Shubhankar,

There is no “API” for that. You will need to implement your own template for a 
custom driveline that has the desired behavior.  You can look at the ones 
already available in Chrono.

I am not sure what you mean by “pinning the wheels on the same side”.  If you 
mean enforcing that they always have the same angular velocity, then you 
probably need to design a mechanism that enforces that.

But at the end of the day, you have to distribute the torque coming from the 
powertrain to all wheels.   A template such as ChShaftsDriveline4WD 
accomplishes that through a mechanism constructed with Chrono’s 1D shaft 
elements.  A template such as ChSimpleDriveline does that by splitting the 
torque and applying it directly to the 4 wheel axles (front-left, front-right, 
rear-left, rear-right).

I suggest you start with something similar to ChSimpleDriveline and simply 
change the logic for the torque splitting (so that you apply the same torque to 
both left wheels and to both right wheels, with a left/right split based upon 
the steering input).  You would do that in your override of the Synchronize 
method.

--Radu

From: [email protected] <[email protected]> On Behalf 
Of Shubhankar Kulkarni
Sent: Friday, July 29, 2022 8:36 PM
To: ProjectChrono <[email protected]>
Subject: Re: [chrono] Skid steer simulation

Hello Radu,

I have implemented a class with the appropriate suspension and no steering. 
Your code is helping to get the steering inputs without a steering system being 
in place.
However, I am no sure as how to implement a custom driveline that will pin the 
wheels on the same side and apply different torques on the left and right 
sides. Could you please point me to the reference containing the appropriate 
APIs?

--Shubhankar

On Thursday, June 2, 2022 at 8:07:01 AM UTC-4 Radu Serban wrote:
Shubhankar,

The latest code in the ‘develop’ branch of the GitHub repository now passes all 
driver control inputs (steering, throttle, braking) to various vehicle 
subsystems.  In particular, these are also passed to the Synchronize() method 
of ChDrivelineWV.  To implement a skid steer vehicle, build a vehicle with no 
steering mechanism and implement a custom driveline which applies different 
torques to the left and right wheels based on steering input.

--Radu

From: 'Radu Serban' via ProjectChrono <[email protected]>
Sent: Tuesday, May 31, 2022 11:04 AM
To: ProjectChrono <[email protected]>
Subject: RE: [chrono] Skid steer simulation

Hi Shubhankar,

Chrono::Vehicle does not explicitly support skid steer vehicles (well, except 
tracked vehicles), but almost all pieces are available for you to model your 
own.

A related example is in 
demo_VEH_ArticulatedVehicle<https://github.com/projectchrono/chrono/tree/develop/src/demos/vehicle/articulated_vehicle>
 which models a vehicle with an articulated chassis.

But you are probably thinking of something like a Bobcat skid steer loader?  In 
that case, you can use a rigid 
axle<https://api.projectchrono.org/wheeled_suspension.html#wheeled_suspension_ChRigidSuspension>
 on the front and a rigid pinned 
axle<https://api.projectchrono.org/wheeled_suspension.html#wheeled_suspension_ChRigidPinnedAxle>
 on the rear. The only missing piece is then a driveline that mechanically 
links the wheels on the same side.  A simple custom model for such a driveline 
is easy to implement.

I can think of one showstopper: the steering input is not propagated to the 
driveline subsystem. Since at least one other user mentioned skid steer 
vehicles in the past and because this would provide more flexibility, I will 
look into modifying the Chrono::Vehicle data flow to pass all vehicle control 
inputs to various vehicle subsystems.  I will reply to this message when that 
is available.  At that time, you should be able to implement a custom driveline 
for such skid steer vehicles.

--Radu



From: [email protected] <[email protected]> On Behalf Of 
Shubhankar Kulkarni
Sent: Monday, May 30, 2022 9:45 PM
To: ProjectChrono <[email protected]>
Subject: [chrono] Skid steer simulation

Hello,
I wished to know whether there is any pre-existing model in projectChrono that 
has a skid-steer mechanism for a wheeled platform?Is there a way to simulate it?

Thanks & Regards,
Shubhankar Kulkarni
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