Dynamic responses of a 2R manipulator in zero-gravity state excited by ender impacts and base motions

In this paper dynamic responses of a 2R manipulator which operates in zero-gravity state of out-space station are studied, specially considering both the impacts which are applied on its link ender and the base motion excitation. The ender impact and joint impact refer to the forces induced by capturing free-flying target or sudden locked of joint respectively, whereas the base motion excitation of the manipulator refers to the motion of its attached spacecraft. Firstly the governing equations of the 2R manipulator subjected to above two categories of excitations are established. The joint frictions are also included and expressed by Stribeck friction model together with flexible stiffnesses of joints. Numerical simulations of the dynamic model of the system under different cases of impact and base motion excitations show that the dynamic behaviors of the ender of the manipulator are differently described by both transient trajectories in time-domain and amplitude-frequency spectra in frequency domain

Head-raising of snake robots based on a predefined spiral curve method

© 2018 by the authors. A snake robot has to raise its head to acquire a wide visual space for planning complex tasks such as inspecting unknown environments, tracking a flying object and acting as a manipulator with its raising part. However, only a few researchers currently focus on analyzing the head-raising motion of snake robots. Thus, a predefined spiral curve method is proposed for the head-raising motion of such robots. First, the expression of the predefined spiral curve is designed. Second, with the curve and a line segments model of a snake robot, a shape-fitting algorithm is developed for constraining the robot's macro shape. Third, the coordinate system of the line segments model of the robot is established. Then, phase-shifting and angle-solving algorithms are developed to obtain the angle sequences of roll, pitch, and yaw during the head-raising motion. Finally, the head-raising motion is simulated using the angle sequences to validate the feasibility of this method

Physical human-robot collaboration: Robotic systems, learning methods, collaborative strategies, sensors, and actuators

This article presents a state-of-the-art survey on the robotic systems, sensors, actuators, and collaborative strategies for physical human-robot collaboration (pHRC). This article starts with an overview of some robotic systems with cutting-edge technologies (sensors and actuators) suitable for pHRC operations and the intelligent assist devices employed in pHRC. Sensors being among the essential components to establish communication between a human and a robotic system are surveyed. The sensor supplies the signal needed to drive the robotic actuators. The survey reveals that the design of new generation collaborative robots and other intelligent robotic systems has paved the way for sophisticated learning techniques and control algorithms to be deployed in pHRC. Furthermore, it revealed the relevant components needed to be considered for effective pHRC to be accomplished. Finally, a discussion of the major advances is made, some research directions, and future challenges are presented