压电智能柔性臂系统非线性耦合振动的分尺度协调控制方法研究

Flexible manipulator has been widely used in many applications offering significant advantages, such as low energy consumption and great load-to-mass ratio and so on. However, elastic vibration with large amplitude and long lasting period is unavoidable during operation, due to the complex coupling characteristics of the flexible manipulator system. And it leads to a deterioration of system positioning precision and operation efficiency.Through integrated analysis on the coupling relationships among the motor friction and torque characteristics, the joint flexibility, the vibration behaviors of the manipulator and the work principles of the piezoelectric actuators, the non-linear coupling vibration mechanism of the system is elaborated. And the method on characteristic model reduction and perturbation decoupling is proposed. Then, the multi-scale coordinate control strategy, which realizes coordination of the joint motor and PZT actuators control in separate time scale, is explored. The essence of this strategy is as follows: In the slow time scale, position control of the system, vibration suppression of the flexible joint and gross vibration control of the flexible manipulator are all realized through the joint motor control. While in the fast time scale, fast vibration of the manipulator is suppressed by the piezoelectric actuators. Meanwhile, the residual vibration of the link is also controlled by the actuators. Finally, the real-time coordinate control between the rigid motion and elastic vibration, the joint motor and piezoelectric actuators is achieved through the real-time workshop(RTW) control unit. The key technical issues on the multi-scale coordinate control of the smart flexible manipulator system can be solved, and the technical innovations of the flexible robot system are promoted by this research. Consequently, this research can provide theoretic and technical support for the application of the smart flexible structures.

具有能耗低及载荷/自重比高等优点的柔性臂应用日益广泛，但系统复杂耦合特性导致柔性臂易产生长时间、大幅值的振动，严重降低了系统定位精度和效率。项目通过综合分析压电智能柔性臂系统中电机驱动特性、关节柔性、臂杆柔性及致动器致动特性之间的耦合关系，揭示系统的非线性耦合振动规律；研究系统的特征模型降阶及摄动解耦技术；探究统筹关节电机和致动器在不同尺度内配合工作的分尺度协调控制方法及实现技术：在慢变尺度内，通过电机控制实现系统位置控制、关节振动抑制及臂杆振动粗略抑制，在快变尺度内利用致动器对臂杆快变振动进行控制，并对电机停止后的残余振动进行快速抑制，最终通过Real Time Workshop 实时控制平台实现系统刚性运动与弹性振动、关节电机与压电致动器的实时协调控制。通过开展项目研究解决压电柔性臂系统非线性耦合振动的分尺度协调控制关键技术，推动柔性机器人技术发展，为智能柔性构件应用提供技术理论支持。

柔性机械臂广泛应用于航空航天、工程机械及医学器械等领域。但其结构特性导致柔性机械臂系统在执行任务中极易产生振动，持续振动会造成疲劳破坏，显著影响了系统的定位精度和操作效率。而传统的控制方法重点关注柔性结构本身的振动特性及控制问题，而对柔性机械臂由于运动带来的非线性耦合振动问题缺乏有效控制。本项目引入压电材料在柔性结构多模态振动抑制中的有效作用，以伺服电机和谐波减速器组成伺服驱动关节，搭建了典型的单连杆压电柔性机械臂系统；对压电柔性臂系统进行了解析建模，确立了系统刚柔耦合、机电耦合特性，掌握了系统的非线性耦合动力学行为；并采用平均自回归滑动模型对压电柔性臂系统进行了实验建模及辨识研究，实验结果表明实验辨识模型与实际系统输出吻合度达90%以上；基于平衡降阶法利用Hankel奇异值从能控/能观性的角度对得到的系统实验模型进行了有效降阶，平衡降阶得到的低阶模型精度在85%以上；然后结合极点配置法与线性二次最优控制法提出了一种用于压电柔性臂系统多模态振动主动抑制的离散型最优极点移动法，有效抑制了外界激励下柔性臂的前两阶振动，其振动衰减时间由24s缩短为5s；最后提出了一种复合抑振轨迹规划与反馈控制的协调控制策略：该策略首先利用基于伺服电机的轨迹规划方法抑制压电柔性臂的主要弹性振动；其次利用压电致动器的最优极点移动法抑制柔性臂在运动过程中的高频振动以及运动结束后的残余振动。二者协调配合工作，实现了压电柔性臂系统运动与振动的协调控制。实验中压电柔性臂末端振动的衰减时间由五次多项式轨迹下的9s缩短为2.3s。项目研究实现了压电柔性臂系统振动的高精度快速有效抑制，提高了压电柔性臂系统末端的定位精度和指向精度，有效改善了压电柔性臂系统的操作效率。研究解决了柔性结构在实际应用过程中的振动抑制难题，为其在相关领域的应用和推广提供一定的理论基础和借鉴意义。