Topic 7 - Control

What is a control system?

A device, or set of devices, that manages, commands, directs, or regulates the behavior of other devices or systems

Examples of a control system

• Automated doors
• Heating system
• Taxi meter
• Elevator
• Washing machine
• Process control
• Device driver
• Traffic lights

Microprocessor definition

an integrated circuit that contains all the functions of a central processing unit of a computer

Sensor

 a device which detects or measures a physical property and records, indicates, or otherwise responds to it

Types of sensors

• Motion
• Humidity
• Proximity
• Touch
• Pressure
• Gas
• Water flow
• Accelerometer
• Electrical

Accessibility alternatives - joystick and switch

Combinations enable an individual lacking sufficient mobility to use a full keyboard to access a computer through an on-screen keyboard or other “virtual substitutes”

Accessibility alternatives - keyboard alternatives

Allow individuals unable to use a standard keyboard to input keystrokes with a mouse, head mount, or other specialized device. 

Basic I-P-O model

• Simplistically, sensors take analog input and convert them to digital data.
• Digital data can then be processed by a microprocessor, producing digital output. 
• Output transducers can then turn the digital data into analog signals to power ‘real world devices’
• Sensors record analog signals which are then converted to digital signals for processing in the microprocessor. The processor’s digital output can then be converted to analog signals again. 

Analog input sensors

• Magnet
• Touch
• Turn
• Motion
• Light
• Button

Transducers as input

• A transducer is a device which converts one type of physical property, quantity, or condition into another easily usable form. 

Advantages of transducers if the output signal is in electric form

• Ease of amplification
• Ease of integration and differentiation
• Ease of convertibility from analog to digital and vice versa
• Remote controllability and easy data transmission capability
• Compatibility with microprocessors and computers

When are transducers used?

• Transducers are used every time a signal has to be converted from one form to another. 
• Input = sensor (via transducer)
• Output = actuator (via transducer)

Feedback

• Feedback is the modification or control of a process or system by its results or effects, for example, in a fridge the thermometer provides feedback to the sensor that switches the refrigeration system on/off.

Processes that use feedback

• A missile tracking a moving target
• A heating system in a house
• A life-support system on a spacecraft
• Basically any situation that changes constantly that needs the system to react according to the new input

Ethical issue - Tagging prisoners

• Arguments for:
  • Allows non-dangerous criminals to move
  • Reduces number of people needed to be in prison
  • Allows for tracking at all times
• Arguments against:
  • Loss of freedom of movement
  • Could possibly be hacked to track innocent people
  • Tracking data could be sold off to make money

Ethical issue - Surveillance

• For
  • Allows for greater security
  • Could be used as effective evidence in court cases
  • Allows fewer people to have monitor others
• Against
  • Loss of privacy
  • Could be hacked and used for unintended purposes
  • Could be used to spy on people (drones)

Centralized control system

computing is done at a central location, using terminals that are attached to a central computer. The computer itself may control all the peripherals directly (as long as they are physically connected), or they may be attached via a terminal.

Distributed control system

components located on networked computers communicate and coordinate their actions by passing messages. The components interact with each other in order to achieve a common goal.

Advantages and disadvantages of centralized

• Advantages:
  • Easier to administrate
  • More control
• Disadvantages:
  • If the main sensor/controller fails, the whole system fails

Advantages and disadvantages of distributed

• Advantages:
  • Quicker access
  • Shared load
  • Response more specific to environment
• Disadvantages:
  • Much more expensive to have multiple controllers/sensors
  • Much more complex than a centralized system

Autonomous agents

software entities that carry out some set of operations on behalf of a user or another program with some degree of independence or autonomy, and in so doing, employ some knowledge or representation of the user’s goals or desires.

Features of agents - autonomy

• Agents activate alone for a task and are not invoked for a task
• Agents can select the task themselves (based on priorities or goal-directed search) without human intervention

Features of agents - reactive behavior

Agent senses the environment in which it is and decides what to do, reacting on its perceptions.

Features of agents - concurrency / sociality

Agents can interact with other agents through communication, in different modes, coordination, cooperation, and competition

Features of agents - persistence

• The code describing an agent runs continuously like a process, and it is not executed on demand

Analog data

Data which are recorded continuously

Features of autonomous agents

• Persistance
• Communication / sociality
• Reactive behavior
• Autonomy