Research On Control Method Of Load For Truck Crane Hoisting Mechanism In Over-running Load Condition

It’s the general trend that the development of crane’s industry in truck crane will be toward great-tonnage and super-tonnage, at one time, closed hydraulic system has extended in the field of truck crane’s winch step by step, because of its excellence at security and energy-saving. At the exceed-load status, the motor of the closed winch become driving element but not executing element, therefore the rotate speed of engine will be "runaway" Plunging load power into the closed hydraulic system of winch to guarantee the rate of load more than zero, sequentially to avoid "runaway". However, if plunged load power is not enough, it will lead to truck crane being lack of security because of the fluctuation of the engine’s load rate; Contrarily, it will cause unnecessarily loss of engine power.The key of this thesis is to constant control the load power and to guarantee the thermostatic control the load power of the engine in the best rate, then reach the request of truck crane’s security and energy-saving. Base on the theory that the hydraulic system’s power equals to the product of pressure and flow, we can realize the thermostatic control of hydraulic system’s power by thermostatic control of its pressure and flow.In this thesis, the main work is as follows:firstly, point out the closed loop control strategy of plunging-load loop’s pressure and flow as to dispel the instability of engine’s power which is caused by the undulation of pressure and flow which is leaded by wind load’s size and the change of the temperature and so on. And then, Through the establishment of dynamics equations of hydraulic components to establish the dynamics equation of load in the hydraulic control system and to establish the simulation model of a large-tonnage truck crane’s plunging load loop by the use of computer simulation tools, and through these dynamic analysis to study the dynamic characteristics of the two, Ultimately determine the feasibility and superiority of the closed-loop control strategy in the plunging closed hydraulic control system. Finally, experimental study in a large-tonnage truck crane products closed winch system, through repeated experiments, hanging to the engine fuel consumption and vehicle stability as an indicator in the upload process, in order to obtain the optimal load master of engine at different speeds from the various tonnage weight status, and verify feasibility and superiority of the closed-loop control strategy at the plunging load status in the hydraulic control system.