Wireless sensor network based HVAC duct pressure control

• Main Author: Zhu, Shengjie.
• Other Authors: Cai Wenjian
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Electrical and electronic engineering::Control and instrumentation::Control engineering
• Online Access: http://hdl.handle.net/10356/15823
• Institution: Nanyang Technological University

Wireless sensor network (WSN) is a network formed by a number of wireless sensor nodes. A sensor node is the wireless module. Sensor node is gathering sensory information, processing the data and communicating with other connected modules. WSN has been widely used in many industrial sectors recent years. HVAC system duct pressure measurement is one of the applications that WSN can be applied to. With WSN, users can collect the data of the HVAC duct pressure in an efficient, low cost, low energy consumption way. It is not easy to achieve by using the conventional cable system. Besides the efficient measurement approach, a proper controller design is also crucial in this project. The purpose of the controller is to stabilize the duct pressure with the setting value. Most of the controllers commissioned in industrial areas are of Proportional-Integral derivative (PID) type. Tuning a proper PID controller requires an accurate model of a Process and an effective controller design rule. The tuning procedure can be a time consuming, expensive and difficult task. This is also true to Heating, Ventilating, and Air-conditioning (HVAC) systems. Although many improved PID design methods are proposed, the Ziegler and Nichols (Z-N) methods are still the methods have been most commonly used in HVAC systems. It has sometimes been difficult to compensate fully for load disturbance and to keep controlled variables close to set point values within the prescribed range, have the shortcomings such as long testing time, limited control performance. Furthermore, finding optimal PID gains by the trial-and error process is one of the most tedious problems faced by a field operator. Even the PID controller that has been well tuned at its commissioning may perform poorly because of changes in operation conditions. This report discusses the fundamental principles of a pressure controlled variable air volume system and the control of a static pressure at the branch level in a variable air volume (VAV) system. The fan pressure set point is optimized resulting in a decreased fan power requirement and sound generation. Two methods of tuning the PI (D) controller are discussed. One is based on classical design approach and the other is steepest gradient descent method. A comparison of the two methods is also discussed.