off_highway_uss

The off_highway_uss package provides a receiver node to receive and decode CAN frames of the Bosch Ultrasonic Sensor System (USS) Off-Highway into ROS messages - it implements an off_highway_can::Receiver. Furthermore, the package provides a sender node to encode and send needed USS input data as CAN frames - an implementation of an off_highway_can::Sender.

Further information on the Bosch USS Off-Highway, it's inputs, outputs and how they can be interpreted can be found in the corresponding Technical Customer Documentation (TCD) of the sensor system.

Supported devices

Further information: Ultrasonic system variants and sensors

Contact: off-highway.beg@bosch.com

Nodes

Receiver

The USS receiver decodes CAN frames into an object list and a direct echo list, manages the current lists and publishes them cyclically.

The parameter use_j1939 defines whether automotive CAN or J1939 messages are expected. J1939 support has the following limitations:

• A fixed source address for the USS ECU must be configured. The dynamic assignment of source addresses is not supported.
• The receiver expects the parameter group numbers (PGNs) to be arranged as in the default DBC. A rearrangement is only supported as a shift of the entire block. Moving individual PGNs is not supported. Be aware that the PGN is only bit 8 to 23 of the extended CAN ID.

All received messages are checked for their cyclic redundancy check (CRC), rolling message counter and age (message not older than parameter allowed_age). If any of these checks do not succeed the received message is not further processed and skipped.

The relevant USS CAN frame IDs to process (object_base_id, direct_echo_base_id, max_detection_range_id and info_id) are calculated from the id_offset (automotive CAN) or pgn_offset (J1939) parameter with constant offsets. It should correspond to the value configured in the USS ECU and needs to be adapted for the specific bus setup. When using J1939, the receiver also checks whether the source address contained in the message matches the value of the source_address parameter. If multiple USS systems need to be decoded on the same bus just launch multiple receiver nodes with individual id_offset (automotive CAN) or pgn_offset and source_address (J1939) parameters.

The object data is published as a list of objects or as a point cloud and contains up to 20 objects (sensor limit). Only valid objects in the list are published (type not TYPE_NONE). Line objects in the point cloud format are sampled between their first and second position into individual points based on the line_sample_distance parameter. If this parameter is zero, only the end points of the line segment are put in the point cloud.

An object CAN frame is multiplexed by the USS, so that the same CAN frame ID is used for two objects. Thus, for uniqueness, the id fields of an object in both published list formats are computed by adding the multiplexor value times ten to the the enumeration the CAN frame IDs starting from the object_base_id as zero. This results in an object id in the range [0, 20).

The direct echo data is published as a list of direct echos and contains up to 12 direct echos (fills up at start till one set is received). The echo's id field is the enumeration of the CAN frame IDs starting from the direct_echo_base_id as zero. This results in an echo id in the range [0, 12).

The echo data list is accompanied by the max_detection_range message, which contains the current maximum detection range for all 12 individual ultrasonic sensors as array.

If the receiver node does not receive anything within a configured period (parameter timeout), it will publish a diagnostic error on /diagnostics. Also, the sensor information CAN frame is published and checked as diagnostic status of the USS. On error, the node publishes a diagnostic error.

Subscribed Topics

• from_can_bus (can_msgs/Frame)
  • USS CAN frames to decode

Published Topics

• objects (off_highway_uss_msgs/Objects)
  • Update Rate: configurable with publish_frequency
  • Contains current object list of USS as custom message containing the same information as each object's CAN frame. Mapping to the respective CAN frame and multiplexor value is done via the id field.
• objects_pcl (sensor_msgs/PointCloud2)
  • Update Rate: configurable with publish_frequency
  • Contains current object list of USS as point cloud. Line objects are sampled with line_sample_distance to equidistant points along the first and second position. Mapping to the respective CAN frame and multiplexor value is done via the id field.
• direct_echos (off_highway_uss_msgs/DirectEchos)
  • Update Rate: configurable with publish_frequency
  • Contains current direct echo list of USS as custom message containing the same information as each echo's CAN frame. Mapping to the respective CAN frame is done via the id field.
• maximum_detection_range (off_highway_uss_msgs/MaxDetectionRange)
  • Update Rate: On each sensor maximum detection range CAN frame
  • Contains the current maximum detection range of USS as custom message containing the same information as the respective CAN frame.
• info (off_highway_uss_msgs/Information)
  • Update Rate: On each sensor information CAN frame
  • Contains current sensor information message containing the same information as the respective CAN frame.
• /diagnostics (diagnostic_msgs/DiagnosticArray)
  • Update Rate: On each sensor information CAN frame or if receiver timed out periodically with timeout period
  • Diagnostic status contains statuses from the latest received sensor information and timeout status.

Parameters

See receiver_params.yaml.

Sender

The USS sender listens for ROS ambient temperature messages as input and encodes and publishes these as CAN frame.

In the case that there is no ambient temperature reading available, the USS can be configured with a fixed value (see TCD) and this sender node is not needed.

The CAN temperature signal can only encode the range of [-40°C, 87°C], ROS messages containing temperature values outside of this range are discarded and not encoded / published. Furthermore, if the ROS temperature message is too old (parameter allowed_age) it is discarded, too.

The relevant USS CAN frame ID to publish the temperature is specified by the outside_temperature_id parameter. This parameter needs to correspond to the vehicle data ID for the specific bus setup. If multiple USS systems are connected on the same bus, a single USS sender is sufficient as long as these USS systems expect the vehicle data frame on the same ID (in contrast to multiple receivers).

If the sender node does not receive anything valid within a configured period (parameter timeout), it will publish a diagnostic error on /diagnostics.

Subscribed Topics

• temperature (sensor_msgs/Temperature)
  • Ambient temperature is sent to the USS for compensating readings

Published Topics

• to_can_bus (can_msgs/Frame)
  • Encoded USS CAN frames
• /diagnostics (diagnostic_msgs/DiagnosticArray)
  • Update Rate: 1 Hz or if sender timed out periodically with timeout period
  • Diagnostic status only contains timeout status

Parameters

See sender_params.yaml.

Launch files

• receiver.launch: Starts the receiver with the default parameters
• sender.launch: Starts the sender with the default parameters

Changelog for package off_highway_uss

0.5.1 (2024-03-27)

• Include what you use
• Remove unused variable
• Properly include rclcpp/executors.hpp when using spin_some
• Disable irrelevant warnings for Clang Anonymous structs are used in PCL for type punning: https://github.com/PointCloudLibrary/pcl/issues/2303 Subobject braces are not needed: https://bugs.llvm.org/show_bug.cgi?id=21629 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=25137
• Contributors: Ramon Wijnands, Robin Petereit