Variable Universe Fuzzy Controller for an Independent Metering System of Construction Machinery

Abstract

As a new type of hydraulic system, the independent valve control system (IMCS) has higher flexibility compared with the traditional four-side slide valve control system. The independent metering control system (IMCS) is divided into four quadrant modes, based on the speed and load of the actuator. The traditional control methods always use a discrete control strategy to realize the switching between different modes based on mode recognition. However, the spool signals frequently switch, and the actuator operating pressure and speed are not stable when the IMCS is switched between different modes. To solve the above problems, this paper proposes a continuous control strategy for the IMCS. Based on the fuzzy control principle, the variable universe fuzzy controller (VUFC) was designed. The controller contains 49 fuzzy rules, and the output of the controller at any time is calculated by the weighted sum of several fuzzy rules. The VUFC divides the system into 49 rules, which are activated by multiple modes at any time to achieve a smooth transition between different modes. The VUFC was verified in a 37 ton excavator model and compared with the traditional independent metering meter-out (IM_MO) control strategy. The results showed that the VUFC significantly improved the frequent switching of the spool signals, and the running speed and pressure stability of the hydraulic cylinder were significantly improved. At the same time, the response speed of the hydraulic cylinder became faster at the start of the system. The VUFC can realize the continuous control of the IMCS and improve the operating performance of excavators.