The Anti-Swaying Control Research Of Crane Based On Vision Servo

Vision servo technique utilizes the computer vision theory for high-speed image information processing and feature extraction to realize closed-loop control of the system based on the feedback information. Using vision as its main approach to obtain outside information, vision servo system features extensive information and high intelligence and therefore is presently widely used in the field of industrial robot, micro-operation robot and spacecraft docking system. At the same time, crane, as a kind of transfer tools, plays a significant role in industrial manufacturing. Consequently, how the swaying during goods lifting can be eliminated to achieve high working efficiency of the crane has always been a classical concern for control study. The key point to damping out swaying is the accurate measurement of the angle. Using contact measuring method, traditional angle measuring devices, however, are installed inside the crane system and characterize complicated mechanical structure and poor ability of independence accordingly. The thesis introduces vision servo technique into the anti-swaying control over the crane. Moreover, non-contact measurement is achieved based on computer vision method and inverse system nonlinear control strategy is employed to realize the positioning and anti-swaying control of the crane system.This paper initially focuses on hardware components of angle vision measuring system. In the light of computer vision measurement requirement of the angle, a set of rapid and effective image processing and feature extraction methods is proposed and the feasibility of these methods is analyzed and tested as well in this paper. The experimental results show that the computer vision measuring method, which has a big distinguishable rate, a wide range of measurement, can guarantee the measuring accuracy of the angle and satisfy the need of real-time control; therefore can be used in the positioning and anti-swaying control of the crane system.Based on the physical model of the crane system, this paper builds up a mathematical model in terms of Langrange equation of analytical mechanics. In essence, as a multi-variable, nonlinear, strong-coupled underactuated mechanical system, the crane is complex in model and difficult to control because its number of control input is less than that of system's degree of freedom. To cope with this problem, the inverse system nonlinear control method is applied firstly for the decoupling of the crane system, then a position and cord length servo controller and swaying controller are designed to put forward the positioning and anti-swaying control strategy of the crane in case of changeable cord lengths. The simulation results demonstrate that the proposed control strategy can realize the accurate positioning and anti-swaying of the crane system.Finally, computer vision measuring method of the angle and inverse system nonlinear control strategy are employed to conduct object experiments on the crane experimental system platform, and positioning and anti-swaying control over the crane is realized based on vision servo thereby. Moreover, the designed controller has good robustness for variable mass of the payload.