Localization method for vine robots
Growing robots (or vine robots) that achieve locomotion by extending from their tip, are inherently compliant and can safely navigate through constrained environments that prove challenging for traditional robots. However, the same compliance and tip-extension mechanism that enables this ability, also leads directly to challenges in their shape estimation and control. We have developed a low-cost, wireless, permanent magnet-based method for localizing the tip of these robots. A permanent magnet is placed at the robot tip, and an array of magneto-inductive sensors is used to measure the change in magnetic field as the robot moves through its workspace. We develop an approach to localization that combines analytical and machine learning techniques and show that it outperforms existing methods.
We are developing a novel tip-extending catheter that grows through vessels in a manner analogous to how plants grow, termed Vascular Internal Navigation by Extension (VINE). The VINE catheter efficiently navigates tight turns and extreme angles due to its low bending stiffness and lack of sliding friction with vessel walls. Further, the soft, growing construction of VINE catheters results in reduced force on the leading edge, potentially reducing the risk of arterial injury compared to standard push-catheters.
Despite the enhanced dexterity, vision, and control offered by robot-assisted minimally invasive surgical (RMIS) systems, the large size and high cost, as well as the inability to move in a highly curved path, limit the effectiveness of current commercial systems and motivate the development of another approach. Procedure- and patient-specific (i.e., personalized) robot design would allow for optimization of operations compared to the current, generic robots designed to perform many different procedures. The need for personalized surgical robots is particularly apparent when considering specialized groups of patients, such as pediatric or obese patients, whose anatomical differences may prove current template systems to be inadequate.
Our proposed workflow begins with preoperative CT scans of the patient. A 3D model of the anatomy in the area of interest can then be generated. The surgeon can then use a design interface (explained in more detail below) which we have developed to help him or her design a dexterous manipulator specific to that patient. We are focusing on using a class of snake-like continuum robots known as concentric tube robots for this dexterous manipulator. The surgeon's final design can be manufactured and subsequently used in the procedure.
3D Printed Concentric Tubes
We propose that concentric tube robots can be manufactured using 3D printing technology on a patient- and procedure-specific basis. We define the design requirements and manufacturing constraints for 3D printed concentric tube robots and experimentally demonstrate the capabilities of these robots. While numerous 3D printing technologies and materials can be used to create such robots, one successful example uses selective laser sintering to make an outer tube with a polyether block amide and uses stereolithography to make an inner tube with a polypropylene-like material.
Compact, Modular Actuation and Control System
To minimize invasiveness and maximize biocompatibility, the actuation units of flexible medical robots should be placed fully outside the patient’s body. We present a novel, compact, lightweight, modular actuation, and control system for driving a class of these flexible robots, known as concentric tube robots. A key feature of the design is the use of three-dimensional printed waffle gears to enable compact control of two degrees of freedom within each module. We measure the precision and accuracy of a single actuation module and demonstrate the ability of an integrated set of three actuation modules to control six degrees of freedom. The integrated system drives a three-tube concentric tube robot to reach a final tip position that is on average less than 2 mm from a given target. In addition, we show a handheld manifestation of the device and present its potential applications.
VR Surgeon Design Interface
Concentric tube robots have potential for use in a wide variety of surgical procedures due to their small size, dexterity, and ability to move in highly curved paths. Unlike most existing clinical robots, the design of these robots can be developed and manufactured on a patient- and procedure- specific basis. The design of concentric tube robots typically requires significant computation and optimization, and it remains unclear how the surgeon should be involved. We propose to use a virtual reality-based design environment for surgeons to easily and intuitively visualize and design a set of concentric tube robots for a specific patient and procedure. In this paper, we describe a novel patient-specific design process in the context of the virtual reality interface. We also show a resulting concentric tube robot design, created by a pediatric urologist to access a kidney stone in a pediatric patient.
Hapkit is an open-hardware haptic device designed to be very low-cost and easy to assemble. Hapkit allows users to input motions and feel programmed forces in one degree of freedom. This enables interactive simulation of virtual environments that represent realistic physics (such as springs and dampers) and creative new touch sensations (like textures and buttons). The Hapkit can be assembled using household tools, costs less than $50 for all components, including the microcontroller board, and is easily set up and programmed by novices. In Fall 2013 we piloteded the Hapkit in a new online class on haptics; this is the ideal topic on which to launch a laboratory course within the current online learning revolution.