The future of the automotive industry can be called autonomous driving. High precision position sensors for automobiles are enabling better and safer self-driving cars. IMU Sensors are used in the contemporary automobile designs particularly in the ADAS and the autonomous cars.
1. Basic application of inertial sensors
The accelerometer and angular velocity gyroscope act as the vehicle’s “brain wheel” to detect the vehicle’s speed. For example, the accelerometer can detect rapid vehicle deceleration. This will cause the airbag to deploy.
Vehicles use increasingly complex inertial sensors. (accelerometer and angular velocity gyroscope) to control stability to help prevent tipping or wheel slipping
2. Inertial Measurement Unit
Using a three-axis accelerometer in conjunction with a three-axis angular velocity gyroscope designed into an IMU, vehicle movement in all six axes (6 DOF) of the linear and rotational directions can be accurately detected.
The IMU can independently monitor the movement status of the vehicle. and find the exact location with an extended Kalman filter algorithm to reduce errors caused by temperature deviation
3. IMU and GPS Fusion
Advanced autonomous driving systems not only rely on IMUs, but also continuously update the location information of the vehicle by combining with sensors such as GPS, Lidar, and cameras. This integrated navigation system is called inertial navigation system (INS).
GPS can provide global positioning, and the positioning accuracy can reach 2-4 cm after error correction. However, the GPS update frequency is low, but the IMU can calculate the vehicle position in a short time when the GPS signal is lost (e.g., in the tunnels and near tall buildings). The calculation time is too long to lead to the accumulation of errors.
4. IMU Accuracy and Cost
Although military IMUs offer extremely high accuracy (within 10-30 cm of error), they are costly and unsuitable for the civilian market. In contrast, MEMS-based (Micro Electro-mechanical System) IMU sensors are suitable for consumer and industrial use.
As technology advances, future MEMS IMUs will have higher accuracy and meet the accuracy and reliability requirements required for fully autonomous driving.
5. Technical Challenges
When the IMU faces high instantaneous acceleration or vibration, the MEMS structure may have adhesion problems, which affects the stability of the sensor.
Moreover, there is a problem of low failure rates and long lifetime IMU senor manufacturers have to address, and although not as competitive as in civil applications the automotive market also has much higher density requirements.
Summary
Autonomous driving and vehicle safety cannot be properly implemented without the use of inertial sensors (IMUs). With the further advancing of sensing technology, the next generation of IMU will become more precise and stable, enabling the society’s ultimate dream-automated driving.