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ScooterizersDetailed Design Review “Making last-mile transportation safer, easier, and more efficient”
Project Goals • The goals of this project are twofold: • Produce a prototype scooter that is lightweight and foldable, easy to use, and provides an electronic boost for uphill travel. • Provide future design teams with a database of knowledge, so that they can benefit from our project learning and experience.
Project Deliverables from First Semester Model the Electrical System Improve Voltage Regulation / Protection Circuits. Add Parallel-Series Ultra-Capacitor Switching Circuit. Combine the Fragmented Control System. Add Variable Throttle / Regenerative Brake Control. Add a Clutch to the current Motor System
Model the Electrical System • Why: • To make the project well documented. • To make it easy to test, assemble and validate. • What do we mean? • Any diagram, circuit, chart or graph has to be: • Clear. • Well explained. • Tested.
Variable Throttle and Brake (Jet- Tread’s Choice) Thumb throttle • Options • Push Button • Linear Motion Potentiometer • Rotational Motion Potentiometer Colin
Variable Throttle and Brake • (Scooterizers’ Choice) Twist throttle • Specifications • Item Code: Throttle-ES (Hole Effect Type) • Price: $ 24.99 + tax • Supply Voltage: 12v • Return Voltage: 4v • Handle Bar Diameter: (approx) 22mm / 7/8" • Three wires red, green, black • The supply voltage = red and black wires. • Green wire voltage increases as the throttle is turned. • Fits 24 and 48v scooters.
Clutch for the Motor Reell Precision Manufacturing Miniature Electromechanical Clutch Model: EC30XP Cost: $77.82 Accelerate loads from zero to full speed in less than three milliseconds. Apply electricity and these clutches rapidly engage; turn off the power, and they instantly disengage. Due to the rapid acceleration and nonslip design of these clutches, some applications may need a slip clutch, coupling, or other shock-absorbing device. These clutches drive in one direction only. Max. rpm is 1400. They operate on 24 VDC and include wire leads for hardwiring
Application Considerations Design Characteristics Colin
Control and Electrical Introduction • Lacked good voltage regulation • Lacked current limiting • No master control system RESULT: Reliability and usability issues
Simplify Series-Parallel Switch Jet-Tread Series-Parallel Switch PROBLEM: Hard to use
Simplify Series-Parallel Switch • USAGE SCENARIOS • Regenerative Mode: • 2.7Vdc • Drive Mode: • 24.3Vdc (9*2.7Vdc)
Simplify Series-Parallel Switch Design No. 1: SPDT Relay Design No. 1: SPST Relay
Simplify Series-Parallel Switch • Design Choice: Design No. 1 (SPDT Relays) • Cheapest • Most Reliable • Fewest Points of Failure
Circuit Protection Mechanisms • Electrical Isolation • Voltage Regulation • Current Limitation
Circuit Protection Mechanisms Electrical Isolation KISS: SPDT Relays!
Circuit Protection Mechanisms Voltage Regulation • Regenerative Mode • 0-15Vdc Input • 2.7Vdc Output • Drive Mode • 12-24Vdc Input • 12Vdc Output
Circuit Protection Mechanisms Voltage Regulation Drive Mode Custom Design: Best idea, but lacking time/expertise Commercial Solution: EXPENSIVE Inverter-Power Supply Combo: Best fit for this project
Circuit Protection Mechanisms Voltage Regulation + Inverter-Power Supply Combo: Best fit for this project
Circuit Protection Mechanisms Voltage Regulation Regenerative Mode
Circuit Protection Mechanisms Current Limitation Current Limiter: MOSFET + Microcontroller Solution
Combine the Control System Modularity = Future Usability SOLUTION: Have several minor control systems under the direction of master control system • Utilize ATMega48 Chips • Very cheap ($2) • 21 I/O Points • PWM • ADCs • Expandable
Project Risks and Scope Future-Proof Designs: (Place Most Effort) Modular Control System Durable Series-Parallel Switch Design Throttle/Brake/Clutch Controls System Modeling Need Future Design Work: Drive-mode Power Supply Regenerative-mode Power Supply (possibly) Motor (hub?) Frame Risk: Variable Regenerative Brake The regenerative break itself will be implemented. However, we may not have time to make it variable. This will be done given enough time.
Project Schedule Detailed Design Review [October 8] Order Parts [Early October] Individual Fabrication [Mid/Late October] Individual Assembly Final Assembly [Early/Mid November] Client Review [November 19] Documentation [November/December] Knowledge Database