sensor_interface.md

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• Wiki | Tutorials | Sensor Interface
• Prerequisites
• Cameras and Sensors in ARIAC 2021
  • Break Beam Sensor
    • Reading Data
    • Adding Sensor
  • Proximity Sensor
    • Reading Data
    • Adding Sensor
  • Laser Profiler
    • Reading Data
    • Adding Sensor
  • Depth Camera
    • Reading Data
    • Adding Camera
  • RGBD Camera
    • Reading Data
    • Adding Camera
  • Logical Camera
    • Reading Data
    • Adding Camera
  • Quality Control Sensor
  • Camera Mounted on the Robot

Wiki | Tutorials | Sensor Interface

The purpose of this tutorial is to introduce you to the sensors available to you in the Agile Robotics for Industrial Automation Competition (ARIAC) and how to interface with them from the command-line. The discussion in this tutorial uses the sensors defined in sample_user_config

Prerequisites

You should have already completed the GEAR interface tutorial.

Cameras and Sensors in ARIAC 2021

As described in the competition specifications, there are sensors available for you to place in the environment. How you can select which sensors to use is covered in the competition configuration specifications.

To start with, launch ARIAC with a sample workcell environment configuration that contains an arm and some sensors in various locations:

roslaunch nist_gear sample_environment.launch

Break Beam Sensor

• This is a simulated photoelectric sensor, such as the Sick W9L-3.
• This sensor has a detection range of 1 meter and the binary output will tell you whether there is an object crossing the beam.
• Cost: $100

Reading Data

• There are two ROS topics that show the output of the sensor:

  • /ariac/{sensor_name}
  • /ariac/{sensor_name}_change

• An osrf_gear/Proximity message is periodically published on topic /ariac/{sensor_name}.

• Run this command to see the message on the command line:

rostopic echo /ariac/breakbeam_0

• Alternatively, you could subscribe to the /ariac/{sensor_name}_change which will only show one message per transition from object not detected to object detected or vice verse.
• Run this command to see the messages on the command line:

rostopic echo /ariac/breakbeam_0_change

Adding Sensor

• Here is an example of adding a break beam sensor to your configuration file:

  breakbeam_0:
    type: break_beam
    pose:
      xyz: [-0.004795, 4.492549, 0.879306]
      rpy: [0, 0, -1.557900]

Proximity Sensor

• This is a simulated ultrasound proximity sensor such as the SU2-A0-0A.
• This sensor has a detection range of ~0.15 meters and the output will tell you how far an object is from the sensor.
• Cost: $100

Reading Data

• The ROS topic /ariac/{sensor_name} publishes the data as sensor_msgs/Range.
• Run this command to see the proximity sensor from the example world on the command line:

rostopic echo /ariac/proximity_sensor_0

• The proximity sensor can be visualized in RViz using the Range display.
• It helps to disable or decrease the marker scale on the TF display to see the cone of the range sensor in RViz.

Adding Sensor

• Here is an example of adding a proximity sensor to your configuration file:

  proximity_sensor_0:
    type: proximity_sensor
    pose:
      xyz: [0, 2.840000, 0.970000]
      rpy: [1.570796, 0.524365, 1.570796]

Laser Profiler

• This is a simulated 3D laser profiler such as the Cognex DS1300.
• The output of the sensor is an array of ranges and intensities.
• The size of the array is equal to the number of beams in the sensor.
• The maximum range of each beam is ~0.725m.
• Cost: $100

Reading Data

• The output of the sensor is periodically published on the topic /ariac/{sensor_name} as a sensor_msgs/LaserScan.
• Run this command to see the output on the command line:

rostopic echo /ariac/laser_profiler_0

• This can be visualized in RViz by adding a LaserScan display.
• There is an offset between the position of the laser profiler and the origin of the data.
• The position of the laser profiler is in a tf frame named {sensor_name}_frame, while the origin of the data is in a frame named {sensor_name}_laser_source_frame.

Adding Sensor

• Here is an example of adding a laser profiler to your configuration file:

  laser_profiler_0:
    type: laser_profiler
    pose:
      xyz: [0., 1.486, 1.526]
      rpy: ['pi/2', 'pi/2', 0]

Depth Camera

• This is a simulated time-of-flight depth camera such as the Swissranger SR4000.
• The output of the sensor is sensor_msgs/Pointcloud
• Cost: $200

Reading Data

• Because of the large amount of data being published, if you want to echo the sensor message you probably want to use --noarr to suppress the data values on the command line:

rostopic echo /ariac/depth_camera_1/depth/image_raw --noarr

• Pointclouds can be visualized in RViz using the PointCloud display.

Adding Camera

• Here is an example of adding a depth camera to your configuration file:

  depth_camera_0:
    type: depth_camera
    pose:
      xyz: [3.082385, 1.750927, 1.82]
      rpy: [0, 'pi/2', 0]

RGBD Camera

• This is a simulated time-of-flight depth camera such as the Swissranger SR4000.
• The output of the sensor is sensor_msgs/Pointcloud and sensor_msgs/Image.
• Cost: $500

Reading Data

• Because of the large amount of data being published, if you want to echo the sensor message you probably want to use --noarr to suppress the data values on the command line:

rostopic echo /ariac/rgbd_camera_1/depth/image_raw --noarr

rostopic echo /ariac/rgbd_camera_1/ir/image_raw --noarr

• Point clouds can be visualized in RViz using the PointCloud display.
• Images can be visualized in RViz using the Image display.

Adding Camera

• Here is an example of adding a RGBD camera to your configuration file:

rgbd_camera_0:
    type: rgbd_camera
    pose:
      xyz: [3.082385, 1.750927, 1.82]
      rpy: [0, 'pi', 0]

Logical Camera

• This is a simulated camera with a built-in object classification and localization system.
• The sensor reports the position and orientation of the camera in the world, as well as a collection of the objects detected within its frustum.
• The camera reports an object's type and pose from the camera reference frame as an osrf_gear/LogicalCameraImage message.
• Cost: $500

Reading Data

• In the sample environment there is a logical camera above one of the bins.
• Run the following command to see the output of the logical camera:

rostopic echo /ariac/logical_camera_0

• Logical cameras also publish tf transforms.

• Use the TF2 library to calculate the pose of the products detected by the logical cameras in the world frame (see http://wiki.ros.org/tf2).

• Here is an example using TF2 command-line tools to get a the pose of a part detected by a logical camera in world frame.

• Note that the frame of the detected products is prefixed by the name of the camera that provides the transform, so if multiple cameras see the same product they will publish transforms with different frame names.

rosrun tf tf_echo world logical_camera_0_assembly_pump_blue_2_frame

At time 82.601
- Translation: [-1.798, 3.280, 0.784]
- Rotation: in Quaternion [0.008, -0.008, 0.001, 1.000]
            in RPY (radian) [0.017, -0.017, 0.003]
            in RPY (degree) [0.967, -0.975, 0.153]

For more information on working with TF frames programmatically see the tf2 tutorials.

Note that GEAR uses tf2_msgs and not the deprecated tf_msgs. Accordingly, you should use the tf2 package instead of tf.

Adding Camera

• Here is an example of adding a logical camera to your configuration file:

  logical_camera_0:
    type: logical_camera
    pose:
      xyz: [-2.515033, 2.925223, 1.82]
      rpy: [-1.570796, 1.570796, 0]

Quality Control Sensor

• This is a simulated sensor that reports the pose of the sensor itself in the world frame and the pose of faulty parts (non-faulty parts are not reported) in the sensor frame.

• There are 4 quality control sensors in the environment (1 above each AGV).

• Locations of quality control sensors are set and competitors cannot change those locations.

• Run the following command to see the output of the sensors:

$ rostopic echo /ariac/quality_control_sensor_1
$ rostopic echo /ariac/quality_control_sensor_2
$ rostopic echo /ariac/quality_control_sensor_3
$ rostopic echo /ariac/quality_control_sensor_4

Camera Mounted on the Robot

• Cost: $600

This depth camera is located on the torso tray and can be enabled (enable: true) or disabled (enable: false) using the following code snippet in the user configuration file (see sample_user_config.yaml):

robot_camera:
  enable: true

Competitors can see the view from this camera in RViz.

$ roslaunch nist_gear sample_environment.launch
$ rosrun rviz rviz

Then:

• File->Open Config
• Navigate to ariac.rviz located in nist_gear/rviz
• Make sure the box for Image is checked.

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