统一标定双臂机器人坐标与运动参数,减少误差累积。
A Unified Calibration Framework for Coordinate and Kinematic Parameters in Dual-Arm Robots
- 用李代数统一建模坐标与运动参数,避免误差分离。
- 提出闭式解析雅可比,保证优化稳定且可识别所有参数。
- 设计可验证最优性的初始化算法,提升联合优化可靠性。
视觉引导的双臂机器人协同需要精确系统标定。现有方法虽能同步求解多个坐标变换,但或把运动误差视为隐式噪声,或采用分离误差建模,导致显著累积误差。本文提出一种统一标定双臂机器人坐标变换与运动参数的新框架。核心思想是将所有强耦合参数统一于单一李代数形式中。基于指数积公式构建综合误差模型,自然以旋量形式整合坐标与运动参数,不引入人工误差分离,有效缓解误差传播。此外,通过李导数推导出闭式解析雅可比,并分析其秩性质,证明在弱条件下联合优化是适定的,使标准迭代求解器可在流形空间上稳定优化。为保障联合优化的鲁棒收敛,开发了一种可验证正确性的坐标初始化算法,基于半定松弛,可获得可靠初始值,其近全局最优性可事后验证。大量实验表明,在相同视觉测量下,本方法精度显著优于基线;且可验证初始化始终优于仅坐标标定的基线,证明其作为联合优化起点的可靠性。
原文摘要 · Abstract (English)
Precise collaboration in vision-based dual-arm robot systems requires accurate system calibration. Recent dual-robot calibration methods have achieved strong performance by simultaneously solving multiple coordinate transformations. However, these methods either treat kinematic errors as implicit noise or handle them through separated error modeling, resulting in non-negligible accumulated errors. In this paper, we present a novel framework for unified calibration of the coordinate transformations and kinematic parameters in both robot arms. Our key idea is to unify all the tightly coupled parameters within a single Lie-algebraic formulation. To this end, we construct a consolidated error model grounded in the product-of-exponentials formula, which naturally integrates the coordinate and kinematic parameters in twist forms. Our model introduces no artificial error separation and thus greatly mitigates the error propagation. In addition, we derive a closed-form analytical Jacobian from this model using Lie derivatives. By exploring the Jacobian rank property, we analyze the identifiability of all calibration parameters and show that our joint optimization is well-posed under mild conditions. This enables off-the-shelf iterative solvers to stably optimize these parameters on the manifold space. Besides, to ensure robust convergence of our joint optimization, we develop a certifiably correct algorithm for initializing the unknown coordinates. Relying on semidefinite relaxation, our algorithm can yield a reliable estimate whose near-global optimality can be verified a posteriori. Extensive experiments validate the superior accuracy of our approach over previous baselines under identical visual measurements. Meanwhile, our certifiable initialization consistently outperforms several coordinate-only baselines, proving its reliability as a starting point for joint optimization.
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