System Integration

Individual assignment: Design and document the system integration for your final project

This assignment covers System Architecture that outlines all major subsystems and how they interact in an electric bike

System Overview

The E-Bike project integrates power electronics, mechanical systems, embedded control, and user interfacing to build a functional electric bicycle. The architecture consists of key systems: Power Supply, Motor Drive, Motor Control, User Interface, Safety Monitoring, and Mechanical Mounting.

1. Power Supply System

• Battery Pack (24V Li-ion): Provides the primary power source. Composed of multiple 3.7V cells connected in series and parallel to reach the desired voltage and current capacity. Protected by BMS (Battery Management System).

• Battery Pack Holder: Custom-designed bracket that securely attaches the battery to the bicycle frame, preventing movement during rides.

• Battery Cells Holder: Plastic grid layout for organizing the cylindrical cells, ensuring easy wiring and structural integrity.

2. Motor Drive

• Hub Motor: A DC hub motor embedded into the rear wheel. It provides direct drive without transmission systems, enabling efficient power transfer and reduced maintenance.

3. Monitoring and Safety System

• Temperature Sensors: Installed on motor, controller, and battery to prevent overheating. Automatically shuts off or limits power if temperature exceeds safety thresholds.
• Voltage Sensors: Continuously measure battery voltage to prevent deep discharge and ensure optimal performance.

4. User Input and Interface

• Throttle: Analog 0–5V signal or Hall-effect sensor. User controls acceleration by twisting the handlebar throttle.
• Brake Switch: Integrated with brake levers to instantly cut power to the motor for safety during braking.
• LCD Display: Real-time display of speed, battery level, temperature, and power status. Also includes odometer functionality.

• Control Buttons: Power on/off, display modes, assist level adjustment.

5. Motor Control System

• Motor Controller: Custom PCB for DC motor control. Receives throttle and brake inputs and drives the motor accordingly.

• Inputs: Throttle signal, brake switch, temperature and voltage data.
• Outputs: High-current PWM signals for motor drive, safety interrupt signals.
• DC-DC Converter: Steps down the 24V battery voltage to 5V for microcontroller and display operation.
• Features: Soft start to avoid jerks, smooth braking, current limiting to protect motor and battery.

6. Support Electronics

• Motor Driver PCB: Combines a microcontroller (e.g. Seeed Xiao RP2040) and IRFZ44 driver circuitry. Interfaces with sensors and display modules.

7. Mechanical Components

• Battery Enclosure: Waterproof case to house the battery pack. Mounted on the down tube.
• Motor Mount: Reinforced dropouts and torque arms to hold the motor securely.
• Controller Mount: 3D-printed mounted to the frame. Ensures airflow and easy access.
• Wiring Management: Sleeving, zip ties, and routing channels to keep wires organized and safe from wear.
• Torque Arms: Prevent motor axle from rotating under torque. Essential for high-power hub motors.

8. Additional Hardware

• Fasteners: Anti-vibration stainless steel bolts for mounting all components securely.
• Waterproofing: Rubber gaskets, silicone sealant, and conformal coating to protect electronics from moisture.

Code and Interface Files

The following files are included as part of the project:

• HTML File – A web-based interface for interacting with the Arduino via serial.
• Arduino Code File – Contains the full sketch used in this implementation.