Comparative study of MAF and MAP sensor for.pptx

Comparative study of Air intake automotive sensors

1. COMPARATIVE STUDY OF MAF AND MAP SENSOR FOR GASOLINE ENGINES AND DEVELOPMENT OF MAF TEST BENCH Externally guided by Mr. Bharadwaj MK Deputy Manager (gasoline systems R&D) Robert Bosch India Submitted by Jishnu Sreenath 160978010 M.Tech Automobile engineering 2 nd year MIT, Manipal Guided by Dr. Deepak Lawrence K Associate Professor Dept. of Aeronautical & Automobile Engineering MIT, Manipal

2. Area of work ORGANISATION : BOSCH LIMITED , ADUGODI ,BANGALORE. Reporting manager: Mr. Bharadwaj MK (Dy. Manager , GS) DEPARTMENT : 4 WHEELER SYSTEM ENGINEERING ( GASOLINE SYSTEMS R&D) TEAM : IC ENGINE TEAM OTHER TEAMS : HYBRID TEAM, CALIBRATION TEAM , QMC TEAM 31-05-2018 2

3. Contents Introduction Literature survey Problem definition Objectives Background theory Methodology Mounting Results and discussions Conclusion Reference 31-05-2018 3

4. Introduction Any precise air-to-fuel ratio control system requires mass air-flow sensing. Therefore, recent needs for a better air-fuel ratio control have led to the introduction of air-flow sensors on diesel automotive engines in India. To comply with the legally specified emission limits for motor vehicles, a specific air-fuel ratio must be precisely maintained. 31-05-2018 4

5. Introduction The use of sensors is required which accurately record the actual air-mass flow and output is in the form of an electrical signal to the control electronics. The sensor is used to measure the air-mass flow in internal combustion engines for precise adaption of the injected fuel quantity to the current power requirement, atmospheric pressure and air temperatures. The requirement for a MAF sensor test bench was also fulfilled in this project. As the MAP sensor will be replaced by MAF sensors in future IC engines, there is chance that number of faulty sensors might increase due to the increase in demand and production volumes. 31-05-2018 5

6. Literature survey In 1991, A micromachined monolithic silicon sensor was developed. It works on the principle of a hot wire anemometer with the usual metal wires replaced by film resistors supported in thin silicon beams . Patrick J. Buehler and, Matthew A. Franchek (2002) developed an information synthesis approach to engine diagnostics. This work focused on the diagnosis of the MAF sensor used for engine fuelling control. Tooru Nomura and Atushi Saitoh [2004] proposed a new thermal mass flow sensor consisting of two Surface acoustic wave(SAW) delay lines on a piezoelectric substrate and investigated its characteristics in experiments 31-05-2018 6

7. Literature survey Wang Changhui, Liu Zhiyuan(2015) defined a piecewise linear interpolation model in the form of vector-vector dot product by defining membership function in order to update MAF sensor relative errors on the grid points. Miao Mingming(2016) analysed heat transfer principle of thermal gas flow meter, and presented a method of the flow measurement based on single platinum resistance. The sensor works in CTD (Constant Temperature Difference) controlling mode. Olig Sazhin (2012) Developed an analytical model of the thermal flow sensor. The results of analytical model application are utilized to develop a thermal flow microsensor with optimal functional characteristics. 31-05-2018 7

8. Problem definition Currently the GASOLINE vehicles in India are not equipped with Air mass sensors. Mass of air coming into the intake manifold is calculated by ECU according to the output of MAP sensor (Manifold absolute pressure sensor) in combination with lambda sensor. If MAF (Mass air flow sensor or Air mass sensor) sensor is implemented into the gasoline vehicles in the air intake section, it may be possible to get accurate direct air mass output signals, rather than depending on estimated or calculated values from other sensors. Based on primary objectives, the idea is to analyse which sensor gives the accurate and reliable readings. Both sensors will be tested on a single vehicle at different throttle positions . Also considering the above objectives, the secondary objective is to build a MAF sensor test bench which is compact and can be used for testing field MAF sensors. As there was no reliable solution currently for testing new generation MAF sensors, it was a primary requirement from the customers of Bosch, such as Maruti Suzuki, TATA and Mahindra. 31-05-2018 8

9. Objectives To develop an external circuit for MAF sensor from which output signal is acquired into a user interface device with appropriate software. To analyse the obtained data from the MAP and MAF sensors tested on a single vehicle at different throttle positions and evaluate the difference in mass flow rate values in order to compare the accuracy of MAP sensor and MAF sensor. To design and make a 3D rendered CAD model of MAF sensor test bench. To develop and fabricate the MAF test bench according to the 3D rendered model for testing the working of MAF sensor locally. 31-05-2018 9

10. Background theory A measurement of the air flow is accomplished using either a mass-air flow (MAF) sensor or manifold air pressure (MAP) sensor. Based on the air mass estimate and knowing the desired air fuel ratio that meets the emission requirements, the fuelling control system calculates the necessary amount of fuel to be injected. Using this mass of fuel and measuring the injector characteristics, the fuelling controller is able to determine the needed injector pulse width command. 31-05-2018 10

11. MASS AIR FLOW SENSOR (HOT FILM TYPE – HFM) 31-05-2018 11

12. Types and Variants ( Bosch-hot film type ) Based on generation – HFM5, HFM6, HFM7, HFM8( 8 th Generation ) Based on type of signal output- 1. Voltage output – 0 to 5V 2.Frequency output (Digital) – 1800 Hz to 9000 Hz 31-05-2018 12

13. WORKING PRINCIPLE In the mass air flow meter, the amount of heat extracted from a heated sensor element by heat transfer from the heating element to the air flow increases with an increasing air mass. The final difference in temperature is taken as the measure of the mass flow rate of air. An integrated embedded circuit evaluates the measured data and thus permits precise recording of the air volume, including the flow direction. The MAF sensor can now be equipped with other sensors, such as a temperature sensor and an intake air humidity sensor. 31-05-2018 13

14. Sensor element 31-05-2018 14

15. Sensor theory This project mainly concentrates on analysing the accuracy of air flow measurements using both MAF sensor and MAP sensor. The main difference between both sensors is that, MAF sensor gives direct measurement of mass of air whereas the MAP sensor estimates the air flow by reading pressure values and converting them to mass values by doing a mathematical calculation using the ideal gas equation. The estimated value may have to be multiplied by some correction factors to almost get the correct value of mass air flow rate. 31-05-2018 15

16. Sensor theory So there can be chances of error while estimating the mass of air, compared to reading direct values in terms of volts or frequency. For MAF sensors the manufacturers provide a technical data sheet for identifying the values of signals that corresponds with the values of mass air flow rate. 31-05-2018 16

17. Characteristic curve (voltage o/p type) 31-05-2018 17

18. Characteristic curve (frequency o/p) 31-05-2018 18

19. MANIFOLD ABSOLUTE PRESSURE SENSOR (MAP sensor) The MAP (Manifold Absolute Pressure) sensor, absolute pressure of admission, detects the air pressure at the inlet of the vehicle and turns it into an electrical signal which is sent to the engine’s electronic control unit (ECU) in order to regulate the stoichiometric mixture. 31-05-2018 19

20. Sensor Element The sensor element of the MAP is a piezoresistive type configured as a wheatstone bridge, i.e., its electrical resistance varies according to the mechanical deformation of a membrane . The incorporated digital electronics allow it to program the output signal between 0-5 V All this is protected with a receptacle and a silicone gel. The electronic circuit is achieved through hybrid technology and is handled in a clean room due to its sensitive nature. 31-05-2018 20

21. Characteristic curve 31-05-2018 21

22. Methodology Install the whole circuit into a gasoline vehicle with the MAF sensor fitted in the air intake pipe between the air filter and throttle body. Connect the vehicle ECU to a device which can read all the outputs from all sensors inside the vehicle. (preferably a laptop PC with On-board Diagnostics Software eg ;- INCA 7.1, Picoscope Automotive). For MAF sensor with digital output, and oscilloscope interface was used to get frequency outputs. Run the engine at different throttle positions and log the readings from different sensors at different time intervals. Compare the output data and observe the Mass flow values from the sensors . Analyze the difference in values given by both sensors. 31-05-2018 22

23. Vehicle mounting The vehicle used for mounting the setup was Suzuki Swift 1.2liter petrol. 31-05-2018 23

24. Measurement procedure Initially , the setup was tested for with small air flow for checking the response patterns and noise. Later on, the whole setup was mounted on vehicle and the MAF sensor between the air cleaner and throttle body.   Air flow Measurements were taken from both MAF and MAP sensor using Picoscope (automotive oscilloscope) and INCA (UV interface) at same time at different throttle positions. Readings from MAP sensor is usually tapped from the ECU using ES 590 vehicle module. 31-05-2018 24

25. Mounting under hood (MAF sensor) 31-05-2018 25

26. MAF sensor installation 31-05-2018 26

27. Measurement tools Picoscope Automotive SW and HW ETAS Inca 7.1 UV interface SW ETAS ES 590 data module HW 48 pin breakout box Banana connectors 31-05-2018 27

28. Circuit (MAP sensor) 31-05-2018 28

29. Developed Circuit for MAF sensor 31-05-2018 29

30. MAF sensor test bench For the other objective, the requirement was to fabricate a device for checking the working of the MAF sensors. In future most of the vehicles will be using MAF sensors for accurate airflow measurements and the demand is steadily increasing at a faster pace . 31-05-2018 30

31. Output signal sample (MAF) 31-05-2018 31

32. Test bench requirement Lot of faulty sensors from the customers are sent to Bosch plant in Bangalore for testing. Since there in no official testing equipment available in Bangalore plant, there was requirement to make a simple low cost test bench for basic electrical and functioning test. This task was assigned to our research and development team to design and fabricate a new test bench. For this task, the concerned department allotted a budget, so that accordingly resources and inventory were acquired and fabrication was done. 31-05-2018 32

33. 3D CAD model of the test bench 31-05-2018 33

34. M ethodology Bosch blower of flow rate 4.5 m 3 /min spec was connected to a coupler pipe with other end connected to 70mm dia HFM. Wiring was arranged and connected according to the test circuit developed for frequency output HFM. Blower was turned on with max flow. The output reading was acquired and logged, and compared with characteristic curve of that HFM. Since the requirement was to check whether HFM was giving variable output corresponding to variable air flow, specified objective was accomplished. 31-05-2018 34

35. Tools Used Bosch 820 W blower (max flow rate 4.5 m3/min).- This device is source for air flow , as it can produce a good air flow rate almost equivalent to a non-turbo charged 1200cc engine. Multimeter- For getting the frequency output Power supply units- during initial testing in workstation, S eparate 12V and 5V power supply units where used. DC batteries 1.2 Kohm resistor BNC cables with crimping at other end Banana connectors Cone air filter 31-05-2018 35

36. Results and discussions 31-05-2018 36

37. Discussions From obtained results, there is a significant difference of mass flow value measured directly for MAF and calculated value from MAP by ECU. There is approximately a difference of 3- 4 kg/hr between the values acquired. As a cost cutting method, manufacturers has implemented MAP sensors for estimating air flow rate. Therefore, by 2020 gasoline vehicles should be equipped with accurate MAF sensors for improving combustion characteristics and to meet the new emission norm . 31-05-2018 37

38. Discussions This results implies that calculated or estimated values shows a percentage of error compared to the direct mass flow values acquired from the MAF sensor. Since the measurement accuracy is more for MAF sensor, it can be implemented to gasoline vehicles for mass air flow measurement. The deviations occur because of the estimation methodology used in MAP sensor systems. Comparing the cost of these sensors, MAF sensor is 5 times more expensive than MAP sensor. 31-05-2018 38

39. MAF Sensor Test bench 31-05-2018 39

40. W orking As per customer demands, our team have designed a portable test bench to check the functional testing of Mass air flow sensor. The blower the is primary source of air flow. As per specification the blower can achieve a maximum of 4.5 m3/min flow rate. The final mass flow rate of air coming out of the blower can calculated by multiplying with current air density. The blower speed can be adjusted to a low rate also. A flow controller switch is present in the blower , which is very helpful in controlling the air flow. When the blower is turned on, the MAF starts to take reading and give output.   When the blower is turned on to maximum speed, the MAF sensor will show a reading in Hz which corresponds to the mass air flow value as given in the characteristic curve. 31-05-2018 40

41. Test bench The circuit used for this setup is same as that used in the primary task for MAF sensor. To make it more compact and portable, we replaced the power box unit by DC battery. It can be used for any type of field testing, as it is made portable and compact to possible size and can easily assembled within no time. 31-05-2018 41

42. Conclusion MAF sensors can greatly improve the engine performance in a better way for gasoline vehicles, same way as it has improved the diesel engine since its implementation. Sensors are mostly electronic components, which are susceptible to get damaged for any reason like electrical failure, functional failure etc. Also , there is a lack of reliable local test setup for this sensor in India. Considering these drawbacks, we teamed up with GS/QMC dept. to develop the portable MAF sensor test bench. Today Maruti Suzuki, TATA motors, Mahindra are jointly working with Bosch on development strategies to improve the IC engine characteristics. 31-05-2018 42

43. Future scope Lot of works has been also carried out for building test benches for sensors. Every year new improvements are made to the existing designs. For MAF sensor test benches, improvements can be made in the flow characteristics. Also implementing a reference flow meter in the test bench can help in comparing the deviation in the readings shown by the sensor . Fitting a velocity stack in front of the suction part can improve the velocity profile of air entering the specimen 31-05-2018 43

44. Reference [ 1] O . Sazhin, “Novel mass air flow meter for automobile industry based on thermal flow microsensor. I. Analytical model and microsensor,” Flow Meas. Instrum . , vol. 30, pp. 60–65, 2013. [ 2] P . J. Buehler, M. A. Franchek , R. W. H. Laboratories, and W. Lafayette, “Mass Air Flow Sensor Diagnostics for Adaptive Fueling Control of Internal Combustion Engines,” Proceedings of the American Control Conference Anchorage. , 2002. [ 3] T . Nomura, A. Saitoh , and K. Koyama, “Mass Flow Sensor Using Dual SAW Device,” IEEE Int. Freq. Control Symp . , pp. 25–30, 2007. [ 4] Z . Liu and C. Wang, “An LPV adaptive observer for updating a map applied to an MAF sensor in a diesel engine,” Sensors (Switzerland) , vol. 15, no. 10, pp. 27142–27159, 2015. [ 5] M . Mingming, “Research of Thermal Gas Flow Measurement Based on Single Sensor,” pp. 391–395, 2016. [ 6] T . Aono and T. Kowatari , “A signal processing algorithm for compensating for back flow effect in intake air mass measurement in internal combustion engines,” Proc. 2004 IEEE Int. Conf. Control Appl. 2004. , pp. 356–363, 2004. [ 7] M . Pereira, “Flow meters: Part 1,” IEEE Instrum . Meas. Mag. , vol. 12, no. 1, pp. 18–26, 2009. [ 8] J . Ye, L. Chen, F. Tian, Z. Wu, and X. Hu, “Design and Implementation of Instantaneous Flow Rate Measurement for Air Splicer,” IEEE Instrum . Meas. Mag., pp. 298–301, 2012. 31-05-2018 44

45. Thank you. 31-05-2018 45