Juncheng Qian
Bandersnatch
October 2019 - November 2019
Collaborator: Anastasia Dombrowski
A tri-wheel, wifi controlled RC car, Bandersnatch is an chanllegening yet rewarding project I worked on for my Mechatronics class at UPenn. The overall design of the car is inspired by a manta ray, with two front driving wheels to propel the car, and a servo-controlled wheel for steering. Through this project, I learned and exercise knowledge on mechanical design, circuit building, and wifi based communication on ESP32.
"It started as a manta ray design, but people kept calling it a batmobile."
Each front wheel is directly connected to a DC motor, which spins frontward and backward to drive the car. A servo is placed to the back left, and connected to the free spinning directional wheel with a L-bridge. By testing and tuning the servo movement, the servo is able to steer the wheel without collision with the chassis. In addition, we used high grip RC wheels for both the driving wheel and directional wheel to increase the friction and prevent drifting and slipping.
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In terms of overall design, we designed two wide, parallel stacked chassis to sandwich most of the critical components including the wheels between the chassis, in order to keep low center of mass, which increases stability.
We used the Adafruit DRV8833 motor driver to eliminate the need of setting up H-bridge and level shifter. 4 AA batteries (6V) are used to power the ESP32.
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There are two code files: one for the joystick controller and one for the RC car. The RC car code uses ISR interrupt and LEDC to manage the PWM. when the car receives the packet, a dataReceived flag is set to true and UDPreceive() reads the packet. Once the motor control is implemented, the flag is set to false until a new command is received again. The controller code is simpler: the ESP32 reads the x and y and z values of the joystick and sends out these signal to the RC car via UDPsend().
