Minimally invasive surgery (MIS) has developed greatly in the world of surgery in recent years. The use of robotic systems in this field has increased in the past decades. In this procedure, the surgeon requires excellent dexterity and precision. On the other hand, the patient requires safety and minimum incisions during the procedure. These have been the driving forces for the development of robotic systems for laparoscopic surgery. However, existing successful robotic systems have some common drawbacks: high cost, excessive complexity, heavy weight, and large size.
In this work, we focus on the design methodology for developing a robotic arm for minimally invasive surgery that meets all the requirements of the procedure. The aim of this project is to progress towards a next generation surgical robotic arm that reduces the weight and size of the system. Based on a comprehensive study of laparoscopic surgery, the design goals and requirements were defined.
The design is based on a novel division of the surgery into two sub-operations: a global passive positioning and a local active laparoscopic motion. This permits to reduce the overall size of the robotic arm and to develop specific functional mechanisms. The first mechanism allows the alignment of the incision point with the centre of rotation. It is light and intuitive to set up. The second mechanism is responsible for the active surgical movement and is inspired by the spherical linkage.
A complete kinematic analysis and optimization is performed to optimize the geometrical parameters of the mechanisms. The optimization is defined as a multifunctional optimization problem with the aggregation of objective functions, that increase compactness, reduce size, and avoid singularities. In addition, a workspace validation is presented. Motors, sensors, materials, and cross-sectional areas of all parts are selected and tested so that all requirements are satisfied.
Finally, a first prototype of the alignment mechanism is built and an experiment is conducted to prove the ease of setting up the robotic arm. The results demonstrate the ease of setting up the system and the simplicity of the steps for alignment. It also shows that the alignment mechanism is intuitive to use without extensive training.
The proposed robotic arm is suitable for appendectomy, cholecystectomy, and inguinal hernia surgery and has several advantages: It is smaller and lighter than commercially available robotic arms, weighting less than 3 kg and measuring 318 mm x 241.4 mm x 35 mm and 385 mm x 178 mm x 101 mm, and it is portable, as specified in the European standards. This modular design with a division into an alignment mechanism and a surgical mechanism has reduced the
size of the overall system and its complexity.