private void FixedUpdate()
{
// brakeTorque
brakeTorque = wheel.brakeTorque;
// center
center = wheel.center;
// forceAppPointDistance // not implemented
// forwardFriction
forwardFriction = wheel.forwardFriction;
// isGrounded
isGrounded = wheel.isGrounded;
// mass
mass = wheel.mass;
// motorTorque
motorTorque = wheel.motorTorque;
// radius
radius = wheel.radius;
// rpm
rpm = wheel.rpm;
// sidewaysFriction
sidewaysFriction = wheel.sideFriction;
// sprungMass // not implemented, use wheel.suspensionForce instead.
// steerAngle
steerAngle = wheel.steerAngle;
// suspensionDistance
suspensionDistance = wheel.suspensionDistance;
// suspensionSpring // not implemented, use wheel.spring instead
// wheelDampingRate // use damper.reboundForce and damper.bumpForce
// GetGroundHit()
wheel.GetGroundHit(out WheelHit hit);
// GetWorldPose()
wheel.GetWorldPose(out position, out rotation);
}
public static void CalculateLateralSlip(float dt, float velocityMagnitude, float angularVelocity,
float loadCoefficient,
float forwardSpeed, ref FrictionPreset frictionPreset, ref Friction friction, bool hasHit,
out float surfaceForce)
{
surfaceForce = 0;
float sideSpeed = friction.speed;
float absForwardSpeed = forwardSpeed < 0 ? -forwardSpeed : forwardSpeed;
float absAngVel = angularVelocity < 0 ? -angularVelocity : angularVelocity;
if (hasHit)
{
if (velocityMagnitude < 0.35f && absAngVel < 1f)
{
friction.PI_error = friction.speed;
friction.PI_integral += friction.PI_error;
friction.slip = friction.Kp * friction.PI_error
+ friction.Ki * friction.PI_integral;
friction.slip = friction.slip <-1f ? -1f : friction.slip> 1f ? 1f : friction.slip;
}
else
{
if (velocityMagnitude < 0.8f && absAngVel < 6f)
{
friction.slip = sideSpeed * 0.25f;
}
else
{
friction.slip = Mathf.Atan2(sideSpeed, absForwardSpeed) * Mathf.Rad2Deg / 80.0f;
}
friction.PI_error = 0;
friction.PI_integral = 0;
}
friction.slip *= friction.slipCoefficient;
friction.slip = friction.slip <-1f ? -1f : friction.slip> 1f ? 1f : friction.slip;
float absSlip = friction.slip < 0 ? -friction.slip : friction.slip;
float slipSign = friction.slip < 0 ? -1f : 1f;
float curveVal = frictionPreset.Curve.Evaluate(absSlip);
surfaceForce = slipSign * curveVal * loadCoefficient * friction.forceCoefficient;
}
}
public static float CalculateLongitudinalSlip(float torque, float brakeTorque, float dragTorque, float wheelRadius,
float wheelInertia,
float dt, float fixedDeltaTime, float loadCoefficient, float BCDEz, ref Friction friction,
ref float angularVelocity, ref float outSurfaceTorque)
{
float speed = friction.speed;
float absSpeed = friction.speed < 0 ? -friction.speed : friction.speed;
float initialAngVel = angularVelocity;
angularVelocity += torque / wheelInertia * dt;
brakeTorque += dragTorque;
brakeTorque = brakeTorque * (angularVelocity > 0 ? -1f : 1f);
float brakeTorqueCap = (angularVelocity < 0 ? -angularVelocity : angularVelocity) * wheelInertia / dt;
brakeTorque = brakeTorque > brakeTorqueCap ? brakeTorqueCap :
brakeTorque < -brakeTorqueCap ? -brakeTorqueCap : brakeTorque;
angularVelocity += brakeTorque / wheelInertia * dt;
float freeAngularVelocity = speed / wheelRadius;
float errorAngularVelocity = angularVelocity - freeAngularVelocity;
float errorTorque = errorAngularVelocity * wheelInertia / dt;
float maxTorque = loadCoefficient * BCDEz * friction.forceCoefficient * 0.8f;
float groundTorque = errorTorque <-maxTorque? - maxTorque :
errorTorque> maxTorque ? maxTorque : errorTorque;
float thresholdVelocity = 0.8f;
if (absSpeed > thresholdVelocity)
{
friction.slip = (speed - angularVelocity * wheelRadius) / absSpeed;
}
else
{
float Vsx = speed - angularVelocity * wheelRadius;
friction.slip = 2f * Vsx / (thresholdVelocity + speed * speed / thresholdVelocity);
}
friction.slip *= friction.slipCoefficient;
friction.slip = friction.slip <-1f ? -1f : friction.slip> 1f ? 1f : friction.slip;
angularVelocity -= groundTorque / wheelInertia * dt;
float deltaOmegaTorque = (angularVelocity - initialAngVel) * wheelInertia / dt;
outSurfaceTorque += groundTorque * (dt / fixedDeltaTime);
float counterTorque = -groundTorque + brakeTorque - deltaOmegaTorque;
#if NVP_DEBUG_PT
if (Powertrain.DEBUG)
{
Debug.Log($"{name} (SendTorque)\tTreceived = {torque}\tTbrake =\tTreact = {Tground}\tslip = {_slip}\t" +
$"W = {angularVelocity}\tIsum = {inertiaSum}\t Returning T = {Treturn}");
}
#endif
return(counterTorque * 0.9f);
}