CARPE (Compliant Actuation Robotic Platform for Flexible Endoscopy, www.carpeproject.eu) project proposed a design of a new generation of active flexible colonoscope. This design relies on novel and patented mini hollow compliant (MCA) actuator (UK patent application no.1407490.0) by using Shape Memory Alloy (SMA) wires in antagonistic configuration, providing two degrees of freedom (DoFs) with intersecting axes, roll and pitch. In contrast to the traditional flexible passive colonoscope, CARPE when developed would be capable of active locomotion through an independent control of the component MCA with use of an embedded miniaturised electronics hardware and sensors systems. This active control would produce a snake-like locomotion reducing the force exchanged with the colonic walls, thereby reducing substantially the pain and discomfort of the traditional colonoscopy performed with conventional colonoscopes. Additionally, the use of an external console for guidance will facilitate execution of the procedure and reduce the learning process for the acquisition of proficiency in performance of the procedure.
The R & D by the project team effort was focused on improvement of a preliminary MCA prototype, by producing a compact and metal version with an overall diameter of only 13 mm, total height of 15 mm and a total weight of circa 1 g.
Both, the mechanical actuation/transmission and the smart control board (SCB) are located in the outer part of the design, keeping the core of the articulated chain empty. This resulting central space has a diameter of 5 mm, and extends the entire length of the device. It will be used to house essential services such as suction/irrigation and biopsy channel for a traditional biopsy or additional instruments. The proximal end of the robot has been designed to carry a HD camera (already developed) and the robot will be controlled from an external console.
Light material, i.e. titanium and aluminum, were utilized to achieve a light MCA frame of only 0.8 g to obtain a high force/torque to weight ratio. Pulleys with miniaturized ball bearings have been adopted to reduce the overall length of the joint and to minimize friction in the transmission mechanism.
Position sensors were needed to overcome the well known limitation in SMA control related to the hysteresis and the heat behaviour. These were located in each joint with an ad-hoc contact less design to reduce any additional friction and to increase the MCA output torque. This sensory system provides a feedback needed for precise control of the position and orientation of CARPE robotic device inside the colon.
The on-board smart control board was designed by using a DSP (digital signal processor) in which, a dedicated firmware is implemented to share all the required information with an external console. Additionally, an inertial measurement unit (IMU) with 3D accelerometer, gyroscope and magnetometer, is incorporated in the SCB to define the position of the robot inside the colon.
A preliminary prototype with 5 MCA has been produced and tested showing high dexterity, low power consumption and fast movement overcoming the traditional issues related to the SMA actuation system.
The entire surface of the articulated robot is covered by a flexible skin to prevent any contamination of the internal components of CARPE with the colon environment. Stretchable sensors embedded into the skin were also investigated to add more information for detection of the force exchanged against the colon wall in order to reduce pain experienced by the patient during the colonoscopy procedure. Preliminary experiments have confirmed high sensitivity and complaint behaviour, although further improvements are needed to improve the overall reliability.
Throughout the conduct timeline of CARPE project, the outcomes of the R & D at the various stages were presented in various conferences, i.e. Actuator Bremen, SAGES Boston and EAES Amsterdam (as invited speaker) in the 2016, and in industry as well, Rethinking Robotics in Boston, with highly favourable positive comments positive and useful feedbacks from the scientific audience. Additional presentations of CAPRE were held at the University of Dundee and at the IMechE (institution of mechanical engineers) in Dundee.
Regarding future product commercialisation, results were discussed and presented periodically to a well-known major European company considered one of the market leaders in technologies for surgical endoscopy. This company has expressed great interest to take over the project for product commercialisation. A final demo to the company will be presented at a meeting in April 2017 to which all the Senior Executives and the CEO of the company will attend.
