Supernumerary Robotic Arm for Three-Handed Surgical Application: Behavioral Study and Design of Human-Machine Interface

In surgical to industrial manipulation, the operator needs assistance for tasks requiring more than two hands. Teamwork may be the source of errors and inefficiency, especially if the assistant is a novice or unfamiliar with the main operator. The need for assistance may become problematic in case of lack of human resources e.g. in emergency surgical cases in the late hours of the night. Our objective is to improve the surgeon's autonomy and dexterity by a robotic arm under his own control. Although a number of robotic instrument holders have been developed, the best way to control such devices is still an open question. No behavioral study has been conducted on the best control strategy and human performance in three-handed tasks. We have selected the foot for commanding the third arm on the basis of a literature review. A series of experiments in virtual environments has been conducted to study the feasibility of this choice. The first experiment compares performance in the same task using two or three hands. Results show that three-handed manipulation is preferred to two-handed manipulation in demanding tasks. The second experiment investigated the type of tasks to be aimed in three-handed manipulation and the learning curve of users. Moving the hands and a foot simultaneously in opposite directions was perceived as difficult compared to a more active task with liberty in choosing the limbs coordination. Limbs were moved in parallel rather than serially. The performance improved within a few minutes of practice. Also, the sense of ownership improved constantly during the experiment. Two other experiments were aimed at handling the endoscope in laparoscopic surgery. Surgeons and medical students participated in these studies. Residents had a more positive approach towards foot usage and performed better compared to more experienced surgeons. This proves that the best training period for surgeons to use a foot controlled robotic arm is during their residency. A realistic virtual abdominal cavity has been developed for the last experiment. This had a positive influence on the participants' performance and emphasizes the importance of using a familiar context for training such a "three-handed surgery". Finally, two different foot interfaces were developed to investigate the most intuitive third arm commanding strategy. A robotic arm is hence controlled by the foot's translation or rotation in one interface (isotonic interface), and by force or torque in the other one (isometric interface). An experimental behavioral study was conducted to compare the two devices. Isometric rate control was preferred to isotonic position control due to the lower physical burden and higher movement accuracy of the robot. It was shown that the proposed device for isometric rate control could be used for intuitive control of four DoFs of a slave robotic arm. This thesis is the first step in a systematic investigation of a three-handed manipulation, two biological hands and a foot controlled robotic assistant. Findings suggest a high potential in using the foot to become more autonomous in surgery as well as other fields. Users can learn the control paradigm in a short period of time with little mental and physical burden. We expect the developed foot interfaces to be the basis of future development of more intuitive control interfaces. We believe that foot controlled robotic arms will be commonly used in various surgical as well as industrial applications.