Multivariable controller auto-tuning with its application in HVAC systems

In this paper, an advanced PID auto-tuner for both single- and multivariable processes is developed and its application to HVAC systems presented. The auto-tuner exploits relay plus step test identification method to suit a wide range of processes including not only linear but also some nonlinear processes. It incorporates two latest PID design rules to achieve high control performance for processes with different dynamic characteristics. Decoupling control is used for multivariable processes. The auto-tuner was implemented on a distributed control system and practically used in industry. Experimental results exhibit the effectiveness and superior performance of the implemented auto-tuner over the manually tuned PID controller and the standard relay auto-tuner.