Deployable, Variable Stiffness, Cable Driven Robot for Minimally Invasive Surgery

Abstract

Minimally Invasive Surgery (MIS) imposes a trade-off between non-invasive access and surgical capability. Treatment of early gastric cancers over 20 mm in diameter can be achieved by performing Endoscopic Submucosal Dissection (ESD) with a flexible endoscope; however, this procedure is technically challenging, suffers from extended operation times and requires extensive training. To facilitate the ESD procedure, we have created a deployable cable driven robot that increases the surgical capabilities of the flexible endoscope while attempting to minimize the impact on the access that they offer. Using a low-profile inflatable support structure in the shape of a hollow hexagonal prism, our robot can fold around the flexible endoscope and, when the target site has been reached, achieve a 73.16% increase in volume and increase its radial stiffness. A sheath around the variable stiffness structure delivers a series of force transmission cables that connect to two independent tubular end-effectors through which standard flexible endoscopic instruments can pass and be anchored. Using a simple control scheme based on the length of each cable, the pose of the two instruments can be controlled by haptic controllers in each hand of the user. The forces exerted by a single instrument were measured, and a maximum magnitude of 8.29 N observed along a single axis. The working channels and tip control of the flexible endoscope remain in use in conjunction with our robot and were used during a procedure imitating the demands of ESD was successfully carried out by a novice user. Not only does this robot facilitate difficult surgical techniques, but it can be easily customized and rapidly produced at low cost due to a programmatic design approach.

Nonlinear energy-based control of soft continuum pneumatic manipulators

“…In the theoretical case of constant disturbances, this inequality can be further simplified as 4D 0 αk m > 1 which suggest that the parameters α and k m contribute alongside the physical damping parameter D 0 to the stability of the prescribed equilibrium. Finally, the third inequality in (32) indicates that a larger value of k i α is required for larger soft manipulators (i.e. with larger cross-section area of the internal chambers A).…”

“…The flexible micro actuator (FMA) has been one of the first designs to achieve bending on any plane due to pressurization of its internal chambers [37] so that a manipulator can be constructed with a single FMA, thus it has inspired various subsequent versions [17]. Other actuation strategies include dielectric elastomers [26,45], cables [32], and shapememory alloy [23,42]. In general, not all degrees of freedom (DOFs) in soft continuum manipulators are actuated.…”

Open Loop Position Control of Soft Hydraulic Actuators for Minimally Invasive Surgery

“…In practice, the sheet material that the soft actuators were made from did not behave exactly as described by the theory, and for this reason the original rectangular shape was redesigned. The laser welding manufacturing method from [9] was used, which enables rapid and low-cost manufacture. To take advantage of the manufacturing method's flexibility, a parametric design approach is followed that allows rapid customisation of the actuators.…”

“…The Cyclops robot is also made from materials more rigid than the soft tissues of the body. In [9], the metal support structure was replaced with an inflatable structure to improve integration with the endoscope and make the robot less invasive, using approaches from the field of soft robotics.…”

“…We have developed soft actuators with the aim of approaching these disadvantages and of building on the work in [9] to produce an entirely deployable cable-driven robot. The actuators have accurate and highly repeatable performance despite their simple manufacture and control.…”