Computation of a decentralized feedback strategy for consensus tracking problem of multi-agent systems that communicate over a directed graph containing a directed spanning tree, is considered. The agents are subjected to bounded control inputs and are governed by double integrator dynamics. Agents transmit their state measurement data and upper bound on control input to other agents over directed edges in the graph. Using the transmitted data, the agents track the reference trajectory generated by an agent that is assigned as the root node. Each pair of agents connected by a directed edge is identified as a pursuer-evader pair where the child node (pursuer) tries to match its state with that of the parent node (evader), in finite time by consuming min-max amount of time-fuel. Nash equilibrium feedback strategies using time-fuel optimal switching curves are derived for the two-player time-fuel pursuit evasion game. By making use of the derived Nash equilibrium strategy each child node tracks its respective parent node's state by locally consuming min-max time-fuel cost. As a consequence, all agents are shown to track the reference trajectory generated by the root agent in finite time with reduced fuel consumption.

To derive analytical feedback solution of time-L1 optimal control problem is a challenging task. In this regard, this paper proposes an alternative strategy that involves intermittent application of open loop time-L1 optimal solution. When disturbances affect the system, such policy is shown to retain the system states to within a small bounded safe region about the origin. The key idea is to switch the processor in between active and idle mode. During the active mode, the states are measured, open-loop optimal control policy is computed and transmitted along the communication link to the actuator. While during the idle mode, the precomputed control profile is applied and rest of the system resources remain inactive. The open loop solution is obtained by solving a set of optimization problems with an additional bound constraint on the update time instances. The bound constraints are derived using an algorithm to ensure that the safe region (defined in terms of attainable set) is always inside the null controllable region or the reachable set. Since attainable and reachable sets are convex polytopes, the bound constraints are obtained through linear inequalities. Simulation results show that under the proposed control strategy, system achieves practical stability with reduced usage of system resources.

With the development of miniaturization technology, micro-electromechanical system (MEMS) electrothermal microgrippers have been widely used owing to their compact size, ease of manufacturing, and low production cost. Since most of these systems are governed by partial differential equations (PDEs), modeling of microgrippers poses a significant challenge for designers. To reduce the overall computational complexity, it is a common practice to model the microgripper system using the finite element method (FEM). During the design process, the geometric and analytical properties of the microgripper influence the system dynamics to a great extent, and this work focuses on studying the effects of such parameter changes. In low-voltage applications, the performance of the microgripper is influenced by the geometrical variations, and the air gap. Hence, for the modeling of the microgripper, actuator arm lengths, and the gap between the arms are chosen as the two main geometric design parameters, while the input current density is considered as the analytical design parameter. In this work, the optimized design parameter values for maximum possible displacement are obtained with the use of sine cosine algorithm (SCA). Furthermore, an averaging operation is proposed for efficiently designing the MEMS electrothermal microgripper, and the efficacy of the proposed design methodology is demonstrated through simulation studies.

This work addresses the attitude tracking problem of reusable launch vehicle (RLV) in its re-entry phase under limited use of communication resources. The inherent nonlinear dynamics and challenging environmental conditions render the objective of navigating the RLV along a desired path to be a difficult task. In this regard, a time-delay based control (TDC) strategy with input hysteresis quantizer is proposed to achieve robustness against external disturbances and model uncertainties. The TDC approach utilizes input-output data of the immediate past instant for estimating the uncertainties effecting the space shuttle. While, the input quantizer discretizes the continuous TDC command to a finite set of predefined discrete levels. Thus, wireless transmission of control command to the actuator is carried out at a lower rate and obeys the communication constraint. Stability analysis using Lyapunov’s method is carried out to demonstrate uniformly ultimately bounded (UUB) convergence of the system states on application of the proposed control scheme. Simulation studies have been included to highlight efficacy of the proposed control scheme in terms of robust tracking of the reference trajectory and control update reduction.