Accelerometer can be used to detect the acceleration of object and gyroscopes detects angular velocity of objects, and are widely used in various devices such as smart phones. In automotive applications, Inertial sensors are widely used and can greatly improve the stability and safety of vehicles. This article will show you the application and development of Inertial sensors in the automotive field, and the product characteristics and advantages of MEMS gyro sensors introduced by Murata.
New applications of inertial sensors in the automotive field are developing rapidly
New applications of inertial sensors in the automotive field are still emerging, which are used to improve road safety, such as ADAS and inertial navigation, hill-start assistance (HSA), dynamic headlight leveling, idling start and stop, engine anti-vibration, electronic parking brake (EPB), roll over detection (ROV), electronic stability control (ESC), etc. ESC is sometimes also called electronic stability program (ESP) and vehicle stability control (VSC). They are acronyms of the same system that controls vehicle driving dynamics. Different car manufacturers will use different acronyms to market the same system, but their basic functions are similar.
Anti-lock braking systems (ABS) and vehicle traction control are still insufficient when driving around corners. ESC can correct understeering and oversteering, and help to keep the car on the road. ESC can compare the Yaw rate and lateral acceleration measured by the angular rate sensor and the lateral acceleration measured by the low G accelerometer with the values calculated according to the wheel speed information and the steering wheel angle, so as to know the driving dynamics of the vehicle, and intervene and correct it in real time before danger occurs, so that the vehicle can run stably and safely.
Inertial sensors are either assembled into the vehicle as a sensor cluster or integrated into the brake unit or airbag ECU as in most current vehicle designs. The new system design adds the measurement functions of electronic parking brake (EPB), idle stop start (ISS), and even redundant Yaw sensors for automatic parking steering control and lane keeping assistant system. The ESC system has evolved from an intelligent ABS system to a central active safety vehicle system, which controls the stability of vehicles and provides information multiple systems. In the future, ESC sensors will play a role in various autonomous driving (AD) and ADAS applications to realize vehicle positioning and other functions.
Inertial sensors based on proven 3D MEMS technology
A gyroscope is a device used to measure or maintain direction and angular velocity. It is a spinning wheel or disk, in which the axis of rotation can freely present any direction. According to the conservation of angular momentum, when rotating, the direction of the axis is not affected by the tilt or rotation of the mounting. Gyroscopes based on other working principles also exist, such as microchip packaged MEMS gyroscopes, solid-state ring lasers, fiber optic gyroscopes, and very sensitive quantum gyroscopes in electronic devices.
The higher the accuracy of the gyro sensor to the ambient conditions in the vehicle, the better the control system. Murata's gyro acceleration sensor can provide reliable and accurate measurement in any assembly positions and measurement directions. Murata is also developing the next generation of combo sensors, which can realize high performance and cost-effective functional integration for various applications.
Murata's gyro sensors are based on Murata's proven 3D MEMS technology, along with highly integrated electronics developed to create gyroscope components. The performance level provided by industrial gyroscopes is usually only suitable for expensive modular products. The sensing elements and measuring circuit are assembled in a premolded plastic dual-in-line (DIL) package. Murata gyro sensors meet RoHS standards and are suitable for lead-free reflow soldering.
Inertial combination sensor for automotive safety-critical application
The SCA3100-D04 introduced by Murata is a high-performance three axis accelerometer component based on VTI capacitive 3D-MEMS technology. The component integrates high accuracy MEMS acceleration sensing and a flexible SPI digital interface. A dual flat lead (DFL) housing is adopted to ensure reliable operation over the product lifetime. The SCA3100-D04 is specially designed, manufactured, and tested to meet the high stability, reliability, and quality requirements of automotive applications.
The SCA3100-D04 accelerometer has very stable output in a wide range of temperatures, humidity, and vibration. The component conforms to the AEC-Q100 standard and has many advanced self-diagnosis functions. The DFL housing is suitable for SMD mounting and the component is compatible with RoHS and ELV directives. The SCA3100-D04 is a part of the VTI digital accelerometer family, and it is fully compatible with single-axis accelerometers (SCA800 series) and other multi-axis accelerometers (SCA2100 series and SCA3100 series).
The SCA3100-D04, a 3-axis high-performance accelerometer with a digital SPI interface, uses a 3.3V power supply voltage, has a measuring range of ±2g, can measure 3-axes in the XYZ directions, has an offset stability of ±30mg in the temperature range, an amplitude response of 45Hz, a mass of only 0.31 g, has an SPI digital interface and a wide range of self-diagnosis functions. The size is only 7.6×3.3×8.6 mm (width x height x length), which conforms to the AEC-Q100 standard. In addition, the packaging, pin-out, and SPI protocol of the VTI digital accelerometer product series are compatible. The DFL plastic packaging conforms to RoHS standards. The packaging adopts 330 mm embossed tape, and the number of standard packages is 100, which is suitable for lead-free welding processes and SMD mounting. It is a mature capacitive 3D-MEMS technology.
The SCA3100-D04 is developed for applications that require high stability. Typical applications include hill-start assistance (HSA), electronic parking brake (EPB), roll over detection, suspension control, inclinometer, motion and position measurement, etc.
Integrated four-axis/five-axis gyro acceleration sensor
The integrated SCC3000 gyro acceleration sensor introduced by Murata is an integrated X or Z dual-axis gyroscope 3-axis acceleration sensor with digital SPI interface, which meets the ISO26262 standard of the ASIL-D system and is a component family with pin-to-pin and software compatibility, including 4 DoF:X or Z gyroscopes combined with XYZ acceleration sensors, and 5 DoF:XZ gyroscopes combined with XYZ acceleration sensors. The angular rate measurement range is ±300°/s, enabling robust sensing in harsh environments.
The SCC3000 features ±6g 3-axis acceleration measurement (XYZ) range, and ±15g auxiliary 3-axis acceleration measurement (XYZ) range. The operating temperature ranges from -40°C to +110°C (please consult Murata separately if +125°C is needed), and the filter settings available for users are 13, 20, 46, 200, and 300Hz, and the supported power supply voltage is 3.0V ~ 3.6V. It can be applied to extensive self-diagnostics features and is qualified according to AEC-Q100 standard.
The SCC3000 components enable cost effective realization of the ESC product family of both standard and high-specification ESC with additional features. Pin-to-pin compatibility, together with the common SPI interface throughout the component family, reduces the engineering effort at the system supplier level, strengthening system robustness at the same time.
The SCC3000 targets safety critical applications and applications demanding high stability in tough environmental conditions, such as electronic stability control (ESC), headlight alignment, roll over and roll stability control, dynamic chassis control, lane keeping assistance (LKA), motion and navigation measurement, etc.
The SCC3000 product series includes SCC3134-D10, SCC3134-D16, SCC3234-D10, and SCC3334-D10, in which SCC3334-D10 is a five-axis gyro acceleration sensor, which can support 2-axis gyroscope (XZ) and 3-axis accelerometer (XYZ) with measuring ranges of 300dps, 6g and 15g, amplitude responses of 13 Hz, 20 Hz, 46 Hz, 200 Hz, and 300Hz, total offset of ±3°/s and ±70mg, and sensitivity of 80LSB/(°/s) and 3924LSB/g, and 1962LSB/g at 15g.
Conclusion
With the rapid development of technologies, cars are equipped with more and more active and passive safety systems. These systems usually have to detect the real-time acceleration and angular velocity of cars in order to make corresponding actions and responses. This requires the use of gyroscopes to achieve these functions. Murata's MEMS gyro acceleration sensor features high quality, high stability, and high accuracy, and will be the ideal choice for automotive-related applications.