Question

Question No 2

a) Draw functional block diagrams of a typical sensor system and a typical actuator
system. ( 10 marks)

b) Draw hierarchy of an Industrial Automation system_ Briefly describe function of each
level ( 15 marks)

Answer 1

Answer 2a)

Answer 2b)

Various components in an industrial automation system can be explained using the automation -
pyramid as shown above. Here, various layers represent the wideness and fastness of components on the time-scale.

Sensors and Acuators Layer: Also called Level '0' layer is closest to the processes and machines, used to translate signals so that signals can be derived from processes for analysis and decisions and hence control signals can be applied to the processes. This forms the base layer of the pyramid.

Automatic Control Layer:Also called level '1' layer, this layer consists of automatic control and monitoring systems, which drive the actuators using the process information given by sensors.

Supervisory Control Layer:Also called level '2' layer, this layer drives the automatic control system by setting target/goal to the controller. Supervisory Control looks after the equipment, which may consis of several control loops.

Production Control Layer:Also called level '3' layer, this solves the decision problems like production targets, resource allocation, task allocation to machines, maintenance management etc.

Enterprise control layer: Also called level '4'layer, it deals less technical and more commercial activities like supply, demand, cash flow, product marketing etc.

The spatial scale increases as the level is increased e.g. at lowest level a sensor works in a single loop, but there exists many sensors in an automation system which will be visible as the
level is increased. The lowest level is faster in the time scale and the higher levels are slower.
The aggregation of information over some time interval is taken at higher levels.
All the above layers are connected by various types of communication systems. For example the sensors and actuators may be connected to the automatic controllers using a point-to-point digital communication, while the automatic controllers themselves may be connected with the supervisory and production control systems using computer networks.