Predictively Adjustable Hydraulic Pressure Rails

1 . A robotic device comprising:

at least one sensor configured to generate data indicative of an environment in which the robotic device is operating;

a hydraulic drive system comprising:

a first pressure rail,

a second pressure rail, and

a hydraulic pump complex configured to provide pressurized hydraulic fluid at a fixed pressure to the first pressure rail and pressurized hydraulic fluid at an adjustable pressure to the second pressure rail;

a control system configured to vary the adjustable pressure provided by the hydraulic pump complex based on at least the data indicative of the environment in which the robotic device is operating; and

a switch valve complex comprising:

hydraulic fluid inputs, wherein the hydraulic fluid inputs comprise a first hydraulic fluid input coupled to the first pressure rail and a second hydraulic fluid input coupled to the second pressure rail,

a hydraulic fluid output, and

a hydraulic fluid switch that selectively connects one of the hydraulic fluid inputs to the hydraulic fluid output.

2 . The robotic device of claim 1 , further comprising:

a locomotion complex that moves the robotic device in a direction of locomotion; and

wherein the at least one sensor comprises a perception sensor configured to generate the data indicative of the environment in the direction of locomotion, and wherein the control system is configured to vary the adjustable pressure based on at least the data indicative of the environment in the direction of locomotion.

3 . The robotic device of claim 2 , wherein the locomotion complex comprises at least one leg including a first member, a second member, and a hydraulic actuator coupled between the first member and the second member, and wherein the hydraulic actuator comprises a port coupled to the hydraulic fluid output such that pressurized hydraulic fluid from the first pressure rail or from the second pressure rail flows to the hydraulic actuator.

4 . The robotic device of claim 3 , wherein the at least one sensor comprises a force sensor configured to detect slippage of the at least one leg, and wherein the control system is configured to increase the adjustable pressure based on the slippage of the at least one leg.

5 . The robotic device of claim 1 , further comprising:

a robotic manipulator; and

a force sensor configured to generate data indicative of a load on the robotic manipulator; and

wherein the control system is configured to vary the adjustable pressure in proportion to the load on the robotic manipulator.

6 . The robotic device of claim 1 , wherein the hydraulic drive system further comprises a third pressure rail, wherein the hydraulic pump complex is configured to provide pressurized hydraulic fluid at a second fixed pressure to the third pressure rail, wherein the second fixed pressure is greater than the first pressure, and wherein the adjustable pressure of the second pressure rail is adjustable from the first pressure to the second fixed pressure.

7 . The robotic device of claim 1 , wherein the hydraulic drive system further comprises a third pressure rail, wherein the hydraulic pump complex is configured to provide pressurized hydraulic fluid at a second fixed pressure to the third pressure rail, wherein the second fixed pressure is greater than the first pressure, and wherein the adjustable pressure of the second pressure rail is adjustable to pressures greater than the third pressure.

8 . The robotic device of claim 1 , wherein the switch valve complex further comprises a rotary switch valve having a spool and a sleeve, wherein rotation of the spool connects one or more of the hydraulic fluid inputs to the hydraulic fluid output.

9 . The robotic device of claim 1 , wherein the robotic device comprises a locomotion complex having four legs.

10 . The robotic device of claim 9 , wherein each leg comprises one or more hydraulic actuators, each hydraulic actuator comprising a port coupled to the hydraulic fluid output such that the pressurized hydraulic fluid from the first pressure rail or from the second pressure rail flows to a respective hydraulic actuator.

11 . A method comprising:

causing, by a control system, a robotic device to execute a gait by causing a hydraulic drive system to supply hydraulic fluid at a first pressure to one or more hydraulic actuators of the robotic device; and

while the robotic device executes the gait:

receiving sensor data indicative of a force acting on a leg of the robotic device;

based on the sensor data indicative of the force acting on the leg of the robotic device, determining that the sensor data indicates a slip of the leg of the robotic device; and

in response to determining that the sensor data indicates the slip of the leg, causing the hydraulic drive system to adjust hydraulic pressure of the supplied hydraulic fluid from the first pressure to a second pressure to counteract the slip of the leg.

12 . The method of claim 11 , wherein the second pressure is greater than the first pressure.

13 . The method of claim 11 , wherein:

the hydraulic drive system comprises a fixed pressure rail and an adjustable pressure rail; and

causing the hydraulic drive system to adjust the hydraulic pressure of the supplied hydraulic fluid from the first pressure to the second pressure comprises switching from supplying hydraulic fluid at the first pressure from the fixed pressure rail to supplying hydraulic fluid at the second pressure from the adjustable pressure rail.

14 . The method of claim 11 , wherein:

the hydraulic drive system comprises an adjustable pressure rail supplying hydraulic fluid at the first pressure; and

causing the hydraulic drive system to adjust the hydraulic pressure of the supplied hydraulic fluid from the first pressure to the second pressure comprises increasing the hydraulic pressure of the adjustable pressure rail from the first pressure to the second pressure.

15 . The method of claim 14 , wherein increasing the hydraulic pressure of the adjustable pressure rail from the first pressure to the second pressure further comprises opening a throttle of a metering valve coupled to the adjustable pressure rail from a flow restricted state.

16 . The method of claim 11 , wherein determining that the sensor data indicates the slip of the leg of the robotic device comprises determining that the sensor data indicates a sudden decrease in the force acting on the leg of the robotic device.

17 . The method of claim 11 , wherein:

the gait comprises a leg movement pattern with a corresponding leg loading pattern for the force acting on the leg; and

determining that the sensor data indicates the slip of the leg of the robotic device comprises determining that the sensor data indicates that the force acting on the leg deviates from the corresponding leg loading pattern.

18 . The method of claim 11 , further comprising:

determining that the sensor data indicates another slip of the leg of the robotic device after adjusting the hydraulic pressure of the supplied hydraulic fluid to the second pressure; and

in response to determining that the sensor data indicates another slip of the leg, causing the hydraulic drive system to adjust the hydraulic pressure of the supplied hydraulic fluid from the second pressure to a third pressure, the third pressure greater than the second pressure.

19 . The method of claim 18 , wherein:

a fixed pressure rail of the hydraulic drive system supplies the hydraulic pressure of at least one of the first pressure, the second pressure, or the third pressure; and

an adjustable pressure rail of the hydraulic drive system supplies the hydraulic pressure of the other of the first pressure, the second pressure, or the third pressure that is not supplied by the fixed pressure rail.

20 . The method of claim 11 , wherein the robotic device comprises four legs.