Disturbance Observer Based Sliding Mode Control for Robot-Assisted Minimally Invasive Surgical System with Stochastic Time Delay

Robot-assisted minimally invasive surgery has achieved great success due to its overwhelming advantages compared with traditional open surgery. However, there are still some disquieting issues that impair its high reliability and efficiency such as unaccessible force feedback, communication time delay and kinds of dynamic modeling error and uncertain nonlinearity. In this paper, disturbance observer is proposed to acquire the interaction force information between the slave manipulator and environment. At the same time, projection based gradient estimator is employed to online estimate the unknown environmental parameters. A novel communication architecture is designed which makes sure that the whole system can work well under varying stochastic time delay. The sliding mode control is utilized to make the tracking error as small as possible. Simulation results with estimated interaction force derived from disturbance observer show the effectiveness and satisfactory performance of the proposed scheme. Bilateral teleoperation experiment is carried out to verify the practicality of the developed algorithm.