System PASS 1 1 Performance AutoShift System This product is a new form of automatic shifting system Works with mechanical derailleur systems and off the shelf drivetrains Requires limited to no retrofitting of a bicycles preexisting components ID: 302585
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Performance AutoShiftSystem(P.A.S.S.)
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1: Performance AutoShift SystemThis product is a new form of automatic shifting system
Works with mechanical derailleur systems and off the shelf drivetrains
Requires limited to no retrofitting of a bicycles preexisting components
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GoalCreate a product that can be used in higher performance cycling, specifically cross country mountain biking where frequent, well timed shifting is important
Minimize cost
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AudienceConsumers looking for a relatively inexpensive alternative to high priced electronic shifting systems such as Shimano Di2 or Campagnolo EPS
Those wanting the added benefit of automatic shifting
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2: Project Driving RequirementsPower, speed and cadence based shifting.
Eliminate unwanted shifting that may reduce ride performance or potentially damage the bicycle drive train or shifting system.
Simple data recording for maximum and average speed, maximum and average cadence, total distance, total time.
Programmable optimum cadence range, gearshift indexing, etc.
Optional user selected shifting.
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User Interface RequirementsA user instruction manual should be made to assist the user with installation and use. This document should also include a list for trouble shooting and solutions to problems.The control unit is to be mounted on the handlebar stem or on the handlebars.
The control unit must have a clearly visible screen to display useful data to the user
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User Interface Requirements cont.The system is to have a user controlled on handlebar multiple button input device, which will be used in the initial system setup and for information display selection.The user must also be able to manually change gears with on handlebar shift buttons that are accessible while the user has their hands on the handlebar grips.
The system should be easy to learn.
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Performance RequirementsChange to selected gear in less than 0.25 secondsOperate in a temperature range of -30°C to 50°C
The motor must be able to pull at a force of at least 36.7 N.
The total weight of the system should less than 1.4 kg, with a goal weigh of less than 0.7 kg.
The system should be able have presets of both specific derailleur gear indexes and rider preferences.
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Capacity RequirementsRecorded data is to be stored on a removable flash card. The flash card should have a minimum storage capacity of 512Mb.Battery must be able to last at least 2 hours and have a capacity of 2Ah
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Monitoring RequirementsDetect errors of input/output and display on the on the screen.Report the current gear, current and average speed, current and average cadence, total distance and time.
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Maintenance RequirementsThe control unit, motor unit and remote controls are to be modular and individually replaceableThe motor unit parts are to bar easily replaceable or able to be rebuilt
Cables and housing are to be off the shelf bicycle cables
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System Requirements Matrix12Slide13
Out of ScopeModification of the control unit so that it can interface with mobile based applications.Modification of the microcontroller storage so that data is stored for later manipulation in a map/workout generating software
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3: High Level SystemIntended to integrate into a bicycles existing drivetrainIt will work with the derailleur, chain and cassette that are already installed on the bicycle
The controls and control unit are simply mounted to the handlebars
The sensors are fastened to their specified locations and the motor unit is attached to the bicycles bottle cage mounts or some alternative location on the bicycle frame.
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High Level System Diagram15
Control Unit
User Input
Controls
Sensors:
Cadence
Speed
Power
Etc
.
Display
Motor
Unit
Derailleur
Performance AutoShift System
Cassette
Chain
Existing Bicycle Drive Train
Shift CableSlide16
Power/Data Schematic16
Control Unit
Sensors:
Cadence
Speed
Power
Etc.
.
Display
Motor
Unit
User Input
Controls
Voltage
Regulator
Ground
7.2 V+
3.3/5 V+
Input
OutputSlide17
AssumptionsImplemented with regularly accessible cycling components that can be purchased by the general publicComponents include the derailleur, gear cable and housing (Bowden cables), and handlebars.
Designing the system basic to advanced programming techniques will be implemented
The sophistication of the system will depend on the limitations of the team to program the microcontroller in the control unit of the system
User will be able to determine a cadence that is appropriate for their riding style.
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Assumptions cont.User must also understand that the systems automatic shifting is limited to its preprogrammed shifting characteristicsExtreme shifting scenarios will require the user to manually select the gear shifting time.
A user that is installing this system should have access to tools regularly available in a bicycle shop and most households
Allen keys, screwdrivers, socket wrenches, cable cutters and a bicycle work stand
A user should also have knowledge of how to correctly adjust a bicycle for the system to function properly.
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Assumptions cont.Cost to design and implement this product must be affordable to design and build The target maximum cost per team member is approximately $150
The design, test, implementation and completion of this project must also follow the project schedule
Must be completed before the end of second semester of the Senior Design course.
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ConstraintsProgramming languagesC++
C
Assembly Language
The system requires a specialized Lithium Polymer charger to safely charge.
Access to mountain bike trail is needed for testing
The system must not exceed the limitations of the motor.
The system must not exceed the limitations of the battery.
The system must not exceed the limitations microcontroller
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Microcontroller Constraints 21Slide22
Motor Constraints 22Slide23
Battery Constraints23Slide24
DependenciesMaximum speed of the motor under load of the derailleur must be known before the control unit can be accurately programmed to control the shifting.The sensors need to be calibrated before measurements can be taken and interpreted into useful data.
The external user interface needs to be built before any advanced field-testing can be made.
The chain, rear cogs and front chain rings must be in acceptable condition and not over worn. If this is not maintained the system will not shift correctly even if the bicycle is reverted to the original shifting system.
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Dependencies cont.The cables must be maintained, lubricated and in good condition.The motor gear unit should be lubricated to reduce additional loss in efficiency from unwanted friction.
The battery must maintain a voltage high enough to not adversely affect the systems voltage regulators and microcontrollers minimum voltage level.
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User ScenariosThis product is for a user that wants the benefits of electronic shifting without the need to purchase a bicycle component set that costs thousands of dollars.With the benefit of electronically controlled shifting it also has the advantage of automatic shifting to the best gear ratio for the best performance.
P.A.S.S. eliminates the need for a separate cycling computer to provide ride feedback.
There is no need to buy any additional parts because the system can be implemented to any standard bicycle drivetrain.
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4: Project Technical TradesTechnical trade study plan addresses design drivers and component alternatives, and an appropriate closure plan has been provided for studies that remain open
These is where you capture things that the team is trading, i.e.., Bluetooth interface over wires or other interfaces. At PDR all these trades needs to be closed and results have to be presented.
Please documents these trades in your action register and track them
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Project Technical TradesScrapped Lidar triangulation for terrain noting premeditative shifting isn’t necessaryMoved from stepper/servo to a brushed motor with a worm drive to eliminate stiction and increase battery life
Servos need current to hold position
Worm drive allows us to turn the motor off after it’s in position
Moved from Arduino to Teensy for a smaller design
Implemented a potentiometer to eliminate the need for a positional marker we initially used the stepper for
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5: Project Testing: Cable Pulling Sys29
Requirements to be Tested:
1. Worm drive system must overcome 36.7 Ns of pull force from the derailleur and calculate maximum motor speed with full load
2. Motor must oppose stiction (pull-back) without consuming too much power
3.
Change to selected gear in less than 0.25 secondsSlide30
Project Testing: Cable Pulling SysWorm drive system must overcome 36.7 Ns of pull force from the derailleur and calculate maximum motor speed with full loadA test will be implemented with the load of the derailleur opposing the worm drive
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Project Testing: Cable Pulling Sys
2. Motor must overcome stiction (pull-back) without consuming too much
power.
The stiction should be eliminated by having an appropriate worm drive. This will be tested along with the load-baring tests.
Hand calculations and autocad designs will be implemented to find “safe” ranges for each of the variables and hardware will be ordered for testing with a static load.
3. Change to selected gear in less than 0.25 seconds
The range-time limit can be adjusted with different pitches, diameters, and lengths of the worm drive. This will be approximated and then tested with a few variations of worm-drives.
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Project Testing: Power MeterRequirements to be Tested:Must calculate torque
Must use torque to calculate required gear ratio
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Project Testing: Power Meter33
Torque must be calculated
Inside the pedals there must be strain gages
Testing the strain can be done using strain gages, a DAQ, and LabVIEW program mapping each pedal with respective force.Slide34
Project Testing: Power Meter2. Must use torque to calculate required gear ratioAfter torque calculations are complete it must be compared with the gear ratio for the bike, this will be calibrated for an ideal shift. This may have to be done by riding the bike with the power meter and noting a comfortable gear ratio for each speed and cadence.
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6: Project Risk
Inherent Risks:
No water resistivity
Fragility
Out of initial scope; requires additional time
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Project RiskProgrammatic Risks:
Budget:
Power meter parts could be more costly than expected
Temperature may affect the strain reading
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Project RiskImplementation Risks:
Funding
Not enough income
Part time jobs
Management
Behind on schedule
Lack of communication
Developmental
Compatibility between devices and components
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Probability (Likelihood)
1
0
Consequence
Schedule
Incomplete
Premature
x
x
High Risk – Severe disruption expected to performance, cost, and / or schedule even with risk mitigation plans in place.
Moderate Risk –Expected disruption to performance, cost, and / or schedule can be overcome by implementing risk mitigation plans.
Low Risk – Little disruption expected to performance, cost, and / or schedule.
Risk of Schedule
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Probability (Likelihood)
0
Consequence
Performance
x
Risk of Performance
x
x
Exceeds Expectations
Nonfunctioning
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Probability (Likelihood)
0
Consequence
x
x
Cost
> $500
< $150
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7: Preliminary ScheduleSlide42
8: Bill of Material (BOM)42Slide43
9: Review Action Items43Slide44
Thank you!Website Link:
http://
autoshiftsystem.weebly.com
/
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