Development of an intuitive foot-machine interface for robotic surgery

• Main Author: Huang, Yanpei
• Other Authors: Phee Soo Jay, Louis
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/148981
• Institution: Nanyang Technological University

In robotic surgery, the surgeon controls the surgical robot through human-machine interfaces. The most common interfaces are for hands so that the surgeon can only control at most two robotic instruments at one time while three or more instruments may be needed at the same time in some procedures, e.g., robotic endoscopic/laparoscopic surgery. Current practices in these cases, i.e., having one assistant control the additional instrument, is not ideal because fine collaboration between the surgeon and the assistant is required, and delayed actions and even safety issues due to communication errors may occur. These limitations can be avoided if the surgeon could control all the tools on his/her own simultaneously. This thesis work developed a novel foot-controlled human-machine interface, enabling the surgeon to control the additional robotic surgical tool using the foot, together with the two tools that are controlled by the hands. This foot-controlled interface controls a robotic surgical instrument in continuous direction and speed based on the motion of the foot in four degrees of freedom (DoFs), i.e., foot left/right translation, forward/backward translation, lateral/medial rotation, and toe-up/down rotation. The foot force/position signals are collected through eight feedback-sensing modules of the interface surrounding the foot. Each feedback-sensing module consists of a spring and a load cell. The foot's position can be determined by the deformation of the springs which is calculated based on the forces measured by the load cells. The whole foot operation is separated into elastic and isometric modes. In the elastic mode, the springs are not fully compressed and thus the foot can move freely with reaction forces from the springs (i.e., passive force feedback); in the isometric mode, the foot’s motion is limited by the boundary (some springs are fully compressed) but its force is not limited and thus can still be used for output commands. The seamless transition between the two modes provides the user with rich proprioceptive information and meanwhile enlarges input ranges that are limited only by his/her strength. The interface also features a singularity-free workspace with a neutral central home position. The weight of the foot is well supported, and the friction of the interface is minimized to limit operation fatigue. An analytical model based on the kinematics and statics of the foot interface was derived for output command calculation; however, this model does not consider the distinct motion behaviors of different users. Therefore, a data-driven mapping approach using independent component analysis was proposed to adapt the interface to the specific user’s motion pattern, which effectively reduces the deviation between users. Three studies were conducted on the developed interface: (1) Controlling of an industrial robotic arm for path-tracking and button-pressing tasks and comparison to a foot button interface. The proposed interface was about 30% faster and 60% smoother than a conventional foot button interface. (2) Three-hand manipulation using the proposed foot interface and two commercial hand interfaces for virtual reality tasks. The subjects were able to reliably control three virtual tools to perform independent and coordinated tasks. (3) A three-limb robotic flexible endoscopic system using the foot interface. The system enables the surgeon to simultaneously control an endoscope and two surgical instruments by the foot and hands, respectively. The feasibility of this concept was confirmed through an ex-vivo trial on a porcine stomach. In addition, the three-limb teleoperation with hands and one foot was 43.7% faster in contrast to a clutch-based hand control scheme. The developed four-DoF foot interface enables one user to simultaneously control three robotic arms which otherwise require two operators, and it facilitates efficient and intuitive robot control. The interface may find wide applications in both surgical and industrial robotic systems, leading to reduced manpower, less communication errors, and improved efficiency.