P18392: Remote Control Bicycle Braking System
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Detailed Design

Table of Contents

Team Vision

Individual Accomplishments

Steven

Eli

Justin

Gabriel

Nick

Project Requirements

Engineering and Customer Requirements (Justin)

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Risk Assessment (Eli)

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Test Plans (Steven)

Bike

Hardware Selection (Eli)

Photodiode Used with the Alert Cluster

Photodiode Used with the Alert Cluster

A photodiode will be used in the alert cluster design. With the addition of the photodiode the ambient light can be detected and used to automatically adjust the brightness of the alert LED. This will ensure the LED will be visible in bright conditions but not excessively bright when the brake is used in lower light conditions.

Fuse Holder Used with the Bike Circuitry

Fuse Holder Used with the Bike Circuitry

Fuse Used with the Bike Circuitry

Fuse Used with the Bike Circuitry

There will be two fuses used in this design, a 12 amp and 1 amp fuse. The 12 amp fuse will be placed inline to protect the actuator and the 1 amp fuse will be placed inline to protect the microcontroller and other small electronics.

Final Selected Motor Controller

Final Selected Motor Controller

Updated Current Draws (Nick)

Updated bike current calculations

Updated bike current calculations

The max heavy usage for the bike calculations made a few assumptions. For the actuator it was assumed that there would be a total of 15 braking events per hour, or one every four minutes. Each braking event was assumed to average out to be 5 seconds long with the actuator acting under full load and drawing its full 3.5A.

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Bike Voltage Regulation (Nick)

LM256T-3.3VNS/NOPB

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NOTE: The 5V output does not reflect the 3.3V output of the chosen specific model.

The battery provides 12V which is far too high to power the Teensy LC (3.3V) and any lesser peripherals. The TI LM256T is a switching regulator that can handle a voltage input within 7-40V and provides a current of approximastely 3A within that range. With the Teensy LC drawing a maximum of 125mA with the Xbee drawing at most 40mA, making the current well within specs for the 3.3V rail.

A switching regulator was chosen to mitigate heat generation and to allow for higher efficiency. As voltage drop increases, linear regulator performance begins to fall off and heat generation increases. Switching regulators use PWM instead as a solution to this, making them a better candidate for a drop from 12V to 3.3V. The TI LM series is a popular product line for this specific type of application of dropping relatively large voltages to voltages usable by microcontrollers.

Bike Battery Charging (Nick)

SEM-1562A-CA 1.5A Maintainer

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This was chosen for ease of implementation as Sealed Lead-Acid battery charging and care requires fairly complex circuitry and monitoring to be robust. This charger handles desulphation for batteries that have been left discharged over a long period. It also handles the logic for dealing with the different stages of charging, along with a trickle-charge mode for the final stage.

Charging Solution (Nick)

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Currently the charging solution is to open the electronics enclosure to disconnect the battery from its load and connect it to the charger at the terminals. As the battery is designed to be removeable, this design allows for portability and also circumvents the weatherproofing issues that come along with machining out holes and inserting bulkheads for a custom charging port.

Circuit Schematic (Eli)

Circuit Schematic for the Bike Electronics

Circuit Schematic for the Bike Electronics

Wiring (Nick)

Deutsch Connectors

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Originally typical hobbyist E-bikes solutions were considered. However these connectors offer questionable moisture resistance and may not be as reliable over longer lifespans. The XT60/90 connectors was a suggestion but these don't offer water resistance and doesn't seem to have reliable pinning force for securing in the cables for long term usage. DT connectors are typically used in automotive applications including ebikes, boats, motorcycles and other vehicles. They offer robust IP68 weather resistance and are designed to be rugged over a long timespan. Various vendors also sell convenient connection kits, and we are currently interfacing with the Simone Center to see what would be ok for purchasing.

The specific crimping tool required has also been considered. Worst case scenario one can be bought for around $50, which will be an unlikely case. However, there are still plenty of avenues through RIT and outside to explore to obtain a usable crimping tool to avoid having to buy one.

Cabling (Nick)

Wire gauge was also considered. 16AWG is more than sufficiently thick to avoid any voltage drops across the line while also not being frail. The largest distance of wiring will be from the front of the bike to the electronics enclosure, with a very minimal amount of current. The voltage drop is calculated using Ohm's law and by treating the wire itself as a resistor.

Length is proportional to resistance while thickness (cross-sectional area) is inversely proportional, meaning thicker wires have less resistance over a static distance.

Assuming a very rough maximum distance of 4 feet, 16 AWG copper cable has approximately 0.0016 Ohms of resistance, which is negligible and results in a voltage drop less than half of a percent.

The main concern with the cabling is the long-term physical survivability, mounting and overall aesthetic.

The current chosen DT pins work in the 12-16 AWG range. This is subject to change as designs are finalized and the overall "shape" of the system is physically considered.

Overall Wiring (Nick/Eli)

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There will be one 3-pin DT connector pair going to the alert cluster somewhere on the handelbars of the bike. This will provide power/signals to both the LED and its photodiode sensor used for light attenuation. One 2-pin DT connector pair will be attached to the read switch being used to monitor bike speed at the front wheel. The read switch and the alert cluster will meet at the body and share the same ground connector, leaving 4 wires to travel from the front of the frame to the electronics enclosure on the back, which will be connected to the electronics enclosure via a DT connector.

The actuator alone requires at least 6 wires going to the motor driver housed in the electronics enclosure. The cabling to the actuator to the electronics enclosure will be connected via an 8-pin DT connector pair, allowing us to populate the pins as needed.

Internal wiring will be handled by ribbon cables, which as of yet have not been specifically chosen or obtained.

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All external wires will be housed in a techflex mesh cabling sheathe and attached to the bike frame alongside the brake cables where possible.

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The size of the overall cabling will be considered when sizing out the overall sheating. A vendor has already been picked out for all components and are placed in the BOM.

Weatherproofing Connectors

The connectors themselves are IP68 rated and exceed the specifications for weatherproofing. However, it is also important to consider the weatherproofing involve with creating connectors to the electronics enclosure themselves. The shape of the connectors allow for treatment as a bulkhead, and lining the area where the connector and the enclosure meet with some sort of waterproof epoxy or resin will be sufficient to maintain the IP rating of both the enclosure and the connector.

Stress Analysis (Steven)

To ensure the proposed design would not fail or damage the tricycle, a strength and fatigue analysis was performed. Using a combination of hand calculations and simulation it was determined that the "Safe Stop" system should last the lifetime of the tricycle. ANSYS was primarily used to model the more complex assembly interactions between the various mounting components. These simulations helped to determine the maximum equivalent stress seen in each component. These values were used in subsequent hand calcualtions to determine the number of cycles needed to fatigue the components. For all Al 6061 components, fatigue data was taken from the following figure.
6061 S-N Curve

6061 S-N Curve

Base Plate

Mechanical Set Up

Mechanical Set Up

Equivalent Stress

Equivalent Stress

Total Deformation

Total Deformation

Base Plate Fatigue Calculations

Base Plate Fatigue Calculations

Cable Housing Mount

Mechanical Set Up

Mechanical Set Up

Equivalent Stress

Equivalent Stress

Cable Housing Mount Fatigue Calculations

Cable Housing Mount Fatigue Calculations

Clevis

Mechanical Set Up

Mechanical Set Up

Equivalent Stress

Equivalent Stress

Clevis Fatigue Calculations

Clevis Fatigue Calculations

Rear Frame

Mechanical Set Up

Mechanical Set Up

Equivalent Stress

Equivalent Stress

Actuator Mount

Mechanical Set Up

Mechanical Set Up

Equivalent Stress

Equivalent Stress

Rear Mount Fatigue Calculations

Rear Mount Fatigue Calculations

Caliper Attachment

Mechanical Set Up

Mechanical Set Up

Equivalent Stress

Equivalent Stress

Bike & Enclosure CAD

Renderings (Steven/Justin)

Full Assembly Rendering

Full Assembly Rendering

Bike Electronics Enclosure Rendering

Bike Electronics Enclosure Rendering

Actuator Assembly Rendering

Actuator Assembly Rendering

Caliper Attachment

Caliper Attachment

Drawings (Steven)

Full Assembly #1

Full Assembly #1

Full Assembly #2

Full Assembly #2

Actuator Mounting Assembly #1

Actuator Mounting Assembly #1

Actuator Mounting Assembly #2

Actuator Mounting Assembly #2

Actuator Mounting Plate

Actuator Mounting Plate

Actuator Mounting Assembly #2

Actuator Mounting Assembly #2

Actuator Mounting Assembly #2

Actuator Mounting Assembly #2

Actuator Rear Mount

Actuator Rear Mount

Actuator Support

Actuator Support

Threaded Frame Clamp

Threaded Frame Clamp

Through Hole Frame Clamp

Through Hole Frame Clamp

Brake Cable Mount

Brake Cable Mount

Clamp Spacer

Clamp Spacer

Cable Clevis

Cable Clevis

Battery Clamp

Battery Clamp

Bike Electronics Mount

Bike Electronics Mount

Bike Electronics Mount Standoff

Bike Electronics Mount Standoff

Caliper Attachment

Caliper Attachment

Remote

Range Testing (Gabe)

Line of Sight 60ft

Line of Sight 60ft

Line of Sight 510ft

Line of Sight 510ft

Line of Sight 730ft

Line of Sight 730ft

Line of Sight 1010ft

Line of Sight 1010ft

Obstruction 640ft

Obstruction 640ft

View of Obstruction Test

View of Obstruction Test

Green: Fixed Location, Red: Furthest LOS Test, Blue: Furthest Obstacle Test

Green: Fixed Location, Red: Furthest LOS Test, Blue: Furthest Obstacle Test

Antenna Selection (Gabe/Eli)

View of Short Antenna

View of Short Antenna

View of Long Antenna

View of Long Antenna

View of Dome Style Antenna

View of Dome Style Antenna

View of Disk Style Antenna

View of Disk Style Antenna

Atenna Benchmark

Atenna Benchmark

When looking into the antennas that will be used in this project the limiting factor is the antenna that will be on the remote. On the bike a large antenna is acceptable and can be placed out of the way. On the remote it would be cumbersome if the antenna was too large. Above are a few of the antenna designs examined for use. The short cylinder has been selected for testing due to its small size, low price, and good gain. The antenna that has a half dome on the end of the wire will not work because there is not enough room on the inside of the remote for the wire. The same problem arises with the disk shaped antenna. The long style antenna displayed has the same benefits as the first but is much longer, therefore it will be used for testing and a benchmark for the design.

Remote Hardware Selections (Gabe/Justin)

Remote Battery Holder

Remote Battery Holder

Remote Buzzer

Remote Buzzer

Remote Display Screen

Remote Display Screen

Remote Slider

Remote Slider

Push Button 1

Push Button 1

Push Button 2

Push Button 2

Push Button 3

Push Button 3

A final push button has not yet been selected. The three push buttons shown have been purchased for testing and a final selection will be made.

Remote Mounting

Remote Mounting

Remote Mount

Remote Mount

The proposed mounting solution for the remote to the guardians bike is a general cell phone mount for bicycles.

Updated Remote Current Draw Calculations (Nick)

Updated remote current calculations

Updated remote current calculations

Remote Voltage Regulation (Nick)

Constraints

TC1264-3.3VDB

595-UUC285T-3 was originally considered. It provides 1A at ~0.3V dropout, increasing linearly as dropout increases.

However, dimensions were to large, (9x9x10mm). With topology and pins included, topology rivals Teensy LC in size.

The TC1264-3.3VDB is the chosen alternative with dimensions (6.5x3.5x1.5mm). The specs meet the constraints.

public/Final Design Documents/Regulator/TC1264_IV.PNG

450mA a minimum projected dropout of 0.3V. Peak dropout draws up to approximately 800mA at the max projected dropout of 1.1V. This is more than enough for the projected max current draw of 300mA from the remote, not including LEDs.

It is a surface mounted chip.

Remote Battery Charging (Nick)

MCP7833T-FCI

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Previously a BQ25600 charging IC was chosen. However, once mounting was considered it was scrapped due to its BGA mounting interface with 0.5mm pitch. A replacement, the MCP7833T-FCI (surface mount) IC chip was chosen in its place. This is a popular chip among hobbyists and prefabricated Lithium-Ion charging circuits. It uses two status logic pins to display/relay charging stages. It also includes thermal regulation to consider battery charge performance under different temperature conditions and is designed for Lithium-Ion/Polymer batteries.

The remote will be charged via USB.

Remote Circuit Schematics and Layout (Gabe)

Circuit Schematic for the Remote Electronics

Circuit Schematic for the Remote Electronics

Circuit Layout for Remote Electronics, Front

Circuit Layout for Remote Electronics, Front

Circuit Layout for Remote Electronics, Back

Circuit Layout for Remote Electronics, Back

Remote CAD

Renderings (Steven/Justin)

Remote Rendering

Remote Rendering

Remote Internal Layout

Remote Internal Layout

Drawings (Steven)

Remote Face

Remote Face

Remote Face

Remote Face

Remote Face

Remote Face

Remote Body #1

Remote Body #1

Remote Body #2

Remote Body #2

PCB Standoff

PCB Standoff

Drop Testing

The main concern relating to remote durability is surviving a potential drop (ER34). A drop from waist height could damage either the screen or other sensitive electronics. To lessen the impact from a drop, soft material is proposed to line the outside of the remote. Initially two materials will be tested for their protection potential. Thermoform plastic will allow an ergonomic shape to me molded to the remote case.
Low-Temp Thermoformed Plastic

Low-Temp Thermoformed Plastic

Liquid rubber can conform to the outside of the remote and provide a tactile surface for the user.
Liquid Rubber

Liquid Rubber

Design and Flowcharts (Gabe)

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public/Detailed Design Documents/Software/parse_loop.png

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public/Detailed Design Documents/Software/actuator_loop.png

public/Detailed Design Documents/Software/actuator_loop.png

Bill of Material (BOM) (Team)

Detailed BOM

Detailed BOM

Budget

Budget

Plans for next phase

Phase 1 Detailed Plan

Phase 1 Detailed Plan

Overall MSD2 Plan

Overall MSD2 Plan

Steven

Nick

Justin

Eli

Gabriel


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