Modeling And Simulation Of Concrete Pump Truck Arm System Based On Flexible Multi-Body Dynamics

With the development of the economic construct in China, the commercial concrete industry and the construction machinery business step into a new stage, in which the construction scale and scope become boarder and boarder, and the demand of the concrete machine from the market become stronger and stronger, so that the rapid development of the concrete transportation machine expand the market space of the concrete pump truck. Nowadays the concrete pump truck has become the important machine in modern construction industry. Study on the automatic control of the concrete pump truck arm system can effectively enhance the construction quality and the working efficiency of the pump truck. The arm system of the pump truck is a multi-body system with redundant freedom, strong nonlinear, coupled with rigid and flexible characters.The system is related to multi-body dynamics, control theory, kinematic reverse problem and hydrodynamics,etc.So it is of great theoretic value and real engineering significance to study the arm system of the concrete pump truck.In this article, the arm system of the concrete pump truck is considered as the study object. The application of multi-body dynamics,especially the flexible multi-body dynamics theory in the automatic pouring field of the concrete pump truck is mainly studied, and focus on the theoretic analysis.Much research has been done on the dynamics,control and simulation of the concrete pump truck arm system, and in detail the following contents are included.(1)The pump truck arm system is considered as a open-looped movement chain, consists of a series of poles connected with rotation fit. One end of the chain is fixed on the basement, the other end is free, so that the pouring movement is completed. Based on the multi-body rigid dynamic theory, the movement of the arms and the hydraulic cylinders are analyzed respectively, and the multi-body rigid dynamic equation of the arms is built with correlative theory of the analysis mechanics.After solution of the equation and with simulation, the influence to the arm end track from the rotation angles change of the rigid arms is studied.(2) With the extension of the pouring range, the arms are tending to be longer and lighter, which is necessary to consider the influence to the arm moving track from the flexible distortion. Based on the correlative theory of the flexible multi-body dynamics, all the arms are supposed as the equal-section Euler beams and the elastic distortion of any point on the arm is described by the style function. With the deduce formula, the Lagrange Equation and the virtual work theory, the flexible multi-body dynamic equation is built.And with the MEBFDAE to solute the equation and according to the simulation results, the influence to the arm end track from the flexible distortion is studied.Compared with the conclusion of the rigid arms, the advantages and disadvantages of the two modeling methods are analyzed.(3)The automation of pouring is studied. With the track programming and the optimization method, the dynamic converse problem of the arm end track is researched, so as to get the optimized rotation angle when the arm end reaches the expected pouring point, and the angle is considered as the expected value of the PD control rate.Combined with foregoing dynamic equation of the arm system, the dynamic control equations of the rigid and flexible arm systems are both built. With the numerical iterative arithmetic solving the equations and with simulation, the precision of the PD control and the change of the end track are both analyzed. This method is based on the accurate mathematic model of the system, in which the PD control rate is applied to the hydraulic driving force of the arms to independently close-loop control the hydraulic cylinder of each arm. And then it is extended to the whole control to the arms and the hydraulic driving system, with the study of the control precision and the real time character, the complete dynamic equation of the pump truck arm system is built.(4) The libration influence to the arms from the flow of the concrete slurry in the pump truck pipes. Because the concrete slurry is not the unitary fluidity, it can be predigested as the solid-liquid two phases flow. With the force analysis of the transport pipes and the slurry unit, the dynamic differential equation of the transport pipes is built. And with the correlative formulas of the mass, flex and the pressure of the solid-liquid two phases flow, the solid-liquid two phases flow equation of the concrete slurry is built.(5) With the ADAMS software, the rigid and flexible models of the pump truck arm system are both built. When building the rigid model, the structure segment is predigested and each arm is connected with the hydraulic cylinder by hinges. The flexible model is based on the rigid one.By dispersing the finite element of each arm, remaining the rigid characters at the hydraulic cylinders and the connection of each arm, with the same rotation angles as values in the foregoing numerical calculation, the movement situation of the arms, the change of the arms end track and the influence to the rotation angles from the flexible distortion are simulated and analyzed. The correction of the foregoing calculation is proved.Also the forces on each arm are simulated.