virtualflybar.c

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/*
 * 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, see <http://www.gnu.org/licenses/>
 */

#include "openpilot.h"
#include "physical_constants.h"
#include "pid.h"
#include "stabilization.h"
#include "vbarsettings.h"

static float vbar_integral[MAX_AXES];
extern float vbar_decay;

static float bound(float val, float range);

int stabilization_virtual_flybar(float gyro, float command, float *output, float dT, bool reinit, uint32_t axis, struct pid *pid, VbarSettingsData *settings)
{
        float gyro_gain = 1.0f;

        if(reinit)
                vbar_integral[axis] = 0;

        // Track the angle of the virtual flybar which includes a slow decay
        vbar_integral[axis] = vbar_integral[axis] * vbar_decay + gyro * dT;
        vbar_integral[axis] = bound(vbar_integral[axis], settings->VbarMaxAngle);

        // Compute the normal PID controller output
        float pid_out = pid_apply_setpoint(pid, NULL,  0,  gyro);

        // Command signal can indicate how much to disregard the gyro feedback (fast flips)
        if (settings->VbarGyroSuppress > 0.0f) {
                gyro_gain = (1.0f - fabsf(command) * settings->VbarGyroSuppress / 100.0f);
                gyro_gain = (gyro_gain < 0.0f) ? 0.0f : gyro_gain;
        }

        // Command signal is composed of stick input added to the gyro and virtual flybar
        // Note the PID output has a positive sign (consistent with its use in other places)
        // but the integral is negative since it is the angle of the virtual flybar which is
        // the negative of the accumulated error.
        *output = command * settings->VbarSensitivity[axis] + 
            gyro_gain * (pid_out - vbar_integral[axis] * pid->i);

        return 0;
}

int stabilization_virtual_flybar_pirocomp(float z_gyro, float dT)
{
        float cy = cosf(z_gyro * DEG2RAD * dT);
        float sy = sinf(z_gyro * DEG2RAD * dT);

        float vbar_pitch = cy * vbar_integral[1] - sy * vbar_integral[0];
        float vbar_roll = sy * vbar_integral[1] + cy * vbar_integral[0];

        vbar_integral[1] = vbar_pitch;
        vbar_integral[0] = vbar_roll;

        return 0;
}

static float bound(float val, float range)
{
        if(val < -range) {
                val = -range;
        } else if(val > range) {
                val = range;
        }
        return val;
}