Parametric Design of a Cable-Driven Coaxial Spherical Parallel Mechanism for Ultrasound Scans

TL;DR

This paper introduces a parametric design and analysis of a cable-driven coaxial spherical mechanism tailored for medical ultrasound haptic interfaces, emphasizing workspace, dexterity, and dynamic performance improvements.

Contribution

It presents a novel cable-driven spherical mechanism with external rotation center relocation, optimized for medical teleoperation and ultrasound applications.

Findings

Prototype validates mechanical feasibility and kinematic behavior.

Design reduces inertial loads and enhances stiffness.

Mechanism achieves decoupled rotational degrees of freedom.

Abstract

Haptic interfaces play a critical role in medical teleoperation by enabling surgeons to interact with remote environments through realistic force and motion feedback. Achieving high fidelity in such systems requires balancing the trade-offs among workspace, dexterity, stiffness, inertia, and bandwidth, particularly in applications demanding pure rotational motion. This paper presents the design methodology and kinematic analysis of a Cable-Driven Coaxial Spherical Parallel Mechanism (CDC-SPM) developed to address these challenges. The proposed approach focuses on the mechanical design and parametric synthesis of the mechanism to meet task-specific requirements in medical applications. In particular, the design enables the relocation of the center of rotation to an external point corresponding to the tool-tissue interaction, while ensuring appropriate workspace coverage and collision avoidance. The proposed cable-driven interface design allows for reducing the mass placed at the robot arm end-effector, thereby minimizing inertial loads, enhancing stiffness, and improving dynamic responsiveness. Through parallel and coaxial actuation, the mechanism achieves decoupled rotational degrees of freedom with isotropic force and torque transmission. A prototype is developed to validate the mechanical feasibility and kinematic behavior of the proposed mechanism. These results demonstrate the suitability of the proposed mechanism design for future integration into haptic interfaces for medical applications such as ultrasound imaging.