## 4 Experiments and Results
### Step Response Tests
#### 4.3.2 Step Response Tests at Reference Velocity 30 rad/s  
In this experiment, we compared the linear velocity PI-controller and the OAC-DES at reference velocity \(\omega_{r}=30\) rad/s. The results of the comparison are illustrated in Figure 11, which is organized in the same way as in the last subsection. Therefore, we focus our discussion here on the results according to the three step responses presented in the corresponding graphs.  
Figure 11: Step response at reference velocity \(\omega_{r}=30\) rad/s.  
Step response 1 graphs show similar transient reactions of the linear PI-controller and the OAC-DES. Since velocities are higher, overshoots are recognized by both of them. However, transient peaks, just like the disturbance peaks, are a bit higher in the case of the OAC-DES. More precisely, these range up to 6 rad/s for the OAC-DEC, compared to 4 rad/s for the linear PI-controller. It is important to note that the disturbance peaks of OAC-DES lower due to adaptation, while these remain constant in the case of the linear PI-controller. The reason for the raised disturbance peaks lies in the increased velocity, which increases the number of disturbances per time unit. Thus, the OAC-DES reacts a bit slower and additionally becomes more restless when reference velocity \(\omega_{r}=0\).  
Despite those facts, it seems that the OAC-DES is the better controller even in this case, because it can adapt to arbitrary disturbances. The more disturbances there are, the more \"experienced\" the OAC-DES becomes. As the graph for step response 2 shows, soon after the transient peak emerged during the change from \(\omega_{r}=0\) rad/s to \(\omega_{r}=30\) rad/s, the disturbance hit the non-linear robotic mechanism, resulting in the disturbance peak. The velocity error of the actual velocity \(\omega_{a}\) according to reference velocity \(\omega_{r}\) becomes noticeable. The first disturbance peak is usually the highest of all peaks in the series. The OAC-DES sequentially adapts to those peaks, and each subsequent error is slightly reduced. The sixth disturbance in the series unexpectedly diverges slightly from the OAC-DES, and the adaptation process repeats.  
Another example of adaptation can be seen in the transient response when the reference velocity is changed from \(\omega_{r}=0\) rad/s to \(\omega_{r}=-30\) rad/s. The transient peak is the highest in the series. Then, a bit lower, the first disturbance peak follows, after which all subsequent disturbance peaks are progressively lower. Indeed, we conclude from this that the proposed OAC-DES controller is capable of reducing periodic disturbances in both directions.  
In the graph of step response 3, the output variable \(i_{r}\) for the linear PI-controller indicates equivalent reactions to each disturbance. On the other hand, the OAC-DES does not react to each disturbance in the same way, but rather changes both the shape and the magnitude of the reactions. This further supports its adaptation to disturbances. However, reactions to transients are one of the bottlenecks associated with the proposed OAC-DES, since the reference current \(i_{r}\) becomes uncertain within these regions.