Tracking vehicle movement in 3 dimensions



Why vehicle telematics systems need more than just satellites

Many vehicle systems rely on accurate satellite positioning as a basis for their correct operation. Navigation, tracking, emergency call, anti-theft, road-pricing and insurance systems all depend on uninterrupted positioning in order to deliver a dependable service.

In reality, availability of global positioning satellite signals is intermittent or absent. Especially in tunnels, urban canyons, park houses and multi-level highways, relying on GNSS satellites alone can result in a failure to establish a position, or even worse, a wrong position may be reported.

3-Dimensional Automotive Dead Reckoning (“3D ADR”) aids traditional Global Navigation Satellite System (GNSS) navigation via intelligent algorithms based on distance, direction and elevation changes made during satellite signal interruption. 3D ADR GNSS blends satellite navigation data with individual wheel speed, gyroscope and accelerometer information to deliver accurate positioning regardless of changes in a vehicle’s speed, heading or elevation, even when satellite signals are partially or completely blocked.

A Solution: GNSS positioning enhanced with 3D Dead Reckoning

ublox-speed

To solve these problems, u-blox has integrated 3D ADR functionality into its GNSS satellite receiver chip technology. Based on advanced “Sensor Fusion Dead Reckoning” technology, the 3D ADR solution maintains accurate positioning while travelling through regions of poor or no GNSS reception. Based on the last known position, vehicle sensors (typically wheel speed sensor, gyroscope and accelerometer) feed information to the GNSS receiver indicating how far and in what direction, as well as what altitude change a vehicle has experienced based on wheel tick and vehicle pitch.

sensing-direction

Sensing distance traveled

There are a variety of sensor techniques for detecting distance traveled. Typically a direct connection to the vehicle’s odometer (wheel tick) is enough.

Sensing direction

Dead Reckoning in a 2 dimensional plane is achieved by measurements reported by a yaw rate sensor gyroscope. The gyro measures the vehicle’s rotation rate along the Z axis. By combining rotation rate and distance travelled, Dead Reckoning is possible through curves.

Sensing changes in altitude

sensing-altitude

Gravity and vehicle accelerations information is gathered from three accelerometers placed in an orthogonal configuration. Combined with information about vehicle heading, any changes in the pitch of the vehicle can be calculated, for instance when climbing a ramp within a park house. Combined with distance measurement, change in altitude can be calculated.

A 3D ADR solution

u-blox’ 3D ADR is a semiconductor solution based on the fusion of sensor data with GNSS satellite data. Based on the Kalman Filter, a mathematical concept first published in 1960 by Hungarian-American mathematician, Rudolf E. Kalman, the concept is widely used in control systems, avionics, and space vehicles. The filter is very powerful and able to estimate present and future states of a system, even when the precise nature of the system is unknown.

driving
3D Dead Reckoning GNSS extends navigation to areas without satellite reception such as tunnels and park houses, while boosting accuracy along multi-level roads and urban canyons

In the case of u-blox’ implementation, a tightly-coupled Kalman filter algorithm is programmed in the GNSS receiver chip to determine vehicle location based on weighted averages of multiple sensor data input provided by the GNSS receiver, wheel-tick and gyroscope and accelerometers. The result is an estimated position that lies in-between the predicted and measured location that is far more accurate than if either methods were used alone. This process is repeated iteratively, with the new estimate used in the following calculation.

During times of good GNSS signal reception, the measurements from the vehicle sensors are constantly calibrated. If later a situation with bad or no GNSS signals is encountered, the solution continues to provide a highly accurate location based on the vehicle sensors’ inputs.

Ideal for first-mount navigation systems, u-blox’ 3D ADR Solution blends data from GNSS satellites with wheel tick, gyroscope and accelerometer information available from the vehicle CAN bus. Making use of the data available from the vehicle data bus brings cost savings; no additional sensors are required to implement Dead Reckoning. The solution runs entirely on the u blox GNSS receiver chip, the UBX-M8030-Kx-DR, and is a highly-accurate solution for car navigation and vehicle telematics systems, regardless of satellite visibility.

The solution requires minimum pre-configuration, and after initial set-up remains permanently calibrated.

Benefits of the 3D ADR solution:

  • Suitable not only for car navigation, but for many other car telematics applications such as eCall, pay-as-you-drive insurance, road-pricing, and stolen vehicle tracking
  • Able to track all visible GPS, GLONASS and BeiDou GNSS satellites in operation, as well as concurrent operation (GPS+GLONASS, GPS+BeiDou, GLONASS+BeiDou)

Reduced hardware costs

  • Utilizes sensor data taken directly from the vehicle bus
  • Supports high-end (wheel tick + gyro + accelerometer) to low-end, low-cost (wheel tick only) configurations
  • Minimal host processing required to execute Dead Reckoning
  • Automatically adapts to sensor head unit misalignment via software calibration
  • Standard and automotive grades

Flexible implementation

  • Supports various sensor configurations
  • Easily supports vehicle variants
  • Rich set of communication interfaces (I2C, SPI, UART, USB)
  • Self-calibrating, both initially and on a continuously to compensate for sensor aging and temperature affects
  • Based on external flash allowing for future improvements and updates to adapt to new GNSS systems (e.g. Galileo)
  • Embedded map-matching input to further refine navigation performance

Simple integration

  • Easy testing
  • Simple and modular production set-up: needs only vehicle parameters
  • Minimal eBOM

Industry proven

  • Successfully deployed by multiple major car manufacturers

For a 2-minute video demonstration of 3D Automotive Dead Reckoning, see the YouTube video located online at:

www.youtube.com/watch?v=ykR0TWL-_oA

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