Modélisation d’un robot SCARA à structure complexe (Parallèle) destiné à manipuler une sonde échographique

Abstract

Robotic tele-ultrasound—viewed as a system comprising several modules (master station, slave station, communication, imaging, videoconferencing, etc.)—enables an expert operator to remotely assist with an ultrasound examination. This is particularly relevant when a patient cannot access optimal care locally and might otherwise need to travel to another city to be examined by experts; such travel is not always advisable, as it can pose risks. Against this backdrop, this work focuses on developing a high-performance robotic tele-ultrasound system that leverages superior ultrasound image quality and a portable structure offering a large workspace. Such a robot would allow experts to conduct remote examinations on patients in towns or villages on a continuous basis, without requiring highly qualified personnel on-site. A study of existing tele-ultrasound robots led to the selection of a family of topologies that serves as the basis for the proposed solution. Analyzing the movements performed by medical experts helped define the robot's required motions—a key parameter in the design specifications. The proposed structure utilizes a parallel-kinematics SCARA-type manipulator, chosen for its advantages regarding mobility, compact size, and a workspace that remains nearly parallel to the scanning surface. We evaluated configurations featuring a wrist with three concurrent axes versus one with three non-concurrent axes. Geometric and kinematic modeling of this robot type allows us to select the wrist configuration that ensures optimal operation of the ultrasound probe. The manipulator featuring a wrist with three non-intersecting axes appears to be the most suitable choice; it allows the probe to examine the organ without encountering singularities (which lie outside the diagnostic zone). Additionally, a dynamic analysis was conducted to facilitate predictive control of the robot. Finally, we developed a MATLAB program to calculate and verify the robot's geometric and kinematic models.