions of a platoon are proposed and verified using agent-based simulations to find the one that provides the most realistic representation of traffic behavior in a stochastic model. We observe that traffic jams are closely related to the convergence of multiple platoons into a single platoon containing all the agents in the model. We also observed that at high-density, traffic system maintains a metastable state when it has multiple platoons in it. A traffic jam occurs when these multiple platoons are merged into a single platoon, which is equivalent to the concept of an infinite cluster in percolation theory.

In this paper, an agent-based model of ant traffic on a unidirectional single-lane ant trail is presented to provide better understanding of the jam-free traffic of an ant colony. On a trail, the average velocity of ants remains approximately constant irrespective of density, thereby avoiding jamming. Assuming chemotaxis, we analyze platoon-related scenarios to assess the marching-platoon hypothesis, which claims that ants on a trail form a single platoon in which they march synchronously, thereby reducing hindrances due to increasing density. Contrary to that hypothesis, our findings show that ants on a trail do not march synchronously and do experience stop-and-go motion. However, more interestingly, our study also indicates that the ants&rsquo, chemotaxis behavior leads to a peculiar jam absorption mechanism, which helps to maintain free flow on a trail and avoids jamming. Again, contrary to the marching-platoon hypothesis, our findings also indicate that, rather than assisting traffic flow, forming a single cluster actually triggers jamming.

This paper presents a vibration control strategy for a flexible manipulator with a collocated piezoelectric sensor/actuator pair. A hybrid vibration controller is proposed by combining the input shaping technique with auto disturbance rejection controller. The parameters of the closed-loop system can be adjusted to the known values by disturbance compensation and linear feedback using the auto disturbance rejection controller. This way, input shaper can be designed without accurate parameters of the flexible manipulator. Both simulation and experiments are conducted to validate the proposed control algorithm. The results verified the effectiveness of the proposed controller in vibration suppression of flexible manipulator.

In this paper, to analyse the rider's effects on the motion of a motorcycle, we model a rider–motorcycle system by taking into account the leaning motion of the rider's upper torso and his/her arm connection with the handlebars. The nonlinearity of the tyre force is introduced by utilising hyperbolic tangent functions to approximate a Magic Formula tyre model. On the basis of a derived nonlinear state-space model, we analyse the effects of not only the rider's arms but also his/her postures during steady turning by simulations. The rider's postures including lean-with, lean-in and lean-out are realised by adding the lean torque to the rider's upper torso. The motorcycle motion and the rider's effects are analysed in the case where the friction coefficient of the road surface changes severely during steady turning. In addition, a linearised state-space model is derived during steady turning, and a stability analysis of the rider–motorcycle system is performed.

In this paper, to realize the comfortable steering feeling during driver's steering or a rough road running, we design a control system of an electric power steering (EPS) for a vehicle with an active stabilizer. Although control systems of the conventional EPS are designed generally to obtain the comfortable steering feeling similar to that using a hydraulic power steering (HPS), the steering feeling might not be realized on a rough road. We propose a design strategy for the control system of the EPS in consideration of the active stabilizer to avoid side effects to the steering system by the reaction force of the front tire due to roll stiffness control for the active stabilizer. According to the design strategy, a controller of the EPS is designed and tuned to realize the HPS-like steering feeling by applying a gain-scheduled control corresponding to both a vehicle speed and a sensor torque on a steering axis in consideration of the active stabilizer, which is designed so as to not only reduce the roll motion of a vehicle body but also suppress the restoring torque which acts on the steering axis through the front tire during the rough road running. It is verified that the control system of the EPS designed is effective to realize the HPS-like steering feeling during the driver's steering and suppress the rotational vibration of a steering wheel during the rough road running.

In this paper, we propose a design method of a reference-filtering-type two-degree-of-freedom control system with a structure of antiwindup feedback control in order to overcome actuator saturation problem. By using a hyperbolic tangential function as the saturation function, the time derivative of the controller output is introduced in order to construct a servo system. Thus, a linear parameter-varying system is formulated to design a gain-scheduled feedback controller by using linear matrix inequalities. In order to manage the reference signal taking account of actuator saturation, the feedforward reference signal is obtained offline by applying final-state control with error learning for the closed-loop system including the gain-scheduled feedback controller that may continuously vary before the actuator saturates. The effectiveness of our proposed method is verified by carrying out both simulations and experiments for stabilizing and positioning control of a cart and inverted pendulum system.

In this paper, a dynamical model of a motorcycle, which consists of four rigid bodies with nine degrees of freedom, is presented. In this model, the cross-sectional shape of the tire is described as a half-circle and its deformation is taken into account. By taking account of the tire slip condition or the tire nonslip condition in the longitudinal direction of the wheels, each equation of motion is derived. Also, by carrying out simulations, it is verified that the responses to the front steering impulsive torque are in good agreement with the results obtained using commercial software. Moreover, the longitudinal friction force and the lateral force in a turning maneuver are analyzed.

In this paper, we deal with the active control of shock caused by the collision between two objects so as to make the deformation of the shock-receiving object large and the deformation of the shock-giving object small. Since the shock-receiving object deforms from the elastic range to the plastic range, we formulate a linear parameter-varying system to cover all the ranges and apply gain-scheduled (GS) control. Also, we utilize a frequency weighting function with varying gain in order to improve the performance of shock control. The GS control system exerts a continuous input when the deformation of the shock-receiving object changes from the elastic range to the plastic range. It is verified experimentally that the designed GS controller is effective for the active control of shock and that the plastic deformation ratio between the two objects is increased.

When large external forces come from road, a suspension stroke reaches the limitation and the riding comfort may reduce. In order to overcome this problem we propose a new control method for an active suspension which can avoid reaching the stroke limitation. A sliding mode controller is designed in consideration of rigidity variation of the spring. Also in order to estimate the internal state of the suspension, VSS (Variable Structural System) observer is designed without information of nonlinear force which occurred in rigidity variation when the suspension reaches the stroke limitation. By carrying out simulation and experiment of a quarter-car suspension model it is verified that the performance of the controller is superior to that of the method, which switches to a passive damper near the stroke limitation from LQR (Linear Quadratic Regulator) in the range of small stroke.

This paper deals with damage detection and vibration control of a smart structure. A finite element model of a cracked beam is established. This model is applied to a cantilever beam and the natural frequencies are determined for a different crack length and locations. This study proposes a method for the crack identification when the vibration of the beam is suppressed by using active control. Once cracks are present in structures, the control performance becomes worse. This is because both eigenvalue and eigenvector of the beam vary. So, in this study we design the gain-scheduled controller considering both the crack length and the location. To obtain the linear parameter-varying (LPV) model for controller design, its Frobenius norm is measured. The efficiencies of our crack identification method and the gain scheduled controller design are verified by simulation.

In this paper we propose a design method for active seismic isolation control taking account of actuator saturation. By using a hyperbolic tangential function that is differentiable to controller output, we formulate the linear parameter varying system according to the controller output and design a gain-scheduled controller. By carrying out simulations and experiments of seismic excitation, our proposed gain-scheduled controller is compared with an H∞ fixed controller or a sliding mode controller. It is verified that the proposed controller maintains performance of isolation even if a large earthquake with which the actuator saturation occurs comes, although the other controllers lower the performance than uncontrolled case.

In this paper we try to realize the active control of shock by an experimental procedure, in which the collision between two objects is controlled so as to make the deformation of one object large and the other small. Two control systems are applied to this experiment. One of them is an LQI control system with Kalman filter and the other is an H∞ control system. In both systems, we proposed a controller switching at a time when the object deforms from the elastic range to the plastic range. In order to evaluate effectiveness of control, the deformation ratio between the objects is introduced. In our experiment the discretized control system is implemented in a digital signal processor used to realize real-time control. As a result of experiment it was verified that the active control of shock is realizable and the controller we designed is useful for shock control.

In this paper, we deal with a three-link space robot moving in planar space without controls for the base attitude. Our experimental setup of the three-link space robot can levitate by use of compressed air. Using d'Alembert principle, it is shown that the state equation of the three-link space robot can be reconstructed as a first-order nonholonomic system with the constraint condition that the rotational velocity of the base is set to be zero. The suitable final postures corresponding to the desired position of the end effector can be determined using the concept of the enhanced disturbance map. Based on the state equation, the feedforward torque inputs can be obtained by the final-state control in order to bring the end effector from an initial position to the desired position. The torque inputs and trajectories obtained are smooth. We designed a two-degree-of-freedom control to follow the obtained trajectory. It is verified from simulation and experiment that the proposed method of motion control is useful.

System identification of the motorcycle model constructed by computer-aided dynamics analysis is introduced to design a control system for attitude stabilization of the motorcycle. The identified model can be reduced to the coupled mode system between the roll and the front steering. The front-steering control system using the roll angle is designed by H ∞ control theory, based on the reduced-order model and the full-order model, respectively. It is verified from simulation results that the motorcycle attitude against disturbance is stabilized by the H ∞ controller, and that the reduced-order controller exhibits efficient stabilization performance in comparison with the full-order controller.

System identification of a real motorcycle is performed to design a control system for attitude stabilization of the motorcycle by front-wheel steering. In system identification, a front-steering impulsive torque is used as the input signal and the roll angle response is used as the output signal. We reduce the identified model to the third order model and design the front-steering control system using the roll rate as the feedback signal by H∞ control theory. It is verified from experimental results that the attitude of motorcycle against front-steering torque disturbance is stabilized by the H∞ controller.

In this paper, we propose a method of control system design which takes the actuator saturation into consideration. By using a hyperbolic tangential function as the saturation function, we introduce both the time derivative of the controller output and the anti-windup control structure with the feedback loop of the error between the controller output and the saturation function output. Furthermore, we formulate a linear parameter-varying system to design the gain-scheduled controller. The effectiveness of our proposed method is verified by carrying out the experiments of the positioning control for a cart and inverted pendulum system.

System identification of a motorcycle by Computer-Aided Dynamics Analysis is introduced to design a control system for the attitude stabilization. The identified model can be reduced to the coupled mode system between the roll mode and the front-steering mode. We design the gainscheduled front-steering control system using the roll angle as the feedback signal, which is according to the varying parameter of motorcycle velocity. It is verified from simulation results that the motorcycle attitude against disturbances is stabilized by the gain-scheduled controller at the wide range velocity.

This paper deals with modeling and control of a crane mounted on a tower-like flexible structure. A fast transfer of the load causes swaying of the load rope and vibration of the flexible structure. Our object is to control both the sway and the vibration by the inherent capability of the tower crane. We have already succeeded in realizing a decentralized control consisting of two individual controllers. This paper describes the design of a centralized control system considering coupling of between the up-and-down (boom luff) direction and the rotational direction. This is because there is a possibility that the control worsened due to the decentralized control system because it did not take into account coupling both directions. It is, therefore, necessary to compare it with a centralized control system and to examine the advantage of a decentralized control system precisely. From the results of the comparison of experiments and /spl mu/ analysis, it is shown that the decentralized control system has almost the same performance and stability as the centralized one and that it is effective for the control of a tower crane.

To evaluate performance of a developed engine, the vehicle model constructed on a computer can be virtually reproduced using a low-inertia dynamo. This engine test bed does not require any devices of the actual vehicle except for the engine. In this paper, we show a control method of a low-inertia dynamo connected to an engine with a six-speed gear transmission through a flywheel with a spring and a damper (FSD) and a steel shaft, in order to generate arbitrary load torque according to the vehicle model simulation. We regard the variation of the gear ratio with shifting of gears as the parameter variation in the system and apply μ-synthesis to obtain a single fixed-controller that is applicable from the first gear to the sixth gear. By carrying out simulations and experiments it is demonstrated that the μ controller designed is effective for virtual drive on the engine test bed.

In this paper, we propose a method of control system design which takes the actuator saturation into consideration. By using a hyperbolic tangential function as the saturation function, we introduce both the time derivative of the controller output and the anti-windup control structure with the feedback loop of the error between the controller output and the saturation function output. Furthermore, we formulate a linear parameter-varying system to design the gain-scheduled controller. The effectiveness of our proposed method is verified by carrying out the experiments of the positioning control for a cart and inverted pendulum system.

In this study, we deal with the twisting motion of a falling cat robot by means of two torque inputs around her waist. The cat robot consists of two rigid columns and has two internal actuators at the joint to generate torque inputs around normal coordinates. This system is a nonholonomic system whose angular momentum is conserved. We formulate the state equation that has torque inputs to the joint by using the nonholonomic constraint and the Lagrange-d'Alembert principle. Then, we transform the system into a linear parameter varying system. In order to improve error learning of a final-state control method, we provide the initial inputs in order to determine the appropriate rotation direction in the early stage of the twisting motion. Next, we introduce the method of the artificial potential function to the final-state control in order to make the maximum bending angle small. The feedforward torque inputs can be obtained by the final-state control in order to bring the system from the initial state to th...

This paper proposes a design method for active vibration isolation control of a structure taking account of actuator constraints. The gain-scheduled control based on the linear matrix inequality is obtained so that the closed-system is stable and has good performance even if saturation phenomena of the actuator occur. By simulations, it is shown that the gain-scheduled controller has higher performance than the fixed controller against a non-stationary random input such as earthquakes.

In order to evaluate performances of an engine that is developed, there is a way that a certain vehicle model constructed on a computer is virtually performed by using a low-inertia dynamo. This way does not need any devices of the actual vehicle except for the engine. This paper shows the control method of the low-inertia dynamo connected to the engine through a hydraulic damper and a steel shaft so as to generate the torque according to the vehicle model simulation. Since the hydraulic damper used to absorb the impulsive torque from the engine has nonlinear property of variation of its torsional rigidity, we apply μ-synthesis by using of structured singular value. Variation of the torsional rigidity can be dealt with as structured uncertainty. By simulations and experiments it is verified that μ controller designed is more effective for the plant with variation of parameter than H∞ controller.

This paper proposes a design method for vibration isolation control of a semi active suspension for automobiles. By using nonlinear functions we formulate the linear-parameter-varying system taking account of mechanical constraints such as valve stroke of the semi-active damper and the damping coefficient restriction. The gain-scheduled controller based on the linear matrix inequalities is obtained so that the closed-loop system may be stable and have good performance even if saturation of the valve stroke occurs. By simulations it is verified that the semi-active damper system designed is effective in comparison with either a passive damper or a conventional switching law based on H∞ control.

In this paper, the author proposes a control method that can bring a system to an arbitrary final state even if the input is already saturated, by adopting a hyperbolic tangential function that describes the input limitation. Furthermore, by using the derivative of the function, the obtained input becomes continuous at terminal points of an initial time and a final time. This formulation of the input limitation can be described by a linear parameter-dependent system and the final-state control with error learning can be applied to the system. The effectiveness of this method is verified by carrying out both simulations and experiments of the swing-up motion control of a cart and inverted pendulum system, whose cart displacement is limited. This method does not require precise determination of the final time and can generate a continuous, smooth, feedforward control input when the output of the actuator is limited.

This paper proposes a design method for vibration control of a structure with an active dynamic vibration absorber involving actuator constraints. We formulate the linear parameter varying system taking into account both the maximum control input and the maximum stroke of the actuator by using a nonlinear function of hyperbolic tangent. The gain-scheduled control based on the linear matrix inequality is obtained so that the closed-loop system is stable and has good performance even if saturation phenomena of the actuator occur. By simulations we verify that the proposed method is useful for not only an impulsive input but also a non-stationary random input such as earthquakes.

This paper deals with twisting motion of a falling cat robot by two torque inputs around her waist. The cat robot consists of two rigid columns and has internally two actuators at the joint to generate torque inputs around the normal coordinates. This system is a nonholonomic system whose angular momentum is conserved. We obtain the Lagrange's equation of motion with nonholonomic constraint and formulate the linear parameter varying system. Then, in order to get the twisting motion we apply the error learning method of final-state control with amplitude constraint of inputs. In simulation we show that the two-link cat robot can pose so that she lands on her feet, by using of the obtained feedforward torque inputs by the final-state control.

Minimizing the damage to buildings from large earthquakes is very important in maintaining urban function, especially if buildings contain critical facilities. Although passive isolation systems have been used in civil structures, if earthquakes of such great magnitude occur these systems are ineffectual, an active seismic isolation system may be useful. The article discusses the design method of an active vibration isolator for a multi-degree-of-freedom structure such as a tall building. The controlled variables are selected based on minimization of interaction between a controlled structure and its base. The controller design employs the well-known /spl mu/-synthesis approach-considered one of the most robust control methods for parameter variations of the controlled structure. Based on experiments on our laboratory structure and on simulations of an actual building, a controller is designed for an active vibration isolator whose passive elements are installed in parallel with the active element. We show that the proposed design method is useful for seismic isolation of tall buildings.

This paper examines a design method of active vibration isolation control for multi-degree-of-freedom systems such as tall buildings subjected to seismic disturbances. In the simulation for a real building, the controller is designed for the active vibration isolator where the passive elements are installed in parallel with the active element. We also examine the performance of control robustness against the nonlinearity of the passive elements depends on the amplitude of the input disturbance.

This paper demonstrates that motion control of a three-link brachiation robot can be performed via final-state control for a linear parameter-varying system with error learning. Since the root joint of the brachiation robot has no drive unit, the control problem is treated as that for an open-chain manipulator possessing nondriven joints in circumstances with gravity. Also, the brachiation robot possesses a nonlinear property in its wide motion area from an initial state to a final desired state. We treat the brachiation robot as a discrete-time linear parameter-varying system by using an extended linearization method and Euler's method. In the experiments, the second and third joints of the brachiation robot are directly driven by AC servo motors installed in each joint. The free vibration of the brachiation robot is coincident with that of the simulation and gives suggestions of the final time to reach a desired state that has to be specified for final-state control. By simulations and experiments, it is demonstrated that the feedforward input obtained by the final-state control method can bring the three-link brachiation robot from an initial state to a desired state in a specific time. Its robustness under a variation of the link mass is also verified.

This paper discusses control of a crane mounted on a tower-like flexible structure. Although a fast transfer of the load suspended from the edge of the boom of the crane causes not only the sway of the load itself but also the vibration of the flexible structure, the objective of this study is to control both the sway of the load and the vibration of the flexible structure by the up-and down positioning control torque to the boom. At first a mathematical model for the experimental model of the tower crane and a reduced order model for a controller design are introduced. Next, we design an H∞ compensator for the reduced order model so that the compensator simultaneously controls the position of the boom, the sway of the load and the vibration of the flexible structure, and suppresses the spillover phenomenon due to the model reduction. By simulations and experiments it is verified that the designed compensator has superior vibration control performances to those the conventional angular velocity control for the boom has.

This paper discusses control of a crane mounted on a tower-like flexible structure in the case of varying load-rope length. A fast transfer of the load causes the sway of the load and the vibration of the flexible structure. Our object is to control both the sway and the vibration by control of torque to the boom. But if the length of the load rope varies, it is difficult to control by the fixed compensator, bacause the natural frequency of the load rope and gain of the plant to control input vary also. So, we design the gain scheduled H∞ compensator based on the LMI for the length of the load rope and verify the efficiency of the gain-scheduled H∞ compensator by simulations and experiments.

The advantages of applying sensorless control to mechanical systems are cost reduction, maintenance of stability of a control system by collocation, noise reduction, decrease of breakdown frequency, increase of reliability, and space saving. In order to realize such a control system, robust performances are required in the state estimation in addition to the control law, so we combined a VSS observer and sliding mode controller and constructed a sensorless nonlinear robust control system. We used a four-degree-of-freedom tower structure with a hybrid dynamic vibration absorber (hybrid DVA) using a linear motor as a control object. It is possible to estimate the state of the system by means of an observer from the coil current of the linear motor for the mutual interaction on the dynamics in the state equation of the system. Then we applied a VSS observer/sliding mode control combination type sensorless nonlinear robust control system to the vibration control system of the structure. Moreover, we investigated performances with regard to vibration suppression.

This study proposes a method for obtaining a feedforward input for motion control of a brachiation robot which has a nonlinear property in its dynamics. We deal with the brachiation robot which has three links with two actuators and no actuator at the root of the first link. We regard the brachiation robot with a nonlinear property as a time-varying system and apply the error learning method of final-state control. We especially adopt an iteration method which uses a learning coefficient less than 1 to improve the convergence property for errors of final state. By simulation taking into consideration the nonlinear property of the brachiation robot, we verify that the desired final state is achieved using the feedforward input obtained. As a result, we see that the iteration method using error learning is useful for motion control of the nonlinear system.