The Six Dof Parallel Adjusting Mechanism Optimal Time Trajectory Planning And Stability Control

In recent years, with the continuous improvement of automation degree in aircraft, ships and other manufacturing production, the traditional assembly methods through using a large number of fixed-frame parts to support and locate the assembled components and artificial docking assembly, has become increasingly unable to meet the requirements of modern machinery manufacturing industry. In order to overcome the problem in traditional method of assembling of a low degree of automation, low productivity, the quality which is not stable enough, and the shortcomings of poor adaptability to different parts, with the rapid development of assembly technology, a kind of flexible assembly technology based on six DOF attitude adjustment mechanism is widely used in modern large parts assembled.Position and orientation adjustment, refers to the parts to adjust the position and orientation in the assembly process, and its implementation process is: First, measure the components currently pose, and then control system calculate the difference between the current position and orientation and the target position and orientation, and solve the position and orientation trajectory of components. Finally, control system driven attitude adjustment mechanism to complete the whole attitude adjustment movement. In this article, by establishing the kinematics and dynamics equations of attitude adjustment mechanism, using polynomial equation to fit components trajectory, and using dichotomy method to look for optimal time of attitude adjustment movement, the problem of trajectory planning when components mass and center of gravity changing, and the time and path of attitude adjustment uncertain, is solved. Meanwhile, this article also designs a tricyclic servo control system of motion axes of attitude adjustment device which compose attitude adjustment mechanism, analyzes the influence of the components mass changing to the control system, and use NLPID controller to solve the traditional PID controller for control effects of load and interference which is not ideal.First, this article reviews the development of assembly technology in domestic and foreign, and the application of parallel institutions pose as the adjustment mechanism, and introduces the structure and working principle of six DOF attitude adjustment mechnism.Secondly, analyze the structural characteristics of attitude adjustment mechanism, establish the kinematics and dynamics model of whole system, and get the relations between components’ pose and driven sides’ movement under uncertain conditions of components mass and center of gravity.Then the article does research of trajectory transferred from the initial position and orientation to the end. Set time as a parameter, and set the physical limits of the driven-side component features as motion constraints, in order to adapt different components mass. Through setting positional relationship constraints between component centroid and the projection of attitude adjustment device contact point, the article solves the tipping problem made by uncertain component centroid. Use dichotomy method to look for optimal time of attitude adjustment movement and finally get the optimal time based drive joints trajectory.The next, design position servo system, and ensure attitude adjustment mechanism tracking pose instruction accurately, rapidly and smoothly. Analyze the effect of control system caused by different components mass and the input of load and disturbance, and improve servo system to achieve control requirements in above-described unstable environment.Finally, use MATLAB simulation to complete the work of modeling and simulation of the six DOF attitude adjustment mechanism trajectory planning and servo control system.