Haya Mohamed Swilam 82
Discrete Systems Report

1) Advantages:
- Provide improved sensitivity to parameter variations.
- Less sensitive to noise and disturbance.
- Less expensive
- More reliable
- Easy to manipulate
- Changing a design doesn't require an alternation in the hardware so new features can be added to a   digital system more easily.
- Digital processors are more compact and light weight.

2) Disadvantages:
- Use more energy than analogue circuits to accomplish the same task, producing more heat.
- Limitations on computing speed and signal resolution due to finite word length of the digital processor whereas the resolution of analogue controllers is theoretically infinite.
- The limitation on computing speed causes time delay in the control loop which may cause instability in closed loop systems.
- Digital circuits are fragile in that if a single piece of digital data is lost or misinterpreted the meaning of large blocks of related data can completely change.
- Quantization error due to analogue signal sampling.

3) Examples on Discrete Systems:
- A simplified single access auto pilot control system:
the objective of the control is to maintain the wings in a certain position. A digital controller with the necessary A/D and D/A converters can be used.
- Digital computer-controlled rolling mill regulating system:
where a digital computer is provided with information describing the rolling mill equipment, the material to be rolled and the starting dimensions and required finish dimensions, is used to direct the adjustment of the mill settings before every path in order to achieve the optimum product.
- Most modern automobiles today have integrated computer systems that monitor certain aspects of the car, and actually help to control the performance of the car. The speed of the car, and the rotational speed of the transmission are analog values, but a sampler converts them into digital values so the car computer can monitor them. The digital computer will then output control signals to other parts of the car, to alter analog systems such as the engine timing, the suspension, the brakes, and other parts.
- A digital filter system usually consists of an analog-to-digital converter to sample the input signal, followed by a microprocessor and some peripheral components such as memory to store data and filter coefficients etc. Finally a digital-to-analog converter to complete the output stage