/**
******************************************************************************
* @addtogroup OpenPilotModules OpenPilot Modules
* @{
* @addtogroup StabilizationModule Stabilization Module
* @brief cruisecontrol mode
* @note This file implements the logic for a cruisecontrol
* @{
*
* @file cruisecontrol.h
* @author The OpenPilot Team, http://www.openpilot.org Copyright (C) 2014.
* @brief Attitude stabilization module.
*
* @see The GNU Public License (GPL) Version 3
*
*****************************************************************************/
/*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <openpilot.h>
#include <stabilization.h>
#include <attitudestate.h>
#include <sin_lookup.h>
static float cruisecontrol_factor = 1.0f;
static inline float CruiseControlLimitThrust(float thrust)
{
// limit to user specified absolute max thrust
return boundf(thrust, stabSettings.cruiseControl.min_thrust, stabSettings.cruiseControl.max_thrust);
}
// assumes 1.0 <= factor <= 100.0
// a factor of less than 1.0 could make it return a value less than stabSettings.cruiseControl.min_thrust
// CP helis need to have min_thrust=-1
//
// multicopters need to have min_thrust=0.05 or so
// values below that will not be subject to max / min limiting
// that means thrust can be less than min
// that means multicopter motors stop spinning at low stick
static inline float CruiseControlFactorToThrust(float factor, float thrust)
{
// don't touch thrust if it's less than min_thrust
// without that test, quadcopter props will spin up
// to min thrust even at zero throttle stick
// if Cruise Control is enabled on this flight switch position
if (thrust > stabSettings.cruiseControl.min_thrust) {
return CruiseControlLimitThrust(thrust * factor);
}
return thrust;
}
static float CruiseControlAngleToFactor(float angle)
{
float factor;
// avoid singularity
if (angle > 89.999f && angle < 90.001f) {
factor = stabSettings.settings.CruiseControlMaxPowerFactor;
} else {
// the simple bank angle boost calculation that Cruise Control revolves around
factor = 1.0f / fabsf(cos_lookup_deg(angle));
// factor in the power trim, no effect at 1.0, linear effect increases with factor
factor = (factor - 1.0f) * stabSettings.cruiseControl.power_trim + 1.0f;
// limit to user specified max power multiplier
if (factor > stabSettings.settings.CruiseControlMaxPowerFactor) {
factor = stabSettings.settings.CruiseControlMaxPowerFactor;
}
}
return factor;
}
void cruisecontrol_compute_factor(AttitudeStateData *attitude, float thrustDemand)
{
static float previous_angle;
static uint32_t previous_time = 0;
static bool previous_time_valid = false;
// For multiple, speedy flips this mainly strives to address the
// fact that (due to thrust delay) thrust didn't average straight
// down, but at an angle. For less speedy flips it acts like it
// used to. It can be turned off by setting power delay to 0.
// It takes significant time for the motors of a multi-copter to
// spin up. It takes significant time for the collective servo of
// a CP heli to move from one end to the other. Both of those are
// modeled here as linear, i.e. twice as much change takes twice
// as long. Given a correctly configured maximum delay time this
// code calculates how far in advance to start the control
// transition so that half way through the physical transition it
// is just crossing the transition angle.
// Example: Rotation rate = 360. Full stroke delay = 0.2
// Transition angle 90 degrees. Start the transition 0.1 second
// before 90 degrees (36 degrees at 360 deg/sec) and it will be
// complete 0.1 seconds after 90 degrees.
// Note that this code only handles the transition to/from inverted
// thrust. It doesn't handle the case where thrust is changed a
// lot in a small angle range when that range is close to 90 degrees.
// It doesn't handle the small constant "system delay" caused by the
// delay between reading sensors and actuators beginning to respond.
// It also assumes that the pilot is holding the throttle constant;
// when the pilot does change the throttle, the compensation is
// simply recalculated.
// This implementation of future thrust isn't perfect. That would
// probably require an iterative procedure for solving a
// transcendental equation of the form linear(x) = 1/cos(x). It's
// shortcomings generally don't hurt anything and work better than
// without it. It is designed to work perfectly if the pilot is
// using full thrust during flips and it is only activated if 70% or
// greater thrust is used.
uint32_t time = PIOS_DELAY_GetuS();
// Get roll and pitch angles, calculate combined angle, and begin
// the general algorithm.
// Example: 45 degrees roll plus 45 degrees pitch = 60 degrees
// Do it every 8th iteration to save CPU.
if (time != previous_time || previous_time_valid == false) {
float angle, angle_unmodified;
// spherical right triangle
// 0.0 <= angle <= 180.0
angle_unmodified = angle = RAD2DEG(acosf(cos_lookup_deg(attitude->Roll)
* cos_lookup_deg(attitude->Pitch)));
// Calculate rate as a combined (roll and pitch) bank angle
// change; in degrees per second. Rate is calculated over the
// most recent 8 loops through stabilization. We could have
// asked the gyros. This is probably cheaper.
if (previous_time_valid) {
float rate;
// rate can be negative.
rate = (angle - previous_angle) / ((float)(time - previous_time) / 1000000.0f);
// Define "within range" to be those transitions that should
// be executing now. Recall that each impulse transition is
// spread out over a range of time / angle.
// There is only one transition and the high power level for
// it is either:
// 1/fabsf(cos(angle)) * current thrust
// or max power factor * current thrust
// or full thrust
// You can cross the transition with angle either increasing
// or decreasing (rate positive or negative).
// Thrust is never boosted for negative values of
// thrustDemand (negative stick values)
//
// When the aircraft is upright, thrust is always boosted
// . for positive values of thrustDemand
// When the aircraft is inverted, thrust is sometimes
// . boosted or reversed (or combinations thereof) or zeroed
// . for positive values of thrustDemand
// It depends on the inverted power settings.
// Of course, you can set MaxPowerFactor to 1.0 to
// . effectively disable boost.
if (thrustDemand > 0.0f) {
// to enable the future thrust calculations, make sure
// there is a large enough transition that the result
// will be roughly on vs. off; without that, it can
// exaggerate the length of time the inverted to upright
// transition holds full throttle and reduce the length
// of time for full throttle when going upright to inverted.
if (thrustDemand > 0.7f) {
float thrust;
thrust = CruiseControlFactorToThrust(CruiseControlAngleToFactor((float)stabSettings.settings.CruiseControlMaxAngle), thrustDemand);
// determine if we are in range of the transition
// given the thrust at max_angle and thrustDemand
// (typically close to 1.0), change variable 'thrust' to
// be the proportion of the largest thrust change possible
// that occurs when going into inverted mode.
// Example: 'thrust' is 0.8 A quad has min_thrust set
// to 0.05 The difference is 0.75. The largest possible
// difference with this setup is 0.9 - 0.05 = 0.85, so
// the proportion is 0.75/0.85
// That is nearly a full throttle stroke.
// the 'thrust' variable is non-negative here
switch (stabSettings.settings.CruiseControlInvertedPowerOutput) {
case STABILIZATIONSETTINGS_CRUISECONTROLINVERTEDPOWEROUTPUT_ZERO:
// normal multi-copter case, stroke is max to zero
// technically max to constant min_thrust
// can be used by CP
thrust = (thrust - CruiseControlLimitThrust(0.0f)) / stabSettings.cruiseControl.thrust_difference;
break;
case STABILIZATIONSETTINGS_CRUISECONTROLINVERTEDPOWEROUTPUT_NORMAL:
// reversed but not boosted
// : CP heli case, stroke is max to -stick
// : thrust = (thrust - CruiseControlLimitThrust(-thrustDemand)) / stabSettings.cruiseControl.thrust_difference;
// else it is both unreversed and unboosted
// : simply turn off boost, stroke is max to +stick
// : thrust = (thrust - CruiseControlLimitThrust(thrustDemand)) / stabSettings.cruiseControl.thrust_difference;
thrust = (thrust - CruiseControlLimitThrust(
(stabSettings.settings.CruiseControlInvertedThrustReversing
== STABILIZATIONSETTINGS_CRUISECONTROLINVERTEDTHRUSTREVERSING_REVERSED)
? -thrustDemand
: thrustDemand)) / stabSettings.cruiseControl.thrust_difference;
break;
case STABILIZATIONSETTINGS_CRUISECONTROLINVERTEDPOWEROUTPUT_BOOSTED:
// if boosted and reversed
if (stabSettings.settings.CruiseControlInvertedThrustReversing
== STABILIZATIONSETTINGS_CRUISECONTROLINVERTEDTHRUSTREVERSING_REVERSED) {
// CP heli case, stroke is max to min
thrust = (thrust - CruiseControlFactorToThrust(-CruiseControlAngleToFactor((float)stabSettings.settings.CruiseControlMaxAngle), thrustDemand)) / stabSettings.cruiseControl.thrust_difference;
}
// else it is boosted and unreversed so the throttle doesn't change
else {
// CP heli case, no transition, so stroke is zero
thrust = 0.0f;
}
break;
}
// 'thrust' is now the proportion of max stroke
// multiply this proportion of max stroke,
// times the max stroke time, to get this stroke time
// we only want half of this time before the transition
// (and half after the transition)
thrust *= stabSettings.cruiseControl.half_power_delay;
// 'thrust' is now the length of time for this stroke
// multiply that times angular rate to get the lead angle
thrust *= fabsf(rate);
// if the transition is within range we use it,
// else we just use the current calculated thrust
if ((float)stabSettings.settings.CruiseControlMaxAngle - thrust <= angle
&& angle <= (float)stabSettings.settings.CruiseControlMaxAngle + thrust) {
// default to a little above max angle
angle = (float)stabSettings.settings.CruiseControlMaxAngle + 0.01f;
// if roll direction is downward
// then thrust value is taken from below max angle
// by the code that knows about the transition angle
if (rate < 0.0f) {
angle -= 0.02f;
}
}
} // if thrust > 0.7; else just use the angle we already calculated
cruisecontrol_factor = CruiseControlAngleToFactor(angle);
} else { // if thrust > 0 set factor from angle; else
cruisecontrol_factor = 1.0f;
}
if (angle >= (float)stabSettings.settings.CruiseControlMaxAngle) {
switch (stabSettings.settings.CruiseControlInvertedPowerOutput) {
case STABILIZATIONSETTINGS_CRUISECONTROLINVERTEDPOWEROUTPUT_ZERO:
cruisecontrol_factor = 0.0f;
break;
case STABILIZATIONSETTINGS_CRUISECONTROLINVERTEDPOWEROUTPUT_NORMAL:
cruisecontrol_factor = 1.0f;
break;
case STABILIZATIONSETTINGS_CRUISECONTROLINVERTEDPOWEROUTPUT_BOOSTED:
// no change, leave factor >= 1.0 alone
break;
}
if (stabSettings.settings.CruiseControlInvertedThrustReversing
== STABILIZATIONSETTINGS_CRUISECONTROLINVERTEDTHRUSTREVERSING_REVERSED) {
cruisecontrol_factor = -cruisecontrol_factor;
}
}
} // if previous_time_valid i.e. we've got a rate; else leave (angle and) factor alone
previous_time = time;
previous_time_valid = true;
previous_angle = angle_unmodified;
} // every 8th time
}
float cruisecontrol_apply_factor(float raw)
{
if (stabSettings.settings.CruiseControlMaxPowerFactor > 0.0001f) {
raw = CruiseControlFactorToThrust(cruisecontrol_factor, raw);
}
return raw;
}