Patent ID: 7870726
Filing Date: 2011-01-18
Classification: B64C,F15B,Y02T

Abstract:
1. A hydraulic control system, comprising: a hydraulic actuator having a cylinder and piston assembly; a first and second fluid line coupled to the hydraulic actuator; a high pressure fluid line; a low pressure fluid line; a central pressure source coupled to the high pressure fluid line to place high pressure on the first and second fluid lines; a servo valve positioned between the central pressure source and the hydraulic actuator and being controllable to selectively connect the first and second fluid lines to the high pressure fluid line and the low pressure fluid line to control movement of the hydraulic actuator; a pressure sensor adjacent the servo valve and coupled to the high pressure fluid line to sense the pressure in the high pressure fluid line adjacent the servo valve, upstream of the servo valve, the pressure sensor outputting a signal indicative of the pressure in the high pressure fluid line; a local pump adjacent to the servo valve, the local pump being coupled to the high pressure fluid line upstream of the servo valve to increase the local pressure in the high pressure fluid line upon being actuated; an electric motor coupled to the local pump to actuate the local pump; a first check valve in the high pressure fluid line adjacent the servo valve, the first check valve preventing the high pressure fluid from entering from the local pump to the central pressure source; a second check valve adjacent to the local pump, the second check valve preventing the high pressure fluid from entering from the central pressure source to the local pump; and a controller which performs (i) a sequential-power mode in which, when a signal output from the pressure sensor is indicative of a pressure lower than a selected value, pressure supply to the hydraulic fluid line is maintained by placing pressure from the local pump to the high pressure fluid line by activating the electric motor and (ii) a parallel-power mode in which, when it is required to switch the pressure source quicker than in the sequential-power mode, the electric motor is activated in advance for a failure of the central pressure source so that the pressure from the central pressure source and the pressure from the local pump are simultaneously supplied to the high pressure fluid liner, wherein, the controller includes: a central controller which outputs a signal based on whether the sequential-power mode is activated and whether the parallel-power mode is activated; and a local controller which activates or stops the electric motor when receiving the signal from the central controller.