Chapter 1

Question 1

What is a real-time system?

Answer 1

A real time system must process information and deliver a response in a specified time

Question 2

What is an embedded system?

Answer 2

An embedded system is hidden from view within a larger system

Question 3

Sampling period:
Small T
Large T

Answer 3

Small T = best approximate to analogue behaviour

Large T = reduces processor time demands

Question 4

Fast RT system

Answer 4

Respond typically in less than a second

Question 5

Slow RT sytem

Answer 5

Response could take several seconds or more

Question 6

Hard RT system

Answer 6

If time requirements aren’t met it could be potentially catastrophic

Question 7

Soft RT system

Answer 7

Deadlines may not be met under certain conditions

Question 8

Examples of RT systems:
Hard-fast
Hard-slow
Soft-fast
Soft slow

Answer 8

Airbag control system
Missile point defence system
Man-machine interfacing
Machine conditioning monitoring

Question 9

What is a sampling period?

Answer 9

Time which samples of a continuous system are taken to make a discrete signal

Question 10

Multi-rate real-time control system

Answer 10

A system with multiple sensors and actuators that require different sampling periods

Question 11

Multi-rate real-time control system example

Answer 11

A helicopter
Need sensors and actuators to provide stability with a small sampling period. Also the control input from the pilot can have a larger sampling period. So may calculate the smaller sampling period every other cycle and the larger one every sixth cycle.