Replay and HIL AD Reference Architecture Example: Adaptive Cruise Control

Adaptive cruise control (ACC) is a driver-assistance function that offers an illustrative use case for the Replay and HIL AD Reference Architecture. ACC will be referenced as an example of how the Replay and HIL AD Reference Architecture could be used to build a test system to validate this functionality.

The resulting test system is based on PXI and Linux RT with all required hardware and software for controlling, configuring, communicating with, and powering the DUT. The test system accurately emulates the behavior of the sensors, communication buses, and I/O connected to the ADAS ECU and allows the ADAS ECU to be tested in a virtual environment. To create this test system, you must first understand the behavior of each sensor and connection to the ADAS ECU.

This implementation of ACC utilizes a combination of radar, lidar, and camera sensors that interact with the ADAS ECU to detect and react dynamically to obstacles in front of a vehicle while cruise control is enabled. The end result is that the vehicle attempts to maintain a specified speed but automatically accelerates or decelerates to maintain a safe following distance from any vehicles in the lane ahead. Refer to the following diagram representing a typical ACC implementation.

Figure 5. Representative ACC Implementation Diagram

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The ADAS ECU monitors the environment in front of the vehicle using radar, lidar, and camera sensors, which detect the presence and location of traffic in front of the vehicle. The ADAS ECU communicates with other ECUs in the vehicle to determine current vehicle speed and current cruise control settings set by the driver, as well as to command changes to the speed of the vehicle. The ADAS ECU also includes a diagnostic port and other connections used for non-ACC ADAS functions. The ADAS ECU is powered by a 12 V power supply. Refer to the following table for additional information about each of these connections.

Table 4. Communication Details for Representative ACC Use Case
Communication Type Communication Paths Communication Characteristics
CAN (dedicated port) Radar to ADAS ECU
  • On power-up, radar starts sending object lists as a series of CAN messages
  • Number of messages varies with number of objects
  • Complete list updated at 15 Hz
  • Radar is not synchronized to other devices
  • Status message sent to ADAS ECU every second, including the following parameters:
    • HW Fault (T/F)
    • Overtemperature (T/F)
CAN (shared port) ADAS ECU to powertrain ECU
  • Command message sent to powertrain ECU at 30 Hz, including the following parameters:
    • ACC enabled (T/F)
    • Throttle (0% to 100%)
    • Brake (0% to 100%)
  • Communication data is not synchronized to other communication with the ECU
Powertrain ECU to ADAS ECU
  • Status message sent to ACC ECU, including the following parameter:
    • Vehicle speed (-50 mph to 300 mph)
Driver settings from dash ECU to ADAS ECU
  • Settings message sent to ADAS ECU at 10 Hz, including the following parameters:
    • ACC enabled (T/F)
    • Target vehicle speed (0 mph to 200 mph)
    • Minimum following distance (10 ft to 150 ft)
  • Communication data is not synchronized to other communication with the ECU
GMSL Front camera to and from ADAS ECU
  • On power-up, camera is idle
  • ECU sends configuration information after power-up
  • ECU generates frame-sync pulses at 60 Hz
  • Camera returns an image after every pulse
  • Image size = 3480x2160 pixels
  • Image type = YUV422
  • ECU may send additional commands to adjust camera settings
Automotive Ethernet Lidar to and from ADAS ECU
  • On power-up, lidar is idle
  • ECU sends configuration information after power-up
  • ECU commands lidar to start sending data at 10 Hz
  • Lidar sends point cloud data at programmed rate
  • Lidar is not synchronized to other devices
1000Base-T XCP diagnostic port to and from debug device
  • Not used during normal vehicle operation
  • Provides diagnostic and development access to ECU
  • Used for tasks such as monitoring the state of the ECU, overriding variable values, or enabling validation of sub-systems
Power connection Power source to ADAS ECU
  • 12 V vehicle power supply
  • ECU begins operation shortly after application of power