This paper introduces the Passive Transformable Omni-Ball (PTOB), an advanced omnidirectional wheel engineered to enhance step-climbing performance, incorporate built-in actuators, diminish vibrations, and fortify structural integrity. By modifying the omni-ball’s structure from two to three segments, we have achieved improved in-wheel actuation and a reduction in vibrational feedback. Additionally, we have implemented a sliding mechanism in the follower wheels to boost the wheel’s step-climbing abilities. A prototype with a 127 mm diameter PTOB was constructed, which confirmed its functionality for omnidirectional movement and internal actuation. Compared to a traditional omni-wheel, the PTOB demonstrated a comparable level of vibration while offering superior capabilities. Extensive testing in varied settings showed that the PTOB can adeptly handle step obstacles up to 45 mm, equivalent to 35 % of the wheel’s diameter, in both the forward and lateral directions. The PTOB showcased robust construction and proved to be versatile in navigating through environments with diverse obstacles.

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 proposes a control framework for a two-armed and two-wheeled mobile robot that can coordinate all the joint forces to achieve diverse motion objectives such as position, velocity, acceleration, force and impedance at any part of the body. The framework comprises two components: 1) Generalized Inverse Dynamics (GID) that determines joint forces satisfying multiple objectives considering task priorities and various constraints and 2) the Idealized Joint Unit (IJU) that generates accurate torque with assigned apparent inertia and viscosity. GID treats the robot as a single manipulator with multiple branches using a joint model with 2-DOF motion subspace equivalent to two opposing wheels. A 21-DOF mobile robot equipped with IJUs is set up and GID is applied to it. The result shows that GID works well in the examples of physical human-robot interaction and object manipulation where motion objectives are attained coordinating the whole body while keeping passivity due to the redundancy and the assigned impedance property.

In this paper we propose a new robust force and position control method for property-unknown objects grasping. The proposed control method is capable of selecting the force control or position control, and smooth and quick switching according to the amount of the external force. The proposed method was applied to adaptive grasping by three-fingered hand which has 12 DOF, and the experimental results revealed that the smooth collision process and the stable grasping is realized even if the precise surface position, the mass and the stiffness are unknown. In addition a new algorithm determines the grasp force according to the "slip" measured with the tactile sensor and the viscoelastic media on the fingertip. This algorithm works at starting and stationary state, so the friction and mass unknown object grasping is realized by the effectual force.