一种含柔性杆件的空间并联机器人控制策略的研究

发布时间：2019-04-25 19:21

【摘要】：本文针对提高柔性多体系统轨迹跟踪精度的要求,将一种含有柔性杆件的3-RRRU空间并联机器人作为研究对象,系统地分析了该刚柔混合系统的非线性正动力学模型和逆动力学模型,提出了一种适用于闭链机构的柔性动力学方程的求解方法,并根据系统的逆动力学模型对控制策略进行了研究,所取得的研究成果如下:(1)基于向量环法建立了刚性3-RRRU并联机器人的逆运动学模型,然后利用牛顿-欧拉法求出了各个运动关节的约束反力和约束力矩。基于自然坐标法构建了刚性空间梁单元和刚性动平台的质量矩阵,并根据拉格朗日法求出了刚性机构的动力学模型,同时验证了该方法与参考坐标法建立的动力学模型具有等效性。并联机构的刚性模型为其柔性动力学模型的构建和求解提供了重要的理论依据。(2)针对刚性3-RRRU并联机器人,在考虑所有关节摩擦力矩的情况下,基于运动学模型和动力学模型提出了一种新型的近似时间最优的平滑轨迹规划方法,通过引入相平面上的零值伪加速度曲线,能够有效地确定轨迹的加减速过程,并通过理论和实验论证了规划方法的可行性和有效性,总结出并联机器人和串联机器人在规划过程中体现出的不同特性,该方法可用于柔性并联机器人的轨迹规划。(3)利用自然坐标法和绝对节点坐标法构建了刚柔混合3-RRRU并联机器人的非线性动力学模型。与传统的线弹性动力学方法相比,该模型不仅未做任何线性化处理,而且考虑了柔性空间梁单元的剪切效应,同时可描述柔性构件的大范围弹性变形。(4)为了避免连续介质力学中泊松闭锁现象的发生,对弹性矩阵和应变能进行了合理分割,同时针对并联机构的特性,给出了计算弹性力及其雅克比矩阵的新方法,从而提高了求解的计算效率。根据柔性并联机器人动力学方程的特性,对其求解原则、求解方法和求解性能进行了详细的分析和说明。(5)针对柔性并联机器人动力学模型在求解过程中出现的破坏刚性约束的问题,提出了一种瞬态刚体校正法,从而保证了数值迭代方法在求解动力学模型正解和逆解过程中的正确性。然后,根据所获得的逆动力学解构建了系统的控制策略,并通过动态轨迹跟踪实验验证了控制策略的可行性,说明了仿真分析结论与实验结果具有良好的一致性。
[Abstract]:In order to improve the trajectory tracking accuracy of flexible multi-body system, a kind of 3-RRRU spatial parallel robot with flexible member is taken as the research object in this paper. The nonlinear positive dynamic model and the inverse dynamic model of the rigid-flexible hybrid system are systematically analyzed, and a method for solving the flexible dynamic equations suitable for closed-chain mechanisms is proposed. According to the inverse dynamic model of the system, the control strategy is studied. The results are as follows: (1) the inverse kinematics model of the rigid 3-RRRU parallel robot is established based on the vector loop method. Then the constraint reaction and binding moment of each motion joint are obtained by Newton-Euler method. Based on the natural coordinate method, the mass matrix of rigid spatial beam element and rigid dynamic platform is constructed, and the dynamic model of rigid mechanism is obtained according to Lagrangian method. At the same time, the equivalence of the dynamic model established by this method and the reference coordinate method is verified. The rigid model of the parallel mechanism provides an important theoretical basis for the construction and solution of the flexible dynamic model. (2) for the rigid 3-RRRU parallel robot, the friction torque of all joints is considered. Based on kinematics model and dynamics model, a new approximate time optimal smoothing trajectory planning method is proposed. By introducing zero-valued pseudo-acceleration curve on the phase plane, the acceleration and deceleration process of trajectory can be effectively determined, and the path acceleration and deceleration process can be effectively determined by introducing zero-valued pseudo-acceleration curve on the phase plane. The feasibility and effectiveness of the planning method are proved by theory and experiment, and the different characteristics of parallel robot and series robot in the planning process are summarized. This method can be used in trajectory planning of flexible parallel robot. (3) the nonlinear dynamic model of rigid-flexible hybrid 3-RRRU parallel robot is constructed by using natural coordinate method and absolute node coordinate method. Compared with the traditional linear elastic dynamics method, the model not only does not do any linearization, but also takes into account the shear effect of the flexible spatial beam element. At the same time, the large-scale elastic deformation of flexible components can be described. (4) in order to avoid the occurrence of Poisson locking in continuum mechanics, the elastic matrix and strain energy are segmented reasonably, and the characteristics of parallel mechanism are pointed out. A new method for calculating elastic force and Jacobian matrix is presented, and the computational efficiency is improved. According to the characteristics of dynamic equations of flexible parallel manipulators, the principle of solving the equations is given. The solution method and performance are analyzed and explained in detail. (5) A transient rigid body correction method is proposed to solve the problem of rigid constraint failure in the dynamic model of flexible parallel robot. Thus, the correctness of the numerical iterative method in solving the positive and inverse solutions of the dynamic model is guaranteed. Then, according to the obtained inverse dynamic solution, the control strategy of the system is constructed, and the feasibility of the control strategy is verified by the dynamic trajectory tracking experiment, which shows that the simulation results are in good agreement with the experimental results.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TP242
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本文编号：2465391