GNVQ Advanced IT - Unit 2

Develop a control system

Requires students to produce a schematic diagram of a control system which includes two types of sensors and output devices, and to construct a process control system with a control procedure according to a given specification.

1.  explain and give examples of control systems
2. select components suited to a given specification
3. produce a schematic diagram of the system
4. create a control sytem
5. construct a control system according to the given specification
6. test the system for effectiveness and suggest improvements to the system

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Control systems: environmental control, process production control, quality control, security, transport systems, robotic production systems.

Components: sensors (heat, light, video, sound, proximity, contact), processors, process control procedure, output devices (heater, light, sound, fan, actuator), interconnecting devices

Specifications: input, tolerances, responses, costs, output, type of feedback

Schematic diagram: environment definition, sensors, processor, output device, feedback

Control procedure: input, decision, process, output. feedback loop

Test: alterations to control procedure (sensing rate, range limits, rate of output), change in sensitivity of sensors, use of different sensors

Effectiveness: comparative cost, speed of response, accuracy, comparison with alternatives, efficiency

Suggestions for improvement: use of different devices, change in feedback, alterations to sensitivity, modifications to software, modifications to situation or object

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A schematic diagram of the system including two types of sensor and two types of output devices.

A control system and a control procedure constructed by the student according to a specification given.

Notes showing that the student has :
 

• tested the system for effectiveness, covering the range
• explained all the uses of the process control systems ranged, with at least one example of each
• selected components suited to a given specification
• suggested appropriate improvements to the system

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Environmental control (PC1 and PC5 range) for example fridge temperature, greenhouse conditions, lighting controls.

Process production control (PC1 and PC5 range) for example control systems used in the manufacture of cars or domestic electrical good.

Quality control (PC1 and PC5 range) for example measuring the diameter of bolts or checking table tennis balls for size.

Security (PC1 and PC5 range) for example automated video camera systems or the control of physical access.

Transport systems (PC1 and PC5 range) for example movement of items on a production line, traffic lights and automated rail systems.

Robotic production systems (PC1 and PC5 range) using robotic devices to undertake work which is unsuitable for inefficient for humans to undertake, eg. moving radio-active material or spraying new cars.

Control procedures (PC4) the program created to operate a process control system.  The procedure is designed to read input data, process the data and send output signals according to preset rules, eg. read light level, compare with limit set, adjust output if necessary.

Tolerance (PC2 range) the set level, which if exceeded should result in some control action.

Response (PC2 range) the output actions of a system when set tolerances are exceeded.

Feedback (PC2 range) the process where part of an output is fed back into the input to enable action to be taken to increase or reduce the output.  Positive feedback results in increased output whereas negative feedback results in reduced output.  The operation of a sensor is generally not considered feedback.

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Control systems in everyday use include: TV/video remote controls, door opening devices, rail ticket machines.  Other systems include: lawn/greenhouse watering devices, garage door opening, greenhouse temperature, humidity and UV light control, security alarms and lighting controls. 

This unit should be integrated with Unit 1.1 Investigate industrial and commercial IT systems