获得大工作空间是并联机构设计中的一个重要目标,利用3种优化算法对并联机构工作空间体积进行优化,以6自由度机构6-RSS为例,建立优化模型,分析比较优化算法的性能。考察的性能指标主要有优化效果、数值稳定性、时间效率。涉及到的优化算法包括多岛遗传算法、广义简约梯度法、序列二次规划法,后两种算法在应用时与试验设计(Design of experiment,DOE)方法进行集成。试验分析表明,DOE结合局部优化算法的改进型优化方法有明显优势,优化后6-RSS并联机构的工作空间体积增加为原来的2.59倍,优化时间仅为多岛遗传算法的1/5,优化结果稳定。
Immersion and interaction are two key features of virtual reality systems, which are especially important for medical applications. Based on the requirement of motor skill training in dental surgery, haptic rendering method based on triangle model is investigated in this paper. Multi-rate haptic rendering architecture is proposed to solve the contradiction between fidelity and efficiency requirements. Realtime collision detection algorithm based on spatial partition and time coherence is utilized to enable fast contact determination. Proxy-based collision response algorithm is proposed to compute surface contact point. Cutting force model based on piecewise contact transition model is proposed for dental drilling simulation during tooth preparation. Velocity-driven levels of detail haptic rendering algorithm is proposed to maintain high update rate for complex scenes with a large number of triangles. Hapticvisual collocated dental training prototype is established using half-mirror solution. Typical dental operations have been realized including dental caries exploration, detection of boundary within dental cross-section plane, and dental drilling during tooth preparation. The haptic rendering method is a fundamental technology to improve immersion and interaction of virtual reality training systems, which is useful not only in dental training, but also in other surgical training systems.
WANG DangXiaoZHANG YuRuWANG YongLU PeiJunZHOU RenGeZHOU WanLin
