Automotive technology

Robust three-axis sensor in engine compartment First combined inertial sensor with integrated vibration damper for ESP® from Bosch SMI650 senses yaw rate and acceleration

  • Immune to interference thanks to integrated mechanical vibration damper
  • Designed for the harsh conditions in the engine compartment
  • First application in generation 9 ESP® electronic control units
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  • November 16, 2012
  • Automotive technology
  • Press releases
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press release

The new Bosch SMI650 combined inertial sensor is designed to cope with the harsh environment found in a car’s engine compartment. It can withstand operating temperatures of up to +140 °C and is able to deal with even strong broadband vibrations thanks to a special vibration damper. This is the first time that an electronic control unit for the ESP® electronic stability program has featured a sensor with integrated vibration damper. ESP® electronic control units with integrated inertial sensors have no need for complicated wiring to connect to external sensors. A biaxial acceleration sensor (ay and az) and a monoaxial yaw sensor (Ox) together give the SMI650 fully fledged ESP® senses for monitoring a vehicle’s three axes of motion. The first series-production version of the new combined inertial sensor will be incorporated in Bosch’s current generation 9 ESP® electronic control units.

Keeping the sensor elements free of interference
The current trend in automotive sensor technology is to use combination sensors. This makes sense because integrating various sensor elements in one housing makes their handling, fitting, and electrical connections considerably more straightforward – with a resulting reduction in costs. But a combination sensor such as the SMI650 has to be able to cope with more challenging conditions, since it has to make the transition from the comfort of the passenger compartment to a car’s “torture chamber”: the engine compartment. Here, temperatures can swing wildly from way below freezing to way above the boiling point of water, while the sensors must avoid misinterpreting the strong vibrations caused by a huge variety of engine types as unstable driving conditions. In order to shield the SMI650’s sensor elements against such sources of interference, the PM28D sensor housing has been fitted with a vibration damper. Its base plate is enveloped in a specially developed silicone material, isolating the sensors from background vibrations. But that is not all: Bosch engineers have also provided the tiny acceleration sensor structures with micromechanical dampers. Together with the optimized component’s own ASIC an up to now unmatched robustness of the sensor was realized. Therefore it is well suited for the integration in units.

Background: the ESP® electronic stability program
A microcomputer in the ESP® electronic control unit monitors the signals transmitted by the ESP® sensors and compares the driver’s steering input to the vehicle’s actual motion 25 times every second. If the values diverge, the ESP® reacts in a flash, applying metered braking to generate the counteracting force necessary to ensure the vehicle continues to follow the driver’s steering input to the extent physically possible. Bosch launched ESP® in 1995, and the sensors that measure yaw rate and lateral acceleration were first integrated into the electronic control unit in 2008. Up to then, they had been fitted separately within the passenger compartment.

 Technical data - SMI650 (excerpt)
 Sensor axis Ωx ay, az
 Measurement range ±100 °/s ±2,0 g
 Sensitivity 100 LSB/°/s 5000 LSB/g
 Sensitivity variation ±3 % ±5 %
 Nonlinearity ±0,5 °/s ±30 mg
 Offset variation ±3 °/s ±70 mg
 Noise (RMS at 60 Hz) 0,6 °/s 10 mg
 Bandwidth (- 3 dB) 57 Hz -
 Supply voltage 5 V
 Current draw, maximum 25 mA
 Ambient temperature - 40 °C to +140 °C
Background: MEMS technology
Bosch was one of the pioneers in the development of micro-electromechanical systems (MEMS) technology, and the company has produced well over two billion MEMS sensors since the start of production in 1995. Production volumes reach new record levels every year, with around half a billion sensors leaving the Reutlingen plant in 2011. This makes Bosch the world market leader, with a product range that comprises pressure, acceleration, yaw-rate, and inertial sensors for many applications in the automotive industry and in consumer electronics. For more information about Bosch automotive sensors, visit

Ron Xu, phone: +49 711 35-39711

Automotive Technology is the largest Bosch Group business sector. In 2013, its sales came to 30.6 billion euros, or 66 percent of total group sales. This makes the Bosch Group one of the leading automotive suppliers (NB: Due to a change in accounting policies, the 2013 figures can only be compared to a limited extent with the 2012 figures). Automotive Technology largely operates in the following areas: injection technology for internal-combustion engines, alternative powertrain concepts, efficient and networked powertrain peripherals, systems for active and passive driving safety, assistance and comfort functions, technology for user-friendly infotainment as well as car-to-car and Car2X communication, and concepts, technology, and service for the automotive aftermarket. Bosch has been responsible for important automotive innovations, such as electronic engine management, the ESP anti-skid system, and common-rail diesel technology.

The Bosch Group is a leading global supplier of technology and services. In 2013, its roughly 281,000 associates generated sales of 46.1 billion euros. (NB: Due to a change in accounting policies, the 2013 figures can only be compared to a limited extent with the 2012 figures). Its operations are divided into four business sectors: Automotive Technology, Industrial Technology, Consumer Goods, and Energy and Building Technology. The Bosch Group comprises Robert Bosch GmbH and its roughly 360 subsidiaries and regional companies in some 50 countries. If its sales and service partners are included, then Bosch is represented in roughly 150 countries. This worldwide development, manufacturing, and sales network is the foundation for further growth. In 2013, the Bosch Group invested some 4.5 billion euros in research and development and applied for some 5,000 patents. This is an average of 20 patents per day. The Bosch Group’s products and services are designed to fascinate, and to improve the quality of life by providing solutions which are both innovative and beneficial. In this way, the company offers technology worldwide that is “Invented for life.”

Further information is available online at and,

PI7961 - November 16, 2012

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