面向微装配的显微视觉伺服

将基于显微视觉伺服的机械手的装配位姿调整归结为使其末端执行器上三点运动到指定空间三点的问题.规定其中一点沿直线运动到目标位置,其余两点则以绕该点旋转的方法运动到它们对应的目标位置,避免部件的运动干涉与碰撞,并确保末端执行器始终在显微镜的视场中.以机械手的路径规划为基础,给出基于距离和角度的图像特征差的估计方法,定义并建立基于图像特征差的图像雅可比矩阵以及机械手的运动模型.提出基于图像误差与控制信号综合优化的具有图像延迟系统的最优控制算法,基于动态视觉伺服控制策略建立比例控制与最优控制综合的视觉伺服控制结构,通过一个误差开关在不同的控制器上切换,进行直线位姿调整和动态目标跟踪试验.结果表明,所研究内容正确可行,系统定位精度保持在两个像素以内,具有较好的实时性,能满足微装配性能指标的要求.

Micro-visual Servoing for Micro-assembly

The pose adjustment of manipulator led and controlled by micro-vision is deduced for the problem how to make three points on its end-effector move for three set points in three-dimensional space respectively. A move planning is designed to avoid the collision and intervention of parts and to hold the end-effector in the visual field of the microscope, which stipulates one point mov-ing along a line to its goal position and the other two points moving to their respective goal positions by rotating on the first point. According to this planning, a method based on the distance and angle between lines is proposed to estimate the image feature devia-tion, and the image Jacobian and kinematic model of manipulator based on the image feature are defined and built. An optimal con-trol algorithm for the system with image delay is derived by the minimization of a cost function that allows weights to be placed on the error of the image features and the control signal. A micro-visual servoing control structure is designed to improve the positional accuracy, which includes a proportional controller and an optimal controller. The switch between the two controllers is selected by an error switch. Using a six-degree micromanipulator, experiments for adjusting line pose and tracking a moving target are performed to validate these researches. The results demonstrate that these researches are feasible and correct, and the location error is less than 2 pixels, which can satisfy the needs of the micro assembly.