Abstract: An example implementation includes (i) receiving sensor data that indicates topographical features of an environment in which a robotic device is operating, (ii) determining, for a particular topographical feature of the environment in a direction of travel of the robotic device, a height of the particular topographical feature and a distance between the robotic device and the particular topographical feature, (iii) estimating a ground plane extending from the robotic device in the direction of travel toward the particular topographical feature, the ground plane fitting to the determined distance and height, (iv) determining a grade of the estimated ground plane, and (v) directing the robotic device to adjust pitch in proportion to the determined grade.

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: An example implementation includes determining a force allocation for at least one foot of a legged robotic device, where the legged robotic device includes two feet coupled to two legs extending from a body of the legged robotic device. The implementation also includes determining a change in mass distribution of the legged robotic device, and based on the determined change in mass distribution, determining a force and a torque on the body of the legged robotic device with respect to a ground surface. The implementation also includes updating the determined force allocation for the at least one foot of the two feet based on the determined force and torque. The implementation also includes causing the at least one foot to act on the ground surface based on the updated force allocation.

Abstract: Example systems and methods for estimating a ground plane are provided. An example method may include determining an orientation of a body of a robotic device with respect to a gravity aligned reference frame. The method may also include determining the location of one or more contact points between the robotic device and a ground surface. The method may also include determining a ground plane estimation of the ground surface based on the determined orientation of the robotic device with respect to the gravity aligned reference frame and the determined locations of the one or more contact points. The method may also include determining a distance between the body of the robotic device and the determined ground plane estimation. The method may also include providing instructions to adjust a position and/or orientation of the robotic device based on the determined distance and the determined ground plane estimation.

Abstract: An example implementation involves receiving measurements from an inertial sensor coupled to the robot and detecting an occurrence of a foot of the legged robot making contact with a surface. The implementation also involves reducing a gain value of an amplifier from a nominal value to a reduced value upon detecting the occurrence. The amplifier receives the measurements from the inertial sensor and provides a modulated output based on the gain value. The implementation further involves increasing the gain value from the reduced value to the nominal value over a predetermined duration of time after detecting the occurrence. The gain value is increased according to a profile indicative of a manner in which to increase the gain value of the predetermined duration of time. The implementation also involves controlling at least one actuator of the legged robot based on the modulated output during the predetermined duration of time.

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 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.

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: 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: 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: 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: 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 implementation includes (i) receiving sensor data that indicates topographical features of an environment in which a robotic device is operating, (ii) determining, for a particular topographical feature of the environment in a direction of travel of the robotic device, a height of the particular topographical feature and a distance between the robotic device and the particular topographical feature, (iii) estimating a ground plane extending from the robotic device in the direction of travel toward the particular topographical feature, the ground plane fitting to the determined distance and height, (iv) determining a grade of the estimated ground plane, and (v) directing the robotic device to adjust pitch in proportion to the determined grade.

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: 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 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: 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.

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: 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 systems and methods for estimating a ground plane are provided. An example method may include determining an orientation of a body of a robotic device with respect to a gravity aligned reference frame. The method may also include determining the location of one or more contact points between the robotic device and a ground surface. The method may also include determining a ground plane estimation of the ground surface based on the determined orientation of the robotic device with respect to the gravity aligned reference frame and the determined locations of the one or more contact points. The method may also include determining a distance between the body of the robotic device and the determined ground plane estimation. The method may also include providing instructions to adjust a position and/or orientation of the robotic device based on the determined distance and the determined ground plane estimation.