Senior Design Robot

An autonomous differential-drive robot that uses a YDLidar G2 for SLAM-based navigation. The ESP32 handles hardware (LiDAR, motors, encoders) and communicates over MQTT. A Python Flask server on the host machine runs RMHC-SLAM, plans paths, and sends movement commands back to the robot.

System Overview

ESP32 (Robot)                       Server (Host PC)
─────────────────────               ─────────────────────────────────
LiDAR scan (360 bins)  --MQTT->   SlamService  >  RMHC-SLAM map
Encoder ticks          --MQTT->   MotionExecutor > A* path planning
                                   MotorCommander > PD heading control
Twist command (v, w)   <-MQTT--    > publish twist

ESP32 Firmware

Dependencies

The firmware depends on a custom YDLidar G2 Arduino library. Arduino has no standard dependency file, so install it manually:

Open Arduino IDE -> Sketch -> Include Library -> Add .ZIP Library…
Download and install from: sarahGruber6/YDLidarG2_ESP32
Open Robot/ESP32/full_integration_v1/full_integration_v1.ino

Before flashing, create Robot/ESP32/full_integration_v1/config_local.h with your WiFi and MQTT credentials (see Config Variables below).

Backend Server

Requirements

Python 3.14
The BreezySLAM C extension (included in this repo under BreezySLAM/)

Setup

# From the repo root:
cd Server
python -m venv .venv
source .venv/bin/activate      # Windows: .venv\Scripts\activate
pip install -r requirements.txt
cd ..
pip install BreezySLAM/python  # builds the C extension

Run

# From the repo root, with the venv active:
python -m Server.app

The web UI is served at http://localhost:5000.

Config Variables

There are two config layers: one on the server (Python), and one on the ESP32 (C++). Both use a _defaults file checked into git and a _local file you create locally for secrets and machine-specific overrides.

Server — `Server/config_defaults.py` (and `Server/config_local.py`)

Variable	Default	When to change
`MQTT_HOST`	`""`	Set in `config_local.py` to your broker address
`MQTT_PORT`	`1883`	Change if your broker uses a non-standard port
`ROBOT_ID`	`"r1"`	Change if running multiple robots; all MQTT topics use this prefix
`WHEEL_DIAMETER_MM`	`96.0`	Update if you swap drive wheels
`AXLE_WIDTH_MM`	`480.0`	Update if the wheelbase changes
`TICKS_PER_REV`	`760.0`	Update after encoder calibration if counts per revolution differ
`ENCODER_LEFT_SIGN` / `ENCODER_RIGHT_SIGN`	`1`	Flip to `-1` if an encoder counts backwards
`ODOM_THETA_SIGN`	`1`	Flip if odometry rotation direction is inverted
`ROBOT_RADIUS_MM`	`350`	Used for obstacle avoidance clearance; update to match physical robot size
`MAP_SIZE_PIXELS` / `MAP_SIZE_METERS`	`800` / `20`	Increase for larger environments; larger maps use more RAM
`sigma_xy_mm` / `sigma_theta_degrees`	`200` / `30`	SLAM position/heading uncertainty. Increase if SLAM drifts; decrease for tighter but less robust matching

ESP32 — `Robot/ESP32/full_integration_v1/config.h` (and `config_local.h`)

Variable	Default	When to change
`WIFI_SSID` / `WIFI_PASS`	—	Set in `config_local.h` for your network
`MQTT_HOST` / `MQTT_PORT`	—	Set in `config_local.h` to match the server
`LEFT_PWM`, `RIGHT_PWM`	7, 5	Change if motor driver PWM wiring changes
`LEFT_DIR`, `RIGHT_DIR`	8, 6	Change if motor driver direction wiring changes
Left encoder `A` / `B`	38, 39	Change if encoder wiring changes
Right encoder `A` / `B`	40, 41	Change if encoder wiring changes
`LIDAR_RX` / `LIDAR_TX` / `LIDAR_MOTOR`	17, 18, 16	Change if LiDAR wiring changes
`LEFT_TRIM`	`1.0`	Scale factor to compensate if one motor runs faster; tune via `drive_calibration.ino`
`POST_EXCLUSION_ZONES`	`{{45,5},{150,6},{238,5},{344,5}}`	LiDAR bins blocked by the robot chassis. Recalibrate with `lidar_calibration.ino` if the LiDAR is remounted
`OBSTACLE_STOP_MM`	`350`	Distance at which the robot brakes for an obstacle
`OBSTACLE_FORWARD_BIN`	`350`	Which LiDAR bin is “straight ahead” — update if the LiDAR is remounted at a different angle
`OBSTACLE_FORWARD_V_SIGN`	`-1`	Flip if forward motion maps to negative velocity