cs.ROOct 12, 2026

Extending Wire-Driven Parallel Robots to Multi-Floating-Link Systems with an Inter-Body Wire

Authors: Shintaro Inoue, Kento Kawaharazuka, Temma Suzuki, Sota Yuzaki, Keita Yoneda, Kei Okada

Organizations: Department of Mechano-Informatics, Graduate School of Information Science and Technology, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

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Abstract

Parallel wire-driven systems are a framework in which multiple wires are connected to an end effector, and the end effector is driven by the tensions of those wires. Because they can transmit large forces, up to the breaking strength of the wires, over lengths on the order of several tens of meters, they can realize powerful actuation in large workspaces. In recent years, studies have also investigated connecting wires to external environments such as trees and columns and forming parallel wire actuation on site. However, conventional parallel wire-driven systems often assume a single end effector, and because of interference between wires and links in a shared workspace, it has been difficult to handle multiple floating links simultaneously. In this study, we realize multi-floating-link parallel wire actuation by introducing an inter-body wire. In real-robot experiments, the two bodies supported and lifted a mannequin and transferred it onto a stretcher as a rescue motion. This shows that parallel wire actuation can be extended from a single end effector to a multi-floating-link system, and indicates its potential for broader tasks such as the manipulation of large objects and rescue support.

Figures & tables

Fig. 1: Overview of the TwinX, a multi-floating-link parallel wire-driven system. Two wheeled-legged robots are connected by an inter-body wire, and each robot can also anchor wires to the environment.
Fig. 2: Representative example illustrating the effect of the inter-body wire on feasible workspace. The top row shows wire configurations without and with the inter-body wire. The bottom row shows feasible pairs of horizontal positions (x1,x2)(x_{1},x_{2}) for fixed heights (y1,y2)(y_{1},y_{2}) . Gray indicates pairs that are feasible without the inter-body wire, while green indicates pairs that become newly feasible after adding the inter-body wire.
Fig. 3: Overall hardware configuration of TwinX. TwinX consists of two identical robot bodies, WiXus-Blue and WiXus-Red, connected by a single inter-body wire. Each body is a wheeled-legged robot and can additionally connect its wires to the environment using flying anchors.
Fig. 4: Definition of symbols used in the multi-link parallel wire-driven controller.
Fig. 5: Pipeline for multi-link parallel wire-driven control. By exchanging localization outputs and the corresponding Jacobian components via UDP, both robots reconstruct and maintain the same whole-system Jacobian. Using this Jacobian, each robot computes gravity compensation and feedback control terms for the entire coupled system, and then applies only the resulting commands corresponding to its own actuators to the motors.
Fig. 6: Simulation setup for the performance evaluation. The world coordinate frame is defined as shown in the figure. Four wires are attached to anchor points. WiXus-Blue and WiXus-Red are additionally connected by an inter-body wire.
Fig. 7: Tracking results in simulation. The left column shows the measured and reference body positions, and the right column shows the reference wire tensions. For each robot, f1reff_{1}^{\mathrm{ref}} and f2reff_{2}^{\mathrm{ref}} denote the tensions of the environment-anchoring wires connected to the −y-y and +y+y anchors, respectively; the same finterreff_{\mathrm{inter}}^{\mathrm{ref}} is shown in both plots, yielding five distinct wire tensions.
Fig. 8: Boxplots of the position error norm for WiXus-Blue and WiXus-Red, grouped by whether the relative position was preserved ( keep ) or changed ( change ), and by whether the robot was moving toward a target ( MOVE ) or holding a target position ( HOLD ).
Fig. 9: Real-robot rescue-task demonstration. Phase 1: four wires are attached to ceiling pillars using flying anchors. Phase 2: TwinX lifts the patient at the waist and legs and transfers the patient onto the stretcher by multi-floating-link parallel wire actuation. Phase 3: the wires are detached and recovered. Phase 4: TwinX reconfigures into the vehicle configuration and tows the stretcher.
Fig. 10: Trajectories of the four flying anchors while attaching the wires to the environment during the integrated rescue-task experiment.
Fig. 11: Time-series body positions and reference wire tensions during multi-link parallel wire driving in the integrated rescue-task experiment. For each robot, f1reff_{1}^{\mathrm{ref}} and f2reff_{2}^{\mathrm{ref}} denote the tensions of the environment-anchoring wires connected to the −y-y and +y+y anchors, respectively; the same finterreff_{\mathrm{inter}}^{\mathrm{ref}} is shown in both plots, yielding five distinct wire tensions.
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