This paper deals with the optimal design of a planar cable-driven parallel robot (CDPR), with three degrees of freedom, intended for assisting the patient’s affected upper limb along a prescribed movement. A Qualisys motion capture system was used to record the prescribed task performed by a healthy subject. For each pose taken by the center of mass of the end-effector, the cable tensions, the elastic stiffness and the dexterity were optimized while satisfying a set of constraints. First, a multiobjective formulation of the optimization problem was adopted. Since selecting a single solution among the multiple ones given by the Pareto front presents an issue, a mono-objective formulation was chosen, where the objective function was defined as a weighted sum of the chosen criteria. The appropriate values of the weighted coefficients were studied with the aim of identifying their influence on the optimization process and, thus, a judicious choice was made. A prototype of the optimal design of the CDPR was developed and validated experimentally on the prescribed workspace using the position control approach for the motors. The tests showed promising reliability of the proposed design for the task.

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.

The optimal design and the experimental validation of a cable-driven parallel robot is discussed in this paper. This novel device is intended for assisting therapists in the rehabilitation of the head–neck joint. First, the motion of the head–neck joint was recorded by means of a Qualisys motion-capture system. The collected data was then analyzed in order to obtain the range of motion of the head and to identify some prescribed trajectories. A novel end-effector design was proposed to reduce the degrees of freedom needed to perform the desired head motion. The best design was found through an optimization problem where the cable tensions are minimized and the robot dexterity is maximized within its workspace. The objective of this optimization was to find the optimal actuator positions while satisfying a set of constraints. A prototype was proposed and experimental tests were conducted to validate the robot performance. In particular, a comparison between the actual trajectories and the desired ones was performed. The experimental test showed promising results.

Cable-driven parallel robots (CDPRs) are still gaining attention thanks to their interesting characteristics compared to serial or classic parallel manipulators. However, the limited range of rotation of their end-effectors reduces their application fields to predominantly translational movements. In this context, the issue of extending the rotational workspace of a CDPR while maintaining a compact robot structure is addressed in this paper. This work is motivated by the need to find the optimal CDPR for upper limb rehabilitation allowing to assist the patient’s hand along a set of prescribed tasks. Firstly, a reconfigurable robot, where the motors’ locations are movable, is proposed in order to help reaching all the prescribed poses. Although this solution presents promising results compared to classical CDPRs, it involves a sizable robot structure inadequate to rehabilitation application. To improve the obtained solution, another approach is proposed, based on combining the large translational workspace of CDPRs and the large rotational workspace of serial manipulators. The optimal structure of a hybrid robot will be considered for the prototype design.