Unit 46 Plant and Process Control


Unit 46:

Plant and Process Control


Unit code:
L/601/1435

QCF level:
5


Credit value:
15






Aim

This unit aims to develop learners’ understanding of time and frequency domain analysis of plant and process control systems and the use of controller designs to achieve specified system performance.

Unit abstract

This unit will develop learners’ understanding of the limitations of standard controllers and the use of more complex control schemes.

The first learning outcome will enable learners to recognise the characteristics of first and second order control systems and to analyse their response to step and ramp inputs. Learners are introduced to closed loop transfer functions and proportional/integral/derivative control actions. They will then apply this knowledge to analyse the requirements and design a control system in the time domain.

Learners are introduced to the response to a sinusoidal input and the conditions for system stability. They will analyse the requirements and design a control system in the frequency domain. Finally, learners will investigate the need for, and the use of, multi-loop and complex control systems.

Learning outcomes

On successful completion of this unit a learner will:

1       Be able to predict the dynamic and steady state response of an engineering system

2       Be able to design a control system in the time domain to a specified performance requirement

3       Be able to design a control system in the frequency domain to meet a specified performance requirement

4       Understand the need for and use of multi-loop and complex control systems.

Unit content

1      Be able to predict the dynamic and steady state response of an engineering system

Representation: first and second order differential equation models of simple engineering systems; standard form of equation; determine transfer functions from differential equation models

Analysis: output response to step and ramp inputs; dominant response

Specification and identification: gain; time constant; damping ratio; overshoot; natural and damped frequencies; rise time; settling time

2      Be able to design a control system in the time domain to a specified performance requirement

Closed loop: block-diagram manipulation; closed-loop transfer function; dynamic response; steady state response

Specification: dominant response; rise time; settling time; steady state error; overshoot

Controllers: review of the effects of P, I and D actions, parameter adjustment and tuning; approximate digital algorithm representation; sampling rate

Design: dynamic and steady state requirements; controller configuration; choice of actions; controller coefficient values; tuning; entry point of disturbances

3      Be able to design a control system in the frequency domain to meet a specified performance requirement

Frequency response: response to sinusoidal input; phase; gain; Bode frequency response plot; first order and second order systems; cascaded higher order; transport lag

Stability: gain and phase margins for simple systems; effect of P, I and D actions

Specification: steady-state error; gain and phase margins; bandwidth; link to time domain requirements

Design: dynamic and steady-state requirements; controller configuration; choice of actions; controller coefficient values; tuning

4      Understand the need for and use of multi-loop and complex control systems

Single-loop, three-term control: limitations; controllability; entry point of disturbances; changes in system dynamics; non-linear gain; multi-loop systems; interactions; de-tuning; averaging control

Multi-loop: ratio; cascade; feed forward; split range; hi-lo select; SCADA systems Advanced control: gain scheduling; self-tuning; fuzzy; predictive; Smith predictor

Learning outcomes and assessment criteria




Learning outcomes
Assessment criteria for pass


On successful completion of
The learner can:


this unit a learner will:










LO1 Be able to predict the

1.1
determine transfer functions from differential equation


dynamic and steady state


models


response of an engineering

1.2
manipulate first and second order transfer functions into


system





standard form and extract standard coefficients









1.3 determine output response to step and ramp inputs








LO2 Be able to design a control

2.1
manipulate transfer functions and determine closed-


system in the time domain to


loop transfer function


a specified performance

2.2
determine closed-loop dynamic and steady state


requirement





parameters









2.3
design a controller to meet given performance criteria




2.4
assess the effect of controller settings on steady state





and dynamic response







LO3 Be able to design a control

3.1
examine response of systems to sinusoidal inputs and


system in the frequency


plot Bode frequency response plots


domain to meet a specified

3.2
determine frequency response of higher order systems


performance requirement










3.3
predict stability and time domain performance of a





closed loop system from open loop frequency response




3.4
design a controller to meet given performance criteria




3.5
assess the effect of controller settings on frequency and





time response







LO4 Understand the need for and

4.1
identify the limitations of PID control in ensuring


use of multi-loop and


effective control in some situations


complex control systems

4.2
investigate alternative control strategies








4.3 investigate and review some advanced control strategies.










Guidance
Links

This unit links to Unit 1: Analytical Methods for Engineers and Unit 2: Engineering Science prior to this unit.

Essential requirements

A range of laboratory rigs, test equipment and appropriate software packages will need to be available to support practical investigations.

Employer engagement and vocational contexts

Centres should try to work closely with industrial organisations in order to bring realism and relevance to the unit. Visits to one or two relevant industrial or commercial organisations to review plant control systems will be of value to enhance and support learning.

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