Generalizable whole-body global manipulation of deformable linear objects by dual-arm robot in 3-D constrained environments

TL;DR

A complementary framework with whole-body planning and control using appropriate DLO model representations that can efficiently solve the high-dimensional problem subject to all those constraints and generalize to various DLOs without elaborate model identifications is proposed.

Abstract

Constrained environments are common in practical applications of manipulating deformable linear objects (DLOs), where movements of both DLOs and robots should be constrained. This task is high-dimensional and highly constrained owing to the highly deformable DLOs, dual-arm robots with high degrees of freedom, and 3-D complex environments, which render global planning challenging. Furthermore, accurate DLO models needed by planning are often unavailable owing to their strong nonlinearity and diversity, resulting in unreliable planned paths. This article focuses on the global moving and shaping of DLOs in constrained environments by dual-arm robots. The main objectives are 1) to efficiently and accurately accomplish this task, and 2) to achieve generalizable and robust manipulation of various DLOs. To this end, we propose a complementary framework with whole-body planning and control using appropriate DLO model representations. First, a global planner is proposed to efficiently find feasible solutions based on a simplified DLO energy model, which considers the full system states and all constraints to plan more reliable paths. Then, a closed-loop manipulation scheme is proposed to compensate for the modeling errors and enhance the robustness and accuracy, which incorporates a model predictive controller that real-time adjusts the robot motion based on an adaptive DLO motion model. The key novelty is that our framework can efficiently solve the high-dimensional problem subject to multiple constraints and generalize to various DLOs without elaborate model identifications. Experiments demonstrate that our framework can accomplish considerably more complicated tasks than existing works, with significantly higher efficiency, generalizability, and reliability.

Figures (21)

• Figure 1: Illustration of the task: whole-body global manipulation of DLOs by a dual-arm robot in 3-D constrained environments. Given the environment and goal configuration, the proposed approach achieves collision-free moving and shaping of the DLO from start to goal configuration, during which the whole body of the DLO and robot is considered.
• Figure 2: Discrete representation of DLO configuration. (a) The vertices and edges for discretizing the DLO; (b) The Bishop frame and material frame attached to each edge.
• Figure 3: Relationships between the global planner, local controller, and their corresponding DLO models in the proposed complementary framework.
• Figure 4: Two examples of projecting randomly sampled invalid DLO configurations to stable configurations by (\ref{['eq:dlo_projection']}). The material frames $\bm m_1$ and $\bm m_2$ of the projected configurations are shown by the blue and green arrows, respectively.
• Figure 5: Comparison between the direct linear interpolation (a) and our DLO interpolation method (b). The lines represent the DLO centerlines; the arrows indicate the directions from left to right ends; the rectangles indicate the poses of DLO ends; and $\eta \in [0, 1]$ refers to the interpolation ratio.