## 5 Conclusions  
In summary, the design selection process adheres to the engineering design methodology, commencing with the description of a well-defined problem, assimilating background information, generating multiple potential solutions, and culminating in the meticulous analysis and selection of the most optimal solution. Three distinct CAD models were systematically created and subjected to comprehensive evaluations, employing finite element analysis and motion analysis techniques to assess the center of gravity, lift forces, and torques during operational scenarios.  
The evaluation process involved the utilization of a design decision matrix featuring 11 distinct criteria, aimed at identifying the design that optimally balances safety and functionality for both the patient and collaborative lower exoskeleton. Notably, the exclusion of noise level and force required to move from the design criteria was deliberate, considering the infeasibility of determining noise levels through a CAD model and the uniformity in the base and wheel setup across all designs, fostering consistency in the focus area of lift and tilt mechanisms.  
The results were consistent with expectations, as Design 1 showcased superior performance in terms of price, stability, and strength. Design 2 excelled in the force required to move the patient and demonstrated strength, albeit falling behind in price and stability. Design 3 displayed excellence in ease of motion and safety but exhibited shortcomings in strength and cost. Overall, Design 1 received the highest score in the matrix evaluation, establishing it as the top-performing design.  
This research holds substantial significance for advancing the robotic walking training device by eliminating the current harnessed system prevalent in contemporary gait rehabilitation with exoskeleton robotic devices. Placing the patient in a supine starting position enhances the ease of use for both patients and healthcare professionals, opening avenues for individuals who are unable to walk. The device, when employed in the supine position, facilitates patient exercise, promoting increased blood flow to the lower extremities and addressing a critical aspect of rehabilitation.  
Conceptualization, A.B., C.-H.G. and B.R.; methodology, A.B., C.-H.G. and B.R.; software, A.B.; validation, C.-H.G. and B.R.; formal analysis, A.B.; investigation, A.B. and C.-H.G.; investigation, C.-H.G. and B.R.; resources, C.-H.G. and B.R.; data curation, A.B.; project administration, C.-H.G. and B.R.; writing--original draft preparation, A.B.; writing--review and editing, C.-H.G. and B.R.; visualization, A.B. and C.-H.G.; supervision, C.-H.G. and B.R.; project administration, C.-H.G. and B.R. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy.  
This project has been partially supported by [PERSON] at the University of Texas at Tyler (currently at Rochester Institute of Technology) since 2019. [PERSON] is grateful for his support in building a prototype of the robotic walking training device (RWTD).  
The authors declare no conflicts of interest.