Daisuke Haraguchi

A prototype of pneumatically-driven forceps manipulator with force sensing capability using a simple flexible joint

This paper presents the first prototype of pneumatically-driven forceps manipulator using a simple flexible joint with intrinsic force sensing. A high performance spring component with wire actuation is employed for two-degree of freedom (DOF) bending joint, and two-DOF tendon drive system is implemented by four pneumatic cylinders. Using a continuum model for the kinematics, a PD controller with static and dynamic compensation is designed for the position control, which shows a good performance at the sufficient working frequency for surgical operations. The forceps manipulator can estimate external forces using a disturbance observer. A link approximation model is introduced to design the observer as the first intuitive approach. The force estimation can be achieved with an accuracy of 0.2 N in the basic straight posture.

A Pneumatically Driven Surgical Manipulator With a Flexible Distal Joint Capable of Force Sensing

This paper presents a novel forceps manipulator for surgical robot systems. The forceps manipulator has a highly simplified flexible distal joint, which is actuated by push-pull motions of superelastic wires. Pneumatic cylinders are employed for its driving system to realize high backdrivability of the flexible mechanism, enabling external force estimation without using a force sensor. For the kinematic description, we newly introduce a three-degree-of-freedom (DOF) continuum model considering expansion and contraction of the flexible joint, which allows three-axis force sensing on the forceps tip. We also developed a practical dynamic model, including linear-approximated elastic forces and nonlinear friction forces dependent on the joint bending angle. Effectiveness of the dynamic model is validated by open-loop control performance of the joint angles. The position control system is designed using a PID-based cascade controller with a feedforward compensator based on the dynamic model. Resolution of the joint angle control is 1°, satisfying the requirement for laparoscopic surgery. An external force estimation algorithm is developed, which realizes the three-axis sensing of translational forces acting on the forceps tip. The rigid-link approximation model is also employed to treat the calculation in singular attitude, the straight position of the flexible joint. Effectiveness of the force estimator is experimentally validated using a force sensor in two cases. Estimation error is 0.37 N at maximum with a force in a radial direction, and the estimation performance using the three-DOF force estimator is much better than the one using a conventional two-DOF force estimator.

A Forceps Manipulator With Flexible 4-DOF Mechanism for Laparoscopic Surgery

In this paper, a forceps manipulator for minimally invasive surgery is developed. The developed forceps has 4-DOF inside the abdominal cavity so that pivoting motion around the entry point is reduced, avoiding the interference with other manipulators or surgeons. The 4-DOF motion is realized using flexible joints that are driven by push-pull wire of superelastic alloy, which make the mechanism of the forceps simple and, thus, low cost and reliable. Since the wires of the forceps are driven by compact pneumatic cylinders, the manipulator is lightweight and achieves high power-to-weight ratio. Kinematic and dynamic models of the proposed forceps are derived considering the flexibility of the joints and friction of the wires. A position control law of the endpoint of the forceps is shown and tracking performance is confirmed by an experiment.

Design of a 4-DOF forceps manipulator for robotic surgery

In this paper, mechanical design of a forceps manipulator for minimally invasive surgery is discussed. The discussed forceps manipulator has 4-DOF link mechanism inside the abdominal cavity so that pivoting motion around the insertion point is not required. The 4-DOF forceps consists of serially-connected two flexible joints to reduce the number of mechanical parts such as pins. The length of flexible joints is designed so that it covers the desired workspace. Workspace of forceps with several link parameters are calculated using the Monte Carlo method. The configuration which achieves the broadest workspace is selected according to the calculation results.