BATTERY AND MOTOR

BATTERY AND MOTOR

 

A critical part of the Biometric Autonomous Droid (BAD-2024) wheelchair system is the motor and battery, which power all functions of the wheelchair. Key specifications include:

  • Battery: The wheelchair is powered by a 24V battery with a capacity of around 50Ah, providing at least 8 hours of continuous use. The battery can be a single 24V unit or two 12V units and is designed to fully charge within 5 hours.
  • Motor: Two motors drive the left and right wheels independently. The motors are rated for 24V and 150-300 Watts, with a peak torque of 100-150 Nm and a continuous torque of 8-15 Nm. This allows the wheelchair to move at speeds of up to 4mph and handle a total weight of 400 lbs.

These components ensure reliable and powerful performance, providing autonomy for the wheelchair throughout the day.

The motor requires the phase and hall sensors to be connected to safely operate and for controllers to function effectively (see figure above). The brakes will be connected to power and ground to release the brakes, allowing the motor to turn. When not connected to power, the brake lock prevents the motor from moving, serving as an emergency brake or parking brake for the wheelchair.

To calculate and control the speed of the wheelchair, the controller reads the Hall sensors from the motor, which are signals U, V, and W. The remaining signals will be left floating to minimize signal noise. Additionally, some of the controller inputs will originate from the microcontroller, which will control brake direction, speed, and motor activation.

The wiring diagram includes the two DACs and Pico that are responsible for controlling the motor operation by sending signals to the controller, including direction, speed enable, and brakes. The controller requires an analog signal to determine the motor’s operating speed, but the Pico only sends out a PWM signal. To convert the digital PWM signal to an analog signal, the GPIO pins are connected to a DAC.

Additionally, an amplifier is included to boost the voltage from the Pico from 3.3 volts to 9.9 volts, aligning with the controller’s input range of 0–10 volts. The remaining signals required by the controller are digital and can be directly connected to the controller from the Pico without conversion. Lastly, the Pico receives signals from the Jetson Nano, which dictate the motor operations.