# Knowledge-Based Automated Mechanical Design of a Robot Manipulator
## 2 Materials and Methods
### Cad Model
#### 2.2.1 \(n\)-th Link Design  
In this step, the force and torque effects were taken into account. The individual elements of the manipulator were designed iteratively, beginning from the end-effector towards the base. Thus, the first proposed element is the part connecting the end effector with the next drive unit. Figures 5 and 6 are flow charts that describe the design and general procedure of the \(n\)-th component, including the respective drive units. The design process depends on the link length. Short links consist of one structural element and long links from three elements. As part of this procedure, we divided the elements of the robotic arm into two main categories. The first contains off-the-shelf or otherwise reused over elements (drive units, end effectors, sensors, etc. ), for which we cannot change the parameters, shape, or individual dimensions. The second category contains mainly load-bearing and connecting elements, which were designed on the basis of predefined rules, but we can change the shape, dimensions, and selected parameters (e.g., material). Based on the lengths of the individual links in the proposed kinematic structure of the robotic arm, one of the two design paths of the nth element was chosen. The length of the kinematic \(n\)-link was compared to the diameter of the previous (\(n-1\)) link's drive unit, or in the case of the first link, the end-effector length was used. If the length of the \(n\)-link exceeds the size of the drive unit (or end-effector) size by more than a factor of four, we considered it long enough to be built from three elements bolted, welded, or glued together. Otherwise, the \(n\)-th link will be built from just one structural element. Figure 7 shows examples of links designed from one and three structural elements. Figure 5: Design procedure of the \(n\)-th link if the link consists of one element. Figure 6: Design procedure of the \(n\)-th link if the link consists of three elements. If the link consists of one piece of material, kinematic and dynamic analysis of the manipulator's 3D model is performed first. Within these analyzes, a 3D model created on the basis of the proposed kinematic structure with the smallest possible overall dimensions was used. Within this model, the original elements were gradually replaced by elements designed according to the procedure indicated in Figures 5 and 6. The data obtained from these analyses were then used in the preliminary design of the drive unit located in the following joint (using a modified version of the DrivePicker software tool [18]. Based on the drive unit dimensions, relative position to the previous joint, and the respective connection dimensions (flanges), a suitable parameterized 3D model was selected from the database. The model has its parameters set appropriately for this use case. The next step of the design was similar to a design study in CAD system SolidWorks, which aimed at the dimensional optimization of the element in such a way as to suit both in terms of strength and especially in terms of maximum deformation, while achieving the lowest possible weight. If it is not possible to get the desired results with this element, another candidate 3D model is selected from the database as the basis of the \(n\)-th element and the process is repeated until a suitable solution is found. Then, a collision analysis is performed again. The purpose of this analysis was to determine whether the model update caused no new collision states. If no collisions are found, the kinematic and dynamic analysis is performed again, and the selected preliminary drive unit is checked. If it is possible to use the originally designed drive unit or a unit with the same connection dimensions, it is possible to end the design of the \(n\)-th element and continue with the design process for the next link in the manipulator.