Vehicle actor not despawning when specified an exit time

Hello,

I have written a code to ensure that the vehicle actor defined in am Automated Driving ToolBox scenario despawns as it reaches the end of the road and then reppears on the satrt of the road to show a continuous traffci flow. Unfortuntely, when I sepcify the vehicle exit Time as carLane3(ii).ExitTime = scenario.SimulationTime; it doesn't seem to work and the vehicle does not despawn. Here is a snippet of the code which moves the vehicle and despawns it if it reaches the end of the road

for ii = 1:length(carLane1)

closestGridPoint = norm(abs(carLane1(ii).Position(2))-x_grid_aug);

[Min,idx] = min(closestGridPoint);

carSpeed = VCurrent(1,idx);

carLane1(ii).Position = carLane1(ii).Position-[0 carSpeed 0]*del_T*iter_ct;

if((norm(carLane1(ii).Position(2)-endPointLane1(2))<0.3||...

carLane1(ii).Position(2)<-Length))

carLane1(ii).ExitTime = scenario.SimulationTime;

despawnIDLane1 = [despawnIDLane1,ii];

end

end

[Ram Prasanth]

Hello, May i Know What is the Version of Matlab are you using?

clc, version

Type this in your Command window.

because my suspect is spawning and despawning works only from R2020b. Might be a reason too and Exit time and Entry time is used until R2020a

Documentation reference - Add vehicle to driving scenario - MATLAB vehicle - MathWorks France

[Abhishek Kashyap]

My version is 2024a

[Abhishek Kashyap]

It seems that the despawning only works when you specify the trajectory of the vehicle. But I want to assign an instantaneous velocity to the cars at each sample time so I can't assign a trajectory to it. Is there a work around for it?

Answer 1

[Ayush]

Hi Abhishek,

From the code that you have written using the Automated Driving Toolbox in MATLAB R2024a, it seems that you have focused on updating the vehicle positions while tracking their exit times when they are reaching the end of the road as per your expectations.

Although this approach is in the right direction, an additional emphasis on the vehicle simulation environment (basically the looping mechanism) as well as the despawning and respawning mechanisms to ensure the desired result. Here are some possible modifications to the provided code for the same:

1. Identifying the vehicles that reach the end of the road and marking their index in the “despawnIDLane1” array to allow for batch processing of vehicles that are to be respawned for efficiency within simulation. Here is a code snippet for your reference:

% Check if the car has reached the end of the lane and update ExitTime
        if carLane1(ii).Position(2) <= endPointLane(2) && isinf(carLane1(ii).ExitTime)
            carLane1(ii).ExitTime = scenarioSimulationTime;
            despawnIDLane1 = [despawnIDLane1, ii]; % Mark for despawn
        end

2. Ensuring dynamic respawn logic where instead of instantaneous update of position and exit time, the respawning mechanism is separated in a distinct phase (new loop) to offer finer control over simulation. Each vehicle in despawnIDLane1 is reset to its starting position and “ExitTime” is set to “Inf”. Here is a code snippet for your reference:

% Process despawning and respawning
    for idx = despawnIDLane1
        % Respawn logic: reset position and ExitTime for despawned cars
        carLane1(idx).Position = startPointLane; % Reset position to start
        carLane1(idx).ExitTime = Inf; % Reset ExitTime indicating they are back in the simulation
    end        

3. Resetting the state after each despawn and respawn cycle is crucial to avoid any duplication in handling vehicle states and its visualisations. This is done by clearing the “despawnIDLane1” array. Here is a code snippet for your reference:

    despawnIDLane1 = []; % Clear despawn list for the next iteration
    
    % Update simulation time
    scenarioSimulationTime = scenarioSimulationTime + del_T;

Additionally, I have attached an example video that shows the result captured in my system from the above modifications.

Hope this helps!