计及环境特征的刚-柔机械臂动力学建模方法与理论研究

基于Kane方程推导建立了在惯性参考坐标系中的刚—柔机械臂的非线性动力学模型 ,并利用假设模态的方法对方程进行离散 .在对刚—柔机械臂进行主动柔顺控制时 ,柔性机械臂要受到未确知外部环境的约束 .本文建立了计及环境特征的一般柔性多体系统动力学模型以及计及环境特征的刚—柔机械臂动力学模型 .     

轮式移动机械臂的建模与仿真研究

移动机械臂系统一般由移动平台和机器臂组成,它既具有机器臂的操作灵活性,又具有移动机器人的可移动性,因此其应用范围要比单个系统宽得多。这篇文章主要研究了由非完整移动平台和完整机械臂组成的轮式移动机械臂系统的建模、跟踪控制及仿真问题。首先。利用拉格朗日动力学方程和非完整动力学罗兹方程建立了移动机械臂系统的精确数学模型;然后。利用非线性反馈将系统解耦。采用类PD控制器进行控制。在考虑了非完整约束及移动平台和机械臂的动态交互影响情况下,该控制算法保证系统同时跟踪给定的终端执行器和平台轨迹;最后,使用Maflah6．5对系统进行了仿真研究,仿真结果表明了其数学模型及控制方法的正确有效性。     

计及环境特征的刚一柔机械臂动力学建模方法与理论研究

基于Kane方程推导建立了在惯性参考坐标系中的刚一柔机械臂的非线性动力学模型，并利用假设模态的方法对方程进行离散．在对刚一柔机械臂进行主动柔顺控制时，柔性机械臂要受到未确知外部环境的约束．本文建立了计及环境特征的一般柔性多体系统动力学模型以及计及环境特征的刚一柔机械臂动力学模型．     

地面和空间机械臂的动力学等效条件与控制相似律

针对如何在地面机械臂上有效验证空间机械臂控制律的问题,本文研究空间机械臂和地面机械臂系统间的动力学等效条件和控制相似律.首先,基于量纲分析研究地面机械臂和空间机械臂之间的动力学等效条件,并基于等效条件设计地面机械臂系统.其次,基于量纲分析建立空间和地面机械臂系统间的控制相似律,设计的空间机械臂控制律通过控制相似律将可以转化为地面机械臂相应的控制律.最后,考虑地面机械臂基座往往无法和空间机械臂的基座航天器一样进行全6自由度运动,以及地面机械臂运动时受到重力影响,使得地面机械臂不再满足动力学等效条件,基于反馈线性化技术设计一种地面机械臂的动力学误差补偿策略,使得地面机械臂和空间机械臂具有相似的闭环动力学行为.这样,空间机械臂的控制律可以在设计的地面机械臂上进行验证,仿真中以在地面机械臂上验证空间机械臂的PID控制器为例说明所提方法的有效性.     

三连杆移动机械臂模型与运动规划

采用拉格朗日动力学方法和非完整动力学罗兹方程建立了三连杆移动机器臂运动学和动力学模型,并且利用该模型采用了人工势函数方法来驱动移动机械臂系统绕过障碍物到达目标位置.仿真的结果证明了该模型的正确性及其规划方法是有效的.     

一种基于指数积的移动机械臂联合标定方法

提出一种基于指数积的移动机械臂联合标定方法,以实现移动平台和机械臂两者间位姿标定与机械臂运动学参数标定模型的统一.机械臂运动学参数标定使用最多的是基于D-H参数法,但D-H参数法无法克服相邻关节平行或接近平行时的奇异性问题,以及建模过程复杂、建模后的模型通用性差等问题.基于指数积的移动机械臂联合标定方法建模时不会因为关节轴平行而出现奇异性问题,建模过程简单.通过对整个系统的运动学方程进行微分运算,获得末端位姿误差和移动机械臂零位状态旋量误差及关节旋量误差的线性化模型.利用伴随矩阵方式建立关节旋量理论值与关节旋量实际值的关系,并通过改变伴随矩阵实现基于最小二乘法的参数辨识计算过程中参数更新.使用高精度激光跟踪仪作为测量工具,通过实验验证所提出方法的有效性.     

基于非回归矩阵的移动机械臂的自适应控制

针对非完整移动机械臂系统的输出跟踪问题,在系统的惯性参数及未建模动态未知的情况下,根据动力学方程的性质,为其设计了基于非回归矩阵的自适应控制律。将其用于一类非完整移动机械臂的输出跟踪控制,仿真结果验证了所提出控制方法的正确有效性。     

基于一阶不确定项估计律的机械臂鲁棒控制研究

针对多自由度机械臂控制系统的模型参数误差、关节摩擦力以及外部输入扰动等不确定项,设计了一类一阶误差估计律;结合基于机构动力学名义模型的输入输出反馈线性化控制算法,对六自由度刚性机械臂的时变轨迹跟踪控制进行了研究,理论上证明了设计的鲁棒控制器是全局渐进稳定的.仿真结果表明该控制策略对系统的各类不确定项具有很好的鲁棒性,能够实现高精度的轨迹跟踪控制.     

机械臂负载移动性能与运动调控研究

工业的不断发展对机械臂的负载要求越来越高,而负载的增加会对机械臂末端的精度造成影响.本文以Franka七轴串联机械臂为对象,采用M-DH法和雅可比迭代法对其正、逆运动学展开分析;采用三次函数插值法进行关节空间的轨迹规划.基于拉格朗日方程建立了机械臂的动力学模型,并通过Admas和Simulink联合动力学仿真验证了动力学模型的有效性.最后基于定位控制,对末端位置误差收敛速率、负载质量、控制参数之间的关系展开研究.     

机器人机械臂的鲁棒最优控制

基于拉格朗日方程,把多关节机器人机械臂动力学模型转化成一线性状态方程。然后,针对此线性状态方程,通过解一线性二次型优化问题,得到鲁棒最优控制律,保证了关节变量全局渐近收敛。最后,以两关节机器人为例,仿真结果表明所设计的控制律的有效性和鲁棒性。     

Adaptive control of free-floating space manipulators using dynamically equivalent manipulator model

In this paper, adaptive control of free-floating space manipulators is considered. The dynamics based on the momentum conservation law for the free-floating space manipulator has non-linear parameterization properties. Therefore, the adaptive control based on a linear parameterization model cannot be used in this dynamics. In this paper, the dynamics of the free-floating space manipulator system are derived using the Dynamically Equivalent Model (DEM) approach. The DEM is a fixed-base manipulator system and allows us to linearly parameterize the dynamic equations. Using this linearly parameterized dynamic equation, an adaptive control method is developed to control the system in joint space. Parameter identification and torque calculations are done using the DEM dynamics. Simulations show that the tracking errors of the manipulator joints to a given desired trajectory become zero when the calculated torques act on the joints of the space manipulator system.     

Dynamics analysis of a 3-RRP spherical parallel manipulator using the natural orthogonal complement

In the present research, application of the Natural Orthogonal Complement (NOC) for the dynamic analysis of a spherical parallel manipulator, referred to as SST, is presented. Both inverse and direct dynamics are considered. The NOC and the SST fully parallel robot are explained. To drive the NOC for the SST manipulator, constraints between joint variables are written using the transformation matrices obtained from three different branches of the robot. The Newton–Euler formulation is used to model the dynamics of each individual body, including moving platform and legs of the manipulator. D’Alembert’s principle is applied and Newton–Euler dynamical equations free from non-working generalized constraint forces are obtained. Finally two examples, one for direct and one for inverse dynamics are presented. The correctness and accuracy of the obtained solution are verified by comparing with the solution of the virtual work method as well as commercial multi-body dynamics software.     

Symbolic modeling and dynamic simulation of robotic manipulators with compliant links and joints

The explicit, non-recursive symbolic form of the dynamic model of robotic manipulators with compliant links and joints are developed based on a Lagrangian-assumed mode of formulation. This form of dynamic model is suitable for controller synthesis, as well as accurate simulations of robotic applications. The final form of the equations is organized in a form similar to rigid manipulator equations. This allows one to identify the differences between rigid and flexible manipulator dynamics explixitly. Therefore, current knowledge on control of rigid manipulators is likely to be utilized in a maximum way in developing new control algorithms for flexible manipulators.

Computer automated symbolic expansion of the dynamic model equations for any desired manipulator is accomplished with programs written based on commercial symbolic manipulation programs (SMP, MACSYMA, REDUCE). A two-link manipulator is used as an example. Computational complexity involved in real-time control, using the explicit, non-recursive form of equations, is studied on single CPU and multi-CPU parallel computation processors.     

Torque Optimizing Control with Singularity-Robustness for Kinematically Redundant Robots

A new control method for kinematically redundant manipulators having the properties of torque-optimality and singularity-robustness is developed. A dynamic control equation, an equation of joint torques that should be satisfied to get the desired dynamic behavior of the end-effector, is formulated using the feedback linearization theory. The optimal control law is determined by locally optimizing an appropriate norm of joint torques using the weighted generalized inverses of the manipulator Jacobian-inertia product. In addition, the optimal control law is augmented with fictitious joint damping forces to stabilize the uncontrolled dynamics acting in the null-space of the Jacobian-inertia product. This paper also presents a new method for the robust handling of robot kinematic singularities in the context of joint torque optimization. Control of the end-effector motions in the neighborhood of a singular configuration is based on the use of the damped least-squares inverse of the Jacobian-inertia product. A damping factor as a function of the generalized dynamic manipulability measure is introduced to reduce the end-effector acceleration error caused by the damping. The proposed control method is applied to the numerical model of SNU-ERC 3-DOF planar direct-drive manipulator.     

Constrained motion control of flexible robot manipulators based on recurrent neural networks

In this paper, a neural network approach is presented for the motion control of constrained flexible manipulators, where both the contact force everted by the flexible manipulator and the position of the end-effector contacting with a surface are controlled. The dynamic equations for vibration of flexible link and constrained force are derived. The developed control, scheme can adaptively estimate the underlying dynamics of the manipulator using recurrent neural networks (RNNs). Based on the error dynamics of a feedback controller, a learning rule for updating the connection weights of the adaptive RNN model is obtained. Local stability properties of the control system are discussed. Simulation results are elaborated on for both position and force trajectory tracking tasks in the presence of varying parameters and unknown dynamics, which show that the designed controller performs remarkably well.     

Dynamics and Cooperative Object Manipulation Control of Suspended Mobile Manipulators

Dynamics and control of mobile manipulators is obviously a more challenging problem compared to fixed-base robots. Including a suspension system for these mobile platforms increases their maneuverability, but considerably adds to their complexity. In this paper, a suspended wheeled mobile platform with two 6-DOF Puma-type manipulators is used to manipulate an object along a given path. To apply a model-based control algorithm, it is required to have an explicit dynamics model for such highly nonlinear system. This model should be as concise as possible to include fewer mathematical calculations for online computations. Therefore in this paper, a detailed set of dynamics equations for a multiple arm wheeled mobile platform equipped with an effective suspension system is presented. The method is based on the concept of Direct Path Method (DPM), which is extended here for such challenging type of robots. The obtained dynamics model is then verified with a dynamical analysis study using software ADAMS. Then, Natural Orthogonal Complement Method is used to include the non-holonomic constraint of the wheeled platform in a more concise dynamics model. Next, an impedance control law is applied for cooperative manipulation of an object by the two manipulators. The obtained results for a suspended wheeled platform equipped with two 6-DOF Puma-type manipulators reveal a successful performance for moving an object along a mixed circular-straight path, even in the presence of unexpected disturbing forces, system/end-effector flexibility and impacts due to contact with an obstacle.     

柔性臂漂浮基空间机器人建模与轨迹跟踪控制

利用拉格朗日法和假设模态方法建立了末端柔性的两臂漂浮基空间机器人的非线性动力学方程．通过坐标变换,推导出一种新的以可测关节角为变量的全局动态模型,并在此基础上运用基于模型的非线性解耦反馈控制方法得到关节相对转角与柔性臂的弹性变形部分解耦形式控制方程．最后,讨论了柔性臂漂浮基空间机器人的轨迹跟踪问题,并通过仿真实例计算,表明该模型转换及控制方法对于柔性臂漂浮基空间机器人末端轨迹跟踪控制的有效性．     

一种双连杆柔性臂动力学模型的研究

针对末端位置受约束的双连杆柔性机械臂,通过哈密顿原理得到系统的分布参数模型,推导了描述关节角,柔性杆振动和接触力之间关系的动力学模型.根据3个假设条件推导柔性臂简化的集中参数动力学模型及准静态方程,利用了计算力矩法设计的控制器对模型进行控制,通过Matlab进行仿真,利用Matlab的符号运算功能,编制M文件实现数学模型自动推导,整个建模和运算过程简单、直观和高效,并绘制了参数轨迹图像,验证了模型的有效性,已应用到小波神经网络控制算法研究中.