For trajectory generation of whole-body jumping motions such as humanoid backflips, it is crucial to simultaneously optimize the takeoff, flight, and landing phases while considering full-body dynamics and kinematics. Although such methods have been proposed for standard jumping motions, they have not been applied to more dynamic actions such as frontflips, backflips, and yaw twist jumps, where strong nonlinearity and high sensitivity to certain parameters (e.g., rotor inertia and torque cost weights) pose significant challenges. To address these challenges, we apply a two-stage optimization strategy to an existing full-body dynamics optimization method that simultaneously optimizes the takeoff, flight, and landing phases. In our approach, the same initialization and reference trajectory generation rules are shared across motions, and the solution from the first optimization is used not only as an initial guess but also as a reference in the second optimization. This strategy improves the convergence of the KKT residuals across various jump types and mitigates sensitivity to parameters such as rotor inertia and torque cost weights. As a result, our method achieves unified trajectory generation for frontflips, backflips, yaw twist jumps, and standard jumps using the same initialization, cost weights, and constraints. We also analyze the sensitivity to rotor inertia and show that exceeding a certain threshold can lead to a sharp deterioration in KKT residual convergence.

Various methods have been proposed to achieve high output torque and a wide output range for fast and high-load robotic motions. However, in robots composed of slender frames, such as humanoid robots, the limited space available for actuators and transmission components restricts the application of conventional methods. In this paper, we propose a Variable Chain Motor (VC Motor), an electric actuator that features both shape variability and speed-torque characteristics variability. Shape variability refers to the ability of the actuator to change its form during operation. This property enhances output torque by enabling a dense motor arrangement even under spatial constraints imposed by the frame structure. For example, the actuator can be placed across adjacent frames and deform according to joint rotation. Speed-torque characteristics variability allows switching output characteristics during operation using a dedicated electrical circuit. This enables an expanded range of output speed and torque without significantly increasing size or weight. We evaluated the performance of the developed VC Motor by measuring output torque and efficiency. Furthermore, by applying the VC Motor to the elbow joint of a humanoid robot, we demonstrated its capability for high-speed and high-load operations.

For humanoid whole body contact motions, it is important to recognize the existence of whole body contacts and the contact forces. The challenges in recognizing the existence of whole body contacts and the contact forces in life-size humanoids are: 1) the measurement part with low mechanical strength must be tolerant of high load and 2) it is difficult to model thick elastic bodies with high impact tolerance and uneven sensor placements when applied to various shapes of the whole body. This paper proposes a method of constructing a load tolerant tactile sensor by separating the loaded part from the measuring part with magnetism and protecting the measuring part inside the frame of the robot. For modeling difficulties, this paper proposes learning the relationship between the change in the detected physical quantity due to deformation of the elastic body and the contact force distribution. This paper shows through experiments that the proposed tactile sensor based on a robot frame is load tolerant enough to support the weight of a life-sized humanoid, and that it can acquire contact force distribution and the robot is able to acclimate to external forces.

In order for a humanoid robot to balance on the movable ground, balance feedback control in response to its unpredictable movement is required. However, feedback control in response to ground movement has the following two issues, (A) Interaction between the ground dynamics and the balance control may cause vibration. (B) The balance control may rather deteriorate the stability due to the response delay. To solve these problems, this study proposes the support foot acceleration term in the walking stabilizer and gives its gain by considering the following two conditions, (A) Avoiding steady-state vibration in a two-mass linear inverted pendulum model on an arbitrary ground, and (B) reducing the influence of inertial forces resulting from the delay of ZMP feedback. Experiments with a life-size humanoid JAXON verified the steady-state vibration phenomenon and improved the stability of acceleration and deceleration when boarding the Two-Wheeled Scooter.