Rover Following Logic & Control Architecture

This page explains how the rover follows the drone using localization data from the VOXL (drone).
It covers:

• The control logic
• Reset synchronization handling
• Safety & smoothing features
• System behavior diagrams

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Overview

The rover receives VIO (Visual‑Inertial Odometry) data streamed over Wi‑Fi from the drone.
The laptop acts as the brain and sends %JSON motor commands to the rover.

Pipeline

Drone (VOXL QVIO) → UDP Position Packets → Laptop → JSON Drive Commands → Rover Motors

The laptop continuously:

1. Reads drone X,Y,Quality
2. Computes rover movement toward drone
3. Sends JSON motor commands to rover
4. Handles resets and low‑quality state

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Rover Following Controller

Control Equations

dx = drone_x - rover_x
dy = drone_y - rover_y

T  = clamp(Kt * dy)         # forward motion
W  = clamp(Kr * dx)         # turn rate

L = clamp(T - W)            # left wheel
R = clamp(T + W)            # right wheel

Parameter	Meaning
Kt	Forward gain
Kr	Turning gain
STOP_DIST	Distance threshold before stopping

This creates a smooth proportional controller.

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Reset Synchronization Logic

The VOXL odometry resets to (0,0) when tracking quality collapses.

Goal

If drone resets:

• Rover should move to the last true drone location
• Only then reset its own coordinate frame to (0,0)
• Prevent jumps / teleport behavior

Logic

Event	Rover Action
Tracking OK	Follow normally
Drone reset triggered	Finish going to last known good pos
Rover reaches that pos	Reset to (0,0) together

Rover turns yellow in GUI during reset‑sync.

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Low‑Quality Filter

Poor vision → noisy / fake coordinates.

Quality	Behavior
Good (>= 40%)	Accept & follow
Low (< 40%)	Ignore updates, keep smooth trajectory
0%	Likely blackout → treat as candidate reset

Drone dot turns gray when low‑quality.

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Two Operating Modes

Mode	Behavior
Live Follow	Rover constantly tracks drone
Summon Mode ("Come to Me")	Drone sends a command, rover travels to drone only once

User triggers summon by pressing Enter on drone SSH session.

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Testing Workflow

Step	Action
1	Start QVIO + UDP on drone
2	Start rover sim on laptop
3	Move drone → rover follows
4	Cover cameras → simulate reset
5	Confirm graceful recovery

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Related Files

File	Description
read_vio_send_udp.py	Drone VIO streaming + summon trigger
rover_follow_sim.py	Laptop controller + UI viz

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Result

This module delivers:

• Real robotic following behavior
• Smooth motion, no jumps
• True multi‑robot frame sync logic
• Reset recovery system
• Field‑tested reliability