Casting manipulation of unknown string by robot arm

TL;DR

The paper addresses casting manipulation of an unknown string using a standard robot arm, removing the need for specialized casting hardware. It couples motion generation with a mass–spring–damper string model and online string-parameter estimation, formalized via the eight parameters $k_h$, $c_h$, $k_s$, $c_s$, $C_{c1}$, $C_{c2}$, $k_{ph}$, and $c_{ph}$. The method alternates between simulated string dynamics, real-world manipulation, and parameter refinement until the simulated motion aligns with the actual string behavior, enabling the end-effector to reach the target. Experiments across multiple strings, target positions, and obstacle scenarios demonstrate the approach’s robustness and potential to extend the capabilities of home service, exploration, rescue, and entertainment robots.

Abstract

Casting manipulation has been studied to expand the robot's movable range. In this manipulation, the robot throws and reaches the end effector to a distant target. Usually, a special casting manipulator, which consists of rigid arm links and specific flexible linear objects, is constructed for an effective casting manipulation. However, the special manipulator cannot perform normal manipulations, such as picking and placing, grasping, and operating objects. We propose that the normal robot arm, which can perform normal tasks, picks up an unknown string in the surrounding environment and realizes casting manipulation with it. As the properties of the string are not provided in advance, it is crucial how to reflect it in casting manipulation. This is realized by the motion generation of the robot arm with the simulation of string movement, actual string manipulation by the robot arm, and string parameter estimation from the actual string movement. After repeating these three steps, the simulated string movement approximates the actual to realize casting manipulation with the unknown string. We confirmed the effectiveness of the proposed method through experiments. The try of this study will lead to enhancement of the performance of home service robot, exploration robot, rescue robot and entertainment robot.

Figures (17)

• Figure 1: Proposal concept of casting manipulation for unknown string
• Figure 2: String model
• Figure 3: Motion generation by joint velocity curve
• Figure 4: Parameter estimation with matching rate E
• Figure 5: Experimental setup with obstacle object