Study Of Control System For Test Platform In Cryogenic Vacuum Environment

Before a spacecraft launched into space,thermal vacuum test must be done on the ground.In order to verify the indicators of the spacecraft whether meet the space environment, it was tested in a low-temperature vacuum compartment which approximate to the space environment.Most spacecraft's heat exchange equipment is axially grooved heat pipe. The thermal efficiency of this heat pipe is very high in weightless space. So the heat pipe can be used to temperature flattening of spacecraft. However, because of the impact of gravity the heat pipe must be placed horizontal can reach a high level of efficiency during vacuum thermal test on the ground.Therefore,a platform that can guarantee spacecraft real-time horizontally in a cryogenic vacuum environment need to be designed. The leveling mechanism applied to cryogenic vacuum environment this paper studies is services for a satellite's thermal vacuum test. This paper presents a set of leveling system with temperature control function based on PLC. The system can complete satellite leveling with high accuracy at a low temperature vacuum environment real-timely.First, the paper researched leveling principle and temperature control strategy based on the analysis of platform performance and research status. It presents a central point stationary successive approximation leveling method based on angular error control method and hereinafter referred to as referred successive approximation leveling method, In order to ensure the experimental platform can work well in a low temperature environment,proper insulation must be taken. In order to give consideration to both the response speed and overshoot in the temperature control process, making the test cooling process the key components' temperature is not too low and not to overshoot too high after cooling process, using fuzzy self-tuning PID method to control key components' temperature.Then, the paper develops and designs corresponding software based on leveling system mechanical structure and control system hardware, including parameter settings for each operating mode, automatic leveling, troubleshooting, redundant hardware switching and fuzzy self-tuning PID temperature control procedures and other procedures. For a leg chocked problem in test, using the method of switch the chocked leg as the leveling center. In terms of temperature control of the test platform components, according to PID control tuning requirements,giving the parameters'membership function,fuzzy rules and defuzzification function. And the monitoring software is developed, including human-machine interaction programs, historical data storage and reporting programs, etc.Finally, the self-leveling adjustment function is validated at normal temperature and pressure,by means of the test proved that the leveling adjustment method described in this paper is effective. In the case of a leg is chocked the system can complete automatic leveling.The platform tilt in any direction can be adjusted horizontal automatically. And it has been proved that using fuzzy self-tuning PID control algorithm to control the temperatur does not appear excessive overshoot by the test in low-temperature vacuum container tank, and it also proved the system can complete the automatic leveling of satellite. And the function of data read-write, warning systems, data store and report forms of monitoring system is feasible.