# Uniform vs. Lognormal Kinematics in Robots: Perceptual Preferences for Robotic Movements
## 5 Tests Performed
### Test 4  
In this test, an ABB robot was used to verify the influence of the movement type on collaborative tasks. Previous tests were based on showing participants videos and analyzing whether they were able to differentiate human from robotic movement.  
The aim of this test was to have the robot perform movements at safe speeds with a uniform and robotic speed profile. The participants were asked to touch the end of the robot with their index finger and to follow its movements, as shown in Figure 14. After this, they were asked which movements felt more comfortable. The tests were completed on-site by the participants with the procedure being as follows:  
Figure 14: Snapshot of test 4.  
Figure 13: Snapshot of test 3.  
The test has two parts:  
\begin{tabular}{l l} Part 1: & The robot executed the Figure six times, the first three one way, followed by a 1-second pause and then three another way. The participants were asked to identify the one that was easiest to follow and also rate them. The rating was: 1 very unfriendly and 5 very friendly. \\ Part 2: & The same as above, but with a bigger figure. \\ \end{tabular}  
The form given to the participants for each figure was:  
_The robot will perform a figure six times in a row, three with a speed profile (movement 1) and three with the other speed profile (movement 2). You must touch the robot's end with your finger and follow its movement. After that, answer these questions._  
\(Q1\)_: Which of the robot movements did you find most friendly? Check the option._  
\(\Box\) _Movement 1._  
\(\Box\) _Movement 2._  
\(\Box\) _Both equal._  
\(Q2\)_: With a scale from 1 to 5, assess each of the previous movements, being 1 (very unfriendly) and 5 (very friendly)._  
_Movement 1:___  
_Movement 2:___  
The figures drawn by the robot are those shown in Figure 7. The four on the left were shown randomly in the first part of the experiment and the one on the left was shown to all participants in the second part of the experiment. The choice of whether the first profile displayed was lognormal or at constant speed was also random.  
This experiment was carried out by 118 participants, of whom 37% were women and 63% men, 31% had a low knowledge of robotics, 60% a medium knowledge and 9% a high knowledge. Regarding the age distribution, 53% were under 30, 13% between 31 and 50 and 51% were over 51. As in previous tests, no differences were observed related to the different groups.  
The results obtained in the first part of the test showed that 42% of the participants preferred a lognormal movement, 44% preferred a uniform movement and 14% had an equal preference for both.  
For the movements shown in second place, it was observed that if the last movement shown was the lognormal, the participants preferred it by 48% and trapezoidal by 36%. However, if the second shown was the trapezoidal, they preferred the lognormal by 36% and the trapezoidal by 54%. This behavior was observed in all tests in which participants had to choose between two options. Because the order of the movements was chosen randomly, this factor was not considered and only the global data were shown.  
The results obtained in the second part of the test showed that 44% of the participants preferred the lognormal movement, 33% uniform and 22% preferred them equally.  
The subjects were also asked to value each of the movements. A summary of the results, including the mean and the standard deviation of all ratings for the two figures and with both speed profiles, can be seen in Table 2.  
\begin{table}
\begin{tabular}{l c c c c} \hline \hline  & \multicolumn{2}{c}{**Small Figures**} & \multicolumn{2}{c}{**Big Figure**} \\ \hline  & **Lognormal** & **Trapezoidal** & **Lognormal** & **Trapezoidal** \\ \hline Mean & 3.35 & 3.25 & 3.54 & 3.57 \\ Std. Dev & 1.10 & 1.16 & 1.21 & 1.18 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Movement evaluation (1 unfriendly-5 very friendly).