You find the source code for our examples in the software-folder:

C++

cd ~\dev\software\basic_circle_example\src

MATLAB

cd ~\dev\software\hlc\matlab\basic_circle_example

How the code works

In this example one vehicle drives in a circle which is not attached to the map. See the sourcecode for explicit documentation. This chapter only provides the theoretical background.

Initialisation

At first a DDS Writer for the RTI DDS Service is intialtized to ensure that position and speed will be sent to the simulation and the vehicle.

Giving direction and speed

Next points and speed of the vehicle are defined at each point for the entire trajectory. When you use v_x and v_y keep in mind that this is not the actual speed but the speed vector at your current location (remember that v_ges = sqrt(v_x^2 +v_y^2) as it is a vector). You use this vector to define the direction for your vehicle, so where it has to steer next:

While defining the speed vector also be aware that the tangent will fit with the vector/tangent from the previous point and that the shape of the curve is not only affected by the vector of the starting point but also of the vector at the end point/next starting point. It turns out that it is the easiest way to define your speed vector by drawing our shape first and define the signs of your vectors to ensure the right orientations. It is recommanded to always define a speed for both v_x and v_y, even if it is a small value, to ensure the right orientation of your vehicle. Last but not least remember that your are giving a trajectory to a physical system so sharp edges won't be possible.
The speed is given in m/s.

Segment duration

For the segment duration keep in mind that speed, time and waylength have to fit. Verify your speed/way/duration with v_ges =s_segment/t_{segmentduration}.

Sending the trajectory information to the vehicle

All data are sent to the vehicle using the writer-function from the beginning.

Matlab specific information

First steps - what the HLC scripts need to include

• Send a ReadySignal message after initialization - only the ID string matters, which must be of the form "hlc_" + vehicle_id, where the latter is the ID of the vehicle the HLC is responsible for
• Receive VehicleStateList messages, which include the current states and observations of the vehicle as well as the current time - this signal is supposed to be the start signal for the HLC, so computation should start using this data after the message was received. Make sure to ignore signals received during computation, if that takes longer than a single period
• Send vehicle command messages as a result of the communication including the vehicle ID to the Middleware, which propagates these to the vehicle
• React to stop signals sent by the LCC and propagated to the HLC by the Middleware
• Your function head may differ, but you must use varargin as your last parameter to pass vehicle IDs to your script. This allows you to define, for your script, which vehicle(s) it should be responsible for. Any previous parameters you define are your own 'custom' parameters and need to be specified as additional parameters in the Lab Control Centers' UI before starting your script (if you wish to start it using the UI).