# Improvement of the Sensor Capability of the NAO Robot by the Integration of a Laser Rangefinder
## 4 Discussion  
The measurements highlighted how the designed helmet with the rangefinder device can provide a wide range of accurate information about the surrounding environment, which is otherwise not retrievable with the robot's embedded sensors. At the same time, it does not significantly affect the stability of the robot when accomplishing its usual tasks. In each of the performed tests, the robot, due to the new settings described by equation (1), maintained its balance correctly and responded by executing the commands given without errors, both for the rotational movements of the head and the walking movements, maintaining a good level of balance and mobility. Due to the additional battery used as a sensor power supply, no alterations in the current power consumption from the robot's onboard battery were observed. In addition, no alterations were found concerning anomalous power consumption of the robot's servo motors, and no supply current increases were detected in any of the stressed joints. The factory provides each servo motor with a proper current sensor. Moreover, each joint presents a specified current limitation value to protect the respective motor, the electronic board, and any mechanical parts of the joint itself. Thus, if the current reaches the maximum allowed value, the PWM (pulse wide modulation) signal returned by the control loop will be modified until the value of the current falls back into the allowed range. Moreover, by using the NAO APIs, it is possible to retrieve the temperature information from each joint, actuator, CPU, and battery and store the value in the proper corresponding ALMemory key. If at least one of the items presents a non-null status, a _HotDeviceDetected()_ event is triggered. In particular, the NAO software provides an alert code to monitor the temperature status for each device, from 0 (meaning a normal temperature) to 3 (meaning that the joints are critically hot). A non-null value of this code implies an automatic correction of the robot's stiffness, which will be lowered in the case of a status equal to three, until the zero value is reached. Once these embedded controls were activated within the tested behaviors, no malfunction warning regarding an anomalous current nor an increase in the temperature of the joints, actuators, CPU, or battery was reported during any of the tests. In addition, no robot protection system operation occurred regarding the robot's stiffness, which was maintained during the tests. The device consumption and the temperatures inside the machine remained stable. Due to the excellent balance and appropriate weight of the proposed system, even the movements of the devices related to the _HeadYaw_, the only degree of freedom allowed for the robot's head, were smooth and not slowed down. This also affects the movements of the robot, which, as long as the walking speed is not increased, but maintained as recommended, remained normal and stable. This is the case in indoor environments (where the tests were carried out), where the factory characteristics of the NAO allow it to operate in complete safety. Since this is a simple characterization of the system, we have no speed constraint, so a setup was chosen in which the robot moves, stops, and acquires laser data and then moves again. The precise adjusting mechanism provided by the helmet allows for the leveling of the rangefinder sensor. Thus, when the helmet is worn and the sensor is adequately oriented, the robot's head must no longer be pitch rotated, while yaw rotation is freely allowed. This setup, combined with the firmness of the helmet lock, ensures parallelism with the floor. The new robot-sensor system has been verified to study the behavior of rangefinder lasers within a living environment. In particular, the rangefinder device has been tested for the designed power supply and laser control through the software functions developed by the robot manufacturers. Moreover, by test #1, the reliability of the sonar and laser rangefinder measures were studied.