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Continuum Robots for Surgical Systems (CROSS)

Subject Area Automation, Mechatronics, Control Systems, Intelligent Technical Systems, Robotics
Term from 2013 to 2019
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 230187450
 
Final Report Year 2019

Final Report Abstract

The Emmy Noether Independent Junior Research Group CROSS investigated methods for concentric tube continuum robots (CTCR), which are the smallest among all continuum robots with typical diameter to length ratios of 1:250. The composition of concentrically arranged elastic tubes with precurvatures allows for simple, yet dextrous, robotic manipulators at a millimetre scale. The following research results were achieved: First, task-optimal design of CTCR was investigated. CTCR component tube parameters include the lengths, diameter, wall thickness, piecewise precurvatures, and material properties. The number of tubes can vary from two to four. Ad hoc selection of these design parameters based on task requirements is infeasible. To address this challenge, computational design optimization algorithms relying on swarm intelligence were developed such that multiple, competing objectives for task- and patientspecific requirements and constraints can be expressed. The methods were evaluated on different medical scenarios, including laser induced thermal therapy, minimally invasive hemorrhage evacuation, and transurethral kidney stone removal. Second, fundamental trajectory generation methods to be in incorporated in common motion planning frameworks were studied. This proved the necessity to consider the temporal order as well as the sequence of actuation. The course of motion in Cartesian space was further studied in terms of follow-the-leader capabilities, i.e. the shaft follows the course of the robot’s tip. The achieved results are significant for those surgical applications through natural orifices (transnasal or transuretheral) or conducted intraluminal (e.g. cochlear implant electrode insertion). Third, research on sensing methodologies for CTCR was conducted. The small diameter of CTCR poses challenging requirements on sensor selection. In this project, electromagnetic, vision- and fibre-based sensing means were analyzed and used in closed-loop control to compensate for model inaccuracies. A task hierarchy based control scheme serves as a foundation to coordinate motion in dual-arm CTCR systems. Fourth, human robot interfaces and assistive function were investigated. Thanks to their compliance, CTCR are inherently safe in direct contact with or in proximity to humans. As CTCR are continuously bending with many degrees of freedom, the control input and the resulting shape cannot be mentally related by the operator. To allow for different levels of autonomy, ranging from teleoperation over task autonomy to full automation, methods to perceive (3-D visual feedback, auditory feedback), interpret and reason (haptic feedback based on virtual fixtures, augmented reality), and act on a situation (teleoperation) proved effective in a series of user studies. Lastly, several robot prototypes were designed and constructed: A dual-arm CTCR system composed of two small footprint actuation units and a handheld actuation device accommodating three tubes. Furthermore the project lead to a patented continuum robot design. The design is inspired by the concentric tube principle, yet bending is achieved by tendon-actuation. The novelty of this robot design lies in the realization of extensible sections using magnetic repulsion forces within the tendonrouting disks. This novel design opens up new perspectives for continuum robots to be applied in confined environments, e.g. in-situ aircraft engine inspection. The research has been recognized by several scientific awards, including the Heinz Maier-Leibnitz Prize of DFG, Lower Saxony Science Award 2015, Nachwuchswissenschaftlerin des Jahres 2015 by academics and ZEIT, Engineering Science Prize 2016 by Berlin-Brandenburg Academy of Sciences and Humanities. The project has been recognized as an Elected Landmark in the Land of Ideas by the German Federal Government in 2017. The applicant was nominated as one of the Young Elite Top 40 under 40 in the Category Science and Society by the business magazine Capital in 2016, 2017, and 2018. In 2016 she was elected as a member of Junge Akademie and in 2019 as a Young Global Leader in the World Economic Forum.

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