Toshiyuki Murakami

Bio: Toshiyuki Murakami is an academic researcher from Keio University. The author has contributed to research in topics: Motion control & Control theory. The author has an hindex of 33, co-authored 425 publications receiving 6541 citations. Previous affiliations of Toshiyuki Murakami include Ministry of Economy, Trade and Industry & National University of Singapore.

Motion control for advanced mechatronics

Abstract: Motion control is now recognized as a key technology in mechatronics. The robustness of motion control will be represented as a function of stiffness and a basis for practical realization. Target of motion is parameterized by control stiffness which could be variable according to the task reference. However, the system robustness of motion always requires very high stiffness in the controller. The paper shows that control of acceleration realizes specified motion simultaneously with keeping the robustness very high. The acceleration is a bridge to connect such robustness and variable stiffness. For practical applications, a technique to estimate disturbance is introduced to make motion controller to be an acceleration controller. Motion control of flexible structure and identification of mechanical parameters are also described.

Torque sensorless control in multidegree-of-freedom manipulator

Abstract: A torque sensorless control for a multi-degree-of-freedom manipulator is described. In the method, two disturbance observers are applied to each joint. One is used to realize a robust motion controller. The other is used to obtain a sensorless torque controller. A robust acceleration controller based on the disturbance observer is shown. To obtain the sensorless torque control, it is necessary to calculate the reaction torque when the mechanical system performs a force task. The calculation method for the reaction torque is explained. Then the method is expanded to workspace force control in the multi-degree-of-freedom manipulator. Several experimental results are shown to confirm the validity of the proposed sensorless force controller. >

Vibration control of 2 mass resonant system by resonance ratio control

Abstract: This paper presents a position control method to suppress torsional vibrations of 2 mass resonant systems without using position sensor on the arm portion. Instead of using a position sensor, the reaction torque caused by the shaft torsion is utilized for the suppression of the vibration. In this paper, the reaction torque is estimated by an observer using motor portion parameters and state variables. The feedback of the reaction torque makes it possible to control the "resonance ratio", which is a novel concept for vibration controls. The proposed control system is based on both the conventional PD control and the resonance ratio control, and the controller gain determination method is discussed. The validity of the proposed method is also confirmed by several experiments. >

Adaptive Control for Virtual Steering Characteristics on Electric Vehicle Using Steer-by-Wire System

Abstract: This paper describes an adaptive control to realize the desired steering characteristics on a vehicle. As is well known, the steering characteristics indicate handling performance on a vehicle and are important for safe driving. In this paper, a strategy to adjust it to a driver's preference easily using a steer-by-wire system is proposed. The control system including the proposed method intervenes only when the front tire cornering stiffness undergoes many changes. Then, the estimated self-aligning torque is fed back to the steering wheel so that a driver can feel reaction torque from the road. This is one of the remarkable features in the proposed steer-by-wire system. Numerical simulation and experiment are carried out to show the validity of the proposed method.

Self sustaining bicycle robot with steering controller

Abstract: Bicycle is a transportation device without any environmental burden. However, bicycle is unstable in itself and it is fall down without human assistance like steering handle or moving upper body. In these days, electric power assistance bicycles are used practically, but all of those bicycles merely assist human with pedal driving and there are no bicycles that help to stabilize its position. Hence, stabilizing the posture and realizing stable driving of a bicycle have been researched. Dynamic model of running bicycle is complicated and it's hard to recognize completely. However, assuming that the rider doesn't move upper body, dynamics of bicycle is represented in equilibrium of gravity and centrifugal force. Centrifugal force is risen out from the running velocity and turning radius determined by steering angle. Under these conditions, it is possible to stabilize bicycle posture by controlling its steering. In this paper, the dynamic model derived from equilibrium of gravity and centrifugal force is proposed. Then the control method for bicycle steering based on acceleration control is proposed. Finally, the validity of this method is proved by the simulations and experimental results.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Motion control for advanced mechatronics

Abstract: Motion control is now recognized as a key technology in mechatronics. The robustness of motion control will be represented as a function of stiffness and a basis for practical realization. Target of motion is parameterized by control stiffness which could be variable according to the task reference. However, the system robustness of motion always requires very high stiffness in the controller. The paper shows that control of acceleration realizes specified motion simultaneously with keeping the robustness very high. The acceleration is a bridge to connect such robustness and variable stiffness. For practical applications, a technique to estimate disturbance is introduced to make motion controller to be an acceleration controller. Motion control of flexible structure and identification of mechanical parameters are also described.

A Survey of Augmented Reality Technologies, Applications and Limitations

Abstract: We are on the verge of ubiquitously adopting Augmented Reality (AR) technologies to enhance our percep- tion and help us see, hear, and feel our environments in new and enriched ways. AR will support us in fields such as education, maintenance, design and reconnaissance, to name but a few. This paper describes the field of AR, including a brief definition and development history, the enabling technologies and their characteristics. It surveys the state of the art by reviewing some recent applications of AR technology as well as some known limitations regarding human factors in the use of AR systems that developers will need to overcome.

A nonlinear disturbance observer for robotic manipulators

Abstract: A new nonlinear disturbance observer (NDO) for robotic manipulators is derived in this paper. The global exponential stability of the proposed disturbance observer (DO) is guaranteed by selecting design parameters, which depend on the maximum velocity and physical parameters of robotic manipulators. This new observer overcomes the disadvantages of existing DOs, which are designed or analyzed by linear system techniques. It can be applied in robotic manipulators for various purposes such as friction compensation, independent joint control, sensorless torque control and fault diagnosis. The performance of the proposed observer is demonstrated by the friction estimation and compensation for a two-link robotic manipulator. Both simulation and experimental results show the NDO works well.

Torque sensorless control in multidegree-of-freedom manipulator

Abstract: A torque sensorless control for a multi-degree-of-freedom manipulator is described. In the method, two disturbance observers are applied to each joint. One is used to realize a robust motion controller. The other is used to obtain a sensorless torque controller. A robust acceleration controller based on the disturbance observer is shown. To obtain the sensorless torque control, it is necessary to calculate the reaction torque when the mechanical system performs a force task. The calculation method for the reaction torque is explained. Then the method is expanded to workspace force control in the multi-degree-of-freedom manipulator. Several experimental results are shown to confirm the validity of the proposed sensorless force controller. >