MOB-Net: Limb-modularized uncertainty torque learning of humanoids for sensorless external torque estimation

Daegyu Lim, Myeong-Ju Kim, Junhyeok Cha, Jaeheung Park
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Abstract

Momentum observer (MOB) can estimate external joint torque without requiring additional sensors, such as force/torque or joint torque sensors. However, the estimation performance of MOB deteriorates due to the model uncertainty which encompasses the modeling errors and the joint friction. Moreover, the estimation error is significant when MOB is applied to high-dimensional floating-base humanoids, which prevents the estimated external joint torque from being used for force control or collision detection in the real humanoid robot. In this paper, the pure external joint torque estimation method named MOB-Net, is proposed for humanoids. MOB-Net learns the model uncertainty torque and calibrates the estimated signal of MOB, substantially reducing the estimation errors of MOB. The external joint torque can be estimated in the generalized coordinate including whole-body and virtual joints of the floating-base robot with only internal sensors (an IMU on the pelvis and encoders in the joints). Furthermore, MOB-Net shows more robust performance for the unseen data compared to the end-to-end learning method, and the robustness of MOB-Net is validated through extensive simulations, real robot experiments, and ablation studies. Finally, various collision handling scenarios are presented to show the versatility of MOB-Net: contact wrench feedback control for locomotion, collision detection, and collision reaction for safety.
MOB-Net:用于无传感器外部扭矩估算的人形机器人肢体模块化不确定性扭矩学习
动量观测器(MOB)可以估算外部关节扭矩,而不需要额外的传感器,如力/扭矩或关节扭矩传感器。然而,由于模型的不确定性(包括建模误差和关节摩擦),MOB 的估计性能会下降。此外,当 MOB 应用于高维浮动基座仿人机器人时,估算误差很大,导致估算的外部关节扭矩无法用于实际仿人机器人的力控制或碰撞检测。本文针对仿人机器人提出了一种名为 MOB-Net 的纯外部关节扭矩估算方法。MOB-Net 可学习模型不确定性扭矩并校准 MOB 的估计信号,从而大幅降低 MOB 的估计误差。只需使用内部传感器(骨盆上的 IMU 和关节中的编码器),就能在广义坐标中估算出外部关节扭矩,包括浮动基座机器人的全身关节和虚拟关节。此外,与端到端学习方法相比,MOB-Net 在处理未见数据时表现出更强的鲁棒性,并且 MOB-Net 的鲁棒性通过大量仿真、真实机器人实验和烧蚀研究得到了验证。最后,介绍了各种碰撞处理场景,以展示 MOB-Net 的多功能性:用于运动、碰撞检测和安全碰撞反应的接触扳手反馈控制。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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