Patent ID: 9638216
Date: 2017-05-02
CPC Classifications: B25J,B60Y,F15B,G05D

Claim:
1. A method comprising: based on a load on one or more hydraulic actuators of a hydraulic drive system of a robotic device, determining, by a control system of the robotic device, an actuation pressure to actuate the one or more hydraulic actuators; based on the determined actuation pressure, selecting, by the control system, a pressure rail from among a set of pressure rails at respective pressures, wherein the selected pressure rail supplies pressurized hydraulic fluid at a supply pressure, and wherein the supply pressure is, among the respective pressures, at a lowest pressure that exceeds the determined actuation pressure; causing, by the control system, one or more valves to connect the selected pressure rail to a metering valve such that hydraulic fluid at approximately the supply pressure flows from the selected pressure rail to the metering valve; causing, by the control system, the hydraulic drive system to operate in a discrete mode in which the metering valve opens such that hydraulic fluid flows from the selected pressure rail through the metering valve to the one or more hydraulic actuators at approximately the supply pressure; receiving, by the control system, from one or more sensors on the robotic device, data indicative of one or more physical features of an environment in which the robotic device is operating; and based on the data indicative of the one or more physical features of the environment, causing, by the control system, the hydraulic drive system to operate in a continuous mode in which the metering valve throttles the hydraulic fluid such that the supply pressure is reduced to approximately the determined actuation pressure.