IBCS HL Topic 7 - Network

Control System

A device/set of devices that mange the behaviour of other devices. If a human body is involved = automated.

4 Functions of a Control System

• Measurement

• Comparison

• Computation

• Correction

Automatic control systems

To be automated, the following hardware is used:

• Sensor - equipment to measure system variables

• Controller/processor - equipment to perform comparison and computation

• Control Element/Actuator/Output transducer - performs the control action. Receives a signal from the controller.

Examples of Control Systems

• Automatic Doors

• Elevator

• Traffic Light

• Global Positioning System (GPS)

Automatic Doors

Sensor is often infrared or microwave. The sensor receives a signal from human movement and send this to the processor which then send info to the automator to move. Photocells in the door make sure it doesn’t close on anyone.

Elevator

Comprised of buttons to each floor, a motor to move the cab, motorised doors, and a computer for control. Magnetic sensors in the cab and shaft alert the computer of the elevators position. It’s next floor and movements are dictated by the computer.

Traffic Light

The pedestrian pushes a button that sends a signal to the microprocessors. This waits for an appropriate time to change the light w/ sensors. Using underground electrical wire, a magnetic field is created to sense metal to check when cars approach.

GPS

GPS communicates with the sensors on satellite, creating spheres per satellites which converge on your location. The more spheres the higher the accuracy.

Microprocessors

An integrated circuit that has an entire CPU in a single chip. Generally takes the role of control element.

Advantages of microprocessors

• Can process data very quickly

• Can react very quickly to change

• Can run 24/7

• Outputs are consistent and error free

Disadvantages of microprocessors

• May cost a lot to develop specialised software

• In the event of a power shortage…

• If a malfunction occurs, the system won’t run

• Can’t react to events outside of programming

Analog-Digital Convertor (ADC)

A device that converts analog data to readable digital data. DAC is also an option!

Sensor

An analog device that sends it readings to an ADC which sends data to the CPU for processing.

Different Input devices

• Kinect - Xbox 360 motion sensing device that lets the user interact through gestures and spoken response

• Passive Infrared sensor - measures infrared light emitted from objects that generate heat

• Laser Rangefinder - Bounces the energy of a leaser beam at a target and measures the return time. Speed of light is constant so reading is highly accurate.

• Temp. sensor - gathers temp. data and converts it to digital data. Has many forms and levels of precision.

Open loop feedback system

Only looks at input. A light set to come on at 7pm will do so irrespective of how dark/light it is outside.

Closed loop feedback system

Output affects the input. Continuous sensing so that the processor can control actuator to regulate process. Not energy efficient.

Surveillance (Ethics)

Use of IT to monitor the actions of people. Example: prisoner tagging with monitors to electronically transmit their location at all times.

CCTV (Ethics)

Closed Circuit TeleVision. Cameras operated in most public spaces today. Undeniable public service benefits but subject to bias and discrimination towards marginalised individuals.

Pros of surveillance (prisoner tagging)

• No cost compared to prison

• Households can still rely on convicted person(s)

• Potential improved rehabilitation into society

Cons of surveillance (prisoner tagging)

• Doesn’t prevent future crime

• Privacy issues

• Sensitive data could be leaked

• Not reliable in some areas

Centrally controlled systems

Where a single entity like a server or a main controller govern all components and actions in a system. Everything flows through this node.

Distributed systems

Network of interconnected nodes that work towards a common goal. Decision-making is decentralised, with each node having a degree of autonomy. Nodes talk directly with each other.

Control (Central vs. Distributed)

Single central entity in charge vs. Control distributed among several nodes

Communication (Central vs. Distributed)

Communication goes through a single entity vs. Direct communication between nodes

Architecture (Central vs. Distributed)

Hierarchal, master-slave vs. Peer-to-peer, decentralised

Scalability (Central vs. Distributed)

Limited by capacity of entity vs. Easier to scale with more nodes

Fault tolerance (Central vs. Distributed)

Vulnerable to single point of failure vs. More resilient, nodes take over

Complexity (Central vs. Distributed)

Typically less complex vs. Can be more complex due to coordination

Examples (Central vs. Distributed)

Mainframes vs. P2P networks, Cloud computing

Autonomous agents

Self-governing entities that can perceive their environment and take actions based on goals.

Role of autonomous agents in a larger system

• Task decomposition → Can break complex tasks into more manageable sub-tasks

• Decision-Making → can adapt to environment

• Coordination & Cooperation → agents can talk and collaborate with other agents

• Specialisation → can be designed with specific skills in mind