This article introduces the analysis and control of a meso-scale two degree-of-freedom robotic endoscopic tool body for minimally invasive surgeries. The design of the robotic tool uses two types of a tendon-driven joint known as a bending flexure joint that allows us to control each degree-of-freedom by minimizing interjoint coupling by design. Pure kinematic modeling and control for these robots may not provide precise control performance due to kinematic uncertainties arising from tendon elongation, tendon slacking, gear backlash, etc. We propose a static model for each of the joints of the robotic tool that avoids several of these problems. Depending on the direction of tendon tension application, the proximal joint displays considerable hysteresis due to the superelastic material characteristics and this is included in our static model. The statics of a highly compliant distal joint is also modeled and validated using finite element analysis and experimental data. Using these models, we develop a control system that comprises of a disturbance observer and the proposed static model to provide precise force control and compensate for joint hysteresis.

Manual navigation of a guidewire is the first step in endovascular interventions. However, this procedure is time consuming with uncertain results due to tortuous vascular anatomy. This letter introduces the design of a novel COaxially Aligned STeerable (COAST) guidewire robot that is 0.40 mm in diameter demonstrating variable curvature and independently controlled bending length of the distal end. The COAST design involves three coaxially aligned tubes with a single tendon running centrally through the length of robot. The outer tubes are made from micromachined nitinol allowing for tendon-driven bending of the robot at various segments of the robot, thereby enabling variable bending curvatures, while an inner stainless steel tube controls the bending length of the robot. By varying relative positions of the tubes and the tendon by insertion and retraction in the entire assembly, various joint lengths and curvatures can be achieved, which enables a follow-the-leader motion. We model the kinematics, statics, as well as the coupling within tubes of the COAST robot and develop a simple controller to control the distal tip of the robot. Finally, we experimentally demonstrate the ability of COAST guidewire to accurately navigate through phantom anatomical bifurcations and tortuous anatomy.

Endoscopy is often used to treat hydrocephalus, a common pediatric neurosurgical condition. Rigid endoscopic tools used in these procedures have many limitations. In this article, we propose four novel designs for a steerable two degree-of-freedom robotic tool body to be deployed through a rigid endoscope and a handheld controller for such a tool body. Each of these designs make use of tendon-driven joints known as asymmetric notch joints, while varying tendon routing techniques. Furthermore, we design a compact handheld controller for this steerable tool body, which consists of dc motors driving lead screws to actuate the tendons for each of the robot's joints. A disturbance observer-based control system for these motors is designed to allow the motor to reach the desired tendon displacements under various loading conditions. Next, we analyze the kinematics of the bidirectional asymmetric notch joint, deriving a relationship between the joint angle and corresponding tendon displacement. Finally, we test each of our four proposed designs for interjoint coupling and provide some insights into the results of our tests. We find that tendon routing strategies play an important role in minimizing tendon coupling for meso-scale continuum tendon-driven robots and combining the properties of each of these asymmetric joints can prove to be beneficial in improving the performance of such two degree-of-freedom robots.

Endovascular and endoscopic surgical procedures require micro-scale and meso-scale continuum robotic tools to navigate complex anatomical structures. In numerous studies, fiber Bragg grating (FBG) based shape sensing has been used for measuring the deflection of continuum robots on larger scales, but has proved to be a challenge for micro-scale and meso-scale robots with large deflections. In this letter, we have developed a sensor by mounting an FBG fiber within a micromachined nitinol tube whose neutral axis is shifted to one side due to the machining. This shifting of the neutral axis allows the FBG core to experience compressive strain when the tube bends. The fabrication method of the sensor has been explicitly detailed and the sensor has been tested with two tendon-driven micro-scale and meso-scale continuum robots with outer diameters of 0.41 mm and 1.93 mm respectively. The compact sensor allows repeatable and reliable estimates of the shape of both scales of robots with minimal hysteresis. We propose an analytical model to derive the curvature of the robot joints from FBG fiber strain and a static model that relates joint curvature to the tendon force. Finally, as proof-of-concept, we demonstrate the feasibility of our sensor assembly by combining tendon force feedback and the FBG strain feedback to generate reliable estimates of joint angles for the meso-scale robot.

This article presents a voice-controlled soft robotic hand exoskeleton for hand assistance. Cervical spinal cord injury results in a disruption of the nerve signals, causing paralysis and limited upper extremity function. The impairment significantly limits the completion of activities of daily living (ADL) due to the importance of hand function. Recently, there has been an increase in hand exoskeleton studies to provide active assistance for effective ADL completion. However, the design, control, and user interface (UI) of the devices remain a challenging issue. This article proposes a novel fabrication method for the wearable glove using high consistency rubber silicone and biomimetic tendon routing. The developed glove provides a robust, deformable, and optimal-fitting design for an individual’s hand with a weight of 131 g and five-degree-of-freedom motion for various ADLs. It provides a pinch force of 6.3 N and an object-level admittance controller was implemented for virtual grasping modalities. A smartphone app-based voice UI was developed to provide a truly portable and intuitive control system. Grasping experiments with a healthy participant were conducted to evaluate the system.