Overview: Electrical Systems

Summary

The Arduino DUE is the 'brain' of the bike that receives inputs and, based on those inputs, the DUE sends outputs to other electrical systems. The DUE is attached to the PCB and through the PCB the DUE communicates with a total of four other electrical systems: Front motor, rear motor, front encoder, and IMU. On the old bike, all electrical systems use the same external power supply (24V lithium battery pack).

Actuators

The front and rear motor are simple actuators, meaning that the front and rear motor does not communicate back to the DUE. On the old bike, the front motor and rear motor operate on a 24V power supply. On the new bike, the front motor is being reduced to a 12V DC motor to minimize stress on the front infrastructure (specifically the infrastructure that holds the front motor) caused by the excessive torque produced. The new rear motor will continue to operate on 24V power supply but requires approximately 10 A (specifically 250 W) for proper operation. Both motors have a motor controller. The front motor has a standard motor controller that safely amplifies the controlling signal (sent by the DUE) to operation voltage levels of the front motor and regulates that signal. The rear motor has a motor controller that not only amplifies the commands sent by the DUE as needed but includes a diversity of functionalities (e.g. brake, headlights, reverse, etc.). These functionalities are currently not being used. These actuators operate using PWM (pulse-width-modulation) signals. Also the amplitude of the motor voltage remains constant so the motor is always at full strength. The result is that the motor can be rotated much more slowly without it stalling. To control the speed of the motor is through changing the duty cycle of the PWM signal.

Encoder

There is currently one encoder coupled to the front motor on the old bike. The purpose of the encoder to the measure the rotation of the front wheel. This data is sent to the DUE such that the DUE can tell how much to turn the front motor based on its relative position. The current encoder operates using three channels, where two channels indicates the amount of rotation and direction of rotation. The third channel indicates number of full revolutions. Please visit 'Fundamental Concepts' page to learn more in detail about the encoder.

IMU

The current IMU (Inertial Measurement Unit) is a Yost Labs 3-Space Sensor Embedded. It is an ultra-miniature, high-precision, high-reliability, low-cost SMT Attitude and Heading Reference System (AHRS) / Inertial Measurement Unit (IMU) which uses triaxial gyroscope, accelerometer, and compass sensors in conjunction with advanced processing and on-board quaternion-based orientation filtering algorithms to determine orientation relative to an absolute reference in real-time. For more information on the operation of the IMU, please visit the 'Fundamental Concepts' page.