2014 engg1200 pa signed

Doc I.D: 2014-ENGG1200-PC Version: 3.0

Date: 16/07/2014

ENGG1200 PROJECT A – AERIAL DEPLOYMENT

The Brief

This document is a client-specified brief. Supplementary information will be communicated through the Problem Solving Sessions and announced via Blackboard. If your design team requires further information or detail, please contact your project . Roles

Work submitted as part of this course must be designed and built entirely by engineering students enrolled in ENGG1200, Semester 2, 2014. Project leaders, tutors and university technicians can be used as consultants for specific information. Your team is required to engage in clarifying any or all of these specifications to deliver the project at the tender competition, being at Demonstration Day in Week 13. Safety

Part of this course requires you to manufacture and assemble components yourselves. Since this is a university project, the university has duty of care for your safety. You are therefore required to complete this work in the Student Technology Centre (STC) where university staff can supervise your work. No toxic or dangerous materials will be allowed. The determination of safe materials will be made by comparison to the Hazardous Substances List at http://www.uq.edu.au/ohs/hazardous-substances (The University of Queensland, 2014). This check must be submitted as part of Build Risk Assessment in the Preliminary Memo (due Week 4) and is required for approval prior to construction.

http://www.uq.edu.au/ohs/hazardous-substances


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CONTENTS 1 Introduction ................................................................................................................... 3

2 Aims .............................................................................................................................. 3

3 Design Specifications .................................................................................................... 4

3.1 Deliverables ............................................................................................................ 4

3.2 Supplied Equipment ................................................................................................ 4

3.2.1 Linear rail ......................................................................................................... 4

3.2.2 Motor and motor driver ..................................................................................... 5

3.2.3 Torque rod ....................................................................................................... 6

3.2.4 Mounting flange ............................................................................................... 6

3.2.5 Payload ............................................................................................................ 7

3.3 Overview of operation ............................................................................................. 7

3.4 Design Constraints .................................................................................................. 7

3.4.1 Mounting points ............................................................................................... 8

4 Models & Simulations .................................................................................................... 8

4.1 Structural Modelling ................................................................................................ 8

4.1.1 CAD CAM Interface specifications ................................................................... 8

4.2 Behavioural Modelling ........................................................................................... 10

4.2.1 Relevant physics: ........................................................................................... 10

4.2.2 Modelling and simulation tasks ...................................................................... 11

5 Build / Manufacture ..................................................................................................... 12

6 Material Selection ........................................................................................................ 12

7 Critical Design Review ................................................................................................ 12

8 Evaluation ................................................................................................................... 12

8.1 Equipment ............................................................................................................ 12

8.2 Testing procedure: ................................................................................................ 13

8.3 Design Objective Function .................................................................................... 13

8.3.1 Starting position above horizontal: ................................................................. 14

9 FAQs ........................................................................................................................... 15

10 Revision Status ........................................................................................................... 15

11 References .................................................................................................................. 16


Date: 16/07/2014

1 INTRODUCTION There are occasional instances in the commercial sector where there is a need to deliver an airborne “payload” over a barrier and into a specific location. Such instances might include needing to put out a raging forest fire, contain a nuclear accident in a reactor core or delivering food and equipment to civilians inside a guarded perimeter. In order to achieve such a trajectory an aircraft carrying the payload would need to come in at a predetermined speed and relatively low altitude and quickly alter its acceleration to launch the payload in a trajectory similar to that shown in Figure 1. Because this is a high risk manoeuvre the Defence Materiel Organisation (DMO) is seeking bids for the design of an Aerial Deployment System that can be attached to the undercarriage of an aircraft to achieve predefined trajectories. Your company has been asked to prepare a tender bid for the detailed engineering design.

Figure 1: Airbourne delivery trajectory

2 AIMS Each team is to design and build a working ‘proof of concept’ scale model to meet the design specifications listed below.


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3 DESIGN SPECIFICATIONS

3.1 Deliverables Each team will manufacture a proof of concept payload deployment mechanism (PDM). The PDM will include the following features:

1. A CNC machined ‘quick release’ plate to interface your model to the client’s linear actuator.

2. An arm, consisting of zero or more articulated sections. 3. A payload holder (which may be part of the arm). 4. Your team will write the controller input to specify the acceleration and deceleration

of the trolley. Teams will be provided with a $100 budget for procuring your design. Tax invoices will be required for reimbursement. Reimbursement will only be given for parts and materials used in the final design, within reason. Refer to the quality section of the marking criteria for marks allocated with minimising cost (Section 8.3).

3.2 Supplied Equipment The client will provide test equipment consisting of the following components:

1. Linear rail with sliding trolley 2. Motor and motor driver 3. Torque rod 4. Mounting flange 5. Payload

3.2.1 Linear rail The linear rail has a usable length of 3 m and is mounted at a height of 1.5 m. The friction coefficient is not specified. The maximum velocity of the trolley on the rail is 10 m/s and the belt can withstand accelerations of over 9 g. Photographs of the actual rail are shown in Figure 2, and videos of it in operation are available on the Blackboard Project A page.


Date: 16/07/2014

Figure 2: Linear rail (left) and the torsion bar assembly (right). View to the mounting flange end

3.2.2 Motor and motor driver The trolley is driven by a Sanyo-Denki 12 Nm stepper motor: model 103-H89222-6341. The datasheet is available on Blackboard. The motor will be driven at 240 Volts. Each revolution of the motor advances the trolley by 280 mm. Teams will interface to the motor by providing a .csv file containing two columns, the first being time values in milliseconds, and the second being corresponding target velocities in m/s. Velocity values can be either positive or negative. Times can be specified down to tenths of milliseconds if necessary. From testing the maximum achievable acceleration is expected to be approximately 10 m/s2. The velocity is effectively limited by the acceleration and length of rail. Motor control files must be submitted via the Blackboard assignment submission (under week 13 on the learning pathway) by 4:30pm on Monday the 27th of October, or the default profile will be loaded for your team on demonstration day. The default profile is: t(ms),v(m/s) 0,0 600,8 900,0


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3.2.3 Torque rod The torque rods are manufactured from high-tensile spring steel with a shear modulus of 79.29 GPa and a yield stress of 1500 MPa. The torsional yield stress is approximately 45 % of the tensile yield stress. The gauge length is 200 mm. Two diameters will be available for teams to choose from: 3 mm and 5 mm. As there are a limited number of torque rods, it is important that teams ensure that they do not plastically deform the torque rod. Teams are therefore asked to show calculations of maximum deflection for their design compared to the yield deflection or the rod. The rod will be measured after each test, and marks will be deducted if a team deforms the rod plastically.

3.2.4 Mounting flange A drawing of the torsion rod assembly (thumbnail shown in Figure 3 below) is available on the Blackboard Project A page. Note the pawl on the rear view that will allow the swing arm to twist the torsion bar in the clockwise direction from the equilibrium position only. See Section 4.1.1 for details of the quick release plate interface.

Figure 3: A drawing of the torsion bar assembly is available. Clock-wise from bottom: Isometric view, front view, side and read view


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3.2.5 Payload The payload shall be a standard size, type 1 or type 2 tennis ball. Specifications for this can be found at: http://www.itftennis.com/technical/publications/rules/balls/appendix-i.aspx

3.3 Overview of operation The trolley slides along the linear rail under the influence of the motor. The torque rod is mounted on the trolley. It is oriented horizontally, and perpendicular to the linear rail. One end of the torque rod is fixed against rotation. The other end of the torque rod engages with the mounting plate where the PDM is attached. Note that the test rig will be mounted in a right-handed fashion, i.e. the arm will hang on the right-hand side of the rail, facing the throwing direction. When the PDM rotates clockwise about the axis of the torque rod, the torque rod acts as a torsional spring, storing energy as the trolley accelerates and releasing energy when the trolley decelerates. This energy is to be used to launch the payload. When the PDM rotates counter-clockwise past the equilibrium position, the torque rod disengages at the fixed end, allowing the PDM to rotate freely without losing energy into the torsional spring.

3.4 Design Constraints The model must fit within the following constraints, as shown in Figure 4.

1. The PDM must protrude no wider than w = 120mm from the adaptor plate. 2. The PDM must extend no more than r = 500mm radially from the torsion pin at any

time. 3. The PDM, including quick-release plate, arm, payload holder and payload must

weigh no more than 3kg. 4. The projectile launch must be propelled exclusively by the energy of the linear

actuator. 5. The model must be safely and securely constructed.

These specifications are essential for safety reasons. Any models which do not meet these specifications will not be tested.

http://www.itftennis.com/technical/publications/rules/balls/appendix-i.aspx


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Figure 4: Design envelope for the quick release plate, arm and payload

3.4.1 Mounting points In addition to the quick release plate, one other mounting point on the test rig will be made available. A point on the trolley, but not attached to the torsion bar may be used as a ‘trigger’ mounting point. This point will be 150mm below and 150mm to the left of the centre of the quick-release plate interface, as shown in the drawing linked from Section 3.2.4. This mounting point is intended to actuate triggers only, and should not be used to absorb large forces such as stopping the motion of the swing arm.

4 MODELS & SIMULATIONS Tenders are expected to use models and simulations to inform the design process and assess the likely performance of their design.

4.1 Structural Modelling Teams will be required to model the quick release plate in CREO computer-aided-design software. Three students from the team should attend the three structural modelling workshops in week 7, 8 and 9, and submit their design files for manufacturing with a CNC mill.

4.1.1 CAD CAM Interface specifications Teams are to design and CNC mill their quick-release plate. The purpose of the quick-release plate is simply to connect your swing arm to a mounting flange on the test rig. CNC milled parts will be cut from aluminium blanks of 12 mm thickness and 75 mm diameter as shown in Figure 5 below. Note that the centre hole will allow an M6 bolt to pass through, which screws into a corresponding, but threaded, hole on the mounting flange. The centre bolt can be used to


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fasten your swing-arm to the quick release plate, but additional features will be required to transfer torque to the arm. The holes at 60mm pitch circle diameter (PCD) are to mate with metal pins. These pins are strongly affixed to the adapter plate on the test rig and these pins transmit torque from the adapter plate/torque rod assembly into your quick release plate. Teams must design and mill features on the plate to ensure the torque is transferred to the arm, and the arm is secured. Note that the alignment of the 60 mm PCD holes and other features will determine the equilibrium angle of the arm.

Figure 5: Interface dimensions. +Z axis is out of the page Please Note:

• Teams must comply with the axis indicated as the parts are manufactured in fixtures aligned with these axes.

• Tool Path must be approx. 150Kb in file size per side (maximum machining time for both sides is 2hrs)

• Tool is 5mm end mill • Vericut screen shot showing axis is required in jpg format and submitted with tool

path file. File Name Format: (Project)_(student email).tap e.g. MINE_S123456.tap (Project)_(student email).jpg e.g MINE_S123456.jpg


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Your files are to be submitted using the specified formats via electronic submission (refer to Blackboard for more details). All components should be available for collection around 5 working days after the submission deadline. Non-compliant submissions will be returned for resubmission with 10% penalty. Designs with excessive non-functional features, decorations and incorrect axis will be deemed non-compliant.

4.2 Behavioural Modelling In order to achieve the aims of the project, teams will need to model and simulate the behaviour of their system.

4.2.1 Relevant physics: The following equations may be a useful starting place for modelling your system. Energy in a spring:

The energy, U, in Joules, stored in a torsion spring is:

U = 12κθ2 [1]

where:

κ is the spring constant, and θ is the angular displacement (radians)

Torque and angle of twist:

θ = T.LG.Ip

[2]

where:

θ is the angular displacement (radians), L is the length of the object the torque is being applied to, T is the applied torque (Nm), G is the shear modulus (GPa), and Ip is the torsion constant for the section

Visit http://www.engr.colostate.edu/~dga/mech325/chapter_summaries/JUVINALL_EQS_CH12.pdf (Juvinall & Marshek, 2000) for more details.

http://www.engr.colostate.edu/~dga/mech325/chapter_summaries/JUVINALL_EQS_CH12.pdf


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Linear and angular motion:

Linear motion Angular motion 𝑣𝐹 = 𝑣𝐼 + 𝑎𝑡 [3] 𝜔𝐹 = 𝜔𝑖 + 𝛼𝑡 [7]

𝑑 =12

(𝑣𝐹 + 𝑣𝐼)𝑡 [4]

𝜃 =12

(𝜔𝐹 + 𝜔𝐼)𝑡 [8]

𝑑 = 𝑣𝐼𝑡 +12𝑎𝑡2

[5] 𝜃 = 𝜔𝐼𝑡 +

12𝛼𝑡2

[9]

𝑣𝐹2 = 𝑣𝐼2 + 2𝑎𝑑 [6] 𝜔𝐹2 = 𝜔𝐼

2 + 2𝛼𝜃 [10] where:

𝑣𝐹 is the final velocity (m/s), 𝑣𝐼 is the initial velocity (m/s), d is the displacement (m), a is the acceleration (m/s), t is the time (s), 𝛼 is the angular acceleration (rad/s2), and 𝜔𝐹 is the final angular velocity (rad/s), 𝜔𝑖 is the initial angular velocity (rad/s), and 𝜃 is the angular displacement (rad).

4.2.2 Modelling and simulation tasks In order to achieve the aims of the design, teams should model and simulate key elements of the system as shown in Table 1 below. Table 1: Modelling and simulation requirements Rod deflection Present calculations of the yield deflection for the torsion rod. Physical System Present modelling results and key equations showing response of the

system to inputs. This should include graphs showing: Projectile trajectories for all arm/payload holder configurations. Projectile distance for several values of maximum acceleration. Maximum rod deflection for several acceleration profiles.


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5 BUILD / MANUFACTURE The university will supply:

• A linear rail, motor and motor driver • A trolley which moves along the rail • The torsion rod and rod mount. • The flange that is fitted to the torsion rod. • Payload – a standard tennis ball. • Barrier – a moveable barrier 1.5m high

Each group will be required to do the following:

• Design and build their own payload delivery system including any links and the payload holder.

• Design and submit for manufacturing, a quick-release plate which will interface with the torsion rod flange. Design their own quick-release plate using computer aided design (CAD) software. The quick release plate will be machined on the University’s computer numerical controlled milling machines (CNC). The quick-release plate will interface your PDM onto the client’s adapter flange.

• Supply control input to the motor driver (protocol to be specified)

6 MATERIAL SELECTION Students have freedom to choose materials for their parts. The quick-release adaptor plate will be CNC machined from aluminium. Material selections and selection criteria should be justified in the final report.

7 CRITICAL DESIGN REVIEW In week 10 teams will be required to demonstrate progress in their design. This review is worth 5% of your final grade and the criteria will be advised.

8 EVALUATION Designs will be tested in week 13. The site will be an open sportsground at UQ.

8.1 Equipment The test rig consisting of a linear rail, motor and motor driver will be set up at the site. Specifications for the height and length of the rail are provided in Section 3.2.


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8.2 Testing procedure: 1. Before the presentation, the barrier distance will be chosen by the team and put in

place. 2. The team will be required to provide the control signal to the stepper motor driver. 3. The team will attach their model to the test rig and load the payload. 4. A tutor will assess the safety, robustness, dimensions and weight of the model and

connection before testing. 5. Once the model is attached it must behave independently. That is, there shall be no

physical interaction between the model and team members. 6. Repeat runs will be completed to confirm the repeatability of the launch.

8.3 Design Objective Function Teams should maximise the launch efficiency (25%), land the payload as close as possible behind the barrier (15%), achieve high repeatability of launch (20%) and have a high build quality (40%). Teams will be able to set the distance to the barrier. The barrier height will be 1.5m. The various dimensions used in evaluation of performance are shown in Figure 6.

Figure 6: Testing and evaluation specifications The specific weightings of the marking criteria are defined as:

demonstration mark = 0.25 �𝑘1𝑙2𝑙1� + 0.15 �𝑘2

𝑙2𝑙3� + 0.2𝑅 + 0.4𝑄 [11]

where: l1, l2, l3 are the acceleration length (m), the flight length (m) and the distance past the barrier (m) respectively, k1, k2 are scaling factors such that the best performing throw receives 100% of the available mark for that term, h (m) is the height of the barrier, Q is the build quality, and R is repeatability.


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See the FAQs (Section 9) for a discussion of how l1 will be calculated. Q = Build Quality:

The build quality mark incorporates many important but subjective factors such as: • Simplicity of design • Fitting/Interface of CNC machined part • General craftsmanship (e.g. are all sharp edges removed, is the prototype well

finished) • Innovation and creativity, i.e. unique solutions. • Cost effective design

R = Repeatability:

• Accuracy of subsequent deployments

8.3.1 Starting position above horizontal: As shown in Figure 4 and Figure 6, the design intent of this brief is for teams to begin with the swing-arm hanging below the rail. Starting with the arm above the rail and exploiting the extra initial gravitational potential energy is an innovative solution, however the design objective function in Section 8.3 does not allow for fair marking of these designs. As such, a minimum value of 0.4 metres (the approximate equivalent rail length required to build up equivalent energy) will be used in the marking of these designs.


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9 FAQS Common project-specific questions and answers are provided in Table 2 below. Table 2: Project C Q&A Item # Question and Answer

1

Q: Can I get multiple parts manufactured using the University’s CNC machines? A: No. We only have capacity to manufacture one part per team. Please purchase materials and use the tools in the STC to manufacture the rest yourselves.

2

Q: Are we just aiming to fling a tennis ball as far as possible?

A: Yes and no. As described in section 8 you will get maximum marks if you minimise the length of track you use, land your payload as close as possible behind the barrier AND maximise the distance that you fling the ball.

3

Q: If I accelerate the trolley forwards and then backwards again before releasing the payload, does that mean that my acceleration length (𝑙1) in the marking criteria will be calculated as zero?

A: No. The acceleration length, 𝑙1, will be calculated as the sum of all stepper motor steps in the forward direction. Steps in the backward direction will not be added (nor subtracted).

4

Q: Can I use the figures in the brief in my reports? A: Yes, there is no need to re-invent the wheel. It is extremely important that you reference where you got the figures though. As with anything in your report that isn’t your own work, if you don’t reference it, it could be considered

10 REVISION STATUS The project brief revision status is shown in Table 5. The table will be updated following major document revisions, approval and issue. Table 3: Revision status Rev Description Date of Issue: By: 1.0 2013 project brief re-formatted into new

style. 15/07/14 MA

1.1 Equation variables update, citations added 19/07/14 MS


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11 REFERENCES The University of Queensland. (2014). Hazardous Substances. Retrieved July 16, 2014,

from The University of Queensland: http://www.uq.edu.au/ohs/hazardous-substances

2014 engg1200 pa signed

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