unit 15 electrical, mechanical, hydraulic and pneumatic ... · automated machines used by industry...

ocr.org.uk/engineering

2016 Suite

Cambridge TECHNICALS LEVEL 3

ENGINEERINGUnit 15

Electrical, mechanical, hydraulic and pneumatic control F/506/7281

Guided learning hours: 60VERSION 4 -June 2017 black line indicates updated content

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© OCR 2017 Unit 15: Electrical, mechanical, hydraulic and pneumatic control

LEVEL 3

UNIT 15: ELECTRICAL, MECHANICAL, HYDRAULIC AND PNEUMATIC CONTROL F/506/7281 Guided learning hours: 60

Essential resources required for this unit: none This unit is internally assessed and externally moderated by OCR.

UNIT AIM Automated machines used by industry are operated by systems of control, which include electrical, mechanical, hydraulic and pneumatic control – this requires engineers to have a sound understanding of the processes and theory which underpin the operation of these machines. The aim of this unit is for learners to develop a foundation of knowledge and understanding of how these control systems work. Learners will gain an understanding of mechanisms used in control systems, and how their design can deliver the desired motion and performance. They will be able to develop their knowledge of electric motor types commonly used in automation control, and how their construction relates to output characteristics. They will gain an understanding of simple hydraulic control systems, including valves and actuators, and a basic understanding of fluid transmission. They will gain an understanding also of simple pneumatic control systems.


TEACHING CONTENT The teaching content in every unit states what has to be taught to ensure that learners are able to access the highest grades. Anything which follows an i.e. details what must be taught as part of that area of content. Anything which follows an e.g. is illustrative, it should be noted that where e.g. is used, learners must know and be able to apply relevant examples in their work, athough these do not need to be the same ones specified in the unit content. For internally assessed units you need to ensure that any assignments you create, or any modifications you make to an assignment, do not expect the learner to do more than they have been taught, but must enable them to access the full range of grades as described in the grading criteria. Please note – if learners are completing this unit as part of the Extended Diploma qualification they will be required to complete the synoptic unit 25: Promoting continuous improvement. Before your learners complete the assessment of this unit, you must refer to the specification and model assignment requirements for unit 25, so if applicable you can ensure learners gather the appropriate feedback on their own performance and performance of the system, process or artefact that they may have produced in this unit.

Learning outcomes Teaching content

The Learner will: Learners must be taught:

1. Understand the mechanical elements of control systems

1.1 motion, i.e. • linear motion (defined as position or speed i.e. m or m/s) • rotary motion (defined in angular position/speed i.e. rad or rad/s) • intermittent or continuous motion

1.2 common mechanical elements for producing linear and rotary motion. i.e. • shafts • slides • four bar linkages

1.3 mechanisms, i.e. • those which convert rotary to linear motion i.e. o rack and pinion o walking beam

• those which convert linear to rotary motion i.e. o piston and crank

• those which produce intermittent motion i.e. o Geneva spur o ratchet and pawl

• how equations of motion and dynamic forces relate to moving systems

1.4 balance of rotating masses and effects of imbalance (e.g. vibration, component damage, noise, accelerated wear)

1.5 power losses due to mechanical friction


2. Understand the electrical elements of control systems

2.1 the role of electrical sensors and actuators in a control system (e.g. sensor detects an object’s position on an assembly line; actuator controls movement of an arm to pick up the object)

2.2 common types of electrical actuators i.e. • linear - solenoid • rotary i.e. o motor o servo motor o stepper motor

2.3 motor types i.e. • AC (e.g. synchronous and asynchronous) • DC (e.g. brushed, brushless)

2.4 motor control, i.e. • servo motors using pulse width modulation • AC motors using variable frequency inverters

2.5 energy losses and reduced efficiency in electrical actuators, i.e. • friction • resistance in windings • eddy current • hysteresis

2.6 motor selection for given output requirements i.e. • power • speed • torque • torque/speed requirements • duty cycle




3. Understand simple hydraulic systems

3.1 power sources for hydraulic systems, i.e. • pressurised non-compressible fluids (mineral and water-based

oils) • pumps, i.e.:

o positive displacement pumps (hydrostatic) o fixed or variable displacement pumps (hydrodynamic)

3.2 valves and actuators for hydraulic systems, i.e. • hydraulic control valve types i.e.

o poppet valves o spool valves o pilot valves o check valves

• hydraulic actuator types, i.e. o linear actuators o single acting o double acting o multi stage linear actuators o rotary actuators

3.3 fluid transmission in hydraulic systems, i.e. • graphical representation of hydraulic circuits to relevant

standards (e.g. ISO5599) • transmission losses and implications for pipe sizing in hydraulic

systems • transmission fluid flow, i.e.

o Laminar flow o Reynolds number o flow velocity o pressure rating o transmission volume o working volume

• how power losses result in heating of fluid and the consequences

Learning Outcomes Teaching Content





4. Understand simple pneumatic systems

4.1 compressors for pneumatic systems, i.e. • dynamic (e.g. centrifugal, axial) • positive displacement (e.g. rotary, reciprocating)

4.2 valves and actuators for pneumatic systems, i.e. • pneumatic control valve types, i.e.

o poppet valves o spool valves o rotary valves o check valves

• pneumatic actuator types, i.e. o linear actuators o single acting o double acting o rotary actuators

4.3 fluid transmission in pneumatic systems, i.e. • Graphical representation of pneumatic circuits to relevant

standards (e.g. ISO5599) • transmission fluid flow, i.e.

o Laminar flow o Reynolds number o flow velocity o pressure rating o gas law o constant pressure

• transmission losses and implications for pipe sizing in pneumatic systems

4.4 recognise implications of moisture build up in pipe networks and need for drains


GRADING CRITERIA LO Pass Merit Distinction The assessment criteria are the Pass

requirements for this unit.

To achieve a Merit the evidence must show that, in addition to the Pass criteria, the candidate is able to:

To achieve a Distinction the evidence must show that, in addition to the pass and merit criteria, the candidate is able to:

1. Understand mechanical elements of control systems

P1: Explain the application of different types of motion in control systems.

M1: Explain the importance of balancing rotating masses.

D1: Demonstrate how power loss occurs in a specific control system due to mechanical friction.

P2: Describe common mechanisms used in control systems. P3 Describe how equations of motion and dynamic forces relate to moving systems. *Synoptic link - Unit 2 Science for engineering

2. Understand the electrical elements of control systems

P4: Explain the role of electrical sensors and actuators in a control system.

M2: Explain energy losses and reduced efficiency in electrical actuators.

D2: Analyse how servo motors and AC motors can be controlled.

P5: Describe common types of electrical actuators.

P6: Describe a range of electric motor types.

M3: Justify the selection of an electric motor for given output requirements.


LO Pass Merit Distinction

3. Understand simple hydraulic systems

P7: Describe power sources for hydraulic systems.

M4: Analyse fluid transmission in hydraulic systems.

D3: Evaluate the suitability of hydraulic and pneumatic systems for different control systems.

P8: Explain the application of valves and actuators in different hydraulic systems.

4. Understand simple pneumatic systems

P9: Describe power sources for pneumatic systems.

M5: Analyse fluid transmission in pneumatic systems. *Synoptic link - Unit 2 Science for engineering P10:

Explain the application of valves and actuators in different pneumatic systems.


*SYNOPTIC ASSESSMENT AND LINKS BETWEEN UNITS When learners are taking an assessment task, or series of tasks, for this unit they will have opportunities to draw on relevant, appropriate knowledge, understanding and skills that they will have developed through other units. We’ve identified those opportunities in the grading criteria. Learners should be encouraged to consider for themselves which skills/knowledge/understanding are most relevant to apply where we have placed an asterisk.

ASSESSMENT GUIDANCE LO1: Understand mechanical elements of control systems Learners should investigate the mechanical aspects of control systems. Teachers may be able to provide suitable examples for learners to investigate. P3 provides an opportunity for learners to draw upon knowledge from Unit 2. LO2: Understand the electrical elements of control systems Learners should investigate the electrical aspects of control systems. Teachers may be able to provide suitable examples for learners to investigate. LO3: Understand simple hydraulic systems Learners should investigate aspects of control systems employing hydraulic power sources, valves, actuators and transmission. Teachers may be able to provide suitable examples for learners to investigate. LO4: Understand simple pneumatic systems Learners should investigate aspects of control systems employing pneumatic power sources, valves, actuators and transmission. M5 provides an opportunity for learners to draw upon knowledge from Unit 2. Teachers may be able to provide suitable examples for learners to investigate. Feedback to learners: you can discuss work-in-progress towards summative assessment with learners to make sure it’s being done in a planned and timely manner. It also provides an opportunity for you to check the authenticity of the work. You must intervene if you feel there’s a health and safety risk. Learners should use their own words when producing evidence of their knowledge and understanding. When learners use their own words it reduces the possibility of learners’ work being identified as plagiarised. If a learner does use someone else’s words and ideas in their work, they must acknowledge it, and this is done through referencing. Just quoting and referencing someone else’s work will not show that the learner knows or understands it. It has to be clear in the work how the learner is using the material they have referenced to inform their thoughts, ideas or conclusions. For more information about internal assessment, including feedback, authentication and plagiarism, see the centre handbook. Information about how to reference is in the OCR Guide to Referencing available on our website: http://www.ocr.org.uk/i-want-to/skills-guides/.

http://www.ocr.org.uk/i-want-to/skills-guides/


MEANINGFUL EMPLOYER INVOLVEMENT - a requirement for the Foundation Diploma, Diploma and Extended Diploma (tech level) qualifications The ‘Diploma’ qualifications have been designed to be recognised as Tech Levels in performance tables in England. It is a requirement of these qualifications for centres to secure for every learner employer involvement through delivery and/or assessment of these qualifications. The minimum amount of employer involvement must relate to at least one or more of the elements of the mandatory content (this unit is a mandatory unit in the Automation, Systems and Control pathway). Eligible activities and suggestions/ideas that may help you in securing meaningful employer involvement for this unit are given in the table below. Please refer to the Qualification Handbook for further information including a list of activities that are not considered to meet this requirement.

Meaningful employer engagement Suggestion/ideas for centres when delivering this unit 1. Learners undertake structured work-experience or work-

placements that develop skills and knowledge relevant to the qualification.

Placements with engineering firms working with production/manufacturing engineering and/or maintenance department, reviewing their system standards and or conformity for electrical/mechanical/hydraulic and pneumatic applications within the manufacturing operation.

2. Learners undertake project(s), exercises(s) and/or assessments/examination(s) set with input from industry practitioner(s).

A task set to design or re-design a hydraulic/ pneumatic system, to a given industry standard, in order that the hydraulic/pneumatic system is suitable for a given application.

3. Learners take one or more units delivered or co-delivered by an industry practitioner(s). This could take the form of master classes or guest lectures.

Lecture from a practicing production/manufacturing and/or maintenance engineer involved in control system design, development and testing. Content to include real examples of open/closed loop systems in practice and hydraulic/pneumatic valves and actuators.

4. Industry practitioners operating as ‘expert witnesses’ that contribute to the assessment of a learner’s work or practice, operating within a specified assessment framework. This may be a specific project(s), exercise(s) or examination(s), or all assessments for a qualification.

Review from a practicing production/manufacturing and/or maintenance engineer (or a manager with direct experience) of students’ designs for a hydraulic/pneumatic control system.

OCR is part of Cambridge Assessment, a department of the University of Cambridge.

For staff training purposes and as part of our quality assurance programme your call may be recorded or monitored. ©OCR 2015 Oxford Cambridge and RSA Examinations is a Company Limited by Guarantee. Registered in England. Registered office 1 Hills Road, Cambridge CB1 2EU. Registered company number 3484466. OCR is an exempt charity.

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unit 15 electrical, mechanical, hydraulic and pneumatic ... · automated machines used by industry...

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