# Control Methods Comparison for the Real Quadrotor on an Innovative Test Stand
## 2 Design of Test Stands
### Test Stand for Verification of Control Techniques  
The second test stand was used to verify and evaluate the control technique applied to a real quadrotor. Before the design of an own test stand, several already existing test stands were analyzed. Table 1 lists the comparison of test stands focusing on DOFs and testing range. The innovative design of a new test stand taken into account the following requirements: increased safety (protet quadrotor and its surroundings), 6 DOF and minimal momentum of inertia. Designed test stand provides absolute information about orientation of the quadrotor during verifying designed attitude controllers. The designed test stand was comprised of two parts--an unmoving metal part which holds a rotary part which can rotate around all three axes. It can be used to mount and; therefore, to test any VTOL platform whereby the maximum dimension is not greater than 0.75 m, including the length of propellers. The rotary part was comprised of carbon tubes and polymer parts including the ball bearings (Figure 4/Figure 5 part 1, 2 and 3). Magnetic rotary sensors are mounted on these polymer parts and provide the following measurements: pitch, roll, yaw and their corresponding angular velocities. VTOL platform can be mounted on a plate with dimension \(0.1\times 0.1\) m in the center of the test stand. The quadrotor can be adjusted in \(z\) axis so that the plane of the propellers contains the \(x\) and \(y\) axis of rotation of the test stand. The module 1 measures roll, module 2 measures pitch and module 3 measures yaw angle (Figures 4 and 5). All modules are powered from external power supply via cables which are laid inside the carbon tubes. The transition between moving parts is provided through the rotary contacts. Figure 4 shows a test stand designed in CAD software and the real prototype is shown in Figure 5.  
Figure 3: Relationship between measured voltage and test weight. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Test Stand** & **DOF** & **Testing Range** & **Disadvantages** \\ \hline A prototype constructed in [42] & 3 & Orientation (with restriction) & Quadrotor is irreplaceable part of the test stand \\ \hline Heli–Safe flight test stand [43] & 3 & Orientation & Test stand does not contain any sensors \\ \hline Test stand composed of a sphere & 3 & Orientation and position (with restriction) & Price \\ sensor [41] & & & \\ \hline Checkerboard with the three & 6 & Orientation and position (with restriction) & Safety, initializing error \\ differently colored active markers [44] & & & \\ \hline [PERSON] training stand [45] & 2 & Orientation (possibly 5 DOFs) & Weight \\ \hline Test stand constructed by [PERSON] [46] & 3 & Orientation (with restriction) & Quadrotor is irreplaceable part of the test stand \\ \hline Customized Whitman training & & & \\ stand used, allowing VTOL & 5 & Orientation and position (with restriction) & Weight, size \\ platform movement in 5 DOFs [47] & & & \\ \hline Test stands integrating a & 3 & Orientation & Quadrotor is irreplaceable part of the test stand \\ \hline Test stands integrating a & 3 & Orientation (with restriction) & Roll and pitch angle \\ quadrotor [48] & 3 & restriction) & restricted to 30\({}^{\circ}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Usage, disadvantages and possible degrees of freedom (DOF) of analyzed test stands. Figure 4: Design of test stand made in CAD software. The communication scheme is shown in Figure 6. The stand was comprised of four modules, from which three are slaves used to measure orientation represented by blocks 1, 2 and 3 in Figures 4 and 5.