Sensitivity Based Selection of an Optimal Cable-Driven Parallel Robot Design for Rehabilitation Purposes

Abstract

This paper deals with the design of an optimal cable-driven parallel robot (CDPR) for upper limb rehabilitation. The robot’s prescribed workspace is identified with the help of an occupational therapist based on three selected daily life activities, which are tracked using a Qualisys motion capture system. A preliminary architecture of the robot is proposed based on the analysis of the tracked trajectories of all the activities. A multi-objective optimization process using the genetic algorithm method is then performed, where the cable tensions and the robot size are selected as the objective functions to be minimized. The cables tensions are bounded between two limits, where the lower limit ensures a positive tension in the cables at all times and the upper limit represents the maximum torque of the motor. A sensitivity analysis is then performed using the Monte Carlo method to yield the optimal design selected out of the non-dominated solutions, forming the obtained Pareto front. The robot with the highest robustness toward the disturbances is identified, and its dexterity and elastic stiffness are calculated to investigate its performance.

A Planar Cable-Driven Under-Sensing Model to Measure Forces and Displacements

“…The distance between the black continuous line and the dashed lines of the six anchor points is reduced, underlining the excellent prevision of the mechanical behaviour of the system. This graph validates the formulations presented in the last sections of this paper and is in line with the results of the simulation shown in Figure 6, validating Equation (26). Figure 10 (left) shows the comparison between the measured displacement of the spring and the measured X displacement of the force application point, underlining how no correlations are noted between point P and the motion of the springs and giving other positive outputs to the formulations presented in this paper because only the presented formulation is able to give the correlation between the spring displacement and motion of point P.…”

“…), but their use on a miniaturised scale and in under-sensitive systems is very limited [5,19]. Recently, redundant cable-driven parallel robots (CDPRs) have been used not only for actuation but also for force distribution sensitivity [5,[19][20][21][22][23][24][25], applied in many domains such as rehabilitation [26], and defining cable tension sensitivity analysis for macroscopic applications, such as maintaining a camera in suspension for a football match [27]. Cable-driven systems are also used to achieve maximum workspace and isotropic force exertion, such as shown in [28].…”

A hybrid cable-driven parallel robot as a solution to the limited rotational workspace issue

“…1. The experimental setup is presented with more details in our previous work [27]. A local frame (X h , Y h , Z h ) was attached to the participant's hand.…”

Recent Trends on Innovative Robot Designs and Approaches

“…Even the use and function of robots on assembly lines and in other conventional frameworks are being extensively altered in favor of innovative flexible and agile manufacturing methods. Novel designs are also being extensively researched, including cable-driven parallel robots (CDPRs), as their conceptual design can provide a key performance in terms of large workspace, reconfigurability, large payload capacity, and dynamics [13][14][15][16].…”