To achieve safe legged locomotion, it is crucial to generate motion in real-time considering various constraints in robots and environments. In this study, we propose a lightweight real-time perceptive motion control system for the newly developed six-wheeled-telescopic-legged robot, Tachyon 3. In the proposed method, analytically smoothed constraints including Smooth Separating Axis Theorem (SSAT) as a novel higher order differentiable collision detection for 3D shapes is applied to the Control Barrier Function (CBF). The proposed system integrating the CBF achieves online motion generation in a short control cycle of 1 ms that satisfies joint limitations, environmental collision avoidance and safe convex foothold constraints. The efficiency of SSAT is shown from the collision detection time of 1 µs or less and the CBF constraint computation time for Tachyon 3 of several µs. Furthermore, the effectiveness of the proposed system is verified through the stair-climbing motion, integrating online recognition in a simulation and a real machine.

This paper introduces a quadruped robot, Tachyon, which aims to achieve high payload, robust, and dynamic locomotion on the various terrain with high energy efficiency. Thanks to a novel compact series-parallel elastic actuator (SPEA) on the upper link and a four-bar linkage design in the knee joint for constant vertical foot force, the 41-kg robot can carry more than 20 kg of payloads with dynamic walking. The combination of a robust horizontal CoM stabilizer and SPEA joint torque controller provides low impedance force controllability of the whole-body even when only the knee joint can accurately detect its joint torque. The major performance of Tachyon is demonstrated by carrying a 20-kg rice bag—half of its body weight—and climbing stairs with dynamic locomotion. When the robot climbs the stairs, the SPEA parallel spring improves energy efficiency by 16% and is also effective for various other gaits. The robustness of the robot is also shown by its high flexibility and fall avoidance capability when an unknown disturbance of 400 N or more is applied.

This paper presents a novel control method for a human-robot cooperative task. There is a problem that a cooperative fitting task, i.e., peg-in-hole task, could not be performed precisely using a conventional impedance control. A proposed controller changes a control mode according to the task. An impedance control based on a position control is used in a carrying task and a torque control with compensation for its dead weight and friction is used in the fitting task. In order to confirm the usefulness of the proposed control, a human-robot cooperative carrying and peg-in-hole task was performed. Experimental results illustrate that the proposed control is effective for the human-robot cooperative task.