PxVehicleTireForceParams
Defined in include/vehicle2/tire/PxVehicleTireParams.h
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struct PxVehicleTireForceParams
Public Functions
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inline PxVehicleTireForceParams transformAndScale(const PxVehicleFrame &srcFrame, const PxVehicleFrame &trgFrame, const PxVehicleScale &srcScale, const PxVehicleScale &trgScale) const
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inline bool isValid() const
Public Members
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PxReal latStiffX
Tire lateral stiffness is a graph of tire load that has linear behavior near zero load and flattens at large loads.
latStiffX describes the minimum normalized load (load/restLoad) that gives a flat lateral stiffness response to load.
Note
A value of 0.0 indicates that the tire lateral stiffness is independent of load and will adopt the value latStiffY for all values of tire load.
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PxReal latStiffY
Tire lateral stiffness is a graph of tire load that has linear behavior near zero load and flattens at large loads.
latStiffY describes the maximum possible value of lateral stiffness that occurs when (load/restLoad) >= latStiffX.
Unit: force per lateral slip = mass * length / (time^2)
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PxReal longStiff
Tire Longitudinal stiffness.
Unit: force per longitudinal slip = mass * length / (time^2)
Note
Longitudinal force can be approximated as longStiff*longitudinalSlip.
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PxReal camberStiff
Tire camber stiffness.
Unit: force per radian = mass * length / (time^2)
Note
Camber force can be approximated as camberStiff*camberAngle.
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PxReal frictionVsSlip[3][2]
Graph of friction vs longitudinal slip with 3 points.
Note
frictionVsSlip[0][0] is always zero.
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frictionVsSlip[0][1] is the friction available at zero longitudinal slip.
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frictionVsSlip[1][0] is the value of longitudinal slip with maximum friction.
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frictionVsSlip[1][1] is the maximum friction.
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frictionVsSlip[2][0] is the end point of the graph.
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frictionVsSlip[2][1] is the value of friction for slips greater than frictionVsSlip[2][0].
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The friction value is computed from the friction vs longitudinal slip graph using linear interpolation.
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The friction value computed from the friction vs longitudinal slip graph is used to scale the friction value of the road geometry.
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frictionVsSlip[2][0] > frictionVsSlip[1][0] > frictionVsSlip[0][0]
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frictionVsSlip[1][1] is typically greater than frictionVsSlip[0][1]
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frictionVsSlip[2][1] is typically smaller than frictionVsSlip[1][1]
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longitudinal slips > frictionVsSlip[2][0] use friction multiplier frictionVsSlip[2][1]
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PxReal restLoad
The rest load is the load that develops on the tire when the vehicle is at rest on a flat plane.
Unit: force = mass * length / (time^2)
Note
The rest load is approximately the product of gravitational acceleration and (sprungMass + wheelMass).
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PxReal loadFilter[2][2]
Tire load variation can be strongly dependent on the time-step so it is a good idea to filter it to give less jerky handling behavior.
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Tire load filtering is implemented by linear interpolating a graph containing just two points. The x-axis of the graph is normalized tire load, while the y-axis is the filtered normalized tire load that is to be applied during the tire force calculation.
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The normalized load is the force acting downwards on the tire divided by restLoad.
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The minimum possible normalized load is zero.
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There are two points on the graph: (minNormalisedLoad, minNormalisedFilteredLoad) and (maxNormalisedLoad, maxFilteredNormalisedLoad).
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Normalized loads less than minNormalisedLoad have filtered normalized load = minNormalisedFilteredLoad.
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Normalized loads greater than maxNormalisedLoad have filtered normalized load = maxFilteredNormalisedLoad.
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Normalized loads in-between are linearly interpolated between minNormalisedFilteredLoad and maxFilteredNormalisedLoad.
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The tire load applied as input to the tire force computation is the filtered normalized load multiplied by the rest load.
Note
loadFilter[0][0] is minNormalisedLoad
Note
loadFilter[0][1] is minFilteredNormalisedLoad
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loadFilter[1][0] is maxNormalisedLoad
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loadFilter[1][1] is maxFilteredNormalisedLoad
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inline PxVehicleTireForceParams transformAndScale(const PxVehicleFrame &srcFrame, const PxVehicleFrame &trgFrame, const PxVehicleScale &srcScale, const PxVehicleScale &trgScale) const