Design and Implementation of Symmetric Legged Robot for Highly Dynamic Jumping and Impact Mitigation.

Aiming at highly dynamic locomotion and impact mitigation, this paper proposes the design and implementation of a symmetric legged robot. Based on the analysis of the three-leg topology in terms of force sensitivity, force production, and impact mitigation, the symmetric leg was designed and equipped with a high torque density actuator, which was assembled by a custom motor and two-stage planetary. Under the kinematic and dynamic constraints of the robot system, a nonlinear optimization for high jumping and impact mitigation is proposed with consideration of the peak impact force at landing. Finally, experiments revealed that the robot achieved a jump height of 1.8 m with a robust landing, and the height was equal to approximately three times the leg length.

Geometrical Structures of Gas Phase Chromium Oxide Cluster Anions Studied by Ion Mobility Mass Spectrometry.

Structural assignments of gas phase chromium oxide cluster anions, CrmOn- (m = 1-7), have been achieved by comparison between experimental collision cross sections measured by ion mobility mass spectrometry and theoretical collision cross sections of optimized structures by quantum chemical calculations. In the mass spectrum, significant magic behavior between the numbers m and n was not observed for CrmOn-, while wide ranges of compositions were observed around CrmO2m+2- to (CrO3)m- as reported previously. The (CrO3)m- (m = 3-7) ions were assigned to have monocyclic-ring structures for m = 3-5 and bicyclic rings for m = 6 and 7. In addition, gradual structural change from these cyclic structures of (CrO3)m- to three-dimensional structures of CrmO2m+2- was found for m = 4-7. The energy levels of molecular orbitals of a calculated monocyclic structure of Cr5O15- were also found to be consistent with previous results of photoelectron spectroscopy, although those of the bicyclic isomer exhibited a different behavior. Moreover, the observation of abundant ions generated by collision induced dissociations at the inlet of the ion drift cell indicates that the larger sized (CrO3)m- (m > 5) series were unstable and easily dissociated to smaller ions.

Biomimetic Soft Underwater Robot Inspired by the Red Muscle and Tendon Structure of Fish.

Underwater robots are becoming increasingly important in various fields. Fish robots are attracting attention as an alternative to the screw-type robots currently in use. We developed a compact robot with a high swimming performance by mimicking the anatomical structure of fish. In this paper, we focus on the red muscles, tendons, and vertebrae used for steady swimming of fish. A robot was fabricated by replacing the red muscle structure with shape memory alloy wires and rigid body links. In our previous work, undulation motions with various phase differences and backward quadratically increasing inter-vertebral bending angles were confirmed in the air, while the swimming performance in insulating fluid was poor. To improve the swimming performance, an improved robot was designed that mimics the muscle contractions of mackerel using a pulley mechanism, with the robot named UEC Mackerel. In swimming experiments using the improved robot, a maximum swimming speed of 25.8 mm/s (0.11 BL/s) was recorded, which is comparable to that of other soft-swimming robots. In addition, the cost of transport (COT), representing the energy consumption required for robot movement, was calculated, and a minimum COT of 0.08 was recorded, which is comparable to that of an actual fish.

Bio-Inspired Take-Off Maneuver and Control in Vertical Jumping for Quadruped Robot with Manipulator.

The jumping motion of legged robots is an effective way to overcome obstacles in the rugged microgravity planetary exploration environment. At the same time, a quadruped robot with a manipulator can achieve operational tasks during movement, which is more practical. However, the additional manipulator will restrict the jumping ability of the quadruped robot due to the increase in the weight of the system, and more active degrees of freedom will increase the control complexity. To improve the jumping height of a quadruped robot with a manipulator, a bio-inspired take-off maneuver based on the coordination of upper and lower limbs is proposed in this paper. The kinetic energy and potential energy of the system are increased by driving the manipulator-end (ME) to swing upward, and the torso driven by the legs will delay reaching the required peak speed due to the additional load caused by the accelerated ME. When the acceleration of ME is less than zero, it will pull the body upward, which reduces the peak power of the leg joints. Therefore, the jumping ability of the system is improved. To realize continuous and stable jumping, a control framework based on whole-body control was established, in which the quadruped robot with a manipulator was a simplified floating seven-link model, and the hierarchical optimization was used to solve the target joint torques. This method greatly simplifies the dynamic model and is convenient for calculation. Finally, the jumping simulations in different gravity environments and a 15° slope were performed. The jump heights have all been improved after adding the arm swing, which verified the superiority of the bio-inspired take-off maneuver proposed in this paper. Furthermore, the stability of the jumping control method was testified by the continuous and stable jumping.