UAV telemetry communications using ZigBee protocol

Wireless communication has been widely used in various fields or disciplines such as agriculture, health, engineering, military, and aerospace so as to support the work in that field. The communication technology is typically used for controlling devices and data monitoring. One development of wireless communication is the widely used telemetry system used to reach areas that cannot be reached by humans using UAV (Unmanned Aerial Vehicle) or unmanned aircraft. In this paper we discuss the design of telemetry system in UAV using ZigBee protocol. From the test obtained the system can work well with visualization displays without pause is 20 data per second with a maximum data length of 120 characters.


Materials and Method
In this study, the functionality of the system created focused on the functionality of the data telemetry system. To support maximum telemetry system UAV data function required RF devices, long range antenna and GCS. The RF device used is the XBee module (ZigBee) and the antenna used is the 2.4 GHz yagi antenna. While the required GCS device has the following specifications:  Visual instrument panel featuring basic flight instruments such as altitude indicator, airspeed indicator, artificial horizon, vertical speed indicator (climb speed), attitude indicator / artificial horizon, indicator Direction (compass / heading indicator), and GPS lock status.  Control engine on UAV (ON, FIRE, STOP / PARACHUTE).
The GCS system is made up of two major parts of hardware and software. GCS hardware part serves to capture data sent by UAV via RF transmitter (ZigBee) and convert to form data that can be processed by software. In addition to processing data obtained telemetry to visualize, the software also serves to store and provide feedback in the form of commands such as turning on, off, and activate the data transmission. The design scheme of this system can be seen in figure 1.

XBee Pro
XBee Pro is a module that allows Arduino Uno to communicate wirelessly using ZigBee protocol. ZigBee operates using on IEEE 802.15.4 specifications operating at 2.4 GHz, 900 and 868 MHz frequencies. XBee Pro can be used instead of serial cable. XBee Pro is expected to reduce costs and become low-power connectivity for equipment that requires batteries to live for several months to several years, but does not require high data transfer rates. XBee Pro enables wireless communications within reach of up to 100 meters indoor and 1500 meters outdoor. In this we use the XBee S2Pro radio module as shown in figure 2. Remote monitoring and measurement systems consist of two of the same XBee Pro modules previously programmed as a receiver-transmitter and transmitters [13]. There are several topology forms commonly used, among others, mesh topology, peer, star, and cluster trees. Topology on XBee Pro network Topology pair is a simple network using only two XBee or node. One node must be the coordinator so that the network can be established. And the other is configured as a router or end device. We use the XCTU application to setup both modules.

Sensor IMU 10 DOF
The IMF sensor module (inertial measurement unit) 10 DOF gy-80 sensor consists of 4 sensors namely, 3 Gyro axis, 3 Axis Accelerometer, 3 Axis Magnetometer, and barometer as shown in figure  3. All sensors communicate using I2C bus protocol so it takes 4 Paths is: 1. GND -Ground 2. 2Supply voltage or source voltage +3.5 V to +5 V. 3. 3SCL for I2C clock 4. SDA for I2C data.  To meet the needs in accordance with the needs, the software interface designed to be made into several parts such as figure 4. Speed graph of time will display acceleration UAV to monitor the stability of flying. The time height graph is designed to show the vertical speed of the object. Engine is a feature that functions as ON, Fire, Stop / Parachute. While data sent sensors and GPS will be displayed as well.
As planned, software that is also a graphical user interface with UAV is developed using C # language in Microsoft Visual Studio 2010 Ultimate software licensed for free from MSDNAA In addition to being displayed visually through the visual instrument panel, flight parameter data obtained from IMU10ODF is also displayed numerically. As shown in the figure 4 is a display of IMU10DOF data located under the visual instrument panel

Results and Discussions
The functional test results of all instruments and visualizations on the GCS interface can respond well to the entire range of data provided through the serial port. Maximum data rate that can be processed so that displaying visualization without pause is 20 data per second with maximum data length of 120 characters. The results of the data responses obtained can be seen in Table 1. When testing is obtained the calculation of the average number of incoming data every second is 8 data with a data width of 90-120 characters. For data variation is given treatment on sensors in IMU10DOF module to see the response. Variations in attitude data variables (yaw pitch and roll) are obtained by changing the position of the IMU Razor 9 DOF sensor connected to IMU10DOF.

Conclusion
From the tests performed, the system can run as expected. GCS can communicate with UAV by receiving data obtained from IMU10DOF sensors. The system can work by displaying data on the GCS interface with 20 data per second with a maximum data length of 120 characters. From these results it can be concluded that the ZigBee protocol can be used for telemetry in the UAV.