Control of a Flexible Manipulator Using Hierarchical Multi-processors

传统上，机械手的定位精度是通过增加系统的刚性来提高的。然而，高刚性会导致质量增加，从而导致效率和高速性能的恶化。通过开发一种考虑了连杆灵活性的控制策略，可以设计出具有高定位精度的轻型机械手。本文提出了一种采用分层多处理器的实时控制系统，每个关节具有状态反馈。利用该柔性机械臂系统，实现了高工作速度下的精确控制。研究结果总结如下：1.只考虑杆件第一阶振型的柔性机械臂的简单数学模型是足够精确的，而考虑高阶振型的精确模型则非常复杂，因此不适合控制目的。在方程的线性化过程中，部分引入了非线性反馈。这比围绕平衡点的简单线性展开提供了更好的结果。杆件变形的动态反馈是一种有效的主动减振手段。前馈补偿库仑摩擦对提高定位精度和抑制残余弹性振动是有效的。为了进一步提高定位精度，并补偿有效载荷或摩擦力的变化，为每个关节安装了I型伺服机构。在设计过程中，采用模态分解的方法对控制系统进行降阶，忽略了不同振型之间的干扰引起的高阶振型。然而，这项研究的机械手在溢出方面没有问题，因为它有足够的结构阻尼。

Conventionally, the positioning accuracy of robot manipulators has been improved by increasing the rigidity of the system. A high rigidity, however, results in an increase in mass which leads to deterioration in efficiency and high-speed behaviour. By developing a control strategy in which the flexibility of the link is taken into account, we can design a light manipulator with high positioning accuracy. This paper presents a real-time control system using hierarchical multi-processors with a state feedback for each joint. Using this flexible manipulator system, a precise control at high working speed is demonstrated. The outcome of this research is summerized as follows:1. A simple mathematical model of the flexible manipulator which considers only the first mode of the link proved to be sufficiently accurate, whereas a precise model considering higher modes is extremely complicated and therefore not suitable for control purposes.2. In linearing the equation, non-linear feedback was partially introduced. This gave better results than a simple linear expansion around the equilibrium point.3. Dynamic feedback of link deformation proved to be an effective means of active damping.4. Compensation of Coulomb's friction by feedforward was effective in improving positioning accuracy and damping the residual elastic vibration.5. In order to achieve further precision in positioning and to compensate for changes in payload or friction, a type I servomechanism was implemented for each joint.6. In the designing process, the control system was reduced by means of modal decomposition neglecting high-order vibration modes caused by interference between different modes. Nevertheless, the manipulator for this study had no trouble with respect to spillover because of its sufficient structural damping.