This paper introduces a method for Model Predictive Path Integral (MPPI) control that optimizes sample generation towards an optimal trajectory through Stein Variational Gradient Descent (SVGD). MPPI relies upon predictive rollout of trajectories sampled from a distribution of possible actions. Traditionally, these action distributions are assumed to be unimodal and represented as Gaussian. This assumption can lead to suboptimal rollout predictions due to sample deprivation and, in the case of differentiable simulation, sensitivity to noise in the cost gradients. By introducing SVGD updates in between MPPI environment steps, we present Stein-Optimized Predictive Path-Integral Inference (SOPPI), an MPPI/SVGD algorithm that can dynamically update noise distributions during rollouts to better capture action sampling distributions without an excessive increase in computational requirements. We demonstrate the efficacy of SOPPI through experiments on a planar cart-pole, 7-DOF robot arm, a planar bipedal walker, and a Unitree G1 29-DOF Robot. Results indicate improved inference of an underlying multi-modal action distribution compared to other Stein-based MPPI algorithms, with improved system performance and similar or improved efficiency across a range of hyper-parameters.

翻译：暂无翻译