A Structural Approach to Improve the Stability of Bilateral Control System with Time Delay

Abstract

Bilateral control is one of the control methods of teleoperation system. The presence of network delays between a master robot and a slave robot makes the design of bilateral control system challengeable. Because, it seriously deteriorates the performance and possibly makes the system unstable. The communication disturbance observer (CDOB) has been proposed to compensate time delay effect without a time delay model. The effectiveness of CDOB with acceleration based four-channel bilateral control system has been confirmed experimentally so far. The acceleration based four-channel bilateral control system utilizes the information of the master/slave position and force. Position and force control are realized in two decomposed virtual modal spaces, i.e. differential mode and common mode. In the acceleration based four-channel bilateral control system with CDOB, position control is stable, but force control is not stable. Thus, the control system is stable during free motion, but the system can be destabilized when the slave robot contacts with the environment. In this paper, a structural approach is applied to improve the stability of force control of bilateral control system. The proposed structure is derived from modal space analysis in differential mode and common mode. By using the proposed structure, position control and force control of the bilateral control system are stabilized. The validity is confirmed by experimental results in the case of constant delay and time varying delay.

A design of disturbance observer in frequency domain for robust control of time delay system

“…Proof. According to Lemma 1, the supposition of the lemma ensures (20) to hold. Then ( 20), (22), and ( 23) guarantee (18), thereby (17).…”

“…We can consider (19) for robust stability of closed loop system. But it is possible only when its right hand, defined as E(𝜔) in (20), is greater than zero for all frequencies.…”

“…This type of uncertain time delay often encounters in the control system designs such as bilateral teleoperator, process control, network control, vision control and it makes the control system design much more difficult. [16][17][18][19][20][21] There are some applications that have applied DOB to the time delay system. [22][23][24] In Reference 22 and later relevant studies, communication disturbance observer (CDOB) were introduced to compensate the time delay on the network and this method has been used in bilateral teleoperation system.…”

Recent advances and outlook in industrial instrumentation and mechatronics control

“…The disturbance observer (DOB) is often termed as the pronoun of motion control technology. Hence, majority of papers related to motion control in IEEJ J. IA are related to DOB .…”

“…These include the extended or modified DOB, and they estimate the special components in the disturbances. Advanced DOBs consist of the following types: The most significant advanced DOB is the reaction force observer (RFOB) , ,. This includes the assumption that a robot makes contact with an environment such as a flat wall.…”