4自由度冗余驱动并联机构运动学和工作空间分析

提出了能实现二维转动和二维移动的空间4-UPS-RPU4自由度冗余驱动并联机构,并对该机构进行了运动学和工作空间分析。4-UPS-RPU并联机构包含5条驱动分支,其中4条分支为UPS(虎克铰-移动副-球副)结构,1条分支为RPU(转动副-移动副-虎克铰)结构。建立了该机构的位置反解数学模型,推导出了该机构的速度雅可比矩阵和加速度分析表达式,求解了机构的位置反解、速度和加速度,并在此基础上分析该机构的工作空间。研究结果为4-UPS-RPU冗余驱动并联机构的实际应用提供了理论依据。     

潜入牵引式自动导引车运动特性分析

与驱动单元和车体刚性连接的传统结构及拖车结构不同,潜入牵引式自动导引车的驱动单元置于车体底部与车体柔性连接。针对车体的运动轨迹问题,建立了车体与所跟踪路径的位姿关系模型,根据车体的几何尺寸及所跟踪圆弧路径的圆心角和半径,推导出车体在世界坐标系中的位姿状态及保证纯滚动运动的最小转弯半径。针对车体负载运行的行驶性能问题,建立车体的动力学模型,求出忽略侧向力影响的条件,推导出车体的角加速度。车体位姿实验证明了所建车体运动学模型的正确性。动力特性实验表明,该种结构的自动导引车行驶稳定性较好。     

全解耦并联机构的运动学与工作空间分析

研究了一种改进型全解耦-平移两转动并联机构,导出了其运动学的正逆解解析式,并用Visual C＋＋6.0编程计算求得数值解,通过Surfacer软件得到并分析了位置工作空间形状及大小;与原机构在运动学正逆解数、解耦性与位置工作空间形状及大小、驱动等方面进行了比较,证实改进型机构比原机构具有更大、更健壮的位置工作空间且不易产生奇异位置.可使该类机型应用范围更广.     

四自由度混联机器人运动学分析与仿真

根据串联机构和并联机构的特点,以两平移一转动并联机构为主体,设计了一种四自由度混联机器人,该机器人动平台自由度为三平移和一转动,同时,在并联机构动平台和虚拟固定平台间增加一辅助支链,该辅助支链具有独立的转动自由度。与具有同样运动特性的并联机构相比,该机器人的工作空间大,转动灵活。分析了该机器人的运动学特征,求出其位置正反解析解,利用运动影响系数对其速度和加速度进行了系统研究,并进行了动态仿真验证。     

履带式车辆斜坡转向稳定性研究

根据履带式车辆的运动特点,运用数力学中矢量分析理论和方法,推导了接地比压为线性分布时履带式车辆在斜坡上转向时,瞬时转向中心偏移量与车辆重心位置、转向半径、行进速度、加速度、车辆方位相互关系的计算公式。在此基础上,分析了瞬时转向中心偏移量的变化规律及影响因素,指出了导致转向不稳定的因素。     

Effects of Steel and Aluminum Shoes on Forelimb Kinematics in Stock-Type Horses as Measured at the Trot

To meet the needs of sport horses, horseshoes of various styles and materials have been implemented to enhance performance. Steel shoes are commonly used for their affordability and longevity; however, the use of aluminum horseshoes is being adopted to satisfy the various requirements of certain equestrian activities. Owing to the importance of the allure of movement in many aspects of competitive riding, the lightweight nature of aluminum horseshoes has been recognized to accentuate foreleg action. By performing a repeated-measures crossover study on nine healthy stock-type horses, the effects of these two horseshoe types on forelimb action were analyzed at the trot using two-dimensional kinematics. Horses were trotted in hand for three repetitions over a distance of 50.1 meters on days 4, 18, 32, and 46 postshoeing for two 6-week shoeing cycles. Video footage was collected and analyzed using gait analysis software (EquineTec) for each repetition. The measured stride length, fetlock extension, elbow and knee range of motion, and minimum and maximum elbow angle remained constant between treatments. However, there was a significant treatment effect on minimum carpal angle and maximum hoof height, with aluminum shoes having a larger minimum carpal angle than those in steel shoes (P < .05) and a lower maximum hoof height (P < .05). An overall 3-degree difference in minimum carpal angle and approximate 2.5-cm difference in maximum hoof height was observed between treatments. This finding is of particular importance to performance horse disciplines for which a lesser degree of knee action is desirable.     

Biomechanics in young and adult italian standardbred trotter horses in real racing conditions

This study was undertaken to characterize and establish the kinematic standards of Italian standardbred trotter horses in real racing conditions. Certain parameters, such as the angles of both front and hind fetlock joints, stride length, stride frequency and average speed in youngs and adults are presented, examinated and compared with statistical tests. The angles and stride length were obtained using ONTRACK software over frames extracted from two CANON MV630i digital videocameras. For the stride frequency, a third identical videocamera filmed the horses to count the number of beats per minute. The average speed was calculated by multiplying the stride frequency by the stride length and transforming the result into kilometers per hour. The data reveal that as speed increases, younger horses have more extended fetlock joints than adults. Contrary to this, at the maximum speed (hereafter referred to as sprint speed) the adults increase both their stride frequency and stride length, while young horses increase stride frequency and decrease stride length. We think that the knowledge of these parameters in competition breeds could have potential relevance as they may reveal early indicators of the development of proper and adequate characteristics in young horses of those breeds.     

The Effect of Training on the Jumping Parameters of Inexperienced Warmblood Horses in Free Jumping

Seven Warmblood horses without sport experience were trained and filmed four times during free jumping, with a 1-month interval between each investigation. Jumping parameters were measured on selected frames by means of video image analysis. Linear and angular parameters describing takeoff, landing, and lifting of limbs above the obstacle were studied. Statistical analysis revealed that the following parameters were affected by training: hind limbs distances at takeoff and landing, lifting of the limbs above the obstacle, and the angle of bascule.     

基于UG的双横臂独立悬架运动学分析系统

提出了一种基于UG构建双横臂独立悬架运动学分析系统的方法,并应用该方法开发出了相应的原型系统,给出了系统的框架结构.系统的快速参数化设计模块可方便、快捷地对双横臂悬架运动仿真模型的结构参数、几何参数和定位参数进行修改;系统的运动学仿真分析模块通过调用UG/Motion集成的MSC ADAMS或Function Bay RecurDyn解算器来获取仿真分析结果,通过集成Matlab的绘图功能对分析结果进行输出查看;以前轮定位参数的变化量最小、车轮侧向滑移量最小为优化目标,采用遗传算法构建了系统的悬架机构结构参数优化设计模块.通过一个设计实例验证了系统的正确性及基于遗传算法的结构参数优化设计模块的有效性.系统的框架结构具有良好的可扩展性,已在麦弗逊悬架的优化设计过程中得到应用.