Hexapod

The Story

What is your project about?

This project is an 18-DOF (Degrees of Freedom) Hexapod Robot designed for high-stability traversal of complex environments. It features a custom-built real-time 3D terrain mapping system using a VL53L8CX Time-of-Flight (ToF) sensor. Unlike traditional hexapods that walk "blindly, " this robot perceives the elevation of the ground in an 8x8 matrix and visualizes it on a dedicated TFT display to assist in navigation and gait adaptation.

Why did you decide to make it?

Most affordable hexapods are limited to pre-recorded gait sequences that struggle with uneven terrain. I wanted to push the boundaries of DIY robotics by combining:

Advanced Kinematics: Managing 18 servos simultaneously to achieve fluid, organic movement.

Sensory Feedback: Moving beyond simple ultrasonic sensors to a true multi-zone depth map.

Human-Machine Interface (HMI): Creating a sophisticated 3D dashboard that allows a pilot to see exactly what the robot "sees" in terms of relief and obstacles.

How does it work?

1. The Physical Architecture (18-DOF)

The robot uses three servos per leg:

Coxa: Controls the horizontal swing.

Femur: Controls the lift.

Tibia: Controls the reach and contact point.

This setup allows the robot to maintain its center of gravity while shifting its body in any direction or rotating on the spot.

• Tibia: Controls the reach and contact point.This setup allows the robot to maintain its center of gravity while shifting its body in any direction or rotating on the spot.

2. The "Digital Eye" (VL53L8CX)

At the front of the robot sits the VL53L8CX ToF sensor. It scans the environment in an 8x8 grid (64 zones). Every few milliseconds, the sensor returns a set of 64 distance values.

3. Real-Time 3D Rendering & Logic

The heart of the visualization is a custom rendering engine on the ESP32 that transforms raw distances into a "Solid Relief" map:

The Perspective Engine: I implemented a projection where the map stretches toward the horizon. The further away a point is, the higher it sits on the screen's Y-axis, creating a natural sense of depth.

The "Solid" Visualization: To avoid a "floating" look, the code renders a "front skirt" (jupe). This closes the gap between the ground and the top of the obstacle, making obstacles look like solid 3D blocks.

Triple-Zone Color Logic: To make the data instantly readable, I developed a gradient system:

RED (Danger Zone): Obstacles under 30cm ($300mm$) are rendered in bright red at maximum height ($50$ pixels).

YELLOW (Caution): Objects between $30cm$ and $100cm$ transition through orange and yellow.

GREEN (Safe): Anything beyond $100cm$ ($1$ meter) is rendered as flat, green ground.

4. Advanced Gait Control

The "Advanced" gait control system uses these depth inputs to adjust the robot's stride. By knowing the height of the "dalles" (tiles) ahead, the controller can dynamically adjust the step height or body clearance.

5. Upcoming Upgrades: The "Heavy-Duty" Evolution

While the current version of the hexapod is fully functional, I am moving towards a "Pro" version to increase stability, payload capacity, and terrain navigation.

1. Brain Upgrade: From MPU6050 to BNO085

The current MPU6050 is great, but it requires the ESP32 to do all the heavy lifting for sensor fusion.

The Change: Switching to the BNO085 (9-axis IMU).

• The Change: Switching to the BNO085 (9-axis IMU).

The Benefit: The BNO085 has an onboard ARM Cortex-M0 processor that handles "Hillcrest Labs SH-2" algorithms. It provides rock-solid Quaternions and Euler angles without drift. This is crucial for keeping the 3D map on the TFT display stable while the robot is walking.

2. Power Upgrade: High-Torque Servos (20kg to 40kg)

The Tibia and Femur joints bear the most stress during the "support" phase of the gait.

The Change: Replacing all standard Tibia servos with high-torque versions (ranging from 20kg to 40kg).

The Benefit: Standard servos often struggle with the leverage effect of long legs. With 40kg servos, the robot can carry a heavier payload (like a larger battery or additional sensors) and maintain a "stiff" posture even when standing on only three legs (Tripod Gait).

3. Mechanical Redesign: Increased Height and Reach

To make the most of the new high-torque servos, I am redesigning the leg geometry.

The Change: Increasing the length (height) of both the Tibia and Femur segments.

The Benefit: * Greater Clearance: The robot will be able to step over much larger obstacles (dalles).

Enhanced Workspace: Longer legs allow for a wider "footprint, " significantly improving stability on slopes.

Visual Impact: A taller hexapod has a more aggressive, organic range of motion, making the "Advanced Gait Control" even more impressive to watch.

SebFr

@Advanced_Gait_Control

www.youtube.com/@Advanced_Gait_Control

Technical Specifications