| Truck crane is a construction machinery widely used in various fields of national economy,is an indispensable equipment in construction,its operating system mainly includes four subsystems such as slewing,winch,telescoping,luffing,etc.,of which the luffing system is a variable load system,the system has high requirements for smooth operation.At present,domestic truck cranes generally have poor uniformity of speed when luffing,easy to produce impact jitter and other problems.In order to improve the performance of the luffing truck crane,this paper takes a domestic enterprise a type of truck crane as the object of research,using a combination of theoretical calculations,simulation analysis and experimental research method to study the key factors affecting the stability of the luffing truck crane,according to the results of the study and analysis of optimization improvement strategies to improve the uniformity of the crane luffing and eliminate the impact of the truck crane jitter and.The main research content of the thesis is as follows.(1)Based on the Lagrangian method to establish a crane load swing model,according to the law of motion of the crane load swing angle simplified and established the dynamics of the luffing mechanism model.(1)Based on the Lagrangian method,the crane load swing model is established,and the dynamics model of the luffing mechanism is simplified and established according to the law of crane load swing angle motion.(2)The simulation model of the luffing hydraulic system is established by means of system-level and component-level accurate modeling,and the correctness of the simulation results is verified experimentally.The influence of the load-sensitive characteristics of the pump control system on the luffing process and the influence of the flow saturation characteristics of the luffing balance valve on the luffing process are revealed.The influence of the valve port structure parameters on the flow-differential pressure characteristics of the balancing valve is further studied to lay the foundation for the optimal control of the amplitude uniformity of the variable amplitude system.(3)Through the AMESim/ADAMS joint simulation platform,a joint machine-hydraulic simulation model of the truck crane is established to reveal the pressure,flow and luffing speed variation law of the truck crane luffing hydraulic system under the machine-hydraulic coupling;the comprehensive dynamic performance test of the truck crane luffing process is conducted to verify the accuracy of the numerical simulation model.On this basis,the crane luffing uniformity under different working conditions is studied,and the study shows that the luffing large angle position when the cylinder force is small and the luffing system late into the flow saturation state will lead to poor uniformity of the luffing process,and will cause the system shock jitter.(4)Genetic algorithm is used to solve the optimal structural parameters of the variable-amplitude balancing valve in a certain range,which achieves the goal of entering the flow saturation state earlier and improves the performance of the balancing valve against shock jitter.The feedback compensation control strategy of the pilot control pressure of the balancing valve and the feedback compensation control strategy of the power drop of the variable amplitude cylinder are designed according to the conditions of uniform amplitude and the load change law in the process of amplitude change.The simulation results show that the optimized luffing system can effectively reduce the shock jitter,and the uniformity of the falling speed is improved by 91.43%,77.56% and 60 %respectively. |
PDF Full Text Request