【2025: Understand at a Glance】Understanding the differences and connections between PID and APC in one diagram
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The attached figure shows: Understanding the differences and connections between PID and APC at a glance.
PID stands for “proportional, integral, derivative” and is a very common control algorithm. Common PID algorithms include position PID, incremental PID, cascade PID, etc.
PID controllers are widely used in various industrial process controls, such as temperature control, flow control, and pressure control, due to their flexibility and reliability. In cars, the cruise control function is a typical example of PID control application. Furthermore, PID controllers can also be used in fields such as power electronics converters and MPPT charging controllers.
Advanced Process Control, abbreviated as APC, is not a new concept. It is merely a general term for a large category of control methods that differ from classical control, and it encompasses a very wide range of approaches. In a broad sense, any control strategy that can achieve better control performance than classical PID control can be referred to as advanced control technology.
At present, Model Predictive Control is widely applied and has achieved good results; therefore, when people discuss APC at this stage, they are often referring to MPC. In fact, there are also many forms of model predictive control, such as dynamic matrix control and generalized predictive control. But regardless of the form, it follows a basic principle: model prediction, rolling optimization, and feedback correction.
Firstly, the biggest difference between APC and conventional PID controllers is that it is no longer just control of a single variable, but rather control of the entire controlled system using multiple variables. This eliminates the mutual influence between multiple circuits.
Secondly, compared to conventional PID controllers, APC has a predictive function. Analysis can be conducted based on the operating conditions of various circuits at present, thereby enabling predictions for the future behavior of each circuit within the controller. Adjustments can then be made to these circuits based on those predictions, thus optimizing the control performance to the greatest extent possible.
Compared to classical PID controllers, APC has greater adaptability and better robustness. It is suitable for dealing with the large time lags and strong coupling characteristics of processes, and can effectively address measurable disturbances in such processes.
Furthermore, compared to traditional PID controllers, the APC strategy employs multi-variable optimization algorithms, making it suitable for handling control problems with multiple levels, objectives, and constraints; it also enables more effective control of the production process in line with its economic criteria.