Exact vehicle positioning is a major challenge for advanced driver assistance systems (ADAS) and autonomous vehicles. Future safety-critical driving functions also require functional safety down to the sensor layer. NAVENTIK PATHFINDER enables both - a more robust localization even in urban environments and the implementation of functional safety concepts through transparency of the signal pre-processing within the receiver framework.
A dedicated hardware GNSS receiver plus antenna results in a complex system architecture. An integrated supervision of the receiver performance is not possible.
Our software positioning engine is seamless integrated into the central sensor fusion platform. This approach leads to a simplified architecture and enables an integrated safety concept.
A key objective for GNSS-based positioning is to provide integrity while achieving robustness to multipath errors, interference and satellite malfunctions.
The heart of PATHFINDER's functional safety concept and an essential step towards certification according to ISO 26262 is the development of the protection level feature. To form a integrity monitoring concept for a protection level computation, two steps need to be taken:
One of the main advantages of the PATHFINDER GNSS software receiver compared to conventional hardware receivers is the ability to generate integrity data in real-time. Based on specific probabilistic algorithms for the error detection and statistical approximation, a probabilistic error assessment of a given position can be achieved. Erroneous measures that could lead to abnormal position errors can be detected and removed.
By adding vehicle motion and rotation data, the positioning engine PATHFINDER FUSION is able to to continuously compute the vehicles position, allowing the ADAS to engage an automated driving function in the case of high integrity along with given position. This approach is is valid for non-safety critical driving functions as well as for ADAS validation.
For safety critical driving functions of ADAS L3+, the position accuracy is required to be even more secure than the standard deviation measure by means of a data category able to derive position integrity at a higher level of reliability. Arising from the principles in aviation, the protection level definition is the “estimated upper bound of error between true position and the position estimate corresponding to an acceptable false alert probability", generated by PATHFINDER.
The protection level is defined as the upper bound of the positioning error.
The application rejects measurements whose protection level exceeds its alert limit .
Upper bound tends to get large, especially in urban areas.
NAVENTIK has employed a significant R&D effort into the development of the principles for the computation of the protection level. The key to derive a protection level is the deep understanding and statistic approximation of the true position and the position estimate:
The protection level will be computed based on the well-known error models of GNSS signals, the integration of certified and modern augmentation correction Services, the error models from specific IMU and the visual odometry input along with the motion models of vehicle. The underlying statistical principles are part of the main IP of NAVENTIK.
NAVENTIK has successfully developed all preconditions for the protection level computation. Based on the implemented development processes, the certification will be the next step. PATHFINDER software components will be qualified as a Safety Element out of Context for safety level ASIL-B according to ISO 26262. Furthermore, we are committed to the full qualification of a real time protection level for safety-of-live applications according ISO21448 (SOTIF).
Achieving that, PATHFINDER will be a disruptive product on the GNSS positioning market with the potential to permanently substitute GNSS chipsets as well as RTK / INS solutions for the upcoming ADAS L3+ and the validation of these system. Wow!
Safety Lifecycle. In order to implement a security concept for GNSS position data, the entire processing chain from the GNSS ground segment via satellites in space to the final position in a digital environmental model must be covered. This includes the explicit modeling and mitigation of all known sources of error. Some of the influences are related to signal propagation disturbances, others to errors inherent in the system. Most of them can be monitored by external service providers and integrity information must be evaluated in real time in the receiver. Our integrity goals regarding a safety-compliant are defined as follows:
Based on the principe "The position is within the described distribution model if the model is correct." PATHFINDER takes the following elements into account to maintain the integrity of the calculated position solution:
In short, PATHFINDER integrates all safety-relevant aspects of vehicle localization. All steps of signal processing are carefully reviewed so as not to lose or falsify any information relevant for the estimating a valid error budget. The PATHFINDER modules will be interfaced by an API tailored to your needs and requirements. As we aim to implement on your ECU or ADAS processor, we carefully develop according to automotive standards and will also comply with ISO 26262.