Patent ID: 6938471

Claim:
A method of measuring a pressure of a hydraulic fluid supplied from a hydraulic drive device to an operation device, wherein the hydraulic drive device comprises a pressure generator arranged and constructed to pressurize the hydraulic fluid, an accumulator arranged and constructed to receive the supply of the pressurized hydraulic fluid from the pressure generator in order to accumulate the pressure of the pressurized hydraulic fluid, and a pressure control unit arranged and constructed to receive the pressurized hydraulic fluid from the accumulator and to control the pressure of the hydraulic fluid to be supplied to the operation device in response to operation of an external device, comprising: measuring a first pressure (Pm) of the hydraulic fluid within a first flow path connecting the pressure control unit and the operation device, measuring a second pressure (Pa) of the hydraulic fluid within a second flow path connecting the accumulator and the pressure control unit, determining a stabilization time (T) that is the time when an absolute value of a pressure gradient per unit time of the second pressure becomes smaller than a predetermined value, and determining a third pressure (Pw) of the hydraulic fluid supplied to the operation device based on the first pressure that is measured at the stabilization time (T) or at a time immediately after the stabilization time (T).