Masatsugu Otsuki

Mobile rovers for lunar or planetary exploration are expected to break a new ground in the field of space science. The realization of adequate locomotion mechanisms for traveling on the surfaces of extraterrestrial bodies is principally a technical challenge. In particular, a reliable mobility on loose soil such as the lunar soil is required for successful rover missions on the Moon. So, the authors propose the novel concept of a micro-rover with an old and new locomotive component, screw unit, and such innovative rover is called Screw Rover. The screw units basically enable the rover to move in various directions by the simple combination of driving modes. Furthermore, Screw Rover can possess a robust and insensitive structure to the serious situation which is a stuck phenomenon caused by slippage and sinkage. In this paper, the fundamental considerations which include the design overview of Screw Rover and the theoretical discussion are presented as the primary study on Screw Rover.

JAXA is examining research and development of an autonomous system, such as mobile rover required for searching ground and constructing basement on the lunar surface in succession of KAGUYA (SELENE) project. Because the lunar surface covered by irregular terrain and muddy soil called regolith, rover has a difficulty in running on such harsh environment. Therefore rover is required of taking a sustainable running mechanism that does not become cautions of fatal functional and mission stop. Then some functions are needed for rover running system on lunar surface, for example certain acting on brake and drive, removing adhered soil and tightens muddy soil. Newly flexible wheel is required to achieve running with high reliability by changing the wheel contact shape itself and being lower contact force on the ground. This paper describes the static measuring test results of flexible wheel contact and distributed pressure, and analysis results of flexible wheel dynamics model.

To clarify the internal and global information of the Moon is very important in future lunar exploration. This paper describes a lunar subsurface exploration system to bury a seismometer in the lunar regolith by a burrowing robot. The authors have proposed a new screw drilling mechanism for a burrowing robot to achieve that purpose, in particular this paper describes the concept of expansion to the complete burrowing system applying the screw mechanism. The authors call the novel robot BSR (Burrowing Screw Robot). Also in this paper, the authors consider the requirements of the design concepts for developing the BSR and the experimental environments.

An approach to the lunar and planetary subsurface exploration by an excavation robot is a novel and challenging project. There are few proposals including an excavation system for planetary exploration by an autonomic and small robot. So, this paper describes a basic concept about subsurface exploration by viewpoint of soil dynamics and robotics. This paper considers the fundamental strategies to advance under the surface and the contents serve as a guideline to establish the total system of the lunar excavation robot.

This paper presents the vibration control, using passive or semi-active dampers, for the transverse vibration of an elevator rope. The dampers are located in the vicinity of the top end of rope and the vibration of rope is reduced by impact with the dampers. The adequate gap width, location, and damping coefficient of the damping device are calculated for the case in which the arbitrary constant length of the rope is allocated and the building is subjected to various earthquakes. Further, the performance of the semi-active vibration control method for the suppression of the vibration of rope is verified; consequently, the usefulness for the proposed method is shown.

Vibration of a large transport system is induced by its motion and the vibration prevents the next motion as the settling time is extended. This paper presents the methodology to simultaneously control the motion and vibration of a cantilevered fork as one of the large transport system. Hence, the nonstationary robust control method considering modeling error of the controlled object as the unstructured uncertainty is applied to enhance the performance for the motion control and vibration suppression by switching the robust state feedback controllers smoothly due to the motion. The usefulness of the proposed methodology is verified through the experimental examinations; consequently, the settling time of the motion and vibration of the controlled object is considerably reduced in the comparison with the result by the conventional method.

Simultaneous control for position and vibration is demanded in the rapid positioning machine with flexible structure such as crane and transport systems in factory automation. Furthermore, the mass distribution, whose the positioning machine in XY plane, varies due to the positioning command, hence, it is classified into a time-varying system. This paper presents the simultaneous control of the rapid positioning and vibration for the flexible structure by the nonstationary robust control method with considering the time-varying characteristics of the controlled object and uncertainties due to its parameter variation. The good performance and robustness of the proposed method are shown through the numerical calculation.

A control method based on the theory of nonstationary sliding mode control is presented for an application to suppression of transeverse vibration of elevator rope. The transverse vibrations of ropes of high-speed elevator are caused by a resonance with sway of building which is subjected to an earthquake and big wind, hence, an effective solution is demanded. The nonstationary sliding mode control is effective for the control of elevator rope categorized by a time-varying system and robust for nonlinearity of a control device. In this paper, therefore, the vibration control for the elevator rope is performed based on the nonstationary sliding mode control using an input system which has gaps between an actuator and the rope because of preventing abrasions of rope. The suppression performance of the proposed method is examined by the numerical calculation on the condition of practical use. Consequently, the numerical results indicate that the performance of the proposed method is remarkable.

This paper presents a synthesis method of the nonstationary sliding mode control system using the time-varying switching hyperplane. The time-varying switching hyperplane is designed explicitly considering time-varying characteristics of a controlled object based on the nonstationary optimal control theory. It is proved that the equivalent control system with the time-varying switching hyperplane and the closed-loop system with the proposed controller become internally stable. The feature and the performance of the proposed controller are examined through the numerical calculation which performs the control of a linear time-varying system.

In this paper, it is performed to suppress the transverse vibration of elevator-ropes caused by the resonance with sway of high-rise building. The elevator-rope has the characteristics due to its flexibility and the variation of its length. And also a control input system to suppress its vibrations requires gaps between an actuator and the rope because of preventing its abrasion. Therefore, we apply the nonstationary sliding mode control to reduce its vibrations with compensating the influence of time-varying characteristics and spillover and also the nonlinearity as the gap of input system. The suppression performance and the influence of nonlinearity are verified through the numerical calculations.

This paper presents a synthesis method of nonstationary sliding mode controller with time-varying switching hyperplane for reducing the vibrations of wire changing its length. The proposed method deals with a change of system in time domain continuously. First, we construct the model of controlled system including a wire and two mass points at both ends by non-dimensional synthesis method. Then the controller with time-varying hyperplane is designed with the time-varying Riccati equation. Finally, the performance of this controller is verified through the simulation in the two cases that the length is getting long and short.

This paper presents a synthesis method of nonstationary sliding mode controller with time-varying switching hyperplane for reducing the vibrations of rope of elevator. The proposed method deals with a variation of system in time domain continuously because the controller with time-varying hyperplane is designed based on the time-varying Riccati equation. The controlled system is modeled on a structure including an elevator system and it is implemented by the time-varying controller and VSS observer. Then the performance of this controller is verified through the numerical calculation in the two cases that the elevator descends and ascends when the structure is subjected to Chi-Chi earthquake.

For a control problem of wire changing its length such as elevator cables and crane ropes, a controller considering its nonstationary characteristics is effective in suppressing their vibrations. Additionally, the controller having robustness for various uncertainties is valid within suppressing the vibrations of object that has a flexible feature. Consequently, the main objectives of this paper are to propose a nonstationary robust control method and to reduce the transverse vibrations of wire. The vibration controller is designed based on H-infinity theory and a time-varying weighting for the worst disturbance is also optimized to have the appropriate robustness for the parametric uncertainties in time domain. The robust stabilization performances of controller is demonstrated through the numerical calculations and then the robust controller shows the advantage regarding the robustness on the various uncertainties in comparison with the optimal controller.

For a transverse vibration control of an elevator rope, a controller considering its nonstationary characteristics is effective in suppressing its vibrations, because the elevator rope is a kind of time-varying system. In addition, a length of elevator rope varies with time, hence, it is difficult to locate actuators and sensors for the control on arbitrary position such as center of rope and abdomen of modal vibration. As a result, we situate them at the end of rope or near the boundary based on the estimation of Hankel singular value expressing the degree to control and observe state values of controlled object. moreover, the controller having robustness for various uncertainties is valid within reducing the vibrations of object that has a flexible feature. Consequently, the main objectives of this paper are to suppress the transverse vibrations of elevator rope with nonstationary robust control methods. The suppression and robust stabilizing performances of controller are demonstrated through the numerical calculations for the case that the elevator system is subjected to shifts of tension of wire and disturbance from a building. Finally, we derive the sufficient suppression of transverse vibration of elevator rope.

For a control problem of wire changing its length such as elevator cables and crane ropes, a controller considering its nonstationary characteristics is effective in suppressing their vibrations. Additionally, the controller having robustness for various uncertainties is valid within suppressing the vibrations of object that has a flexible feature. Consequently, the main objectives of this paper are to propose a nonstationary robust control method and to reduce the transverse vibrations of wire. The vibration controller is designed based on H-infinity theory and a time-varying weighting for the worst disturbance is also optimized to have the appropriate robustness for the parametric uncertainties in time domain. The robust stabilization performances of controller is demonstrated through the numerical calculations and then the robust controller shows the advantage regarding the robustness on the various uncertainties in comparison with the optimal controller.

There are many uncertainties for characteristics of building and information of disturbance. And a restoring force characteristic of building has nonlinearity. Therefore soft computing method is a strong interest to control such buildings. We describe the Optimal Fuzzy control system as seismic response for a high-rise building. A tall building with 500 meters in height is reduced to the model with 2 meters. Response analyses were carried out for the model reduced by 1/250 in length. It was pointed out that the reduction rate of response under the Optimal Fuzzy control with the known linear model is the same as that of the Optimal control (LQG control). Meanwhile with nonlinear model the Optimal Fuzzy control is better. However the Optimal Fuzzy control needs to investigate the optimal solution the value of membership function, because the value of membership functions make difference of the control performance.

This paper presents a vibration control method for a wire with time-varying length such as an elevator cable and a crane wire. The characteristics of the wire is varying with time, hence, a nonstationary controller which is designed depending on the time variation of controlled object is effective. Furthermore, since a wire is flexible structure, a spillover due to uncertainties and ignored high order modes is caused. Therefore, we propose the controller considering the robustness for the uncertainties of controlled system and its usefulness is verified through a numerical calculation.

This paper presents a synthesis method of nonstationary sliding mode controller with time-varying switching hyperplane for reducing the vibrations of wire changing its length. The proposed method deals with a change of system in time domain continuously. First, we construct the model of controlled system including a wire and two mass points at both ends by non-dimensional synthesis method. Then the controller with time-varying hyperplane is designed with the time-varying Riccati equation. Finally, the performance of this controller is verified through the simulation in the two cases that the length is getting long and short.

This paper presents a synthesis method of nonstationary optimal controller with time-varying criterion fuction for reducing vibration of the wire. We propose the two methods to decide the weightings of criterion function. One is to give weight the reflected waves, and the other is for each mode. Moreover, by using the disturbance accommdation control method, the weight on the state value of absolute coordinate system can performed, even if the observed state value is relative. Then, we model the objective system using the both relative and absolute coordinates, and compare their performance of nonstationary optimal controllers by the simulation.

This paper presents a vibration control method for a wire with time-varying length such as an elevator cable and a crane wire. The characteristics of moving wire are varying with time. When the wire is approximately modeled with such a method as FEM, it is possible to cause a spillover due to the ignored high order modes. Therefore, the robustness for the variation of tension, spillover of high order modes and rapid change of disturbance is important and a robust nonstationary control method is proposed by applying nonstationary H-infinity control theory in this study. For the moving wire such as crane string and elevator cable, it is possible to reduce the vibration by using only a nonstationary robust controller for the case that the mass at the tip of wire changes its weight, that is, the tension of wire varies. The robust controller then is designed based on a lower order model of wire with the frequency weightings. As a result, in the numerical calculations we show the robustness and the usefulness of the robust controllers are shown.

This study presents a synthesis method of a nonstationary optimal controller with a time-varying criterion function for reducing vibration of a time-varying object such as rope of elevator and crane. Moreover, from the viewpoint of wave propagation, we also propose a method of reducing vibration with wave-absorbing controller to remove the reflected waves. As an illustration, the performance of reducing vibration with respect to the rope-sway problem on a high-rise building is examined through numerical calculation. These nonstationary optimal and wave-absorbing controllers are compared with the stationary optimal controller in case that the structure is subjected to Kobe earthquake.

This paper develops an approach for the control of the motion of a multiple-link manipulator possessing unactuated joints. A three-rigid-link arm with its shoulder joint actuated and two elbow joints unactuated is modeled as a nonlinear Affine system. The system is a case of second-order nonholonomy since the constraints at the passive joints contain terms of accelerations. In the proposed method to solve the problem of optimal positioning the control input is expressed as a general function of a Fourier basis parameter acquired by using the Ritz method; then this parameter is optimized through the application of the Newton method. Numerical simulations were carried out and tests with an experimental setting demonstrate the effectiveness of the approach.