Adaptive Proportional-Derivative Sliding Mode Control Law With Improved Transient Performance for Underactuated Overhead Crane Systems

In this paper, an adaptive proportional-derivative sliding mode control(APD-SMC) law, is proposed for 2D underactuated overhead crane systems. The proposed controller has the advantages of simple structure, easy to implement of PD control, strong robustness of SMC with respect to external disturbances and uncertain system parameters, and adaptation for unknown system dynamics associated with the feedforward parts. In the proposed APD-SMC law, the PD control part is used to stabilize the controlled system, the SMC part is used to compensate the external disturbances and system uncertainties,and the adaptive control part is utilized to estimate the unknown system parameters. The coupling behavior between the trolley movement and the payload swing is enhanced and, therefore, the transient performance of the proposed controller is improved.The Lyapunov techniques and the La Salle's invariance theorem are employed in to support the theoretical derivations. Experimental results are provided to validate the superior performance of the proposed control law.

Efficient Dynamic Locomotion of Quadruped Robot via Adaptive Diagonal Gait

Quadruped animals in the nature realize high energy efficiency locomotion by automatically changing their gait at different speeds.Inspired by this character,an efficient adaptive diagonal gait locomotion controller is designed for quadruped robot.A unique gait planning method is proposed in this paper.As the speed of robot varies,the gait cycle time and the proportion of stance and swing phase of each leg are adjusted to form a variety of gaits.The optimal joint torque is calculated by the controller combined with Virtual Model Control(VMC)and Whole-Body Control(WBC)to realize the desired motion.The gait and step frequency of the robot can automatically adapt to the change of speed.Several experiments are done with a quadruped robot made by our laboratory to verify that the gait can change automatically from slow-trotting to flying-trot during the period when speed is from 0 to 4 m/s.The ratio of swing phase is from less than 0.5 to more than 0.5 to realize the running motion with four feet off the ground.Experiments have shown that the controller can indeed consume less energy when robot runs at a wide range of speeds comparing to the basic controller.

Research on Pressure Tactile Sensing Technology Based on Fiber Bragg Grating Array

A pressure tactile sensor based on the fiber Bragg grating （FBG） array is introduced in this paper, and the numerical simulation of its elastic body was implemented by finite element software （ANSYS）. On the basis of simulation, fiber Bragg grating strings were implanted in flexible silicone to realize the sensor fabrication process, and a testing system was built. A series of calibration tests were done via the high precision universal press machine. The tactile sensor array perceived external pressure, which is demodulated by the fiber grating demodulation instrument, and three-dimension pictures were programmed to display visually the position and size. At the same time, a dynamic contact experiment of the sensor was conducted for simulating robot encountering other objects in the unknown environment. The experimental results show that the sensor has good linearity, repeatability, and has the good effect of dynamic response, and its pressure sensitivity was 0.03 nm/N In addition, the sensor also has advantages of anti-electromagnetic interference, good flexibility, simple structure, low cost and so on, which is expected to be used in the wearable artificial skin in the future.

A Trot and Flying Trot Control Method for Quadruped Robot Based on Optimal Foot Force Distribution

In order to enhance the dynamic motion capability of the bionic quadruped robot,a flying trot gait control method based on full-scale virtual model and optimal plantar force distribution is proposed.A stable flying trot gait is accomplished by mapping the robot torso motion to the foot trajectory.The force distribution calculated by the torso virtual model is converted into a quadratic optimization problem and solved in real time by the open source library Gurobi.The transition between the trot gait and the flying trot gait is achieved by coordinating leg motion phases.The results of the dynamic simulation verify that the proposed method can realize the 3D stable flying trot gait.Compared against the trot gait,the flying trot gait can improve the speed of the quadruped robot.Combine the trot gait and the flying trot gait,the quadruped robot can move efficiently and adapt to complex terrains.

Autonomous live working robot navigation with real-time detection and motion planning system on distribution line

In this study,an autonomous robot navigation system is designed for live working on distribution line.The developed system features a real-time detection and motion planning system,incorporating a manipulator capable of grasping power components.In order to accurately identify targets,the authors propose an object detection method based on the Larger Scale‘You Only Look Once’Version 4(LS-YOLOv4)algorithm for detecting the insulators and drop fuses.The LS-YOLOv4 extracts features of power components by Convolutional Neural Network(CNN),and then performs feature fusion.Then the authors develop a motion planning method based on the Node Control Optimal Rapidly Exploring Random Trees(NC-RRT*),which can drive the robot to realise the autonomous robot motion planning and obstacle avoidance.On the grasping function,the authors present a reliable Lightweight-based Convolutional Neural Network(L-CNN)grasping point detection method.Finally,the authors evaluate fully autonomous robotic system in both simulated and real-world experiments.The experimental results demonstrate that the proposed system can effectively identify the target and complete the grasping task in an efficient way.Notably,the proposed motion planning method can take into account both planning efficiency and accuracy to manipulation tasks.