Abstract: Aiming at the safety of human-computer cooperative surgery in the robot-assisted long bone fracture reduction operation, a safety strategy of fracture reduction robot is proposed and is based on the envelope error of reduction path and improved artificial field method. According to the patient's CT scan data, the 3D digital model of the fracture is constructed by reverse modeling, and the A^* search algorithm is used to plan the obstacle avoidance reduction path. Based on the clinical surgical accuracy requirements and planned reduction path, an envelope error surface is constructed around the planned reduction path, and an improved artificial force field is proposed. A repulsive field is established on the envelope error surface formed by the countless enveloping circle, and a gravitational field is established at the end of the long bone. Then, the reduction robot is guided to perform a fracture reduction, and the operation of the robot-assisted fracture reduction operation is limited to the envelope error range of the planned path. The safety strategy of reduction robot based on the envelope error of reduction path is simulated for verification. For two situations of the fracture reduction path no obstacles and the obstacles situation, the simulation of the safety strategy of the reduction operation is carried out, respectively. Simulation results show that adopting the safety strategy based on the envelope error and the improved artificial force field method can ensure the reduction path completely fall within the range defined by the envelope error, which can completely avoid the obstacle, and the simulation path is very close to the planned path, which can effectively improve the safety and precision of the reduction robot operation.

Key words: fracture, reduction robot, path planning, envelope error, improved artificial force field, safety strategy