Tandem welding increases productivity in gas metal arc welding (GMAW). We investigate asynchronous DC–AC pulse tandem GMAW. We analyse welding arc and droplet behaviour for two tandem welding processes, DC standard-AC pulse and DC pulse-AC pulse. Spatters were generated by attractive and repulsive arc interferences. The attractive arc interaction hinders stable droplet transfer and the repulsive one can induce short-circuiting of the hanging droplets. We examine the effect of process parameters on droplet transfer and spatter generation. During DC pulse-AC pulse tandem GMAW, high peak current of the DC pulse increases arc stiffness and enhances droplet detachment. The observed consistency in arc length, droplet formation, and droplet transfer confirms the stability of asynchronous DC pulse-AC pulse tandem GMAW.

Based on the intelligent digital redesign (IDR) technique, this paper proposes a novel method for designing a sampled-data fuzzy observer estimating a state vector of a nonlinear oscillating system. The proposed method guarantees not only the state estimation performance but also the state matching performance of the designed sampled-data fuzzy observer. The state matching aims at making the difference between the state trajectories of a redesigned sampled-data fuzzy observer and the given continuous-time fuzzy observer small enough. Thus, it is assumed that the continuous-time fuzzy observer was appropriately designed in advance. To solve the IDR problem, we propose the linear matrix inequality (LMI)-based design condition that simultaneously guarantees both the state estimation and the state matching performance. Also, the conservativeness of the design condition is relaxed by developing a novel integral inequality condition and a fuzzified time-dependent Lyapunov–Krasovskii functional (LKF). Finally, the superiority of the proposed methodology is demonstrated by showing the state estimation and the state matching performance.

This study aims to propose a sampled-data control technique, utilizing a linear matrix inequality (LMI) approach, to achieve string-stable vehicle platooning in a cooperative adaptive cruise control (CACC) system with communication delays. To do this, a decentralized sampled-data controller design technique that combines one controller using sensor measurements and another one utilizing vehicle-to-vehicle (V2V) communication, ensuring both individual and string stability, is proposed first. Next, a memory sampled-data control (MSC) approach is presented to account for transmission delays in V2V communication. Additionally, an improved Lyapunov–Krasovskii functional (LKF) is presented to improve computational complexity and sampling performance. The design conditions are formulated as linear matrix inequalities (LMIs) in the time domain, facilitating efficient stability analysis and optimization. Finally, vehicle platooning simulations are provided to validate the effectiveness and feasibility of the proposed technique.