Design And Control Of 4PUS-PPPU Parallel Robot With Large Tilting Capacity

Parallel mechanism has higher structural rigidity,higher load-bearing capacity,lower inertia effect and higher kinematic precision because it is connected between the moving platform and the base by multiple chains.In recent years,parallel mechanism has become the best choice for high hardness parts processing equipment,heavy-duty robot,precision orientation adjustment platform,flight motion simulator and other applications.However,due to the structure characteristics of multiple closed loops,parallel mechanism has more singularity configuration and less available workspace,which further limits the practical application of the parallel mechanism.In this paper,a parallel mechanism with large tilting capacity based on self-adjusting drive branch chain is developed,and carried out research on kinematics,dynamics,control and experimental testing methods.From the mission requirements of five-face machining,this paper proposes a new type of 4PUS-PPPU parallel robot system scheme with high stiffness and large tilting capacity is proposed.The mechanism scheme includes 4 PUS peripheral branches and 1PPPU central branch.The three prismatic pairs of the central branch are all driving pairs.Under a given moving platform pose,the three prismatic pairs of the central branch chain can move in the given inverse solution space by finding a suitable position in the inverse solution space.Make the mechanism in the optimal performance state,so as to achieve the purpose of overcoming the singularity and improving the mechanism performance.For the proposed new 4PUS-PPPU parallel mechanism,the degree of freedom of4PUS-PPPU parallel mechanism is analyzed,the main parameters of the mechanism are determined,the kinematics model is established,and its singularity,stiffness and workspace are analyzed.Based on the detailed analysis of each part of the mechanism,the dynamic model is established based on the principle of virtual work.The redundant driving force is optimized by the minimum solution method of driving force norm,and the driving force of the redundant driving joint is solved.It provides the theoretical basis for the improvement of other drive joint driving forces by redundant drives.Combining with the dynamic model,the trajectory tracking control strategy of redundant actuated parallel mechanism is proposed,and the control algorithm adopts sliding mode control based on exponential approach law.After that,the effectiveness of the trajectory tracking control method is verified by the simulation model,and the effect of the sliding mode control algorithm is analyzed by the simulation results.Designed and manufactured a grinding robot system based on the 4PUS-PPPU parallel mechanism,carried out related performance tests and grinding experiments on the parallel robot,and verified that the prototype meets the design specifications,including the large tilting ability and five-face machining capacity.The feasibility of the proposed new parallel mechanism is proved.