Self-tuning control of a robot manipulator arm

The paper describes self-tuning control as applied to a purpose-built experimental five-axis manipulator arm. The dynamic equations of the three principle axes are linearized and used as a design basis for pole-assignment self-tuning adaptive controllers

Two applications are presented. In the first application the manipulator arm is controlled using a SISO pole-assignment self-tuner, while in the second, a multivariable pole-assignment self-tuning controller is applied. A discussion of the practical issues affecting these two application is presented in the concluding section.     

A vertically intersected dual-axis modularized reconfigurable actuator: design and application for a six-axis humanoid robot arm

A vertically intersected dual-axis modularized actuator system (DAMA) is developed and applied to a six-axis humanoid robot arm in this article. The DAMA consists of a two independent joint system, and the system structure is further refined using finite element analysis. It will be shown that the novel DAMA modular system can be used to easily construct a mechanism with any degrees of freedom. In other words, a modular or reconfigurable system can be achieved using the DAMA module. Based on simulations with ADAMS and MATLAB software packages, the system dynamic properties can be observed. In addition, the hardware and software systems of the DAMA are developed. The hardware architecture is composed of a microprocessor, an RS-232 to CAN bus module, and two independent-joint controller modules. The software control system is written in Visual C++. The system employs a simple but effective PID scheme to independently control the DAMA's two joints. The experimental results show that for an S-curve and circle trajectory input position command, the DAMA and the six-axis humanoid robot arm, which is formed by the DAMA module, can track the command well. Hence, the DAMA can be used as a generic module for multiple-degree-of-freedom systems.     

基于组合非线性反馈技术的机器人控制方法

为解决机器人跟踪控制中响应速度和超调量之间的矛盾,实现快速的响应和较小的超调,研究了机器人非线性动力学与组合非线性反馈技术相结合的控制策略,提出了一种基于组合非线性反馈的机器人控制器.该控制器由两部分组成,一部分由完全的机器人非线性动力学补偿来实现反馈线性化,另一部分由组合非线性反馈技术实现镇定.通过反馈线性化技术与Lyapunov理论,证明了闭环系统的渐近稳定性.同时,把组合非线性反馈理论拓展到多输入多输出(MIMO)饱和线性系统的时变轨迹跟踪控制,利用非线性项的变阻尼特性,使得系统的动态响应快速且没有超调.仿真结果证实了此方法的有效性.     

关节臂式坐标测量系统关键技术研究

关节臂式坐标测量机是一种新型的多自由度非笛卡尔式坐标测量系统.介绍了该系统硬件系统和软件系统的基本构成、主要特点及实现方法.基于DH参数法建立了误差参数模型,提出了一种将并行机制的模拟退火算法和两次最优保存策略的遗传算法相结合的参数标定方法,同时利用改进的多点交叉算子和自适应变异算子加快了标定过程.本标定算法在Faro Platinum 2.4 m关节臂式坐标测量机上进行了实验验证,证明了标定算法精确性.     

Development of the anthropomorphic robot with carbon fiber epoxy composite materials

The material for the robot structure should have high specific stiffness (stiffness/density) to give positional accuracy and fast maneuverability to the robot. Also, the high material damping is beneficial because it can dissipate the structural vibration induced in the robot structure. This cannot be achieved through conventional materials such as steel and aluminum because these two materials have almost the same specific stiffnesses which are not high enough for the robot structure. Moreover, steel and aluminum have low material dampings.

Composites which usually consist of very high specific modulus fibers and high damping matrices have both high specific stiffnesses and high material dampings. Therefore, in this work, the forearm of an anthropomorphic robot which has 6 degrees of freedom, 70 N payload and 0·1 mm positional accuracy of the end effector was designed and manufactured with high modulus carbon fiber epoxy composite because the magnitudes of the mass and moment of inertia of the forearm of an anthropomorphic robot are most important due to its farthest position from the robot base.

Two power transmission shafts which deliver the power of the motors positioned at the rear of the robot forearm to the wrist and the end effector were also designed and manufactured with high modulus carbon fiber epoxy composite to reduce weight and rotational inertia. The mass reduction of the manufactured composite forearm was 15·9 kg less than the steel forearm.

The natural frequencies and damping capacity of the manufactured composite arm were measured by the fast Fourier transform method and compared to those for the steel arm. From the test, it was found that both the fundamental natural frequency and damping ratio of the composite arm of the robot were much higher than those of the steel arm.     

Control and stabilization of a flexible robot arm

It is shown that a flexible robot arm performing a slewing manoeuvre can be controlled exactly within finite energy states by applying moments at the rotating cylinder the beam is attached to, and shearing forces at the free end of the structure. Furthermore, the use of implementable mechanical damping devices, applied to the base and to the free end of the robot arm, shows that uniform exponential stability holds. A Liapunov function is constructed     

基于等效并联机构的四足步行机器人运动分析

针对四足步行机器人机构运动学求解问题进行了研究.以螺旋理论为分析手段,提出一种基于等效并联机构的步行机器人运动分析方法.将四足机器人3足落地和4足落地状态的运动状态等效为3-UPS和4-UPS并联机构,进行了步行机器人3足、4足落地时的等效并联机构自由度分析,证明其自由度设计的正确性.对单腿机构的运动空间进行了分析和计算,通过比较研究,选取其中运动空间合理的单腿机构配置方式.最后,通过对对应等效并联机构的运动学分析,解决了不同运动状态下的四足步行机器人机构的运动学求解问题.     

Experimental analysis of a composite automotive suspension arm

In applications where weight saving and parts integration can be achieved, the Rover Group has been investigating the design and manufacture of components from composite materials. The methods used in the different steps in the design-to-manufacture cycle in the high volume automotive industry are relatively well known for a steel component, but are not so well established for a composite component. A design methodology for composites has been emerging in which a principal procedure is design analysis. One of the most established methods of analysis is that using the finite element technique, and this is being supplemented with experimental tests on prototypes using photoelastic analysis and stress pattern analysis by thermal emission, coupled with conventional strain gauge monitoring. Little work has been undertaken to correlate the results obtained from these different test methods and to compare the results with measurements made on an actual component. This paper presents some of the work undertaken concerning the analysis and testing of a composite automotive suspension arm. The results obtained from the three different analysis techniques are compared with experimental test results, and their accuracy is discussed.     

网络远程控制中机械臂的连续轨迹控制

探讨了点位控制在二自由度机械臂网络远程控制中的问题,将连续轨迹控制应用到基于关节坐标空间的机器人控制系统中,分析了在远程操控环境中实现连续轨迹控制所需要满足的条件,给出了最佳合成速度的求法,并进行了实际系统的远程控制实验,在期望时间内实现了连续、平滑的运动效果,证实了在网络远程系统的控制中采用连续轨迹控制能够获得更高的精度。     

多臂机提综臂辅助旋铆并联机器人优化设计

提综臂是多臂机上实现凸轮开口运动的关键核心部件.为满足多臂机提综臂的自动化加工需求,设计了一种新型辅助旋铆并联机器人,以实现在提综臂旋铆加工过程中对零部件的高速、高精度抓取和摆放,显著提升生产效率和保证加工质量.首先,介绍了新型辅助旋铆并联机器人机构的拓扑结构特征,并结合旋量理论及修正的G-K(Grübler-Kutz...     

基于机器人的复合材料缠绕策略优化

基于机器人的复合材料缠绕不同缠绕策略会对缠绕工艺及机器人运动稳定性产生影响, 为获得使机器人运动稳定性更优的缠绕策略, 研究了6自由度工业机器人的复合材料缠绕工作站, 单独分析了包络形式、悬纱长度以及测地线/非测地线缠绕等参数对缠绕工艺及机器人运动稳定性的变化参数的影响, 采用MATLAB进行不同缠绕策略的机器人缠绕轨迹计算, 确定规划后的缠绕轨迹, 基于ADAMS和MATLAB进行机器人缠绕动力学联合仿真, 获取机器人各关节力矩曲线, 分析规划后的缠绕轨迹对机器人运动稳定性的影响。进行了复合材料制品干纤维缠绕实验, 缠绕实验表明:采用优化后的缠绕策略进行复合材料制品缠绕时缠绕线型稳定, 缠绕过程无滑纱、交叠、架空等现象, 缠绕精度完全满足设计要求。      

Manufacturing of composite sandwich robot structures using the co-cure bonding method

The conventional manufacturing of composite sandwich structures is completed by adhesive bonding separately prepared composite faces to cores. The joining process during sandwich fabrication is a most difficult process, which requires strict quality control. However, the joining process can be eliminated when the sandwich structures are manufactured by the co-cure method inside a mold using the large difference of coefficient of thermal expansion between foam cores and steel mold.

In this work, the robot hands and wrists for handling large LCD glass panel displays were designed and manufactured using the co-cure method. Considering the non-linear thermal expansion properties of the foam during co-cure manufacturing, the pressure generated inside a mold was analyzed and the required pre-compression strain of the foam for sandwich beams was determined for enough consolidation. Finally, the composite sandwich robot hands and wrists were co-cure manufactured and the deflections of hands were measured under the weight of large LCD glass panel.     

Extended Kalman filter-based sensor fusion for operational space control of a robot arm

Accurate measurements of positions, velocities, and accelerations in both joint and operational space are required for achieving accurate operational space motion control of robots. Servomotors used for joint actuation are normally equipped with position sensors and optionally with velocity sensors for interlink motion measurements. Further improvements in measurement accuracy can be obtained by equipping the robot arm with accelerometers for absolute acceleration measurement. In this paper, an extended Kalman filter is used for multisensor fusion. The real-time control algorithm was previously based on the assumption of a jerk represented as a processed white noise with the zero mean. In reality, the accelerations are varying in time during the arm motion, and the zero mean assumption is not valid, particularly during fast accelerating periods. In this paper, a model predictive control approach is used for predetermining next-time-step jerk such that the remaining term can be modeled as Gaussian white noise. Experimental results illustrate the effectiveness of the proposed sensor fusion approach.     

基于视觉辅助定位的机械臂运动学参数辨识研究

标定机器臂的运动学参数可以有效提高机械臂的绝对定位精度。针对一般平面约束标定方法往往通过手动示教获取测量数据,效率低,提出一种基于视觉辅助定位约束平面的机械臂运动学参数辨识方法。为了弥补双目视觉视场范围狭小的弊端,在约束平面上粘贴3个靶点,以此将对平面的定位等效成对靶点的定位。应用双目视觉系统提取靶点中心并进行立体匹配,得到靶点在机械臂基坐标系下的三维位置信息;同时构建靶点坐标系,以此规划出按一定规律分布的约束点;为了进一步提高标定精度,建立双平面约束误差模型,通过两垂直平面上任意非共线的3个点得到一系列法向量,每一对法向量的数量积为0,即增加了约束方程;利用机械臂对相互垂直的两约束平面自动进行接触式测量,通过改进的最小二乘法辨识出真实的运动学参数误差。实验结果表明,基于双平面约束误差模型,修正运动学参数后,机械臂绝对位置精度由1.234 mm提高到了0.453 mm。该方法实现了数据的自动化测量,大大提高了标定效率,为机械臂批量标定提供了参考,具有工程意义。     

Nonstationary vibrations of robot construction elements made of composite materials

The effect of damping on nonstationary vibrations of elements of manipulators and mechanisms with flexible links is considered. To analyze nonstationary vibrations in the case of kinematic excitation, a finite-element frequency method was employed, which is based on numerical integral Fourier transformation.     

轮-履-腿复合仿生机器人步态规划及越障性能分析

为了提高移动机器人的越障性能,实现其自主越障,设计了一种轮-履-腿复合仿生机器人,并对其进行步态规划和越障性能分析。首先,以海龟为仿生对象,通过分析其身体结构和稳定机理,设计了机器人的轮-履-腿复合式移动机构和二自由度支腿结构;同时,基于该机器人的结构特征,利用D-H(Denavit-Hartenberg)法建立了坐标系并求解了其支腿的运动学方程。然后,通过观察海龟的爬行过程,将其单个爬行步态周期内的动作分解成放腿、爬行、抬腿和摆腿,并结合运动学模型对机器人进行步态规划,提出了4种仿海龟爬行步态。接着,以机器人的四腿爬行步态为例,利用静力学方法分析了其支腿关节的受力情况,而后通过分析机器人跨越壕沟和攀越台阶的过程,以最大跨越壕沟宽度和攀越台阶高度为指标对其越障性能进行了评价。最后,制作了机器人实验样机,开展了步态实验和越障实验。实验结果表明,该机器人可以利用4种仿海龟爬行步态实现横向移动、纵向移动和原地旋转,且具有很好的越障性能和稳定性;机器人能跨越最大宽度为434 mm的壕沟,攀越最大高度为175 mm的台阶。实验结果进一步验证了所设计的仿海龟机械结构可行,所规划的仿海龟爬行步态合理...     

Development of a compliant legged quadruped robot

This paper presents the detailed steps for design and development of a compliant legged fault tolerant quadruped robot where each leg has two links and two motorized revolute joints for locomotion. The body and upper links of legs are rigid whereas the lower link of each leg is compliant. Amble gait is demonstrated on the developed robot. Safety and reliability are the most critical issues for the quadruped robot. During the failure of any joint, performance of quadruped robot is affected. In this paper, locked joint failure is also discussed. Strategies for fault tolerant control of the quadruped are developed and experimentally validated. The developed robot can be used for various hardware-in-the-loop controller prototyping such as reconfiguration, fault tolerant control, and posture control, etc. pertaining to quadruped robots.     

Multiple eigenvalue optimization of composite structures using discrete third order displacement models

This paper deals with the implementation and test of a non-smooth eigenfrequency based criterion to evaluate the directional derivatives applied to multilaminated plate structures, when non-differentiable multiple eigenfrequencies occur during the structural optimization process. The algorithm is applied to a family of C⁰ Lagrangian higher order shear deformation theory discrete models. Angle ply design variables and vectorial distances from the laminate middle surface to the upper surface of each ply are considered as design variables. The efficiency and accuracy of the algorithm developed is discussed with an illustrative case. The analytical single and/or directional derivatives are compared to forward finite difference derivatives for the developed discrete models.     

用于并行结构机器人关节的开发方法

 与目前几乎仅绝对使用的串行结构相比，并行运动结构的机器人在各个领域的应用具有广阔前景。并行结构机器人的主要优点是有较高的结构刚度并可以实现较大的加速度。在并行结构机器人中，除了主动的关节(即驱动装置)之外，还需要被动的关节。这些被动的关节在大多数情况下都具有更多滑移自由度和转动自由度。对这些关节的要求主要是：移动性大、刚度高、质量轻以及结构空间紧凑。市场上现有的关节大都不能很好地满足这些要求。