Tetsuo Kotoku

Balance control of a piped robot combining off-line pattern with real-time modification

Since a biped robot tends to tip over easily, stable and reliable biped walking is a very important achievement. In this paper, we propose a balance control method based on an off-line planned walking pattern with real-time modification. First, a method of generating a highly stable, smooth walking pattern is presented. Then, a method of real-time modification consisting of body posture control, actual zero moment point control and landing time control based sensor information is proposed. By combining the proposed off-line walking pattern with real-time modification, the biped robot can walk smoothly and adapt to unknown environments. The effectiveness of the proposed method is confirmed by dynamic simulator such as walking on unexpected irregular rough terrain, soft ground and in environments in the presence of disturbances.

A study of casting manipulation (swing motion control and planning of throwing motion)

We propose a new type of manipulator, a casting manipulator, which includes flexible parts, such as a string, in the link mechanism. A gripper is attached at the end of the string. In order to let the gripper reach a target, the rigid link is swung until the necessary motion of the gripper is generated. The gripper is then thrown to the target by releasing the string at the suitable time. In this paper we describe the manipulation of a casting manipulator. We present a method of oscillating a casting manipulator by considering it as a two-degrees-of-freedom nonholonomic system. First, we propose a method to swing the manipulator for casting motion, and then discuss the selection of swing motion and decision of the timing for releasing the string.

Facial expression communication with FES

Facial expression communication is considered, mainly focusing on achieving smooth telecommunications. Gesture and facial expressions are considered to be significant factors in telecommunications, such as tele-services. To realize a real time communication system for facial expression, we proposed the facial expression space (FES) and a correspondence technique between each personal facial expression space. Then, a real time facial expression communication system is developed, which transports the facial expressions but not the images themselves. This final system is able to synthesize the facial expressions with two persons, further more in cartoon characters. The experimental results show the validity of these criteria.

Task-based data exchange for remote operation system through a communication network

Proposes task-based data exchange for teleoperation systems through a communication network as an efficient method of transmitting data between an operation device and a remote robot. On the task-based data exchange, the more important information according to the contents and conditions of the task which the robot performs is given transmission priority, for example, by altering the contents of the transmitted data. We have built an experimental system in which the master arm in Tsukuba and the slave arm in Kawasaki, separated by, about 100 km, are connected through N-ISDN and the standard techniques are utilized, such as TCP/IP, socket, JPEG, etc. A series of experimental tasks has been effectively carried out by the task-based data exchange, that is, crank operation which consists of grasping and revolution. The communication network with capacity limitations was used effectively, and the high maneuverability in real-time with bilateral servo control has been realized. The effectiveness of the task-based data exchange has been confirmed.

Swing motion control of casting manipulation

We begin by describing the process of casting manipulation and discussing the swing motion phase. We propose a method of generating the desired swing motion by keeping the string taut from the initial state when the links are hung. We investigate a method for choosing feedback gain using an off-line simulation chart. The method is evaluated by numerical experiments and shown to be effective. We constructed a two-link casting manipulator and conducted an experiment in swing motion control. The experimental results show that the proposed method of swing motion control was effective.

Coordinated rate control of multiple telerobot systems with time delay

A collision-free coordinated rate control scheme is discussed for multi-operator-multi-robot (MOMR) teleoperation using a network with communication time delay. However, the effect of time-delay would pose a more difficult problem to MOMR teleoperation systems and seriously affect their performance. In this work, the time-delay problems in remote collaboration through MOMR teleoperation are first investigated. Then, the scaled rate control method is proposed to cope with the collision arising from the time-delay in MOMR teleoperation system. We scale down the velocity of the slave end-effector when the possible collision is expected during the collaboration. To verify the validity of the proposed scheme, an experiment on planar block arrangement by two slave manipulators was performed based on simulation models.

Swing motion control of casting manipulation (experiment of swing motion control)

We have been developing a casting manipulator which includes a flexible string in the link mechanism in order to enlarge the work space of the manipulator. Like the casting motion of fly fishing, the necessary motion of the gripper, which is attached at the end of the string, is generated by swinging a rigid link The gripper is thrown to the target by releasing the string at the suitable time. In this paper we deal with the basic swing motion control of the casting manipulator. We describe a method of oscillating the casting manipulator by considering it as a two-degrees-of-freedom nonholonomic system By planning a time-periodic reference for the second joint while controlling the first joint, the desired swing motion of the system can be generated. The method was evaluated by comparing the results of numerical simulation and those of experiments using the casting manipulator hardware.

Study on casting manipulation (experiment of swing control and throwing)

We have been developing a casting manipulator which includes a flexible string in the link mechanism in order to enlarge the work space of the manipulator. Like the casting motion of fly fishing, the necessary motion of the gripper, which is attached at the end of the string, is generated by swinging a rigid link. The gripper is thrown to the target by releasing the string at the suitable time. We deal with the swing motion and throwing motion of the casting manipulation. First, we describe a method of oscillating the casting manipulator by considering it as a two degrees of freedom nonholonomic system. The method of the swing motion generation is investigated through experiments. Next we propose a method of planning of throwing the gripper considering the time delay of releasing the gripper and frictional force which disturbs the flying motion of the gripper. The evaluation by comparing the results of numerical simulation with those of experiments using the casting manipulator hardware has shown the effectiveness of the proposed methods.

Walking patterns and actuator specifications for a biped robot

Since most conventional robots cannot easily be adapted to environments designed for humans, a human-size biped robot is expected to be able to play an important role in assisting human activities. The selection of suitable joint actuators is an important point when developing a human-size biped robot. In order to select suitable actuators and effectively utilize the selected actuators, it is necessary to clarify the relationship between walking patterns and the specifications of each joint actuator, and this is the issue tackled in the paper. First, a method of generating a high stability, smooth walking pattern is presented, and it is shown how various walking patterns can be produced by setting a series of defined walking parameters. Then, the dynamics of the robot, including the reaction force between the feet and the ground, are formulated. Finally, by simulation studies, the correlation found between actuator specifications and walking patterns is described, and the effectiveness of the proposed method is suggested.

Facial expression space for smooth tele-communications

In this paper, the facial expression is mainly focused to achieve the smooth tele-communications. The facial expressions has been considered as the most significant factor in tele-communications, such as tele-services. To realize the real time facial expression transportation system, we propose the facial expression space (FES) and a correspondence technique between each personal facial expression spaces. Then, real time facial expression transportation system is developed, which transports the facial expression but not the image itself. This final system is able to display the same facial expressions in another person and further more in cartoon characters. The experimental results show the validity of these criteria.