Construction machine and control method thereof

1 . A construction machine, which comprises a boom, the construction machine comprising:

a boom cylinder configured to move the boom upward or downward and comprises a head side and a rod side;

a boom regeneration valve configured to control a flow rate of a working fluid discharged from a head side of the boom cylinder;

an operating device configured to generate an operating signal for operating the boom;

an accumulator configured to store the working fluid discharged from the boom cylinder;

a regeneration motor configured to produce renewable energy by performing a regenerative operation by using the working fluid discharged from the boom cylinder or the working fluid discharged from the accumulator; and

a control device configured to correct an opening area of the boom regeneration valve on the basis of pressure of the accumulator when the boom descends,

wherein the control device is configured to:

determine a target speed of the boom corresponding to the operating signal of the operating device;

calculate a target passage flow rate at which the working fluid needs to pass through the boom regeneration valve to achieve the target speed; and

calculate the opening area of the boom regeneration valve required to pass the calculated target passage flow rate, and, once the opening area is calculated, transmit a control command to the boom regeneration valve.

2 . The construction machine of claim 1 , wherein the control device is configured to determine a control instruction to be transferred to the boom regeneration valve so that the opening area of the boom regeneration valve increases as the pressure of the accumulator increases.

3 . The construction machine of claim 1 , further comprising:

an accumulator pressure sensor configured to measure the pressure of the accumulator.

4 . The construction machine of claim 1 , further comprising:

a control valve configured to control a supply of the working fluid to the boom cylinder;

a first boom hydraulic line configured to connect the control valve and the head side of the boom cylinder;

a second boom hydraulic line configured to connect the control valve and the rod side of the boom cylinder;

a recirculation line branching off from the first boom hydraulic line and connected to the second boom hydraulic line; and

a regeneration line branching off from the recirculation line and connected to the regeneration motor.

5 . The construction machine of claim 4 , wherein the boom regeneration valve comprises:

a first spool configured to adjust a passage flow rate of the regeneration line; and

a second spool configured to adjust a passage flow rate of the recirculation line, and

wherein the control device is configured to adjust an opening area of the first or second spool.

6 . The construction machine of claim 4 , further comprising:

a working fluid storage line branching off from the recirculation line and connected to the accumulator; and

an accumulator valve installed in the working fluid storage line and configured to control an inflow of the working fluid to the accumulator and an outflow of the working fluid from the accumulator.

7 . The construction machine of claim 1 , further comprising:

a main pump configured to supply the working fluid to the control valve; and

an engine connected to the main pump and the regeneration motor.

8 . A method of controlling a construction machine comprising a boom cylinder configured to operate a boom, the method comprising:

receiving an operating signal for operating the boom;

receiving information on pressure of an accumulator configured to store a working fluid discharged from the boom cylinder;

calculating a target passage flow rate of the working fluid that needs to be discharged from the boom cylinder in response to the operating signal; and

correcting the target passage flow rate on the basis of the pressure of the accumulator,

wherein the method further comprising:

determining a target speed of the boom corresponding to the operating signal; and

calculating an opening area of a boom regeneration valve required to pass the calculated target passage flow rate, and, once the opening area is calculated, transmitting a control command to the boom regeneration valve, and

wherein the target passage flow rate is calculated to achieve the target speed.

9 . The method of claim 8 , wherein the target passage flow rate is one of or both a first target passage flow rate at which the working fluid is discharged to the accumulator from a head side of the boom cylinder and a second target passage flow rate at which the working fluid is discharged to a rod side of the boom cylinder from the head side of the boom cylinder.