Ryojun Ikeura

Variable impedance control of a robot for cooperation with a human

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.

Cooperative motion control of a robot and a human

Robots are expected to be human-friendly and to execute tasks cooperating with humans. The control system for the robots should be constructed so as to work adaptively with human characteristics. In this paper, human characteristics in a cooperation task by two humans is analyzed and it is shown that the human performance can be expressed by impedance control. We then applied the principle in making 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 gave the best result for robots cooperation with human.<<ETX>>

Evaluating the maneuverability of a control stick using electromyography

This paper proposes maneuverability indexes for a control stick that are based on consierations of muscle characteristics. The indexes are defined on the basis of muscle forces: stiffness of the musculoskeletal system and torque for accelerating the stick. Measuring muscle forces with electromyography, we examine the effectiveness of the proposed indexes experimentally. In a slow tracking operation, the index based on stiffness conforms to the subjective evaluation, but the index based on the torque is inadequate as an index of maneuverability; we therefore use the index based on stiffness as the maneuverability index. In experiments on a step operation, we divided the operation into two phases: moving and holding. The index in the holding operation is in good agreement with the subjective evaluation. In both tracking and step operations the characteristics of the index are appropriate whether or not the controlled object has a first-order lag element. As a result, it is shown that the index can indicate the maneuverability in the low-frequency tracking operation of the stick.

Experimental study on human's grasping force

We investigate the humans characteristics of grasping behavior when disturbance forces, inertial forces or moment of rotation are acted on a grasped object. First we examine the grasping behavior when the inertial force of the object is generated. A subject grasps the experimental object with the thumb and index and ring fingers, and moves it up and down repeatedly in the vertical direction. Experimental results show that the human controls the grasping force to compensate for the inertial force acted from the object and uses the force which is just greater than the minimum force required for grasping the object. Next we investigate the grasping characteristics when the moment of rotation is acted on the object. The experimental object has a weight on one side so that its center of gravity is biased. As a result, it is found that the human controls the grasping force so as not to rotate the grasped object, the moment of inertia acted on the object can be cancelled successfully.

Teaching of robot task by manual control-iterative modification by a human operator

In teaching a complicated task to a robot manipulator, the human operator must control the slave manipulator satisfactorily for a long period of time. If the human operator improves the teaching data iteratively, satisfactory data are attained easily. The characteristics of the human operators control action are investigated experimentally during the process of iterative modification. It is shown that the human operator tries to reduce the lower frequency part of an error signal at the beginning of the process and later concentrates on the high-frequency part. After many modification trials, the error is reduced quickly; the decrease rate is dependent on the natural frequency of the slave manipulator.<<ETX>>

Subjective evaluation of dancing motion model with a limited degree-of-freedom

Traditional automata perform only one pattern of motions because they are controlled by mechanical components like cams and gears. We have developed computer controlled automata which can perform various motions by changing the computer programs. We attempts to use human dancing motion for motion planning of the automata. But it has a limited degrees-of-freedom (DOF), while human dancing motions have many DOFs. To solve the problem, we propose a method to select important joints of the human dancing motion model, and to reduce the degree-of-freedom by restricting the unimportant ones. In this method, we evaluate the movement of center of gravity of each body part to decide the importance of joint. We also evaluate the generated motion by subjective evaluation, and the effectiveness is shown.

Motion planning of computer controlled automata

This paper describes motion planning of computer controlled automata (CCA). We consider two steps for the motion planning; (1) Create rough patterns of motion. (2) Modify the patterns iteratively and create a desired motion. A real time planning method for a robot task, which has been developed by authors, is applied as the first step. Using this method, a human operator can generate a trajectory of the CCA while monitoring the actual motion by operating a joystick. For accurately modifying inadequate motion in the second step, a CAD system is developed. Tools for the CAD system are described and, then, the effectiveness is shown in an experimental example.<<ETX>>

Evaluation for maneuverability of a control stick using electromyogram

Control sticks are often used in man-machine system. To increase performance of the operation, maneuverability of the stick needs to be evaluated and improved. In this paper, maneuverability indexes for the control stick are proposed considering characteristics of muscles. Using an electromyogram, by which muscle forces can be measured, we examine the effectiveness of the indexes experimentally. As a result, it is shown that the indexes can completely indicate the maneuverability in low frequency tracking operation of the stick.<<ETX>>

Teaching of robot task by manual control-trial and correction of the velocity with a variable sampling time

A new teaching method has been proposed for robot manipulators, which is developed based on manual control in real time by using human operators skills. This method allows the operator to correct the velocity data of the robot motion through the playback of teaching data. So, even on the condition of high speed task, the method is also effective and suitable. Using an experimental master-slave manipulator system, the authors examine the application of the method to the teaching of a high-speed drawing task, and analyze the teaching process of the human operator. The results show that the high-speed task can be performed by the robot manipulator successfully.<<ETX>>

Motion planning for computer controlled automata

Abstract The motion planning of Computer Controlled Automata (CCA) is described. We consider two steps for the motion planning: (1) design of rough patterns of motion and (2) modification of the patterns iteratively to generate the desired motion. A real-time planning method for a robot task, which has been developed by the authors, is applied as the first step. Using this method, by operating a joystick, a human operator can generate a trajectory for the CCA while monitoring the actual motion. To accurately modify inadequate motion, in the second step, a CAD system is developed. Tools for the CAD system are described, and then the effectiveness is demonstrated using an experimental example.