Towards delayed teleoperation with pneumatic master and slave for MRI

Over the last 50 years, master-slave teleoperation has become a widespread and successful field of research. This discipline explores how to perform tasks using a robot on an environment with haptic feedback about robot-environment interaction being provided to the human operator. Most of the master and slave manipulators used in teleoperation are electrically actuated. However, in some particular applications such as inside an MRI for image-guided surgery, ferromagnetic materials including electrical wiring is prohibited. Thus, nonferromagnetic actuators like pneumatic or hydraulic actuators are a solution to this problem. This specific application also requires teleoperation in the sense of “tele-actuation” because of the lack of space inside the MRI chamber to put the robot’s actuators and the presence of electrical components in pneumatic servovalves. In this paper, we study the case of a teleoperation system composed of two identical pneumatic cylinders (as the master and the slave) equipped with servovalves, making a symmetric teleoperation system. This serves as a one-degree-of-freedom system to outline the design and analysis in terms of teleoperation transparency and stability. Simulation and experimental results check the validity of the theory without and with classical transmission delays. • rPerfect gas constant: r = 8.314/0.029 J/(kg.K) • kPolytropic constant: k = 1.2 • TSupply temperature: T = 293.15 K • MMass of the load: M = 0.5 kg • SPiston area: S = 1.814.10−4 m • V0Dead volume: V0 = 10−6 m • PsSource pressure: Ps = 5.210 Pa • PeExhaust pressure: Pe = 10 Pa • bViscosity coefficient: b = 50 N/(m.s) • y(t)Load position, in m • ẏ(t)Load rate, in m/s • ÿ(t)Load acceleration, in m/s • `Stroke length with 0 < y < `, in m • Vp(t), Vn(t)Volumes of the chambers P and N , in m • Pp(t), Pn(t)Pressures in the chambers P and N , in Pa • qp(t), qn(t)Mass flow rates entering in the chambers P and N , in kg/s • fext(t)External longitudinal force exerted by the environment on the piston, in N