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Vertical walking distance is discussed. The horizontal distance is estimated by using the three dimensional acceleration of the subject's toe. Considering the movement of the foot, it is assumed that only the pitch angle of the foot changes and that the velocity of the foot is never negative. A three dimensional accelerometer is fixed to the subject's toe and measures the acceleration during the swing phase of the foot. A piezoelectric gyro is used to estimate the angle of the foot and to calculate its horizontal acceleration. The horizontal distance is obtained by integrating the horizontal acceleration twice each step. The vertical distance is calculated by integrating the change of atmospheric pressure during ascent or descent. A band pass filter is applied to reject natural changes of the atmospheric pressure and sensor noise. The integration of the output of the filter produces a value corresponding to the vertical distance. Experiments were performed in a horizontal corridor and on some stairs. The results show that the error of the horizontal distance estimated is less than 5.3% and 0.0% on average, and the vertical distance is less than 11.1%.

In this paper, human learning characteristics in the tracking tasks of iterative nature are investigated. Various linear and nonlinear systems are used as plant, and a human operator has to generate the proper control inputs to force these systems in tracking the desired trajectory. The learning behaviour of the human operator in modifying his control actions is studied and it is observed that the human operator can improve his performance quite efficiently despite the unavailability of any information about the system or the desired trajectories. It is concluded from the experiments that the human operator not only use the information that is directly available to him (error in this case), but also extracts some useful information (e.g. error rate) that he feels is necessary to generate a good control action. The limitation of the human performance is studied in frequency domain, and the performance of the human operator against the frequency bandwidth of error and error rate signals are highlighted. Analysis of the results revealed that a human operator gives more importance to the error rate in generating his control actions and, accordingly, it is observed that his limitation in term of performance is more sensitive to the frequency bandwidth of the error rate as compared to the error. The human operator cannot improve his performance once the frequency components of the error or error rates shift to the higher frequencies, say above 1.0 Hz.

We consider the design of a modular hybrid functional electrical stimulation (FES) system for an injured person. We propose a system using an assistant robot to follow the FES performance, as FES control has many uncertainties in characteristics. The assistant robot used is a 3-link serial type, and attached to the injured person to actively assist the FES performance. The assistant robot must be very simple, light, and can be easily attached to the injured person. We constitute various types of human models which can be used to show the exact actions and muscle function characteristics. Furthermore, we propose a control system for the model of an injured person fitted with the assistant robot. Finally, we show that a robust performance of the injured person has been achieved in the standing motion using the modular hybrid FES system.

In this paper, we deal with the handling of a flexible object by rigid arm robots. We consider three main tasks: 1) to propose a mathematical model for a variety of flexible objects of our daily life; 2) to design a controller to achieve cooperative handling of the flexible object by the robots; and 3) to analyze the stability and robustness of the control system. In particular, demands for manipulating a large-scale structure by a space robot will be increasing. Therefore, it is important to constitute the cooperative control problem of several robots handling a flexible object, and to analyze the proposed control system.

Robots are expected to be human-friendly and to execute tasks in cooperation with humans. Control systems for such robots should be designed in order to adapt human characteristics. In this paper, a variable impedance control method for robot to cooperate with human is proposed. First, the human characteristics in a cooperative task between two humans are analyzed. It is confirmed that human characteristics can be expressed by a variable impedance model. Then, we make a robot and a human to execute a cooperative task. It is shown that the impedance parameters obtained in the experiment performed by two humans give the best characteristics to the robot for cooperation with the human.

Deals with the handling of a constrained flexible object by a robot. The authors regard the robot as a rigid manipulator and the object as having one side free and the other side fixed to the wall. The authors' purpose is for the robot, to follow up the open end of the flexible object and to suppress its vibration. As a technique to achieve their purpose, the authors propose a new numerical modeling method to handle the object by the robot. This model reveals the force relationship at the handling point. Next, the authors constitute the control system to make it possible to achieve two performances, following up the object and vibration suppression.

In this paper, we deal with the handling of a vibrating flexible object by a rigid dual-arm robot. Each arm consists of two links and an end-effector. The aim of this work is to realize the position control of the flexible object while suppressing its vibration. In particular, the problem considered is about the control system designed to realize the active handling of the flexible object. For this purpose, we propose a model for both the robot and the object in a connected position so as to guarantee the whole handling system's stability. We also express a new mathematical model of the flexible object using the model reduction theory in the same connected position. The model of the robot and the object while they are in contact is derived by the positional requirements at the handling point. We also consider the design of the controller to satisfy the constraint condition at the static equilibrium point. The design of the combined system consisting of the robot and the object is useful for the analysis of whole handling system's stability.

In the future, robots may perform cooperative tasks with humans in daily life. In this paper, the authors focus on a hand-over motion as an example of cooperative work between a human and a robot, and propose an algorithm which enables a robot to perform a human-like motion. First the authors analyze trajectories and velocity patterns of a hand-over motion performed by two humans. The experimental results show that a receiver's motion during hand-over has some typical characteristics. The authors then confirm that a human-like motion can be generated using these characteristics. Finally, the authors plan the robot's motion considering these results. Initially, two kinds of potential fields are used to generate a motion command which leads the robot along a trajectory similar to that followed by the human. In addition, more precise motion is considered at the end of the hand-over operation to guarantee accurate positioning and to soften the shock of contact. Simulation results show the validity of the proposed method.

A robot manipulator with passive joints has the following features: a light weight manipulator can be fabricated by implementing simple hinge; and the manipulator is fault-tolerant to actuator failure by using frictional torque at the passive joint.. A motion control of a two-link robot manipulator actuated only at the second joint is presented in this paper. The first integral of the system is derived and the motion is described as a variation of the integral constant. Also, the dynamically enforced motion and free motion are analyzed based on the first integral approach proposed in this paper. An effective motion control algorithm is established using the dynamic characteristics positively. Finally a simple numerical example is given.

This paper considers the generation of skillful control actions, which require high experience of a task, by manual control using a master-slave manipulator. The authors have shown that a robot manipulator can be "taught" a skilled task using a "teaching method" based on manual control at a master manipulator. It takes, however, a long time for a human operator to control the master-slave manipulator satisfactorily when the task is complicated. In this paper, an iterative modification method using the master-slave manipulator (IMMSM) is proposed, which makes it possible to improve the movement of the slave based on performance evaluation. As the master-slave manipulator is usually used in teleoperation, the master is complicated and expensive because of the high maneuverability required. By applying the proposed method, a simple device like a joystick can be used. Using a joystick and a small manipulator, the authors have investigated the effect of IMMSM allowing iteration in the "teaching" of a simple task. The experimental results show that the operator can "teach" a skilled task to the robot manipulator using IMMSM. The oscillation frequency of the task error becomes large as progress is made through iterative modifications and the operator, finally, can not modify the high frequency signal any further. To avoid this confusing development for the operator the high frequency signal of the master manipulator is restricted by a function like a low-pass filter. In an experiment, it is confirmed that a filtering function helps the human operator to perform IMMSM more accurately.>

A tree search technique for dynamic control problems is proposed. The method is proven to be effective by successfully solving the swinging control problem for a pendulum carried by a motor-driven cart. It is extremely difficult to determine a swinging control rule analytically because the problem is nonlinear and the system has two degrees of freedom. To apply the proposed tree search procedure to the nonlinear control problem, some numerical calculations are performed. The result shows that the technique is suitable for dynamic control problems, and in particular, for the complicated nonlinear dynamic control problem.>

The experimental positioning of a flexible arm by a human operator is described. The flexible arm is characterized by nonlinearity and infinite degrees of freedom. The human operator interprets a given task and finds a procedure for the operation, devising an effective way of achieving the goal, based on his or her experience and knowledge about the task. The question of how these results can be modeled and applied to automatic control systems is considered, and the use of a reference input filter is proposed. The filter gives a satisfactory overall response if the time constant is chosen appropriately.>

Some features of human operator's ability in optimal control tasks are experimentally studied. A subject is instructed to control a plant properly by manipulating a potentiometer which produces an input to the plant. At the same time he is requested to decrease the value of a performance index shown to him after each trial; the index evaluates his control action based on a formula. It is shown that the subject can decrease the index value after many trials even if he does not have any knowledge about the dynamics of a plant and the performance index. This suggests that the learning process can be reinforced by showing the performance index to the operator.>