Research On Force Control Of 3-TPT Parallel Robot

Steel billets snagging has been relied on manual force for the long time, which restricts productivity improvement of steel plants severely, and can hardly guarantee the quality of steels.3-TPT parallel robot has automatically grinded surface of steel billets recently in order to solve these problems such as low productivity produced by laborers. In the process of snagging, normal force should be controlled precisely which can make sure the quality of steels. Therefore, researching on force control of 3-TPT parallel robot will have great significance.Under analysis of technology of steel billets snagging, we get key factors that influence the quality of steel billets snagging. In order to realize consecutiveness of grinding process, we adopt clothoid curve related to corner trajectory of grinding wheel according to condition of grinding technology. Using impedance control as active compliance control strategy of 3-TPT parallel robot takes into consideration for controlling normal force precisely and characteristics of two kinds of force control. Impedance control based on position is employed as force control method to achieve steel billets snagging because of comparison by characteristics of two kinds of impedance control and consideration with control means of traditional robots. We analyze steady-state position error and force error of the whole system according to impedance control based on position and environment factors giving rise to steady-state error. At the same time, we analyze the whole system dynamic performance and ideal impedance parameters having an influence on system performance.As a result of 3-TPT parallel robot as object of study of research paper, we mainly deduce its kinematics, inverse kinematics, velocity, acceleration, jacobian matrix, inverse jacobian matrix and so on, in order to build simulation platform. Simultaneously, we conduct position control with PD plus gravity control method, PD plus feed forward control method and computed torque method under interference of noise in order to choose an effective control strategy for guaranteeing force control system successfully realizing the goal. We conduct tracking test of normal force with impedance control based on position under constant condition of environment factors, and analyze the performance of control system and influence of impedance parameters. Furthermore, building force/position hybrid control system which conducts tracking test of normal force in order to compare with performance of impedance control system. Under the varying condition of environment factors, coming up with force control based on fuzzy rule solves problem that traditional control can not work out.Taking parallel robot mechanism characteristic into consideration, we introduce synchronous control policy for force control. Under condition of synchronous control policy, dynamic error of 3-TPT parallel robot comes to ideal state. Moreover, we put forward force control policy based on synchronous control, test the performance of control system, and make an assessment of it.