read

Gather latest reading from robot sensor

Since R2022a

Syntax

[isUpdated,t,sensorReadings] = read(sensor)

Description

[isUpdated,t,sensorReadings] = read(sensor) gathers the simulated sensor output sensor readings from the latest update of the robot platform associated with the specified sensor sensor. The function returns an indicator isUpdated of whether the reading was updated at the simulation step in the scenario with timestamp t.

Examples

Create and Simulate Robot Scenario

Create a robot scenario.

scenario = robotScenario(UpdateRate=100,StopTime=1);

Add the ground plane and a box as meshes.

addMesh(scenario,"Plane",Size=[3 3],Color=[0.7 0.7 0.7]);
addMesh(scenario,"Box",Size=[0.5 0.5 0.5],Position=[0 0 0.25], ...
        Color=[0 1 0])

Create a waypoint trajectory for the robot platform using an ENU reference frame.

waypoint = [0 -1 0; 1 0 0; -1 1 0; 0 -1 0];
toa = linspace(0,1,length(waypoint));
traj = waypointTrajectory("Waypoints",waypoint, ...
                          "TimeOfArrival",toa, ...
                          "ReferenceFrame","ENU");

Create a rigidBodyTree object of the TurtleBot 3 Waffle Pi robot with loadrobot.

robotRBT = loadrobot("robotisTurtleBot3WafflePi");

Create a robot platform with trajectory.

platform = robotPlatform("TurtleBot",scenario, ...
                         BaseTrajectory=traj);

Set up platform mesh with the rigidBodyTree object.

updateMesh(platform,"RigidBodyTree",Object=robotRBT)

Create an INS sensor object and attach the sensor to the platform.

ins = robotSensor("INS",platform,insSensor("RollAccuracy",0), ...
                  UpdateRate=scenario.UpdateRate);

Visualize the scenario.

[ax,plotFrames] = show3D(scenario);
axis equal
hold on

In a loop, step through the trajectory to output the position, orientation, velocity, acceleration, and angular velocity.

count = 1;
while ~isDone(traj)
    [Position(count,:),Orientation(count,:),Velocity(count,:), ...
     Acceleration(count,:),AngularVelocity(count,:)] = traj();
    count = count+1;
end

Create a line plot for the trajectory. First create the plot with plot3, then manually modify the data source properties of the plot. This improves the performance of the plotting.

trajPlot = plot3(nan,nan,nan,"Color",[1 1 1],"LineWidth",2);
trajPlot.XDataSource = "Position(:,1)";
trajPlot.YDataSource = "Position(:,2)";
trajPlot.ZDataSource = "Position(:,3)";

Set up the simulation. Then, iterate through the positions and show the scene each time the INS sensor updates. Advance the scene, move the robot platform, and update the sensors.

setup(scenario)
for idx = 1:count-1
    % Read sensor readings.
    [isUpdated,insTimestamp(idx,1),sensorReadings(idx)] = read(ins);
    if isUpdated
        % Use fast update to move platform visualization frames.
        show3D(scenario,FastUpdate=true,Parent=ax);
        % Refresh all plot data and visualize.
        refreshdata
        drawnow limitrate
    end
    % Advance scenario simulation time.
    advance(scenario);
    % Update all sensors in the scene.
    updateSensors(scenario)
end
hold off

Input Arguments

sensor — Robot sensor added to platform in scenario

robotSensor object

Robot sensor added to platform in scenario, specified as a robotSensor object.

Output Arguments

isUpdated — Sensor reading update indicator

0 or false | 1 or true

Sensor reading update indicator, returned as a logical 0 (false) or 1 (true). If the sensor reading updated at the current simulation step, the function returns this argument as true.

Data Types: logical

t — Timestamp of generated sensor reading

scalar in seconds

Timestamp of the generated sensor reading, returned as a scalar in seconds.

Data Types: double

sensorReadings — Simulated sensor readings

gpsSensor output | insSensor output | robotLidarPointCloudGenerator output

Simulated sensor readings, which depends on the type of sensor specified in the sensor input argument. See the Usage syntax for the appropriate gpsSensor, insSensor, or robotLidarPointCloudGenerator System object™.

Version History

Introduced in R2022a