Abstract: In some applications, a piston of a hydraulic actuator may move at high speeds, and large undesired forces may be generated if the piston reaches an end-stop of the hydraulic actuator at a high speed. The undesired forces may, for example, cause mechanical damage in the hydraulic actuator. A controller may receive information indicative of the piston reaching a first position at a first threshold distance from the end-stop, and, in response, may modify a signal to a valve assembly controlling flow of hydraulic fluid to and from the hydraulic actuator. Further, the controller may receive information indicative of the piston reaching a second position at a second threshold distance closer to the end-stop of the hydraulic actuator, and, in response, the controller may further modify the signal to the valve assembly so as to apply a force on the piston in a away from the end-stop.

Abstract: A method for estimating a ground plane includes receiving a pose of a robotic device with respect to a gravity aligned reference frame, receiving one or more locations of one or more corresponding contact points between the robotic device and a ground surface, and determining a ground plane estimation of the ground surface based on the orientation of the robotic device with respect to the gravity aligned reference frame and the one or more locations of one or more corresponding contact points between the robotic device and the ground surface. The ground plane estimation includes a ground surface contour approximation. The method further includes determining a distance between a body of the robotic device and the determined ground plane estimation and causing adjustment of the pose of the robotic device with respect to the ground surface based on the determined distance and the determined ground plane estimation.

Abstract: An example implementation includes (i) receiving sensor data that indicates topographical features of an environment in which a robotic device is operating, (ii) processing the sensor data into a topographical map that includes a two-dimensional matrix of discrete cells, the discrete cells indicating sample heights of respective portions of the environment, (iii) determining, for a first foot of the robotic device, a first step path extending from a first lift-off location to a first touch-down location, (iv) identifying, within the topographical map, a first scan patch of cells that encompass the first step path, (v) determining a first high point among the first scan patch of cells; and (vi) during the first step, directing the robotic device to lift the first foot to a first swing height that is higher than the determined first high point.

Abstract: In some applications, a piston of a hydraulic actuator may move at high speeds, and large undesired forces may be generated if the piston reaches an end-stop of the hydraulic actuator at a high speed. The undesired forces may, for example, cause mechanical damage in the hydraulic actuator. A controller may receive information indicative of the piston reaching a first position at a first threshold distance from the end-stop, and, in response, may modify a signal to a valve assembly controlling flow of hydraulic fluid to and from the hydraulic actuator. Further, the controller may receive information indicative of the piston reaching a second position at a second threshold distance closer to the end-stop of the hydraulic actuator, and, in response, the controller may further modify the signal to the valve assembly so as to apply a force on the piston in a away from the end-stop.

Abstract: A method for estimating a ground plane includes receiving a pose of a robotic device with respect to a gravity aligned reference frame, receiving one or more locations of one or more corresponding contact points between the robotic device and a ground surface, and determining a ground plane estimation of the ground surface based on the orientation of the robotic device with respect to the gravity aligned reference frame and the one or more locations of one or more corresponding contact points between the robotic device and the ground surface. The ground plane estimation includes a ground surface contour approximation. The method further includes determining a distance between a body of the robotic device and the determined ground plane estimation and causing adjustment of the pose of the robotic device with respect to the ground surface based on the determined distance and the determined ground plane estimation.

Abstract: An example method may include i) detecting a disturbance to a gait of a robot, where the gait includes a swing state and a step down state, the swing state including a target swing trajectory for a foot of the robot, and where the target swing trajectory includes a beginning and an end; and ii) based on the detected disturbance, causing the foot of the robot to enter the step down state before the foot reaches the end of the target swing trajectory.

Abstract: A control system of a robotic device may receive sensor data indicating at least one deviation from a nominal operating parameter of the robotic device, where the robotic device includes articulable legs that include respective actuators, and where one or more strokes of the actuators cause the articulable legs to articulate. Based on the received sensor data, the control system may determine that the at least one deviation exceeds a pre-determined threshold. In response to determining that the at least one deviation exceeds the pre-determined threshold, the control system may provide instructions for centering the one or more strokes at approximately a mid-point of extension of the actuators, and reducing a stroke length of the one or more strokes of the actuators.

Abstract: A robot system includes: an upper body section including one or more end-effectors; a lower body section including one or more legs; and an intermediate body section coupling the upper and lower body sections. An upper body control system operates at least one of the end-effectors. The intermediate body section experiences a first intermediate body linear force and/or moment based on an end-effector force acting on the at least one end-effector. A lower body control system operates the one or more legs. The one or more legs experience respective surface reaction forces. The intermediate body section experiences a second intermediate body linear force and/or moment based on the surface reaction forces. The lower body control system operates the one or more legs so that the second intermediate body linear force balances the first intermediate linear force and the second intermediate body moment balances the first intermediate body moment.

Abstract: An example method may include i) detecting a disturbance to a gait of a robot, where the gait includes a swing state and a step down state, the swing state including a target swing trajectory for a foot of the robot, and where the target swing trajectory includes a beginning and an end; and ii) based on the detected disturbance, causing the foot of the robot to enter the step down state before the foot reaches the end of the target swing trajectory.

Abstract: A method of operating a robot includes driving a robot to approach a reach point, extending a manipulator arm forward of the reach point, and maintaining a drive wheel and a center of mass of the robot rearward of the reach point by moving a counter-balance body relative to an inverted pendulum body while extending the manipulator arm forward of the reach point. The robot includes the inverted pendulum body, the counter-balance body deposed on the inverted pendulum body, the manipulator arm connected to the inverted pendulum body, at least one leg having a first end prismatically coupled to the inverted pendulum body, and the drive wheel rotatably coupled to a second end of the at least one leg.

Abstract: A robot includes an inverted pendulum body having first and second end portions, a counter-balance body disposed on the inverted pendulum body and configured to move relative to the inverted pendulum body, at least one leg having first and second ends, and a drive wheel rotatably coupled to the second end of the at least one leg. The first end of the at least one leg is prismatically coupled to the second end portion of the inverted pendulum body.

Abstract: A robot system includes: an upper body section including one or more end-effectors; a lower body section including one or more legs; and an intermediate body section coupling the upper and lower body sections. An upper body control system operates at least one of the end-effectors. The intermediate body section experiences a first intermediate body linear force and/or moment based on an end-effector force acting on the at least one end-effector. A lower body control system operates the one or more legs. The one or more legs experience respective surface reaction forces. The intermediate body section experiences a second intermediate body linear force and/or moment based on the surface reaction forces. The lower body control system operates the one or more legs so that the second intermediate body linear force balances the first intermediate linear force and the second intermediate body moment balances the first intermediate body moment.

Abstract: An example method may include i) determining a first distance between a pair of feet of a robot at a first time, where the pair of feet is in contact with a ground surface; ii) determining a second distance between the pair of feet of the robot at a second time, where the pair of feet remains in contact with the ground surface from the first time to the second time; iii) comparing a difference between the determined first and second distances to a threshold difference; iv) determining that the difference between determined first and second distances exceeds the threshold difference; and v) based on the determination that the difference between the determined first and second distances exceeds the threshold difference, causing the robot to react.

Abstract: Example methods and devices for touch-down detection for a robotic device are described herein. In an example embodiment, a computing system may receive a force signal due to a force experienced at a limb of a robotic device. The system may receive an output signal from a sensor of the end component of the limb. Responsive to the received signals, the system may determine whether the force signal satisfies a first threshold and determine whether the output signal satisfies a second threshold. Based on at least one of the force signal satisfying the first threshold or the output signal satisfying the second threshold, the system of the robotic device may provide a touch-down output indicating touch-down of the end component of the limb with a portion of an environment.

Abstract: An example method may include determining a requested yaw for a body of a robot, where the biped robot comprises a foot coupled to the body via a leg. The robot may then detect, via one or more sensors, a yaw rotation of the body with respect to a ground surface, where the foot is in contact with the ground surface. Based on the detected yaw rotation of the body, the robot may determine a measured yaw for the body. The robot may also determine a target yaw for the body, where the target yaw for the body is between the measured yaw for the body and the requested yaw for the body. The robot may then cause the foot to rotate the body to the target yaw for the body.

Abstract: Example methods and devices for touch-down detection for a robotic device are described herein. In an example embodiment, a computing system may receive a force signal due to a force experienced at a limb of a robotic device. The system may receive an output signal from a sensor of the end component of the limb. Responsive to the received signals, the system may determine whether the force signal satisfies a first threshold and determine whether the output signal satisfies a second threshold. Based on at least one of the force signal satisfying the first threshold or the output signal satisfying the second threshold, the system of the robotic device may provide a touch-down output indicating touch-down of the end component of the limb with a portion of an environment.

Abstract: A robot system includes: an upper body section including one or more end-effectors; a lower body section including one or more legs; and an intermediate body section coupling the upper and lower body sections. An upper body control system operates at least one of the end-effectors. The intermediate body section experiences a first intermediate body linear force and/or moment based on an end-effector force acting on the at least one end-effector. A lower body control system operates the one or more legs. The one or more legs experience respective surface reaction forces. The intermediate body section experiences a second intermediate body linear force and/or moment based on the surface reaction forces. The lower body control system operates the one or more legs so that the second intermediate body linear force balances the first intermediate linear force and the second intermediate body moment balances the first intermediate body moment.

Abstract: An example implementation for avoiding leg collisions may involve a biped robot reducing a three-dimensional system to a two-dimensional projection of the biped robot's feet. An example biped robot may determine a touchdown location for a swing foot. The biped robot may determine lateral positions of the touchdown location and the swing foot, each relative to a stance foot. Based on one or more of the determined lateral positions of the touchdown location and the swing foot, each relative to the stance foot, the biped robot may determine an intermediate swing point for the swing foot that is not on a line defined by the swing foot and the touchdown location. The biped robot may further cause the swing foot to move to the intermediate swing point, and then cause the swing foot to move to the touchdown location.

Abstract: Examples method and devices for automatic gait transition are described herein. In an example embodiment, a computing system may identify gaits for the robotic device to perform in response to receiving an input for the robotic device to move at a velocity. The system may determine criteria for selecting a gait from the identified gaits for the robotic device to perform based on sensor data of the environment (e.g., slope and terrain) and based on the state of the robotic device. The system may modify the set of criteria based on prior operation of the robotic device in respective environments similar to the environment. Responsive to determining the criteria for selecting a gait, the computing system may determine whether the identified gaits include a gait that enables the robotic device to move at the velocity according to the set of criteria, and provide instructions to operate based on the determination.

Abstract: An example method may include i) determining, by a robot having at least one foot, a representation of a coefficient of friction between the foot and a ground surface; ii) determining, by the robot, a representation of a gradient of the ground surface; iii) based on the determined representations of the coefficient of friction and the gradient, determining a threshold orientation for a target ground reaction force on the foot of the robot during a step; iv) determining the target ground reaction force, where the target ground reaction force comprises a magnitude and an orientation; v) determining an adjusted ground reaction force by adjusting the orientation of the target ground reaction force to be within the determined threshold orientation; and vi) causing the foot of the robot to apply a force on the ground surface equal to and opposing the adjusted ground reaction force during the step.