## 3 Application of the Design Approach to the Definition of the Innovative Test Rig
### Design of the General System ('Test Rig')
#### 3.2.4 Proposal of an Actuation Mechanism (\(\rightarrow\) Step 1.d)  
Taking into account all the considerations presented herein, the following solutions were selected:  
* The operation of the platform is performed by hydraulic linear actuators. These are particularly suitable in such cases as the present because: (1) they are able to develop large thrust forces, (2) they have a high flexibility of positioning thanks to the physical separation among the power-generation system (for pressurizing the operating fluid), the control system (typically: a control panel and an electro-hydraulic distributor) and the power-using system (i.e., the actuator, indicated as 'hydraulic jack');
* The overall inclination of the platform is provided by operating an actuator against the platform support-frame [76], articulated at one end of it with the base. The reference scheme is a triangular pattern with a variable-length link (i.e., the linear actuator; Figure 18, I.a-Ib). In the final project, if the system will require a lighter structure with the same overall structural resistance (capability to support agricultural machines), the indicated kinematic scheme could possibly be replicated by placing two actuators per side which operate simultaneously and in parallel (i.e., at the brim and at the middle of the main frame, Figure 18, I.a-Ib);
* The angle between the two semi-platforms is obtained by acting on one semi-platform only. The second semi-platform is inclined as the result of the position taken by the first one (Figure 18, A.a-A.b). The kinematic scheme for the lower semi-platform which is driving the entire angling mechanism is again a triangle with a variable-length side. Instead, the complete angulation mechanism of the two semi-platforms is similar to a centered crank-mechanism. For practical reasons, i.e., to make it easier for a vehicle to get on and off the platform, the articulated joints of the lower semi-platform and of the main structure of the platform are adjacent. Consequently, the two kinematic mechanisms described before are superimposed as reported in Figure 19. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline \multirow{4}{*}{
\begin{tabular}{} \end{tabular} } & \multicolumn{2}{p{113.8 pt}}{The forces that can be exerted can also be very high, high mechanical robustness, ability to operate in pushing and pulling} & Possible limitations to the maximum extension of the jack (to be checked with the manufacturer of hydraulic components) \\ \cline{2-4}  & & No problem of stroke practicable by the attachment point (if an appropriate structure for positioning a fixed pulley and the winch is provided), possibility of using an electric rotary motor for the winch & The cable elasticity and extension can cause oscillations of the platform during the dynamic tests; need for another system to keep the position of the platform fixed when tilted (therefore, the cable is only used for moving the platform) \\ \cline{2-4}  & & & Limited length of the threaded rod; possible problems of friction in the parts in relative motion; thrust sustained by threads; possible problems for the bar of deviation from the straightness \\ \cline{2-4}  & & & & \\ \cline{2-4}  & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: _Cont._Finally, if after a first dimensioning of the system and the choice of actuators from a catalogue (\(\rightarrow\) Steps 1.d, 1.e) the length of a single, fully-extended hydraulic jack were not sufficient to provide the maximum desired inclination, other alternative solutions should be considered (Figure 20):  
1. (AS1.) Shift of the position of cylinders toward the hinges. The shifting distance is however limited by the need to not interfere with the circular paths of the vehicles under test and with the coupling  
Figure 19: Side schemes of the platform in the ‘at rest’ configuration (**SC1**) or tilted and angled (**SC2**; ‘tiltable’ frame in red; semi-platforms in blue).