The kinematic model parameter deviation is the main factor affecting the positioning accuracy of neurosurgical robots. To obtain more realistic kinematic model parameters, this paper proposes an automatic parameters identification and accuracy evaluation method. First, an identification equation contains all robot kinematics parameter was established. Second, a multiple-pivot strategy was proposed to find the relationship between end-effector and tracking marker. Then, the relative distance error and the inverse kinematic coincidence error were designed to evaluate the identification accuracy. Finally, an automatic robot parameter identification and accuracy evaluation system were developed. We tested our method on both laboratory prototypes and real neurosurgical robots. The results show that this method can realize the neurosurgical robot kinematics model parameters identification and evaluation stably and quickly. Using the identified parameters to control the robot can reduce the robot relative distance error by 33.96% and the inverse kinematics consistency error by 67.30%.
In order to calibrate the hand-eye transformation of the surgical robot and laser range finder (LRF), a calibration algorithm based on a planar template was designed. A mathematical model of the planar template had been given and the approach to address the equations had been derived. Aiming at the problems of the measurement error in a practical system, we proposed a new algorithm for selecting coplanar data. This algorithm can effectively eliminate considerable measurement error data to improve the calibration accuracy. Furthermore, three orthogonal planes were used to improve the calibration accuracy, in which a nonlinear optimization for hand-eye calibration was used. With the purpose of verifying the calibration precision, we used the LRF to measure some fixed points in different directions and a cuboid’s surfaces. Experimental results indicated that the precision of a single planar template method was (1.37±0.24) mm, and that of the three orthogonal planes method was (0.37±0.05) mm. Moreover, the mean FRE of three-dimensional (3D) points was 0.24 mm and mean TRE was 0.26 mm. The maximum angle measurement error was 0.4 degree. Experimental results show that the method presented in this paper is effective with high accuracy and can meet the requirements of surgical robot precise location.
Objective To evaluate the effectiveness and precision of the domestic total hip arthroplasty (THA)-assisted robotic system ROPA through artificial bone experiments. MethodsRobot-assisted THA was performed on 16 artificial bone models (8 left hips and 8 right hips) using the ROPA system. Preoperative CT scans were imported into the ROPA system for three-dimensional reconstruction and preoperative planning. Component size, acetabular cup position (anteversion and abduction angles), and osteotomy parameters (femoral neck osteotomy distance, offset, leg length discrepancy, and acetabular reaming bone volume) were recorded. Intraoperative probe verification accuracy, matching accuracy, remaining reaming distance, and remaining press-fit distance were documented. Postoperative three-dimensional scanning was performed to measure actual parameters, which were compared with planned values to calculate deviations. Results Osteotomy experiments were successfully completed on all 16 hip models. Component sizes were consistent with the preoperative plan in all 16 hip models. Deviations between actual and planned values were as follows: Anteversion angle was (0.79±1.69)° and abduction angle was (0.19±2.23)°. According to the initial position of acetabular cup, abduction angle was 40° and anteversion angle was 20°. The deviation of acetabular cup anteversion angle was (40.79±1.69)° and abduction angle was (20.19±2.23)°. All acetabular cups were implanted in the Lewinnek safe zone. The femoral neck osteotomy distance was (0.31±0.38) mm, the leg length discrepancy was (0.79±1.16) mm, the hip offset was (0.69±2.21) mm, and the acetabular fossa reaming bone volume was (0.03±0.06) mm, all of which met the acceptance criteria. The probe verification accuracy was (0.18±0.16) mm, the intraoperative registration accuracy was (0.50±0.22) mm, the remaining reaming distance was (?0.19±1.05) mm, and the remaining press-fit distance was (1.88±0.89) mm, all of which were in line with the expected design error range. Conclusion The domestic THA-assisted robotic system ROPA demonstrated favorable osteotomy accuracy, operational performance, effectiveness, and precision in artificial bone experiments. However, its long-term efficacy still requires further verification through clinical trials.