e9f4fc5972
> > Here's a patch to add manual-pitch control to the propeller in YASim. A new > > control axis "PROPPITCH" is added. Requires "manual-pitch" boolean property > > in the "propeller" tag. > > > > Tags and Properties to add in order to enable: > > > > manual-pitch="true" > > > > <control-input axis="/controls/engines/engine[0]/propeller-pitch" > > control="PROPPITCH" src0="0" src1="1" dst0="0.40" dst1="0.80"/> > > > > Note that for the time being, excessively low RPM or excessively high RPM is > > brought undercontrol by a scaling range defined in the control-input tag > > (see "dst0" and "dst1" properties).
116 lines
2.9 KiB
C++
116 lines
2.9 KiB
C++
#include <stdio.h>
|
|
|
|
#include "Atmosphere.hpp"
|
|
#include "Math.hpp"
|
|
#include "Propeller.hpp"
|
|
namespace yasim {
|
|
|
|
Propeller::Propeller(float radius, float v, float omega,
|
|
float rho, float power)
|
|
{
|
|
// Initialize numeric constants:
|
|
_lambdaPeak = Math::pow(5.0, -1.0/4.0);
|
|
_beta = 1.0f/(Math::pow(5.0f, -1.0f/4.0f) - Math::pow(5.0f, -5.0f/4.0f));
|
|
|
|
_r = radius;
|
|
_etaC = 0.85f; // make this settable?
|
|
|
|
_j0 = v/(omega*_lambdaPeak);
|
|
_baseJ0 = _j0;
|
|
|
|
float V2 = v*v + (_r*omega)*(_r*omega);
|
|
_f0 = 2*_etaC*power/(rho*v*V2);
|
|
|
|
_matchTakeoff = false;
|
|
_manual = false;
|
|
_proppitch = 0;
|
|
}
|
|
|
|
void Propeller::setTakeoff(float omega0, float power0)
|
|
{
|
|
// Takeoff thrust coefficient at lambda==0
|
|
_matchTakeoff = true;
|
|
float V2 = _r*omega0 * _r*omega0;
|
|
float gamma = _etaC * _beta / _j0;
|
|
float torque = power0 / omega0;
|
|
float density = Atmosphere::getStdDensity(0);
|
|
_tc0 = (torque * gamma) / (0.5f * density * V2 * _f0);
|
|
}
|
|
|
|
void Propeller::modPitch(float mod)
|
|
{
|
|
_j0 *= mod;
|
|
if(_j0 < 0.25f*_baseJ0) _j0 = 0.25f*_baseJ0;
|
|
if(_j0 > 4*_baseJ0) _j0 = 4*_baseJ0;
|
|
}
|
|
|
|
void Propeller::setManualPitch()
|
|
{
|
|
_manual = true;
|
|
}
|
|
|
|
void Propeller::setPropPitch(float proppitch)
|
|
{
|
|
// makes only positive range of axis effective.
|
|
_proppitch = Math::clamp(proppitch, 0, 1);
|
|
}
|
|
|
|
void Propeller::calc(float density, float v, float omega,
|
|
float* thrustOut, float* torqueOut)
|
|
{
|
|
if (_manual) {
|
|
float pps = _proppitch * 0.9999f; // avoid singularity
|
|
pps = 1 + ( Math::pow(pps,-1/(pps-1)) - Math::pow(pps,-pps/(pps-1)) );
|
|
_j0 = (4*_baseJ0) - ( ((4*_baseJ0) - (0.26f*_baseJ0)) * pps );
|
|
}
|
|
|
|
float tipspd = _r*omega;
|
|
float V2 = v*v + tipspd*tipspd;
|
|
|
|
// Clamp v (forward velocity) to zero, now that we've used it to
|
|
// calculate V (propeller "speed")
|
|
if(v < 0) v = 0;
|
|
|
|
// The model doesn't work for propellers turning backwards.
|
|
if(omega < 0.001) omega = 0.001;
|
|
|
|
float J = v/omega;
|
|
float lambda = J/_j0;
|
|
|
|
float torque = 0;
|
|
if(lambda > 1) {
|
|
lambda = 1.0f/lambda;
|
|
torque = (density*V2*_f0*_j0)/(4*_etaC*_beta*(1-_lambdaPeak));
|
|
}
|
|
|
|
// There's an undefined point at 1. Just offset by a tiny bit to
|
|
// fix (note: the discontinuity is at EXACTLY one, this is about
|
|
// the only time in history you'll see me use == on a floating
|
|
// point number!)
|
|
if(lambda == 1.0) lambda = 0.9999f;
|
|
|
|
// Calculate lambda^4
|
|
float l4 = lambda*lambda; l4 = l4*l4;
|
|
|
|
// thrust/torque ratio
|
|
float gamma = (_etaC*_beta/_j0)*(1-l4);
|
|
|
|
// Compute a thrust, clamp to takeoff thrust to prevend huge
|
|
// numbers at slow speeds.
|
|
float tc = (1 - lambda) / (1 - _lambdaPeak);
|
|
if(_matchTakeoff && tc > _tc0) tc = _tc0;
|
|
|
|
float thrust = 0.5f * density * V2 * _f0 * tc;
|
|
|
|
if(torque > 0) {
|
|
torque -= thrust/gamma;
|
|
thrust = -thrust;
|
|
} else {
|
|
torque = thrust/gamma;
|
|
}
|
|
|
|
*thrustOut = thrust;
|
|
*torqueOut = torque;
|
|
}
|
|
|
|
}; // namespace yasim
|