Optimal load of robotic manipulator with joint elasticity using accuracy and actuator constraints

A computational technique for obtaining the maximum load-carrying capacity for a robotic manipulator with joint elasticity, subject to accuracy and actuator constraints, is described. Full load motions and increased productivity are linked in the industrial applications of many robotic manipulators; the maximum load carrying capacity which can be achieved by a manipulator during a given trajectory is limited by a number of factors. The dynamic properties of a manipulator, its actuator limitations, and joint elasticity (transmissions, reducers, and servo drive system) are probably the most important factors. This paper presents a strategy for determining dynamic load carrying capacity (DLCC), subject to both accuracy and actuator constraints, where a series of cubical bounds centred at the desired trajectory is used in the end-effector oscillation constraint while a typical d.c. motor speed-torque characteristics curve is used in the actuator constraint. The technique which considers the full nonlinear manipulator dynamics, actuator constraints, and accuracy constraints permits the manipulator user to specify the trajectory completely. Finally, a numerical example involving a two-link manipulator with joint flexibility using this method is presented and the results are discussed.     

Optimal load of elastic joint mobile manipulators imposing an overturning stability constraint

Full load motion of mobile manipulators while carrying a load with pre-defined motion precision is an important consideration in their application. Therefore, in this paper a general formulation for finding the maximum load-carrying capacity of compliant joint mobile manipulators is presented. The overturning stability of the system and the precision of the motion on the given end effector trajectory are taken into account. The main constraints used for the algorithm presented are the actuator torque capacity, the limited error bound for the end effector and the overturning stability during motion on the given trajectory. This paper presents a strategy for determining the dynamic load-carrying capacity (DLCC), subject to overturning stability, accuracy and actuator constraints, in which a series of ball-type bounds centred at the desired trajectory is used in the end effector oscillation constraint, while a typical d.c. motor speed-torque characteristics curve is used in the actuator constraint. The technique, which considers the full nonlinear mobile manipulator dynamics, actuator constraint, overturning stability constraint, and accuracy constraint, permits the user to specify the trajectory completely. In order to verify the effectiveness of the algorithm presented, a simulation study considering a compliant joint two-link planar manipulator mounted on a differentially driven mobile base is given with details.     

机器人协调操作刚性负载效率的研究

针对工业机器人的使用情况，考虑机器人臂的弹性变形，提出了以机器人关节输入功率最小作为规划目标，规划各协调机器人的承载比例和相对位置的方法。此方法可使系统效率最高并且其它动力特性较好。以具有冗余驱动的机器人协调操作系统为例，将所提目标的规划结果与通常即标的规划结果进行了比较，分析了影响系统效率和其它动力特性的因素。     

优化初始位形减轻具有柔性杆和关节的冗余度机器人振动变形

提出了利用最优初始位形以减轻具有柔性杆和关节的冗余度机器人变形振动的新方法。优化结果表明，在规划机器人的运动时，初始位形的优劣对柔性机器人的动力学性能有很大影响。     

Optimal load of elastic joint mobile manipulators imposing an overturning stability constraint

Full load motion of mobile manipulators while carrying a load with pre-defined motion precision is an important consideration in their application. Therefore, in this paper a general formulation for finding the maximum load-carrying capacity of compliant joint mobile manipulators is presented. The overturning stability of the system and the precision of the motion on the given end effector trajectory are taken into account. The main constraints used for the algorithm presented are the actuator torque capacity, the limited error bound for the end effector and the overturning stability during motion on the given trajectory. This paper presents a strategy for determining the dynamic load-carrying capacity (DLCC), subject to overturning stability, accuracy and actuator constraints, in which a series of ball-type bounds centred at the desired trajectory is used in the end effector oscillation constraint, while a typical d.c. motor speed-torque characteristics curve is used in the actuator constraint. The technique, which considers the full nonlinear mobile manipulator dynamics, actuator constraint, overturning stability constraint, and accuracy constraint, permits the user to specify the trajectory completely. In order to verify the effectiveness of the algorithm presented, a simulation study considering a compliant joint two-link planar manipulator mounted on a differentially driven mobile base is given with details.     

双柔性臂机器人的建模和主动振动控制

针对双柔性臂机器人在操作过程中出现的结构振动和残余振动影响控制精度的问题,提出了采用多组压电换能器对柔性臂进行主动振动的控制方法.设计了基于超声电机驱动的双柔性臂机器人,采用拉格朗日法和假设模态法对双柔性臂进行了动力学建模,并考虑了在协作搬运过程中双柔性臂机器人需要满足的闭链约束条件.提出了采用独立关节PD反馈控制器和正位置反馈控制器相结合的混合控制方法.Matlab仿真表明,所提出的混合控制器能使柔性机器人在准确完成目标物体轨迹运动的同时,实现对柔性臂的振动抑制,提高了双柔性臂机器人的搬运精度和效率.     

冗余度机器人研究动向

冗余度机器人，从运动学的观点来说是指完成某一特定任务时，机器人具有多余的自由度。多余的自由度可用来改善机器人的运动及动力学特性，如增加灵活性，躲避障碍、回避奇异、优化主运动任务下的辅助操作指标，优化关节速度，加速度，力矩，能量等。冗余度机器人由于其自身众多优点而越来越受到人们的关注。本文介绍冗余度刚性机器人、冗余度柔性机器人研究的发展现状及存在的问题。     

Optimal actuator sizing and end point deformation for mobile robotic manipulators with elastic joint based on load criteria

Application of a numerical method to determine the maximum dynamic load carrying capacity (DLCC) for a robotic manipulator carrying an automobile petrol tank with joint elasticity subject to accuracy and actuator constraints is described in this paper. The maximum DLCC which can be achieved by a manipulator during a given trajectory is limited by a number of factors. The most important of which are the dynamic specification of the manipulator, the actuator limitations, and the elasticity of the joints such as reducers and servo drive system. Initially, the kinematic equations for carrying the automobile petrol tank by the robotic arm with 6 degrees of freedom (DOF) were calculated. The mechanical modeling was achieved via software programming. Dynamic modeling of the flexible joints manipulator was done simply for the three major axes. A method for determination of the dynamic load capacity with specific reference to both accuracy and actuator constraints is explained. The results obtained indicate the importance of both constraints and which constraint is more critical for accuracy and tracking.     

Kinematics and dynamic modeling for holonomic constrained multiple robot systems through principle of workspace orthogonalization

This paper deals with an efficient mathematical modeling for multiple robot manipulators (or multifingered robot hands) holding and transporting a rigid common object on the constraint surfaces, subject to a set of holonomic (integrable) constraints. First, the kinematics and dynamics of the multiple robot systems are formulated. After a series of model transformations, a combined dynamic model is derived from a unified viewpoint. Then the system dynamics can be decomposed into two orthogonal subsystems the (reduced-order) motion subsystem and the force subsystem. From a practical point of view, the new dynamic model presented in this paper is suitable form for dynamic analysis and hybrid (position/force) control synthesis.     

多机械手协同的无内力抓取及动载的分配

讨论了多机械手协同系统的无内力抓取及相应的动载分配方法。对两个PUMA机械手协同操作同一物体的情况,进行了无内力分配原则下系统动载在关节空间的分配的数值分析。     

多机械手协同的无内力抓取及动载的分配

讨论了多机械手协同系统的无内力抓取及相应的动载分配方法。对两个ＰＵＭＡ机械手协同操作同一物体的情况,进行了无内力分配原则下系统动载在关节空间的分配的数值分析。     

Multibody modelling of N DOF robot arm assigned to milling manufacturing. Dynamic analysis and position errors evaluation

Nowadays, with the large use of robot manipulators in the most different fields of industrial production, two main aims must be commonly reached: robot dynamic behavior improvement and end-effector position errors reduction. For a N DOF robot arm, in case of specific applications such as milling manufacturing, one of the main source of end-effector position errors can be identified with joint compliances. This aspect, well known in literature, has been confirmed by experimental tests and measurements carried out on a specific robot assigned to non-standard milling manufacturing of marble objects (sculptures realization). To approach and analyze this issue the authors chose the multibody simulation environment. Hence, the authors developed a parametric modelling procedure that, by determining the robot characteristics through CAD model and technical data sheet investigation, provides reliable multibody dynamic models of generic N DOF robot arms. In this modelling approach the robot geometry construction is based on a standard strategy typical of this research field (i.e. Denavit-Hartenberg, Veitschegger-Wu). The developed procedure enables to obtain robot representation at various complexity levels according to the number of modelled robot components and actuation typology (Motion laws defined both in displacement or applied torque). Eventually, for a specific test case, the authors were able to correctly simulate the robot dynamic behavior, as it was demonstrated by numerical/experimental comparison. In this way the influence of the joint compliance behavior and actuator rotational inertia effects on end-effector position accuracy was analyzed.     

Dobot型机器人运动学分析与仿真

为了获得Dobot机器人的正逆解计算公式、避免解被丢失的可能性和保证角的精度,根据该型机器人的结构特点,运用D-H法建立了机器人的坐标系和运动学方程,进行了正逆运动学的分析,将双变量反正切函数应用到了逆解的表达式中。针对逆解多解和运动平稳性问题,对笛卡尔空间中利用直线插补和调用逆解公式求出的关节角序列进行了分析研究,提出了运用动态规划算法选出一组最优解序列,再利用三次B样条插值进行了连续化处理,并进行了实例验证和Matlab软件仿真。研究结果表明,利用该算法能够选出一组最优解和保证机器人运动的平稳性,为该型机器人的应用及轨迹规划与控制器的研究打下基础,所运用的算法和思想也适用于其他类型的多关节机器人。     

柔性机器人的协调操作及其逆动力学控制算法

柔性协调机器人系统是一个含柔性机器人内部各杆之间,运动协调约束条件和动力协调约束条件之间,柔性机器人与负载之间,以及柔性机器人之间高度耦合的复杂非线性系统,无论在动力学建模,还是控制算法方面都要比刚性协调机器人困难得多。通过对刚、柔性机器人协调操作系统本质特性的比较,利用有限元法和Lagrange方程建立了柔性协调机器人系统的动力学模型,并以系统逆动力学任务为目标,提出了通过校正机器人名义刚性运动来达到提高系统位姿控制精度的预测校正控制算法,成功给出了平面两3R柔性臂机器人协调操作刚性负载的仿真算例。     

用于驾驶机器人的车速跟踪多机械手协调控制方法

提出一种用于驾驶机器人的车速跟踪多机械手协调控制方法。建立了驾驶机器人车速跟踪多机械手/腿控制模型,在此基础上设计了驾驶机器人车速跟踪协调控制器,通过油门/离合器协调控制器实现了车辆的平稳起步和平顺换挡,通过发动机/制动器切换控制器实现了驾驶机器人对给定车速的准确跟踪。实车试验结果表明,提出的方法能合理地协调控制驾驶机器人的油门、制动、离合机械腿和换挡机械手,实现对目标车速的跟踪控制,驾驶机器人完全能够代替试验人员进行各种汽车试验。     

三维机器人工作空间及几何误差分析

机器人工作空间的分析和求解是机器人机构设计过程中一个非常重要的问题。本文采用基于随机概率的蒙特卡罗方法,根据关节空间到工作空间的映射关系,得到了机器人机构工作空间。因为常见的机器人属于三维空间机构,所以在以前工作的基础上,将概率方法推广到对三维机器人机构工作空间的求解上。通过深入地研究二维、三维图形的微分几何关系,在沿z方向得到每一层的边界曲线基础上,采用曲线包络的方法得到了三维工作空间曲面的形状。通过一个例子详细说明了该方法的具体使用。最后对三维工作空间进行了几何误差分析,并说明了该方法对工程实际问题的应用价值。     

基于样条函数法的机器人运动轨迹规划

利用样条函数法开发了一种机器人运动轨迹的规划方法，即各关节的运动采用样条函数来拟合。该法使用简便、计算量小，而且不会出现机构奇异点问题，可生成光滑平稳的无噪音机器人运动轨迹     

机器人末端操作器自动更换技术研究

介绍一种基于多传感器的机器人操作器自动更换装置，由于在机器人腕部安装了微调节器，机器人与环境接触时具有很好的柔顺性。在作业时具有很高的刚度；对接时采用了视觉引导粗定位、光学引导精确定位和姿态调整及主被动混合柔顺控制策略，使机器人操作器自动更换过程中都能满足对接正常进行的几何约束条件和力学约束条件；机器人操作器自动更换装置结构简单、感知能力和环境适应能力强、更换迅速、可靠，具有很强的数据传输能力，可用在除水下之外的大多数极限环境条件下。     

神经元调整比例因子模糊控制器控制直接驱动机器人单关节

基于文献「１」的神经元模型及学习策略，提出用神经元优化调整比例因子的模糊控制器设计方法方法，并针对直接驱动机器人单关节位置控制系统进行仿真实验。研究结果表明，非模型控制方法具有很强的鲁棒性，抗干扰性及满意的控制品质。     

Stable joint torque optimization for multiple cooperating redundant manipulator system

In this paper, joint torque optimization for multiple cooperating redundant manipulators rigidly handling a common object is considered. This work focuses on finding the optimal and stable distribution of the operational forces of a multiple redundant manipulator system to the individual manipulators. Two joint torque optimization schemes (local joint torque minimization and natural joint motion) are formulated and compared. When a redundant manipulator with its joints free is driven by its tip, a naturally inducing joint motion can be called ‘natural joint motion’. From the simulation results of a system of three cooperating redundant manipulators, the natural joint motion scheme is shown to be better than the local joint torque minimization scheme with regard to global torque minimization capability and the resulting stability of motion. However, in order to guarantee the stability, the null space damping method is required for the both schemes. The effectiveness of the null space damping method is demonstrated by simulation. Additionally, the condition for the distribution of the operational forces required to drive the given system along a natural joint motion trajectory is addressed.