[ODE] Vehicle Gears/DriveDrain/Engine techniques.

[Jeff Weber]

I have a general idea how i'm going to implement the gears/drive train, and 
yes there will be an analog gas pedal involved.

From this paper http://home.planet.nl/~monstrous/tutcar.html I got the 
following that I plan to use:

maxEngineTorque = LookUpTorqueCurve(rpm)
engineTorque = throttlePosition*maxEngineTorque

driveTorque = engineTorque * gearRatio * differentialRatio * 
transmissionEfficiency.

I then plan to apply the drive torque by setting the hinge2 joint's MaxForce 
= driveTorque.

What I'm currently debating, is how "realistic" do I try to be.  According 
to Matt Barnett's post, it may not be easy to find all the precise torque 
data I need so right now i'm leaning toward "faking" the torque curves and 
just tuning it till it feels right.  My simulation needs only to feel right 
to the driver, it doesn't necassarily need to be based on precise vehicle 
characteristics.

Any other input is more than welcome.







----Original Message Follows----
From: "David Whittaker" <david@csworkbench.com>
Reply-To: david@csworkbench.com
To: <ode@q12.org>
Subject: Re: [ODE] Vehicle Gears/DriveDrain/Engine techniques.
Date: Tue, 15 Apr 2003 12:40:56 -0500 (CDT)

 > I'm soon to be creating the engine/drivetrain for my vehicles.  Looking
 > for  any techniques others have used.
 >
 > Has anyone had any luck simulating gears using real torque curves?  In
 > other  words, if all the units for my vehicle are correct, and I apply
 > drive torque  derived from real torque curves and gear ratios, will the
 > vehicle behave  realistically.
 >
 > I think in theory it should but was wondering if anyone has done it.
 >
 > Also, how is DesiredVelocity handled in this situation. Is it acceptable
 > to  just make DesiredVelocity some arbitrarily large value and let the
 > max  vehicle speed be limited by different drag/resistance forces?
 >
 > -jeff
 >

I don't have any experience with using this method, but I don't see why it
wouldn't work.  With enough external forces (i.e. drag/wind resistance), a
car should (theoretically) reach a "terminal velocity" that would be it's
max speed, based on the fmax (i.e. your torque) of the joints pushing it
against these external forces.

The desired velocity paramter could be set to some big value, and just let
the fmax and external forces determine the car's velocity.  But then a car
capable of going 200 mph couldn't go 60 without gas-brake-gas-brake kind
of motion.  So you might relate an analog gas pedal directly to desired
velocity.

 >
 >
 >
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