Concentric-tube Tendon-actuated Robots
Concentric-tube robots offer several advantages, including ease of actuation, high dexterity, follow-the-leader motion capabilities among others. But the pre-curved nature of the tubes that make up these robots result in curvature limitations, snapping instabilities, etc.
On the other hand, tendon-driven robots have variable curvatures, but are limited by a fixed number of joints. Concentric-tube tendon-actuated robots are a new paradigm of actuation in robotic surgical devices that offers unique advantages of variable curvatures and high number of degrees-of-freedom. In collaboration with the Dupont Lab, at Boston Children’s Hospital & Harvard Medical School, we’re modeling the behavior of these types of robots using the standard Cosserat Model framework. Our work is the first to model the bending, twisting and elongation that these tubes go through when their respective tendons are actuated.
Publications:
- Chitalia, Y., Donder, A., & Dupont, P. (2022). Modeling Telescoping Tendon-Actuated Continuum Robots (No. 8201). EasyChair.
- Chitalia, Y., Donder, A., & Dupont, P. (2023). Modeling Tendon-actuated Concentric Tube Robots. 2023 IEEE International Symposium on Medical Robotics (ISMR 2023). To Appear.
COAST Robotic Guidewire
The Co-Axially Aligned STeerable (COAST) guidewire is the newest version of a robotically steerable guidewire with an outer diameter of 0.4 mm. The guidewire has a single degree-of-freedom, and demonstrates follow-the-leader
motion along with feed-forward motion. The guidewire is able to achieve high curvatures at varying bending lengths. Therefore the guidewire can be used in minimally invasive surgical procedures involving pediatric carotid arteries,
peripheral artery disease procedures, or procedures involving navigating around the aortic bifurcation or the aortic arch.
Robotic Pediatric Neuroendoscope
The robotic pediatric neuroendoscope is a tendon-driven robotic tool with a handheld controller designed for minimally invasive surgeries for treating pediatric hydrocephalus.
The tool itself is a cylindrical tube of 1.93 mm (outer diameter) with two notch joints micromachined within it using a femtosecond laser (see laser setup and SEM image of joint to the left).
Both joints of the robotic tool are in the same plane, allowing the robot to make S-shaped curves in any plane (GIF to the left).
The plane of bending can further be changed by a rolling motion capability in the handheld controller (see CAD to the left). The resulting tool is controlled using a joystick located at the back end of the handheld controller.
Thus, the robotic tool and its controller are ergonomic in their design and fully compatible with existing endoscopes used in hydrocephalus cases.
Media Coverage:
- Steerable Robotic Instruments Could Help Pediatric Neurosurgeons, Research Horizons, July 2019.
Robotic Guidewire
In this project, we have designed and analyzed a 0.4 mm single degree-of-freedom and a 0.78 mm two degree-of-freedom robotic guidewire for cardiovascular applications. The guidewire makes use of a Femtosecond laser to micromachine notch joints into a Nitinol tube allowing it to bending in the plane of the notch joint with the application of a moment from a tendon. See the papers below for more static models and controls details of the guidewire.
Media Coverage:
Miniature Force Sensor
This work presents a photointerrupter based force sensing mechanism to implement a low-cost, high accuracy, and reliable sensor with a miniaturized design.
Most force sensors are either too bulky or if they are small, they usually have a narrow range of linear output and
are significantly vulnerable to external disturbances. This makes it difficult to use these sensors in precision force measurement and feedback control especially in handheld medical robotics.
The optimized geometry of the screen and a novel dual-screen arrangement are proposed to increase the linear range of the sensor output.
A dual-phototransistor signal acquisition is introduced to compensate the external disturbances and provides robust sensor output.
The sensor has the ability to measure forces up to 21 Newtons,
having 1.08% nonlinearity, 0.83% hysteresis, and 99.58% accuracy.
The proposed model and sensing mechanisms are experimentally validated.
Large Deflection Shape Sensing - Continuum Robots
Endovascular and endoscopic surgical procedures require micro-scale and meso-scale continuum robotic tools to navigate complex anatomical structures.
Previous work has failed at achieving large deflections at micro-scale and meso-scale robots. In this work, 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 compact sensor allows repeatable and reliable estimates of the shape of both scales of robots with minimal hysteresis. This sensor can measure curvatures as high as 145 /m, and can estimate shape even in the presence of external forces or kinematic uncertainties (see image (c) to the left).