MEMS Technology in Automotive Industry: Trends and Applications Abstract Identification of the emerging technologies for an industry and the channel technology related information into an organization, possibly through technology scouting is a key concept used in the technology management. In this paper, a practical technology scouting approach is employed to introduce the newest and most important applications of the MEMS technology in the automotive industry. In recent years, MEMS technology with a broad variety of MEMS sensors has been used widely in the automotive industry, so that at least 30 sensor nodes of a modern vehicle with 100 sensor nodes are MEMS and the automotive industry is the second market of MEMS technology. First, we categorize the general MEMS technologies into 4 classes, and various applications are investigated. Then, it is shown that the MEMS sensors have contributed to fuel consumption reduction, safety improvements and cost-effective vehicles, and the previous sensors can be replaced easily by the MEMS sensors. Finally, MEMS standpoint in the automotive industry at present and in future is evaluated. Keywords: MEMS Technology, Technology Management, Automotive Industry, Sensor 1. Introduction Micro-Electro-Mechanical Systems (MEMS) is a combination of electronic and mechanical elements, sensors, and active elements on a silicone sub-layer adapting the micro-fabrication technology. The MEMS makes it possible to implement a whole system on a single chip, and so it has got a wide range of application. Under the assumption that the integrated microelectronic circuits are the central core of a system, the MEMS sensors, through gathering the information, allow the system to measure the parameters and control the ambiance [1]. In recent years, electronic technologies in modern vehicles have been evolving both in quantity and complexity. These technologies have contributed to major improvements in vechicles such as more safety and less fuel consumption which are critical issues in developing countires. Figures 1. and 2. show trafic density, number of accidents and injured or killed people; and average fuel consumption over years in the US, respectively [2], [3]. As it can be seen, considerable improvments have been achieved by passing time. To a great extend, this is due to the enhancement in the electronic systems of the vehicles. All of these electronic systems depend on the input from sensors, and a growing share of them is manufactured using MEMS technology. Compared to the other sensors, the MEMS sensors, due to their considerable advantages, have a variety of uses in the automotive industry, and now at least 30 sensor nodes of a modern vehicle with 100 sensor nodes are MEMS [4]. Also, hundreds of millions of MEMS sensors have been utilized in vehicles over the past decade. In this paper, the most recent and main applications of the MEMS technology in the automotive industry are introduced through technology scouting approach. Technology scouting is a powerful tool which contributes to technology management by identifying emerging technologies, and channel technology related information into an organization. First, we classify the general MEMS technologies into 4 classes, and different applications are investigated. Finally, MEMS market in the automotive industry at present and in future is evaluated. 1
Figure 1. Trafic density, number of accidents and injured or killed people over years Figure 2. average fuel consumption over years 2. MEMS Categories Figure 3. shows MEMS general technologies. MEMS technologies can be generally classified into four categories: accelerometers, gyroscopes, and inclinometers; flow and pressure sensors; emerging applications like the IR sensors for air quality and micro-scanners for vehicle displays etc.; as well as other applications such as the MEMS oscillators, and energy scavengers for TMPS. Any of these categories involves different applications to address the specific objectives in the vehicle. In the following, the most important and widespread uses of the MEMS are investigated [4]. Figure 3. MEMS general technologies 2.1 MEMS sensors for the passenger safety systems Detection of the possibility of a car accident for controlling the air bags makes up the widest use of MEMS sensors in the automotive industry. The use of MEMS accelerometers for the air bag control 2
chip eliminates the need for the g switches as the acceleration sensors in the air bag chip. In fact, the g switches are expensive, and their distribution in different places of the vehicle increases the costs and reduces the reliability. In this context, an accelerometer continuously measures the vehicular acceleration, and in case the acceleration exceeds a predetermined threshold, then a microcontroller computes the acceleration integral (the lower surface of the curve) to show whether a big change has occurred in the car speed or not. If so, then the air bags act [5]. Since the MEMS accelerometers perform continuous measurement (analogue), all the g switches can be replaced by a single MEMS module in the air bag control terminal. As a result, the reliability increases, and the cost of the air bag system is reduced which results in increasing the use of such systems in all the vehicles. Another considerable capability of the MEMS accelerometers is that they can perform self-testing with high reliability, and so enable the air bag processor chip to investigate whether the information gathered by the sensors are reliable or else the air bag chip needs to be serviced [5]. Figure 4. Generations of the high- g acceleration senssors used in the airbags [2]. Besides, the decision making about activating the passenger side air bags must be made quickly as possible, because, due to the small space between the passenger and the side body of the vehicle, the energy absorption is much less. Indeed, there is a very short distance between the air bag and the passenger. In this context, the importance of the MEMS accelerometers is further emphasized. As a result, many vehicles outfitted with side air bags may add two to four more MEMS accelerometers for this function [6]. Figure 4. Generations of the high- g acceleration senssors used in the airbags, BOSCH Co. 2.5. Rollover and Skidding Detection Another application of the MEMS sensors in the vehicle control systems is the rollover and skidding detection [2]. Such a characteristic is now quickly and widely accepted by all of the car manufacturers as a modern standard particularly for vans, pickup trucks, and sport utility vehicles, which are more likely to roll over. A two-axle low g range accelerometer is the most appropriate thing for measuring the speed along z and y axes. Here, the MIMO accelerometer and gyroscopes have a good performance, too [5]. Figure 6. gyroscopes sensor for rollover detection, BOSCH Co. [2]. Figure 6. gyroscopes sensor for rollover detection, BOSCH Co. 2.2. Tire Pressure Sensors A study at Indiana University in 1977 estimated that 260,000 vehicle crashes occurred each year in the US because of underinflated tires (out of a total 18 million crashes for all reasons). Hence, the US congress mandated tire pressure sensors (TPS) on all new passenger vehicles and light trucks from 3
September 2007. TPS informs the drivers about the tire underinflation, leaks, and also the air pressure loss which naturally happens. Battery lifetime is of crucial importance in the TPS because in many TPS systems, battery replacement requires the substitution of the whole package. In this case too, cost reduction is a matter of considerable concern that draws attention of the car manufacturers to the MEMS sensors suppliers. However, it still takes time for the appropriate pressure sensors to enter the market [6]. Figure 5. A typical TPS package. This segment is expected to grow at a combined annual growth rate (CAGR) of 30.7% and generate revenues of $526.7 million in 2012. As the technology advances, the TPS systems change into much lighter, smaller, and battery-free systems which are connected to the tire rather than the rim. These systems are called intelligent tire systems. It is expected that from the year 2012 forth, intelligent tires with battery will be replaced by the intelligent tires fed by the MEMS vibration energy scavengers [4]. Figure 5. A typical TPS package 2.3. Electronic Stability Control of the Vehicles Electronic stability control (ESC) can be regarded as the most important electronic system in the modern vehicles in the sense of the vehicle safety. It helps drivers maintain control of vehicles in sudden maneuvers. According to the Insurance Institute for Highway Safety, ESC could save 10,000 lives each year in the US and save 4000 lives and prevent 100,000 injuries in Europe. Based on the new rules in the US, ESC systems have been phased in gradually, i.e. 55% of model year 2009 cars, 75% of model 2010 cars, and so on, to 100% in model 2012. Europe recently is preparing exact guidelines for introduction of ESC on all vehicles in 2014 [7]. Nowadays, ESC systems comprises over 66% of the gyroscopes revenues, and it is forecasted that the number of the ESC units reaches from 23 million ESC systems in 2007 to 48 million in 2012 [4], [7]. Figure 6. shows generations of the gyroscopes used in the ESC, in which MEMS gyroscopes are better in terms of size, efficiency, and reliability [2]. The growth in the ESC systems creates a continuing need for use of the accelerometers. In this context, some companies using the MEMS have designed some devices in which several accelerometer and gyroscope sensors are combined. These devices are highly economical. Fig.5 shows a typical device of this type, manufactured in the BOSCH Co. Figure 6. Generations of the gyroscopes used in the ESC, BOSCH Co. 2.4. Vehicle Dynamic Control Vehicle Dynamic Control (VDC) helps the driver to maintain the vehicle s stability when it starts to skid. If the VDC works correctly, the driver does not even sense the presence of this system in the 4
car. Before the development of MEMS accelerometers and gyroscopes, the VDC application in the usual passenger cars was impractical. Because the conventional accelerometers and gyroscopes added hundreds of dollars to the vehicle s cost. On the other hand, due to the addition of mechanical antivibration, the traditional MEMS gyroscopes had a large size (100 cm3); however, this problem has been solved in the novel MEMS sensors. For example, a typical MEMS gyroscope of the Analog Devices Co. is 0.15 cm3 [8]. 2.6. MEMS Sensors for Engine Management MEMS sensors used in the engine management are comprised of the pressure sensors (including a wide range of pressure) and air mass flow sensors. For example, Fig.8 shows a barometric air pressure, BAP, sensor, which has widely been used in the recent systems related to the engine in ECU aiming for the adjustment of the fuel combustion process parameters with the varying atmospheric pressure [2]. Figure 7. shows BAP sensor, BOSCH Co. Figure 7. BAP sensor, BOSCH Co. 2.7. Electronic Parking Brake Systems When you activate the vehicle parking brake, you rarely pull it sufficiently regardless of the required brake pressure; therefore, the parking brakes should be basically more than the design requirements. In new systems, electronic parking brake systems are activated by just pressing a button. In these systems, by use of a low g range MEMS accelerometer, the acceleration and then the inclination of the vehicle are measured, so that the required amount of brake pressure is determined and implemented. Thanks to such a good feature of the new systems, the manufacturers can get rid of the hard work on making large and unsuitable systems [5]. 2.8. Antitheft Systems Generally speaking, the antitheft systems are now in a continuous state of development. One of the most common ways of car theft is to pull it by the rope or chain. In order to deal with this sort of car theft, many car manufacturers have applied the antitheft systems mounted on the tilt detection systems [5]. A three-axis accelerometer is used to measure the vehicle inclination in proportion to the earth. If the car theft is carried out using a rope, then the accelerometer measures the change in the inclination angle, and the safety system of the car will be activated. Besides, this accelerometer can detect the wheel theft [9]. The conventional sensors have a limited range of inclination measurement and are impractical in many situations, while the MEMS accelerometer sensors are ideal for this application [5]. 2.9. Vehicle Navigation Systems The vehicle navigation systems have rapidly become the standard characteristic in the modern, luxurious cars. GPS plays a key role in the tracking system; however, it cannot provide solely all the information required by the system. In urban areas, there is a strong possibility of signal blocking by the elevated buildings or long tunnels. In this case, after obtaining the initial directions by GPS, the navigation system makes use of a gyroscope for obtaining information about the forward path, and a low g accelerometer for information about the position [5]. 5
2.10. Other Applications of MEMS in the Vehicles Some of the other applications of MEMS in the cars are CAM/crankshaft position, fuel-line, X- by-wire, fuel evaporation, motor damping, headlight leveling, absolute-manifold pressure (MAP), wheel speed, and so on. It should be noted that up till now, more than 70 potential uses have been recognized for MEMS in the automotive industry [1]. 5. MEMS Trends in the Automotive Industry Safety systems in modern vehicles are becoming more advanced and more complex, and MEMS that are crucial to their operation. However government mandates are more important than safety systems market. When governments make safety systems mandatory, MEMS suppliers see a big benefit. Some studies indicate that the total Available Market multiplied by 2 or 3 and innovation is needed at sensor and system level [7], [10]. Figure 5. shows the worldwide automotive MEMS revenue forecast [11]. As it can be seen from this figure, the annual worldwide average growth rate is 9.0% and China became the world s fastestgrowing country for automotive MEMS sales with average growth rate of 14.8%. According to the reports, the MEMS technology share in the automotive industry was 1.6 billion dollars in 2006, and has created the second great market of MEMS after the IT technology. Nearly 100 million airbag, tire pressure monitoring, and electronic stability (ESP) safety systems that use MEMS shipped worldwide during 2010. They contained more than 300 million MEMS chips. In 2016, about 150 million systems are expected to be installed in vehicles, but the number of MEMS they contain will have rocketed to over 830 million. The chief markets involve ESC gyroscopes (272 million dollars), air bags (260 million dollars), MAP and BAP pressure sensors (192 million dollars), lateral air bags, and TPS systems [4]. The companies Bosch, Dalsa, Delphi-Delco, Denso, Infineon, Motorola, VTI Technologies, and X Fab constitute about 90% 0f the entire MEMS market in the automotive industry [1]. MEMS suppliers to the automotive market are currently few. This is no market for startups: it's difficult to get into. But profits can be significant for those that succeed [11]. Figure 5. Wordwide automative MEMS revenue forecast (millions of US dollars) 5. Conclusions In this paper, the newest and most important applications of the MEMS technology in the automotive industry have been introduced. It has been shown that many of the previous sensors can be simply replaced by the more cost-effective, safer, and smaller MEMS sensors, and hundreds of millions MEMS sensors have been used in the cars. Besides, most forecasts suggest that their application in the vehicles will continue to grow to address vehicle safety requirements as well as government mandates. Furthermore, due to the considerable advantages of such sensors in terms of technical and economic aspects, car engineers continually discover new applications for them so that the safety and efficiency of the vehicles can be enhanced. Now, the manufacturers usually use the MEMS sensors in the vehicle safety parameters. However, the applications related to the performance 6
improvement, comfort, and additional facilities and accessories are rapidly changing into the largest MEMS market in the automotive industry.. Acknowledgments The authors would like to thank the Center for strategic plan of the Iran Khodro Co. References [1] Allan, R., "MEMS:size Does Matter", www.electronicdesign.com/articles/articleid/8984/8984. [2] Ernest, P., "MEMS@Bosch:Automotive Application and beyond", BOSCH Co., www.mstbw.de/imperia/ md/content/mstbw/bestpractice/bosch_mems_12_micromachine_symposium_ernst.pdf. [3] Hayashi, M. and et. al., "Trends in Hitachi s MEMS Sensors for Automobiles", Journal of Hitachi Review, Vol. 58, No. 7, 2009. [4] Dixon, R., Bouchaud, J., "prospects of MEMS in automotive industry", Wicht Technologie Consulting, Online Journal of MEMS Investor, www.memsinvestorjournal.com/2007/08/prospects-for-m.html. [5] Weinberg, H., "MEMS sensors are driving the Automotive industry", Analog Devices Co., www.auto.sensorsmag.com. [6] Keck, D.O., "Making Sense of Automotive Pressure Sensors", Silicon Microstructures Inc. [7] Dixon, R. Bouchaud, J., "MEMS in Automative: How regulatory issues will reshape the market", isuppli Co. [8] Venkatesh, P., "MEMS in Automotive and Consumer Electronics", http://auto.sensorsmag.com. [9] "MEMS sensors for car alarm,crash recorder and more", ST company, www.st.com/mems. [10] Tanaka, M., "An industrial and applied review of new MEMS devices features", Elsevier Journal of Microelectronic engineering, Vol. 84, pp. 1341-1344, 2007. [11] "Automotive MEMS Market Brief", IHS isuppli Research, 2011. 7