Huiyu Sun

A Modular Self-Reconfigurable Robot with Enhanced Locomotion Performances: Design, Modeling, Simulations, and Experiments

This paper presents the design and implementation of a modular self-reconfigurable robot with enhanced locomotion capabilities. It is a small hexahedron robot which is 160 mm × 140 mm × 60 mm in size and 405 g in weight. The robot is driven by three omnidirectional wheels, with up and down symmetrical structure. The robot can perform rectilinear and rotational locomotion, and turn clockwise and counterclockwise without limitation. A new docking mechanism that combines the advantages of falcula and pin-hole has been designed for attaching and detaching different modules. The communication and image data transmission are based on a wireless network. The kinematics and dynamics of the single module has been analyzed, and the enhanced locomotion capabilities of the prototype robot are verified through experiments. The maximum linear velocity is 25.1cm/s, which is much faster than other modular self-reconfigurable robots. The mobility of two connected modules is analyzed in the ADAMS simulator. The locomotion of the docking modules is more flexible. Simulations on the wheel and crawling locomotion are conducted, the trajectories of the robot are shown, and the movement efficiency is analyzed. The docking mechanisms are tested through docking experiments, and the effectiveness has been verified. When the transmission time interval between the adjacent packets is more than 4 ms, the wireless network will not lose any packet at the maximum effective distance of 37 m in indoor environments.

P-like controllers with collision avoidance for passive bilateral teleoperation of a UAV

This paper aims to tele-operate the movement of an unmanned aerial vehicle (UAV) in the obstructed environment with asymmetric time-varying delays. A simple passive proportional velocity errors plus damping injection (P-like) controller is proposed to deal with the asymmetric time-varying delays in the aerial teleoperation system.,This paper presents both theoretical and real-time experimental results of the bilateral teleoperation system of a UAV for collision avoidance over the wireless network. First, a position-velocity workspace mapping is used to solve the master-slave kinematic/dynamic dissimilarity. Second, a P-like controller is proposed to ensure the stability of the time-delayed bilateral teleoperation system with asymmetric time-varying delays. The stability is analyzed by the Lyapunov–Krasovskii function and the delay-dependent stability criteria are obtained under linear-matrix-inequalities conditions. Third, a vision-based localization is presented to calibrate the UAV’s pose and provide the relative distance for obstacle avoidance with a high accuracy. Finally, the performance of the teleoperation scheme is evaluated by both human-in-the-loop simulations and real-time experiments where a single UAV flies through the obstructed environment.,Experimental results demonstrate that the teleoperation system can maintain passivity and collision avoidance can be achieved with a high accuracy for asymmetric time-varying delays. Moreover, the operator could tele-sense the force reflection to improve the maneuverability in the aerial teleoperation.,A real-time bilateral teleoperation system of a UAV for collision avoidance is performed in the laboratory. A force and visual interface is designed to provide force and visual feedback of the slave environment to the operator.

Energy-Optimized Consensus Formation Control for the Time-Delayed Bilateral Teleoperation System of UAVs

This paper proposes an energy-optimized consensus formation scheme for the time-delayed bilateral teleoperation system of multiple unmanned aerial vehicles (UAVs) in the obstructed environment. To deal with the asymmetric time-varying delays in aerial teleoperation, the local damping is independently distributed on both sides to enforce consensus formation and force tracking of the master haptic device and the slave UAVs. The stability of the time-delayed aerial teleoperation system is analyzed by the Lyapunov function. In addition, a flux-conserved force field is incorporated into the aerial teleoperation system to guarantee a collision-free consensus formation in the obstructed environment. Moreover, to reduce the communication complexity and energy dissipation of the formation, a top-down strategy of 3D optimal persistent graph is first proposed to optimize the formation topology. Under the optimized topology with environmental constraints, communication complexity and energy dissipation can be minimized while the rigid formation can be maintained and transformed persistently in the obstructed environment. Finally, the human-in-the-loop simulations are performed to validate the effectiveness of the proposed scheme.

Step-climbing maneuver for transleg in the wheeled mode

Transleg is a transformable leg-wheel robot conceived to work in the unstructured environment. The steps exist all over this environment, so it is essential that Transleg has the ability to negotiate the steps. The step-climbing performance of Transleg in the wheeled mode is studied in this paper. Transleg owns four leg-wheel and one spine mechanisms, and only the leg-wheel mechanisms are used in the study of this paper. Each leg-wheel is actuated by two actuators. One is for driving the thigh in the legged locomotion and wheel in the wheeled locomotion. The other is for driving the shank in the legged locomotion. For the low steps, Transleg can climb easily, only driving the wheels. To find the height of step Transleg can climb in this way, it is driven to climb the steps with different heights. The results show that Transleg can cross steps whose heights are a little lower than the radius of its wheels 55mm in the wheeled mode. To climb the higher steps, a step-climbing maneuver is designed. In this maneuver, the shanks play an important role. Some simulations are done to verify this maneuver, and the results show that Transleg can negotiate the steps with the height of 94mm which are much higher than the radius of its wheels using this step-climbing maneuver.

Bilateral teleoperation of multiple UAVs with low-energy coordinated formation control

This paper addresses the problem of the low-energy coordinated formation control of multiple unmanned aerial vehicles (UAVs) in a time-varying bilateral teleoperation system. To achieve the multi-UAV cooperative control with time-varying delays, a passive proportional velocity/position errors plus damping injection controller is proposed to enforce the coordinated formation and force tracking of the master haptic device and the slave UAVs. The stability of the controller is analysed by the Lyapunov-Krasovskii function and the delay-dependent stability criteria of system are obtained. Moreover, a min-weighted rigid graph is adopted to reduce the communication energy dissipation. With the optimal rigid topology, the communication links and costs can be decreased. Finally, the human-in-the-loop simulations are performed to evaluate the effectiveness of the proposed control scheme.

Bilateral teleoperation of a group of mobile robots for cooperative tasks

A visual and force feedback-based teleoperation scheme is proposed for cooperative tasks. The bilateral teleoperation system includes a haptic device, an overhead camera and a group of wheeled robots. The commands of formation and average velocities of the multiple robots are generated by the operator through the haptic device. The state of the multiple robots and the working environment is sent to the human operator. The received information contains the feedback force through the haptic device and visual information returned by a depth camera. The feedback force based on the difference between the desired and actual average velocities is presented. The wave variable method is employed in the bilateral teleoperation of multiple mobile robots with time delays. The effectiveness of the bilateral teleoperation system is demonstrated by experiments. The robots in the slave side are able to follow the commands from the master side to interact with the environments, including moving in different formations and pushing a box. The results show that the scheme enables the operator to manipulate a group of robots to complete cooperative tasks freely.