fyp report - eoin lees
TRANSCRIPT
“Development of a condition monitoring tool for composite wind
blades”
18/03/2016
Eoin Lees
09004826
Computer Aided Engineering and Design
ii
“Development of a condition monitoring tool for composite wind
blades”
18/03/2016
Eoin Lees
09004826
Computer Aided Engineering and Design
Dr. Anthony Comer (Supervisor)
Final Year Project report submitted to the University of Limerick, (March) (2016)
I declare that this is my work and that all contributions from other persons have been appropriately
identified and acknowledged.
Abstract
The current method for monitoring wind turbines from the ground involves mounting a stationary
device to the base of a wind turbine tower. The issue with this is due to the constantly changing wind
direction the nacelle turns out of range of the device. The aim of this project is to design a device to
monitor the turbine blades and track the nacelle as it turns with the wind.
A design process was followed in order to come up with a design that worked. First, a design
specification was decided upon. Then concepts were developed to match this specification. Next, a
final design was chosen and built as a prototype for testing to work out and redesign for any issues
that arose. Lastly, a program was developed to track the yawing of the wind turbine with the wind.
The initial design featured a magnetic wheel design. Following testing and experimentation this design
was changed to a rail dependent design which supported the device through legs on the ground. The
development of the tracking program led to the specification of a stepper motor, which then led to a
redesign of the track and supporting bearings.
Further development is needed to complete the design in order for the unit to function. It needs to
have inbuilt computer, motor and battery, along with a cover attached and some form of
weatherproofing.
The prototype is built and will serve as a test rig to develop the nacelle tracking software needed to
progress this project to a complete stage.
iv
Acknowledgements
I would like to thank my supervisor Dr. Anthony Comer for all his invaluable help and advice
throughout the year working on this project.
Also I’d like to thank Adrian McEvoy for helping me get laboratory space and facilitating testing.
I’d like to thank Gerard Lees for getting the prototype built and working through the final design with
me.
I’d like to thank John Cunningham for helping me finalise the design of the prototype.
Finally, Meghan Devlin for providing me with advise for writing and proof reading the report.
v
Nomenclature
E Young’s Modulus GPa Giga Pascal’s
L Length mm Millimetres
M Mass Kg Kilograms
ρ Density kg/m^3 Kilograms per metre cubed
vi
Table of Contents
Abstract .................................................................................................................................................. iii
Acknowledgements ................................................................................................................................ iv
Nomenclature ......................................................................................................................................... v
Introduction ............................................................................................................................................ 1
A Brief Explanation of the Project ....................................................................................................... 1
Schematic ............................................................................................................................................ 3
Objectives ............................................................................................................................................... 5
Constraints and limitations ................................................................................................................. 5
Literature Review .................................................................................................................................... 6
Design ...................................................................................................................................................... 8
Design Process .................................................................................................................................... 8
Initial Stages .................................................................................................................................... 8
Design specification ........................................................................................................................ 8
Concept generation ...................................................................................................................... 10
Concept down selection ................................................................................................................ 13
SolidWorks Drawing ...................................................................................................................... 13
Phase 1 – Magnetic Wheel Design .................................................................................................... 14
Phase 2 – Chassis and bearing block Design ..................................................................................... 16
Chassis Design ............................................................................................................................... 16
Bearing Block Design ..................................................................................................................... 23
Material Selection ............................................................................................................................. 24
Phase 3 – Rail and Roller Design ....................................................................................................... 27
Shaft Design .................................................................................................................................. 30
Phase 4 - Prototype ........................................................................................................................... 31
Phase 5 – Control system design ...................................................................................................... 32
Phase 6 – Final Drawings................................................................................................................... 35
Assembly ....................................................................................................................................... 35
Experimenting and Testing ................................................................................................................... 36
Magnets ............................................................................................................................................ 36
Procedure: ..................................................................................................................................... 36
Results ........................................................................................................................................... 37
Conclusions ................................................................................................................................... 37
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Prototype .......................................................................................................................................... 38
Procedure ...................................................................................................................................... 39
Results ........................................................................................................................................... 39
Conclusion ..................................................................................................................................... 40
Nacelle Tracking ................................................................................................................................ 40
Procedure ...................................................................................................................................... 40
Conclusions ................................................................................................................................... 40
Results ................................................................................................................................................... 41
Conclusions ........................................................................................................................................... 42
Recommendations / Future work ......................................................................................................... 43
References ............................................................................................................................................ 44
Appendix A .............................................................................................................................................. a
Appendix B .............................................................................................................................................. a
Appendix C .............................................................................................................................................. a
1
Introduction
A Brief Explanation of the Project
A design process was followed in order to achieve the best solution to the problems posed. Initial
research looked into what currently exists for this type of application and whether those solutions
could be used to deal with this issue. Using a design process set out in an Introduction to Design
Process, a set of design specifications was come up with (Wallace & Clarkson 1999). (Appendix A)
Having the design specifications, concepts were then compiled. These concepts were scrutinised and
finally one concept was down-selected.
This concept was worked with on an iterative basis until finally working drawings were produced.
These drawings were then sent to the fabricator and the prototype was made.
In the meantime, a motor was found and plans to attach it to power the rig were put in place.
The prototype was tested proving the mechanical design concept.
The Project
Wind turbines are becoming more common than ever in Ireland. There are currently 228 windfarms
in Ireland and that is planned to increase. The main issue with wind turbines regarding power
generation is that electricity cannot be stored. Therefore, the turbines need to perform at time of
most need, i.e. evenings and morning. The efficiency of the turbines is of utmost importance; the angle
of the tower towards the wind and the condition of the blade are vital to this efficiency. Furthermore,
the need to monitor these details is very important. The tool that is currently used is able to monitor
the blades at a fixed position. However, the towers by their nature are constantly rotating to face
towards the wind direction on any particular day. In order to get an accurate understanding of the
motions of the blades and nacelle, they need to be monitored for a period of 8 hours or so. This brings
in the need for the device that is able to move along the base of the tower and is also to track the
nacelle as it moves. Thus, this project aims to create a design to fulfil this need.
The design was worked on for a number of weeks. Each issue that was encountered needed
redesigning. This iterative design approach led to a design that has been thought out fully.
2
The image tracking was looked into by using Simulink for Mat lab. This program uses the input from
the webcam to set limits for the unit. The program then sends a signal to the motor if this is to pass
these limits allowing it to move to a position that allows it to work.
The design come up with is the rig that once completed will be mounted with a payload of monitoring
equipment. For the purpose of this design it was decided that the payload would be 10kg.
The design was completed on campus in the University of Limerick. The prototype was manufactured
in Limerick and assembled in Newport Co. Tipperary before transportation to the University of
Limerick for testing.
The report follows the design of the tool from start to finish, in chronological order. The sections of
the report are as follows.
First, the literature review sets out the research that was undertaken and underpins the need for the
design.
Second, the main body of the report follows the design process. This portion of the report goes into
detail about all the tools and methods used, and about the issues that were encountered.
Sections of the main body are laid out in the following order:
Design process
Drawings
Prototype build
Video tracking software
Motor addition
Mini computer
Third, the results section displays the finished product. This section is an overview of what was
designed and what was developed through the course of this project.
Fourth, the conclusions section goes into detail about what was learned from the process and what
further work will need to be done in order for the design to be completed.
Last, the appendices contain all the finished drawings and assemblies. This section also contains all
material data sheets and design details relevant to certain parts.
3
Schematic
The following schematic labels all parts and terminology used in this report. All parts will be referred
to as they are named in this figure. The Legend is shown in Table 1.
Figure 1: Schematic 1
Figure 2: Schematic 2 Figure 3: Schematic 3
4
Table 1: Schematic Legend
Number Description
1 Chassis
2 Bearing Block
3 M6 Bolt
4 Wheel Shaft
5 Bearing
6 Magnetic Wheel
7 Roller Shaft
8 Roller
9 External Circlip
10 Internal Circlip
11 Motor
12 Motor Gear
13 Roller Holder
14 Raspberry Pi
15 Battery Pack
5
Objectives
To develop a condition monitoring tool for composite wind blades.
To develop a portable lightweight device that can be mounted on any wind turbine.
To design a method of allowing the device to move along the tower.
To design software to allow the tool to track the yawing of the nacelle.
Constraints and limitations
A number of issues arose leading to difficulties completing the design. One issue that arose was that
time taken to finalise drawings was underestimated, thus leading to a delay in the drawings being sent
to be manufactured. Following this, the manufacturing process took longer than expected, resulting
in the final prototype only being assembled on week 7 of the university calendar. Finally, time
constraints lead to lack of time to become competent at using the Simulink software for image
tracking.
6
Literature Review
Wind energy is a fast growing industry in Ireland and worldwide. Wind energy provided 15.5% of Irish
electricity in 2012 (Association, 2016)
This growth has been driven by the Irish government’s plan to increase renewable energy to 40% by
2020, as outlined by an EU binding target (Irish Wind Energy Association 2016).
Wind power, by its nature, is dependent on the weather. Wind Turbines are dependent on wind
conditions not being too fast or too slow; normal operating range is from 8-12 mph (Irish Wind Energy
Association 2016). This means it is important for wind turbines to be operating correctly during these
times of good wind conditions.
Electricity from these wind turbines is usually sold to the grid in order to make money from them.
While individual wind turbines do exist, it is much more common for wind turbines to be in a wind
farm for the use of the public.
Due to human usage, electricity has peak and off peak times. For example, between 5pm and 7pm in
the wintertime, electricity usage spikes by up to 800 megawatts (Sustainable Energy Authority of
Ireland 2016) . For wind farm operators to make a profit, they must ensure that the wind turbines are
producing as much electricity as possible at these times.
The efficiency of a wind turbine is dependent on a number of factors. These factors include its size,
blade length, number of blades (two, three or four), direction of the yaw, etc. In order for the towers
to operate as efficiently as possible, each of these aspects is considered in the design.
Most of these factors are considered at the design stage of the tower build. However, due to the
changing wind variations, the condition that has the largest effect on the wind turbine’s efficiency
after it has been built is the direction the tower is pointing into the wind. To be most efficient the
tower needs to be pointed into the direction the wind is blowing. Wind turbines are designed to do
this. Most modern wind turbines have built in wind vanes on the back of the nacelle that are used to
assess the direction that the wind is coming from. This information is used to point the tower into that
direction.
Wind direction may be strongest from a particular direction, but it changes over periods of time.
Variations in the wind direction cause the nacelle to yaw frequently.
If a wind turbine is not facing the direction the wind is coming from its efficiency goes down by the
(cos of the angle yawed.)^3, which with the average wind direction varying by up to +- 30 degrees
could lead to power output inefficiencies of 64% .
7
Currently a tool is used to monitor the condition of the composite wind blades while in operation. This
tool is attached to the base of the tower magnetically and is fitted with a camera that recorded and
monitors the condition of the composite wind blades. The need to monitor these blades is essential
to advancing the design of the blades in future and improving their overall efficiency.
The limiting factor to the current monitoring tool is that once it is attached to the wind turbine tower
it is fixed in position. The tool can record what is happening above it within the limit of the cameras
capability. However, it does not have the ability to track the nacelles movement and move along with
the tower as it yaws.
There are methods of inspecting and monitoring other areas of a wind turbine such as the blades or
nacelle. One such method is the Helical Robotics' HR-MP20 wind turbine-inspecting robot. Helical
Robotics. (2016) Like the current method used, it too attaches magnetically to the steel turbine tower.
It can, however, traverse the wind turbine tower both vertically and horizontally. It is the design of its
wheels that give it the ability move so freely around the tower. The complex magnet design allows
this movement.
The cost of the Helical Robotics' HR-MP20 wind turbine-inspecting robot is upwards of $18,000
The total invest cost of installing one wind turbine is up to € 1.1 million (Sustainable Energy Authority
of Ireland 2016).
A wind turbine tower is typically made of steel, and these towers range anywhere from 60-120m,
depending on the make and model (Irish Wind Energy Association 2016). The tower diameters vary
depending on the size and power output of the unit. The most common wind turbines in Ireland have
a tower is 50m high and a rotor diameter of 52m (Sustainable Energy Authority of Ireland 2016). Wind
turbines are simple structures. The generator sits on top of the tower encased in the nacelle with the
blades attaching to a central hub bolted to the nacelle. The nacelle is free to rotate a full 360 degrees
around the tower.
8
Design
Design Process
Initial Stages
A number of design ideas were developed through a series of brainstorming exercises and taking
inspiration from what is already available. The idea of using a magnetic wheel came from the existing
helical robotics robot and the unit that currently is used to survey wind turbine towers.
In order to fulfil the tasks laid out in the design specification a project plan was come up with. It set
out the tasks and deadline for the duration of the project. It is attached in Appendix A.
Design specification
Using the tools learned from Wallace and Clarkson (1999), the design specification was arrived at. The
specification is attached in Table 8 : Initial Design Specification in Appendix A.
This specification lists all of the aspects that the generated concepts need to stick to.
The areas specified were:
Geometry – the overall dimensions of the design
Kinematics – how the design moves on the tower
Attachment – how the design is attached to the tower
Forces – the forces the design is expected to handle
Energy – how the design is powered and how long it operates for
Materials – what the design is made from
Control – how the design is controlled
Safety – the maximum operating limits deemed safe
Assembly – how it is to be assembled
Transport – how the design is going to be transported
Timescale – the length of time for the design
Environment – the environment the design will have to operate in
The design specification, like the design process itself, was an iterative procedure. As the design
developed issues arose which influenced the design specification. The design was then changed
accordingly.
The final design specification shown in Table 2 lists the specifications of the Unit as it is built.
9
Table 2: Design Specification Final
D/W
W D
D D
D W
W W
W W
D D D W
D W W D
W
Wt
H H
H H
H H
H M
M M
H H M M
H M H M
M
Requirements
Geometry Shuttle overall dimensions: 300 x 300 x 150mm Rail Length 1500mm Kinematics Horizontal Movement along rail Autonomously controlled Overall weight 25kg Attachment Non-permanent – Attaches for 8hours Magnetically attached Forces Payload 10kg Unit 10kg Energy Power source – 1 Battery Pack - Lightweight Operate for 8 hours Materials Rail – Pipe able to hold 20kg Aluminium Chassis Non Corrosive Lifespan – 20 years Control Camera able to work up to 80 meters Program work without radio control Matlab: Simi link – video controlled analysis. Operating for length of battery life Safety Safe lifting limit 25kg – Maximum weight Max installation Height 1000mm
Keyword
Dimensions Angle
Manoeuvre Control
Attachment Attachment
Weight Weight
Battery Battery
Attachment Material
Corrosion Life
Camera Control
Program Battery
Lifting
10
Concept generation
Initial concepts were based loosely around what is currently available. The idea of adding a guide rail
became a central idea in the concept. Ideas were sketched and drawn. Different methods of keeping
the conditioning monitoring tool on the tower were come up with. These methods were sketched and
three sketches were chosen as concepts to be developed.
The idea was to come up with a chassis capable of holding a 10kg payload. With this in mind the
following concepts were developed.
Figure 4 shows the simple magnet wheel concept with a guide rail attached. The rig is supported fully
by the four magnetic wheels and the rail is just allowing it to travel horizontally. The payload is
mounted on top of this design. The rig attaches over the rail allowing it to travel along it as seen in
Figure 5.
W D
D D
D D
D D D
M M
M L
H H
M M M
Assembly Small parts Easily transported Transport Easily lifted. 25kg Maximum Fit into standard car boot 450 litres capacit Timescale 8 months design to construction Completed by 18/03/2015 Environment -40 degrees to 85 degrees c Strong winds 24m/s (55mph) Storm force 10 Protected from Moisture
Space Lifting
Weight Size
Project Plan Deadline
Temperature Wind
Height
11
Figure 4: Concept 1 – Plan View
Figure 6 shows the section concept. It is similar to the first, as it uses the magnetic rail design; however,
it has only two wheels. It uses two legs on either side to attach onto the guide rail that is positioned
underneath.
Figure 5: Concept 1 - End View
12
Concept 3 uses the rail to bear the load of the unit. It has one wheel which drives it along the rail it
hangs from. The rail is attached to the tower magnetically and is supported with support legs. It is
shown in Figure 7
Figure 6: Concept 2 - Plan and end views
Figure 7: Concept 3 - Front, End and Plan Views
13
Concept down selection
Using the methods suggested in “An Introduction to the Design Process” (Wallace & Clarkson, 1999)
the three main concepts were compared. The design specification was used to come up with a Concept
Selection Chart (Table 3). Concept 1 was chosen as a datum and all the other concepts were ranked
against it under the design wishes criteria from the design specification.
Table 3: Concept Down Selection
Criteria Weighting Concept 1 Concept 2 Concept 3
Value Wt Value Value Wt Value Value Wt Value
Dimensions 3 D
atum
1 3 1 3
Magnetically attached 2 -2 -4 -2 -4 Material Weight 2 1 2 1 2 Safety 2 -1 -2 -1 -2 Assembly - Small Parts 1 1 1 0 0 Assembly - replacement pieces 1 0 0 -2 -2 Transport 1 0 0 1 1
Total 0 Total 0 Total -2
While both concept 1 and concept 2 gained a 0 ranking it was decided to pursue concept 1 for this
design as it provided more stability for the unit. Furthermore, the four-wheel design would require
weaker and less expensive magnets than the two-wheel design.
SolidWorks Drawing
The majority of the design of the concept took place using SolidWorks drawing software. The software
allowed the concept to be brought from basic stages right through to the detailed design stage. The
software provided the platform to discover problems early on and the chance to change the drawings
and solve these problems.
14
Phase 1 – Magnetic Wheel Design
The concept selected involved using four magnetic wheels on a rig that could drive along the tower to
whatever position the nacelle yawed to. This concept relied on the magnetic wheel design.
The inspiration for the design came from the design used from the Helical Robotics' HR-MP20 wind
turbine-inspecting robot and the original unit that is used currently. The idea initially was to take a
standard plastic wheel and bore out holes to fit the magnets. This lead to a complete design of the
wheel allowing the specified magnets to attach it into it as shows in Figure 8: Magnetic Wheel
DesignFigure 8.
The magnets needed to be sufficiently strong enough for this design to work. A number of options
were considered before finally arriving on the S-30-10-N neodymium magnets sourced from
www.supermagnete.de . These magnets were specified as having a 20 kg Pull force however, as with
most magnets, no shear force limit was given.
Initially the wheel was sized with a 60mm radius. This measurement was based on the off-the -shelf
plastic wheels that the design originally planned for. The four wheels would sit on a shelf and a guide
rail would pass underneath them giving the rig direction along the tower.
In the end, the size of the wheel was driven by the distance that the rig was off of the rail on the
rollers. The wheel radius needed to be 60mm in order for the chassis of the rig to remain horizontal
so the payload could monitor the composite wind blades.
The wheel was drawn up at this size and it became apparent that there was not enough room for the
guide rail to pass beneath the chassis. This lead to an increase in the diameter of the wheel from 60mm
to 90mm.
Figure 8: Magnetic Wheel Design
15
This increase lead to an increase in the number of magnets needed for the part; the 60mm wheel
needed 9 magnets while the 90mm wheel needed 15.
After the initial design of this wheel, it was not immediately obvious how the magnets would be
secured to the wheel. This called for a revision of the design.
The magnets sourced were found to be available in a “pot magnet style” which includes a threaded
stem. These magnets were available in the same style and size as the initially specified magnets.
The wheel was drawn up as a solid cylindrical section but was revised and hollowed out to save costs.
The full drawing can be seen in Appendix C page C-1
Due to working with magnets, the material choice for the wheel was dictated by the need for it to not
be magnetic. After consulting with a technician, the choice was made to produce the wheels out of
Aluminium. This would provide a light, non-magnetic part, which is strong and resistant to the
elements.
A review of the Chassis design lead to the gap between the chassis and the rail greatly increasing by
moving the chassis to the opposite side of the bearing blocks. This gave much more room for the rail
and wheels to function, so the wheel was re-specified to 60mm radius. This size remained constant
throughout the rest of the design.
Experimentation was performed on the magnets originally specified. The S-30-10-N Neodymium
magnets were tested in shear to see if the 4 wheel set up would be possible with this magnet type.
The experiment procedure and results are shown in the experiments and testing section.
The results of this experiment proved that, while all 4 magnets could in facet support the rig and its
payload in shear, it could not do so if one or more of the magnets on the wheels was out of contact.
This, along with the general difficulty with working with strong magnets, led to a redesign of the entire
rig to make better use of the rail for weight distribution.
Due to this redesign, the need for strong magnets on the wheels was eliminated. However, there was
still a need for the wheels to grip the tower in some fashion. Using the wheel design that was already
drawn up, the magnets were re-specified to CS-S-27-04-N neodymium magnets which are
16
countersunk. This allowed for easy assembly by simply screwing in M4 screws fastening the magnets
into position.
The Material Data Sheets for both the S-30-10-N and the CS-S-27-04-N neodymium magnets are
available in Appendix B.
The final wheel design was manufactured in the prototype and only one wheel was used as per the
design progression. The assembled wheel is shown in Figure 9. This wheel design was used in the final
phase of the project as an option for the driven wheel for the unit itself.
The final wheel design drawing is attached in appendix C Page C-1.
Phase 2 – Chassis and bearing block Design
Chassis Design
The chassis design developed from a series of sketches that were come up with during the concept
generation phase. The chassis is the central part of the rig. While it is a simple part, it is required for
stability, for structure and for positioning all of the other parts along with the payload. The design of
the chassis encompassed all these aspects throughout.
Figure 9: Final Wheel Assembly
17
The first drawing of the chassis is shown in Figure 10.
Figure 10: Initial Chassis Design
This folded plate design took into consideration the space needed for a rail along with holes to allow
shafts for the wheels to pass through.
After a revision of this design, it was decided to simplify it substantially.
Revision 1 of the chassis design was a simple plate with 4 bearing blocks attached to the top of it
allowing the 4 wheels to attach to the chassis and the payload to sit in the centre of it. Figure 11 shows
the design. In order for the guide rail to pass beneath it, the wheel size was altered, as explained in
the previous section-this led to a larger distance from the tower to the payload.
18
This distance was deemed too large and the increased size of the wheel meant an increase in weight
of the unit. The design was again reconsidered and a solution was found.
Revision 2 was a simple but effective one. This revision moved the chassis to the opposite side of
the bearing blocks allowing the rail to pass freely between the 4 blocks.
Figure 11: Chassis Design Revision 1
Figure 12: Chassis Design Revision 2
19
This allowed a return to the initial wheel size and allowed the payload to be mounted closer to the
tower itself.
Figure 12 shows the sketch of this design. This design was considered the most promising until the
magnets were tested for the wheel design. The results of the testing and experimentation lead to
the need to refocus the design of the rig to supporting the weight of the rig from the rail itself.
From this perspective, it was important for the payload and all self-weight to be distributed into the
rail along with the magnetic wheel design.
Revision 3 inspected this method of carrying the weight and thus lead to a combination of wheels
and rollers.
Figure 13 is the resulting drawing. This included a newly designed roller at the top which would sit
onto the rail. Both the roller and the wheels were attached to shafts and bearings in bearing blocks.
Figure 13: Chassis Design Revision 3
20
This idea was thought through and a new rail design was come up with the accompany the roller.
However, the issue of stability and rotation became an issue. Due to only one roller being on it at the
top the motor driven wheels could rotate the rig when moving it.
The chassis was once again redesigned. This time the number of wheels was reduced to one and one
roller was added. It was reshaped into a more equilateral triangle also. This resolved the issue of the
rig rotating while moving.
Figure 14 and Figure 15 shows the finished cad drawing alongside the manufactured prototype. The
chassis is designed to house all the components needed for the full completion of the design
including Motor, Mini PC, Battery. These components are all shown below in Figure 16.
Figure 15: Prototype Design
Figure 14: Prototype
21
The chassis will then be covered by a casing both protecting the parts and allowing the payload to be
mounted.
The Final revision of the chassis design includes a thinner plate of aluminium, allowing it to be bent
slightly while in use. (Figure 17) To keep its shape, it is attached with a support bar, which gives the
unit its stiffness to compensate for the thinner plate. This curve design follows the final design of the
curved rail, which follows the curvature of the wind turbine tower itself.
Figure 16: Chassis Design Revision 5
Figure 17: Curved Chassis
22
Figure 18: Curved Rail + Chassis
Figure 19: Scale of rail on tower
23
Figure 20: Initial Bearing Block Design
Figure 21: Final Bearing Block Design
Figure 19 shows the overall size of the design situated on an actual size wind turbine tower. The
curvature of the rail is set to match the tower. Figure 18 shows a close up of the prototyped rig
assembly on this rail. It shows how even without a slight curve in the chassis it almost fits the rail.
A full working drawing of the final design for prototype is attached in Appendix C Page C-2 with all
dimensions and details needed for manufacture.
The chassis needs to be fitted with a cover once final control designs are completed. Once this is
fitted the payload can be attached and the rig can be operational.
Bearing Block Design
The purpose of the bearing block is to house the chosen bearing and to secure the bearing along with
the shaft and wheel or roller. It ensures the parts are secured rigidly and that it is mounted securely
to the chassis.
The bearing block was initially left out of the design as seen in Figure 10. This early design stage was
not detailed enough to identify the need for a bearing block.
With the redesign of the chassis the bearing bock was identified as a part that needed designing as
seen in Figure 11. It was not until the late stages of the chassis design that it was properly considered.
24
Figure 20 shows the initial design of the bearing block with space shown for the bearing. The outside
diameter was driven by the size specified for the bearing.
After finally specifying the bearing as a SKF 6203 ball bearings, the bearing block was altered again.
These alterations included an internal Lip to support the back of the bearing along with a grove cut
out to allow for the placement of circlips. The design was drawn up so that the bearing block would
be a common size for both the wheel and the roller shafts. The only difference between the two was
the placement of the tapped holes, which allowed them to attach to the chassis in the correct
orientation for use.
Complete drawings for the bearing blocks are attached in Appendix B
Material Selection
The material selection for the majority of the design was based upon using magnets as the primary
method for holding the rig to the tower and the need to cut down on weight for the entire design.
The method used for specifying the material type is outlined in chapter 4 of Materials Selection in
Mechanical Design (Ashby, 2011).
A Design requirement chart is drawn up for the chassis to decide on the constraints, objectives and
free variables of the design.
Table 4: Chassis Design Requirements
Design Requirements for Chassis
Function plate
Constraints Must not Yield Must not fracture if struck Small thickness
Objectives Minimize mass, m Maximize Strength Maximize Stiffness
Free Variables Choice of Material Dimensions
25
Using Table 4 a materials property chart is selected to select the possible materials.
Figure 22 is the material property chart chosen. All of the materials above the red line represent
possible material choices. The red line is decided upon based upon the guidelines for minimum mass
design shown in the chart. (E^1/3)/ ρ was chosen as it represents the design requirements for a flat
plate like the chassis in this situation.
The materials chosen from this graph were stainless steel, aluminium, carbon fibre reinforced plastic
(CFRP) and titanium. Some materials were excluded immediately like natural materials and foams as
although their density is good, they lack the strength needed for this design.
The materials were put into a material ranking table (Table 5) and ranked against each other based on
their performance to the set out selection criteria M.
Figure 22: Material Property Chart (Ashby 2011)
26
Table 5: Material Ranking Table
Material M = (E^1/3)/ρ Comment
Stainless Steel 8.70 Cost effective, Magnetic
Aluminium 8.52 Relatively in-expensive, Lightweight compared to steel
CFRP 37.71 Lightweight, More expensive than Aluminium
Titanium 8.73 Expensive, Good properties
CFRP ranks highest in the ranking table. It is eliminated from the design choices as it is expensive and
not as straight forward to work with as the other materials.
Titanium, and stainless steel both rank favourably with aluminium following closely behind. However
due to the cost of titanium it was eliminated also.
Stainless steel while ranking higher than aluminium can be magnetic. Due to the design functioning
around the use of magnets it was decided to eliminate this material and go with aluminium.
When bringing the design to the manufacturer the material choice was discussed. The manufacturer
agreed with the choice of aluminium for the chassis and suggested using it for all of the parts that
needed to be manufactured due to its softness and availability. Aluminium was then specified for all
parts in the assembly and used for the manufacture of the prototype.
The aluminium used in the prototype manufacture was anodised to prevent corrosion.
27
Phase 3 – Rail and Roller Design
The rail was included initially as a method for keeping the rig traversing along the tower horizontally.
It was to be attached to the tower magnetically but to support no real load.
The first drawing of the rail consisted of a hollow tubular section set underneath the chassis. This
design is shown in Figure 23
Figure 23: Initial Rail Design
This design was used throughout most of the iterations of the chassis and wheel designs. The rail is
tapped to allow the CSF-48 pot magnets to be screwed into them.
The material data sheet for the CSF-48 magnets is available in Appendix B.
As the chassis design changed, a shelf-like rail design was briefly considered. This design would have
a wheel rolling along the flat section with the chassis hanging below it. Error! Reference source not f
Figure 24: Shelf Rail Design
28
ound. shows this design in basic stage. While this is an area that was considered it was decided to
return to the tubular section and instead design a roller to roll along the tube section.
The roller was designed to be simply manufactured and easy to assemble. The initial sketches were
drawn up and assembled in SolidWorks. To prevent the roller from slipping a ridge was attached to
the top of the rail to allow the side of the roller to lay against it if it were to be pulled. This prevented
the rig from falling off the rail. Figure 25 is an illustration of this design.
Full roller drawings are attached in the Appendix C Page C-4
Figure 25: Rail and Roller Design
Figure 25 also shows the leg attachments on either side of the rail. Following the testing of the
magnets being used for the wheel design the strength of the magnets was found not to be sufficient
to support the rig and its payload. The rail was then designed for taking the load of the rig. To transfer
this load to the ground adjustable legs were added to each side of the rail giving it support.
29
Figure 26: Rail Support Leg Design
Figure 26 shows the manufactured adjustable support legs for the rail. They include tightening screws
on the leg, to allow the height to be changed, and on the rail loop, to allow the angle of the leg to be
changed. These screws also act to keep the legs in place on the rail.
The rail drawings were sent to the manufacturer to be made for the prototype. A different rail was
decided upon following discussions with the manufacturer. In Figure 27 the square box section is
shown with grooves added to take the roller. Like the original design, the rail is tapped along its length
and magnets are attached. These CSF-48 magnets prevent the rail from pulling free from the tower
under normal operating conditions. The have a pull strength of 23kg’s.
Figure 27: Prototype Rail Design
30
The final iteration to the design of the rail was to curve the length of the rail to match the curvature
of the wind turbine tower. (Figure 28) This allows the rig to move freely around the tower. The length
of the rail is specified as 2000mm. This takes into consideration the average yawing of a wind turbine
during an 8-hour period.
Final rail and rail support drawings for the prototype are attached in Appendix C Pages C-5 and C-6
With the addition of the stepper motor in the control design, the rail will be fitted with proximity
sensors at each end of the rail.
Shaft Design
There were two different types of shafts designed and three shafts in total. The diameters were
specified as the same for both, however, the distance from the bearing was different. This was to
ensure that the distance from the tower face to the roller and its shaft matched up with the distance
of the wheel to its shaft. It also allowed the wheel to protrude over the edge of the chassis so it could
move freely.
The shaft also included a groove and a butt for the bearing so it could be securely held and kept in
place by circlips. This feature was common with both designs.
Figure 29 shows the shaft with the bearing attached with the circlip while Figure 30 below shows the
completed part with the roller attached.
Figure 28: Curved Rail Design
31
Phase 4 - Prototype
After working through all the revisions a final set of working drawings was created. These drawings
were then taken to a workshop to be manufactured. Upon meeting with the manufacturer, the design
was talked through and a number of changes were made to the prototype.
The rail was also given a redesign. It moved away from being a cylindrical length of pipe with a ridge
on top to a rail that the rail bearing could easily track on to. This simplified the connection between
the rail and the unit. It also provided more stability.
The materials that were specified for parts of the prototype were also discussed with the
manufacturer. It was suggested to use aluminium for the bearing blocks as it cuts down on weight and
is cheaper and easier to use. This, along with some other small changes, were added to the design in
order to produce a successful working prototype.
The prototype was loaded to its design load of 10kg. The prototype functioned at this weight and this
justified the design.
Figure 30: Roller and Shaft Design
Figure 29: Shaft with Bearing attached
32
Phase 5 – Control system design
The control system for this design is an area that is not fully developed. The rig was mechanically
designed and a stepper motor was specified to drive it along the rail. With the use of image tracking
software, it will track the yawing of the nacelle as the wind turbine is in regular use.
The stepper motor layout is shown in Figure 16. The motor and the shafts will be fitted with toothed
gears pictured in
The belt pictured (Figure 32) in will be attached and the two outside pulleys will provide tension for
the belt.
Figure 31: Control Gear
Figure 32: Belt for motor
33
The Stepper motor make and model is shown in Figure 33.
This motor will work quite slowly however the movement of the wind turbine nacelle also happens
relatively slowly so this will not be an issue.
The full material data sheet for the RS 440-422 stepper motor is attached in Appendix B.
Two stepper motor proximity sensors will be mounted at either end of the rail. This will inform the
motor when to stop.
The motor will revive its information from the inbuilt computer system mounted on the rig. The
Raspberry Pi or similar unit could complete this task.
Raspberry Pi has the ability to run Mat Lab successfully on it. Attaching a simple web camera to this
allows the image acquisition tool boxes to be run through Simulink. The programmes could be
programmed to follow the simple logic showed in Figure 34.
Figure 33: Stepper Motor
34
Figure 34: Control Logic
A battery pack providing 8-hour life has been specified for the design.
Place rig on centre of rail below the tower
and turn on
rig runs to the left until it reaches the proximity sensor
the rig returns to the centre and locks on to
the nacelle
the rig tracks the yawing and moves
with it
if it reaches the end of the rail it stops
When the nacelle returns it begins
tracking agian
Continues tracking the nacelle until the
designed 8 hour run
Returns to centre and powers down
35
Phase 6 – Final Drawings
A set of final drawings was drawn up to include all aspects of the final design. These drawings are a
combination of the original drawings sent to the manufacturer for the prototype build, the changes
made at the manufacturing stage and the alterations decided upon after testing the prototype.
The main changes from the prototype have to do with the design in actual use on a wind turbine
tower. The tower itself is not a flat plate as shown in the prototype. Its curvature is reflected in the
design of some of the parts such as the rail and chassis. Other parts, such as the shafts, roller and
wheel, were unaffected by this change. A drawing of a full assembly of the rig is shown in Appendix
C Page C-10
This drawing shows the rig in position on the tower. This drawing also shows the position of all the
additional control equipment and motors.
The drawings attached in Appendix C are a full set of construction drawings and can be used to
produce this condition monitoring tool as per this design.
Assembly
The assembly of the full prototype rig was relatively straightforward once all the parts were
manufactured. Ten M8 bolts for the chassis and nine screws for the wheel were all the extras that
were needed.
The M7 bolts used to attach the bearing blocks onto the chassis. The bearing blocks were pre- tapped
and no issues arose. The magnets were then individually screwed into the wheel using countersunk
M4 bolts.
The issues that arose during assembly were a result of machining. Various edges of the aluminium had
to be sanded down and greased up to allow the shaft to fit into the bearings and the bearings fit into
the bearing blocks. However, the result provided each part of the design with a secure assembly that
will not fail.
The prototype was assembled easily and quickly as per design. The assembly details are shown in the
assembly drawings section in Appendix C Page C-9
All that was needed was M8 and M4 bolts and it all attached together straightforwardly. Once
assembled, the prototype was then sent to the lab for testing.
36
Experimenting and Testing
Magnets
Procedure:
The S-30-10-N neodymium were tested using the apparatus shown below in Figure 35. The 20mm
thick steel plate was mounted on a vice holding it in place. The magnet was then placed centrally and
a weight hanger was hung from it by cable ties. The weight was added incrementally. Four magnets
were tested to ensure that all magnets reacted the same. Magnet A was tested a number of time until
it slipped. It was then repositioned and reloaded to this weight, adding more weights when possible.
Magnets B, C, and D were then loaded with this initial weight and tested until slip.
Figure 35: S-30-10 Disk Magnet Test Apparatus
Weights
Magnet
Vice
Weights Hanger
HangerSteel Plate
Steel Plate
37
Results
The results of the test are shown in Table 6
Table 6: Results of S-30-10 Disk Magnet tested
The lowest weight for slip is 3.9kg’s
Conclusions
Using the results from the test, it could be possible for the four-wheel setup to carry the weight of the
rig. The combined capacity of four wheels would be 15.6kg. However, a number of issues with the
design arose from the testing. The placement of the magnets is critical. If the magnets are in-between,
wheel turns and not all four magnets are in contact, then the design may fail under the weight of the
payload.
Another issue encountered was the difficulty in working with magnets this strength. The S-30-10 Disk
Neodymium magnets tested were very strong. Once they stuck to the surface of the metal they
needed a strong force to remove them. This will become an issue for the motor that has to turn them,
Test 1
Test 2
Test 3
Test 4
Test 5
Test 6
Test 7
Test 8
Test 9
Test 10
Magnet A A A A A A A B C D
We
igh
ts A
dd
ed
200 200 200 200 200 200 200 200 200 200
250 1000 2000 2000 2000 5000 2000 2000 2000 2000
250 500 1000 1000 1000 1000 1000 1000 1000
250 250 250 250 500 1000 250 500 500
250 250 250 250 500 500 200 200 200 Legend
250 250 250 250 250 100 No Slip occurred
250 250 250 250 Slip occurred
250 250 250
250 250 250
250
250
200
Total (Grams) 1700 3200 3950 4700 5900 5200 4700 3750 3900 3900
38
as it will require a strong motor in order to provide enough force to lift them. This will lead to an
increase in the size of the motor and more importantly an increase in the weight of the motor.
This was a deciding factor in the redesign of the device.
The material data sheets for each of the three magnets tested can be found in (appendix B)
Prototype
The Prototype was mounted with a 10kg weight in order to simulate the payload. The design was able
to hold this weight and move along the rail with ease. In order to find out the power required to move
the loaded unit it needed to be tested with the simulated payload in place.
The prototype was set up against a steel plate simulating the tower. The test rig is shown in Figure 36
Figure 36: Prototype Test set up
Strap
Tightening Screw
Steel Plate
Weight Hanger
39
Procedure
The rig was mounted on the rail at the centre point and a strap was attached to the bearing block. The
other end of the strap was looped around the tightening screw on one of the supporting legs and tied
off- a weights hanger was hung from this. Weights were then hung from the hanger incrementally
until the rig moved. This test was repeated a number of times to give a more accurate result.
Results
Table 7 shows the weights added for each test and when slip occurred.
Table 7: Prototype Test
Test 1 Test 2 Test 3 Test 4 Test 5 Test 6
Magnet A A A A A A
We
igh
ts A
dd
ed (
g)
200 200 200 200 200 200
500 500 500 500 500 500
500 500 500 500 500 500
250 250 250 250 250 250
250 250 250 250 250 250 Legend
250 250 250 250 250 250 No Slip occurred
250 250 250 250 250 250 Slip occurred
250 250 250 250 200 250
250 200 250 200 250
100 100 100 100
100 100 100 100
Total (Grams) 2450 2700 2850 2900 2800 2900
The Maximum amount it took to get slip to occur was 2.9 kg.
40
Conclusion
The weights added incrementally gave mixed results. The value needed to be taken from this test is
the maximum weight needed to move the rig This is the value that will drive the motor specification.
The test revealed, however, that the weights were gaining most resistance from the pull of the
magnet. When attached mid turn it moved a lot freer. The 2.9kg force applied was the force needed
to cause slip in the magnet allowing the wheel to turn.
Nacelle Tracking
A simple test for the tracking of the nacelle was designed.
A webcam was attached to the prototype is set in the centre of the rail directly below the tower
simulator.
Procedure
The web cam is positioned in the centre of the rig as it would be on the finished design. The tennis ball
represents the nacelle.
The tennis ball is rotated around the test tower.
The outputs suggested by Simulink are monitored.
The tennis ball is rotated the opposite direction. The output is monitored again.
Conclusions
This Test could effectively test the capability of the software developed on a small scale in laboratory
conditions. It would be a good starting point to develop the software for potential real world use.
41
Results
The final set of production drawings are attached in Appendix C along with the full set of drawing files
in SolidWorks. These drawings are the end result of the design process that was followed.
Along with these drawings a series of experiments were carried out to verify that the design
specification was achieved.
To provide proof of concept a prototype was manufactured. This prototype was then tested as well.
All further details not included in the prototype are included in the final design specification.
The overall cost of Manufacture and Materials was €700.00.
All copies of drawings and iterations of drawings are attached in the attached CD.
42
Conclusions
The initial design objectives are fulfilled to a certain extent. The rig that was designed and
manufactured as a prototype proved the mechanical design concept.
While working with this prototype a number of issues arose. These issues are addressed in the main
body and the changes are reflected in the final drawings that are issued in appendix C
The motor set up for would need additions added to the rail in order for it to function as a stepper
motor. The program would need to be launched so that the rig could move to a predefined sensor and
then gain its position on the rail under the nacelle. This program would also prevent the rig from falling
off of the rail by moving too far. If the nacelle yawed too far out of the range of the rail, then it would
simply stay at the end of the rail until it returned in a given period of time.
The curvature of the rail to match the tower only requires a very slight curve along the chassis. This
could be achieved relatively easily without altering any of the existing parts.
The cost comparison to the available robotic condition monitoring tool and the design developed
alone justifies the concept. The Helical robotics model costs €18000.00 while the cost to date of the
design developed was €700.00. This simple design fulfils the design requirements and solves the
problem.
The objective to develop a tool capable of monitoring the composite blades of a wind turbine is
partially complete. It did meet the requirements to be portable and lightweight and also to move along
the tower horizontally.
It did not complete the software design however the basic layout is designed for.
In conclusion this design meets the criteria and with further work will accomplish the objectives it was
designed for.
43
Recommendations / Future work
While mechanically the prototype proved the concept, the following items are recommended to be
followed up on to finish this project.
Redesign of the motor mechanism should be done. A more efficient method of running the
rig can be found.
A more detailed rail and chassis design is needed to follow the curvature of the Tower.
A detailed design of the nacelle tracking software would provide much better results than the
current set up.
The use of slightly stronger magnets to hold the rail may eliminate the need for the legs in the
set up.
Further research into motors is needed.
Further research into batteries, mini computers and fine tuning of the tracking software.
The Payload needs to be designed with a mount, this can only occur after the cover is fitted
over the internal working parts.
44
References
Anon., 2016. Helical Robotics. [Online]
Available at: http://www.helicalrobotics.com/
[Accessed 17 March 2016].
Anon., 2016. Sustainable Energy Authority of Ireland. [Online]
Available at: http://www.seai.ie/
[Accessed 17 March 2016].
Ashby, M. F., 2011. MAterials Selection in Mechanical Design. Fourth Edition ed. Burlington, MA:
Butterworth-Heinemann.
Association, I. W. E., 2016. Irish Wind Energy Association. [Online]
Available at: http://www.iwea.com/
[Accessed 17 March 2016].
Budynas, R. G. & Nisbett, J. K., 2015. Shigley's Mechanical Design. 10th ed. New York: McGraw-Hill
Education.
Wallace, K. & Clarkson, J., 1999. An Intorduction to the design Process. Cambridge: University of
Cambridge, Department of Engineering.
a
Appendix A Table 8 : Initial Design Specification
D/W
W D
D D
D W
W W
W W
D D D W
D W W D
W
Wt
H H
H H
H H
H M
M M
H H M M
H M H M
M
Requirements
Geometry Shuttle overall dimensions: 300 x 300 x 150mm Rail Length 1500mm Kinematics Horizontal Movement along rail Autonomously controlled Overall weight 25kg Attachment Non-permanent – Attaches for 8hours Magnetically attached Forces Payload 10kg Unit 10kg Energy Power source – 1 Battery Pack - Lightweight Operate for 8 hours Materials Rail – Pipe able to hold 20kg Aluminium Chassis Non Corrosive Lifespan – 20 years Control Camera able to work up to 80 meters Program work without radio control Matlab: Simi link – video controlled analysis. Operating for length of battery life Safety Safe lifting limit 25kg – Maximum weight Max installation Height 1000mm Assembly
Keyword
Dimensions Angle
Manoeuvre Control
Attachment Attachment
Weight Weight
Battery Battery
Attachment Material
Corrosion Life
Camera Control
Program Battery
Lifting
b
W D
D D
W W
D D
D D D
M M
M L L M
H H
M M M
Small parts Easily transported Transport Easily lifted. 25kg Maximum Fit into standard car boot 450 litres capacity Assembly Easily manufactured parts Standard replacement pieces Timescale 8 months design to construction Completed by 18/03/2015 Environment -40 degrees to 85 degrees c Strong winds 24m/s (55mph) Storm force 10 Protected from Moisture
Space Lifting
Weight Size
Replacement Standard Parts
Project Plan Deadline
Temperature Wind
Height
a
Appendix B
a
Appendix C