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18 Chapter 1 Introduction

include physical size, responsiveness, power management, etc. The example of an
embedded system that I use is a software system to control a medical device.
2. An information system This is a system whose primary purpose is to manage
and provide access to a database of information. Issues in information systems
include security, usability, privacy, and maintaining data integrity. The example
of an information system that I use is a medical records system.

3. A sensor-based data collection system This is a system whose primary purpose
is to collect data from a set of sensors and process that data in some way. The
key requirements of such systems are reliability, even in hostile environmental
conditions, and maintainability. The example of a data collection system that
I use is a wilderness weather station.

I introduce each of these systems in this chapter, with more information about
each of them available on the Web.

1.3.1 An insulin pump control system

An insulin pump is a medical system that simulates the operation of the pancreas (an
internal organ). The software controlling this system is an embedded system, which
collects information from a sensor and controls a pump that delivers a controlled
dose of insulin to a user.
People who suffer from diabetes use the system. Diabetes is a relatively common
condition where the human pancreas is unable to produce sufficient quantities of a
hormone called insulin. Insulin metabolises glucose (sugar) in the blood. The con-
ventional treatment of diabetes involves regular injections of genetically engineered
insulin. Diabetics measure their blood sugar levels using an external meter and then
calculate the dose of insulin that they should inject.
The problem with this treatment is that the level of insulin required does not just
depend on the blood glucose level but also on the time of the last insulin injection.
This can lead to very low levels of blood glucose (if there is too much insulin) or very
high levels of blood sugar (if there is too little insulin). Low blood glucose is, in the
short term, a more serious condition as it can result in temporary brain malfunctioning
and, ultimately, unconsciousness and death. In the long term, however, continual high
levels of blood glucose can lead to eye damage, kidney damage, and heart problems.
Current advances in developing miniaturized sensors have meant that it is now pos-
sible to develop automated insulin delivery systems. These systems monitor blood sugar
levels and deliver an appropriate dose of insulin when required. Insulin delivery systems
like this already exist for the treatment of hospital patients. In the future, it may be pos-
sible for many diabetics to have such systems permanently attached to their bodies.
A software-controlled insulin delivery system might work by using a micro-
sensor embedded in the patient to measure some blood parameter that is proportional
to the sugar level. This is then sent to the pump controller. This controller computes
the sugar level and the amount of insulin that is needed. It then sends signals to a
miniaturized pump to deliver the insulin via a permanently attached needle.