Learning What Matters: Task Tailored Dynamics Models through Differentiable MPC
Jan Węgrzynowski, Piotr Kicki, Grzegorz Czechmanowski, Krzysztof, Tadeusz Walas
AI summary
Problem
Traditional dynamics models for MPC are trained with uniform loss functions like MSE, which misallocates limited model capacity by treating all state prediction errors as equally important for closed-loop control.
Approach
The authors use differentiable MPC to analytically compute how each predicted state error affects the final task cost, then use these sensitivities to dynamically weight the training loss so the model prioritizes learning critical states.
Key results
- Sensitivity-weighted loss reduces closed-loop tracking cost compared to uniform MSE and variance-based baselines
- Performance gains scale with multi-step rollout length, achieving a 91.7% normalized cost reduction at p=4
- Local, sample-dependent sensitivity weighting proves essential, as averaging sensitivities causes significant performance drops
- Demonstrated applicability to high-speed autonomous racing tasks with highly contextual state importance
Why it matters
It enables more efficient and accurate model-based control for robotics by ensuring limited model capacity is allocated to states that actually matter for task success.
Abstract
In model-based control, dynamics models are typ- ically trained by minimizing open-loop prediction errors uni- formly across all states. However, due to finite model capacity, this misallocates representational power, as not all prediction errors impact the downstream closed-loop performance equally. In this extended abstract, we propose a task-aware training methodology for a prediction model used in the context of Model Predictive Control (MPC). By extracting analytical sensitivities via differentiable MPC, we construct a loss function that weights multi-step dynamics model prediction errors based on their impact on the closed-loop task cost. Experimental results on a simulated 7DoF manipulator demonstrate that our sensitivity-weighted loss significantly improves closed-loop tracking performance compared to standard Mean Squared Error (MSE) or variance-based state standardization.