Analysis, design, and control for robots in temperature-restricted environments

Abstract

In this thesis, the problem of controlling the internal and external temperatures of a robot operating within a temperature-restricted environment was addressed. One example of a temperature-restricted environment is the interior of a holding tank for Liquefied Petroleum Gas (LPG), which is the focus of the analysis in this work, but not the only possible application. This gas is stored at sub-zero temperatures to maintain its liquidity, and any significant rise in temperature can cause the gas to vaporize, posing a safety hazard. The tank in which the gas is stored must be periodically inspected for defects. Using robot inspectors while the tank is in service would reduce the cost due to lost productivity during human inspection. A thermal management system (TMS) was designed to maintain the robot's electronics and components within operating limits, while preventing the external environment from increasing in temperature above safe levels. A detailed model of the system was constructed for simulation, and the results indicate that the system performs as intended, but requires closed-loop control to maintain robot operation for extended periods of time. A control system based on system model linearization and model predictive control was implemented for the TMS. The results of the closed-loop simulations indicate that the control system enhances the operation of the TMS, maintaining robot operating temperatures for extended periods of time, while avoiding an unsafe rise in the temperature of the external environment.