Controlling Unmanned Ground Vehicle Via 4 Channel Remote Control

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Energy Procedia 68 ( 2015 ) 381 – 388

2nd International Conference on Sustainable Energy Engineering and Application, ICSEEA 2014 Controlling unmanned ground vehicle via 4 channel remote control

Hendri Maja Saputraa,* and Midriem Mirdaniesa

aResearch Centre for Electrical Power and Mechatronics - Indonesian Institute of Sciences Komplek LIPI, Building 20, Jl. Cisitu, No. 21/ 154D, Bandung 40135, Indonesia

Abstract

A four-channel Remote Control (RC) which is used to model aircraft can be modified to control multiple DC motors and other devices on Unmanned Guided Vehicle (UGV). Remote control used in this paper is HobbyKing brand that works at frequency 2.4 GHz. Eight bit microcontroller module is added to give command reference value to the transmitter module of the remote control that will be sent to the receiver module. On the transceiver module, two channels are used as an identifier (address and command), while the other two channels are used for transfer hexadecimal data (0-F). A PWM data received by the receiver module is read by the microcontroller module using the counter method utilizing the 16-bit timer. The data is sent to the DAC module to be converted into analogue voltage 0-5 Volt which is then manipulated by a signal amplifier to moving the DC motors or control various other devices on the UGV. The algorithm is implemented into the microcontroller module using the C programming language. Test results show that the counter method can be used for reading a PWM signal with absolute error less than 1%, so that the UGV can be controlled well via remote control.

© 20152015 TheThe Authors. Authors. Published Published by Elsevierby Elsevier Ltd. B.V.This is an open access article under the CC BY-NC-ND license Peer(http://creativecommons.org/licenses/by-nc-nd/4.0/-review under responsibility of Scientific Committee). of ICSEEA 2014. Peer-review under responsibility of Scientific Committee of ICSEEA 2014 Keywords: remote control; microcontroller; DC motors; C language; UGV

1. Introduction

Transmitter-receiver (transceiver) module is ready to use has been sold in the market; one of them is a remote control that is commonly used in model aircraft consisting of four to six channels. Remote control (RC) is widely implemented for various purposes, either to operate the vehicle model or to control a variety of specific devices.

* Corresponding author. Tel.: +62-813-8100-6059; fax: +62-22-250-4773. E-mail address:[email protected]

1876-6102 © 2015 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of Scientific Committee of ICSEEA 2014 doi: 10.1016/j.egypro.2015.03.269 382 Hendri Maja Saputra and Midriem Mirdanies / Energy Procedia 68 ( 2015 ) 381 – 388

Remote control can be used to control Unmanned Aircraft Systems (UASs), Unmanned Ground Vehicles (UGVs), and Unmanned Maritime Systems (UMSs) [1]. Fig. 1 is an example of vehicle that is controlled by remote control [2-4]. UGV generally use four to eight independent rotating wheels added with other devices such as pan-tilt camera mechanism, manipulator, coupling tracks, and switch modes.

(a) (b)

Fig. 1. Remote-controlled vehicle; (a) excavator, (b) unmanned ground vehicle.

In Hendrik paper [5], the remote control is used to control the omni directional robot. Six channel data received by the receiver module is converted by the microcontroller into 4 bits data to drive a DC motor in order to move clockwise (CW) or counter clockwise (CCW). The remote control can be used to drive only four DC motors. At the modifications made of Samosir [6], the transceiver module can be used to transmit the numbers 0 to 9. Input from the keypad is read by the microcontroller and then sent through a transmitter module in the form of binary code. The data received by the receiver module is shown through seven segments after reconverted by the microcontroller. Remote-controlled car used is consists of four bits (forward-backward and left-right) which has a high '1' and low '0' value. Some of the data is not sent, this is because the forward-backward cannot be worth the high ("1") simultaneously as well as right-left. On the remote control that has a PWM output, signal identification method is very important. In PWM signal identification method discussed by Mahendra [7], 16-bit timer on the microcontroller is used as an internal counter to calculate the pulse width of the PWM with a resolution of 1/crystal frequency. This paper describes how to modify the remote control in order to dynamically function as digital data communication. Data input can be an array of letters or numbers. The data is sent in the form of hexadecimal code [8]. The identification of the PWM signals from the receiver module using the counter method. The eight-bit microcontroller module (e.g. ATMega8535/16/32) is used to manipulate the data to be transmitted or received. Programs created using the C language. The modification described in this paper is implemented on the remote control to control UGV that can simultaneously drive multiple DC motors or to control other devices.

2. Remote control connections

2.1. The current used design

The remote control on the market is very practical to use and basically can be directly used without modification. The connections are commonly used on the remote control is shown by Fig. 2(a). However, the implementation of servo motors as actuators for devices that require high speed or greater torque is not enough. It requires modifications to the receiver output module by adding additional modules such as a microcontroller (see Fig. 2(b)).

Hendri Maja Saputra and Midriem Mirdanies / Energy Procedia 68 ( 2015 ) 381 – 388 383

4-Channel 4-Channel Transm itter Module Receiver Module

Data Data

A A Servo Motor 1 B B Joystick & Servo Motor 2 C C Button Servo Motor 3 D D Servo Motor 4

(a)

4-Channel 4-Channel Transm itter Module Receiver Module

Data Data

A A B B Microcontroller Joystick & Driver 1-4 DC Motor 1-4 Button C C Module D D

(b)

Fig. 2. General connections for controlling 4 motor: (a) without microcontroller; (b) with microcontroller.

In Fig. 2 it can be seen that the general connections for controlling four motors via remote control can be with or without a microcontroller. Connection is shown in Fig. 2(a) can actually be found in the model of aircraft (airplane, helicopter, etc.) that uses servo motors as actuators. In Fig. 2(b), microcontroller added to process the signal coming from the receiver module in order to drive various types of DC motors.

2.2. The proposed design

Configuration in Fig. 2 has weaknesses, i.e. (1) data communication only in the form of analog voltage input and PWM output; and (2) the maximum motor that can be used is only four motors because it consists of four channels. To make the remote control to send data more dynamic, it can be used as the connection diagram shown by Fig. 3. In the Fig. 3, the data sent can be an array of letters or numbers depending on the purpose. A transmitter and receiver module functioned only as a sender of data in hexadecimal code [8]. Two channels are used as identifier of the slot array (address) and delivery orders (command), while the other two channels are used as data. An analogue signal 0-5 V on each channel which functions as the input to the transmitter module is partitioned into 16 section, it is determined to ensure the precision and accuracy of the data. The task of each channel can be seen in Fig. 4.

384 Hendri Maja Saputra and Midriem Mirdanies / Energy Procedia 68 ( 2015 ) 381 – 388

4-Channel 4-Channel Transm itter Module Receiver Module Driver 1 Motor 1

Data Data

A A Driver 2 Motor 2 Control panel B B (joystick, Microcontroller DAC Microcontroller DAC Signal button, Module module C C Module module Amplifier keypad, etc.) D D

Driver N Motor N

Fig. 3. Proposed connection for controlling UGV.

Address Analogue 0-5V PWM 1 Address

Command Analogue 0-5V 4-Channel 4-Channel PWM 2 Command Transmitter Receiver Analogue 0-5V PWM 3 Data 1 Module Module Data 1

Data 2 Analogue 0-5V PWM 4 Data 2

Fig. 4. Distribution of duties of each channel.

3. Experimental set-up

Experiments have been done to determine the performance of the remote control (transceiver module). The device used in this experiment including control panel, microcontroller module, DAC module, transceiver module, and signal amplifiers. A microcontroller eight-bit with 16 MHz clock (ATMega8535/16/32) is used for processing the data from the control panel. Microcontroller module is connected to the DAC module eight-bit to send the analogue (0-5 Volt) data to four channel transmitter module on the remote control. The remote control used is HobbyKing [9] using 2.4 GHz frequency. Remote control consists of HK-T4a Mode 2 four channel transmitter module and HK- TR6A six channel receiver module. At the receiver module, analogue signal 0-5 V is represented by a high pulse width of the PWM signal with a frequency of 50 Hz. The PWM signal is identified by the microcontroller module using the counter method. A counter data is then processed as the reference data to be sent to the DAC module to generate analogue signal 0-5 V. The identification algorithm on the PWM signal from the receiver module using counter methods can be seen in Fig. 5. In the early stages of the experiment, the data counter is sent to the computer using the RS232 connector that can be read via the computer terminal.

Hendri Maja Saputra and Midriem Mirdanies / Energy Procedia 68 ( 2015 ) 381 – 388 385

Start

D ata initialization: - S et Timer 1 clock = 0.0625 us - S et PO R T X = input loop

true Is Input = high?

false S et timer 1 = on

S et timer 1 = off

S et counter = TC NT1

Stop

Fig. 5. Signal identification using counter method.

Algorithm in Fig. 5 is implemented using the C programming language. Timer 1 is used to counter high pulse received. The results of the counter after being processed are then put into the equation as a comparison between the value that will be used as a reference and a signal to be sent to the DAC module using the straight-line (interpolation) equation.

yy 1 xx 1 (1) yy 12 xx 12 where y is the data that will be sent to the DAC (8-bit or 0-255), y2 is the maximum value of the signal (255), y1 is the minimum value of the signal (0), x is the desired reference value, x2 is the maximum reference values, and x1 is the minimum reference values. Analogue signals from the DAC module reprocessed by the amplifier signal into the desired data. The data is eventually sent to the driver to rotate the DC motor or other devices. Experimental set-up can be seen in Fig. 6.

Control 4-channel 4-channel Oscilloscope panel Transmitter module Reciever module

microcontroller_1 DAC_1 microcontroller_2 DAC_2 Signal module module module module Amplifier

Fig. 6. Experimental set-up. 386 Hendri Maja Saputra and Midriem Mirdanies / Energy Procedia 68 ( 2015 ) 381 – 388

4. Result and discussion

Each channel of the four channel transceiver modules tested for sending and receiving data hexadecimal (0 -F). The test results can be seen in Table 1. Input data with decimal value of 8 bits (0-255) is entered from microcontroller to the DAC module which will convert into analogue data (0-5 V) to the transmitter module. PWM data which received at the receiver module is read by the microcontroller using the counter method and oscilloscope as a comparison.

Table 1. Experimental results of the transceiver module.

No Data Decimal DAC Channel A Channel B Channel C Channel D 8 bit (Volt) + width* Counter** Abs. + width* Counter** Abs. + width* Counter** Abs. + width* Counter** Abs. (μs) (μs) Error (μs) (μs) Error (μs) (μs) Error (μs) (μs) Error

1 0 0 0,02 880,0 876,3 0,4% 880,0 876,7 0,4% 960,0 961,9 0,2% 870,1 876,2 0,7%

2 1 16 0,34 960,2 950,9 0,9% 950,0 946,4 0,4% 1020,0 1017,8 0,2% 950,0 951,0 0,1%

3 2 32 0,68 1040,0 1038,4 0,2% 1040,0 1035,1 0,5% 1090,0 1088,6 0,1% 1040,0 1034,6 0,5%

4 3 48 1,01 1120,0 1124,2 0,4% 1120,0 1119,7 0,0% 1160,0 1157,1 0,3% 1120,0 1124,5 0,4%

5 4 64 1,36 1220,0 1214,0 0,5% 1210,0 1209,5 0,0% 1230,0 1228,2 0,1% 1210,0 1211,8 0,1%

6 5 80 1,69 1300,0 1297,6 0,2% 1300,0 1298,1 0,1% 1300,0 1298,8 0,1% 1300,0 1297,9 0,2%

7 6 96 2,02 1380,0 1382,3 0,2% 1380,0 1382,6 0,2% 1370,0 1366,5 0,3% 1380,0 1382,4 0,2%

8 7 112 2,37 1480,0 1477,1 0,2% 1470,0 1472,4 0,2% 1440,0 1439,4 0,0% 1480,0 1477,0 0,2%

9 8 128 2,71 1560,0 1574,5 0,9% 1560,0 1560,9 0,1% 1510,0 1510,0 0,0% 1560,0 1560,9 0,1%

10 9 143 3,02 1640,0 1640,7 0,0% 1640,0 1640,6 0,0% 1570,0 1572,4 0,2% 1640,0 1640,4 0,0%

11 A 159 3,36 1730,0 1719,6 0,6% 1720,0 1724,1 0,2% 1640,0 1640,7 0,0% 1720,0 1725,6 0,3%

12 B 175 3,70 1820,0 1813,9 0,3% 1820,0 1814,4 0,3% 1720,0 1712,6 0,4% 1820,0 1814,2 0,3%

13 C 191 4,05 1900,0 1909,2 0,5% 1900,0 1903,8 0,2% 1790,0 1784,5 0,3% 1910,0 1904,0 0,3%

14 D 207 4,38 2000,0 1988,3 0,6% 1990,0 1988,7 0,1% 1850,0 1851,2 0,1% 1990,0 1988,7 0,1%

15 E 223 4,71 2060,0 2072,2 0,6% 2079,0 2072,4 0,3% 1920,0 1919,1 0,0% 2070,0 2072,4 0,1%

16 F 239 4,95 2120,0 2132,1 0,6% 2130,0 2132,3 0,1% 1970,0 1966,9 0,2% 2130,0 2132,0 0,1%

power off 0,0 0,0 0,0% 0,0 0,0 0,0% 0,0 0,0 0,0% 1500,0 1498,6 0,1%

free voltage 880,1 876,3 0,4% 880,0 876,2 0,4% 960,0 962,3 0,2% 880,0 876,1 0,4% Note: * is using Oscilloscope and ** is using microcontroller

Table 1 shows that the high pulse width (+ width) on each channel are different, the data is the value of a counter that has been converted into a high pulse width of the PWM signal. This is done so that the value of the counter can be compared with the value of the oscilloscope. Intervals of high pulse width of each channel are 876.3 μs - 2132.1 μs for A channel, 876.7 μs - 2132.3 μs for B channel, 961.9 μs - 1966.9 μs for C channel, and 876.2 μs - 2132.0 μs for D channel. Absolute error using the counter method is less than 1% (see Fig 7).

Hendri Maja Saputra and Midriem Mirdanies / Energy Procedia 68 ( 2015 ) 381 – 388 387

1,2%

1,0%

0,8%

0,6%

0,4% Absolute error 0,2%

0,0% 0 1 2 3 4 5 6 7 8 9 A B C D E F Data

Channel A Channel B Channel C Channel D

Fig. 7. Absolute error comparision.

Implementation of the remote control for controlling a UGV that has been done, the results of experiments counters are used as the basis for data communication algorithm using C language that is downloaded to the microcontroller. Remote-controlled UGV is a bomb disposal mobile robot (Morolipi V1) which created by Research Centre for Electrical Power and Mechatronics - Indonesian Institute of Sciences (Puslit Telimek–LIPI) [10]. The remote control is used to control two independent wheels, 5-DOF arm (manipulator), and the end-effectors as cable cutting tools. Fig. 8 shows the unmanned ground vehicle (UGV) that is controlled by a remote control.

Data communication

Fig. 8. UGV is controlled via remote control.

UGV can move forward-backward and have a good maneuver controlled by the remote control. Manipulator (arm 5-DOF) can be controlled to create certain angles and end-effectors can work well for cutting cable.

5. Conclusion

Based on the results of research, it can be seen that the remote control of aircraft model can be implemented to drive DC motors by using the current used diagram, while to create a more dynamic data communication to transmit the arrangement of letters and numbers can be used the proposed diagram in this paper. Counter method is implemented using microcontroller module to read the data communication via the transceiver module with absolute 388 Hendri Maja Saputra and Midriem Mirdanies / Energy Procedia 68 ( 2015 ) 381 – 388

errorless than 1%. Data communication experiments described in the paper is only qualitative (test function) to control the UGV, so that further research needs quantitative experiment to determine how accurate and precise data sent in the control of the UGV.

Acknowledgements

Authors would like to thank to Prof. Dr.Eng. Estiko Rijanto which provide guidance for this research and all coleague in mechatronics division on Research Center for Electrical Power and Mechatronics – Indonesian Institute of Sciences who have helped in the robotic defense research.

References

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