针对复杂物体的力控抓取,提出自适应力跟踪新方法。
An Adaptive Grasping Force Tracking Strategy for Nonlinear and Time-Varying Object Behaviors
- 引入广义刚度概念,用LSTM在线估计非线性时变物体特性。
- 基于广义刚度动态调整控制器参数,实现高精度力跟踪。
- 适合抓取软、塑性等复杂材料,提升机器人在真实环境中的适应性。
精准的抓取力控制是确保机器人成功且无损抓取物体的关键技能。尽管现有方法在滑移检测和抓取力规划方面已有深入研究,但常忽略不同材料特性下实际力对目标力的自适应跟踪问题。力跟踪控制器的最佳参数显著受物体刚度影响,许多自适应算法依赖刚度估计,而现实物体常表现出粘性、塑性等更复杂的非线性时变行为,现有研究在刚度定义与估计上支持不足。为此,本文提出广义刚度概念,将刚度定义扩展至非线性时变抓取系统模型,并基于长短期记忆网络(LSTM)设计在线广义刚度估计算法。基于此,本文以比例积分(PI)控制器为例,提出自适应参数调节策略,实现对不同特性的物体的动态力跟踪。实验结果表明,该方法具备高精度和短探测时间,在非理想物体上的适应性优于现有方法。所提方法有效解决了未知、非线性、时变抓取系统中的力跟踪问题,展现了神经网络的泛化能力,增强了机器人在非结构化环境中的抓取能力。
原文摘要 · Abstract (English)
Accurate grasp force control is one of the key skills for ensuring successful and damage-free robotic grasping of objects. Although existing methods have conducted in-depth research on slip detection and grasping force planning, they often overlook the issue of adaptive tracking of the actual force to the target force when handling objects with different material properties. The optimal parameters of a force tracking controller are significantly influenced by the object's stiffness, and many adaptive force tracking algorithms rely on stiffness estimation. However, real-world objects often exhibit viscous, plastic, or other more complex nonlinear time-varying behaviors, and existing studies provide insufficient support for these materials in terms of stiffness definition and estimation. To address this, this paper introduces the concept of generalized stiffness, extending the definition of stiffness to nonlinear time-varying grasp system models, and proposes an online generalized stiffness estimator based on Long Short-Term Memory (LSTM) networks. Based on generalized stiffness, this paper proposes an adaptive parameter adjustment strategy using a PI controller as an example, enabling dynamic force tracking for objects with varying characteristics. Experimental results demonstrate that the proposed method achieves high precision and short probing time, while showing better adaptability to non-ideal objects compared to existing methods. The method effectively solves the problem of grasp force tracking in unknown, nonlinear, and time-varying grasp systems, demonstrating the generalization capability of our neural network and enhancing the robotic grasping ability in unstructured environments.
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