| Hydraulic drive units mainly include motor and pump.As a method to improve the energy efficiency of the drive units of hydraulic system,frequency conversion technology has a great deterrent effect on the energy matching loss of hydraulic system.However,due to the traditional frequency conversion technology for hydraulic system only consider the drive unit as a whole to match the load well,while ignore the effect to energy-saving for the energy conversion efficiency of motor and pump respectively,energy-saving effect is poor.In this paper,an energy-saving method for improving drive units overall energy efficiency was studied for a hydraulic system.Then take the energy-saving method into further explore combined with variable frequency asynchronous motor driving variable piston pump.Firstly,according to the characteristics of the hydraulic machine,the energy flow characteristics and dissipation characteristics of the motor and the hydraulic pump are analyzed in hydraulic drive units.In the single working condition,the energy efficiency models of the induction motor and the plunger pump are established respectively,and clarify the main influencing factors of the energy efficiency for the motor and the hydraulic pump.Then,based on the energy efficiency of the motor and piston pump,the coupling relationship between the motor and the hydraulic pump under single working condition is studied during the forming process for a hydraulic press.Then,the energy matching model about drive unit is established and the optimization method of the whole energy efficiency for the drive unit is proposed,to achieve a best matching effect for the drive unit matching load.In the process of induction motor variable frequency regulation.In order to solve the problem of precise control for the parameters in drive unit energy matching method,the linear regression model is used to establish a more accurate mapping relationship between the actual output speed and frequency of the asynchronous motor based on the quantification for the slip.And the validity of the model is verified by experiments.Finally,based on the modeling method of power bond graph,the dynamic characteristic model of driving unit based on energy matching method is established.Then study the output characteristic of the pressure under step response by software simulation.The results show its dynamic performance is excellent.Thus,we can realize a double-excellent hydraulic system with high energy efficiency and good response characteristics. |
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