## 4 Use Case Example: Deriving Electromagnetic Requirements for An Elevator Application
### Deriving Requirements into Disciplines  
The requirements are imported from Doors to Bhapsody to illustrate the process of derivation. In order to derive requirements into the different disciplines for this customized motor design, first, the operation characteristics curves (speed, torque, acceleration, jerk, and position) of the system must be obtained. A system assessment is carried out due to the initial specification not presenting these curves. The initial specification does present the important parameters to derive these curves. The equations that model the behavior of the system were obtained and agreed among the stakeholders  
\begin{table}
\begin{tabular}{l l} \hline \hline
**Requirement Package ID** & **Package Name** \\ \hline InRS & Integrator’s requirements \\ MechRS & Mechanical engineering requirements \\ ElecRS & Electrical engineering requirements \\ ControlRS & Control engineering requirements \\ ManufRS & Manufacturing engineering requirements \\ ObjRS & Set objectives during the development process \\ ElectmgnRS & Electromagnetic requirements \\ \hline \hline \end{tabular}
\end{table}
Table 2: Requirement Package IDs.  
Figure 9: Initial requirements classification in Rational Doors.  
The operating characteristics curves were obtained for a trip distance of 7.2 m, i.e., two floors of 3.6 m in height. The trip ends in 8 s, and at that distance, the brake is activated releasing the motor from doing work. The minimum time that is required by the elevator system to stop is 12 s, time for doors to open, people to get in/off, and doors to close. Therefore, the worst case scenario thermally speaking is to study a cycle of 20 s. All the aforementioned information is captured in the diagram to illustrate the derivation of mechanical requirements.  
The requirement diagram in Figure 12 shows the relationships of this elevator operation characteristics requirement derived as a mechanical requirement from the initial requirements. Figure 13 shows the parametric diagrams that refine this requirement. Although not being shown in the figure, for each characteristic curve a mechanical requirement is also created, i.e., this requirement contains five mechanical requirements one for each curve. These are used later to derive the electromagnetic requirements.  
Figure 12: Mechanical requirements derivation.  
Figure 14 shows some electrical requirements derivation relationships; it can be seen that some requirements may just be copied from the initial requirements. However, with a different id, to know to which specialized package it belongs. In summary, the converter is specified; due to its specifications, the motor shall be a three-phase motor with a current less than or equal to 15 A and the rated line-to-line voltage is limited to 400 V. The converter has the option of using space vector pulse-width modulation (PWM). Accordingly, a control requirement is derived stating to use this type of modulation because the operating voltage obtained from it is a maximum, thus lowering the operating current.  
Figure 14: Electrical requirements derivation.  
Figure 13: Elevator operator characteristics refinement: (a) Parametric diagram to compute operating characteristics curves; and, (b) Requirement refinement through parametric diagrams.  
The motor selected for this particular case is a surface permanent magnet motor, selected due to the ease of manufacturing leading to lower costs and because the required speeds are considered that can be satisfied by this type of motor.