The performance on braking of a vehicle is recently improved in the generation of brake-by-wire systems. In this paper, a new brake system is proposed by using the brake-by-wire technology. The velocity of a vehicle is controlled to track a nominal velocity which is calculated from an ideal tire-road friction model and a driver's input. However, the saturation of the tire-road friction makes tracking impossible when the slip becomes large. It is required that the control objection should be changed to prevent the wheel slip from being over a certain value. A hybrid brake system based on model reference adaptive control is designed to attain these control objectives under various road conditions. The stability of this system is theoretically proved, and then it is confirmed by simulations.

View full abstract

In this paper, a method of cooperative control between steer-by-wire system and brake-by-wire system based on model reference adaptive control is proposed. The controller can treat the tire nonlinear characteristic. The vehicle has two wheel steering (2WS) which is equipped with steer-by-wire technology, and all the wheels are equipped with brake-by-wire technology respectively. The validity of the controler is shown by the simulation based on a multi DOF model of vehicle.

View full abstract

The authors propose the concept of "Control Fusion of suspension system". The Control Fusion means the merging of functions of control for suspensions. This study aims for the realization of the fusion of control of the motion, vibration and rolling by electro-magnetic devices, and the realization of a new suspension system under control in which the five functions, sensor, actuator, spring, passive damper, and energy regeneration are merged. In addition, the evaluation platform was made and some experimental results of the electro-magnetic device were shown in this paper.

View full abstract

A suspension of a vehicle is the support system between a vehicle body and wheels. The task of a suspension is to support the vehicle body and develop ride comfort. But if the attenuation force becomes large, the passenger will feel hard at high frequencies If the attenuation force becomes small, the passenger will feel soft at low frequencies. If the coefficient of spring becomes low the vehicle's naturel frequency of vibration becomes low, thus the heave, rolling and pitching will become large. In this study, a fuzzy sliding mode controller for real vehicle has been designed. A new method about fuzzy sliding mode swich hyperplane has been proposed. Experiment results are presented to confirm effectiveness of this new algorithm.

View full abstract

In recent years, a semi-active suspension has been put into practical use in order to improve ride-comfort and driving stability of automobiles. However, there is a problem for the case of running on rough roads that temperature of the damper rises extremely because of heat generation due to friction at pistons and fluid friction at orifices at the damper. In this study, the bilinear disturbance accommodating optimal control theory is applied to the semi-active suspension and by taking the temperature rise of dampers into the design concept of the controller, a systematic design method of the controller is proposed, which maintains good balance of damper temperature and control performance. Furthermore by using gain-scheduling, an adaptive control algorithm which changes the weight between ride-comfort and temperature. As a result of computer simulation, it was demonstrated that the proposed method is useful.

View full abstract

The purpose of this study is to make a model of two-link flexible robot arms. We had used a modeling method called an 'extended reduced-order physical model (extended model)' to make a model of one-link flexible robot arm. The model of the two-link flexible robot arms is made of a combination of the model of each link that is regarded as one link flexible robot arm. To connect each link, the constraint addition method is used. This is creating method of an equation of motion in multi-body systems. The model of the two-link flexible robot arms agrees qualitatively with the experimental results. The LQI control theory is applied to the control of motion and vibration. It is verified that the results of the simulation are effective for control of two-link flexible robot arms.

View full abstract

This paper proposes a modeling method for elastic vehicles. Flexiblizing the vehicle body invites a bad influence on a degree of driving comfort or operation stability. In order to improve them, active suspension control is used. Although a model is required in order to control motion and vibration of elastic vehicles, the ordinal modeling way is difficult to apply since an elastic vehicle is in a flexible multibody system. Then, the created elastic vehicle is modeled using the extended reduced physical order model proposed by us that can perform expression of motion and vibration. In derivation of the equations of motion of an elastic vehicle, the additional constraint method is derived. Since linear control theory is used, linearization of the equations of motion of the elastic vehicle expressed by a multibody system with nonlinearty is performed. By changing the equations of motion into state space form, a control system design can be made easy.

View full abstract

Dynamic behavior of a small wiper with piezoelectric actuators, which is applied for a small CCD camera, is discussed in order to clarify the driving mechanism of it. First, the analytical governing equations are evaluated in the distributed system using the eigen function expansion techniques. Second, a flexible multibody method based on the absolute nodal coordinate formulation (A.N.C.F.) that has been proposed by Ahmed. A. Shabana et al. is introduced as a numerical test and formulated using the general augmented formulation of the equations of motion. In addition to the numerical analysis, present wiper is verified experimentally. In conclusion, the driving mechanism of the present wiper module enables us to explain the effect qualitatively and quantitatively.

View full abstract

Recently, the case that a stairs elevator is installed on from the 1st floor to the 2nd floor has been increasing along with the fulfillment of the welfare machine. This paper describes the preliminary investigation of the vibration control to secure the comfortability of a stairs elevator. A stairs elevator is considered as a movement body restrained on the three-dimentional orbit. The response vibration at the seat in the top-bottom, front-back, and left-right direction is analyzed taking the stiffness, the damping etc as parameters, and these effects are investigated.

View full abstract

The analysis of vibration of an arm and a tennis racket is important to understand the performance of rackets and the preventation of sports diseases when people play tennis. This paper discusses about the interaction among a ball, a racket, and an arm at the impact. The ball, the racket, and the arm are modeled by masses, flexible beams, and rigid links, respectively, and they are connected by springs and dampers. By coupling the dynamics of the ball, the racket, and the arm, the coupled equation of motion is derived. Finally, the parameter study is performed, and we show the results of experiments for parameter identification.

View full abstract

The "community car" has been attracting attention as a transportation vehicle aimed at increasing the comfort of and convenience of daily life in the 21st century. In addition, the spread of "silver vehicles, " marketed mainly for elderly people, has been notable recently. It is expected that the demand for small electric automobiles will increase yearly, and the development of increasingly value-added products is expected. The purpose of this study is to examine the effectiveness of active seat suspension when it is applied to small cars and the problems associated with its practical use. A small active seat suspension, which is easy to install, was designed and manufactured for one-seater electric automobiles. In an actual driving test, a test road in which the concavity and convexity of an actual road surface were simulated using hard rubber was prepared and control performance of vertical vibrations of the seat surface using sliding mode control theory during driving was examined.

View full abstract

This study focuses on a tilting railway vehicle using variable link mechanism for compensating lateral acceleration that passengers feel, and suppressing wheel load fluctuation. In this paper, feedback control using car information was proposed. Feedback controller was designed with optimal control theory, evaluating lateral acceleration and wheel load fluctuation. And, the curved track running simulation and scale model experiment were conducted with this controller. It was found that lateral acceleration and wheel load fluctuation were decreased.

View full abstract

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.

View full abstract

This paper deals with active vibration control of parallel flexible structures supported with a rigid-body rotor like a space station. In this report, authors present a mechanism that actuators are connected to the structures with long arms so that the direction of vibration in a mode differs on each structure. In this way, it is possible to control both structures effectively, even if dynamic properties of structures are identical. Computer simulation and control experiment are carried out and the effectiveness of presented mechanism is confirmed. Furthermore, authors present a modeling method that can express both motion and vibration.

View full abstract

Active control to suppress vibration of large solar panel is studied for a space solar power satellite employing tether tension. The solar panel is connected to a bus system by four tethers at the corners and tether tension is used to suppress the vibration of the panel. The mission function control algorithm is employed for the control and results of numerical analysis show excellent controlled behavior.

View full abstract

Control on lirations of a tether system is studied by employing a crawler mass, which is necessary to inspect and recover any damage on tether. The model consists of a mother satellite and a subsatellite connected through tether and a crawler mass moving on tether. The model is a simple one, the satellites and crawler are assumed to be particles and mass and flexibility of tether are neglected. The mission function algorithm is employed for the control and feedback algorithm is confirmed. Results of numerical analysis show sufficient performance of the control of librational motion of the tether system employed with the crawler mass.

View full abstract

A tethered satellite is connected with a string called tether to mother ship. Since the tether cannot be pushed, the control tension is constrained to be nonnegative. Additionally, since the tether has flexibility, its analysis is difficult. Therefore it is difficult to guarantee that the tethered satellite does not collide with the mother ship, the tether does not twine, and so on. nevertheless, it has not been discussed enough to guarantee safety. To operate the satellite safely avoiding aforementioned situations, we propose to give switching conditions for the control input. In this paper, we report about the switching control law and simulation results.

View full abstract

Attitude control of a tethered space solar power satellite is studied in this paper. The attitude is gravity-gradient stabilized with employment of tether system. The buss part connected by tether to the solar panel is treated as the proof-mass-actuator. The controllability and controlled performance is analyzed resulting in numerical simulation with sufficient capability of controlling the attitude motion of the present tethered space solar power satellite.

View full abstract

A method for reducing the angular momentum of a satellite by employing only two-dimensional impulse torques is proposed based on the zero dynamics formulation. The method is useful to recover the case when one of the nominal three thruster jets had failed or to save the consumption of propulsive fuel. The time delay is one of the difficulties in implementation of the present method. This paper shows an index for the robust stabilization of the system including the time delay. Both of the continuous-time and discrete-time systems are considered independently in the course of the analysis.

View full abstract

The present paper proposes a control scheme for position and attitude tracking of a spacecraft in order to inspect a malfunctioning satellite by maneuvering around the satellite. The proposed method is a nonlinear controller based on the exact-linearization techniques. The exact-linearization method is powerful for controlling nonlinear systems such as the position and attitude control problem treated in the present paper, because each state variable of the linearized system can be controlled independently. After nonlinear systems are exactly linearized, any kind of control method can be applied to control the systems. The Linear Quadratic Regulator (LQR) is one example of such methods that can be used for controlling the exact-linearized systems. However, from the real energy point of view, the exact-linearization method combined with LQR is not optimal, because the performance index is not an energy function and is optimized with respect to the exact-linearized state variables, which are not equal to the real state variables. In the present study, considering the rotational motion of a target satellite, position of the chaser satellite relative to the target and the period of rotational motion of the target satellite, the energy consumption for the fly-around motion using the exact-linearization is optimize. The effectiveness of the proposed method is verified, in comparison with the exact-linearized method with LQR and the adaptive exact-linearized method with LQR, through numerical simulation.

View full abstract

In this paper, we propose the model based height control and a method of automatic controlled taking-off and landing for autonomous small unmanned helicopter. Our research group realized autonomous attitude, position, height and hovering control. But, when helicopter makes a take-off and landing, we operate by manual control. In order to realize the full automatic controlled small unmanned helicopter, we have to realize automatic controlled taking-off and landing. Height controller require high performance to attain the purpose, so we apply LQI controller and model tuning approach for small helicopter system by using simple mathematical model. Besides we design new attitude controller to make a taking-off and landig in safety. We apply the new height and attitude controller for small unmanned helicopter, and inspect that they can realize automatic take-off and landing.

View full abstract

In this paper, we propose a method to design a nonlinear simulator for a small scaled unmanned helicopter. The main bottleneck in enhancing the control accuracy of the autonomous flight is not having a accurate dynamic model for the helicopter. Change of moment of inertia of the helicopter due to the rotation of the rotor. interrelationship between each axis due to the gyroscopic effect, nonlinearity of the control inputs to the helicopter are some effects wich has to be considered to obtain a better dynamic model. In our approach we do the initial modelling using 3D cad software (Pro ENGINEER), then do the simulator design using a dynamic analysis software (DADS). Using this nonlinear model we do the flight simulation using previously designed attitude controller in MATLABs SIMULINK.

View full abstract

This paper deals with an active vibration control of a new smart board designed by mounting the piezoelectric fibers with metal core on the surface of the CFRP composite. These complex fibers function as sensor and actuator in the CFRP board A finite element model of a cantilever and a reduced order model for controller design are established. The piezoelectric fibers each have unevenness in the actuator outputs. Therefore, the liner fractional transformation (LFT) is formulated considering the unevenness of the actuator outputs as the perturbation. Next, the controller considering the perturbation and the robust stability is designed by using μ synthesis. The control performance of the proposed method is verified by experiment and it is shown that the use of piezoelectric fibers is effective in the vibration control.

View full abstract

The high precise measurement of vibration and the efficient control system are indispensable to suppress the vibrations occurring to large-scale flexible structures. This paper discusses about the measurement and the control system using the modal sensor/actuator, which are composed of accelerometers and PZT. In a design of modal sensor, accelerometers are placed on the optimal locations obtained from the minimization problem observation spillover. In a design of modal actuator, a location of PZT elements is optimized by the minimization criterion of control spillover, and the optimal control gain is determined by LQR control theory to consider both the effect of control and the control energy. Numerical and experimental results of vibration measurement/control using a cantilevered CFRP plate with accelerometers and PZT elements have been demonstrated to verify the validity of the proposed modal sensor/actuator.

View full abstract

Vibration control of a flexible beam using piezoelectric film sensors and multilayered actuators is investigated. At first, the method of multilayered piezoelectric actuator is proposed for the purpose of improvement in vibration control effect against relatively thick structure. In the proposed technique, multilayered piezoelectric films are connected in parallel electrically and are driven simultaneously by the control voltage. Then, multilayered actuator is actually applied to a cantilever beam and by measuring the amplitude of semi-static displacement at the tip of the beam, it is shown that the actuator force generated by the proposed miltilayered actuator improves for the same magnification as the number of films. Finally, proposed method is applied with the piezlelectric film sensor to the transient vibration control of the cantilever beam and it is verified that the vibration control effect actually improves and the theory agrees well with the experiment.

View full abstract

This paper aims at presenting the structural vibration suppression capability of the recently developed Macro-Fiber Composite (NASA LaRC-MFC^<TM>) actuator as a passive piezoelectric absorber using an inductive resonant shunt circuit. The resistance and inductance of the series RL shunt circuit are designed by the analogy with the single-degree-of-freedom mechanical damped vibration absorber and by using the maximum power transfer theorem of the electric network. Experimental test of a simple cantilevered beam demonstrates that the MFC actuator has excellent capability of improving the dynamic response of the beam as a piezoelectric damping system. The damping enhancement performance of the MFC actuator is superior to that of the conventional monolithic PZT actuator.

View full abstract

This paper describes a modeling of a smart flexible beam composed four piezoelectric materials due to detect the failure, for example, the damage of piezoelectric materials and the breaking wire. Model of the smart flexible beam in case of the failure is expressed by a linear parameter varying system. The output matrix of the object system is affected by damage of piezoelectric materials and breaking wire. Subspace state space identification is adopted in order to detect the failure. Numerical simulation indicates that the failure detection is possible by using proposed method.

View full abstract

This paper presents a quantitative structural health monitoring technique to evaluate tensile force in a thin beam and stress field in a thin plate. This technique is based on the smart structure concept, which a piezoceramic material (PZT) bonded on the surface of a structure works simultaneously as an actuator and a sensor. To evaluate the stress state inside a structure, electrical impedance before and after applying tensile force are measured. Based on the wave propagation theory, a structural model of the beam containing the PZT is formulated and the measured electrical impedance is derived analytically. A tensile force identification method in the beam is proposed by using an optimization technique. For a plate case, FEM model is used in formulation. With experimental verification, it is found that the analytical results and the tensile force in beam case can be identified with accuracy. By using the proposed method, it is possible to identify value of the tensile force in a thin beam from only one measurement.

View full abstract

This paper describes the active vibration control of a plate using a self-sensing actuator (SSA). In self-sensing actuator, the same piezoelectric element functions as both a sensor and an actuator, so that the total number of piezoelectric elements can be reduced. Many studies have been reported on the application of self-sensing actuators to the vibration control of beams. In this study, the application of self-sensing actuator was extended to the active vibration control of a plate. The adaptive filtered-X LMS algorithm is adopted in the control. The effectiveness of the control method was confirmed in the experiment, and the results show that the vibration level is considerably reduced at many peaks.

View full abstract

A smart structure is composed of the piezoelectric film sensor and actuator in order to reduce the structural vibration. H_2 controller is designed with the reduced order model of the smart structure which is obtained by finite element and modal analyses. The control force is applied by the piezoelectric film actuator and the feedback signals are detected by the piezoelectric film sensor and the accelerometer in the system. The vibration response is suppressed by the modal control in which the modal coordinate displacement is taken as the controlled variable. The shape/placement of the piezoelectric actuator and the H_2 control system are simultaneously optimized by SQP method and genetic algorithm to achieve an enhanced vibration control performance. Efficient optimization algorithm based on a two-step procedure is employed in the simultaneous optimization. It is verified by some applications that the enhanced performance for the vibration suppression can be achieved by the presented optimal design.

View full abstract

In actively controlled cantilevered pipes conveying fluid the critical flow velocity depends not only on the structural property of the pipe but also the feedback controller. In this report we discuss an integrated design of a cantilevered pipe conveying fluid to optimize both parameters in the pipe system and the controller in simultaneous manner. The pipe is composed by a beam with variable width and two pipes conveying fluid attached on both sides of the beam. The beam is divided into several parts and the width of each part can be independently adjusted so as to obtain the higher closed-loop critical flow velocity. This means that the resulted beam has a stepped form after the optimization The location and the number of the division of the beam are determined by the sign distribution of the sensitivity function of the critical flow velocity on the small width change of each divided part of the beam. The effectiveness of the proposed design methodology is justified by a simulation study.

View full abstract

This paper considers a problem of designing a control system for displacement expanders of magnetic recording test stands. Dynamic characteristics of the actuator for the expander have been analyzed by finite element method, and the vibration modes are evaluated in connection with the controllability and observability of the control system. A treatment of the plant uncertainty and the closed-loop performance is discussed in terms of the integrated design of the structure and controller. It is shown that there exists a trade off between the nominal performance and the robust properties in the design.

View full abstract

This paper considers a design method for plant/controller in gain scheduling control scheme. An identification method is used on-line for tuning the scheduled parameters in the controller. Because of the structure of the identification method, we can evaluate the sensitivity of parameter change in the plant. We can optimize the design using this sensitivity in the sense of integrated design of plant/controller.

View full abstract

This paper is concerned with simultaneous optimal design of adaptive structures consisting of structural and control systems. In this paper, we use the fact that the nonconvex problem is approximated by a convex one by adding a semidefinite positive function, so-called a convexifying function, to make the constraint convex. This paper proposes a method of simultaneous optimization for state feedback gains and structural parameters. The system formulation is given using the descriptor form representation of the plant under the LMI (Linear Matrix Inequality) constraint. A simple numerical example of a flexible beam structure is given to demonstrate the effectiveness of the proposed method.

View full abstract

This paper describes a new levitation control method of linear magnetic bearings for a linear arm in clean robot without any mechanical contact. The linear arm consists of a slender beam like a ladder and carries a silicon wafer on a tip. It is levitated by linear magnetic bearings and is driven by a linear stepping motor without any mechanical contact. A new control method for the linear active magnetic bearing is applied for its levitation, in which the bias current of each magnet is changed according to the distance between the center of the bearing and the center of gravity of the arm. The experiments have been carried out on the levitation control while the arm is moved by the linear stepping motor. The experiment shows that the arm is levitated and moves smoothly without any mechanical contact.

View full abstract

An experimental apparatus is developed for study on a new magnetic suspension method in which the attractive force of a permanent magnet is adjusted by a flux path control mechanism. The apparatus has a two-dimensional flux path control mechanism that enables the three-dimensional positioning of the suspension object. It is shown experimentally that the developed apparatus can achieve such positioning control.

View full abstract

This paper describes a control method of magnetic levitation system which uses actuators and permanent magnets. The control method is pseudo zero power control, in which there is a little power loss during the system is operated near the equilibrium. As the adjustment of the air gap length varies the suspension force and stabilizes the system, the zero power control can be achieved by such as a spring force. First an experimental device is introduced and the principle of levitation is explained. Numerical simulations for the zero power control are carried out based on the model of the device, and some experimental examinations are shown.

View full abstract

This study proposes an adaptive unbalance disturbance control for a zero-power magnetic bearing system based on a Fourier coefficients algorithm which generates the synchronous compensation signals. The proposed adaptive algorithm does not need any plant model of the AMB system for disturbance cancellation. The compensation signal generated by adaptive algorithm is added to sensor signal to attenuate the unbalance disturbance. The adaptive algorithm is experimentally verified and a high degree of unbalance response attenuation is achieved.

View full abstract

In a bearingless motor for vibration suppression of a flexible shaft, a control system of a suspension part can be simplified. In this paper, it is shown that induced voltage at suspension winding terminals, caused by mutual couplings between motor winding and suspension winding, provides current flow in suspension winding, generating damping and spring forces, which suppress flexible shaft vibration. Controllers and inverters are not required at suspension terminals but these terminals are simply short-circuited.

View full abstract

In this paper, test results on an induction type bearingless motor driven by a general-purpose inverter are reported. The behavior of the motor is shown when parameters like carrier frequency, starting frequency, and torque boost of a general-purpose inverter have been changed to see magnetic suspension characteristics.

View full abstract

This paper proposes a new type of self-bearing motor which uses Lorentz force. It is expected to have good dynamic response, and high levitation capability. For realizing high magnetic flux in airgap, Halbach magnet is used for the rotor. First, the fundamental principle is introduced how the motor produces rotating torque and radial levitation force. Next, Halbach magnet is introduced. Then the motor is designed and its radial levitation force is calculated using FEM. Finally, the experimental setup is desined and discussed.

View full abstract

Recently small magnetic bearing is widely requested for small rotary machines. Standard active magnetic bearing (AMB) has problems of low efficiency and temperature rise. Hybrid (HB) type AMB can improve these problems. However, the traditional HB type AMB has bias permanent magnet between the two radial magnetic bearings. This structure requires long magnetic circuit causing heavy casing and flux leakage. This paper proposes smart HB type AMB which has internal permanent magnet inside the radial magnetic bearings. The fundamental principle is introduced, followed by the design of the experimental setup.

View full abstract

This paper deals with modeling and design of control system for motion and vibration control of flexible rotor using active magnetic bearings (AMB). The goal of this research is to pass through a critical speed and achieve high-speed rotation. One of the most problems is the cross-coupling effect caused by gyroscopic. To achieve this goal, it is necessary to make model that can express to high order flexible modes and to gyroscopic effect. Thus we apply an extended reduce order physical model method that can express motion and vibration simultaneously to rotor-AMB system. Further, we propose controller that combined PID with LQ control to motion and vibration control. The effectiveness of made out model and designed controller is approved by simulations.

View full abstract

For thin steel plates which are used in many industrial products including those of the automobile industry, we have proposed a magnetic levitation control system and confirmed its realization by means of a the digital control experiment. However, in the case in which only the levitation control is applied to the steel plate, it has no horizontal restraining force on the direction of travel. Therefore electromagnetic actuators are installed in order to control the horizontal position movement of the levitated sheet steel. The electromagnetic attractive control forces of the actuators are given for the two facing edges of the levitated sheet steel, from the horizontal direction. In this paper, the suppression effect of elastic vibration of levitated sheet steel in the horizontal noncontact position is reported. Moreover, we have examined the suppression effect of elastic vibration by placing permanent magnets, which have no operational costs, at locations devoid of the electromagnets used to control the horizontal position of the steel plate. The results of experiments showed that the elastic vibration of the sheet steel could be sufficiently reduced.

View full abstract

The continuous thin steel plate subjected to iron and steel processes is supported on a series of rollers during processes such as rolling; the thin steel plate moves on the rollers at a speed of 10 m/s or more. In the plating process, the steel plate is conveyed 20-50m in the vertical direction for drying, during which the steel plates are negligibly supported by rollers and other mechanisms. Therefore, plating nonuniformity due to the generation of vibration and other reasons prevents the increase of productivity. To solve this problem, we developed a new noncontact guide system for parts of the steel plate at which its traveling direction changes by applying an electromagnetic force from the direction of the edge of the thin steel plate, and experimentally examined the effectiveness of the system.

View full abstract

In this study, we propose a contorl method based on the virtual suspension model in order to keep the posture stability of body when robot walking on terrain. Firstly, we built a CAD model of a six-legged walking robot for studying rough terrain walking. Nextly, we designed a vibration system with one degree of freedom, which has virtual spring and damper, in the direction of the vertical, the pitch angle, and the roll angle of body respectively. And then, considering of active control input and disturbances from the collision control that decrease tremble of body using sliding mode control can be realized. Moreover, the efficiency of this sliding mode control based on the virtual suspension model is shown by 3D CAD simulation of walking on terrain with obstacles.

View full abstract