Braking and regeneration control in a legged robot

A method comprising:

• providing, by a controller of a robot, a first signal to a valve system, wherein the robot includes a hydraulic actuator cylinder controlling motion of a member of the robot, the hydraulic actuator cylinder comprising a piston, a first chamber, and a second chamber, wherein the valve system is configured to control hydraulic fluid flow between a supply line of pressurized hydraulic fluid, the first and second chambers, and a return line, the valve system configured to couple the first chamber to the supply line of pressurized fluid and couple the second chamber to the return line to move the piston in a forward direction, wherein the first signal to the valve system causes the piston to follow a desired trajectory, the desired trajectory indicating movement by the piston in the forward direction from a first position until the piston stops at a second position, then move in a reverse direction;
• when the piston is between the first position and the second position while moving in the forward direction:
• receiving sensor information from a sensor system indicative of a speed of the piston and a pressure level in the second chamber;
• and
• providing a second signal to the valve system based on the speed of the piston and the pressure level in the second chamber, the second signal causing the piston to override the desired trajectory and stop at a third position disposed between the first position and the second position;
• and
• prior to when the piston would have reached the third position if the piston was moving in the reverse direction according to the desired trajectory, providing a third signal to the valve system to resume moving the piston in the reverse direction based on the desired trajectory.

A non-transitory computer readable medium having stored therein instructions that, in response to execution by a controller of a robot, cause the controller to perform operations comprising:

• providing a first signal to a valve system, wherein the robot includes a hydraulic actuator cylinder controlling motion of a member of the robot, the hydraulic actuator cylinder comprising a piston, a first chamber, and a second chamber, wherein the valve system is configured to control hydraulic fluid flow between a supply line of pressurized hydraulic fluid, the first and second chambers, and a return line, the valve system configured to couple the first chamber to the supply line of pressurized fluid and couple the second chamber to the return line to move the piston in a forward direction, wherein the first signal to the valve system causes the piston to follow a desired trajectory, the desired trajectory indicating movement by the piston in the forward direction from a first position until the piston stops at a second position, then move in a reverse direction;
• when the piston is between the first position and the second position while moving in the forward direction:
• receiving sensor information from a sensor system indicative of a speed of the piston and a pressure level in the second chamber;
• and
• providing a second signal to the valve system based on the speed of the piston and the pressure level in the second chamber, the second signal causing the piston to override the desired trajectory and stop at a third position disposed between the first position and the second position;
• and
• prior to when the piston would have reached the third position if the piston was moving in the reverse direction according to the desired trajectory, providing a third signal to the valve system to resume moving the piston in the reverse direction based on the desired trajectory.