Pressure overshooting prevention system for electronic hydraulic pump in hydraulic system

Abstract

The present disclosure relates to a pressure overshooting prevention system for an electronic hydraulic pump in a hydraulic system, in which a flow rate command is added (+), a discharge flow rate is subtracted (−), a displacement flow rate (Delta Q) is calculated, a first pressure command corresponding to the displacement flow rate (Delta Q) is generated, a working fluid pressure value corresponding to the discharge flow rate is generated, a limit pressure command is generated to limit an increasing gradient of the working fluid pressure value, a stall is determined based on a first rate of change of the flow rate command, and a second rate of change of the discharge flow rate, and the limit pressure command is set to a second pressure command when the stall is determined, and a small value of the first pressure command and the second pressure command is selected as a final pressure command so as to control an electronic proportional control valve, thereby reducing overshooting of the electronic hydraulic pump.

1 . A pressure overshooting prevention system for an electronic hydraulic pump in a hydraulic system, comprising:
 a flow rate command calculating unit which adds (+) a flow rate command corresponding to required pressure, subtracts (−) a discharge flow rate discharged from an electronic hydraulic pump, and calculates a displacement flow rate;   a flow rate control unit which generates a first pressure command corresponding to the displacement flow rate;   a stall determining unit which determines a stall based on a first rate of change of the flow rate command, and a second rate of change of the discharge flow rate;   a flow rate pressure generating unit which generates a working fluid pressure value corresponding to the discharge flow rate;   a gradient limiting unit which generates a limit pressure command so as to limit an increasing gradient of the working fluid pressure value;   a selecting unit which sets the limit pressure command to a second pressure command when a stall is determined by the stall determining unit; and   a minimum pressure setting unit which selects a small value of the first pressure command and the second pressure command as a final pressure command so as to control an electronic proportional control valve.   
     
     
         2 . The pressure overshooting prevention system of  claim 1 , wherein the stall determining unit determines the stall when the second rate of change is greater than the first rate of change. 
     
     
         3 . The pressure overshooting prevention system of  claim 1 , wherein in the limit pressure command, a second pressure command gradient after a time point when the stall is determined is smaller than a first pressure command gradient before the time point when the stall is determined. 
     
     
         4 . The pressure overshooting prevention system of  claim 1 , wherein the selecting unit sets a system pressure command to the second pressure command when the stall determining unit determines that the stall is released.