Analyzing the control network with telemetry activated for the whole team, six robots, was crucial to confirm the ability to use telemetry at the games. The results, shown at Figure 23, had a higher gap between the delivery delay at a network with and without telemetry when compared with the tests realized with one robot, shown at Table 6. The increased gap shows a delay coming from the base station higher load of messages because now it needs to transmit six packets of control and six of telemetry.
Figure 23: Delivery time of Ethernet base station packets with different telemetry sampling time at 6 robots control network.
Although, the delivery time of the control network increased from 4308us, when it is without telemetry, to 4672us, when it is with a 50ms sampling telemetry in each of the six robots.
Now, with telemetry, it is possible to monitor the robot’s status, like the angular speed of each wheel on time, represented at Figure 24.
Figure 24: Angular speed on time of each wheel is the robot, monitored by the developed telemetry network.
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5
CONCLUSION
In the context of houses, Industry 4.0, Internet of Things (IoT), and robotics, wireless communication is essential. It can share information across devices, give functionalities, or, like the soccer robots at SSL, may control mobile robots movements. Therefore, technologies and systems should be developed and integrated to fill the necessity present at each application developed. Although there are no perfect modules or technologies, there are options to find a balance that maximizes the desired efficiency at each application.
At robotics systems, the challenge is higher. Besides the perception and cognition, there are tasks like wireless communication, which is fundamental to accomplish real-time motion control at the robots. At communication wireless, this work proposed architecture of the base station that efficiently controls the RobôCIn’s SSL robots. The work reviewed modules and interfaces to reach a system architecture that, when analyzed in a real robotics soccer environment, fulfill the requirements.
The results show a system that reached 4.33 milliseconds of latency at robot when it is on a six robot network. Only the Ethernet base station proposed reaches that latency, and it is almost three times faster than the serial base station. What endorsed the benefits of using a faster and updated interface of communication, even between the computer and base station.
Even though the number of robots in the network increases the latency proportionally because the station should divide its throughput to more robots, continuously emitting messages at one, two, and six robots’ networks, showed consistent message reception and consistent latency. Even when measuring in two different robots and also at different distances from the base station, the proposed network delivered at least 230 messages per second, faster enough to SSL competition, that usually uses 60 fps cameras.
When developed the telemetry at the robot and base station, the delivery time of the packets in the six robots’ network, with 50ms of telemetry sampling enabled, reached 4.39 milliseconds. This latency permits the delivery of 227 messages per second per robot. Moreover, although 4.39 milliseconds represents an increased of 1,39% compared with the network without telemetry, the telemetry network brings the benefit of monitoring each robot and should avoid failures and increase precision.
Results reliability working with wireless networks is trick, because many phenomena
may occur and noise the results. So, every test made measured 30 receptions intervals, and each interval is the average time between the delivery of 500 packets. This amount of measures in a real environment statistically endorse the real-time network efficiency, which also has telemetry ability at each robot.
With the results shown at this work, the RobôCIn team already used the proposed network at the Latin American Robotics Competition (LARC) - 2019. Without any failure or delayed control, it was a pleasure to see the team using the proposed network to control and monitor its robots. At the competition, RobôCIn did not play any match with malfunction robots due to telemetry. The robot status, received at the computer, enabled the team prevent robot’s failures before and during the game. This work also brought to RobôCIn a quickly maintenance and consistency in the championship.
After the RobôCIn’s experience, the proposed network proved its ability to support multiple devices in real-time and is suitable for IoT and Industry 4.0 applications.
For future work, a study of new modules and its technologies should be considered to speed up the network data exchange. Moreover, future work may find alternatives to reduce the delivery time impact when adding more robots to the network. Changes like the embedded boards or different interfaces may increase the network cost but may reduce the delivery of the whole system. Together with bets specifications, future work may develop an automatic time analyzes that search the optimal parameters using the hardware in the loop.
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