Enhancing Transparency of a Position-Exchange Teleoperator

Abstract

Dynamic properties of robotic manipulators, including inertia, damping, and friction, limit the transparency of a haptic-feedback teleoperator. In this paper, we develop a position-exchange controller to provide hapticfeedback for a surgical teleoperator. The controller consists of proportional controllers and model-based feedforward terms that cancel the dynamic properties of the manipulators. We show that the teleoperator transmits the impedance of a soft environment to the operator when the gains of the proportional controllers are very high and dynamic terms of the manipulators are canceled. However, the high gains and complete cancellation of the dynamic terms of the manipulators can make the teleoperator unstable. We use Llewellyn's criteria for absolute stability to limit the controller parameters to values that keep the teleoperator stable during interactions with any passive user and environment. Experimental results using a custom version of the da Vinci Surgical System show that 70% of the inertia of the slave manipulators during low-frequency motion and almost all static friction of the manipulators during sliding motion can be canceled.

Absolute stability analysis of sampled-data scaled bilateral teleoperation systems

“…Similar to passivity, the absolute stability approach assumes that the environment and the operator are passive but otherwise arbitrary. The absolute stability of a continuous-time two-port network can be assessed using Llewellyn's criterion (Mahvash and Okamura, 2007;Cho and Park, 2005;Abbott and Okamura, 2003). Recent studies have introduced geometric approaches inspired by criteria for unconditional stability of microwave systems to study the absolute stability of teleoperation systems (Haddadi and Hashtrudi-Zaad, 2009).…”

M-Width: Stability and Accuracy of Haptic Rendering of Virtual Mass

“…[1,6,7,10]. Virtual mass rendering has been previously explored for specific medical robotics scenarios, including dynamic compensation for a surgical teleoperator [14], and inertia compensation for a lower-leg exoskeleton [3]. Gil et al [11] explore inertia compensation by force feedforward for an impedance haptic device using additional sensors for acceleration estimation.…”

Force-Feedback Surgical Teleoperator: Controller Design and Palpation Experiments

“…Developing highly transparent force feedback for a surgical teleoperator is challenging because (1) the use of force sensor on the patient-side arm is limited for practical reasons, (2) the dynamic force of the arms of a surgical teleoperator is generally in the scale of the environment force, (3) link flexibility and the tendon elasticity reduce transparency, and (4) the trade-off between the transparency and stability of a teleoperator limit the controller performance [5] [6].…”

“…The palpated environment for the first task is designed to be similar to heart tissue with a calcified artery, and for the second task, similar to a prostate tissue with a cancerous tumor inside. The details of controller can be found in prior publications [5] [6]; this paper focuses on the system structure and evaluation.…”

“…The teleoperator system contains one master manipulator and one patient-side manipulator of the da Vinci surgical system [7] [8] ( Figure 1) provided by Intuitive Surgical, Inc., and a custom control system developed at the Johns Hopkins University [5][6].…”