Traffic Sign Recognition: Notes
The Traffic Sign Recognition (TSR) system uses camera traffic sign information and map data information to determine the unconditioned speed limit for the current driving scenario and displaying this speed limit information to the customer. In certain use-case scenarios, the TSR system provides supplementary information relative to conditioned speed limits (e.g., speed limit under specific weather conditions, time, etc.). In addition, the TSR system will provide indications to the customer regarding the presence of overtaking ban (i.e., no passing) signs.
The TSR system provides a visual warning indication when the customers vehicle speed exceeds the unconditioned speed limit. The customer is capable of enabling and disabling the TSR system through the customer settings menu in the DSM.
The TSR system performs the following:
- Correctly operate in any country or region specified by the product grid.
- Provide the correct sign information in the case of either a fixed or variable speed limit.
- Provide the correct information in the case of either a permanent or temporary speed limit.
- If there is lane-specific speed limits, the system will only provide the traffic sign information relative to the lane in which the host vehicle is traveling.
The TSR system will ignore the following:
- Lane-specific speed limits that do not apply to the lane in which the host vehicle is traveling.
- Radar speed displays which reflect the current speed of the host vehicle or other vehicles.
- Advisory (i.e. recommended) speed signs.
- Minimum speed limit signs.
- Traffic signs not related to the path of the host vehicle (e.g. traffic sign posted on exit or parallel roads).
- Traffic signs embedded into a non-relevant traffic sign.
The LRCF is used to perform the following functions in the TSR system:
- Detect the following primary traffic signs, defined as signs whose meaning and validity are exhaustively described by the sign itself:
- Speed limits (i.e. both unconditioned and supplementary).
- End of speed limit.
- No passing zone.
- End of no passing zone.
- Detect the following additional signs, defined as signs which indicate the validity of the primary signs they are linked with:
- Restrictions for environmental conditions (e.g. snow, rain, fog, etc.).
- Restriction for end of limit.
- Restriction for time.
- Validity at night only.
- Other types (e.g., hazardous materials, arrows, exit, etc.).
- Provide the information specified above internally to the CADM by using an internal connection.
The CADM will perform the following functions in the TSR system:
- Determine the validity of the traffic signs detected by the LRCF according to:
- The detection of speed limit start/end signs.
- The physical road type.
- The time and/or the distance traveled relative to each traffic sign.
- Determine the most reliable information any time new information is provided by the LRCF and the map data:
- The unconditioned speed limit.
- The presence of a supplementary speed limit with its restriction type.
- The presence of no passing zones.
- Provide all the necessary information for visualization to the IPC.
The TSR system operates when the ignition is in the RUN or START position assuming that the vehicle PROXI identifies that the TSR system is equipped.
The CADM combines the LRCF input with the map data inputs to perform the camera/map data fusion and arbitration process. The map data continuously monitors the vehicle position and provides the information related to its path as long as the GPS signal and the map data are available. If there is a contradiction between the camera and map data inputs, the CADM performs an arbitration and priority logic process to determine the best course of action.
OPERATION
The BCM is responsible for multiple outputs to the CADM to assist in TSR operation. The BCM is also responsible for performing gateway functions for several bus networks in order to facilitate TSR communication.
When the ignition is in the RUN or START position, the CADM is responsible for operating the TSR system. It receives several inputs to help determine the vehicle and its surrounding and sends multiple outputs in order to drive the TSR system. Some of the inputs are used to determine the conditions that the vehicle is operating such as:
- Front wiper signal from the BCM to determine whether or not the front wipers are in the parked position.
- External temperature signal from the BCM to determine whether the vehicle is driving in snow or rain weather conditions.
- Ride height information from the Air Suspension Control Module (ASCM) to select the appropriate TSR calibration that compensate for ride height adjustments.
The DSM contains the menu options and the ON/OFF customer interface for the TSR system. When the DSM menu selections are made, the DSM by way of the SGW sends the requests to the CADM for processing.
When the TSR system is ON or OFF, the IPC receives several inputs from the CADM to determine the display to be shown to the customer. This information is continuously updated by inputs from the CADM. The CADM also drives the warning system, audible and visual, through the IPC to alert the driver.
The LRCF is wired directly to the CADM and is used for detecting and processing the road signs that it identifies and sends provides the CADM with the sign detail for the CADM to process.
The SGW is a gateway between the DSM and the CADM. Signals to and from the DSM pass through the SGW for gating and security purposes.