Tutorial: Creating a Vehicle with Modular Vehicle Systems

Select Mechanism in the Explorer panel, then either:

• Press F2 for editing mode, edit the name to Car and press Enter to confirm.

• Click on the Name field at the top of the Properties panel at the right of the screen, change the name in the dialog box, and press Enter.

From the Home page, click Open and select the Car - Hatchback.vxgraphicgallery file located in the Graphics subfolder of the folder mentioned above. Save As a copy of the file in your working folding.

Switch back to your mechanism's tab.

Select Graphics in the Toolbox.

Double-click Galleries From Files....

In the resulting panel, select Car - Hatchback and click Ok. (Since you opened the Car Graphics Gallery in the previous step and have the tab open, it will automatically be shown in the Opened Resources section of the Add Graphics Gallery dialog box.)

In the Explorer panel, the 3D model is located within a Graphics Gallery than can be expanded via the small triangle on the left. It contains the 3D model and all its associated files (e.g., textures).

NOTE: The x axis is the forward direction of the vehicle. This is the standard, and all vehicle galleries must follow this convention.

NOTE: You can see the various files but cannot change them. To do so, the Graphics Gallery must be opened in a separate window. Leave this aside for now.

You should now see the car model in the centre of the viewport. Follow the next link for more information on how to navigate in the 3D Vies, Using the 3D View .

Select Basics in the Toolbox. Double-click Empty Assembly to add it.

Right-click on the Car Hatchback > Body graphics node in the Graphics Gallery and click Create Part... to create a part in the assembly (this will be the body for the vehicle).

You can now save the mechanism file by clicking Save.

In the resulting browser window, find the desired destination folder, and click Save.

Right-click on the Body part that was added to the Assembly and select Create  Collision Geometry > Convex Mesh....Enter Wheel.* in the Excluded Graphics Nodes field so the geometry is created for the body only, not the wheels.

In the resulting panel, click Ok to create the collision geometry. In the Explorer panel, Double-click on Assembly to open it in a tab.

Click on ConvexMesh_Body. In its Properties panel, select the material Chassis from the dropdown of the Material field.

Click on the Body part in the Explorer panel. In the Properties panel, under the Parameters tab, set the mass to 1220 kg.

Calculate the inertia tensor with the Compute inertia and COM button.

Right-click the Body part in the Explorer panel and select Insert Attachment Point.

Rename the attachment point Body [AP] to match the standard naming convention used in modular vehicle.

Save and close the assembly.

Save and close the Assembly tab.

Test the mechanism to see the vehicle chassis drop to the ground.

Select Basics from the Toolbox.

Double-click Assemblies from Files.

Click the Browse button and navigate to the FWD folder of the Topology directory listed above.

Select the FWD.vxassembly file and click Open.

If the exact wheel positions are known, they can be directly entered in the Component Configuration. In this case, they can be read from the graphics gallery.

In the Explorer window, click on the wheel node in gallery at Car Hatchback → Body → Wheel FL.

In the Properties window, look at the Outputs -> World Transform field. The top row of values are the (x, y, z) position of the wheel: (1.177, 0.765, 0.336)

Note the same values for the Wheel RL wheel. All are the same except the x value: -1.436

Navigate to the Component Configuration interface of the FWD sub-assembly.

The Wheel Position Front field corresponds to the x position of the front wheels, which was read in the previous step: 1.177

The Wheel Position Rear field corresponds to the x position of the rear wheels: -1.436

The Wheel Spacing field is the width between wheels, which is double the y position of the wheels: 0.765 * 2 = 1.53

The wheel height is the z position of the wheels: 0.336

With these values set, the centres of the collision geometries of the wheels should now match the gallery.

Start the simulation.

Try dragging the vehicle around, and notice that the wheels are locked.

This is caused by the wheels colliding with the body of the vehicle (activate the contact display Shift+C).

Stop the simulation.

In its Properties panel, create a new Collision Detection Rule by clicking on Add Rule.

In the new rule, drag the Assembly to one side, and the FWD sub-assembly to the other.

Ensure that Collide is not clicked, so that there is no collision between the Assembly and the FWD.

Start the simulation.

Try dragging the vehicle around, and notice that the wheels now roll freely.

Stop the simulation.

Note the Skin connection container that was created when the body part was created.

Double click the Skin container to see a graph of connections between parts and graphics nodes.

Click on the FWD -> Part Transforms interface. This has fields that output the current transform for each part in the vehicle sub-assembly.

Drag each of the four Wheel Transform fields into the graph window. These correspond to the four wheels: front left (FL), front right (FR), rear left (RL) and rear right (RR).

Expand the gallery to see the four wheel nodes in Car Hatchback -> Body -> Wheel FL.

Click on each of the wheel nodes and drag the Parent Transform field to the yellow circle of the corresponding Wheel Transform in the graph.

This creates connections that send the live values of the transforms of each of the wheels to the nodes of the graphics gallery, so they move with the physics simulation.

Start the simulation.

Try dragging the vehicle around, and notice that the wheel graphics now correctly roll with the parts.

Stop the simulation.

Two tables in the sample vehicle will be used for this tutorial.

Copy the two .csv files from the Tables subfolder of the Car - Hatchback sample directory into your own vehicle directory.

Click on the Engine Tuning interface in the FWD sub-assembly

The Torque Table needs to be provided for every vehicle. This is a single curve of torque as a function of engine RPM. The curve can be many points for smoother operation, or can be as little as two points (such as max torque and max power) if that all that's available.

Click on the ... button of the Torque Table parameter.

Choose the Engine Torque Table.csv file that was previously copied into your user directory.

The Idle RPM parameter should match the stable RPM of the vehicle when in neutral and no throttle is applied.

Set the value to 800.

Click on the Coupling Tuning interface.

The Stall RPM and Stall Torque determine the point at which the torque converter will fully couple the engine to the transmission.

In general, this will be near the maximum torque point of the engine curve.

For this vehicle, set the Stall RPM to 2100 and the Stall Torque to 240.

These correspond to the gear ratios of the transmission.

Click on the Transmission Tuning interface.

Click on the ... button of the Gear Ratio Table parameter.

Choose the Automatic Transmission Ratios.csv file that was previously copied into your user directory.

There are several fields that determine the automatic shifting behaviour of the transmission, which are described in this section of the documentation.

In this case, we only need to set the Shift Scale field to match the maximum RPM of the engine: 6000.

When set this way, the Shift Up and Shift Down values will be scaled to shift at a given fraction of the maximum RPM.

Click on the Wheel Front Tuning interface, then control-click on the Wheel Rear Tuning interface to select and edit both at the same time.

Set the Radius and Width to match the size of the wheel: Radius = 0.337, Width = 0.225

Note that the wheel collision geometries now match the size of the graphical wheel.

Select the Coulomb tire type, then select the Name property, type "Pavement - Default" and press enter.

Enter the values in the Inputs and Rolling Resistance properties as seen in the screen capture.

This will define the behavior of the wheel to be equivalent to rubber on pavement.

In the Ground Materials section, click the + button to add a ground type, and select default in the field.

This contact model will be used any time the wheel is touching a collision geometry with a material listed in this Ground Materials list.

'default' is a special value that means this model will be used for all materials that are not otherwise defined in other Time Models.

Select the Wheel Front Tuning interface in the FWD sub-assembly - > Wheel Front Tuning.

Drag the Tire Type object from the Explorer panel to the Tire Type field of the Properties panel.

Repeat for the Wheel Rear Tuning interface.

The wheel components provide an interface to test and debug that the wheel models are functioning correctly.

Navigate to the wheel component in FWD - > Components - > Wheel FL - > Wheel Contact.

Start the simulation.

Verify that the Tire Model Name output shows "Tire Type / Pavement - Default", which indicates that our tire model is being used correctly.

Note that there are many details about the current state of the tire type shown in this interface.

Stop the simulation.

From the Toolbox, choose the Simulation category.

Drag a VHL interface from the Toolbox into the Explorer tree just above the Car Hatchback gallery.

This places the interface at the top of the explorer tree so it is the first thing seen when using the vehicle in a scene.

When adding the VHL Interface, the Interface Editor opens in the main window.

In the Explorer tree, click on the vehicle control interface in the FWD sub-assembly - > Vehicle Control.

Click on the Engine Running input in the Properties panel, then shift-click on Gear to select all the input fields.

Drag the fields to the Inputs row of the Interface Editor panel.

Do the same with the Outputs by selecting all of them and dragging them to the Outputs row of the Interface Editor panel.

Close the Interface Editor by clicking the small x on the tab at the top of the Interface Editor panel.

Click on the Interface in the Explorer tree and note that it now shows all of the properties needed to control the vehicle, and these will be visible and accessible from the top of the Explorer tree for this mechanism.

Start the simulation.

Click on the Interface object in the Explorer tree.

In the Properties panel, click on Engine Running to start the engine.

Set the Gear to 6 to engage the transmission.

Set values in the Throttle, Brake, and Steering to drive the vehicle.

Stop the simulation.