【作者】 陈成军；

【导师】 周以齐；

【作者基本信息】 山东大学 ， 机械电子工程， 2008， 博士

【摘要】 力觉/触觉反馈技术可以使操作者通过反馈力感受虚拟模型的特征、约束和交互状态等,从而约束和引导操作者与虚拟环境进行实时交互。本文以单点型力觉/触觉反馈设备PHANToM^? Desktop作为交互接口,研究了基于力觉/触觉反馈的虚拟装配技术,以增强虚拟装配操作的拟实程度,提高虚拟装配的力觉/触觉沉浸感和交互性。本文的研究内容和方法对其它单点型力觉/触觉反馈设备的研究和应用同样具有参考意义。基于力觉/触觉反馈的虚拟装配技术是随着力觉/触觉反馈技术的不断进步,在无力觉/触觉反馈的虚拟装配技术的基础上发展起来的,它需要研究的问题包括:（1）面向虚拟装配的力觉/触觉反馈接口,（2）基于PHANToM的力觉/触觉反馈式虚拟装配交互方式,（3）基于力觉/触觉反馈的虚拟装配操作和导航方法等。本文首先研究了力觉/触觉反馈技术的基本原理,给出了力觉/触觉反馈式虚拟装配系统的框架,定义了系统各模块的基本功能。实现了SolidWorks格式的产品装配模型在虚拟装配系统中的重构,为开展基于力觉/触觉反馈的虚拟装配技术研究构造了虚拟装配环境。根据力觉/触觉渲染局部性强、多线程结构以及各线程刷新频率不同的特点,提出了基于碰撞检测的力觉/触觉渲染优化方法。该方法在主线程中动态构造代理点的方向包围盒,通过代理点方向包围与虚拟模型的碰撞检测,裁减掉代理点不可能“触摸”到的三角面片集;在碰撞检测线程中只渲染可能“触摸”到的三角面片集,提高了力觉/触觉渲染的效率和系统的稳定性。为增大虚拟装配操作工作空间,提高虚拟装配操作定位精度,提出了动态空间匹配方法,使代理点在远视点处具有较大的工作空间,近视点处具有较高的定位精度,提高了虚拟装配操作的可交互性。提出了面向虚拟装配操作的力觉/触觉反馈式虚拟机械手臂模型。根据6自由度机械手臂结构和PHANToM结构的相似性,构建了基于PHANToM关节驱动的6自由度虚拟机械手臂模型,为使该虚拟机械手臂模型具有力觉/触觉反馈功能,提出了基于机器人运动学分析的空间匹配方法。该模型可以在虚拟装配环境中交互模拟机械手臂的装配操作,丰富了虚拟装配系统的交互方式。基于6自由度虚拟机械手臂模型,提出了基于反馈力约束和引导的交互式机械手臂装配路径规划方法。在该方法中,操作者通过PHANToM控制虚拟机械手臂运动,在反馈力的引导下结合操作者的经验和决策能力,以虚拟示教的方式完成装配路径的粗略规划;自动优化阶段使用基于距离准则的单端搜索法对粗略路径进行自动优化;在手动优化阶段,机械手臂末端点的运动被反馈力约束到装配路径上,操作者可以使用力觉/触觉反馈设备交互地编辑路径和被操作对象的姿态;最后通过动画的形式模拟机械手臂的装配过程,以供用户对该路径进行评价。提高了械手臂装配路径规划的人机交互性。研究了基于力反馈的虚拟装配操作和导航方法。使用自由度转化和归约法将装配约束转化为运动自由度约束,应用质点-弹簧模型计算装配过程中的约束反馈力,解决了约束运动条件下代理点与虚拟物体分离的问题;研究了基于特征和规则的装配工具建模、定位和操作方法,建立了标准紧固零件库和标准紧固工具库,在此基础上实现了基于反馈力约束和引导的虚拟装配工具交互模型。研究了基于稳定性分析的交互式装配顺序规划方法。该方法通过装配约束矩阵、装配接触矩阵和装配支撑矩阵的转换,求解已装配零件的稳定性;根据已装配零件的稳定性、未装配零件的连接关系和装配方向等向操作者提示下一步应该装配的零件;操作者结合自己的装配经验和决策能力判断哪一个零件是下一步应该装配的零件,从而通过逐步推进的方法生成装配顺序。研究了基于客户端/服务器结构的力觉/触觉反馈式虚拟装配系统,提出了基于接触状态预测的协同式力觉/触觉渲染方法。该方法在服务器端预测基本的接触状态,客户端根据从服务器端接收到的接触状态和本地代理点的位置计算反馈力,并且发送给本地反馈设备输出,完成力觉/触觉渲染。该方法减轻了网络传输的数据量,减小了由于代理点位置预测误差和网络延迟扰动造成的反馈力计算误差,提高了协同式力觉/触觉反馈虚拟装配系统的稳定性。综合以上技术,本文设计了一个基于力觉/触觉反馈的虚拟装配原型系统,通过某加工中心动力头部件的装配过程说明了该原型系统的使用步骤,实例说明本文提出的相关方法是有效的。更多还原

【Abstract】 Force and haptic feedback technology provides operators with the ability of feeling features,constraints and interactions of virtual models,which enables them to interact with virtual environment in real-time way.In order to make virtual assembly （VA） interaction more real,this dissertation studied VA technology based on force and haptic feedback taking PHANToM^? Desktop,which is a kind of force and haptic feedback device of single point type,as the force and haptic feedback device.Both the research contents and the research methods in this dissertation can act as references for the research and application using other force and haptic feedback devices of single point type.With the development of force and haptic feedback technology,VA technology based on force and haptic feedback is developed on the base of VA technology with no force and haptic feedback.Comparing with no force and haptic feedback one,the VA technology based on force and haptic feedback should study three additional issues, which are the force and haptic feedback interface oriented to VA operation,the interaction manners of VA based on PHANTOM device and the assembly operation and navigation based on force-feedback.At the beginning of this dissertation,the force and haptic feedbacktheory was studied,then the framework of the VA system based on force and haptic feedback was presented,and the functions of each module were also defined.In order to conduct research on VA technology based on force and haptic feedback,the first step is to construct VA environment.This paper turned SolidWorks models into VA models, which provided a base for further study of VA technology based on force and haptic feedback.Based on the analysis of the characters and frame of force and haptic feedback rendering algorithm,an optimization method based on collision detection was presented.In the main process,a bounding box is constructed dynamically according to the state of 3-D cursor.Then an improved oriented bounding box（OBB） collision detection method is used to reduce the untouchable triangle collections,and the remnant triangle collections are rendered in collision detection process,so the efficiency of the haptic rendering algorithm has been improved.According to the needs of wide workspace and high position resolution of VA operation using PHANTOM device,a dynamic workspace mapping method with variable parameter was also presented.In this method the proxy far from the viewpoint has larger workspace,and the proxy near the viewpoint has more accurate position precision.In order to simulate the assembly operations of the six-DOF（Degrees of Freedom） articulated robot arm in VA system,a six-DOF virtual robot arm driven by the PHANTOM device was modeled according to the structural similarity between the PHANTOM device and a six-DOF articulated robot arm.To enable the virtual robot arm to haptically interact with virtual prototypes in a virtual environment,a workspace mapping method based on robot kinematics analysis was also proposed.Based on the above-mentioned six-DOF virtual robot arm with force and haptic feedback,an assembly path planning method with virtual teaching and force feedback guiding was proposed.In this method,the guiding force is estimated using potential field method,and the virtual robot arm is driven by the PHANToM device manipulated by operator.With the help of both feedback force guideline and user’s experiences and decision-making ability,the rough path planning process is being conducted in a virtual teaching way.An improved optimal method is employed to optimize the rough path.At last,the assembly process along optimized path is shown in animation,which enables users to evaluate the path and assembly process.The VA operation and navigation method based on force-feedback was explored. The assembly constraints are transformed into DOF constraints,which are reduced next.The separation problem between the proxy and parts under constraint movement was solved.Spring-damping model is employed to estimated feedback force,so the operator can feel the existence of assembly constraints.The standard tools library as well as standard fastening pars library was established,then a force-feedback-based tool interaction model was presented. The assembly sequence planning based on stability analysis was studied.By the transition from assembly constraint matrix,assembly contact matrix to assembly support matrix,the stability of each assembled parts can be analyzed.According to the stability of assembled parts,the assembly constraints and assembly direction of the unassembled parts,the parts that probably be assembled is recommended to the operator.The operator can make a decision with his/her experience on which part should be assembled.So the assembly sequence can be obtained step by step.The framework of the collaborative VA system based on force and haptic feedback using client/server structure was studied,and a contact elements prediction-based haptic rendering method was proposed.This method is conducted at both server and client side.The server predicts the basic contact elements using haptic rendering model. At client side,according to the local proxy position and basic cntact elements received from server,the finial feedback force to be sent to the PHANTOM device is estimated under the invariability assumption of contact elements.This method could not only reduce the network transfer load greatly,but also reduce the effects of both proxy position prediction error and network jitter,and the stability of the presented collaborative VA system based on force and haptic feedback were enhanced.Combining with the above-mentioned technologies,a VA prototype system based on force and haptic feedback was designed,and the assembly procedure of the power devices of a machining center was set as example to introduce process of VA design. Both the efficiency of the proposed algorithm and the feasibility of the presented VA system based on force and haptic feedback were proved.更多还原