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具有柔性关节的冗余机器人柔顺控制研究
Alternative TitleResearch on Compliant Control of Redundant Robot with Flexible Joints
侯澈
Department机器人学研究室
Thesis Advisor赵忆文
Keyword协作型机器人 柔顺控制 冗余机械臂 机器人动力学 人机协作
Pages126页
Degree Discipline模式识别与智能系统
Degree Name博士
2020-05-29
Degree Grantor中国科学院沈阳自动化研究所
Place of Conferral沈阳
Abstract目前,协作型机器人正处于快速发展阶段,在人机协作场景中,机器人具备与环境柔顺接触的能力十分必要。柔顺控制是解决机器人与环境接触问题的重要方法,而协作型机器人复杂的运动特性以及人机协作场景的不确定性给控制器的设计带来了极大挑战,本文针对协作型机器人的柔顺控制方法展开研究,主要研究内容如下:首先针对协作型机器人的动力学建模与模型参数辨识方法展开研究。建立了刚、柔耦合动力学模型。为获得精确的模型参数,本文针对协作型机器人复杂的动态特性,从以下方面展开刚、柔耦合动力学模型参数辨识方法的研究:针对柔性关节参数的辨识问题,提出了基于关节谐振与抗谐振频率特征的频域辨识方法,该方法有针对性地利用柔性关节的谐振与抗谐振的频率与幅值信息建立参数计算模型,减少了测量噪声与误差对辨识结果的影响;针对由机器人连杆组成的刚体动力学参数辨识问题,提出了基于静、动态激励的分步辨识方法,改善统一辨识时多关节耦合干扰问题和逐一辨识时误差逐级传递问题。柔性关节内部具有复杂的动态特性,影响整体控制性能以及鲁棒性,针对该问题,本文提出一种高、低频混合力矩控制方法作为底层控制方法,其主要作用是消除柔性关节内部动态特性对系统的影响,如柔性抖振,非线性摩擦力以及负载变化引起的模型摄动等。该方法以扰动观测器的基本结构为基础,通过Q滤波器将闭环系统的频率特性分离,并分别针对不同频段的频率响应特性设计控制器:在低频段,系统的动态特性接近名义模型,因此,以柔性关节的名义模型作为被控对象,设计控制器并将闭环系统构造为标准的二阶系统,将低频控制器的设计问题被转变为标准二阶系统的设计问题;在系统的高频段,测量噪声、模型摄动以及摩擦力扰动对系统鲁棒性具有较大影响,针对该问题,提出了基于混合灵敏度求解方法设计高频控制器。最后本文推导了该方法的全局稳定性条件。进一步针对冗余机器人在笛卡尔空间的阻抗控制问题展开研究。研究分两部分进行,第一部分为机器人末端在笛卡尔空间阻抗控制问题的研究,第二部分为机器人冗余自由度阻抗控制问题的研究。第一部分根据目标阻抗关系推导了笛卡尔空间阻抗控制律,控制律的状态变量中含有欧拉角,针对欧拉角在连续运动中的突变问题,本文将欧拉角的解划分为两种状态,并设计状态转换条件使欧拉角的解在连续运动中始终保持连续,从而增强了阻抗控制的鲁棒性。第二部分针对机器人冗余自由度的阻抗控制问题展开研究,研究对象限定为具有S-R-S构形的7自由度机器人,首先根据S-R-S构形的空间几何特征对冗余自由度的位置与接触力进行参数化处理,并针对冗余自由度的柔顺控制问题设计了冗余阻抗控制方法,实现冗余自由度位置与力的统一控制。进一步,在该冗余阻抗控制方法的基础上提出了运动优化方法,该方法的主要优势是降低了搜索空间的维度,简化了运算。最后,本文对上述方法进行了综合实验研究。搭建了7自由度协作型机器人原理样机实验平台以及单关节实验平台,实验结果验证了所提方法的可行性以及有效性。
Other AbstractAt present, collaborative robots are in a stage of rapid development. In human-robot collaboration scenarios, it is necessary for robots to have the ability to contact the environment smoothly. Compliance control is an important method to solve the problem of robot contact with the environment. However, it takes great challenges to the design of the controller due to the complex motion characteristics of collaborative robots and the uncertainty of human-robot collaboration scenarios. This article studies the compliance control problem of collaborative robots. The main research contents are as follows: This paper firstly studies the modeling and parameter identification of the cooperative robot. The coupling dynamic model of rigid links and flexible joints is established. In the process of robot dynamics model identification, due to the large number of parameters to be identified, and the large difference in the contribution of each parameter to the measurement data, there is a problem of parameter interference. The model of the robot system to be identified is divided into two parts: one part is the robot rigid body Dynamic model, the other part is the flexible joint model. During the identification process of rigid body dynamics model, there are large noises in the joint velocity and acceleration, which affects the accuracy of the identification results. For this problem, this paper proposes a step-by-step identification method based on static and dynamic excitation data. The mathematical model is decomposed into two parts, one of which are only related to static variables. Experimental data is collected by designing static and dynamic excitation experiments, and the two parts of the model are solved step by step to obtain identification results. For the parameter identification of flexible joints, for the problem of measurement noise interference, this paper proposes a frequency domain identification method based on the characteristics of resonance and anti-resonance of flexible joints. This method uses the relationship between the frequency and amplitude of resonance and anti-resonance points to model parameters The parameter identification model is obtained, and the parameters are solved by the least square method. The internal dynamic characteristics of flexible joints are very complex, which affects the overall control performance and robustness. For this problem, this paper proposes a high/low frequency mixed torque control method, and uses it as the inner loop of the impedance control method to weaken the interior of the flexible joint The impact of dynamic characteristics. This method first considers the vibration and hysteresis caused by joint flexibility, the nominal model of the flexible joint is taken as the controlled object, a controller is designed to construct a standard second-order system, and the control problem of the flexible joint is transformed into the problem of the standard second-order system. Further, considering the problem of model perturbation caused by uncertain friction and load changes in the actual system, a disturbance observer is introduced on the original control structure to compensate for disturbance and model perturbation, but the disturbance observer can only have good performance of disturbance compensation and model perturbation compensation in a certain frequency range. In order to have a better control effect in the entire frequency range, this paper proposes a high/low frequency hybrid torque control method based on the disturbance observer, and the stability boundary conditions of the control parameters are given. Further, the problems of impedance control for redundant robots in Cartesian space are researched. The research is conducted in two parts. The first part is the research on the impedance control of the robot's end effector in the Cartesian space, and the second part is the research on impedance control of the robot's redundant degree of freedom. The Cartesian space impedance control law is derived based on the target impedance relationship. The state variable of the control law contains Euler angle, and for the sudden change of Euler angle in continuous motion, this paper divides the Euler angle solution into two states and design the state transition conditions to keep the Euler angle solution continuous in continuous motion, thus enhancing the robustness of impedance control. The problem of impedance control for the redundant degrees of freedom is studied in the second part. In this paper, the research is limited to a 7-degree-of-freedom robot with S-R-S configuration. First, the redundant degrees of freedom are parameterized according to the spatial geometric characteristics of the S-R-S configuration. The problem of impedance control for redundant degrees of freedom is transformed into the control of the dynamic relationship between the torque and the rotation angle of the self-moving shaft, and a redundant impedance control method is designed to realize the unified control of position and force with redundant degrees of freedom. Further, this paper gives a control quantity optimization method based on the proposed redundant impedance control framework. The main advantage of this method is to reduce the dimension of the search space and simplify the calculation. Finally, this article has carried on the comprehensive experimental research to the above-mentioned method. A prototype experimental platform and a single-joint experimental platform for a 7-degree-of-freedom collaborative robot principle were built. The experimental results verified the feasibility and effectiveness of the proposed method.
Language中文
Contribution Rank1
Document Type学位论文
Identifierhttp://ir.sia.cn/handle/173321/27159
Collection机器人学研究室
Affiliation中国科学院沈阳自动化研究所
Recommended Citation
GB/T 7714
侯澈. 具有柔性关节的冗余机器人柔顺控制研究[D]. 沈阳. 中国科学院沈阳自动化研究所,2020.
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