The dynamic modeling and trajectory tracking control of a mobile robot is handled by a hierarchical constraint approach in this study. When the wheeled mobile robot with complex generalized coordinates has structural constraints and motion constraints, the number of constraints is large and the properties of them are different. Therefore, it is difficult to get the dynamic model and trajectory tracking control force of the wheeled mobile robot at the same time. To solve the aforementioned problem, a creative hierarchical constraint approach based on the Udwadia–Kalaba theory is proposed. In this approach, constraints are classified into two levels, structural constraints are the first level and motion constraints are the second level. In the second level constraint, arbitrary initial conditions may cause the trajectory to diverge. Thus, we propose the asymptotic convergence criterion to deal with it. Then, the analytical dynamic equation and trajectory tracking control force of the wheeled mobile robot can be obtained simultaneously. To verify the effectiveness and accuracy of this methodology, a numerical simulation of a three-wheeled mobile robot is carried out.
Artificial cervical disc replacement surgery has become an effective and main treatment method for cervical disease, which has become a more common and serious problem for people with sedentary work. To improve cervical disc replacement surgery significantly, a 6-DOF parallel bone-grinding robot is developed for cervical bone-grinding by image navigation and surgical plan. The bone-grinding robot including mechanical design and low level control is designed. The bone-grinding robot navigation is realized by optical positioning with spatial registration coordinate system defined. And a parametric robot bone-grinding plan and high level control have been developed for plane grinding for cervical top endplate and tail endplate grinding by a cylindrical grinding drill and spherical grinding for two articular surfaces of bones by a ball grinding drill. Finally, the surgical flow for a robot-assisted cervical disc replacement surgery procedure is present. The final experiments results verified the key technologies and performance of the robot-assisted surgery system concept excellently, which points out a promising clinical application with higher operability. Finally, study innovations, study limitations, and future works of this present study are discussed, and conclusions of this paper are also summarized further. This bone-grinding robot is still in the initial stage, and there are many problems to be solved from a clinical point of view. Moreover, the technique is promising and can give a good support for surgeons in future clinical work.
In computer assisted surgery, one of the most important problems is to align the
For the registration between the preoperative computed tomography (CT) image and the intraoperative patient space in surgical navigation technology, this paper puts forward a registration technique based on the principal component analysis (PCA) and the iterative closest point (ICP) algorithm, using two feature point clouds from the medical image space and the actual patient space. Firstly, the feature point cloud of the image space was obtained through the reconstruction, segmentation and interactive operation of the CT image, while the corresponding feature point cloud in the actual patient space was collected by the optical locator in real time. Secondly, the eigenvectors of the two sets of point clouds were obtained through the PCA for rough registration, and the optimal solution of the registration matrix was found by the ICP. Finally, the effect of the proposed registration method was verified against point cloud data (the surgical navigation accuracy was evaluated through an experiment on the vertebra model), and the impacts of the number of point clouds and Gaussian noise on the registration error were investigated in details. The results show that the proposed method is simple and capable of realizing high registration accuracy, and completed registration with a less-than-2mm error in our experiment; in addition, the registration accuracy was greatly affected by the number of point clouds and the noise of the photoelectric locator. This research provides a general solution for registration in surgical navigation and lays the theoretical basis for improving intraoperative registration accuracy. RÉSUMÉ. Pour l'enregistrement entre l'image tomodensitométrique préopératoire et l'espace patient peropé ratoire dans la technologie de navigation chirurgicale,cet article propose une technique d'enregistrement basé e sur l'analyse en composantes principales (PCA) et l'algorithme de 'iterative closest point' (ICP), utilisant deux nuages de points caractéristiques de l'espace image mé dical et de l'espace patient ré el.Tout d'abord, le nuage de point caracté ristique de l'espace image a é té obtenu par la reconstruction, la segmentation et le
The visualization and real-time tracking technologies of the probe in surgical navigation system are studied. The electromagnetic positioning method is introduced, and the probe with data acquisition function is designed based on electromagnetic positioning. Firstly, the probe model is constructed by means of three-dimensional solid modeling technology, and the transformation from the solid geometry model to the three-dimensional surface models is completed. Secondly, the probe tip is registered using the pivot calibration method and the registration accuracy is also tested. Then, the registration between the CT model and the patients site is realized intraoperatively by means of iterative closest point (ICP) algorithm, and simulation analysis and accuracy verification are carried out. Finally, according to the preoperatively registered position and orientation, the spatial location of the probe is tracked in real-time and accurately, and is displayed in the system. The results show that the data acquisition function and registration accuracy of the probe, as well as the effect of registration algorithms can meet the needs for surgical navigation.
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