ST’s 6-Axis Inertial Measurement Units Hit the Road
STMicroelectronics has released a new 6-axis inertial measurement unit (IMU) targeting automotive navigation and advanced driver assistance systems (ADAS).
STMicroelectronics has introduced an automotive 6-axis inertial measurement unit (IMU) that incorporates a 3-axis accelerometer and 3-axis gyroscope into a single module. ST designed the new module, the ASM330LHBG1, to provide critical vehicle motion data for automotive functional safety applications, including semi-autonomous driving, vehicle navigation, and advanced driver assistance (ADAS).
The ASM330LHBG1 can withstand extreme automotive environments.
The new IMU is ASIL-B compliant when used with ST’s certified software library and features a range of embedded digital capabilities, including a machine-learning core (MLC) and programmable finite state machines (FSM) for onboard data processing. The ASM330LHBG1 is AEC-Q100 Grade-1 qualified for automotive applications and has an extended operating temperature range to 125 °C that supports operation near the engine compartment or when exposed to direct sunlight.
The new module is pin-compatible with ST's prior IMU variants.
An Inertial Measurement Unit for Position Data
The ASM330LHBG1's combined 3-axis accelerometer and 3 axis-gyroscope allow the module to perform as an inertial measurement unit (IMU), measuring both speed (accelerometer) and angular rate (gyroscope) from a known point (fix) to estimate its location. In the nautical world, this is referred to as dead-reckoning, where sailors can use speed and direction to estimate their position in the ocean in the absence of visible aids to navigation (or GPS).
ASM330LHBG1 functional block diagram.
For automotive applications, the ASM330LHBG1 uses its own dead-reckoning algorithms embedded on-chip to provide precise location information for a vehicle when GPS or satellite navigation is not available. Sensor data from the IMU can also assist with Level 2 semi-autonomous driving and ADAS (radar, LiDAR, and cameras) applications that depend on accurate vehicle motion and position information.
The MEMS Sensors Behind the Scenes
At the core of the ASM330LHBG1 (datasheet linked) are the microelectromechanical systems (MEMS) sensing elements used to measure acceleration and angular rate. These 3-axis sensors are manufactured using ST’s proprietary micromachining processes. The accelerometer has full-scale acceleration ranges of ±2, ±4, ±8, and ±16 g, while the gyroscope has a wide angular rate range extending from ±125 to ±4000 degrees per second (dps). The sensors' wide range makes the IMU module adaptable to a wide range of automotive applications.
Sensors measure acceleration and angular rate.
A simple 14-lead LGA package (2.5 x 3.0 x 0.83 mm) accommodates the power supply connections (3.0 V nominal). A serial data interface communicates sensor data to the host processor, and pins communicate state machine-generated interrupt signals triggered by user-defined motion patterns.
Low-Power Signal Conditioning and ML Core
Embedded low-power functions in the ASM330LHGB1 include analog frontends and digital converters for the MEMS sensors, low-pass filtering, and data management blocks. A basic machine-learning core (MLC) is available for on-module processing and can help recognize user-defined data patterns to generate interrupts.
Selectable high-performance and low-power modes allow designers to trade off module power consumption with output data rates (ODR up to 1.6 kHz) and measurement resolution. With both the gyroscope and accelerometer in operation, the module nominally consumes 1.3 mA.
An onboard temperature sensor compensates sensor data based on characterized performance to negate any temperature-related offsets and maintain accuracy over the full operating temperature range.
Designed for Automotive Safety
The reliability of ADAS and navigation assist features can impact a vehicle's safe operation. Automotive Safety Integrity Level (ASIL) is a risk classification scheme (A to D, with D being the highest safety level) that helps define the safety requirements for these systems. Other vehicle systems that are classified as ASIL B include brake lights, rear cameras, and instrument clusters.
The ASM330LHGB1 is ASIL-B compliant when used in conjunction with a certified software library (ISO 26262:2018). ST’s ASIL-B library can interface two redundant IMUs with a host processor to accurately acquire data and communicate in accordance with ASIL-B requirements.
All images used courtesy of STMicroelectronics.
