用低成本模拟纠正偏差,高效获得高精度参数推断结果。
Bridged SBI: Correcting Biased Low-Fidelity Posteriors for Cost-Efficient High-Fidelity Inference

- 先用低精度模拟定位关键参数区域,再通过残差修正映射到高精度空间。
- 在有限高精度模拟次数下,后验分布准确性提升超过30%。
- 适合资源受限但需高精度参数估计的机器人土方仿真场景。
粒子模拟器的精准标定对机器人土方作业仿真至关重要,但因高度非线性粒子动力学和传统模拟器的黑箱特性,解析标定极为困难。虽然基于模拟的推断(SBI)可仅通过正向模拟估计参数后验分布,但直接应用于高保真(HF)粒子模拟器通常计算成本过高。低保真(LF)模拟器通过粗粒度粒子可降低开销,但粒径与粒子数量的变化会改变重现相同观测所需参数值,导致LF后验存在偏差。本文提出Bridged SBI,利用虽有偏差但信息丰富的LF后验引导HF推断。该方法首先通过廉价的LF模拟识别粗粒度高密度参数区域,随后学习局部残差桥接函数,以校正LF-HF差异,将样本迁移到符合HF一致性的区域。我们分析了序列多保真SBI(Naive-MF)在缺乏差异校正时易受LF后验误导而导致后验覆盖不足的问题。实验表明,在模拟到模拟的粒子参数标定及真实到模拟的土壤观测标定任务中,相较于仅使用HF或Naive-MF基线,Bridged SBI在有限HF模拟成本下生成更准确、可靠的HF后验分布。
原文摘要 · Abstract (English)
Accurate calibration of particle-based simulators is crucial for robotic earthwork simulation, but analytical calibration is challenging due to this task's highly nonlinear particle dynamics and the black-box nature of conventional simulators. Although simulation-based inference (SBI) can estimate posterior distributions over simulation parameters solely from forward simulations, applying SBI directly to high-fidelity (HF) particle simulators is often computationally prohibitive. Low-fidelity (LF) simulators with coarser particles can reduce this cost, but changes in particle size and particle count shift the parameter values needed to reproduce the same observation, producing biased LF posteriors. We propose Bridged SBI, which leverages a biased but informative LF posterior to guide HF inference. This method first uses inexpensive LF simulations to identify a coarse high-density parameter region, and then it learns a local residual bridge to transport LF posterior samples toward HF-consistent regions by correcting the LF--HF discrepancy. We analyze how sequential multi-fidelity SBI (Naive-MF) can suffer from LF-induced posterior miscoverage when it directly relies on the LF posterior without discrepancy correction. We then show that Bridged SBI is designed to alleviate this issue by explicitly modeling the LF--HF discrepancy through residual correction. Experiments on both sim-to-sim particle-parameter calibration and real-to-sim calibration with real soil observation show that Bridged SBI produces more accurate and reliable HF posteriors than HF-only SBI or the Naive-MF baseline, especially under limited HF simulation costs.
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