Optoelectronic shape sensing for flexible continuum robots

Abstract

The advancement of flexible continuum robots has enabled their use in complex environments such as minimally invasive surgery (MIS), industrial inspection, and aerospace maintenance. However, a key challenge remains in achieving real-time shape sensing for precise and stable control and navigation, due to the flexible and curvature-based nature of these robotic structures, as opposed to rigid robots. This research presents the use of optoelectronic sensors, more specifically, a photo-reflective sensing component, to develop a novel variation of shape sensing techniques, for integration into simple planar robot structures, as well as flexible tendon actuated robots. The sensing principle is based on proximity detection of the optoelectronic sensor to a reflector, a number of which are integrated into the robotic structures. As the robot moves, the proximity changes to the sensor are recorded as a voltage varying signal, which is used to estimate the curvature, or shape, of the robot. Optoelectronic shape sensing overcomes some of the shortcomings of the standard shape sensing: The sensing is non-contact, and based purely on light intensity detection, meaning the sensors are not affected by material properties or load limitations, so that calibration remains intact in almost any scenario. Real time sensing can be achieved through the sensors high sampling rate, which do not require an amplifier. Development of the shape sensing technique is presented, including sensor characterisation, theoretical modelling based on gaussian light intensity, development of experimental rigs and novel calibration platforms for planar and tendon actuated robots integrating this shape sensing, as well as eventual development of a novel technique to target improved shape sensor performance using specialised reflector shapes. The results demonstrate significant improvements in accuracy, miniaturisation, simplicity of integration, adaptability, and robustness, making optoelectronic shape sensing a viable alternative for future applications using continuum robots.