| For hydraulic systems with multiple loads and large differences in load pressure and flow rates,a conventional hydraulic power unit typically consists of a single hydraulic pump,a relief valve,and multiple reduction valves and is configured by the maximum pressure and maximum flow rate.When multiple loads are running parallel,the efficiency will be very low,with large throttle loss and overflow loss.Aiming at this problem,an energy-saving hydraulic power unit for multi-load has been proposed.The power unit consists of a number of low-power servo motor direct drive hydraulic pump and safety valve,one-way valve and other components.It provides different pressure levels and flow levels of hydraulic oils according to the load requirements of different actuators to form real-time,efficient and intelligent pressure fluid coordination and distribution.Therefore,it can ensure that the hydraulic pump output power close to the load power consumption,thereby reducing the throttle loss and avoiding excessive pressure and flow.And main research work is present as follows:Firstly,the research on hydraulic energy-saving technology at home and abroad is done;the principle and similarities and differences of different energy-saving technologies is analyzed,which provides ideas and guidance for designing new energy-saving power units.Secondly,a new type of hydraulic energy-saving power unit is proposed,and the energy conversion efficiency of the traditional multi-load hydraulic system and the multi-load hydraulic system using the new hydraulic power unit are respectively calculated,and the essence of energy saving is explained.At the same time,the design principles of the new hydraulic power unit are introduced,which means that different working conditions should apply different design methods.Then the mathematical modeling of the single-pump single-cylinder hydraulic direct drive system is carried out,and AMESim-Simulink joint simulation is carried out to track different input signals separately.At the same time,for the open-loop control of hydraulic cylinders without displacement feedback,which often occurs in engineering practice,fuzzy adaptive control is applied to pressure feedback to eliminate speed oscillation and obtain better control effect.The multi-load hydraulic system is then analyzed.The hydraulic system of the single-pump and two-cylinder is mathematically modeled,and the nonlinear state space of two inputs and two outputs is obtained.The Falbwolovich method is used for decoupling and software simulation.For the switching problem of two control modes(pump control,valve control),the control method of switching control is applied,and in the process of speed tracking control,excessive speed error is eliminated,and better control effect is obtained.For the problem of multi-hydraulic pump switching,the oil pump and the pressure are matched in advance to realize the smooth switching of the oil supply hydraulic pump,so that the new energy-saving power unit can be better applied to the hydraulic load with variable flow or pressure.Finally,in order to verify the reliability of the control method,a doublepump and multi-load test bench was designed and manufactured,and the experimental verification of the control method under various working conditions was carried out. |
