Biped robots with dynamic motion control have shown strong robustness in complex environments. However, many motion planning methods rely on models, which have difficulty dynamically modifying the walking cycle, height, and other gait parameters to cope with environmental changes. In this study, a heuristic model-free gait template planning method with dynamic motion control is proposed. The gait trajectory can be generated by inputting the desired speed, walking cycle, and support height without a model. Then, the stable walking of the biped robot can be realized by foothold adjustment and whole-body dynamics model control. The gait template can be changed in real time to achieve gait flexibility of the biped robot. Finally, the effectiveness of the method is verified by simulations and experiments of the biped robot BHR-B2. The research presented here helps improve the gait transition ability of biped robots in dynamic locomotion.

Formation of a nanometer-scale oxide surface layer is common when a material is exposed to oxygen-containing environment. Employing aberration-corrected analytical transmission electron microscopy and using single crystal SnSe as an example, we show that for an alloy, a second thin amorphous layer can appear underneath the outmost oxide layer. This inner amorphous layer is not oxide based, but instead originates from solid-state amorphization of the base alloy when its free energy rises to above that of the metastable amorphous state; which is a result of the composition shift due to the preferential depletion of the oxidizing species, in our case, the outgoing Sn reacting with the oxygen atmosphere.

Pt based alloys are one of the most important intermetallic materials with widespread applications. In this article, we have investigated the structural stability, elastic modulus, and electronic structure of Pt3M alloys by applying first-principles density functional theory, where M atom covers alkali metals, alkali earth metals, main group metals, and transition metals. The calculated elastic constants and elastic modulus demonstrated that all Pt3M alloys studied in this article are mechanically stable, possess good stability against shear and behavior in a ductile manner. The equilibrium lattice constant and the binding energy are also calculated to reveal the law with the change of elements. In addition, the LDOS and deformation charge density is presented to reveal the structural stability and the extent of charge transfer between Pt and M atoms. These results help us to better understand the physical properties of Pt3M alloys and also indicate that Pt3M alloys provide an extensive selection of intermetallic materials.

Previous research has revealed that foot rotation of the supporting foot in a single support phase could increase walking speed. This paper presents a method for force-controlled bipeds to realize foot rotation by breaking the kinematic contact constraint between the supporting foot and the ground. An inverse dynamics controller is proposed to make the biped model controllable even when the constraint is broken. In addition, a linear inverted pendulum model is extended to make its ZMP adjustable so that the ZMP can be predefined as required. When the planned ZMP is in the toe, the kinematic contact constraint will be broken and foot rotation can be achieved. A walking simulation demonstrates the effectiveness of the proposed method.

A crucial problem is the risk that a manipulator arm would be damaged by twisting or bending during and after contacting a target satellite. This paper presents a solution to minimize the risk of damage to the arm and thereby enhance contact performance. First, a hand-eye servo controller is proposed as a method for accurately tracking and capturing a target satellite. Next, a motion planning strategy is employed to obtain the best-fit contacting moments. Also, an impedance control law is implemented to increase protection during operation and to ensure more accurate compliance. Finally, to overcome the challenge of verifying algorithms for a space manipulator while on the ground, a novel experimental system with a 6-DOF (degree of freedom) manipulator on a chaser field robot is presented and implemented to capture a target field robot; the proposed methods are then validated using the experimental platform.

This paper presents a whole-body dynamics controller for robust push recovery on a force-controlled bipedal robot. Featherstone's spatial vector method is used to deduce dynamics formulas. We reveal a relationship between the accelerations of the floating base and the desired external forces needed for those accelerations. Introducing constraints on the desired external forces causes corresponding constraints on the accelerations. Quadratic programming is applied to find the extremal accelerations, which recover the robot from pushes as best as possible. A robustness criterion is proposed based on the linear inverted pendulum model to evaluate the performance of push recovery methods quantitatively. We evaluate four typical push recovery methods and the results show that our method is more robust than these. The effectiveness of the proposed method is demonstrated by push recovery in simulations.

This paper explores the design of humanoid complicated dynamic motion based on human motion capture. Captured human data must be adapted for the humanoid robot because its kinematics and dynamics mechanisms differ from those of the human actor. It is expected that humanoid movements are highly similar to those of the human actor. First, the kinematics constraints, including ground contact conditions, are formulated. Second, the similarity evaluation on the humanoid motion based on both the spatial and temporal factors compared with the human motion is proposed. Third, the method to obtain humanoid motion with high similarity is presented. Finally, the effectiveness of the proposed method is confirmed by simulations and experiments of our developed humanoid robot “sword” motion performance.