SUMMARY In this research, a dynamic model is first established based on screw theory and the principle of virtual work for a bilaterally symmetrical hybrid robot. By combining a novel composite error (NCE) with second-order nonsingular fast terminal sliding mode (SONFTSM) control method, a NCE-based SONFTSM dynamic control method is further presented to guarantee better trajectory tracking performance and synchronization performance simultaneously. The asymptotic convergence of proposed errors and the stability of the proposed control method have been proved theoretically. Finally, the simulation and experiment are implemented to validate the effectiveness of the proposed control method.

This paper considers the finite-time dynamic tracking control for parallel robots with uncertainties and input saturation via a finite-time nonsingular terminal sliding mode control scheme. A disturbance observer is designed to estimate the lumped disturbance in the dynamic model of the parallel robot, including modeling errors, friction and external disturbance. By introducing the fractional exponential powers into the existing asymptotic convergent auxiliary system, a novel finite-time convergent auxiliary system is constructed to compensate for input saturation. The finite-time nonsingular terminal sliding mode control is proposed based on the disturbance estimation and the state of the novel auxiliary system, so that the convergence performance, control accuracy and robustness are improved. Due to the estimation and compensation for the lumped disturbance, the inherent chattering characteristic of sliding mode control can be alleviated by reducing the control gain. The finite-time stability of the closed-loop system is proved with Lyapunov theory. Finally, simulation and experimental research on the dynamic control of a conveying parallel robot are carried out to verify the effectiveness of the proposed method.

Demand response (DR) in the smart grid will promote the stable operation of the power system and reduce economic costs effectively. However, uncertainty of users' behavior becomes a barrier of DR, in which the credibility between the DR users and aggregators will have a crucial impact on the DR. Blockchain is a new technology to solve the trust problem without third-party endorsement, which has the advantages of decentralization and irreversibility. Considering the difference of computing capability between users and aggregators, this article proposes a blockchain-based strategy to support the bidirectional selection between DR users and aggregators based on reputation values, which improves the success rate of the DR and mitigates the impact of user behavior on the DR. At the same time, this strategy can also increase the enthusiasm of users with a high reputation value to participate in DR. Using the network topology and DR incentive rules of Suzhou, Jiangsu Province, the rationality of blockchain-based reliable interoperation for DR entities proposed in this paper is verified.

The road of a greenhouse is both damp and narrow, and there are both ground obstacles and space obstacles in a greenhouse, which easily cause the instability problem for a four-wheel independent driving greenhouse spraying mobile robot turning in the greenhouse. In order to improve the steering performance of the greenhouse spraying mobile robot, based on the characteristics that each wheel torque of the robot can be separately controlled, the dynamic model of the four-wheel independent steering system is firstly established using D'Alembert's principle and choosing the sideslip angle and the yaw velocity as the state variables. Then, based on the theory of sliding mode control, a dynamic sliding mode control strategy with exponential approaching rate is proposed by adopting the sideslip angle and the yaw velocity as the joint control variables in order to make the sideslip angles be in the stable range and make the yaw velocity track the desired value well. Finally, the simulation of the steering performance is performed using MATLAB/Simulink. The control response curves of the yaw velocity and the sideslip angle of the robot's mass center in a step input and in a sinusoidal input are obtained, respectively. It is shown from the simulation results that compared with the feedforward-feedback control method, the proposed dynamic sliding mode control strategy based on the established dynamic model is effective to improve the turning control stability of the mobile robot for greenhouse spraying. The experiment results further verify the feasibility of the proposed turning control strategy.

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