4 PERFORMANCE ASSESSMENTS

The response time is one of the most important factors to make the system specifications. It is also a factor for the system assessment. In this paper, there are 3 types of response time to be measured with possible different number of DTCs in communication. They are the response time of communication for CAN, for GPRS, and for the integrated system.

4.1 The response time measurement of CAN

Figure 6 shows the conditions of the response tine measurements for CAN. They are about 756 ȝs, 903 ȝs, 1032 ȝs, and 1176 ȝs for 1, 2, 3, and 4 DTCs with direct transmissions, respectively. They are the average values The International Conference on Electrical Engineering 2008

for successive 10000 transmissions with data lengths of 2 bytes, 4 bytes, 6 bytes, and 8 bytes in Data Field of Data Frame in CAN. The response time measurements for CAN can be referred to [25] for details.

Figure 5. The tracks of the vehicle.

Figure 6. The response time measurements of CAN.

4.2 The response time measurement of GPRS

The response time of GPRS is defined as the time interval between a packet transmitted from GPRS module to the server system with a specified IP in internet and the signal which is transmitted from this server system received by GPRS module. Figure 7 depicts the architecture of the response time measurements of GPRS. The values of response time measured are the average of successive 500 times for transmission and receiving. There are four timeframes measured in this paper. They are morning (08:30~09:30), noontime (11:30~12:30), evening (17:00~18:00), and midnight (23:30~00:30). Table 1 and Figure 8 list and show the measured values of the response time of GPRS with different number of DTCs and timeframes, respectively.

Figure 7. The architecture of the response time measurements of GPRS.

4.3 The response time measurement of the integrated system

The response time of the integrated system is the time

interval between the time when CAN Node 1 starts to transmit DTCs to CAN Node 2 which sends the message to the server system via GPRS module and the time when CAN Node 1 receives the signal of completion from CAN Node 2 after CAN Node 2 receives the signal from the server system via GPRS module. The measurements are similar to those of GPRS. They also include four timeframes with different number of DCTs. Table 2 is the measured values of the response time. In addition, Figure 9 sketches these measured values.

Table 1. The response time of GPRS system.

Unit: sec

0.80 0.90 1.00 1.10 1.20 1.30 1.40

1 2 3 4 5 6 7 8 9

number of DTCs

s

Morning Noon time Evening Midnight

Figure 8. The response time of GPRS.

It takes short time for the communication in CAN compared with the integrated system, i.e., the communication in CAN is not crucial for the efficiency of the integrated system.

The decisive factor is the transmission between GPRS and the server system. Figures 8 and 9 show that the response time at midnight is better than that in noontime since the GPRS and internet systems are busier in noontime than other timeframes. Nevertheless, the integrated system has to work even the busiest hour. The infrastructure of GPRS systems is very well in Taiwan and the measured data are reliable. Therefore, the system engineers can take account of these data when they design such proximate systems.

The number of DTCs is also a factor that affects the communication efficiency since it theoretically takes more 1.8% (|2/112) time for one more number of DTCs between CAN Node 2 and GPRS module. It is suggested that the DTCs may append to one of the vehicle information packets transmitted by GPRS. The DTCs can be arranged sequentially in a packet and this will further the communication efficiency.

July 6-10, 2008, OKINAWA, JAPAN

5

Table 2. The response time of the integrated system.

Unit: sec

Figure 9. The response time of integrated system.

5 CONCLUSIONS

This paper presents an application of the OBD-II system.

The service quality and efficiency of a service center will be raised due to the prompt acquisition of the DTCs from ODB-II. The integrated system of the function prototype is established. CAN system provides the medium to access the vehicle information including the DTCs data. GPRS module is adopted for the mobile communication. It reports not only the vehicle information but also the DTCs data via internet. Therefore, the service center will acquire all the necessary information of vehicles in time.

The response time of CAN, GPRS, and the integrated system is crucial and measured in this study. The results show that the critical factor of transmissions for the integrated system is the response time of GPRS. It depends on the bandwidth of GPRS and internet. For instance, the maximal response time of GPRS is about 1.31 seconds and that of the integrated system is about 2.51 seconds both in the noontime. However, the maximal difference of the response time for GPRS and the integrated system is about 0.2 seconds for difference timeframes. The number of DTCs also affects the response time of the integrated system.

It increases about 1.8% for one more DTC. The measured results show that it is sufficient for the service center to offer the necessary actions if vehicles are in troubles.

ACKNOWLEDGMENTS

This research work is supported by National Science Council under Grand NSC-96-2516-S-018-001 and NSC-96-2221-E-018-006.!

REFERENCES

[1] J.H. Visser and R.E. Soltis, “Automotive exhaust gas sensing systems,” IEEE Transactions on

Instrumentation and Measurement, vol. 50, no. 6, 1543-1550, 2001.

[2] P. Greening, “On-board diagnostics for control of vehicle emissions,” Proceedings of IEE Colloquium on Vehicle Diagnostics in Europe, London, February 23, 1994.

[3] S. Godavarty, S. Broyles, M. Parten, “Interfacing to the on-board diagnostic system,” Proceedings of IEEE Vehicular Technology Conference, 52nd-VTC, vol. 4, 2000, pp. 24-28.

[4] W. K. Waldeck, “Diagnostic protocol challenges in a global environment,” Proceedings of Convergence International Congress & Exposition on Transportation Electronics, Detroit, MI, USA, October 2002.

[5] C.E. Lin, C. C. Li, S.H. Yang, S.H. Lin, C.Y. Lin,

“Development of on-line diagnostics and real time early warning system for Vehicles,” Proceedings of Sensors for Industry Conference, Houston, Texas, USA, Feb.

2005, pp. 45-51.

[6] SAE Standards, SAE J1850: “Class B Data Communications Network Interface,” 2006.

[7] ISO Standards, ISO 9141-2: “Road vehicles - Diagnostic systems Part2: CARB requirements for interchange of digital information,” 2005.

[8] ISO Standards, ISO 14230: “Road vehicles-Diagnostic systems-Keyword Protocol 2000,” 2004.

[9] SAE Standards, SAE J2012, “Diagnostic Trouble Code Definitions Equivalent to ISO/DIS 15031-6,” 2002.

[10] GSM Association, GSM World from the GSM Association Home Page, [Online]. Available:

http://www.gsmworld.com

[11] J. Rapeli, Standardization for global mobile communications in the 21st century, European Telecommunications Standardization and the Information Society, The State of the Art, ETSI, 1995, pp. 176-185.

[12] B. Ghribi and L. Logrippo, “Understanding GPRS: the GSM packet radio service”, Computer Networks, vol: 34, no. 5, pp. 763-779, 2000.

[13] C. Bettstetter, H. J. Vogel, and J. Eberspacher, “GSM phase 2+ general packet radio service GPRS:

architecture, protocols, and air interface,” IEEE Communications Surveys, vol. 2, no. 4, 1999.

[14] Morgan Doyle Limited Company, GPRS Tutorial, [Online]. Available: http://www.morgandoyle.co.uk/

[15] J. Schill, “An overview of the CAN protocol,”

Embedded System Programming, vol. 10, pp. 46-62, 1997.

[16] W. Lawrenz, CAN System Engineering: From Theory to Practical Applications, New York: Spring-Verlag, 1997.

[17] N. Navet, “Controller area network: CANs use within automobiles,” IEEE Potentials, vol.17, pp. 12-14, 1999.

[18] L. Chaari, N. Masmoudi, and L. Kamoun, “Electronic control in electric vehicle based on CAN network,”

IEEE Conference on Systems, Man and Cybernetics, vol.

7, 2002, pp. 4-7.

[19] X. Wang, C. Chen, and H. Ding, “The application of The International Conference on Electrical Engineering 2008

controller area network on vehicle,” Proceedings of the IEEE International Vehicle Electronics Conference, 1999(IVEC’99), vol.1, 1999, pp. 455-458.

[20] M. Farsi, K Ratcliff, and M. Barbosa, “An overview of controller area network,” Computing & Control Engineering Journal, vol.10, pp. 113-120, 1999.

[21] K.C. Lee and H.H. Lee, “Network-based fire-detection system via controller area network for smart home automation,” IEEE Transactions on Consumer Electronics, vol. 50, pp. 1093 – 1100, 2004.

[22] C.E. Lin, C.C. Li, A.S. Hou, and C. C. Wu, “A real time remote control architecture using mobile communication,” IEEE Transactions on Instrumentation and Measurement, vol. 52, pp. 997-1003, 2003.

[23] J.S. Young, “Data Communication Protocol of SRU/LRU for Vehicle Network Systems Based on CAN,” Submitted to The International Conference on Electrical Engineering 2008, 2008.

Biographies

Jieh-Shian Young was born in Taoyuan, Taiwan, R.O.C., in 1964.

He received the B.S. in Department of Mechanical Engineering from National Chiao Tung University, Hsinzhu, in 1986, and the M.S. and Ph.D. in Institute of Aeronautics and Astronautics form National Cheng Kung University, Tainan, Taiwan, R.O.C. in 1988 and 1990, respectively.

He was a scientist in Chung Shan Institute of Science and Technology from 1990 to 2004. He is currently an associate professor of the Institute of Vehicle Engineering, National Changhua University of Education. His research interests include communication protocols, automotive electronics, avionics, steering control, and flight simulation.

Yu-Wei Huang was born in Taiwan, R.O.C., in 1959. He received his BSEE and MSEE degree from National Tsing Hua University in 1981 and 1983 respectively, Ph.D. from National Cheng Kung University in 1989. Since 1996, he has been a professor at National Chang-Hua University of Education. His research interests are in microprocessor control, air-conditioning thermal comfort control, energy system for electric vehicle.

Ching-Wei CHANG was born in Taipei, Taiwan, R.O.C., in 1983. He received the B.S. in Department of Vehicle Engineering, Formosa University, Yunlin, in 2005, and M.S.

in Institute of Vehicle Engineering, National Changhua University of Education, Changhua, Taiwan, R.O.C., in 2007. His research interests include the automotive

electronics, ODB systems, GPRS technologies, etc.

July 6-10, 2008, OKINAWA, JAPAN

1