# Triangular-Shaped 5-DOF Piezoelectric Robot for Optical Lens Positioning
## 4 Experimental Investigation of the Robot
The results of the investigation are given in Figure 16. It can be seen that the lowest planar motion speed was obtained while excitation signal amplitude and payload were 80 V\({}_{\text{\text{P-p}}}\) and 6.8 g, respectively. It reached 3.13 mm/s or 39.12 \(\upmu\)m/s/V\({}_{\text{\text{P-p}}}\). It can be seen that the weight of the payload affects the motion speed of the rotor. When the payload is increased up to 12.6 g, the speed reaches up to 6.01 mm/s or 75.12 \(\upmu\)m/s/V\({}_{\text{\text{P-p}}}\). When the mass of the payload is 25.1 g, the planar speed increases up to 8.73 mm/s or 109.1 \(\upmu\)m/s/V\({}_{\text{\text{P-p}}}\). This shows that planar speed increases when payload increases as well. The highest planar motion speed of 21.1 mm/s or 105.5 \(\upmu\)m/s/V\({}_{\text{\text{P-p}}}\) was obtained when a payload of 25.1 g was used and voltage of 200 V\({}_{\text{\text{P-p}}}\) was applied. The speed reached the value of 13.77 mm/s or 68.85 \(\upmu\)m/s/V\({}_{\text{\text{P-p}}}\) and 7.72 mm/s or 38.6 \(\upmu\)m/s/V\({}_{\text{\text{P-p}}}\) when payloads of 12.6 g and 6.8 g were used at the same voltage, respectively. Measurements showed that planar speed almost linearly depends on voltage. Therefore, in order to fully investigate planar motion characteristics of the robot, the same experimental studies were performed while segments L\({}_{\text{\text{\text{120 deg}}}}\) and L\({}_{\text{\text{\text{240 deg}}}}\) were driven by excitation signal. A summary of the measurement results is shown in Figure 17.  
Figure 16: Measured planar motion speed of the robot at different payloads when segment L\({}_{\text{\text{\text{deg}}}}\) is excited. The highest planar speeds generated by different piezoceramic segments have different values that depend on the payload applied to the robot. Fluctuations of speeds values, while payloads of 6.8 g, 12.6 g, and 25.1 g are applied, are around 9.58%, 2.82%, and 8.96%, respectively. Therefore, it can be found that the lowest planar speed fluctuations are obtained while a payload of 12.6 g is used. It can be assumed that a payload of 12.6 g will ensure the most even planar motion speed in different directions. On the other hand, the lowest planar speeds have significantly lower values when different payloads are applied. The difference is more than 50% compared to the highest ones. However, the difference between the lowest values also depends on payload, with values of 11.58%, 5.37%, and 8.13% while 6.8 g, 12.6 g, and 25.1 g payloads are applied, respectively. Therefore, it can be found that the most suitable payload is 12.6 g. On the other hand, planar motion speed achieved at this payload is lower by 36.41% compared to planar speed obtained while 25.1 g payload was applied. Experimental investigation of angular speeds was performed as well when segments R\({}_{\text{ddeg}}\)-R\({}_{\text{240 deg}}\) were excited by harmonic voltage. The same experimental setup was used (Figure 15). Firstly, the angular motion speed of the payload was investigated when the R\({}_{\text{ddeg}}\) segment of the piezoceramic ring was excited while segments R\({}_{\text{120 deg}}\), R\({}_{\text{240 deg}}\), and L\({}_{\text{ddeg}}\)-L\({}_{\text{240 deg}}\) were set to open-circuit condition. Excitation voltage changed in the range from 80 V\({}_{\text{P-P}}\) to 200 V\({}_{\text{P-P}}\). The measurements were made using three different payloads. Results are given in Figure 18.  
The lowest angular motion speed was obtained when the R\({}_{\text{ddeg}}\) segment was affected by an excitation voltage of 80 V\({}_{\text{P-P}}\) and payload of 6.8 g. The angular speed reached 4.27 RPM or 0.053 RPM/V\({}_{\text{P-P}}\). On the other hand, while payload values and excitation signal amplitude were 12.6 g, 25.1 g, and 80 V\({}_{\text{P-P}}\), the angular speed of the payload reached 7.56 RPM or 0.0945 RPM/V\({}_{\text{P-P}}\) and 11.03 RPM or 0.137 RPM/V\({}_{\text{P-P}}\), respectively.