# Remote Control Device to Drive the Arm Gestures of an Assistant Humanoid Robot
## 5 Experimental Evaluation
### Measurement of the Structural Delay of the Imitation Model  
The structural delay is the time required by the mobile robot to replicate the position of the joints submitted by the remote controller device. The structural delay depends on the closed-loop control applied to drive the arms of the mobile robot and does not depend on the communication network.  
Figure 8: Structure of the imitation model: the operator moves the arms of the remote control device; the positions of the joints are measured, mapped, and sent to the APR-02 mobile robot.  
Figures 10 and 11 show the evolution over time of the target joint angles of the right and left arms of the mobile robot (solid lines) during a dynamic gesticulation, and also the real evolution of the joint angles of the robot (dotted lines). The joints are numbered as in Figure 2. In all experiments, the starting position of the arms of the remote controller device and the humanoid robot corresponds to a resting position in which the arms are extended and hanging. This initial position is called the neutral position in this work.  
Figure 10: Evolution of the joint angles when the arms of the mobile robot perform four circular rewards trajectories in the air: (**a**) right arm; (**b**) left arm. Solid lines depict the joint position received by the mobile robot, and dotted lines depict the real evolution of the joints of the robot.  
Figure 9: Evolution of the joint angles measured by the remote control device when the arms perform three circular inwards trajectories in the air: (**a**) right arm; (**b**) left arm.  
In the gesturing example represented in Figure 10, the arms of the robot perform four inward circles in the air, with the arms raised (almost parallel to the ground) and the elbow slightly bent. The dynamic joint evolution generated by this circular gesture is difficult to imitate because the circular profile is always accelerating and decelerating the motors of the robot joints. Similarly, in the gesturing example represented in Figure 11, the arms of the robot perform three lateral displacements in the air: starting from the neutral position, moving upwards and diagonally to the left, and then horizontally to the right, returning to the left and repeating to the right.  
The analysis of the information displayed in Figures 10 and 11 shows that the joint positions received by the robot are the same as those submitted by the remote control device, without discontinuities or jumps. Additionally, the comparison of the evolution of the target joint (solid lines) and the real robot joint (dotted lines) reveals that the structural delay of the humanoid robot replicating arm gestures is from 120 to 540 ms, depending on the joint and movement performed, with an average structural delay of 274 ms.  
The arms of the robot are programmed to reach all target joint positions, but the structural delay may reduce the amplitude of the motion in case of changing the direction of the motion. In the case of the periodic gestures shown in Figures 10 and 11, this effect reduces the amplitude of the joint evolution performed by the robot with respect to the target joint evolution.