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[Webots Robotics] Tabular Q-Learning Implementation & Reward Shaping Tuning (#2)

· 5 min read
Jihwan Park (jaybee)
AI & Robotics Engineer

Training Reward Curve

📌 Key Takeaways (TL;DR)

  • Problem: Sparse reward setups (+1.0 at goal, -1.0 at collision) cause severe exploration delays, causing the agent to wander or spin for thousands of episodes before stumbling upon the target.
  • Solution: Implemented a multi-objective Dense Reward Shaping mechanism combining potential-based Euclidean distance delta rewards (+0.1 × Δdist) with step (-0.01), turning (-0.01), and backward (-0.05) penalties, paired with exponential epsilon decay (1.0 → 0.05).
  • Result: The moving average reward shifted into a steady positive regime (0.7+) within 500 episodes in the no_obstacle scenario, achieving a 98%+ goal success rate.