Optimization of a novel mechanism for a minimally invasive surgery robot

Background Minimally invasive surgery (MIS) has many advantages compared with open surgery, but there are still many drawbacks in performing MIS. Using robotic technologies, many problems caused by human restrictions, such as fatigue and low precision, can be solved. In this paper, a novel mechanism for a MIS robot is proposed. Methods Kinematics analysis was carried out and singularity and isotropy configurations were also investigated, based on kinematics equations. In order to evaluate the performance of the robot, a combined measure gave attention to the mean value and standard deviation of the reciprocal of the condition number. Optimization was achieved by maximizing the combined measure subjected to a set of constraints in the task workspace. The effectiveness of the measure was demonstrated by comparing the performance and volume of the optimized mechanism with those of the mechanism optimized by the Global Condition Index (GCI). Results The robot met the volume constraints with the dimensional parametera≤ 115 mm. The combined measure φ was maximized whenais 100 mm. The robots optimized by the GCI and the combined measure showed similar performance in terms of condition number, but the latter had advantages on volume compared with the former. Conclusions A novel mechanism that satisfied the incision point constraint of MIS was proposed. A systematic methodology for optimizing the mechanism was developed and the combined measure was effective to evaluate the performance. A prototype was set up based on the outcomes mentioned in the paper.