# Analysis of Dynamic Behavior of ParReEx Robot Used in Upper Limb Rehabilitation
## 8 Conclusions  
In this paper, we conducted a study on the dynamics of the ParReEx robot used for the wrist joint. Dynamic analysis was performed using MSC.ADAMS in three simulation scenarios:  
1. Kinematic elements were considered rigid bodies and friction in the kinematic couplings was not considered;
2. Kinematic elements were considered rigid bodies and friction in the robot couplings was considered;
3. Both flexibility of kinematic elements and friction in the couplings were considered. Structural optimization of the circular guide of the ParReEx robot using ANSYS software was performed. The differences between the experimentally measured values and those obtained by numerical simulation are acceptable for the following reasons:  
* Parts made by 3D printing have tolerances within 0.2 mm. For this reason, the experimental model is in real assembly conditions;
* Similar variations of torsional moments were determined experimentally and by numerical simulation in ADAMS, which validates the two models.  
Figure 42: Evolution of the maximum values for the moments of actuation for flexion–extension and radial–ulnar deviation motions.  
Dynamic analysis allows us to draw conclusions about the operational safety of a robotic system. A next step is dynamic optimization of the robotic structure. Structural optimization can eliminate stress concentrators in the robot structure, which contributes to increased operational safety.  
The results obtained by numerical simulation were validated by experimental measurements. Thus, the actuation moments for the two movements of the wrist joint--flexion-extension and radial-ulnar deviation--were determined experimentally. Concordance between the variations determined by numerical simulation and those determined experimentally was observed.  
Conceptualization, D.T., I.D.G., D.P. and G.C.; methodology, D.T., I.D.G. and D.P.; software, I.D.G. and D.T.; validation, P.T., B.G., N.T., C.A. and D.N.T.; formal analysis, I.D.G., P.T. and B.G.; investigation, I.D.G., D.T. and D.P.; resources, D.T.; writing--original draft preparation, I.D.G. and D.T.; writing--review and editing, D.P., B.G. and G.C.; visualization, D.N.T., N.T. and C.A.; supervision, D.T., D.P. and G.C.; project administration, D.P. All authors have read and agreed to the published version of the manuscript.  
This work was supported by a grant from the Romanian Ministry of Research and Innovation, CCCDI--UEFISCDI, project number PN-III-P2-2.1-PED-2019-3022/546 PED/2020 (NeuroAssist) within PNCDI III, and by the project POCU/380/6/13/123927--ANTREDC, \"Entrepreneurial competencies and excellence research in doctoral and postdoctoral studies programs\", co-funded from the European Social Fund through the Human Capital Operational Program 2014-2020.  
Not applicable.  
All subjects gave their informed consent for inclusion before they participated in the study. The study was conducted in accordance with the Declaration of Helsinki, and the protocol was approved by the Ethics Committee of NeuroAssist project.  
The data presented in this study are openly available in the reference number.  
The authors declare no conflict of interest.