Shoshiro Hatakeyama

Internal model and saturating actuation in human operation from view of human-adaptive mechatronics

Human-adaptive mechatronics (HAM) is the area of mechatronics which adapts to the operator skill and assists its improvement. The analysis of human control action is one of the fundamental problems in the study of HAM. A special feature of human control action is the action being saturated with respect to the amplitude and velocity. At the same time, the human does not pay attention continuously to the response but intermittently scans and gets the information. In this paper, the continuous control action based on the scanned information is studied, and the desired trajectory of the human control action is considered to be generated by the closed-loop system including the internal model in the feedback path. Since the visual information is scanned intermittently, the closed-loop reference generator is considered as a sampled-hold system. The feedforward function of the cerebellum can be interpreted as the reference generator with a long scanning interval for the skilled operation. The saturating control action causing the pilot-induced oscillation is studied by taking the swing-up control of a single pendulum from the pendant to the upright position as an example. The two swing-up control laws are studied for reachability of the unstable nonlinear pendulum. One is the linear combination of sine function of the position and angular velocity, and the other is the variable-structure control for the sliding-mode function similar to the linear combination control law. The reachability is analyzed successfully by the color map.

Control strategy for a snake-like robot based on constraint force and verification by experiment

This paper aims to develop a method for the locomotion of a snake-like robot, and proposes a control strategy based on the friction force between robotpsilas body and the ground. Our concept of a control system design is that a control law should be based on the friction force as a real snake is. Both the motion equation of the robot and the friction force are derived by the projection method proposed by W. Blajer. The friction model is evaluated in the cost function of the control system design based on state dependent Riccati equation. As a result a derived control law takes the friction effect into account. We also build an experimental system. The effectiveness of the proposed method is verified by simulations and experiments.

Passive walking towards running

Passive walking emerges autonomously on a slight slope without an external input of energy. It is known that the walking motion on a steep slope evolves into a chaotic motion. In this paper a biped model for walking and running is presented, and a strategy is proposed to expand the range of stable passive walking by using a chaos-control technique based on the Ott – Grebogi – Yorke method. The resultant controller is a discrete type so that the input value changes at every step, and the generated walking motion is kept non-chaotic. Fast walking on a steep slope is achieved, and pseudorunning has also been realized in simulations. By adding an input to the biped model, in which the input corresponds to the effect of the artificial gravity field, it has been verified that pseudorunning can be realized on level ground.

A Consideration of nonlinear system modeling using the projection method

This paper considers modeling of nonlinear systems, especially nonholonomic systems, by the projection method proposed by W. Blajer. The projection method focuses on constraints of a system, and it can make a model of a non-holonomic system in the similar way of a holonomic system. The projection method also permits us the modeling as follows: first of all, the sub-model of each component is derived, and combining them gives the entire model. In this way, the complex and large system modeling can be decomposed into each easy-small sub-modeling.

Analysis of intermittent control systems by human operations

Human adaptive mechatronics is the coined name for a research project at Tokyo Denki University sponsored by Ministry of Education, Sports, Culture, Science and Technology (MEXT). Human adaptive mechatronics consists of human and mechatronics, and aims to develop Mechatronic systems adapting and assisting human operations. In this paper, the human control action of human-in-the-loop system is studied paying attention to the sampling effect via visual feedback. To analyze the performance of human operations with such factors, the swing-up of a pendulum by human was studied.

Biped walking robot control with passive walker model by new VSC servo

Passive walking on a slope is known as the most efficient and natural walking style because there is no extra power without potential energy, and the motion occurs inherently according to its mechanical property. In this paper a walking control strategy which utilizes the dynamics of passive walking as a trajectory generator is introduced. A virtual model can generate a walking pattern by being given the feasible initial state corresponding to the direction of the virtual gravity field. To enhance the robustness of the implementation a new variable structure control (VSC) servo is proposed, and applied to walking control. This VSC law is obtained as an integral form of the sign function of a sliding mode. Hence there is less chattering which may damage the mechanical components. A discrete trajectory generator and discrete estimator which are needed for the digital implementation are mentioned too. The efficiency of the strategy is demonstrated by simulation.

Brief papers: Structural identification and software package for linear multivariable systems

This paper is concerned with the structural identification of linear multivariable systems and an interactive identification package. The structural identification is done by taking the time-invariant subsystem from the realizations of the input-output relations identified using data of disjoint time intervals, and the statistical hypothesis test is employed to determine the order, where the input-output relation is identified based on the generalized least squares method using the possibly larger model for the plant. The identification package is for the identification of the input-output relation of a linear multivariable system, for the structural identification based on the realization and for data management.

Design of variable structure controller-from sliding mode to sliding sector

In general, a variable structure (VS) control system is designed with a sliding mode. But recently a sliding sector designed using algebraic Riccati equation has been proposed to replace the sliding mode for chattering-free VS controllers and for discrete-time VS controllers. In this paper we design a new sliding sector based on the sliding mode and propose a VS controller with the sliding sector. The proposed VS control system is quadratically stable even if there exists parameter uncertainties and external disturbances. The experimental results on an inverted pendulum show the effectiveness of the proposed VS control algorithm with the sliding sector.

Motion analysis by experiment and simulation for riding bicycles with children

The purpose of this paper is motion analysis by experiment and simulation for riding bicycles with children. It is very important to think about stability when the bicycle is driving with children. However, such a research is not so performed. Therefore, analysing human motions in the such case by some experiments and simulations, dynamic characteristics of the such case are shown. The modeling of bicycle is performed, and the model is used for the simulations.

Control Strategy for a Snake-Like Robot Based on Constraint Force and Verification by Experiment

This paper describes a locomotion method of a snake-like robot with passive wheels based on a stabilizing control theory for nonlinear systems. The advantage of this method is that the locomotion can be realized only by a state feedback control law, while many reported methods require some reference trajectory such as the serpenoid curve or are realized not only by a locomotion control, but also by a posture control to avoid singular postures. The proposed method evaluates the friction force of passive wheels in the quadratic-like cost function, so that the efficiency with respect to the input can be improved. The state-dependent Riccati equation technique is utilized to realize this method and it permits us to tune the system performance like an optimal control case. The projection method, one of the nice modeling techniques, is utilized to derive both the plant and the friction model. The effectiveness of the proposed method is verified through numerical simulations and experiments.