RTLinux Based Bilateral Control System with Time Delay over Network

Abstract

In this paper, bilateral control system over networks is discussed and transmission delay issues are considered. This paper concerns on two subjects relating to transmission delay. The first one is how to realize real-time network transmission. Both systems; master and slave system run in RTLinux that is based on real time operating system. Thus, both systems should be connected to network device in real time as well. The other one is bilateral control system with transmission delay. In this paper, bilateral control system composed of disturbance observer and reaction force estimation observer is proposed. And the disturbance force from transmission time delay is compensated by disturbance observer. The validity of proposed control architecture is shown by experimental results. I. INTRODUCTION The Internet's spread has a great influence on our life. We can transmit various data, such as text, picture, voice and vision over the Internet and be provided with the In- ternet's services. Moreover, some researchers investigates force transmission through the Internet to accomplish teleoperation. Bilateral control is required for improvement of the teleoperation manipulability. Bilateral control is com- posed of the transmission information between a op- erator and environment. Accordingly, the operator can feel feed back force sensation and the force sensation makes manipulability improvement. Hence, the operator can conduct complex work operations in the remote place. The bilateral teleoperation system is expected to apply to various cases. In the place such as space, a new reactor, and the polar region, the bilateral teleoperation system is utilized. Recently, the bilateral teleoperation system is applied to robotic surgery system. In this paper, new bilateral robot system with network is proposed. The bilateral teleoperation system is characterized transmission delay between operator commands and re- sulting robot actions at a remote site over the network. The transmission delay makes the control performance of teleoperation system degrade. The most previous work dealt with teleoperation system including transmission delay was presented in 1965 (2). In 1989, Anderson and co-workers proposed a control law for teleoperators which overcomes the instability caused by transmission delay (3). The design of bilateral controller with transmission delay based on H∞ is introduced (4). This paper concerns on two subjects relating to trans- mission delay. The first one is how to realize real-time network transmission. Both systems; master and slave system run in RTLinux that is based on real time operating system. Both systems are connected to network device in real time with RTSocket. The other one is bilateral control system with transmission delay. And the disturbance force from transmission time delay is compensated by disturbance observer. Accordingly, the improvement of performance of the teleoperation system with transmission delay is realized. This paper starts the introduction of bilateral robot system. In Section III, real time network is described and RT-Socket is introduced. In Section IV, the compensation of the transmission delay is explained. In Section V, the whole bilateral robot system is expressed. The validity of proposed bilateral robot system is shown by experimental results in Section VI and finally conclusions are drawn in Section VII.