## 3 Results
### Decision Matrix  
To impartially assess each design, a comprehensive decision matrix was formulated, encompassing 11 distinct weighted criteria, each of which pertains to the RWTD lift mechanism as shown in Figure 13. These criteria serve as diverse requirements essential for evaluating the performance and functionality of the RWTD. The 11 criteria are as follows:  
1. Weight
2. Size
3. Number of Motors
4. Number of Joints
5. Noise Level
6. Force Required to Lift Patient
7. Force Required to Move the Device
8. Center of Gravity (Tipping)
9. Price
10. FEA Structural Strength
11. Number of Pinch Points  
Each of these criteria addresses a pivotal aspect of RWTD's operation. For instance, criteria such as weight, size, and force required to move are used to assess the device's transportability. Others, such as the number of pinch points, center of gravity, and noise level, focus on evaluating the device's safety for both patients and therapists.  
To establish the weighted values for these criteria, an algorithmic approach was adopted. This approach derives the weights based on correlations between customer  
Figure 12: Design 3 (double pivot lift) torque results. Top: torque on the back motor which controls the larger pivot. Bottom: torque on the front motor which controls the smaller pivot.  
requirements and functional specifications. The highest level of importance was assigned to the center of gravity, as it plays a substantial role in the device's safety, functionality, and structural design. Conversely, the overall weight of the device received a lower importance rating since, given that the device is primarily motor-driven, it remains a significant consideration but is comparatively less critical than the other criteria.  
Among the three design variants, \"Rotational Lift,\" representing Design 1, emerged as the top performer in the decision matrix. It obtained the highest total score, with noteworthy results in several key areas, particularly excelling in center of gravity, price, and size.  
In Figure 13, the scoring system utilized a range from 1 to 9 to assess each criterion in relation to the target goal. A score of 9 signified an excellent achievement, while a score of 6 indicated performance above the average standard. Scores of 3 and 1 were assigned to criteria that were below average and poor, respectively.  
In the decision matrix, two criteria, noise and force required to move, were not assessed due to specific constraints and conditions.  
The noise criterion was excluded from the evaluation because a noise analysis could not be conducted using a CAD (computer-aided design) model. Accurately assessing the noise level of the device necessitates a physical mechanism to generate the noise, which is typically achieved through experimental testing. Nonetheless, it is important to acknowledge that noise remains a critical aspect of the design, and it must adhere to OSHA (Occupational Safety and Health Administration) requirements, ensuring that it does not necessitate noise protective gear and complies with safety regulations.  
The force required to move criterion was omitted from this analysis because all the designs featured the same wheel and base configurations. Consequently, the force required to push or move the device was considered directly proportional to the weight of the device.  
Figure 13: Decision matrix.  
In such a scenario, this criterion became redundant for distinguishing between the design variants since it did not provide meaningful differentiation.  
These exclusions were made based on the specific limitations and uniformities within the designs, but it is essential to recognize their significance in the broader context of the device's functionality and safety. The robust performance of Design 1, particularly in terms of center of gravity, price, and size, underscores its strong suitability and competence with respect to these vital aspects of the RWTD design.