Excavator With New Electro-hydraulic Proportional Valve Control Strategy

As the key part on the excavator, the multitandem valve's performance and function directly determine the performance and function of the excavator. Most of the multitandem valves used on the excavator in domestic market have two characteristics. The first characteristic is non-electronic-control, that means the operation of multitandem valve is done via directly controlling the spool by hand. The second characteristic is single spool control mode, that means the oil which flow in and out the actuator is controlled by one single spool. These two characteristics make the excavator hard to fulfill large-scale energy saving, and other performance like remote control task and excavator group cooperation task. The paper has done some research on a new type of electronic-hydraulic proportional multitandem valve based on independent control of actuator ports, which is a latest overseas production used on the excavator. For adopting a creative structure design and integrating the electronic technology, it can provid the excavator's large-scale energy saving and intelligence operation like remote control with premise condition. Based on establishing the mathematical model of the valve, the paper did research on its control strategy, which could provide instruction for the valve's designing and production in home.Combined the excavator, analyzed the structure construction, work principle of the valve and the relevant hardware and software construction,made a comparison research on the control mode of the hydraulic actuator between the valve and the traditional change valve, pointed out that the valve is more flexible than the traditional change valve on controlling the hydraulic loop.Based on hydrodynamics and classical control theory, established the mathematical model of the valve, pointed out the difference between the transfer function of pilot valve to main valve and the transfer function of classical valve control symmetry cylinder, analyzed the dynamic characteristic of the valve, discussed the main parameters that influence the dynamic characteristic of the valve. On the basis of this, put forward the opinion that use normal PID controller to control the displacement of the main spool, the simulation result show that the adaptability of PID control is not good and hard to meet the control demands.Introduced fuzzy control strategy, designed a fuzzy controller.The simulation result of normal fuzzy control strategy show that it is feasible to use fuzzy control strategy to control the displacement of the main spool, and the dynamic response quality of the system is fairly good,but there is a big steady state error.The fuzzy control strategy based on modifying fuzzy rules can improve the dynamic response quality of the system, but also can not eliminate steady state error. The Fuzzy-PID dual-mode fuzzy control strategy combined the virtue of fuzzy control and PID control, the system not only has a good dynamic response quality, but also eliminate steady state error thoroughly. As the bucket hydraulic loop for representation, established a Amesim/Matlab union simulation model of electronic-hydraulic proportional valve and the relevant excavator hydraulic system. Through testing the piston chamber pressure and the rod chamber pressure of the bucket actuator and comparing it to the simulation result, testified the correctness of the model, meanwhile, it also indirectly proved that Fuzzy-PID dual mode fuzzy control strategy can be used on this valve.