Design and integration of a parallel, soft robotic end-effector for extracorporeal ultrasound

Objective: In this work we address limitations in state-of-the-art ultrasound robots by designing and integrating a novel soft robotic system for ultrasound imaging. It employs the inherent qualities of soft fluidic actuators to establish safe, adaptable interaction between ultrasound probe and patient. Methods: We acquire clinical data to determine the movement ranges and force levels required in prenatal foetal ultrasound imaging and design the soft robotic end-effector accordingly. We verify its mechanical characteristics, derive and validate a kinetostatic model and demonstrate controllability and imaging capabilities on an ultrasound phantom. Results: The soft robot exhibits the desired stiffness characteristics and is able to reach 100% of the required workspace when no external force is present, and 95% of the workspace when considering its compliance. The model can accurately predict the end-effector pose with a mean error of 1.18+/-0.29mm in position and 0.92+/-0.47deg in orientation. The derived controller is, with an average position error of 0.39mm, able to track a target pose efficiently without and with externally applied loads. Ultrasound images acquired with the system are of equally good quality compared to a manual sonographer scan. Conclusion: The system is able to withstand loads commonly applied during foetal ultrasound scans and remains controllable with a motion range similar to manual scanning. Significance: The proposed soft robot presents a safe, cost-effective solution to offloading sonographers in day-to-day scanning routines. The design and modelling paradigms are greatly generalizable and particularly suitable for designing soft robots for physical interaction tasks

Three-Axis Fiber-Optic Body Force Sensor for Flexible Manipulators

This paper proposes a force/torque sensor structure that can be easily integrated with a flexible manipulator structure. The sensor’s ring-like structure with its hollow inner section provides ample space for auxiliary components, such as cables and tubes, to be passed through and, hence, is very suitable for integration with tendon-driven and fluid-actuated manipulators. The sensor structure can also accommodate the wiring for a distributed sensor system as well as for diagnostic instruments that may be incorporated in the manipulator. Employing a sensing approach based on optical fibers as done here allows for the creation of sensors that are free of electrical currents at the point of sensing and immune to magnetic fields. These sensors are inherently safe when used in the close vicinity of humans and their measuring performance is not impaired when they are operated in or nearby machines such as magnetic resonance imaging (MRI) scanners. This type of sensor concept is particularly suitable for inclusion in instruments and robotic tools for minimally invasive surgery (MIS). The paper summarizes the design, integration challenges and calibration of the proposed optical three-axis force sensor. The experimental results confirm the effectiveness of our optical sensing approach and show that after calibrating its stiffness matrix, force and momentum components can be determined accurately

Motion Control of Cable-Driven Continuum Catheter Robot through Contacts

International audienceCatheter-based intervention plays an important role in minimally invasive surgery. For the closed-loop control of catheter robot through contacts, the loss of contact sensing along the entire catheter might result in task failure. To deal with this problem, we propose a decoupled motion control strategy which allows to control insertion and bending independently. We model the catheter robot and the contacts using the Finite Element Method. Then, we combine the simulated system and the real system for the closed-loop motion control. The control inputs are computed by solving a quadratic programming (QP) problem with a linear complementarity problem (LCP). A simplified method is proposed to solve this optimization problem by converting it into a standard QP problem. Using the proposed strategy, not only the control inputs but also the contact forces along the entire catheter can be computed without using force sensors. Finally, we validate the proposed methods using both simulation and experiments on a cable-driven continuum catheter robot for the real-time motion control through contacts

A vision-based soft somatosensory system for distributed pressure and temperature sensing

Emulating a human-like somatosensory system in instruments such as robotic hands and surgical grippers has the potential to revolutionize these domains. Using a combination of different sensing modalities is problematic due to the limited space and incompatibility of these sensing principles. Therefore, in contrast to the natural world, it is currently difficult to concurrently measure the force, geometry, and temperature of contact in conventional tactile sensing. To this end, here we present a soft multifunctional tactile sensing principle. The temperature is estimated using a thermochromic liquid crystal ink layer which exhibits colour variation under temperature change. The shape and force of contact is estimated through the 3D reconstruction of a deformed soft silicone surface. Our experiments have demonstrated high accuracy in all three modalities, which can be measured at the same time. The resolution of the distributed force and temperature sensing was found to be 0.7N and 0.4℃ respectively

Model-Free Position Control for Cardiac Ablation Catheter Steering Using Electromagnetic Position Tracking and Tension Feedback

Cardiac ablation therapy is an effective minimally invasive treatment for cardiac arrhythmia. Catheter steering in the constrained environment during the procedure is considered difficult, particularly in providing accurate catheter tip positioning for ablating or for diagnosing the cardiac tissue. These difficulties and inaccuracies in the catheter tip positioning are a common reason for severe complications and a prolonged duration of the procedure. To improve the maneuverability and hence the accuracy of the catheter tip navigation, a model-free catheter tip position control with a new robotic catheter system is proposed in this article. A model-free tension control algorithm for steering the catheter has been developed and implemented in the robot. As seen in the experimental validation of the system, the model-free control is able to minimize position error up to 0.5 ± 0.2 mm from 80 mm position error within 7 ± 2 s. Furthermore, it shows the capability to react efficiently to external disturbances, such as external contacts or unwanted catheter shaft movement