Nonlinear bilateral teleoperators under event‐driven communication with constant time delays

Abstract

Bilateral teleoperation systems provide a platform for human operators to remotely manipulate slave robots in engaging various tasks in remote environments. Most of the previous studies in bilateral teleoperation were developed under continuous transmission or periodic communication with fixed data exchanging rates. This paper presents control schemes for bilateral teleoperation systems using nonperiodic event-driven communication. By using P-like and PD-like controllers, this study proposes triggering conditions for teleoperators to reduce network access frequency so that robots only transmit output signals when necessary. Stability and position tracking of the control system are studied, and nonzero minimum interevent time is guaranteed. The proposed event-driven teleoperation is studied with a velocity estimator to avoid the requirement of velocity information in the controller and triggering condition. Without velocity measurements, the boundedness of tracking errors and stability are ensured for teleoperation systems under event-driven communication.Simulations and experiments are illustrated to validate the performance of the proposed event-driven teleoperation systems.

A prescribed‐performance‐like control for improving tracking performance of networked robots

“…(2) How to avoid the Zeno behavior in such system? 2 In other words, in addition to selecting the appropriate initial value of i (t), what other measures need to be synchronized to eliminate Zeno behavior? (3) How to obtain the stability conditions for the resulting closed-loop system?…”

“… 1 (t) = diag[ 11 (t), 12 (t), … , 1n (t)] ∈ R n×n and  2 (t) = diag[ 21 (t), 22 (t), … , 2n (t)] ∈ R n×n are the switched rules of the designed auxiliary switching filters. Let {t 1 1,k } k≥0 and {t 2 2,k } k≥0 be the switching times of  1 (t) and  2 (t), respectively. Diacritical mark wedge denotes the estimation, for example,̂is the estimation of .…”

Event‐triggered control for adaptive bilateral teleoperators with communication delays

“…Theorem 2: Consider the bilateral teleoperation system, which is described by (25) with external force (24) and coordinating control (9). If the signals r^m(t) and r^s(t) are updated whenever the triggering conditions (11), (12) are satisfied, then the teleoperation system is stable and all trajectories of the control system are inputto-state stable (ISS).…”

“…Because network congestion is one of the crucial issues leading to instability in networked robotic and control systems, reducing data transmission frequency is expected to be a useful method to lower the communication burden. An event-triggered control strategy has brought a new aspect to networked system by updating control signals or transmitting information over the network when the system requires it [25]. Using event-triggered communication, output signals are exchanged between robots only if the triggering condition is satisfied, and the received signals are kept constant until the triggering condition is violated.…”

“…Many researchers have focused on event-triggered communication in multi-agent control in recent years [27][28][29][30]. Event-triggered control systems have proved to be powerful techniques in reducing communication burden under network uncertainties and limited bandwidth [25,27,30]. However, the advantages of event-triggered control have seldom been considered in bilateral teleoperation systems, except for the preliminary results of this paper [31].…”