[in Japanese]

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To suppress external vibration for a hard disk drive shock sensor feed forward techniques are proposed. To design the feedforward controller phase approximation is important. In this paper a method to design a Finite Response Filter (FIR) type controller with phase constraint is proposed. The result is compared with the method which does not use the phase constraint. For the filter with small order the proposed method can approximate the phase better.

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Owing to 300mm wafer application, semiconductor lithography equipments have become large. At present, it is difficult to design a fully rigid base-frame within the limited weight restriction. The aim of this paper is to propose a method of compensation for the stage position measurement error occurred by the elastic deformation in the base frame. First, we show, by analysis and simulation, that the method improves the stage positioning accuracy. Next, we show by experiment that the standard deviation of the stage repeatability if improved from 9.4nm to 4.5nm. We show also that this method is effective in making semiconductor lithography equipments lightweight.

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For a first access control, it is effective to reduce the power spectrum density (PSD) of feedforward input in the frequency range where the mechanical resonance modes of the plant exist. We have shown that these feedforward input can be easily obtained using a final-state control method with a certain weighting function. However, if these resonance modes have damping and it cannot be neglected, the feedforward input can be optimized considering the effect of damping of the resonance modes. In this paper, we propose a design method of feedforward input which is optimized for resonance modes with damping. This method is applied to the track seek control of hard disk drives, and the effectiveness is shown by simulation.

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System identification results of a magnetic suspension and balance system (MSBS) are presented in this study. A model to describe the system behaviors is a linearized equation of motion of the MSBS. Conventionally, unsteady aerodynamic forces have been estimated using the equation of motion and individually measured model parameters, however, it has not been confirmed the validity of the model in detail. In the study, the model parameters are identified from experimental data, and it is confirmed the linearized equation of motion with the identified parameters is valid for simulation of the model behavior and measurement of unsteady aerodynamic forces.

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This paper describes a novel type of magnetic suspension system with a permanent magnet and a rotary actuator. The feature of this suspension system is that a rotary actuator controls attractive force. Varing the angle of the permanent magnet driven by the actuator changes magnetic flux path in the suspension system and controls the suspension force. The merit of this suspension system is that the attractive force of this magnetic circuit can be made to be zero. Moreover this system can change the polarity of stator poles. First an outline of the suspension system will be described. Next, the principle of the suspension mechanism will be explained. To verify the feasibility of the proposed system, some basic experiments and a numerical simulation will be shown.

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Major objective of this paper is to develop the design method of sliding mode controller for a nonlinear electromagnetic levitation system and to verify the validity by carrying out the experiments. The system is governed by a set of a nonlinear second-order motion equation and a nonlinear first-order electromagnetic equation. The design procedure of a switching function is based on the stability of the system zero dynamics with respect to motion. Results of several case studies for the initial response are shown to discuss the present design method in advance of the experiment.

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The sensitivity function of feedback control systems is recommended for AMB (Active Magnetic Bearing) rotors to evaluate the stability margin. However, we need to predict the Q-value before rotor operation. In this paper, the sensitivity and the Q-value are discussed and the difference is made clear. How to obtain the Q-value from the open loop transfer function is also discussed. In this experiment the open loop transfer functions of the AMB system controlled by the mode separation control method was measured. Q-value peaks measured by open loop transfer functions agreed with Q-value calculated by closed loop transfer functions which is commonly used.

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In recent years, Active Magnetic Bearings (AMBs) characterized by non-contact support without mechanical loss have been applied in industrial rotors. The Purpose of this research is to pass the 2nd bending critical speed in the flexible rotor supported by AMBs. This paper deals with the following topics about AMB over-hung rotor system: (1) Method of controller design based on the phase adjustment method and the evaluation results by using sensitivity functions, (2) Evaluation results by using Q-value function (new method), and (3) Application of modal balancing method and passing the 2nd bending mode for rotational speed.

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An energy storage flywheel is considered as one of the most effective methods to improve the efficiency of the electric power plant. For such a high speed and long term application, however, the eddy current loss in the laminated steel sheet is still induced. This paper proposes a new type of magnetic bearing which is expected to have almost zero eddy current loss. In order to test the energy storage system with proposed magnetic bearing, a small flywheel is designed. The designed flywheel is fabricated and installed to the proposed magnetic bearing. In order to clarify performance of this flywheel magnetic bearing, fundamental characteristics are measured. The rotor could run up 5,200 [rpm] without any serious problem.

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High-speed motor drive for turbo compressors is becoming attractive, but there is a rotor dynamics problem due to the lowered bending mode frequencies. In order to support such flexible and high-speed rotating shaft, active magnetic bearing will be one of the solutions. In this paper, the design and test results of active magnetic control system for a high-speed turbo compressor that has two impellers and a motor on a single shaft are presented. In a digital control, a large phase lag in high frequency domain cannot be avoided. For this disadvantage, a practical controller design that use phase shifting filters is presented. In addition to this, a synchronous filter that has an arbitrary phase property at the reference frequency is applied to the controller to cross over the first bending critical speed. Adopting these control methods, very stable operation at the rated speed of 55,000min^<-1> is realized.

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Maglev pump is widely requested for artificial heart or chemical industries. Hybrid magnetic bearing is recognized as an high efficient one even with wide airgap and is suitable for such applications. This paper proposed two types of hybrid magnetic bearing for maglev pump. The results of magnetic field analysis for internal permanent magnet (IPM) type one are introduced. Then the experimental setup and its fundamental characteristics are explained. The results show stable levitation, but it has dynamical problems. To improve dynamic characteristics, control system has changed from local to centralized PID controller. The results show promising characteristics for practical use.

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This paper proposes a new structure of the interior permanent magnet (IPM) type self-bearing motor to realize self-sensing control technique based on the principle of differential transformer. Main flux (d-axis) directional permeance is different from its orthogonal (q-axis) direction because of the salient pole property in the IPM type motor. It means that the radial direction displacement information is not detected simply from the mutual inductance independently. Magnetic field analysis using finite element method was carried out to determine the location of the interior permanent magnets of the rotor. Prototype IPM self-bearing motor was designed and fabricated from the analyzed results. This IPM rotor structure is expected to realize self-sensing control.

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In this paper, we consider designing of a FDI filter to detect faults of sensors which are used in an active control system. Required capabilities of FDI filters are sensitivity of occuring faults, and robustness against modeling errors or disturbances. In many cases, there are small discrepancies between a real system and its model in space systems. Thus, effects of disturbances provide serious problems for designing a FDI filter. In this paper, we consider to design a FDI filter by using H∞ filterng technique. Performance of designed FDI filer is demonstrated by some experiments.

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In this paper, we propose a design method of a disturbance-accommodating gain-scheduled control taking account of actuator saturation by seismic excitation in vibration isolation for a multi-degree-of-freedom structure. A disturbance model multiplied by an envelope function is introduced for disturbance-accommodating control in order to represent the nonstationary characteristics of seismic disturbance. We formulate a linear parameter varying system according to the amplitude of the disturbance as well as the controller output, and design a gain-scheduled controller. By carrying out simulations and experiments of seismic excitation, it is verified that the proposed controller can maintain the performance of isolation even if a large earthquake with which actuator saturation occurs comes.

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It is well known that an inverted pendulum system can be controlled by only horizontal input from the view point of its equation of motion. But it seems to be possible to enhance control performance by using vertical input like human beings keep the rod in upright position on their hand. So this paper deals with non-linear control problem of the inverted pendulum using vertical movement in addition to horizontal movement and two main results are proposed to handle this problem. First one is derivation of coordinate and input transformation so as to convert equation of motion of the inverted pendulum system into simple bilinear system. Secondly LMI conditions to solve Hamilton-Jacobi inequality for non-linear H_∞ control problem are derived. Finally these results are confirmed through numerical simulation.

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In this paper, we discuss an aerial posture control problem of a 3-link horizontal bar robot with nonzero initial angular momentum. Two joints of the robot can be controlled under the in-phase or out-of-phase constraint. We already succeeded in realizing 3-link aerial robot control under the in-phase constraint in our previous study. In this paper, we show a way to control the robot under the out-of-phase constraint. First, the law of conservation of angular momentum is shown and an error equation based on two angular velocity inputs is derived for a 3-link aerial robot. Next, the necessary condition which assures the existence of the control low under the out-of-phase constraint is derived. A feedback control law is derived by the backstepping technique which guarantees Lyapunov stability of the error system. The feedback control input is calculated numerically by solving a fourth order equation. Finally, simulation results are presented to show validity of the proposed control strategy.

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This paper deals with a passivity-based approach to wide area stabilization of the magnetic suspension systems. The magnetic suspension systems have strong nonlinearity. In order to take the leakage inductance of the electromagnet into account, we design the controller considering the leakage inductance of the electromagnet. The systems can be decomposited two subsystems, electrical subsystem and mechanical subsystem. We design a nonlinear passivity-based controller for each two subsystems. Steady-state and transient experimental results for some operating points show the effectiveness of the proposed method.

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For cars without side skidding in their wheels, steering control based on time-state control form and exact linearization technique can achieve globally asymptotically stable tracking. But real cars always experience side skidding; their behavior depends on their velocity, roadbed and property of wheels. For this challenge, we have proposed a modified steering controller by inverse dynamics of vehicle with side skidding. Our controller assures exponential asymptotic tracking to the desired trajectory. In this paper, our steering controller is extended to the 4WS vehicle to achieve both the tracking control and the attitude control of the vehicle. Base on this extended controller, we realize an automatic deceleration method using active toe-in angle control.

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In this paper, a design of the state predictive model following control system with time delays and disturbances is discussed. The design of the control system is constructed using the easy algebraic algorithm of matrices whose elements are polynomials of the three kinds of operators. Boundedness of the inner states for the control system is given and the utility of this control design is guaranteed. It is confirmed on basis of a numerical example that the output signal of the control system asymptotically follows the reference model signal in the case of the existence of disturbances.

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This paper deals with an H_∞ DIA control for the magnetic bearing considering periodic disturbance via rotor unbalance. H_∞ control problem which treats a mixed Disturbance and an Initial state uncertainty Attenuation (DIA) control is expected to provide a good transient property and a good rotational performance. In this paper, we propose an H_∞ DIA control system design in order to attenuate the periodic disturbance of the magnetic bearing caused by the vibration of rotor unbalance. In fact, this H_∞ DIA control system design can obtain a controller by adding a frequency weighting function in generalized plant. Then, we carry out an experiment in order to validate proposed control system design by switching control. Switching control consists of two proposed controllers and a switching logic, it can be switched at a certain rotational speed. Finally, experimental results show that the proposed robust control approach is effective for improving rotational performance.

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This paper presents a new control strategy based on the sliding mode control theory. The controller is designed so that the state trajectories of a plant will stay close to a switching surface in a certain future time, not stay on it at the present time. To this end, the future value of the switching function is evaluated with the prediction of the plant state and disturbances. As a result, a discontinuous input with a time-varying gain, which is adjusted in every prediction interval based on prediction is introduced.

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In order to operate a train efficiently at high speeds regardless of the number of composed vehicles, control systems that can provide stable braking forces must be developed. In the design of brake control system, it is quite important to consider the robustness because there are model uncertainties which result from nonlinear characteristics for adhesion between wheel and rail, and friction coefficients of brake materials. This paper will present the experimental results about the new wheel slip prevention control designed by sliding mode control theory. The experiments for the proposed wheel slip prevention control are performed while comparing some conventional control laws. The experimental results proved the effectiveness of the proposed control as compared with conventional ones, and showed the high brake performance under nonlinear characteristics of brake dynamics.

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This paper describes the evaluation of direct yaw moment control with EV Kart. We have developed EV kart that has two motors and independent wheel drive mechanism. Each motor is controlled by PIC microcomputer, and its yaw moment is controlled by the right and left traction force. Various sensors such as acceleration sensor, velocity sensor and steering angle sensor are equipped with this kart. This control was evaluated by carrying out computer simulation and running test with EV kart

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This study aims at a system to measure 6 force components acting between a tire and the road surface by measuring strains in the wheel of the tire module. The measurement method was developed based upon the least square method. Dynamic tests were carried out, showing effectiveness of the method. It is expected that the real time measurement of the 6 force components will greatly improve performance and reliability of the vehicle dynamics control system.

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This paper presents study on suspension control for heavy-duty trucks considering road holding ability with variable damping shock absorber. In heavy-duty trucks, the large payload, changing in the wide range, causes unstable vehicle behavior such as rollover. So, variable damping property is necessary. In order to reduce the cargo vibration and improve the road holding ability, linear functions of the damping ratio are introduced and examined, which are represented as functions of loading ratio. Next, with results of linear analysis, a nonlinear damping force characteristic is proposed. The nonlinear damping force characteristic has high damping coefficient around zero stroke velocity and low damping force level in the range of high stroke velocity. It is found that the proposed nonlinear damping force characteristic is effective for the compatibility of the vibration isolation and road holding ability.

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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 design a controller for an active suspension in consideration of rigidity variation of the spring at the stroke end by applying sliding mode control. By carrying out simulations for a quarter-car suspension model the performance is verified. We also design Kalman filter in consideration of nonlinear force occured by rigidity variation of the spring when the suspension reaches the stroke end.

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The air suspension system is now widely used for railway vehicles. To improve the riding comfort of vehicles equipped with this system, we tested semi-active control system of air suspensions having a variable orifice which is installed between air spring and auxiliary air chamber, and is controlled by a controller designed based on the H_∞ control algorism. Numerical simulations and excitation tests using a 1/2 carbody on rolling stock testing plant are carried out. The results show that the proposed system reduces effectively the power spectral density (PSD) of acceleration of the carbody floor, and there is observed little difference in the effectiveness of vibration mitigation between the case of using a reduced-order controller and the case of using the original one.

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In recent years, railway vehicles are becoming lighter since it corresponds to improvement in the running speed. However, this affects a degree of ride comfort as increase in bending vibration due to the deterioration of the body rigidity. Recently, the piezoelectric element are paid attention as the actuator for structures in order to control vibration. This is referred as the smart structure concept. A piezo-electric element has characteristic that is small, light and high output. Therefore, the objective of this research is to reduce bending vibration by embedding piezo-electric elements in the body. In addition, an active control is applied to the secondary suspension, and the rigidity vibration of the car body is reduced. Vibration control performance is investigated by computer simulation and experiment with 1/6-scale experimental setup.

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This paper describes evaluation of adaptiveness of human-vehicle system by running test. We have evaluated response properties of the kart obtained by pulse response running test. In order to discuss about response properties of human-vehicle system, we also have carried out lane change test. By comparing the results of these tests, it can be observed that driver's maneuver changes according to vehicle dynamic characteristics.

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In this paper we propose active control of shock to defend passenger legs in vehicle collision. Although it is possible to decrease the load to the passenger legs in vehicle collision by using a knee bolster with an elast-plastic element, active control may be adaptable to the various situations of the collisions. In order to suppress the contact force between the passenger knee and the knee bolster, Linear Quadratic Integral (LQI) control is applied. Also we arrange a passive damper in parallel with the actuator. By carrying out simulations, it is verified that the introduced knee bolster is more effective than the previous among wide range of collision speed.

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This paper deals with motion and multi-modes of vibration control of a flexible transportation system. In order to reduce a settling time from one position to another one, the vibration control is remarkably important on the transportation system. Since transportation system moves long distance, no limit in the measuring range of the sensor is required. For the purpose, piezoelectric films pasted on flexible structures are used as the point sensor to detect vibrations. To control the first two vibration modes, the reduced-order physical modeling method proposed by authors is applied and the control system is designed by LQ control approach. Control experiments demonstrate that the settling time is well shortening by controlling many-modes of vibration in addition to motion.

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This paper presents the effective and practical method for experiments of comfort evaluation of trains using a motion simulator. The experimental plan was considered from various viewpoints such as cabin vibration condition, the questionnaire sheet, passenger situation, reality and total efficiency of the experiments. From the experimental results, it was confirmed that the experimental method was effective and had various merits for evaluation rather than the case of actual trains such as the reproducibility of the cabin vibration and setting of many conditions which are difficult for real vehicles.

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In this study, the triaxial force tactile sensor, which has 12 sensor elements that can detect vertical force and shear force, was proposed. Here we produced prototype sensor five times larger than those to be used in practice. The sensor elements detect vertical force and shear force as changes in electric resistance on a strain gauge. The measuring accuracy of the sensor element is 5.0%RO in the X and Y axes direction and 2.0%RO in the Z axis direction. Then, the output algorithm that can distinguish and detect translational and rotational slippage was created. Translational and rotational slippages were distinguished by the direction of vector of shear force that acts on each sensor element Translational slippage was detected by the movement of center of pressure, and rotational slippage was detected by evaluating the principal axis of inertia of a contact pattern. Effectiveness of the output algorithm was shown by experiments.

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In this study, rheometers for MR fluids were developed. The shear stress were measured on changing the condition of flow rate, types of MR fluids, magnetic flux density, and gap through which MR fluids flowed. The response time of the MR fluids on the flux density were also measured. Using these experimental results, the force and the response time of devices using MR fluids were modeled. And we also suggested a new type of engine mount, in which the rotation of the engine is controlled using the mount. By controlling the damping force, the shock force among the parts was homogenized and the peak value of the force was reduced.

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This paper presents a nonmetallic and light robot finger using low-pressure driven pneumatic actuators developed by us. Recently, there is much robot research into coexistence with people and helping them. Such robots must be considered safe for contact with people. The drive system of our proposed robot hand uses low-pressure driven pneumatic actuators originally developed in consideration of safety for human contact. The results of the characteristics of the pneumatic actuator proved that it is possible to drive die robot hand and get enough generated force to grasp objects by lower inner pressure and lower air volume. Therefore, a model fee same size as a human hand can be made without a big air compressor, and applications for prosthetic hands are considered.

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This paper proposes a new type of absolute displacement and velocity sensor based on the principle of servomechanism. Because measuring range is over natural frequency, it is difficult to realize seismic system sensors with low frequency range to measure. In order to expand measuring frequency range, sensor with the low natural frequency is realized by using feedback control techniques. It is shown that the sensor with small size and lightweight have a low frequency measuring range. To construct such a sensor, we try to use both analogue and digital controls. This sensor is used for controlling vibration using active dynamic vibration absorber.

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Inner disturbance compensation is required for high accurate attitude control of spacecrafts. In this paper, an active inner disturbance accommodation filter based on the minimal-order observer is studied, which is useful to estimate and eliminate the inner disturbance. And MDM/MDP method is applied to the feedback control, where MDM/MDP method is one of the robust control strategies to prevent spillover instability. These methods are verified through experiments with a satellite free test bed and numerical simulations.

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The satellites in formation flying are close to each other within some hundreds of meters. However the Earth's oblateness effects make the satellites in formation apart. The solar radiation pressure can be used to maintain the formation. The wing area to cancel the Earth's oblateness effects is analyzed and propellant mass for ion engine corresponding the solar radiation pressure is estimated.

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This paper deals with the active vibration control with twisting vibration. The control objects are flexible plates like solar array panels supported by a rigid-body rotor like a space station. Two flexible plates are connected with each other through the electromagnetic actuators fixed with the flexible arms. As a vibration control mechanism, the method using the interactive force between structures is applied for vibration control of these plate structures. Then, these structures are expressed by the lumped parameter system "4-DOF model" using the reduced order physical modeling method. To prevent so-called spillover, a second order low-pass filter is built in the control system. The LQ control method is used to obtain feedback gain. Computer simulations showed the effectiveness of presented control method.

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This paper discusses on guidance and control law for an unmanned lunar landing module. The guidance law is required to avoid obstacles on a lunar surface automatically during vertical descending. The main thruster of landing module is used not only for deceleration of descending rate but also for avoidance maneuver. Thus the avoidance guidance law is required to complete the maneuver during main thruster firing. The main purpose of this paper is to show the relation between thruster delay and the landing accuracy through numerical simulation. The results show that the delay time of main thruster affects the accuracy of vertical landing rate. The requirement of landing accuracy, however, is satisfied for the main thruster with common performance.

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This paper presents the optimal model for model based control of small-scale unmanned helicopter. We designed a multi-input/multi-output model of small-scale helicopter which refer Mettler's model, and we identified this model by frequency domain identification. Frequency domain and time domain validation results have shown that identified model can describe actual dynamics of helicopter, and we derive simple SISO model based on this MIMO model, so we prove experimentally that this SISO model is optimal model for model based control of small-scale unmanned helicopter.

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A cluster of small-sized single-gimbal control moment gyros (SGCMGs) is proposed as an attitude control actuator for high-speed maneuver of a small satellite. The singularity of the system of 4-SGCMGs in pyramid configuration is analyzed and the distribution of singularity surfaces is visualized. This paper also presents a new singularity avoidance control logic using the singular value decomposition algorithm. The effectiveness of the present singularity avoidance control logic is demonstrated with numerical simulations for a large angle maneuver of a small satellite.

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In this paper, a control method for shifting of gears of a four-wheeled vehicle with the manual transmission is proposed and is verified by 10.15 mode driving on a chassis dynamometer. By switching the two degrees of freedom system to the one degree of freedom system when the gear reaches the synchronizer mechanism, shifting of gears is achieved. An automatic driving of 10.15 modes on a chassis dynamometer is performed for a four-wheel vehicle with manual transmission controlled by the MT shift actuator. Also, 10.15 modes driving by a skilled driver in the same vehicle are performed. It is verified from comparison among experimental results that shifting of gears by the switching control proposed is in good agreement with that by the skilled driver.

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