Novel observers for compensation of communication delay in bilateral control systems

The problem of communication delay in bilateral or teleoperation systems is even more emphasized with the use of the internet for communication, which may give rise to loss of transparency and even instability. To address the problem, numerous methods have been proposed. This study is among the few recent studies taking a disturbance observer approach to the problem of time delay, and introduces a novel sliding-mode observer to overcome specifically the effects of communication delay in the feedback loop. The observer operates in combination with a PD+ controller which controls the system dynamics, while also compensating load torque uncertainties on the slave side. To this aim, an EKF based load estimation algorithm is performed on the slave side. The performance of this approach is tested with computer simulations for the teleoperation of a 1-DOF robotic arm. The simulations reveal an acceptable amount of accuracy and transparency between the estimated slave and actual slave position under both constant and random measurement delay and variable and step-type load variations on the slave side, motivating the use of the approach for internet-based bilateral control systems

Function based control for bilateral systems in tele-micromanipulation

Design of a motion control system should take into account (a) unconstrained motion performed without interaction with environment or any other system, and (b) constrained motion with system in contact with environment or other systems. Control in both cases can be formulated in terms of maintaining desired system configuration what makes essentially the same structure for common tasks: trajectory tracking, interaction force control, compliance control etc. The same design approach can be used to formulate control in bilateral systems aimed to maintain desired functional relations between human and environment through master and slave motion systems. Implementation of the methodology is currently being pursued with a custom built Tele-micromanipulation setup and preliminary results concerning force/position tracking and transparency between master and slave are clearly demonstrated

Scaled bilateral teleoperation using discrete-time sliding mode controller

In this paper, the design of a discrete-time slidingmode controller based on Lyapunov theory is presented along with a robust disturbance observer and is applied to a piezostage for high-precision motion. A linear model of a piezostage was used with nominal parameters to compensate the disturbance acting on the system in order to achieve nanometer accuracy. The effectiveness of the controller and disturbance observer is validated in terms of closed-loop position performance for nanometer references. The control structure has been applied to a scaled bilateral structure for the custom-built telemicromanipulation setup. A piezoresistive atomic force microscope cantilever with a built-in Wheatstone bridge is utilized to achieve the nanonewtonlevel interaction forces between the piezoresistive probe tip and the environment. Experimental results are provided for the nanonewton-range force sensing, and good agreement between the experimental data and the theoretical estimates has been demonstrated. Force/position tracking and transparency between the master and the slave has been clearly demonstrated after necessary scalin

Transparency in Port-Hamiltonian-Based Telemanipulation

After stability, transparency is the major issue in the design of a telemanipulation system. In this paper, we exploit the behavioral approach in order to provide an index for the evaluation of transparency in port-Hamiltonian-based teleoperators. Furthermore, we provide a transparency analysis of packet switching scattering-based communication channels

Predictive input delay compensation for motion control systems

This paper presents an analytical approach for the prediction of future motion to be used in input delay compensation of time-delayed motion control systems. The method makes use of the current and previous input values given to a nominally behaving system in order to realize the prediction of the future motion of that system. The generation of the future input is made through an integration which is realized in discrete time setting. Once the future input signal is created, it is used as the reference input of the remote system to enforce an input time delayed system, conduct a delay-free motion. Following the theoretical formulation, the proposed method is tested in experiments and the validity of the approach is verified