Sensing-Communication-Computing-Control Closed-Loop Optimization for Coordinated UAV-Robot Systems

This paper investigates an emergency rescue system, which comprises a multi-functional unmanned aerial vehicle (UAV) and multiple robots. The UAV carries sensing, communication, and computing modules. It senses system states, calculates commands, and instructs field robots to take actions. In this way, the UAV and robots form multiple sensing-communication-computing-control $(\mathbf{SC} ^{3})$ loops, which could finish many mission-critical tasks without human participation. To activate these $\mathbf{SC} ^{3}$ loops, we propose a closed-loop optimization scheme. Unlike traditional studies that primarily focus on the communication link, the proposed scheme emphasizes the $\mathbf{SC} ^{3}$ loop and adopts the linear quadratic regulator (LQR) cost as the objective. Focusing on the UAV-robot downlink, we model the data transmission in the finite block length regime and take the transmit power and block lengths as optimization variables. We solve the nonlinear integer problem by exploiting the monotonicity and convexity of the objective rate-cost function. The closed-form solution of the transmit power is derived in the assure-to-be-stable region. On this basis, we compare the proposed scheme with the max-sum rate scheme. Through comparisons, the fairness-minded nature of the proposed scheme is revealed.