Mitsushige Oda

Ground-space bilateral teleoperation of ETS-VII robot arm by direct bilateral coupling under 7-s time delay condition

A bilateral teleoperation experiment with Engineering Test Satellite 7 (ETS-VII) was conducted on November 22, 1999. Round-trip time for communication between the National Space Development Agency of Japan ground station and the ETS-VII was approximately seven seconds. We constructed a bilateral teleoperator that is stable, even under such a long time delay. Several experiments, such as slope-tracing task and peg-in-hole task, were carried out. Task performance was compared between the bilateral mode and the unilateral mode with force telemetry data visually displayed on a screen. All tasks were possible by bilateral control without any visual information. Experimental results showed that kinesthetic force feedback to the operator is helpful even under such a long time delay, and improves the performance of the task.

Model-based space robot teleoperation of ETS-VII manipulator

In our previous research, we developed space robot teleoperation technology to achieve control from the ground of effective manual manipulations in orbit. To solve the communication time delay in the space robot teleoperation, we propose a mixed force and motion command-based space robot teleoperation system that is a model-based teleoperation. Moreover, we have also developed a compact 6-degree-of-freedom haptic interface as a master device. The important features of our teleoperation system are its robustness against modeling errors and its ability to realize the force exerted by the operator at the remote site. We introduce a new control method, which modified our model-based teleoperation system, to control the real robotic system Engineering Test Satellite VII manipulator. Surface-tracking and peg-in-hole tasks have been performed to confirm the effectiveness of our system. The experimental results obtained with our system including the haptic interface demonstrate its ability to perform these tasks in space without any major problems. We also evaluated different master device approaches for the model-based space teleoperation system. For this purpose, we used two methods, which are a master-slave (MS) approach and a force-joystick approach. Our results show that the MS approach is the best control method for contact tasks in which the directions of motion of the slave arm and of the operators input force are different, as in the surface-tracking task.

ETS-VII, space robot in-orbit experiment satellite

National Space Development Agency of Japan (NASDA) is to launch an engineering test satellite named ETS-VII in the year 1997 to develop and perform in-orbit test of rendezvous docking and Space robot technologies. ETS-VIIs robot experiment includes (a) performance evaluation of satellite mounted robot system, (b) coordinated control of satellite attitude and robot arm, (c) teleoperation of the satellite mounted robot arm, (d) demonstration of in-orbit satellite serving. The ETS-VII satellite carries a robot arm of 2 m long and 6 dof which will be teleoperated from a ground control station. This paper shows mission, design and development status of ETS-VII space robot experiment mission.

Dynamics, control and impedance matching for robotic capture of a non-cooperative satellite

In this paper, the contact motion between rigid bodies floating in space is formulated and dynamic conditions are investigated in order to capture a non-cooperative target. As for the theoretical investigation, the definition of the virtual mass is recalled to model the inertial property of a space robot for the case of no joint control. By selecting the posture, the virtual mass can be altered, but its variation may be minor. Then the impedance control is introduced to realize a wide range of impedance characteristics. Impedance matching is discussed for the case in which the hand of an impedance-controlled robot approached and collided with a passive target. The specific inertia property, referred to as Virtual-mass for Impedance Matching, is defined as an equivalent virtual mass of the hand that yields impedance matching with a target floating in space. Experiments are carried out using two robot manipulators as a motion simulator of chaser and target. Through the experiments, the concept of the impedance matching is verified and satellite capture is demonstrated using the strategy that an impedance controlled probe is inserted into the thruster nozzle cone of the target. Whether the impedance matching gives a criteria if the target is pushed away by the probe is investigated.

Experiences and lessons learned from the ETS-VII robot satellite

The National Space Development Agency of Japan (NASDA) launched the ETS-VII (Engineering Test Satellite No.7) on November 28, 1997 to conduct rendezvous docking and space robot technology experiments. ETS-VII is the worlds first satellite that used a robot arm on a satellite. The robot arm was 2 m long and was tele-operated from the on-ground control station. The mission of ETS-VII lasted for two years and brought may experiences and results. The paper summarizes experiences and results of the ETS-VII robot satellite.

Coordinated control of spacecraft attitude and its manipulator

When a robot arm is mounted on a satellite to perform tasks, satellite attitude must be stabilized to keep communication link and to generate electrical power from its solar panels. Most past studies about free-flying space robots assume that the satellite platform is uncontrolled. Since performance of the space qualified onboard computer is not enough to handle the complicated control system, coordinated control of the robot manipulator control system and the satellite attitude control system is proposed in this paper. The robot control system estimates the angular momentum which the robot arm will produce. The satellite attitude control system compensates the robot arms reaction by the feed forward momentum control. The robot control system also controls robot arm motion not to generate excess reaction against the satellite platform.

Ground-space bilateral teleoperation experiment using ETS-VII robot arm with direct kinesthetic coupling

A bilateral teleoperation experiment with ETS-VII was conducted on November 22, 1999. Round-trip time for communication between the NASDA ground station and ETS-VII was approximately six seconds. We constructed a bilateral teleoperator that is stable even under such a long time delay. Several experiments, such as slope tracing task and peg-in-hole task, were carried out. Experimental results showed that kinesthetic force feedback to the operator is helpful even under such long time delay and improves the performance of the task.

Satellite capturing strategy using agile Orbital Servicing Vehicle, Hyper-OSV

To realize practical orbital servicing missions in the 21/sup st/ century, we have developed a new system concept for an orbital servicing vehicle named Hyper-OSV (Orbital Servicing Vehicle), which has higher speed manipulation capability and larger operation area than OSVs that were proposed in the 1990s. The main feature of Hyper-OSV (HOSV) is the separation of the operation function and the long-term in-orbit surviving functions such as a solar panel and a large communication antenna. This releases HOSV from attitude restrictions and flexible dynamics and provides a large operation area. The second feature of HOSV is the reconfigurable function that allows HOSV to perform various orbital servicing missions. One of the most difficult missions of HOSV is the noncooperative satellite capture. Separation of the operation function and the long-term in-orbit survival functions gives HOSV an agile working ability. Thus, we have proposed a satellite capturing strategy using an agile orbital servicing vehicle like HOSV and have been conducting its feasibility study. This paper outlines Hyper-OSV first, and then presents the satellite capturing strategy using an agile orbital servicing vehicle and feasibility studies of the satellite capturing.

Tele-manipulation of a satellite mounted robot by an on-ground astronaut

An experiment to teleoperate a robot arm on a satellite from an onground control station was conducted by an astronaut who has extensive on-orbit experience in operating the Space Shuttles robotic arm. This experiment aimed to evaluate/compare a teleoperation system, which we developed, with the teleoperation system of the Space Shuttle Remote Manipulator System (SRMS). There was a time delay of about 6 seconds in the teleoperation control loop of the satellite-mounted robot. However, the teleoperation experiments were satisfactory conducted with helps of various operator assistance functions.

Development of an EVA end-effector, grapple fixtures and tools for the satellite mounted robot system

There are many tasks to be performed by space robots. However a single end-effector can not meet the individual tasks requirements. NASDA is to launch an experimental robot satellite named ETS-VII. The satellite has a 6-DOF robot-arm to handle many experimental payloads. Payloads vary in mass, shape and size. Interfaces between payloads and the end-effector are standardized using grapple fixtures. Additional tools with grapple fixtures are also developed to meet specific task requirements. This paper shows current status of the space-robots EVA end-effector and development result of the ETS-VIIs end-effector, grapple fixtures and tools.