# A Gesture-Based Teleoperation System for Compliant Robot Motion
## 4 Experiments
### Case Study of Peg-In-Hole Process
#### 4.2.1 Results  
It takes less than an hour to train two operators to use the gesture-based system, including how to make the right gestures, how to switch modes and how to accurately control the robot movement. And it requires more than 10 min for the operator to complete an assembly task at the beginning of the training. After several training sessions, the assembly task can be completed in 1.5 min. Although the speeds were different, all tasks were successfully accomplished. Ten sets of experiments were done by two operators. As shown in Figure 11, the average time for grabbing the axis was 62.72 s and its standard deviation was 10.51 s, the average time for moving the axis was 36.19 s and its standard deviation was 8.41 s; and the time for putting the peg in the hole was 39.74 s and its standard deviation was 9.48 s. Because of the difference in physical structure of human and robot, it was a bit slower than manual operation. After learning the tasks through GMM/GMR method [34], the robot can quickly reproduce this task. One of the recorded robot motions is shown in Figure 12; the small green circles stand for the robot position in free space, while the big red circles are positions where contact force was detected. Figure 11: The portion time for each part of the assembly process. The average time for grabbing the axis was 62.72 s and its standard deviation was 10.51 s; the average time for moving the axis was 36.19 s and its standard deviation was 8.41 s; and the time for putting the peg in the hole was 39.74 s and its standard deviation was 9.48 s.  
Figure 12a shows a full robot motion from start position to stop position. Initially, it was in coarse motion mode. Because of the unsteadiness of human motion, the robot motion also had a significant variation. This variation is not a serious problem because it can be smoothed in the learning from the demonstration process by averaging techniques. When the robot was close to the peg, it was switched into fine motion mode. The step size reduced, and the points were dense compared to coarse motion mode. After a series of adjustments, the robot moved above the peg, and the single-axis mode was used. The robot moved along the vertical direction until the contact force was detected. After closing the gripper, the robot started to lift the peg out of the container. Because the gripper-peg combination was longer than the gripper, the lift attitude was higher than the previous gripping process. Once the peg was out of the container, it was switched into coarse motion mode again. The peg was swiftly moved above the hole. After adjusting the position in fine mode, the peg was driving downward in single axis mode until contact occurred. This process can be clearly seen in Figure 12b. The dense red circles are points in the hole searching process when the robot movds along a horizontal search pattern while keeping contact with the hole's surface. Finally, once the contact force vanished, it was switched into the fine motion mode and single-axis mode to insert the peg into the hole and release the peg then. Finally, the gripper was lifted with coarse motion mode and returned to the stop position. Figure 13a shows the used gestures. The values represent specific actions, as shown in Table 1. It can be seen that coarse mode, fine mode and single-axis mode are frequently used to adapt the assembly skills and sensor ranges. Gripper open/close gestures were used twice to pick and place the peg. Figure 13b shows the forces measured during the teleoperation. The compliant assembly skills can be located on this figure. The contact force in the process of moving the robot gripper downward appears at around step 450; the search force in the process searching hole appears at around step 950. Owing to human uncertainties, the locating errors and the friction between peg-container and peg-hole generated additional forces. The pulse drag force (positive) at step 280 and 500 was caused by those frictions when lifting motion happens, and multiple demonstrations can eliminate this.