欠驱动柔性机械臂的动力学建模与控制

针对欠驱动柔性机械臂建模、控制困难的问题,文中采用在第一关节安装轻质弹簧的方法来表示机械臂的柔性,从而得到柔性臂的简化模型。将其应用到两连杆欠驱动柔性机械臂中,建立欠驱动柔性机械臂的系统模型,并利用拉格朗日函数法,对该系统进行动力学建模。同时通过构造基于系统能量和驱动杆状态的李雅普诺夫函数,设计该欠驱动柔性机械臂系统的控制律。最后,使用Matlab对该系统及所设计的控制律进行数值仿真。仿真结果表明,所构建的动力学模型以及设计的控制规则具有良好的有效性,且同时具备响应速度快、控制输入小的优点。     

一种柔性曲柄滑块机构的解耦控制方法

基于对柔性机构运动学和动力学模型的分析与解耦,提出一种解耦控制方法。这种方法有效地利用了模型信息,将反馈划分为由刚性和柔性运动两路反馈,通过两组不同的控制器分别计算各自的输出量,并在控制器输出端叠加输出。针对曲柄滑块机构进行柔性动力学建模并实施了轨迹跟踪仿真。与同样基于动力学模型的计算力矩法进行了对比,结果证明本方法的可行性和高效性。     

压电陶瓷驱动器在机器人柔性臂应用中的研究

研究了片状压电陶瓷驱动器在柔性手臂中的应用,推导了基本压电陶瓷驱动器的柔性臂静力学方程,建立了描述驱动器迟滞特性的Ｐｒｅｉｓａｃｈ模型,提出了一种基于Ｐｒｅｉｓａｃｈ前钏环的ＰＩＤ掏方法对柔性夺动主动控制和轨迹控制俞中以有效地克服片状压电陶瓷驱动器的迟滞特性,消除柔性臂运动产生的振动,实现柔性臂的精度轨迹控制。     

两自由度柔性臂压电陶瓷抑振方案优化设计

振动控制是柔性臂控制的主要任务。两自由度柔性臂系统是非性线系统，并且存在强运动耦合，模型复杂。因此有效的抑振方案对柔性臂控制至关重要。该文以两自由度柔性臂残余振动分析为依据，对压电陶瓷作动器与振动传感器的布置位置进行了优化设计，提出了压电陶瓷作动器与振动传感器相结合的抑振方案。实验证明这种抑振方案是有效的。     

SMA驱动的仿章鱼多关节柔性臂研究及发展分析

仿生柔性臂是从自然界软体动物的运动功能中获得灵感,基于功能仿生和结构仿生原理研制的新型机械臂。采用形状记忆合金(ShapeMemoryAlloy,SMA)丝作为制动器,能有效提高仿生机械臂的柔性,减轻重量,简化结构,研制一种SMA丝驱动的高性能仿生柔性机械臂为水下探测、取样提供一种重要智能装备,研究具有理论意义和实用价值。本项目从章鱼触手的解剖结构中获得灵感,提出研制一种驱动-缠绕-抓取一体化的软体柔性臂机器人。建立好力学模型后,通过记忆合金丝驱动柔性臂。本实验研究不同电压以及占空比的作用下,柔性比的弯曲结果。实验验证了力学模型的成立,实现了柔性臂连续行的矢量弯曲,得到了驱动电压、驱动时间、弯曲角度以及占空比之间的关系。     

基于Matlab和Adams的超速机柔性轴系仿真

在通用型机械强度超速试验机的柔性系统中,柔性轴在高转速下会出现变形过大的问题,影响试验结果的准确性。结合以往设计经验,在理论研究的基础上,利用有限元法和拉格朗日方程建立柔性轴系运动方程,运用Matlab求解出相应的质量矩阵、刚度矩阵,得出了柔性轴系在瞬态和稳态情况下的运行情况。并利用Adams进行柔体动力学分析,得出在瞬态和稳态情况下柔性轴系的运行情况与理论计算结果进行对比,其结果基本一致,验证了理论计算和系统柔性仿真的正确性。     

基于凯恩方程的机械臂固定时间滑模控制

针对存在未建模动态和随机干扰等因素影响下的机械臂轨迹跟踪控制问题,提出了一种新型非奇异固定时间滑模控制策略.首先,利用凯恩方程和虚功原理,推导了n自由度机械臂的动力学方程;然后,由固定时间稳定理论设计了新型固定时间滑模面,结合6R机械臂的凯恩动力学模型,针对机械臂的模型参数不确定性和外界干扰,设计了非奇异固定时间滑模控制器,并基于Lyapunov理论证明了系统的稳定性;最后的数值仿真表明,所设计的控制器能保证系统状态的收敛不依赖于初始条件,并具有更快的收敛速率和更短的收敛时间以及良好的鲁棒性.     

串联机械臂运动控制系统设计

由于加工装配的累积误差,驱动控制,机械臂的柔性变形以及实际工作环境中振动等因素的干扰,导致无法准确获取机械臂的运动学模型和动力学模型,导致机械臂实际的运动性能与期望的高精度运动性能相比出现较大的差距。针对上述问题,文中通过研究串联机械臂轨迹优化算法,设计了一套简单且实时性的机械臂控制变量补偿系统,以减少甚至消除机械臂的运动学误差。这一技术的实现,将对提高装备制造业中机械臂运动精度关键技术的发展起到推动作用。     

分布柔度桥式位移放大机构静动力学性能研究

该文对分布柔度桥式位移放大机构的放大比、刚度特性及固有频率等静动力学性能进行了研究。首先,根据柔性梁单元的刚度矩阵建立了该放大机构的位移放大比及其输入刚度解析模型。随后根据柔性梁的变形曲线方程,通过求解变形曲线对时间的导数,得到梁上任一点速度以获得柔性梁在机构振动过程中动能表达,在此基础上,利用拉格朗日法建立了具有3个广义坐标的桥式放大机构的振动方程,并得到其工作方向的固有频率。最后利用有限元与实验方法对其动力学性能进行了测试。实验结果表明,解析计算结果与有限元分析及实验结果较吻合,证明了所建立的解析模型的准确性。     

硅橡胶的硫化机理研究

本文综述了硅橡胶硫化反应的动力学机理和硫化反应动力学的研究方法和手段，介绍了各种不同的硫化反应机理及其相应的动力学模型，列举出硅橡胶硫化反应的动力学方程。并重点阐述了硅橡胶硫化动力学的物理化学法和硫化仪法，在研究过程中将两者结合，最后对其结果进行综合分析。     

Dynamic formulation of redundant and nonredundant parallel manipulators for dynamic parameter identification

Utilizing the virtual work principle, this paper presents a method for the dynamic formulation of redundant and non-redundant parallel manipulators for dynamic parameter identification. In modeling, the selection of pivotal point and the computation of inertia force and moment about the pivotal point are more crucial. The selection principle of pivotal point and force transmission on a rigid body are studied. In order to validate the method, the linear form of dynamic models of a 3-DOF parallel manipulator with actuation redundancy and its corresponding non-redundant parallel manipulator are derived.     

An optimal information method for mobile manipulator dynamic parameter identification

High-performance robot-control algorithms often rely on system-dynamic models. For field robots, the dynamic parameters of these models may not be well known. The paper presents a mutual-information-based observability metric for the online dynamic parameter identification of a multibody system. The metric is used in an algorithm to optimally select the external excitation required by the dynamic system parameter identification process. The excitation is controlled so that the identification favors parameters that have the greatest uncertainty at any given time. This algorithm is applied to identify the vehicle and suspension parameters of a mobile-field manipulator, and is found to be computationally more efficient and robust to noise than conventional methods. Issues addressed include the development of appropriate vehicle models, compatible with the onboard sensors. Simulations and experimental results show the effectiveness of this algorithm.     

Identification of dynamic and friction parameters of a parallel manipulator with actuation redundancy

The dynamic model is formulated in the joint space for a parallel manipulator with actuation redundancy. The established model is expressed in its linear matrix form with respect to the dynamic and friction parameters, and then the Weighted Least Square (WLS) method is applied to estimate the parameters. In order to get satisfying estimated results, the filters of joint angle and actuated torque are designed for the parallel manipulator. A simple and effective method is presented to design the excitation trajectory by analyzing the mechanism structure characteristics of the actual parallel manipulator. Another type of trajectory which is different from the excitation trajectory is adopted to verify the estimated parameters. The dynamic control experiments based on the identified model with the estimated parameters are implemented on an actual 2-DOF parallel manipulator with actuation redundancy, and the tracking accuracy of the identified model is compared with the result of the so-called nominal model.     

A hybrid dynamic model for the AMBIDEX tendon-driven manipulator

Tendon-driven actuation allows for light and compact manipulator designs with enhanced safety features. One of the key challenges in model-based control of tendon-driven robots is the increased complexity of the dynamic model, due in large part to difficult-to-model behavior like nonlinear dynamic deformation and friction at the tendons. While purely data-driven modeling approaches, e.g., neural networks, free one from dealing with complex and often error-prone mechanics models, they usually do not generalize well to diverse tasks, and also do not offer the needed intuitive understanding or predictive power of traditional mechanics-based models. In this paper, we present a hybrid modeling approach for complex tendon-driven robots, which effectively complement the limitations of pure physics-based and data-driven learning-based approaches. Rigid multibody equations of motion are augmented with (i) a configuration-dependent viscous-Coulomb friction model and (ii) a recurrent neural network that captures the tendon dynamics, and estimates link joint angles from the motor positions, velocities, and torques. Experiments involving a two-dof tendon-driven parallel wrist mechanism and the 7-dof AMBIDEX tendon-driven manipulator validate the performance advantages of our hybrid model-based control framework.     

Design and implementation of an adaptive recurrent neural networks (ARNN) controller of the pneumatic artificial muscle (PAM) manipulator

This paper presents the design, development and implementation of an adaptive recurrent neural networks (ARNN) controller suitable for real-time manipulator control applications. The unique feature of the ARNN controller is that it has dynamic self-organizing structure, fast learning speed, good generalization and flexibility in learning. The proposed adaptive algorithm focuses on fast and efficient optimization by weighting parameters of inverse recurrent neural models used in the ARNN controller. This approach is employed to implement the ARNN controller with a view to controlling the joint angle position of the highly nonlinear pneumatic artificial muscle (PAM) manipulator in real-time. The performance of this novel proposed controller was found to be superior compared with a conventional PID controller. These results can be applied to control other highly nonlinear systems as well.     

6R机械手在CMP设备中的运动空间分析

工作空间是一个衡量机械手工作能力的重要运动学指标。通过分析抛光机中机械手的工作流程，确定了机械手工作空间；并利用D-H坐标法，建立6R机械手的数学模型，得到机械手来端坐标系相对于基坐标系的传递矩阵。最后，采用蒙特卡洛数值分析法，仿真了机械手的运动空间，结果显示，该机械手的运动空间大于设备要求的工作空间。满足CMP设备的...     

Computed force and velocity control for spatial multi-DOF electro-hydraulic parallel manipulator

A novel dynamic trajectory tracking controller for spatial 6-DOF electro-hydraulic parallel manipulator considering system nonlinearity-computed force and velocity controller is proposed, with a view of improving the control performance with high computational efficiency of control algorithm. The dynamic model of electro-hydraulic parallel manipulator, both mechanical and hydraulic system, is described by using Kane and hydromechanics method. The requisite system states are estimated via forward kinematics based upon global Newton–Raphson with monotonic descent algorithms under the measured actuator position. The desired leg position and velocity required for the proposed controller are calculated by an analytical method corresponding to the desired generalized pose, and the desired driven force is computed with an effectively simplified inverse dynamics. Under feed-forward of the desired driven force and velocity, the computed force and velocity controller is developed with actual leg position as its feedback only, and the desired leg position, velocity and driven force as its input. The control performance of the proposed controller for multi-DOF parallel manipulator is evaluated in theory and experiment, especially for dynamic tracking performance. Experimental results show that the presented controller can greatly improve the dynamic trajectory tracking performance for high real time electro-hydraulic parallel manipulator.     

Modeling and Identification of Elastic Robot Joints With Hysteresis and Backlash

This paper presents a novel approach to the modeling and identification of elastic robot joints with hysteresis and backlash. The model captures the dynamic behavior of a rigid robotic manipulator with elastic joints. The model includes electromechanical submodels of the motor and gear from which the relationship between the applied torque and the joint torsion is identified. The friction behavior in both presliding and sliding regimes is captured by generalized Maxwell-slip model. The hysteresis is described by a Preisach operator. The distributed model parameters are identified from experimental data obtained from internal system signals and external angular encoder mounted to the second joint of a 6-DOF industrial robot. The validity of the identified model is confirmed by the agreement of its prediction with independent experimental data not previously used for model identification. The obtained models open an avenue for future advanced high-precision control of robotic manipulator dynamics.     

Static balancing and dynamic decoupling of the motion of manipulation robots

The conditions for simplification of moment actions of the particular DOFs of a manipulator are derived, and the individual components of the moment actions are determined. Mechanical unloading of a multi-link manipulator from the moments due to gravitational forces are also analysed. The specificity of dynamic decoupling of the manipulator motion is considered. Examples of different types of balancing and unloading with manipulation mechanisms are given.