In post-disaster scenarios, field robots and unmanned aerial vehicles (UAVs) are effective tools to provide an ondemand response and guarantee the safety of humans. Sensors, field robots, and the devices equipped by UAVs, such as base stations (BSs) and mobile edge computing (MEC) servers, can be jointly deployed to form a sensing-communication-computing-control (SC3) closed loop, which could be used to complete dangerous tasks without human intervention. In this paper, we jointly optimize the communication bandwidth and computing frequency for a UAV-robot rescue system, aiming to improve the control performance of the SC3 loop. We introduce the linear quadratic regulator (LQR) cost to measure the control performance. We use the successive convex approximation (SCA) method and propose an iterative algorithm to solve the non-convex problem effectively. Numerical results corroborate the superiority of our proposed scheme compared with existing communication-oriented schemes. The results also show that the joint optimization of communication bandwidth and computing frequency is essential for closed-loop control, providing insights into the intrinsic relationships among communication, computing, and control.