Inverse Dynamics of Delta Robot Based on the Principle of Virtual Work

A systematic methodology for solving the inverse dynamics of the Delta robot is presented.First,the inverse kinematics is solved based on the vector method.A new form of the Jacobi matrix formulized by the vectors is obtained so the three types kinematics singularities namely inverse, direct and combined types, can be identified with the physical meaning.Then based on the principle of virtual work, a methodology for driving the dynamical equations of motion is developed.Meanwhile the whole actuating torques, the torques caused by the gravity, the velocity and the acceleration are computed respectively in the numerical example. Results show that torque caused by the acceleration term is much bigger than the other two terms.This approach leads to efficient algorithms since the constraint forces and moments of the robot system have been eliminated from the equations of motion and there is no differential equation for the whole procedure when the principle of virtual work is applied to solving the inverse dynamical problem.

Unified Modeling Approach of Kinematics, Dynamics and Control of a Free-Flying Space Robot Interacting with a Target Satellite

In this paper a unified control-oriented modeling approach is proposed to deal with the kinematics, linear and angular momentum, contact constraints and dynamics of a free-flying space robot interacting with a target satellite. This developed approach combines the dynamics of both systems in one structure along with holonomic and nonholonomic constraints in a single framework. Furthermore, this modeling allows consid-ering the generalized contact forces between the space robot end-effecter and the target satellite as internal forces rather than external forces. As a result of this approach, linear and angular momentum will form holonomic and nonholonomic constraints, respectively. Meanwhile, restricting the motion of the space robot end-effector on the surface of the target satellite will impose geometric constraints. The proposed momentum of the combined system under consideration is a generalization of the momentum model of a free-flying space robot. Based on this unified model, three reduced models are developed. The first reduced dynamics can be considered as a generalization of a free-flying robot without contact with a target satellite. In this re-duced model it is found that the Jacobian and inertia matrices can be considered as an extension of those of a free-flying space robot. Since control of the base attitude rather than its translation is preferred in certain cases, a second reduced model is obtained by eliminating the base linear motion dynamics. For the purpose of the controller development, a third reduced-order dynamical model is then obtained by finding a common solution of all constraints using the concept of orthogonal projection matrices. The objective of this approach is to design a controller to track motion trajectory while regulating the force interaction between the space robot and the target satellite. Many space missions can benefit from such a modeling system, for example, autonomous docking of satellites, rescuing satellites, and satellite servicing, where it is vital to limit the con-tact force during the robotic operation. Moreover, Inverse dynamics and adaptive inverse dynamics control-lers are designed to achieve the control objectives. Both controllers are found to be effective to meet the specifications and to overcome the un-actuation of the target satellite. Finally, simulation is demonstrated by to verify the analytical results.

基于MATLAB和RobotStudio的6-DOF机器人运动学分析与仿真

针对船体密封舱、箱柜等狭窄空间普遍存在的机器人难以工作问题,提出了一种新型6-DOF(degrees of freedom)机器人。首先分析了该机器人的机械结构,基于D-H坐标理论建立了机器人D-H坐标表格以及机器人正、逆运动学方程,其次应用MATLAB对机器人的运动学进行了仿真,结果表明所得的机器人正、逆运动学方程完全正确;最后设计了虚拟样机,利用RobotStudio仿真分析了机器人箱体焊接的优点;为进一步验证设计的机器人运动性能,与通用6-DOF机器人做了对比分析。研究结果表明新型机器人运动的可行性,为设计适应箱柜等狭窄空间的工业机器人提供了理论依据。

Algebraic Method‑Based Point‑to‑Point Trajectory Planning of an Under‑Constrained Cable‑Suspended Parallel Robot with Variable Angle and Height Cable Mast

To avoid impacts and vibrations during the processes of acceleration and deceleration while possessing flexible working ways for cable-suspended parallel robots(CSPRs),point-to-point trajectory planning demands an under-constrained cable-suspended parallel robot(UCPR)with variable angle and height cable mast as described in this paper.The end-effector of the UCPR with three cables can achieve three translational degrees of freedom(DOFs).The inverse kinematic and dynamic modeling of the UCPR considering the angle and height of cable mast are completed.The motion trajectory of the end-effector comprising six segments is given.The connection points of the trajectory segments(except for point P3 in the X direction)are devised to have zero instantaneous velocities,which ensure that the acceleration has continuity and the planned acceleration curve achieves smooth transition.The trajectory is respectively planned using three algebraic methods,including fifth degree polynomial,cycloid trajectory,and double-S velocity curve.The results indicate that the trajectory planned by fifth degree polynomial method is much closer to the given trajectory of the end-effector.Numerical simulation and experiments are accomplished for the given trajectory based on fifth degree polynomial planning.At the points where the velocity suddenly changes,the length and tension variation curves of the planned and unplanned three cables are compared and analyzed.The OptiTrack motion capture system is adopted to track the end-effector of the UCPR during the experiment.The effectiveness and feasibility of fifth degree polynomial planning are validated.

Dynamic analysis, simulation, and control of a 6-DOF IRB-120 robot manipulator using sliding mode control and boundary layer method

Because of its ease of implementation,a linear PID controller is generally used to control robotic manipulators.Linear controllers cannot effectively cope with uncertainties and variations in the parameters;therefore,nonlinear controllers with robust performance which can cope with these are recommended.The sliding mode control(SMC)is a robust state feedback control method for nonlinear systems that,in addition having a simple design,efficiently overcomes uncertainties and disturbances in the system.It also has a very fast transient response that is desirable when controlling robotic manipulators.The most critical drawback to SMC is chattering in the control input signal.To solve this problem,in this study,SMC is used with a boundary layer(SMCBL)to eliminate the chattering and improve the performance of the system.The proposed SMCBL was compared with inverse dynamic control(IDC),a conventional nonlinear control method.The kinematic and dynamic equations of the IRB-120 robot manipulator were initially extracted completely and accurately,and then the control of the robot manipulator using SMC was evaluated.For validation,the proposed control method was implemented on a 6-DOF IRB-120 robot manipulator in the presence of uncertainties.The results were simulated,tested,and compared in the MATLAB/Simulink environment.To further validate our work,the results were tested and confirmed experimentally on an actual IRB-120 robot manipulator.

面向学科竞赛的发球机器人设计与控制

以发球机器人的设计和控制为案例,涵盖机械结构设计、电子电路设计、单片机控制、机器视觉、运动学建模和控制调试等多个领域的知识综合。该机器人的机械结构主要包括捡球机构、传球机构、发球机构和底盘机构。底盘机构为机器人的移动提供动力,捡球机构用于捡取放置的待发球,结合视觉定位单元可实现待发球的准确定位和自动抓取,传球机构负责将待发传送到发球机构,由发球机构将待发球发射到目标区域。电气控制系统的主控芯片为STM32单片机,实现对各执行机构的协调控制。经制作样机测试,该发球机器人的发球方向和速度可控。

刚柔耦合串并联康复机械臂运动特性分析

针对目前大多数上肢康复机器人在结构上存在的不足,首先,设计了一种兼具绳索驱动和并联机构优点的4自由度刚柔耦合串并联康复机械臂。其次,在基于此康复机械臂绳索空间和关节空间映射关系的条件下,运用D⁃H坐标法建立了康复机械臂的运动学模型。最后,在Matlab环境下,仿真分析了各关节角与绳长、速度随时间变化的关系曲线。分析结果表明,该刚柔耦合串并联康复机械臂结构设计的合理性,也为分析康复机械臂的轨迹规划问题提供理论基础。

2DOF空间3-RPS并联机器人位置运动学混合算法

空间2自由度并联机构可用于高作用力下精确控制姿态的两个分量的工作场合.建立了2自由度3-RPS并联机器人的位置运动学约束方程;对其正逆运动学算法进行了讨论.对求解并联机器人位置正解的杆长搜索法进行了改进,并结合解非线性方程组的拟牛顿法,提出了一种能解决方程组多解并且计算精度较高的混合算法,推导了2自由度3-RPS并联机器人位置反解的求解过程.通过实例验证了算法的正确性和所能达到的精度.

油茶果动态抓取Delta机器人正运动学特性研究

针对传统D-H参数法求解机械臂运动学时过程比较复杂的问题,为满足油茶果动态抓取的要求,提出了一种基于旋量理论构建3-R(SS)2Delta机器人正运动学方程的方法。针对3-R(SS)2Delta机器人的结构进行分析;通过旋量理论的指数积公式对该机器人的正运动学特性进行研究,获得机器人的位姿变换矩阵;最后,通过搭建的Delta机器人试验平台运行标准门型轨迹,结果表明:Delta机器人末端执行器能够精准地对传送带上移动的油茶果进行抓取。对比分析正运动学方程的计算值和Delta机器人试验平台试验测量值,得到末端执行器位置值的位置误差为±0.3mm,验证了所提出方法对构建油茶果动态抓取Delta机器人正运动学方程的正确性及可行性,旨在为后续进行油茶果动态抓取的轨迹规划研究奠定基础。

基于多自由度机械臂的乒乓球平衡控制算法研究

以板球系统模型为基础,提出了使用多自由度串联机械臂控制乒乓球平衡的方法。首先,从板球控制系统出发,分析这类平衡算法的优缺点;其次,对六自由度串联机械臂进行运动学分析;最后,通过Matlab软件和Webots软件对机械臂进行仿真试验,验证其准确性。仿真结果表明:在一般的应用场景下,使用多自由度串联机械臂控制乒乓球平衡的方法具有一定的通用性。

3-DOF混联机构的动力学建模与仿真分析

提出一种新型三自由度混联机构,运用螺旋理论分析了该机构的机构学原理,计算了机构自由度。以多刚体系统动力学理论为基础,建立了该并联机构的多体系统动力学模型,在此基础上开展了该机构正向运动学、逆向运动学及动力学的仿真研究。结果表明:在所设计的的构型及尺度下,机构存在非线性的输入输出关系;在Z轴方向一定的情形下,X方向最大运行角度为-15°,Y方向最大运行角度为-17°;从机构的加速度及速度运动曲线来看,机构不存在明显的刚性冲击。

6RSS仿人并联咀嚼机器人的刚性动力学建模分析

目的:对设计的6RSS仿人并联咀嚼机器人进行刚性动力学建模分析。方法:首先,推导刚性动力学建模所需的运动变量(包括平动/转动速度和加速度)函数。其次,使用牛顿-欧拉法则建立机器人的刚性动力学模型。最后,在机器人受到咀嚼反力情况下,跟踪口腔健康志愿者的咀嚼运动轨迹,并开展数值计算。结果:数值计算结果表明,机器人的驱动力矩和约束力出现峰值的时刻和咀嚼反力出现峰值的时刻一致。结论:外力对机器人的逆动力学有较大影响,该研究为机器人的运动控制以及优化设计提供了理论依据。

三自由度欠约束柔索驱动并联机器人的轨迹规划

柔索驱动并联机器人是一种特殊的并联机器人,属于柔性机器人的一类,它的末端执行器是由柔索代替刚性杆驱动实现其位姿的变化。研究了一种三自由度欠约束柔索驱动并联机器人,其索杆可以沿着圆形导轨旋转,即索杆夹角是可变的,实现机器人构型的可重构,减少柔索与柔索以及柔索与障碍物发生碰撞的概率。采用矢量闭环原理建立该机器人的逆运动学方程;根据拉格朗日公式建立该机器人的动力学方程;给定机器人末端执行器的运动轨迹,采用五次多项式进行规划,得出规划前后X、Y和Z方向的位移、速度和加速度曲线,在速度突变的点处,规划后的速度和加速度曲线实现光滑过渡,避免机器人在运动过程中发生振动和冲击,使得机器人末端执行器的运动轨迹平滑;三根柔索长度和拉力的实验曲线与规划后的期望曲线基本吻合,相机追踪轨迹与五次多项式规划后的运动轨迹基本一致;数值仿真和实验结果验证了三自由度欠约束柔索驱动并联机器人的逆运动学和动力学分析的正确性,以及五次多项式规划的有效性。

Trajectory Tracking of Quadrotor Aerial Robot Using Improved Dynamic Inversion Method

This paper presents trajectory tracking control works concerning quadrotor aerial robot with rigid cross structure. The quadrotor consists of four propellers which are two paired clockwise rotate and anticlockwise rotate. A nonlinear dynamic model of the quadrotor is provided, and a controller based on the improved dynamic inverse is synthesized for the purpose of stabilization and trajectory tracking. The proposed control strategy has been tested in simulation that can balance the deviation of model inaccuracy well.

Design considerations of high precision 6-HTRT parallel manipulator

Describes a new architecture of a parallel robot with six degrees of freedom and focuses on improving orientation accuracy of movable platform in mechanism, error correction and control methods. A set of formulations about inverse kinematics, Jacobin matrix, and forward kinematics for the high precision 6-HTRT parallel robots is presented. The analysis of errors existing in the manipulator is discussed and a novel approach for error correction is advanced. By DSP technique, inverse kinematics is solved in real time conditions with high precision and the hardware control system is given. The experimental results demonstrate the effectiveness of the proposed technique.

Disturbance rejection control based on acceleration projection method for walking robots

This paper presents a disturbance rejection scheme for walking robots under unknown external forces and moments. The disturbance rejection strategy, which combines the inverse dynamics control with the acceleration projection onto the ZMP (zero moment point)-plane, can ensure the overall dynamic stability of the robot during tracking the pre-computed trajectories. Under normal conditions, i.e., the system is dynamically balanced, a primary inverse dynamics control is utilized. In the case that the system becomes unbalanced due to external disturbances, the acceleration projection control (APC) loop, will be activated to keep the dynamic stability of the walking robot through modifying the input torques. The preliminary experimental results on a robot leg demonstrate that the proposed method can actually make the robot keep a stable motion under unknown external perturbations.

Exact Computation of Parallel Robot's Generalized Inertia Matrix

According to the definition of the new hypothetical states which have obvious physical significance and are termed as no-gravity static and accelerated states, a method for exact computation of the parallel robot＇s generalized inertia matrix is presented. Based on the matrix theory, the generalized inertia matrix of the parallel robot can be computed on the assumption that the robot is in these new hypothetical states respectively. The approach is demonstrated by the Delta robot as an example. Based on the principle of the virtual work, the inverse dynamics model of the robot is formulized after the kinematics analysis. Finally, a numerical example is given and the element distribution of the Delta robot＇s inertia matrix in the workspace is studied. The method has computationa＇, advantage of numerical accuracy for the Delta robot and can be parallelized easily.

双工位模块化磨削机器人运动学及动力学仿真

基于机器人运动学和动力学的相关知识,设计了一种双工位的模块化磨削机器人系统。首先构建系统机器人实体模型,根据D-H方法创建机器人关节连杆坐标系,并求解机器人的正逆运动学结果。然后,通过求解结果和轨迹规划设计,对机器人进行运动学仿真模拟,以获得每个关节的运动关系曲线。随后对机器人模型进行动力学仿真模拟,得到每个关节的力矩曲线。模拟结果显示:机器人每个关节的运动和力矩连续,双工位模块化磨削机器人系统在工作时能够保持较高的精度,并且仿真值的相对误差在5%以内,表明模拟结果具有较高的可靠性,文中研究为磨削机器人系统设计提供一定的指导。

3-PRPS/RRR踝关节康复机器人运动机理研究与试验

为设计一种结构合理、适宜患者使用的踝关节康复机构,针对踝关节运动特点,提出一种3-PRPS/RRR并联机器人。采用旋量理论描述机器人的数学模型,推导得出该机器人具有3转动自由度;使用闭环矢量法得到机器人的位置逆解方程,利用粒子群优化算法计算机器人的位置正解;设定一组机器人的设计参数,建立由初值不断迭代的数值算法得到机器人的工作空间;推导机器人的雅克比矩阵,计算机器人在其工作空间内的奇异位形;通过生物力学软件建立人体骨肌系统,仿真得到使用该机器人进行踝关节康复训练时踝关节处肌肉的激活程度;搭建试验样机进行试验,验证机器人位置正/逆解、工作空间和奇异位形。研究结果表明:CAD模型和理论计算结果一致,结合试验验证了机器人位置正/逆解的正确性;试验样机的工作空间能够满足踝关节康复训练所需的运动范围,且机器人在其工作空间内不存在奇异位形;使用该机器人进行康复训练时能够有效地激活肌肉,达到康复训练的目的。

索杆高度可变的3自由度欠约束并联机器人的力学分析

柔索驱动并联机器人是并联机构中的一种特殊柔性机构,通过使用柔索代替刚性杆驱动末端执行器,其综合了柔性机器人和并联机器人两方面的优点。研究了一种索杆高度可变的3自由度欠约束并联机器人,根据矢量闭环原理,建立该机器人的逆运动学模型;根据柔索的长度,推导该机器人的正运动学模型;采用拉格朗日公式,建立该机器人的动力学模型;利用Monte-Carlo方法,研究该机器人的静力学工作空间;给定末端执行器的运动轨迹,通过机器人的逆运动学模型得出3根柔索的期望长度,以3根柔索的期望长度作为实验输入,得到3根柔索的实验长度曲线和拉力曲线以及机器人的正运动学轨迹。实验结果验证了该机器人的正逆运动学和动力学模型的正确性以及工作空间的有效性。