Based on the theory of multibody system dynamics, the spatial kinematics analysis of the Mcpherson independent suspension widely used in the car was carried out. A practical and simpler method was provided to reduce t...Based on the theory of multibody system dynamics, the spatial kinematics analysis of the Mcpherson independent suspension widely used in the car was carried out. A practical and simpler method was provided to reduce the number of the generalized coordinates and constraint functions. By solving the nonlinear equations, the motion of any points in the whole suspension and wheel system can be predicted, including the spatial changes of the wheel alignment parameters which are of great importance to the car performances.展开更多
Parallel robots are widely used in the academic and industrial fields. In spite of the numerous achievements in the design and dimensional synthesis of the low-mobility parallel robots, few research efforts are direct...Parallel robots are widely used in the academic and industrial fields. In spite of the numerous achievements in the design and dimensional synthesis of the low-mobility parallel robots, few research efforts are directed towards the asymmetric 3-DOF parallel robots whose end-effector can realize 2 translational and 1 rotational（2T1R） motion. In order to develop a manipulator with the capability of full circle rotation to enlarge the workspace, a new 2T1 R parallel mechanism is proposed. The modeling approach and kinematic analysis of this proposed mechanism are investigated. Using the method of vector analysis, the inverse kinematic equations are established. This is followed by a vigorous proof that this mechanism attains an annular workspace through its circular rotation and 2 dimensional translations. Taking the first order perturbation of the kinematic equations, the error Jacobian matrix which represents the mapping relationship between the error sources of geometric parameters and the end-effector position errors is derived. With consideration of the constraint conditions of pressure angles and feasible workspace, the dimensional synthesis is conducted with a goal to minimize the global comprehensive performance index. The dimension parameters making the mechanism to have optimal error mapping and kinematic performance are obtained through the optimization algorithm. All these research achievements lay the foundation for the prototype building of such kind of parallel robots.展开更多
Background： Joint line （JL） is a very important factor for total knee arthroplasty （TKA） to restore. The objective of this study was to evaluate the early clinical and kinematic results of TKAs with posterior-sta...Background： Joint line （JL） is a very important factor for total knee arthroplasty （TKA） to restore. The objective of this study was to evaluate the early clinical and kinematic results of TKAs with posterior-stabilized （PS） or cruciate retaining （CR） implants in which the JL was elevated postoperatively. Methods： Data were collected from patients who underwent TKA in our department between April 2011 and April 2014. The patients were divided into two groups based on the prosthesis they received （PS or CR）. At 1-year postoperatively, clinical outcomes were evaluated by the American Knee Society （AKS） knee score, AKS function score, and patella score. In vivo kinematic analysis after TKA was performed on all patients and a previously validated three-dimensional to two-dimensional image registration technique was used to obtain the kinematic data. Anteroposterior （AP） translation of the medial and lateral femoral condyles, and axial rotation relative to the tibial plateau, were analyzed. The data were assessed using the Mann-Whitney test. Results： At time of follow-up, there were differences in the AKS knee scores （P = 0.005）, AKS function scores （P = 0.025）, patella scores （P = 0.015）, and postoperative range of motions （P = 0.004） between the PS group and the CR group. In the PS group, the magnitude of AP translation for the medial and lateral condyle was 4.9 ± 3.0 mm and 12.8 ± 3.3 mm, respectively. Axial rotation of the tibial component relative to the femoral component was 12.9 ± 4.5°. In the CR group, the magnitude of AP translation for the medial and lateral condyle was 4.3 ±3.5 mm and 7.9 ± 4.2 mm, respectively. The axial rotation was 6.7 ± 5.9°. There were statistically different between PS group and CR group in kinematics postoperatively. Conclusion： Our results demonstrate that postoperative JL elevation had more adverse effects on the clinical and kinematic outcomes ofCR TKAs than PS TKAs.展开更多
文摘Based on the theory of multibody system dynamics, the spatial kinematics analysis of the Mcpherson independent suspension widely used in the car was carried out. A practical and simpler method was provided to reduce the number of the generalized coordinates and constraint functions. By solving the nonlinear equations, the motion of any points in the whole suspension and wheel system can be predicted, including the spatial changes of the wheel alignment parameters which are of great importance to the car performances.
基金Supported by National Natural Science Foundation of China(Grant No.51135008)
文摘Parallel robots are widely used in the academic and industrial fields. In spite of the numerous achievements in the design and dimensional synthesis of the low-mobility parallel robots, few research efforts are directed towards the asymmetric 3-DOF parallel robots whose end-effector can realize 2 translational and 1 rotational（2T1R） motion. In order to develop a manipulator with the capability of full circle rotation to enlarge the workspace, a new 2T1 R parallel mechanism is proposed. The modeling approach and kinematic analysis of this proposed mechanism are investigated. Using the method of vector analysis, the inverse kinematic equations are established. This is followed by a vigorous proof that this mechanism attains an annular workspace through its circular rotation and 2 dimensional translations. Taking the first order perturbation of the kinematic equations, the error Jacobian matrix which represents the mapping relationship between the error sources of geometric parameters and the end-effector position errors is derived. With consideration of the constraint conditions of pressure angles and feasible workspace, the dimensional synthesis is conducted with a goal to minimize the global comprehensive performance index. The dimension parameters making the mechanism to have optimal error mapping and kinematic performance are obtained through the optimization algorithm. All these research achievements lay the foundation for the prototype building of such kind of parallel robots.
基金Acknowledgments We would like to thank the subjects for their time and enthusiasm. We also thank our fluoroscopy technologist Qing-Hua Liu.This work was supported by a grant from the National Natural Science Foundation of China （No. 81472139）.
文摘Background： Joint line （JL） is a very important factor for total knee arthroplasty （TKA） to restore. The objective of this study was to evaluate the early clinical and kinematic results of TKAs with posterior-stabilized （PS） or cruciate retaining （CR） implants in which the JL was elevated postoperatively. Methods： Data were collected from patients who underwent TKA in our department between April 2011 and April 2014. The patients were divided into two groups based on the prosthesis they received （PS or CR）. At 1-year postoperatively, clinical outcomes were evaluated by the American Knee Society （AKS） knee score, AKS function score, and patella score. In vivo kinematic analysis after TKA was performed on all patients and a previously validated three-dimensional to two-dimensional image registration technique was used to obtain the kinematic data. Anteroposterior （AP） translation of the medial and lateral femoral condyles, and axial rotation relative to the tibial plateau, were analyzed. The data were assessed using the Mann-Whitney test. Results： At time of follow-up, there were differences in the AKS knee scores （P = 0.005）, AKS function scores （P = 0.025）, patella scores （P = 0.015）, and postoperative range of motions （P = 0.004） between the PS group and the CR group. In the PS group, the magnitude of AP translation for the medial and lateral condyle was 4.9 ± 3.0 mm and 12.8 ± 3.3 mm, respectively. Axial rotation of the tibial component relative to the femoral component was 12.9 ± 4.5°. In the CR group, the magnitude of AP translation for the medial and lateral condyle was 4.3 ±3.5 mm and 7.9 ± 4.2 mm, respectively. The axial rotation was 6.7 ± 5.9°. There were statistically different between PS group and CR group in kinematics postoperatively. Conclusion： Our results demonstrate that postoperative JL elevation had more adverse effects on the clinical and kinematic outcomes ofCR TKAs than PS TKAs.
