【作者】 李鹏；

【导师】 顾宏斌；

【作者基本信息】 南京航空航天大学 ， 载运工具运用工程， 2012， 博士

【摘要】 针对现有分辨率和对比度高、视场角大、专业级立体显示的头盔显示器一般在使用过程中会出现运动不便，定位跟踪干扰大，有沉重感、束缚感和异物感等问题，本文以高精度与短延迟跟踪、低工作负荷的功能需求为目标，从提高头盔显示器佩戴舒适性的角度出发，提出了一种主要由6URHS并联机构和传统头盔显示器组成的新型虚拟现实设备——头盔伺服系统（Helmet Mounted Display with6DOF Parallel Manipulator，以下简称HMDPM），并对该系统的若干关键技术进行了研究，具体有以下几个方面：1、执行机构的尺寸优化设计及原型样机研制。作为系统的运行执行机构，并联机构的结构尺寸将会直接影响到系统的运动特性。本文首先通过对实测数据进行量化与修正处理，得到了描述头部运动范围的六维超椭球体和头部运动速度、精度的极限数值，明确了执行机构尺寸优化的性能指标；其次，对各性能指标进行了归一化处理，定义了相应的子目标函数，建立了尺寸优化问题的数学模型，并提出了基于Centroidal Voronoi Tesselations（CVT）的非线性最小二乘法对优化问题进行了解算。计算结果显示，CVT的使用可以使参数初始值均匀覆盖整个参数空间，可在保持非线性最小二乘法原有优势的同时，提高算法的全局搜索能力，提供多组非劣解；再次，在执行机构的结构设计方面，提出了穿越式的驱动支链设计方案，减小了自身结构尺寸和安装占用空间，通过悬挂安装驱动支链保证了穿越式方案的实施，实践证明，机构的使用效果达到了设计目标；最后，按照最优方案完成了执行机构的设计研制。2、执行机构的运动学与动力学分析。分析了6URHS并联机构关节空间与任务空间之间的运动学关系；对螺母单独进行了动力学分析，推导了驱动支链的动力学方程，采用牛顿——欧拉法建立了部件级、细粒度的6URHS并联机构动力学模型；采用Simulink的Simmechanics模块建立了6URHS并联机构的虚拟样机，进行了开环动力学响应实验，实验结果显示数学模型与虚拟样机的动力学响应基本一致，数学模型的准确度与虚拟样机相仿。对6UPS并联机构模型与6URHS并联机构模型进行了能量转化分析，分析结果证明，考虑螺母的动力学特性，建立6URHS并联机构的动力学模型具有较高的必要性。3、系统重要未知参数的辨识。针对含头盔显示器的动平台质量、重心位置等参数具有时变不确定性的特点，本文重点对非线性系统的在线辨识算法进行了研究，通过理论分析和文献资料阅读，归纳、总结了部分辨识方法的优、缺点；结合待辨识参数和执行机构动力学模型，给出了用于参数辨识的系统状态空间模型和观测函数；通过在线辨识仿真，对比分析了连续-离散扩展卡尔曼滤波（CDEKF）算法和连续-离散无味卡尔曼滤波（CDUKF）算法的辨识速度、精度和稳定性，仿真结果显示CDUKF在这三方面均要优于CDEKF；采用CDUKF对HMDPM的动平台参数进行了在线辨识实验，实验结果显示CDUKF能对参数的阶跃变化作出快速响应，辨识误差较小，且阶跃变化越小，CDUKF的响应速度和辨识精度就越高。4、系统控制策略。针对系统的设计功能，提出了HMDPM的主动柔顺控制策略（ACCSH）；并对策略涉及的内容——运动轨迹规划和控制器设计进行了研究。鉴于螺旋副存在自锁问题，根据六自由度并联机构任务空间与关节空间的运动学关系，结合6UPS与6URHS各自驱动支链的运动特点，提出了基于6UPS并联机构驱动支链动力学模型和力传感器反馈数据的头部运动预测方法，该方法通过对头部运动的预测实现了对执行机构动平台运动轨迹的规划；针对系统设计功能之二——减小头盔显示器与使用者头部间的广义接触力，本文基于系统动力学模型，设计了带有惯性项与非线性项补偿的控制器；通过仿真与实验，对主动柔顺控制策略用于HMDPM控制的可行性与效果进行了验证，实验结果显示主动柔顺控制策略可以在实施精确位置跟踪的同时，有效地减小广义接触力，从而达到减小系统使用者工作负荷的系统设计目标。5、系统软件设计及其运行环境。按照功能划分，采用模块化的方法对系统软件架构进行了设计，基于Visual Studio实现了指令模块等17个功能模块，并根据任务需求将各模块有机结合，开发完成了系统管理软件、头部运动预测软件、在线辨识软件、系统控制软件以及动力学与运动学计算软件；基于C++Builder开发了系统管理软件的可视化操作界面，基于OpenGL设计了用于动态显示6URHS并联机构运动状态的虚拟样机，方便了测试实验的开展，保证了实验的安全性；基于Windows XP和RTX8.1搭建了系统软件的运行环境，设计了服务器（Windows）——客户端（RTX）的上、下位机控制架构，实现了HMDPM的480Hz的高频率实时控制。6、系统性能测试。构建了头盔伺服系统的原型样机，实现了系统硬件、软件的联合调试；采用仿真与实验相结合的方法，对HMDPM的设计功能实施效果和系统动力学响应等特性进行了研究。建立了有、无金属物体干扰两种跟踪性能测试实验环境，采用惯性陀螺测量了动平台的位姿信息，对电磁跟踪器与HMDPM的静、动态跟踪精确度、抗干扰能力和稳定性进行了对比，实验结果证实了HMDPM的良好跟踪性能；提出了基于动力学模型与力反馈数据的广义接触力计算方法，为通过实验手段验证ACCSH的实施效果提供了便利。参考了报告《AGARDAR-144》和《MIL-STD-1558》中关于飞行模拟机动感模拟平台的运动测试规范，设计了HMDPM运动特性极限等测试项目，完成了相关实验，并对实验结果进行了分析说明。更多还原

【Abstract】 At present, there are some disadvantages, such as bad ability of anti-jamming, increasement ofhuman working load in application of a kind of professional helmet mounted display which has highcontrast, big enough angle of field. A novel helmet mounted display----helmet mounted display witha6URHS parallel manipulator (HMDPM) which can solve problems above by mean of parallelmanipulator is proposed, and several principal researches on improving system funciton are developedin this paper.Firstly, a dimensional design and its corresponding methodology for6URHS is investigated whilecharacteristics of head motion are considered as design criterions. A metod that descripts scale of headmotion by six-dimensional hyperellipsoid is investigated, and the characteristics of head motion inflight training are summarized based on datum from many experiments. In practice, design criterionsare classified into compulsory requirements and relaxable requirements, and the objective functionsregarding the kinematic performances of the6URHS are defined according to all criterions, while themathematical model of optimization is established in accordance with the principle of nonlinear leastsquares. The paper presents a novel methodology--modified nonlinear least squares based onCentroidal Voronoi Tesselations(CVT)--which initializes the design parameters with CVT and solvesthe optimization problem by means of the nonlinear least squares method, thus obtaining severalfeasible solutions The numerical simulations show that each design solution satisfies all thecompulsory criterions and the new method has a better ability for global optimization. Additionally,the best solution is determined by taking into account the optimization of relaxable requirements--dexterity in workspace, and the feasibility of the new method is further verified by analyzing thepartial indices of the optimal mechanism. The prototype machine is manufactured according to theoptimal scheme.Secondly, the kinematic analysis for manipulator of6URHS is developed, and the kinematicrelationship between leading screw, nut and platform is derived. Dynamic analysis of leg is carried outusing Newton-Euler method, and the Newton-Euler equations of whole leg and corresponding partsincluding nut are established respectively, and then the closed-form dynamic equation of6URHSparallel manipulator is established. Virtual machine, dynamic models of6URHS are buildedrespectively by SIMULINK and M file, and some comparison experiments about dynamic responseare developed, the results of experiments show that the veracity of the dynamic models of6URHS isas the same as virtual machine’s. Additionally, it is proved that it is essential to established6URHSdynamic model considering the dynamic characteristics of nut.Thirdly, the parameter identification and cooresponding methodology of HMDPM platformincluding helmet is studied. Requirments about parameter identification method being fit for HMDPMare summarized in accordance with system construction and operation. Continuous-discrete extensionkalman filter and hybrid unscented kalman filter which are modified based on extension kalman filterand unscented kalman filter respectively to be used in identification of continuous-discrete hybridsystem are developed; Some contrastive analysises are done by mean of simulation, and results showthat continuous-discrete unscented kalman filter is more excellence than Continuous-discreteextension kalman filter on computation velocity and accuracy. Taking advantage ofcontinuous-discrete unscented kalman filter, the real value of platform parameters are obtained, and contrastive analysis betweent actual value and CAD mdel value of platform parameters is carried out,the reasons resulting in difference between actual value and model value are investigated, and anslysisresults show that the difference is the reflection of reality and continuous-discrete unscented kalmanfilter has qualification to identify parameters of HMDPM platform online.Forthly, an active compliance control strategy and its kernels for HMDPM are investigated. Themethodology of predicting head motion based on force feedback and dynamic model of extensible legof parallel manipulator is proposed to plan trajectory. Based on the relationship between the length ofextensible leg and the position and orientation of platform, the information of head motion ispredicted by means of sensor datum and solution of dynamic model of extensible leg, and then it isused to be the desired trajectory of HMDPM position control. The inertia term and nonlinear term ofHMDPM dynamic model are calculated, and the compensations of them are considered in design ofHMDPM controller so that the generalized contact force between head and helmet will be controlledeasily while tracking control of head is progressing. The SimMechanics module in MATLAB isadopted to construct human-robot interactive model of HMDPM, and the feasibility of novel controlstrategy is verified by developing some related numerical simulations. The simulations show that headmotion will be predicted rapidly and exactly using the presented method, the stiffness of HMDPM andgeneralized contact force are reduced evidently by compensating inertia term and nonlinear term inHMDPM controller while tracking control of head is conducted well, and user’s comfort is enhancedobviously. Method to calculate generalized contact force which is based on system dynamic modeland force feedbacks is developed, and is applicated in experiment to test the effience of activecompliance control strategy, experiment results show that both system stiffness and generalizedcontact force can be decreased by making use of active compliance control strategy, and humanworking load is reduced simultaneously. Quantized analysis of influence that have resulted fromdifferent experiment condition is done, and the impersonality of experiment is approved to be well.Fifthly, system softwares operation environment is established by combining RTX and WindwosXP, then the instantaneity and performance of system are promoted and the frequency of system canattain500~1000HZ. Based on Visual Studio, system softwares such as system management software,prediction of head motion software, online identification software and so on, are developed bymodularizing system functions, and the graphic user interface of system management software andvirtual machine showing kinematic status of6URHS are also developed respectively adopting C++Builder and OpenGL, so it is possible to evaluate the reliability and efficiency of methods beforeadoption in practice. Thereby, the security of system will be improved and hardwares can be protectedfrom damage which is due to unexpected case, and then the practicability of softwares is approved tobe fine.Finally, Some comparison experiments are developed and carried out to test the tracking precision,stability and ability of anti—jamming of traditional electromagnetic tracker and HMDPM, and theresults show that the former is better than the latter on all three test aspects in two test environmentswhich are classified by metal object existence, and there is a serious meansurement distortion forelectromagnetic tracker in metal object environment. Several test items that are designed to analyzesystem performance are constituted in accordance with report 《AGARDAR-144》和《MIL-STD-1558》.更多还原