A novel reinforcement learning deep deterministic policy gradient agent-based sliding mode control (DDPG-SMC) approach is proposed to suppress the chattering phenomenon in the attitude control for quadrotors, in the presence of external disturbances. First, the attitude dynamics model of the studied quadrotor is derived and the attitude control problem is described by formulas. Second, a sliding mode controller including its sliding mode surface and reaching law is selected for the nonlinear dynamic system, and the stability of the designed SMC system is supported by Lyapunov stability theorem. Third, a reinforcement learning (RL) agent based on deep deterministic policy gradient (DDPG) is trained to adjust the switching control gain adaptively. During the training process, the input signals of agent are the actual and desired attitude angles, and the output action is the time-varying control gain. Finally, the above trained agent is applied to the SMC as a parameter regulator, to implement the adaptive adjustment of the switching control gain related to reaching law, and the simulation results verify the robustness and effectiveness of the proposed DDPG-SMC method.

Manufactured sand and natural sand have great differences in terms of physical properties, chemical composition, and so on. In the mix ratio design of manufactured sand concrete, the traditional common concrete ratio cannot be used. The water-cement ratio playing a crucial role in the mix ratio design. The optimum water-cement ratio can not only improve concrete performance, it can also reduce cement consumption and costs. The present study examines the working performance indicators and mechanical performance indicators of manufactured sand concrete using Fujian granite with three strength grades (C35, C40 and C50) at different water-cement ratios. The impact of water-cement ratio on the operational and mechanical performance of manufactured sand concrete with different strength grades is analyzed and summarized. Revised sentence: The findings suggest that the workability of Fujian granite concrete is directly influenced by the water-cement ratio. Additionally, the water-cement ratio indirectly affects the mechanical properties of manufactured sand concrete. Finally, when changing the water-cement ratio, cube compressive strength, splitting tensile strength and bending strength exhibit similar trends. The optimal water-cement ratio for C35 concrete is determined to be 0.39, considering the workability and mechanical properties of Fujian granite manufactured sand concrete. Similarly, the optimal water-cement ratio for C40 concrete is 0.34, while for C50 concrete it is 0.32.