In many cases, control system design is formulated as minimization of some prescribed closed loop performance reflecting a control requirement. Since the closed loop performance is a function of a controlled plant and a controller, the model identification and controller design must interact with each other. This motivates us to consider the model identification and controller design simultaneously. However, most of the previous joint design methods are not applicable to unstable plants because the identified plant model is usually used as the design parameter, i.e. a weighting function in the controller design. On the other hand, we have analyzed the internal structure of 2DOF control system using coprime factorization on RH_∞ and shown that two free parameters, K and Q ∈ RH_∞, specify tracking performance and feedback performance, respectively. Also, Tay et al. have proposed a parameterization of the plant dynamics by switching the role of the controlled plant and controller, and introduced a free parameter R ∈ RH_∞. In this paper, we propose a new joint design strategy based on the identification of R and the design of Q. Since the identified plant parameter R is always stable, the proposed joint design strategy can be applied to wider class than the conventional joint design methods. Moreover, it is known that R is well approximated as a less order model than the plant itself. This leads to the advantage in designing Q with less order. Finally, the usefulness of the proposed method is verified by some simulations and experiments.

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In this paper, we propose flexible shoe system to apply passive walking manner to ordinary humanoid biped. In this system, 2DOF (FF & FB) control scheme is used and realize walking with less ankle torque. Besides, this system is consisted as reference modification of position control system, so it can be applicable to most of walking robot even if its joint servo is black box. The effectiveness and characteristics of this system is confirmed by computer simulations and experimental result. The softness of shoe is very important parameter for energy consumption and walking stability. From the discussions of the system, it is said that sagittal plane assistance shoes reduce the energy loss due to the ankle joint friction. Finally, we confirmed the reduction of energy consumption on walking experiment, so we call this system as “energy saving shoes.”

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This study is about an attitude control device applying flywheels. Reaction torque of a flywheel is applied for oscillation suppression of a suspended load. We suggest a sensorless estimation method of the attitude angular velocity. The band pass filter extracts the component of oscillation velocity from flywheel rotation velocity that contains various kinds of errors. A disturbance observer eliminates the steady state error on the wheel. Since the disturbance observer is for low frequency range, it does not interfere to angle velocity estimation. This attitude control device is convenient because it needs least calibrations when it is remounted on various suspended loads. The experimental result shows the validity of angle velocity estimation and the validity of oscillation suppression.

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This paper describes an accurate position control in object coordinate. In case the motion control of industrial robot placed in global coordinate is considered in object coordinate, it is preferable and convenient to decide its motion by the teaching of robot operator. However the teaching procedure requires much time and effort. Moreover, as often as relative position between robot and object is changed, the operator needs to do the teaching operation again. To improve the above issue, it is required to develop the strategy that decides the robot motion without the teaching operation. This paper proposes a control strategy that is not required the teaching operation and enables to realize the desired motion without affecting the relative position error between the robot and the target object in object coordinate defined by PSD (Position Sensitive Detector). In the proposed approach, the estimation algorithm of the kinetic transformation between global and object coordinates is introduced by using PSD output, and the error of coordinate transformation estimated by the proposed approach is compensated in global coordinate. The validity of the proposed method is shown by simulations and experiments.

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This paper describes a strategy to improve the accuracy of 3D position detection of a moving object. Stereo vision is one of powerful methods to detect a target position. However the measurement accuracy depends on the configuration of a target object and two cameras of vision system. In this case, these exist a camera configuration that enables to improve the measurement accuracy of object position. On the other hand, the camera system requires a multi-DOF motion to realize fast tracking of moving object. To address the above issues, a stereo vision system with multi-DOF motion is developed in this research. The constructed vision system has two hand-eye system that are controlled independently. In the proposed strategy, two performance indices are considered to determine the manipulator motion of hand-eye system. One is camera configuration index to evaluate the performance of the position detection by the stereo vision. The other is a manipulability measure of the manipulator in the hand-eye system. Considering both indices to determine the motion of hand-eye system, the tracking performance of stereo vision system is improved. Numerical and experimental results show the availability of the proposal method.

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In control application of industrial robot manipulator, a two-inertia resonant system is normally represented as the basic plant model for various control schemes. Various control techniques with partially feedback linearization have been proposed to achieve high performance motion control. The design of such controllers basically relies on system mechanical parameters. The proper parameters of the model cannot be obtained by the parameter identification based on only manipulator force and motion measurements. In this paper, the open-loop resonant frequency characteristic of the flexible joint is employed to identify the proper mechanical parameters of the two-inertia model. The nominal link inertia and spring constant of gear drive can be readily measured by this novel identification method.
The identified parameters are used in independent-joint controller design for conventional PD control scheme and robust control scheme to verify the effectiveness of the proposed identification method. Moreover, the accuracy improvement of the proposed robust control scheme based on feedforward inverse dynamic compensation and D-PD position control gives support the validity of the proposed identification method.

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This paper proposes a new friction free bilateral system based on twin drive control system considering resonant frequency for bilateral systems. The twin drive system consists of two motors which are coupled by the differential gear. The output torque becomes a different torque of both motors. The nonlinear friction torque of twin drive system can be easily compensated. However, the resonant frequency and the anti-resonant frequency caused by the tensional vibration exist. This paper proposes a new two-mass-model of twin drive system and suppress torsional vibration by state-feedback. The proposed control method is applied to the bilateral robot, and the effectiveness of the control method is confirmed by the experimental results.

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This paper presents a friction model-based control of an ultra-precision stage that is equipped with the non-resonant ultrasonic actuator (SPIDER). The SPIDER is expected as an actuator suitable for stages for semiconductor manufacturing with the electron beam which is light source in next generation.
At first, the friction characteristics as a function of stage position are experimentally identified. Next, measuring the time variation of the static friction characteristics, the on-line identification method for the control system is proposed. And then, a friction model-based compensation for the PI control system is discussed. In addition to the PI control system, the continuous-path tracking control system with the compensation is designed. Finally, the model-based control method is verified through the positioning experiments.

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When Reusable launch vehicles (RLV) return to earth, it flies just by gliding without thrust. In this phase, one of the most likely and important faults to occur in the airframe is a jamming of the elevon. To tolerate this failure, the flight control system must keep stability and performance during such a failure. One of the effective ways to overcome this problem is to switch the controllers based on the information of the detected failure in the plant. Generally speaking, the controller must have integrators so as to yield the zero steady-state error for the controlled output even if there exist some perturbations in the plant dynamics. In this paper, the design of controller switching scenario is addressed especially focusing on the decision of the controller state at the instant of switching the controllers with integrator. Then, the proposed switching scenario is applied to the control of ALFLEX (Automatic Landing FLight EXperiment), which is the automatic landing experimental vehicle being developed for RLV, considering the occurrence of the jamming fault. Some simulations are shown to verify the usefulness of the proposed idea.

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In this paper, we propose a gait control method for redundant legged biped robot based on leg center of mass (COM) position control at constant velocity and constant height of the waist. The developed biped robot has redundant legs, which have 4 degree-of-freedoms (DOFs) on each in the saggital plane. The redundant DOF enables to move its leg tip position and its leg COM position independently. Therefore proposed robot has structural capability to control the leg COM position for keeping the projection of the total COM inside the support polygon without upper body motion. Such capability enables the stable static walk in the arbitrarily desired velocity and height of the waist motion. The validity of the proposed method for the static walk at constant velocity and constant height of the waist in the leg COM position control for redundant legged biped robot is confirmed by several results of simulation and experiment.

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This paper presents a practical on-line auto-tuning methodology for fast and precise positioning controllers using Genetic Algorithms (GA). In the system design for the proposed GA-based tuning, guidelines of the fitness evaluation and the high efficiency of the optimization are especially studied to establish the practical tuning interfaces. This GA-based optimization evaluates two fitness indexes to ensure the desired positioning performance: one is the absolute required positioning specifications, i.e., the settling accuracy and time, and the other is the residual vibration in response. In order to provide the practical tuning time and computation cost, on the other hand, the searching space of each parameter to be optimized is appropriately determined using the system stability analysis, which enables the tuning time to be reduced. The proposed auto-tuning algorithm has been verified as a practical controller design tool, paying attention to the tuning time for positioning devices in commercial machine tools.

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This paper presents a novel compensation methodology for nonlinearities in table drive system of machine tools, providing the high-precision contouring control. The nonlinearities in a target system are mainly composed of the lost motion between motor and table and the nonlinear friction on the table sliding surface with standard lubricants. In the research, the lost motion is especially modeled as a nonlinear spring/damping component at the velocity reversal motion, which causes the response delay in acceleration torque. The deterioration in table contouring performance due to the lost motion and the nonlinear friction can be separately compensated in a mode switching control manner, by superimposing the motor torque based on the lost motion model or the disturbance observer according to the system stiffness at the velocity reversal. Experimental results using a prototype show the significant performance improvements of the proposed approach in precise table contouring control.

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The paper describes a position and posture controller design based on the absolute position by external PSD vision sensor for redundant robot manipulator. The redundancy enables a potential capability to avoid obstacle while continuing given end-effector jobs under contact with middle link of manipulator. Under contact motion, the deformation due to joint torsion obtained by comparing internal and external position sensor, is actively suppressed by internal/external position hybrid controller. The selection matrix of hybrid loop is given by the function of the deformation. And the detected deformation is also utilized in the compliant motion controller for passive obstacle avoidance. The validity of the proposed method is verified by several experimental results of 3link planar redundant manipulator.

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High speed and high precision control has been required in various cases. Hence, a new linear actuator based on Linear DC Solenoid Motor (LDSM), is developed for that purpose. In addition, we propose a precision motion control for LDSM. LDSM is composed of solenoid stator and moving permanent magnet. It has simple and light structure. Moreover, the solenoid form provides small leakage and generates more power than non-linear motor. Nevertheless, the nonlinear disturbance force such as friction force prevents LDSM from controlling precisely. In this paper, the high gain disturbance observer is applied to LDSM to suppress the force. The observer is able to estimate and compensate the nonlinear disturbance force. It is confirmed that the proposed precision motion control provides LDSM with precise observer control position and force through the experiments.

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It is very important to identify the electrical parameters accurately for the current control system, the current simulator and some of sensor-less system. Generally, the electrical parameters of PM motor are identified by using the signal of motor voltage and motor current. However, current seneor has indivisual difference. This paper proposes a new identification method of both the main flux and the electrical time constant of PM motor without current sensor.
Moreover, in order to confirm the validity of this method, this paper describes self tuning of a current control system and a current simulator as an application example to a servo system, and shows an experiment result.

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This paper deals with a merging section of Personal Rapid Transit system. Several schemes have been proposed for the control of vehicles in PRT systems. In quasi-synchronous control systems, one flow of traffic must form a queue at a merging section in order to avoid the collision of vehicles. In other words, a queue is formed on one of the lines, which is called the sub line; the other line is called the main line. Basically, vehicles on the main line have priority. We propose a control strategy whereby vehicles on the main line are usually not stopped; vehicles on the main line are only stopped when the number of waiting vehicles on the sub line exceeds some specific number. Therefore, queues are formed on the main line and the sub line, respectively. This paper presents a fundamental discussion of the effects of the double queue and the relationship between traffic density and the behavior of traffic.

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This paper proposes a technique to inspect the bump height, area and volume of solder bump using X-ray fluoroscopy. Since X-ray fluoroscopy can acquire the 2-dimensional signal proportional to the thickness of a solder, it is expectable to measure a solder bump with high precision and at high speed. We introduced some image processing method to correct unevenness of image. Furthermore we introduced X-ray monitor in order to decrease the effect of X-ray fluctuation. As a result, fluctuation decrease more than 50% than without X-ray monitor. By compare to the optical measurement method, this method shows advantageous result at the viewpoint of bump coverage area and inspection speed.

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This paper describes the influence of magnetic saturation on sensorless control for interior permanent magnet synchronous motors (IPMSM). A novel sensorless control algorithm for IPMSM using 3-phase high frequency voltage input is proposed. Rotor position is estimated by simple integration procedure independently of motor parameters. Taking magnetic saturation into consideration, local inductance is directly calculated by finite element method. Calculated inductance well agrees with experimental value and the influence of magnetic saturation on motor inductance value is evaluated. It is shown that magnetic saturation causes large estimation angle error of sensorless control for IPMSM, and a method that reduces estimation angle error is proposed. The validity of proposed method is confirmed by experimental results.

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In this paper, the single-phase operation of a permanent-magnet induction generator (PMIG) is analyzed theoretically and experimentally and is compared to that of a conventional induction generator (IG) of the same size to evaluate its usefulness. Phase balancing is achieved by connecting a phase converter across their stator windings. Based on the method of symmetrical components, the steady-state performance of both the PMIG and the IG is theoretically predicted, and the results are verified through experiments. The PMIG exhibits a higher performance, in terms of output power, power factor, and efficiency, than the conventional IG.

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