DRIVING MODULE
Marcus Abrahamsson
Xavier Evrat
Christian Magnusson
Henrik Svensson
Institutionen för maskinteknik Blekinge Tekniska HögskolaKarlskrona 2002
Följande arbete är utfört som en obligatorisk del av utbildningen på programmet Utvecklingsteknik vid Institutionen för Maskinteknik på Blekinge Tekniska Högskola.
Following project is done as an obligatory part of the education on the program Developing technology. “Utvecklingsteknik” at the institution for mechanical engineering at the Blekinge Tekniska Högskola.
1 Preface
This project is an examination these for pass the Bachelor of Science in Mechanical Engineering with Emphasis on Product Development at the BLEKINGE INSTITUTE OF TECHNOLOGY. This work was carried out under the supervision of Dr. Mats Walter and Dr. Morgan Klang.
This research project was performed in co-operation between the University and “Elautomation Syd AB” the society which needed to manufacture for SAS a driving module for their Cart.
The project group consists of three students from the BLEKINGE INSTITUTE OF TECHNOLOGY and one from an Engineering school “EIGSI La Rochelle” from France. He was involved in this project as an exchange student for two months and a half until the middle of April.
We wish to express our sincere appreciation to Christer Georgsson, the inventor, Knut Blom and Jonas Persson from “Elautomation Syd AB” and Peter Melander from SAS for their help and engagement throughout the work. Finally we want to thank Dr. Mats Walter and Dr. Morgan Klang for their valuable support and advice.
Karlskrona the 5th of May 2002
Marcus Abrahamsson Christian Magnusson Henrik Svensson
Xavier Evrat (Exchange student)
2 Summary
This project has been made in co-operation with “Elautomation Syd AB” located in Svängsta. This study is partly based on a report from Högskolan I LULEÅ University written by Jörgen Winkel, Berit Ekblom and Bengt Tillberg called “Fysiska Belastningar på Kabinpersonal vid trafikflygning”. We needed to design an electric-driven module to place underneath a serving-cart, to facilitate the work made by the cabin personal and thereby prevent work injuries. This degree project is divided in three parts: ”Principkonstruktion”, ”Primärkonstruktion” and “prototype manufacturing”, according to the Fredy Olsson method.
In the first part of the project Principkonstruktion” we analysed the criterions and the wishes from our customer in order to determine the principals. We also investigated the standardization rules use in the airplane construction. After combining the proposals we checked the fulfilling of this criterions.
Secondly on the ”Primärkonstruktion” phase, few test were performed on this proposals in order to define which one we considered the best. According to this result we decided to focus on one proposal and we began to create the product drawing. Afterwards we made some more accurate drawings to define the product according to the FEM results. Finally we did a model over how the module will be designed.
Table of contents 1 Preface 2 2 Summary 3 3 Notations 10 4 Introduction 11 4.1 The project 11
4.2 Presentations of the group members 11
4.3 Presentation of the Universities 12
4.3.1 The Blekinge Institute of Technology 12
4.3.2 EIGSI an engineering school in France 15
4.4 Fredy Olsson’s Integrated Product Development 18
4.4.1 The process of IPD 18
5 PPSHE 19 5.1 Product (P) 20 5.2 Process (P) 20 5.3 Surroundings (S) 21 5.4 Human (H) 21 5.5 Economy (E) 22
6 Product survey and criterion disposition 22
6.1 Product survey 22
6.1.1 SAS 22
6.1.2 Wexiödisk AB 23
6.1.3 Iacobucci 24
6.2 Criterion and wishes disposition 24
6.2.1 Functions or performance criterions 24
6.2.2 Operation criterions 25
6.2.3 Personal safety criterions 25
6.2.4 Ergonomic criterions 25
6.2.5 Esthetical criterions 25
6.2.6 General design/production criterions 26
6.2.7 Manufacturing criterions 26
6.2.9 Elimination criterions 26
6.2.10 Production economical criterions 27
6.2.11 Users economical criterions 27
6.3 Additional comments 27
7 Compilation of product proposals for module 28
7.1 Manner of operation 28
7.1.1 Electric motor 28
7.1.2 Compressed air 28
7.2 Design of the product 28
7.3 The products way of construction & primary proposals 29 8 Evaluation of the product proposals of module 34
8.1 Advantages and disadvantages of the proposals 34
8.2 Evaluation 38
8.2.1 Primary evaluation 38
8.2.2 Intermediate evaluation 41
8.2.3 Final evaluation 41
8.3 Evaluation through tests/experiments 44
8.4 Second test 45
8.4.1 Evaluation through calculations 46
8.4.2Energy needed for the serving cycle 50
9 Lift development 52
9.1 Function of the lift 52
9.2 Criterion disposition for lift 53
9.3 Lift proposals 53
9.4 Evaluation of lift proposal 56
10 Steering device development 58
10.1 Function of steering device 58
10.2 Criterions for steering device 58
10.3 Steering device proposals 59
10.3.1 Manner of operation 59
6.2.2 Proposals 59
10.5 Conclusion 63
11 Presentation of final proposal 64
11.1 Module proposals 64
11.2 Lifting device proposals 65
11.3 Steering device proposals 66
11.4 Conclusion 68
12 Product Concept 69
12.1 Specification of the parts 70
13 Choosing components 70
13.1 Criterions on module 70
13.2 Searching for components 72
13.3 Electric motor 72
13.3.1 Evaluation of motor proposals 73
13.4 Transmission 75
13.5 Driving wheel 76
13.7 Electric control device 76
13.8 Battery 77
14 First prototype design 79
15 Detail design 80
15.1 Criterions of the detail (-s) 80
15.2 Detail proposals 80
15.2.1 Detail proposal no. 1: “Triangular” 81
15.2.2 Detail proposal no. 2: “Spring” 82
15.3 Locking device solution 83
15.4 Test to determine the needed down force 83
15.5 Evaluation and choice of the proposals 84
15.6 Components of the lift 85
15.6.1 The springs 86
15.6.2 Ball bearings 86
15.7 The results and choice of lift components 86
15.7.2 The ball bearings 87
15.8 Material choice 88
15.8.1 Conclusion & choice 89
15.9 Technical design 89
15.9.1 Usage 90
15.9.2 Bending of lift parts 90
15.9.3 Bending of locking device parts 93
15.9.4 Pressure 97
15.9.5 FEM calculations 98
16 Project management 100
16.1 Evolution of the project phase 1 and 2 100
16.2 Risks 100 16.3 Gantt schedule 101 16.4 Meetings 101 17 References 103 Appendix 105 Appendix 1: Questionnaire 106 Appendix 2: Frågeformulär 107
Appendix 3: Trolley Washer WD-18CW 108
Appendix 4: Technical data 109
Appendix 5: Functional description 110
Appendix 6: Dimensional Drawing 111
Appendix 7: Cabin Configuration 112
Appendix 8: Parameter calculation Small Cart 113 Appendix 9: Parameter calculation Big cart 114
Appendix 10: Module Evaluation 115
Appendix 11: Lift Evaluation 116
Appendix 12: Handle Evaluation 117
Appendix 14: First Prototype: 119
1. Side View 119
2. Friction Tests: 119
Appendix 15: Driving Prototype 120
1. Bottom View: 120
2. Right view: 120
Appendix 16: FEM calculation pressure 121
Appendix 17: FEM calculation locking device I 122 Appendix 18: FEM calculation locking device II 123
Appendix 19: FEM calculation pedal 124
Appendix 20: Battery Construction 125
Appendix 20: Principal Gantt schedule 126
Appendix 21: Primary Gantt schedule 127
Appendix 22: DC Motor, Rockwell Automation 128
Appendix 23: Faulhaber 130
Appendix 24: Maxon Motor 140
Appendix 25: Premotec Transmission 142
Appendix 26: Stohne elteknik motor 143
Appendix 27: Stohne elteknik gear 144
Appendix 28: Drawing “lift support 1” 145
Appendix 29: Drawing “lift support 2” 146
Appendix 30: Drawing “slide” 147
Appendix 31: Drawing “locking device” 148
Appendix 32: Drawing “fixation link” 149
Appendix 33: Drawing “guidance 1” 150
Appendix 34: Drawing “guidance 2” 151
Appendix 36: Drawing “link” 153
3 Notations
Mv is the twisting torque [Nm]
M is the bending torque [Nm]
F is the applied force/load [N]
x is the deflection of the spring [m] k is the stiffness of the spring [N/m] d is the diameter of the wire used to make the spring [m] G is the shear modulus of the material (usually steel) [N/mm2]
Dy is the diameter of the spring itself [m]
N is the number of coils in the spring.
L0 is unloaded length of the spring [m] τmax is the maximum stress in the material due to the load [N/mm2]
m is the mass [kg]
δ is the acceleration [m/s2]
P is the electric or mechanic power [J/s]
v is the linear speed [m/s]
ω is the radial speed [rad/s]
µ is the friction coefficient (dimensionless).
η is the efficiency [%]
r is the radius [m]
f is the frequency [Hz]
Rp is the yield strength [N/mm2]
σ is the stress [N/mm2]
Shortenings
FEM Finita Element Methode
No. Number
4 Introduction
4.1 The project
This is the final report of our five-month degree project at BTH (Sweden), department of Mechanical Engineering.
The degree project is performed in co-operation with the inventor, Christer Georgsson, “Joje” from Saxemara and the company “Elautomation Syd AB”, located in Svängsta. The company needed help to construct an electric-driven module to place underneath a serving-cart, the main idea is to facilitate the work made by the airhostesses and thereby prevent industrial injuries and decrease the number of workers on the sick list.
The inventor has one solution of the problem and a patent for a module. But our task was, starting from scratch, to construct a working module considering the main demands and wishes received from Christer Georgsson and other criterions found after contact with SAS.
4.2 Presentations of the group members
The group consists of 4 students, 3 from Sweden and one from France. Marcus Abrahamsson, Christian Magnusson and Henrik Svensson are 3 students who study in the Blekinge Institute of Technology. This project is the end of their education to pass the Bachelor of Science. Xavier Evrat comes from France and he studies in one engineer school in La Rochelle. He is involved in this project thanks to European program Socrates as a 3 months training period.
4.3 Presentation of the Universities
4.3.1 The Blekinge Institute of Technology
The BTH is a Young University located in the southern part of Sweden, along the east coast. This province of the country is named Blekinge, and it’s known as “the Garden of Sweden”. Established in 1989 it has accepted it’s first students in the 1989/1990 Academic years.
Nowadays approximately 5500 individual students (converted to full-time students; 3100) occupy the 3 different sites of Karlskrona, Ronneby and Karlshamn. The Blekinge Institute of Technology has 35 programmes, 9 Master’s and approximately 150 separate courses. The aim of the University is to focus on the Information Communication Technology and Social and Commercial development.
General Information:
• 1989, the Institute was founded
• 1999, the Institute gained the right to run Ph.D. programmes in technology
• 1999, the Institute merged with The Baltic International School of Public Health
• 2000, the Institute opens a new campus in Karlshamn • 2000, the Institute was re-named Blekinge Institute of
Technology
• 5500 individual students (converted to full-time; 3100), 47% women
• 425 employees
Figure 4.1. In this figure you can see where in Sweden Karlskrona is located.
Departments represented in 3 different sites:
1. Department of human Work Science and Media Technology 2. Department of Business and Management
3. Department of Spatial Planning 4. Department of Humanities
5. Department of Science and Health 6. Department of Mechanical Engineering
7. Department of Software Engineering and Computer Science 8. Department of Telecommunication and Signal Processing
The Department of Mechanical Engineering:
Our Department is the Mechanical Engineering and it is located at Campus Gräsvik in Karlskrona. It carries out education and research in the area of mechanical engineering. It offers a Bachelor programme with emphasis on “Virtual Product Development and Design” and a Master programme on “Structural Mechanics”. We have access to one CAD/CAM software called I-DEAS® primarily used in the industry. When talking about designing a structure, calculating a frame, viewing a complex system. This software has a large number of available possibilities: designing, drafting, simulating, testing, manufacturing. The contact between tutors and students are informal in order to create a good work atmosphere. Thus permit the development of a close co-operation with industry and regional organisations during the final projects.
Blekinge Institute of Technology SE-371 79 Karlskrona, Sweden
www.bth.se
4.3.2 EIGSI an engineering school in France
The school
The French engineering school is called EIGSI. It was founded in 1990 in LA ROCHELLE. EIGSI means in French Ecole d’Ingénieur en Génie des Systèmes Industriels, in English: Industrial Systems Engineering School.
Nowadays, there are about 500 students in the school.
Figure 4.3. This figure
shows where in France La Rochelle is located.
The History
It was called EEMI-Violet (Electrical and Industrial Mechanic Engineering school) at beginning of the century according to the street name where it was located in Paris. Founded in 1990 in La Rochelle thanks to the wish of old students from EEMI-VIOLET desired to create a new school, which inherits, of the tradition and more adapted to the new industry needs. EIGSI received its first students in 1990, the Industrial Systems General Engineering diploma is approved since 1991 by French Educational ministry of Higher Education. The first engineer was graduated in 1993 and since then, EIGSI awarding more than 100 diplomas each year
The environment
The School is located in La Rochelle on the Atlantic coast, about 500km from Paris. It takes place in the university campus in “Les Minimes” the largest harbour in Europe. Nowadays, the university campus counts 8000 students and EGSI about 500.
The education
It is a five years multidisciplinary school; the students integrate the courses just after Baccalaureate (equivalency of the A level) and having no preliminary preparatory cycle integrated into the curriculum. Some students who have had a special course can integrate the school in third years. The courses connect the various traditional scientific fields and ensure a global solution with talking into account all the technical, economic and human components. It constitutes a new approach to circumvent the industrial development.
During the five years, the students will be following some lectures, tutorials, practices, and works assignments in this the several fields:
• Mathematics • Computer science • Mechanics and Energy
• Mechanical Engineering and material • Electricity
• Automation • Communication • Management
In order to connects their scientific knowledge to the industrials world, the students have to do some training periods:
• In the second or third year: as a technician to discover the industrial world and the worker's conditions.
• During the fourth year: In small groups on industrial study for six weeks, which students carry out in a company within the framework of an industrial project.
• In the fifth year: Engineering training: five months training internship to get graduated.
There are some other opportunities to do these training periods abroad, thanks to European programs such as Socrates (fourth year students) and Leonardo (fifth year students).
Figure 4.4. Photograph taken outside Eigsi.
Ecole d’Ingénieurs en Génie des Systèmes Industriels
26 rue Vaux de Foletier – 17041 La Rochelle CEDEX 1 France
4.4 Fredy Olsson’s Integrated Product
Development
In this project we will use a method of integrated product development. Fredy Olsson [1] is the author of this method.
4.4.1 The process of IPD
The general description of this process:
1. Define the need on the market. Our superiors in our project had already defined this.
2. Define the type of the product.
3. The principal construction phase, the first step in this report. 4. The primary construction phase, the second step in this report. 5. Manufacturing design.
6. Final design.
7. Prototype and testing.
The principal construction phase This part of the process contains:
• Product definition. The product’s containing parts, its tasks, its working surroundings and who are getting in contact with the product.
• Product survey and criterion disposition. We do a background check, are there any existing solutions on the same product and we define all the criterions for the product.
• Compilation of product proposals. We show different solutions which can fulfil our criterions.
• Evaluation of the product proposals. We evaluate the proposals we have and see if they fulfil our criterions.
• Presentation of the final, chosen proposal. The best proposal will be chosed so we can start work with the next step, the primary construction phase.
The primary construction phase This part of the process contains:
• Product Concept. Here we show the parts which are included in the product, how they are arranged and some approximately dimensions.
• Component choice. Here all the parts which can be bought are shown. To buy standard components saves time and money. • Detail construction. Here we design parts which can’t be
bought. These parts are special and rare so we need to make them ourselves.
• Manufacturing and testing. We manufacture a final prototype and make some tests to make sure it fulfil our demands. If it doesn’t it will be expensive to make changes this late.
5 PPSHE
In Swedish this chapter is called POME. The chapter contain these parts:
The product - an explanation of what the product will perform, which units are involved and the connection between these.
The process - the main process, part processes an their connection and the need.
Surroundings - the places and environments where the product should be used.
The human - who or which become users. And who becomes involved of the product, the human’s relation to the product and the interplay human-product.
5.1 Product (P)
The product is a module design to drive a serving cart forward. The module is supposed to work as a servo in order to relieve the load on the personal pushing the cart. Thereby injures caused by this operation is reduced.
5.2 Process (P)
Our product, the driving module’s, main task is to drive the serving-cart, forward and backwards. Its part-processes are drifting of the cart, lock/break the cart, charging of the cart (help-process) and cleaning of the cart (help-process).
Figure 5.1. This is a process tree, shows all the processes, included in our product.
Main process:
Drift the cart
Part process 2:
Lock/break the cart
Part process 1: Drift
of the cart
Part process 4:
Cleaning of the cart
Part process 3:
Charge the module
Battery power-indicator Bring Disconnect the breaks Disconnecting Bring human energy
Reconnect the breaks
Get the cart dry Bring water and perhaps cleaning liquid
Help processes
5.3 Surroundings (S)
The product will adjacent to the serving cart itself. The whole world is counted as the geographic area and the module must therefore resist all sorts of climate. The module’s working surroundings will be onboard a plane and a kind of industrial hall where they will be recharged, loaded with food or washed.
5.4 Human (H)
Air hostess – operator Passenger – involved
Airhostess – benefits from the use of the product Airport personal – Negative (recharge of batteries)
The product perform Drives the cart forward Locks the cart when it stops Loads the batteries
The personal performs
Plugs in the recharging device into the module Cleans the cart
Activate the direction control devices Disengage the module when desired
5.5 Economy (E)
The market price, price to customer, is decided to be 5500 SEK without VAT as a maximum price. An ordinary cart cost about 8000 SEK.
The cost for assembling the components is allowed to be no more than 1000 SEK. Mounting the module onto the cart isn’t included in this price. The components mustn’t cost more than 2000 SEK.
6 Product survey and criterion disposition
6.1 Product survey
There are no current solutions for a module for the flight carts, but there are some existing carts that are manufactured with electric drive. The patents for these carts will not interfere with our product.
We heard about a big cart at the hospital that was electric driven. So we went to the hospital to find that this cart was used to deliver newspapers and candy etc. This cart had a good solution; they had installed one motor with one wheel in the centre of the cart. So all the four wheels are free to rotate.
Christer Georgsson managed to arrange a meeting at the airport of Ronneby. Here we got access to the carts, where they were standing before take off. The carts were loaded with food and then they were taken to the plane. The forklift truck lifted the carts into the plane, through a sliding door on the side of the stairs.
6.1.1 SAS
During an interview with Peter Melander, SAS, we found out some interesting facts about how the carts were used. The daily use of a smaller cart is up to 3 flights a day. The treatment of these carts is
very hard. They are being dragged over thresholds with a height of up to 8 cm. The space inside the plane is very little and the carts may therefore bounce into the walls. Outside the plane they can fall onto the ground causing serious damage. Inside the catering kitchens they are quickly unloaded and reloaded. They are also washed here. We also found out that there are standards about flight equipment that can cause trouble during usage. The feeling we got from SAS is that the carts are being used without any consideration. We did also find out that the manufacturer of the washing equipment is Wexiödisk AB, in Växjö.
Results of the Questionnaire
Questions seen in Appendix [1 and 2] told us:
There is no change in holding positions between the small and the big cart, but if it was really heavy to move the big cart maybe the personal used a hip-push to get the cart moving.
Our conclusion is that all three different carts are pushed in the same way, holding the handles with two hands.
According to the answers there were no problems controlling the cart, pending on the size of the cart, on the other hand control problem could appear concerning the weight.
We also found that on top of the cart a possible basket with bread could be placed. There were no other comments or wishes.
Due to the low amount of participants in the survey there is no statistics made of the results.
6.1.2 Wexiödisk AB
To get information about how the carts are being washed and data we contacted Wexiödisk AB. There we talked with Gudrun Johansson on the sales department, she sent us all the information about their different washing machines. From these catalogues we could say that the model was a Trolley Washer WD-18CW, we got some criterions from the technical data in the information catalogue see Appendix 3-6.
6.1.3 Iacobucci
In order to receive a drawing with dimensions the company Iacobucci, one of the manufacturers of carts for SAS. We received the drawing from them shown in Appendix 13.
6.2 Criterion and wishes disposition
Notice that the wishes are marked with (W).
6.2.1 Functions or performance criterions
1. The module must be able to hold the pressure from the cart (representing a total force of 1100 N).
2. The module shall be easy to control.
3. The module must engage the parking brake automatically. 4. The module must be able to be disengaged, so the cart can be
pushed by hand.
5. The module mustn’t disturb the electronics in the plane, Electro Magnetic Compatibility, according to RTCA 160D. 6. The cart with two handles must have the function of
“master-slave” on each side.
7. The module must hold for hard treatment, for example transportation between the plane and the wash and when driving over thresholds (the only big threshold is the one when you enter the plane).
8. The module should be equipped with a battery power-indicator. (W)
9. All not-motorized wheels on the cart must remain free to rotate.
10. The stability of the cart should not decrease. (W)
6.2.2 Operation criterions
11. The module mustn’t change the height, width or length of the cart.
12. The module mustn’t change the storing-space in the cart. 13. The module must be waterproof according to the technical
specifications on Trolley Washer WD-18CW, see Appendix 3-5.
14. The module should have a life of ten years.
6.2.3 Personal safety criterions
17. The module must comply with existing safety regulations for example “Maskindirektivet, AFS 1994:48”.
6.2.4 Ergonomic criterions
18. The module mustn’t interfere with existing ergonomics.
19. The airhostesses shouldn’t need to perform difficult movements to drive the cart. (W)
6.2.5 Esthetical criterions
20. The module shouldn’t interfere too much with the look of the cart. (W)
21. The module should, if possible, comply with the colour of the existing cart. (W)
6.2.6 General design/production criterions
22. A low weight of the module is desirable. (W)
23. Modularity as far as possible, easy to exchange the different components/details. (W)
24. As few components inside the module as possible. (W) 25. Easy to assemble the module. (W)
26. Low cost is desirable. (W)
27. The module should be as effective as possible concerning the material use. (W)
6.2.7 Manufacturing criterions
28. The module should be designed for different sizes of carts. (W)
6.2.8 Disposal custody, sales and supplies criterions
29. Easy assembling on cart is desirable. (W)
6.2.9 Elimination criterions
30. All the parts should be able to be taken care of in a professional environmental correct way meaning no unusual materials.
6.2.10 Production economical criterions
32. Standard components should be used as far as possible. 33. The components mustn’t cost more than 2000 SEK.
34. The cost for assemble the parts mustn’t be more than 1000 SEK.
6.2.11 Users economical criterions
35. The price to for the customer mustn’t be more than 5500 SEK, without VAT.
6.3 Additional comments
In order to limit the time of the project it has been decided that when the following parts are finished, the project is finished:
Full report written including: Results
Drawings (both 3D and 2D)
We’ll make a model to show the function and outlining.
Parts excluded are the charging of the batteries, cables and the primary part of the steering device. Even small parts as screws and nuts will not be included.
7 Compilation of product proposals for module
7.1 Manner of operation
We have found two ways to operate the cart:
7.1.1 Electric motor
The first manner of operation contains an electric motor. Batteries provide the energy needed for the motor/motors. The motor is connected by a transmission to the wheel/wheels.
7.1.2 Compressed air
The second manner of operation is a compressor motor. An air pressure tank provides the energy for the motor. The flow is regulated with a valve. Due to safety regulations and economy this principal fails.
7.2 Design of the product
These design drawings are made for the smallest cart. They are fully usable even for the larger ones. But it might be to prefer a different design of the shell for each cart size.
Figure 7.1. This shell shows the maximum volume that is available.
Figure 7.1 shows the maximum volume available underneath the cart, designed for revolving movement of wheels and made to fit with existing brake pedals. This means that the module cannot be bigger than this.
Figure 7.2. This shell shows how the shell can look like when it’s designed.
Figure 7.2 shows an example of the final module shell, just to give a picture of the module outlining. Observe that for the final module changes will be made on the design, to make the driving module and batteries fit inside.
7.3 The products way of construction & primary
proposals
1 “Diagonal”
Figure 7.4. This picture shows the first proposal, “Diagonal”.
Figure 7.4: Two motors and no mechanical brake. The motors will brake effective enough. To disengage the driving module there must be a clutch between the motors and the driving wheels.
2 “TT4”
Figure 7.5. This picture shows the second proposal, “TT4”.
Figure 7.5: Two motors that are mounted in the centre of the module and all the four wheels in the corners are free to rotate. One thought here is that the motors can be driven separately when turning and together when driving straightforward. The existing mechanical brake will be modified but not disengaged. The motors in the centre should be placed on a lift, so the driving module can be disengaged and the pressure against the floor can be adjusted.
3 “T4”
Figure 7.6. This picture shows the third proposal, “T4”.
Figure 7.6: The module with one bigger motor in the centre, all the four wheels in the corners are free to rotate and the existing mechanical brake is not disengaged but modified. The motor in the centre should be placed on a lift, so the driving module can be disengaged and the pressure against the floor can be adjusted.
4 “FW”
Figure 7.7. This picture shows the fourth proposal, “FW”.
Figure 7.7: Two motors that are placed in the front, only two wheels are free to rotate and the existing brake will be left but modified. To disengage the driving module there must be a clutch between the motors and the driving wheels.
5 “TT3”
Figure 7.8. This picture shows the fifth proposal, “TT3”.
Figure 7.8: Two motors that are placed in the centre of the module. But these motors have their “driving wheels” along the long side and only three wheels that are free to rotate. The motors in the centre should be placed on a lift, so the driving module can be disengaged and the pressure against the floor can be adjusted.
6 “T3”
Figure 7.9. This picture shows the sixth proposal, “T3”.
Figure 7.9: Shows a proposal with on one bigger motor in the centre of the module, the existing brake (modified) and only three wheels that are free to rotate. The motor in the centre should be placed on a lift, so the driving module can be disengaged and the pressure against the floor can be adjusted.
7 “TT2”
Figure 7.10. This picture shows the seventh proposal, “TT2”.
Figure 7.10 is equipped with two motors as in figure 7.8. But there are only two wheels that are free to rotate. The motors in the centre should be placed on a lift, so the driving module can be disengaged and the pressure against the floor can be adjusted.
8 “ST”
Figure 7.11. This picture shows the eight proposal, “ST”.
The last proposal, figure 7.11 shows a geared motor placed in the centre of the module, further like in figure 7.6. The motor in the centre should be placed on a lift, so the driving module can be disengaged and the pressure against the floor can be adjusted.
8 Evaluation of the product proposals of module
8.1 Advantages and disadvantages of the
proposals
Below we list about what’s good or bad with the different proposals. Advantages are marked with (A) and disadvantages are marked with (D).
8.1.1 “Diagonal” (1)
(A):- Much space left for batteries
(D):
- Only two wheels are free to rotate → hard to make narrow turns - Two motors - Clutch is needed - Brakes?
8.1.2 “TT4” (2)
(A):- Four wheels, which are free to rotate - Motor brake
- The existing brake is used and will also be used to raise and lower the motor module
(D):
- Two motors
- A lift is needed to engage/disengage the motor - Separate steering-device on the two motors
8.1.3 “T4” (3)
(A):- Four wheels, which are free to rotate - Motor brake
- The existing brake is used and will also be used to raise and lower the motor module
(D):
- The size/volume of the motor?
8.1.4 “FW” (4)
(A):- We can use the existing brake
- The cart will be easy to control when going straight forward
- Not four free wheels → hard to make narrow turns - Two motors - Clutch is needed
8.1.5 “TT3” (5)
(A): - Easy to turn- The cart will be easy to control when going straight forward
- The existing brake is used and will also be used to raise and lower the motor module
(D):
- Two motors - Separate steering
- The cart will be easy to tip
8.1.6 “T3” (6)
(A):- The existing brake is used and will also be used to raise and lower the motor module
(D):
- Choice of the motor? - The cart will be easy to tip
8.1.7 “TT2” (7)
(A):- The cart will be easy to control when going straight forward
- Easy to turn
(D):
- Two motors
- The cart will be easy to tip - No existing brake
- Clutch is needed - Instability sideways
8.1.8 “ST” (8)
(A):
- The existing brake is used and will also be used to raise and lower the motor module
- Four wheels are free to rotate - Motor brake
(D):
- Motor volume?
8.2 Evaluation
The evaluations of the proposals are, according to the Fredy Olsson-model, subdivided in three steps:
Primary evaluation: many proposals, which are compared to the main criterions, if they don’t fulfil these they fall out.
Intermediate evaluation: further development of the proposals and a more detailed evaluation
Final evaluation: only two to four proposals will exist, on these proposals calculations and principal tests will be performed.
8.2.1 Primary evaluation
In this stage we compare the demands with our different proposals, are there any proposals that don’t fulfil our demands they fall out.
Technical demands
- The module must be able to hold the pressure from the cart (max 1100 N).
- The module shall be easy to control.
- The module must be self-locking and work as a brake.
- The module must be able to be disengaged, so the cart can be pushed by hand.
- The module mustn’t disturb the electronics in the plane, Electro Magnetic Compatibility.
- The cart with two handles must have the function of “master and slave” on each side.
- The module must hold for hard treatment, for example transportation between the plane and the wash and when driving over thresholds (the only big threshold is the one when you enter the plane).
- The module mustn’t change the height, width or length of the cart. - The module mustn’t change the storing-space in the cart.
- The module must be waterproof according to IP 56 (SS ENC 60529).
- The module should have a life of ten years.
- The module must resist the 85-degree Celsius water that is used to wash the cart.
- The module must resist the pressure from the water that the washing machine produces, 0.3 Mpa/30litre/min.
- The module must comply with existing safety regulations. - The module mustn’t interfere with existing ergonomics.
- All the parts should be able to be taken care of in a professional environmental correct way meaning no unusual material.
Economical demands
- Standard components should be used as far as possible. - The components mustn’t cost more than 2000 SEK.
- The cost for assemble the parts mustn’t be more than 1000 SEK. - The price to for the customer mustn’t be more than 5500 SEK, without VAT.
Below you can see a solution classification according to the “direct group method”.
TECHNICAL DEMANDS Group scale
6 fulfil the demands for certain 5
4 probably fulfil the demands 3
2 hardly fulfil the demands 1
0 do not fulfil the demands
ECONOMICAL DEMANDS Group scale
6 fulfil the demands for certain 5
4 probably fulfil the demands 3
2 hardly fulfil the demands 1
0 do not fulfil the demands
No. PROPOSAL Description TC EC ∑ Goes trough (Y/N) 1 Diagonal 0 4 4 N 2 TT4 5 3 8 Y 3 T4 4 4 8 Y 4 FW 0 4 4 N 5 TT3 2 3 5 Y 6 T3 2 3 5 Y 7 TT2 2 3 5 Y 8 ST 4 3 7 Y
Table 8.1. This table shows the first evaluation of the proposals and which ones that goes through.
Proposals number one (Diagonal) and number four (FW) don’t fulfil the main criteria 9 (all not-motorized wheels on the cart must remain free to rotate). So these two proposals won’t go through to the next evaluation.
8.2.2 Intermediate evaluation
We went to “Coop Forum”, a supermarket in Karlskrona, to take a look on their carts. They have storing carts with only three wheels and this size gives no problem but if they would be shorter, like our carts, we all agreed that it would be problems with the stability.
Proposals number six (T3) and number seven (TT2) does not fulfil the main criteria 10 because of the instability. Also number five (TT3) will fall for this criteria depending on how the cart will be loaded with its contents.
The remaining proposals are number two (TT4), number three (T4) and number eight (ST).
8.2.3 Final evaluation
Final assessment of wishes according to the ”compare method in pairs”
A: The module should be equipped with a battery power-indicator B: The airhostesses shouldn’t need to perform difficult movements to drive the cart
C: The module shouldn’t interfere too much with the look of the cart D: The module should, if possible, comply with the colour of the existing cart
E: A low weight of the module is desirable
F: Modularity as far as possible, easy to exchange the different components/details
G: As few components inside the module as possible H: Easy to assemble the module
I: Low cost is desirable
J: The module should be as effective as possible concerning the material use
K: The module should be designed for different sizes of carts L: Easy assembling on cart is desirable
M: The cart should be restorable
8.3 Evaluation through tests/experiments
An experiment has been done to verify the function of some proposals. The most critical moment is the proposals with a middle centred wheel. The problem with these is the friction. There has to be enough friction to start the cart and to brake the cart safely. The following equipment were used during the experiment:
Big cart Small cart Dynamometers
Carpet similar to the carpet on airplanes Scale
A plate to generate the slope
The experiment was performed with following conditions:
The plate formed an angle with the floor, approximately 15°. Both carts were pushed containing their maximum load. During the second part of the test the slope was approximately 10°.
Cart Slope (%) Slope (°) Total weight (kg) Pushing force (N)
Big cart 33 15 120 400
22 10 120 300
Small cart 33 15 90 350
22 10 90 250
Table 8.3. This table show what force is needed to push the different carts in different slopes.
Results from the experiment:
During the product survey the highest slope found when serving was 22%. Dimensioning the motor for the higher slope will probably secure the module from unknown types of use. The highest needed pushing force is 400 N. The reliability of the test is good. The carpet used has a surface, which is quiet thicker, than the carpet used in a plane.
8.4 Second test
The need for the brake to withstand the pressure during take-off has also been tested. The wheel that is possible to use on the proposals with a middle centred wheel is similar to the existing wheels on the cart. Therefore the small cart was used in this test. The test was performed on the carpet with no slope what so ever.
Because of the ”primitive” equipment the test wasn’t fulfilled. When the pushing force exceeded 400 N the carpet started to move. Calculations for the big cart fully loaded standing in a slope of 33% shows that the brake has to hold for maximum 300 N. The test-results give 400 N and then the carpet starts to move.
The approximation with reality is good except for the surface of the carpet. It’s possible that the carpet inside a plane is more slippery.
8.4.1 Evaluation through calculations
The first approximation of the necessary power to drive the big cart
Data:
Max gross weight 90kg Max empty weight 27kg Total weight 117 Kg
We use the Dynamical Mechanical Principal
∑
F = mδ
(1)According to the plan organisation we wanted to use 1s to accelerate to the max speed, about 3km/h:
2 3 / 83 , 0 3600 10 3 s m dt dv = × = =
δ
(2)Using result from (2) in equation (1) N
Fa =120×0,83=99,6 (3)
This is the force, which is necessary to drive the cart without friction and slope.
We have done many tests about ability to move the cart on different carpets with a slope about 30%: We need to have a force about 400N.
We can now calculate the necessary power to drive the cart on the carpet:
Notice that the acceleration and the speed have the same value because of the acceleration time 1s.
v
F
P
=
×
(4)Using the result from (2) in equation (4)
W P=400×0,83=332
Now you can calculate the torque to drive the cart:
If we decided to use a eight-centimetre diameter wheels:
r
×
π
2
(5), gives the distance per rotation Using the equation (5)r m / 25 , 0 10 4 2π× × −2= (6) With a speed of 0,83 m/s: 3,32rps 25 , 0 83 , 0 = (6) f × = π ω 2 (7)
Using result from equation (6) in equation (7)
s rad / 86 , 20 32 , 3 2 × = =
π
ω
(8)ω
×
=
M
vP
(9)Torque from the out axle of the reducer Nm P Mv 15,92 86 , 20332 = = = ω (9)
The first approximation of the necessary power to drive the small cart
Data:
Total weight 80 Kg
We use the Dynamical Mechanical Principal
∑
F = mδ
(1)According to the plan organisation you wanted to use one second to accelerate to the max speed about 3km/h:
2 3 / 83 , 0 3600 10 3 s m dt dv = × = = δ (2)
Using result from (2) in equation (1) N
Fa =80×0,83=66,4 (3)
This is the force, which is necessary to drive the cart without friction and slope.
We have done many tests about ability to move the cart on some different carpet with a slope about 30%: We need to have a force about 350N.
You can now calculate the necessary power to drive the cart on the carpet:
v
F
P
=
×
(4)using result from (2) in equation (4)
W P=350×0,83=290
If we decided to use a 8cm diameter wheels: Using equation (5) r m / 25 , 0 10 4 2π× × −2= (6)
Using result from (4)
With a speed of 0,83 m/s: 3,32rps 25 , 0 83 , 0 = (6) f × = π ω 2 (7)
Using result from (5) in equation (7)
s rad / 86 , 20 2 32 , 3 × = =
π
ω
(8)ω
×
=
M
vP
(9)Torque from the out axle of reducer; result from (7) in equation (8) Nm P Mv 13.9 86 , 20290 = = = ω (9) Compilation Table
Small Cart Big Cart
Power 290 W 332 W
Torque 13,92 Nm 15,92 Nm
Conclusion:
Finally with the efficiency of the reducer and its reduction rate we can determinate the motor torque and rotation speed for the calculated power.
This is an approximation because we don’t use the inertial and the friction coefficient and we use some experimental result but this enough for determine the first prototype.
8.4.2 Energy needed for the serving cycle
We have created an excel sheet (See Appendix 8 & 9) which uses a recursive least square mathematic method and the dynamical mechanical principal: F=m*dv/dt in order to calculate the needed torque and energy during a cycle of use. According to this result and the others from the first approximation we have determined the different parameter for motor and battery. This test was performed with the cabin configuration from the Boeing® 737-700 used by SAS. See on Appendix 7: the Cabin Configuration.
The cabin personal use 2 carts from the both ending of the plane and they stop serving at the middle of the plane. The cabin configuration (Appendix 7) gave us the seat organisations as shown in figure 8.1
Figure 8.1. Seat Organisations
At the speed of 3 km/h = 0,83m/s we can use this first approximation: 1s between 2 seats and 2 between the kitchen and the first seat.
6 seats
2 m
Cycle Time of use:
• 2s in forward motion between the kitchen and the first seat. • 1s between 2 seats during 10 seats to the middle of the plane. • 10s break for serving the food
• 11s in backward motion for return to the Kitchen.
We have done this test with the 2 different Cart for a slope of 30%, which is the maximum slope during the serving time.
See on the Appendix 8 & 9 the calculation sheet.
Compilation Table
Small Cart Big Cart
Maximum Power 210 W 314 W Maximum Torque 9,5 Nm 14,1 Nm Total Energy 4,37 kJ 1,21 Wh 6,55 kJ 1,82 Wh Energy using 24 V 0,051 Ah 0,076 Ah Number of Cycles using 24 V 69 46 Energy using 12 V 0,101 Ah 0,152 Ah
Number of Cycles using
12 V
35 23
Table 8.5. This table show the energy consumption.
The maximum discharge is calculated for less than 50% of the capacity, for the deepest discharge, the battery could be damage. This result is for a 7Ah battery, which fulfil our demand.
Conclusion
This calculation is an approximation because the wheels friction and the air penetration are missed. Furthermore these results are enough precise to fulfil our demands. These results permitted us to define the motor and battery parameters in order to make the good choice. We have to choose components, which fulfil these criterions.
9 Lift development
9.1 Function of the lift
Our thoughts are to make the module able to work as planned:
The module is supposed to be self-braking when the handles are inactivated and move when controlled by the handles, still should the cart be able to move as present when the brake is deactivated. This function can be reached by two different methods:
Clutch: Between the motor and driving wheel a clutch is placed and the existing brake is used for parking brake, this method demands either a lever or pedal to control the clutch.
Lift: The driving wheel is lifted up when existing pedal for deactivating brake is pushed, thereby the motor brake is deactivated and since the brake on the existing wheels is permanently disabled the cart can move freely. The motor brake is used both for self-brake and parking brake of the cart. The driving wheel is making contact with the floor when pushing down existing pedal for activating the brake.
According to the limited space for lever or new pedal the clutch method will be rejected.
9.2 Criterion disposition for lift
The same criterions as for the module including the criterions below will be valid for the lift.
Wishes marked (W) and demands marked (D).
• Plain construction (W) • Sturdy construction (W) • Compact construction (W) • Use existing pedals (D) • Reliable construction (D) • Fit according to space (D)
9.3 Lift proposals
To protect the driving module against threshold damages we will add a suspension to all the proposals.
Figure 9.1. Shows the “twin”.
Proposal no.1 (figure 9.1): the “Twin”, using the principle of deformable parallelogram. When pushing the pedal you engage the drive module by deformation of the parallelogram. The lifting module could be frail sideways and claims much space.
Figure 9.2. Shows the “slider”.
Proposal no.2 (figure 9.2): the “Slider”. The slope between the oblong hole and the plate of the cart allows the lifting of the motor reducer. Easy to manufacture and made as a sturdy construction.
Figure 9.3. Shows the “big belt”.
Proposal no.3 (figure 9.3): the “Big Belt”. Similar function as “Slider”, but here only the wheel is moved. Sturdy construction, easy to manufacture.
Figure 9.4. Shows the “tilt”.
Proposal no.4 (figure 9.4): the “Tilt”. A lever controlled by the pedals generates the lifting and lowering. The lifting module could be frail sideways and claims much space.
Figure 9.5. Shows the “scissor”.
Proposal no.5 (figure 9.5): the “Scissor”, using the principle of scissors. By pushing the pedals you lift and lower the driving module. The lifting module could be frail sideways and claims much space.
9.4 Evaluation of lift proposal
TECHNICAL DEMANDS Group scale
6 fulfil the demands for certain 5
4 probably fulfil the demands 3
2 hardly fulfil the demands 1
ECONOMICAL DEMANDS Group scale
6 fulfil the demands for certain 5
4 probably fulfil the demands 3
2 hardly fulfil the demands 1
0 do not fulfil the demands
No. PROPOSAL Description TC EC ∑ Goes trough (Y/N) 1 “Twin” 2 3 5 N 2 “Slider” 5 4 9 Y 3 “Big Belt” 3 4 7 N 4 ”Tilt” 3 3 6 N 5 ”Scissor” 2 3 5 N
Table 9.1. The evaluation of the lift proposals.
Conclusion
According to the result of the proposal evaluation we choose solution no.2.
The “Big Belt” solution doesn’t allow us to use gearbox because of the construction. Contrary has the “Slider” solution where we can choose which transmission will be the best for starting torque, speed rotation and low noise.
10 Steering device development
10.1 Function of steering device
The function is to control the power to the motor. The device mustn’t be able to steer the cart, just control the forward and backward movement. It’s desirable that the steering device has the same function as a servo. When the cabin personal start to push the cart the motor helps proportional to the pushing force.
On the big carts where two devices are needed, one on each handle, their function in between should be “master and slave”. During a stop both devices goes high. The device first activated becomes master and the other becomes slave.
10.2 Criterions for steering device
The same criterions as for the module inclusive the criterions below will be valid for the steering device. Wishes marked (W) and demands marked (D). • Safe construction (D) • Easy to control (W) • Sturdy construction (W) • Reliable construction (W) • Servo function (W)
10.3 Steering device proposals
10.3.1 Manner of operation
5 different ways to control the power to the motor has been found. Switches can be both analogue and digital.
• Thread stretching device • Toggle switch
• Revolving switch • Slide control switch • Micro gap switch
10.3.2 Proposals
Figure 10.1. Shows the “roller”.
Proposal no.1 (figure 10.1) shows the “Roller”. By revolving the circular handle the power to the motor is changed. The handle is only free to rotate around its centre axis. The proposal is using a revolving
switch and therefore the regulation is variable. This solution cannot be used a servo.
Figure 10.2. Shows the “button”.
Proposal no.2 (figure 10.2) shows the “Button”. The two buttons is for movement back and forth. They can be variable or with step regulation. The switch is an ordinary “pressure” switch. This solution cannot be used a servo.
Figure 10.3. Shows the “press”.
Proposal no.3 (figure 10.3) shows the “Press”. The picture is seen from above. With your thumbs you can regulate the forward movement by pressing the switch. When dragging the cart behind you the switch on the other side will be activated. This is not a real servo
but closer to a servo than proposal 1 and 2. The switch on the front can cover the whole handle and therefore be activated by the drivers’ palms.
Figure 10.4. Shows the “mover”.
Proposal no.4 (figure 10.4) shows the “Mover”. The picture is seen from above. The handle is supposed to slide on a track on the sides of the cart. The handle can slide both forward and backwards. Springs control that the handle returns to the starting position. This proposal is supposed to work as servo. When the driver push with a force of, for example 10 N, the motor is powered and helps the driver.
Proposal no.5 (figure 10.5) shows the “Angle”. The handle controls a toggle switch. When the driver push the cart the handle tilt a small angle which gives the signal. This principal is working for both backward and forward motion. This solution will also work as a servo.
Proposal no.6 is called the “Strain”. Because of the simplicity in the picture it was decided not to draw a picture. The handle is supposed to remain as it is. The strain gage should be hidden inside the handle. The strain gage gives signals when the handle is touched. The sensitivity can be adjusted to fit our purpose. There may be problems with the extension of material when the carts are stored in cold places and enters a warm plane. There also has to be a device that resets the hardware.
10.4 Evaluation of steering device proposals
TECHNICAL DEMANDS Group scale
6 fulfil the demands for certain 5
4 probably fulfil the demands 3
2 hardly fulfil the demands 1
0 do not fulfil the demands
ECONOMICAL DEMANDS Group scale
6 fulfil the demands for certain 5
4 probably fulfil the demands 3
1
0 do not fulfil the demands
No. PROPOSAL Description TC EC ∑ Goes trough (Y/N) 1 Roller 3 2 5 N 2 Button 5 5 10 Y 3 Press 5 4 9 Y 4 Mover 4 4 8 Y 5 Angle 4 4 8 Y 6 Strain gage 2 3 5 N
Table 10.1. This table show the evaluation of the steering device.
10.5 Conclusion
For now proposals 2-5 will be taken to the primary construction phase. Further development on the proposals will be done after an evaluation with the customer. If the evaluation concludes that a handle with servo function is to prefer these will be developed further.
11 Presentation of final proposal
The chosen proposals will be presented with picture and explanatory text. These proposals will be further developed in the next phase, the primary construction phase. The principals will be presented in order of appearance in the report.
11.1 Module proposals
Two module proposals were taken to the primary construction phase, the “T4” and the “ST”. Both proposals fulfil the demands and the wishes.
Figure 11.1. This figure shows the proposal called “T4”.
Figure 11.1 shows the “T4”. A wheel in the middle of the cart with a motor and a clutch gives the needed power to drive all the different carts. The lifting device is easily fitted and the manoeuvrability of the lift is good and controlled with the existing brake pedals. The clutch is supposed to give the needed braking torque. Advantages with this module are that all four existing wheels are free to rotate. Since the driving wheel is hidden inside the module when lifted the reliability of a good function increases.
Figure 11.2. This figure shows the other proposal, the motor is turned 90 degrees.
Figure 11.2 shows the second proposals. This module also has one wheel (or 2 wheels) in the middle but the motor has a 90° clutch in order to provide more space on both sides of the middle wheel. The two proposals are quiet similar but the brake is more easily arranged on this proposals. Two wheels instead of one can give a better friction if so needed. Other advantages on this proposal are same as on the first one. All four wheels are free to rotate and the middle wheel is protected with the lift.
11.2 Lifting device proposals
Only one proposal of five was taken to the primary construction phase. The chosen proposal has big advantages compared with the other suggestions. The possibility to use different transmissions without changing the lift was a favourable quality. The lifting is easily performed and the existing brake pedals can be used with small modifications. The lift fulfilled all the written criterions, for example sturdy construction and yet small dimension. Figure 11.3 shows the chosen architecture of the proposal.
Figure 12.3. This figure shows the sliding lift.
11.3 Steering device proposals
Five ways to control the signal were found and six ways to control the switches were found. Of these proposals four fulfilled all the demands. One wish was that the steering device should work as a servo. Further evaluation with the customer and tutors will be done in this matter.
Figure 11.4. This is a better figure of the second proposal, the “button”.
Figure 11.4 shows the first proposal, which got through, the “Button”. The two buttons is for movement back and forth. They can be variable or with step regulation. The switch is an ordinary “pressure” switch. It
is an easy construction and the components aren’t expensive. The understanding of how the steering device is controlled is also very easy. The problem is that this cannot work as a servo.
Figure 11.5. This is a better figure of the press proposal.
Figure 11.5 shows the “Press”. Pressing with thumbs or palms regulates a switcher in the front of the handle. Another switcher is regulated when the cart is being pulled. This proposal is probably more expensive than the buttons but the function is almost like a servo. This way of controlling the cart will be rather natural.
Figure 11.6. Shows the “mover”.
Figure 11.6 shows the “Mover”. The handle is supposed to slide on a track on the sides of the cart. The handle can slide both forward and backwards. Springs control that the handle returns to the starting position. When the driver push with a force of, for example 10 N, the motor is powered and helps the driver. The function of this device is as similar to as servo as possible.
Figure 11.7. Here you can see a better figure over the “mover”.
Figure 11.7 shows the inside of the proposal “Mover”. As seen in the picture the handle can slide in the track.
Figure 11.8. This figure gives a better overview of no. 5, the “angle”.
Figure 11.8 shows the “Angle”. The handle controls a toggle switch. When the driver push the cart the handle tilt a small angle which gives the signal. This principal is working for both backward and forward motion. The servo function is obvious. A sturdy construction of the handle is needed to get “the right feeling”.
11.4 Conclusion
All the proposals taken to the primary construction phase has potential. The possibility of a well-working module with the lift and
steering devices suggested are good. The application can, in this stage, be modified with a steering device that the customer prefers without delaying the project.
12 Product Concept
Figure 11.9. This figure shows the whole module and the available volume. 425m 300m Electric Motor Reducer Free Wheels Lifting device Driving Wheel Lift Control
The module will be protecting against exterior injury by a shell. This shell should be contain and protect all the module elements.
12.1 Specification of the parts
Part Treatment Standard/unique
Motor Routine Standard
Transmission Special Standard
Driving Wheel Routine Standard
Switcher Routine Standard
Electric control device Routine Standard
Battery Routine Standard
Lifting device Special Unique
Cables Routine Standard
Table 12.1. This table shows the parts, which are included in the module. Here you can see if they have to be manufactured by us or if they can be bought.
13 Choosing components
13.1 Criterions on module
Electric Motor: Firstly, it should be able to transform electric energy in rotation movement. Secondly, it shall provide the necessary torque and speed rotation without injury. Thirdly it’ shouldn’t disturb the electronics inside the plane. Finally, it needs to fit inside the shell because of the small space available under the cart.
The calculations made for the motor sets the limits. For example we see that the highest needed power is close to 300W, the highest torque is 16 Nm (on the wheel) and then we have some criterions concerning the space. With the different ways to arrange the motor we have found the diameter to be no larger than 90 mm and the length 210 mm (gear head included). When using a motor that has a large diameter but the length is decreased the dimension are 160 mm in diameter and a length of 90mm (gear head included).
Transmission: Firstly, it should be enough strong for working with the motor specifications. Secondly, it should be able to transform the high motor speed rotation to the necessary speed which is 200 rpm. Finally it should be enough small to stay in the shell. As mentioned the highest torque is 16 Nm.
Driving Wheel: Firstly, it should be able to transmit rotation speed in the carpet without slide. Secondly it should be able to brake the cart on a usual slope (For example: during a plane take off). It should stand a load of 500 N. Finally it should be contents in the shell designed for module protection.
Switcher: Firstly it should be able to control the direction of the cart according to the security airplane specification. Secondly it should be ergonomic and easy to use for reduce the airhostess injuries. Finally it should be added on the cart without any modification.
Electronic control device: Firstly like the electric motor it shouldn’t disturb the electronic device available inside the plane. It should respect the EMC rules. Secondly it should allow controlling the speed and rotation in order to change the cart direction.
Battery: Firstly it should be able to provide the necessary power to drive the full cart in the worst conditions. Secondly it should have the necessary autonomy to drive the cart during the flight. Finally it should be small enough to stay inside the shell. Calculations on needed battery
