Cart Driver

Browser-based WASD controller for a two-motor RobStride cart:

• Motor 1: steering, with startup position captured as straight
• Motor 2: rear-wheel velocity control
• Official RobStride CH340/GD32 USB-CAN adapter on /dev/ttyUSB0
• Steering uses a 2:1 motor-to-vehicle ratio: 2° motor rotation equals 1° steering.

Safety behavior

• Motors must be explicitly connected and armed.
• W/S is dead-man drive control; releasing the key/button commands zero speed.
• A/D slews vehicle steering at up to 100°/s within ±60°.
• Manual steering accelerates at 400°/s² and decelerates at 250°/s².
• Set center here records the current motor-1 position as vehicle-straight.
• Steering response is governed by speed, acceleration, and the ±60° range.
• Center steering returns separately at up to 30°/s with a gentle acceleration.
• Idle steering drops to Kp=3/Kd=0.2 and releases corrective torque inside a 0.75° deadband.
• Idle drive uses Kp=0/Kd=0 after its speed command reaches zero.
• A 350 ms browser-command watchdog stops drive and steering slew.
• STOP/disarm and server shutdown command zero drive speed and disable both motors.
• Drive uses damped MIT velocity control with a 1,000°/s² command ramp.
• Drive torque is limited to 2 Nm and speed to 500°/s.
• The drive-speed slider defaults to 250°/s.

Install and run

cd ~/repos/cart_driver
python3 -m venv .venv
.venv/bin/pip install -r requirements.txt
.venv/bin/python app.py

Open http://<raspberry-pi-ip>:5000/.

Set a different adapter path if needed:

ROBSTRIDE_PORT=/dev/ttyUSB1 .venv/bin/python app.py

Keep the cart lifted or otherwise restrained during initial testing.

Run as a service

sudo install -m 0644 cart-driver.service /etc/systemd/system/cart-driver.service
sudo systemctl daemon-reload
sudo systemctl enable --now cart-driver.service

Inspect logs with:

journalctl -u cart-driver.service -f