3.  Types of PID controller:

3.1  Parallel PID Controller

Figure 3.4.10 shows the parallel configuration of PID controller. In general, this type of PID is preferred over series one because in Parallel PID, output of one controller does not affect the output of other. This allows freedom to control parameters independently.

Figure 3.4.10 Configuration of PID controller

 

3.2 Series PID Controller

Figure 3.4.11 shows the typical configuration of series PID controller. In this type of controller, the output of a controller affects the output obtained from the other. Therefore the order of controller must be taken into account during designing such configuration.

Figure 3.4.11 Series PID controller

Detail analysis and study of these controllers is out of the scope of the present course. However readers are advised to read following books for further study:

1. PID controllers 2nd ed., by Karl J. Astrom and Tore Hagglund, Research Triangle Park, ISA 1995.
   
   
2. Structure and synthesis of PID controllers, by Aniruddha Dutta, Ming-Tzu Ho and Shankar P. Bhattacharyya, Springer-Verlag, Londoan 2000.

PID controllers have wide variety of applications manufacturing industry. Some of them are listed as follows.

1. PID control is used in automatic car steering when it is integrated with Fuzzy Logic
2. In movement detection system of modern seismometer
3. In water/oil level monitoring in tanks
4. Head positioning of a disk drive
5. Automated inspection and quality control
6. Manufacturing process control: CNC machine tools
7. Chemical process control: flow control, temperature control
8. Automatic control of material handling equipments
9. Automatic packaging and dispatch
10. To ensure safety during manufacturing operations