EEL 4906.001 - Engineering Design1, Jamal Haque Ph.D. Performance AutoShift System (P.A.S.S.) 1.

EEL 4906.001 - Engineering Design1, Jamal Haque Ph.D.

Performance AutoShiftSystem

(P.A.S.S.)

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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

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Goal

➢ Create 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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Audience

➢ Consumers 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 Requirements

➢ Power, 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 Requirements➢ A 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 Requirements➢ Change to selected gear in less than 0.25

seconds➢ Operate 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 Requirements➢ Recorded 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 Requirements➢ Detect 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 Requirements➢ The control unit, motor unit and remote controls

are to be modular and individually replaceable➢ The 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 Matrix

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Out of Scope➢ Modification 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 System➢ Intended to integrate into a bicycles existing

drivetrain➢ It 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 Diagram

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Control Unit

User InputControls

Sensors:Cadence

SpeedPower

Etc.

DisplayMotorUnit

Derailleur

Performance AutoShift System

Cassette

Chain

Existing Bicycle Drive Train

Shift Cable


Power/Data Schematic

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Control Unit

Sensors:Cadence

SpeedPowerEtc..

DisplayMotorUnit

User InputControls

VoltageRegulator Groun

d7.2 V+3.3/5 V+InputOutput


Assumptions➢ Implemented with regularly accessible cycling

components that can be purchased by the general public➢ Components 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 characteristics➢ Extreme 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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Constraints➢ Programming languages

➢ C++➢ 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

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Motor Constraints

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Battery Constraints

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Dependencies➢ Maximum 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 Scenarios➢ This 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 Trades➢ Technical 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 Trades➢ Scrapped Lidar triangulation for terrain noting

premeditative shifting isn’t necessary➢ Moved 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 Sys

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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 load2. Motor must oppose stiction (pull-back) without consuming too much power3. Change to selected gear in less than 0.25 seconds


Project Testing: Cable Pulling Sys

1. Worm drive system must overcome 36.7 Ns of pull force from the derailleur and calculate maximum motor speed with full load▪ A 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 Meter

Requirements to be Tested:1. Must calculate torque2. Must use torque to calculate required gear ratio

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1. 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.



2. Must use torque to calculate required gear ratio• After 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 Risk

➢ Programmatic Risks:

➢ Budget: ➢ Power meter parts could be more costly than

expected

➢ Temperature may affect the strain reading

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Project Risk

➢ Implementation 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

0Consequence

ScheduleIncompletePremature

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

x



0Consequence

Performance

x

Risk of Performance

x

xExceeds

Expectations Nonfunctioning

1



0Consequence

x

x

Cost> $500< $150

x


7: Preliminary Schedule


8: Bill of Material (BOM)

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9: Review Action Items

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Thank you!

Website Link:

http://autoshiftsystem.weebly.com/

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EEL 4906.001 - Engineering Design1, Jamal Haque Ph.D. Performance AutoShift System (P.A.S.S.) 1.

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Transcript of EEL 4906.001 - Engineering Design1, Jamal Haque Ph.D. Performance AutoShift System (P.A.S.S.) 1.