This article studies the formation tracking control (FTC) of nonlinear second-order leader–following multiagent systems (LFMASs) with time-varying delays and periodic sampling. The FTC protocols based on position and velocity information of neighbor agents and measurable communication noise in fixed and Markovian switching directed topology are proposed. Some sufficient conditions are obtained to reach formation tracking by using the algebraic graph theory and generalized Halanay inequality. Meanwhile, the upper bound of formation-able time-varying delays $\bar{\tau }$ is obtained. Results show that the LFMASs can achieve formation tracking in mean-square exponential stability as well as almost sure exponential stability under the proposed control algorithms. Finally, the availability of the theoretical results is verified by numerical simulation.

Gait plays a decisive role in the performance of hexapod robot walking; this paper focuses on adaptive gait generation with reinforcement learning for a hexapod robot. Moreover, the hexapod robot has a high-dimensional action space and therefore it is a great challenge to use reinforcement learning to directly train the robot’s joint angles. As a result, a hierarchical and modular framework and learning details are proposed in this paper, using only seven-dimensional vectors to denote the agent actions. In addition, we conduct experiments and deploy the proposed framework using a real hexapod robot. The experimental results show that superior reinforcement learning algorithms can converge in our framework, such as SAC, PPO, DDPG and TD3. Specifically, the gait policy trained in our framework can generate new adaptive hexapod gait on flat terrain, which is stable and has lower transportation cost than rhythmic gaits.