No moving for vehicles on SPH terrain

[Alex Lan]

Hi,

I defined a vehicle with two suspensions of simplified double wishbone using JSON, very similar to HMMWV. But the parameters of suspensions, steering and chassis were different from those of HMMWV. I tested the vehicle to follow a straight line on SCM terrain, reference to demo_VEH_HMMWV, and it worked well. Then I tested it with same configuration on the SPH terrain, reference to demo_VEH_SPHTerrain_WheeledVehicle. There were no moving of chassis, and the wheel seemed to rotated in place. Is there any problem for the vehicle with simplified double wishbone running on SPH terrain?
Regards.

[Radu Serban]

Alex, There’s no reason why a particular suspension subsystem will influence the vehicle-terrain interaction.  There must be something else that you are missing in your program.

Does demo_VEH_SPHTerrain_WheeledVehicle work fine for you?  A couple of days ago I modified that demo to include additional options for initializing the SPH terrain.  The original code generated a pretty large terrain patch and so was taking quite a bit to run.  The new version still has that option, but the default now is to create a smaller and coarser SPH terrain patch which runs quite a bit faster. Please make sure the demo works as expected (with the Polaris vehicle moving forward) and then see what it is that you are doing differently in your code.

 

--Radu

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[Alex Lan]

Thank you for your answer!
I found it was because the rear wheel easily got stuck in SPH terrain that may be different from SCM terrain. I used the path-follower driver. When the rear wheel got a kind of large sinkage, the axles gave rear wheel a larger torque and  gave front wheel a smaller torque, which makes the rear wheel sink more. I set the "Central Differential Locking Limit" as 2.0, but when the wheel got stuck, the difference of torque on the front and rear wheel can reach even 5.0. I want to give the front wheel more torque. Is there any problem or parameters that I can set to change the distribution of torques on the two axles?
regards.