Instrumentation and Hardware-in-the-Loop Simulation of a Control System for a Thermal Management Test Rig

Kurzfassung

Effective thermal management is crucial for maintaining the performance and reliability of engineering systems. This thesis explores the instrumentation for control system development and hardware-in-the-loop testing of a thermal management test rig. The test rig is designed to study the performance and behavior of different types of heat exchangers, making it suitable for testing different cooling strategies and airflow control methods. It mainly consists of an axial fan, a cross flow heat exchanger, and a modular air duct. The axial fan regulates the airflow through the air duct to control the cooling process, while the heat exchanger facilitates heat transfer from the liquid coolant to the gaseous coolant (air). Liquid coolant used is water. To enable real-time monitoring of the system’s performance, sensors are strategically placed throughout the test rig to measure parameters such as temperature, volume flow rate, and pressure. The work done in this thesis can be divided into four parts. The first part of this work involves controlling the Huber system’s liquid coolant temperature and pump speed using MATLAB scripts and Simulink via serial communication. The Huber system acts as an initial reservoir to provide liquid coolant at a precisely controlled temperature. Its internal heater regulates the liquid coolant temperature using built-in sensors. Once the liquid coolant reaches the set-point, the Huber system maintains it at that temperature. This serves as baseline testing for external sensor’s functionality. External temperature sensors installed along the test rig’s piping, only measure the liquid coolant temperature, allowing for verification of the accuracy of the temperature sensors. The Huber pump speed is adjusted to verify that the volume flow sensor is measuring the liquid coolant flow. Additionally, the pressure sensors are checked to ensure they provide readings for the system’s (test rig) inlet and outlet pressures when the liquid coolant is flowing through the system. The second part deals with the interfacing of different sensors (temperature (PT100), pressure, and volume flow sensors) and actuators (fan and pump) of the thermal management test rig with the Speedgoat real-time target machine to achieve real-time data acquisition and control using MATLAB/Simulink. The third part focuses on developing a control oriented state-space model describing the thermal dynamics of the test rig. Physics based non-linear differential equations relevant to describe the thermal dynamics were used to develop the parametric control oriented model which were then linearized using Taylor series expansion, leading to the formulation of the linear state-space representation of the system. The unknown parameters of the system were determined experimentally. Finally, a Linear Quadratic Regulator (LQR) controller is designed and implemented with the aim of controlling the temperature of the heat source. For the experimental setup a tank equipped with a 2 kW external heater is used as a heat source. where the temperature of the liquid coolant inside the heat source is considered to be equal to the outlet temperature, based on the lumped parameter assumption. A temperature sensor, placed at the outlet of the heat source, measures the temperature of the liquid coolant entering the heat exchanger. Therefore, controlling the outlet temperature of the heat source becomes the main task. By combining instrumentation, modeling, and control strategies, this thesis contributes to the development of real-time control techniques for thermal management systems, improving their precision and effectiveness.