Brachiosaurus Model

A massive quadrupedal sauropod herbivore optimized for stable four-legged locomotion and food reaching.

Specifications

Property	Value
Height	2.0m torso, ~4m head reach (simulated)
Weight	205kg (simulated)
Joints	28
Actuators	30
Observation dim	83
Action dim	30

Features

• First quadrupedal species in the project
• Articulated 4-segment neck with head control (6 actuators)
• Front legs longer than rear (characteristic giraffe-like posture)
• Columnar elephant-like legs for stable support
• Food-reaching behavior using neck articulation
• 3-stage curriculum learning (balance, locomotion, food reach)

Unique Characteristics

Brachiosaurus differs from the bipedal species in the project:

• Quadrupedal gait instead of bipedal
• Herbivore behavior (food reaching) instead of predatory (hunting/striking)
• 22 actuators (6 neck + 16 legs)
• 75-dim observation space

Training Stages

1. Balance - Stand on all four legs without falling
2. Locomotion - Coordinated quadrupedal walking
3. Food Reach - Navigate to food and extend neck

Diagnostic Metrics (Stage 3)

After each training stage the eval command reports:

Metric	Description
mean_forward_velocity	Average forward speed (m/s)
gait_symmetry	Left/right stride symmetry ∈ [0, 1]
stride_frequency	Step frequency (Hz)
cost_of_transport	Energy efficiency (lower is better)
mean_pelvis_height	Torso height stability (m)
success_rate	Fraction of steps with food-reached event
min_prey_distance	Closest approach to food (m, head_food_distance)

Training Videos

Brachiosaurus PPO training progression across each curriculum stage.

STAGE 1

Balance

Standing on all four legs without falling

STAGE 2

Locomotion

Coordinated quadrupedal walking

STAGE 3

Food Reach

Navigating to food and extending neck

Usage

cd environments/brachiosaurus

# View the model
python scripts/view_model.py

# Train
python scripts/train_sb3.py train --stage 1 --timesteps 1000000