Achieving Dexterous Manipulation for Minimally Invasive Surgical Robots through the Use of Hydraulics

Existing robotic surgical platforms face limitations which include the balance between the scale of the robot and its capability in terms of range of motion, load capacity, and tool manipulation. These limitations can be overcome by taking advantage of fluid power as an enabling technology with its inherent power density and controllability. As a proof-of-concept for this approach, we are pursuing the design of a novel, dexterous robotic surgical tool targeted towards transgastric natural orifice surgery. The design for this hydraulic surgical platform and the corresponding analysis are presented to demonstrate the theoretical system performance in terms of tool positioning and input requirements. The design involves a combination of a novel 3D valve, hydraulic artificial muscles, and multi-segmented flexible manipulator arms that fit in the lumen of an endoscope. A dynamic model of the system is created. Numerical simulations show that a hydraulic endoscopic surgical robot can produce the desired performance without using large external manipulators such as those employed by conventional surgical robots. They also provide insight into the component interactions and input response of the system. Future work will include manufacturing a prototype to validate the concept and the numerical models. NOMENCLATURE A0 The orifice area of the control valve inlet orifice. A f The curtain area at the controlled valve outlet. ∗Address all correspondence to this author. b The length of each strand within the braided sheath of an artificial muscle actuator. Cd0 The discharge coefficient of the control valve inlet orifice. Cd f The discharge coefficient of the valve outlet. D The diameter of the artificial muscle actuator. DN The fixed diameter of the valve outlet. E Elastic modulus of the manipulator backbone material. Fa The contractile force produced by the artificial muscle actuator. Fb Force load at the distal end of the manipulator due to beam deformation. FL External force load applied at the distal end of the manipulator. Fx Total load in the transverse direction at the distal end of the manipulator. Fz Total load in the longitudinal direction at the distal end of the manipulator. g The gap between the orifice face and the flapper within the control valve. γ The angle of each strand of the braided sheath measured relative to the longitudinal axis of the actuator. I Second moment of area of the manipulator backbone. Ib Moment of inertia at the distal end of the manipulator. L The length of the manipulator backbone. La The overall length of the artificial muscle actuator. M Total moment at the distal end of the manipulator. m Mass at the distal end of the manipulator. Mb Internal moment of the beam. ASME 2012 5th Annual Dynamic Systems and Control Conference joint with the JSME 2012 11th Motion and Vibration Conference DSCC2012-MOVIC2012 1 Copyright © 2012 by ASME DSCC2012-MOVIC2012-8685 October 17-19, 2012, Fort Lauderdale, Florida, USA ML External moment load applied at the distal end of the manipulator. n The number of turns completed by one strand within the braided sheath of an artificial muscle actuator. Pa The internal pressure of the artificial muscle actuator measured relative to the external pressure. PE Potential energy within the beam for any arbitrary beam shape. Ps The supply pressure provided to the control valve. Qa Flow rate of fluid entering or exiting the actuator. Q1 Flow rate of fluid entering the control valve. Q2 Flow rate of fluid passing through the controlled flow restriction and exiting the control valve. r Radius of the routing discs on the manipulator backbone. ρ Density of the fluid. s Position coordinate along the manipulator backbone. Varies from 0 to L. θ Angular orientation of the beam cross-section. V The internal volume of the artificial muscle actuator. x Beam position in the transverse direction. z Beam position in the longitudinal direction.