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Diffstat (limited to 'apps/fixedwing_control/pid.c')
-rw-r--r-- | apps/fixedwing_control/pid.c | 118 |
1 files changed, 118 insertions, 0 deletions
diff --git a/apps/fixedwing_control/pid.c b/apps/fixedwing_control/pid.c new file mode 100644 index 000000000..81b4deac1 --- /dev/null +++ b/apps/fixedwing_control/pid.c @@ -0,0 +1,118 @@ +/**************************************************************************** + * pid.c + * + * Copyright (C) 2012 Ivan Ovinnikov. All rights reserved. + * Authors: Ivan Ovinnikov <oivan@ethz.ch> + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * 3. Neither the name NuttX nor the names of its contributors may be + * used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS + * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT + * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS + * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE + * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, + * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS + * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED + * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN + * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + * + ****************************************************************************/ + +/**************************************************************************** + * Included Files + ****************************************************************************/ + +#include "pid.h" +#include "fixedwing_control.h" + +/******************************************************************************* + * pid() + * + * Calculates the PID control output given an error + * + * Input: float error, uint16_t dt, float scaler, float K_p, float K_i, float K_d + * + * Output: PID control value + * + ******************************************************************************/ + +static float pid(float error, float error_deriv, uint16_t dt, float scaler, float K_p, float K_i, float K_d, float intmax) +{ + // PID parameters + + float Kp = K_p; + float Ki = K_i; + float Kd = K_d; + float delta_time = dt; // delta time + float lerror; // last error value + float imax = intmax; // max integral value + float integrator; + float derivative; + float lderiv; + int fCut = 20; // anything above 20 Hz is considered noise - low pass filter for the derivative + float output = 0; // the output of the PID controller + + output += error * Kp; + + if ((fabs(Kd) > 0) && (dt > 0)) { + + if (PID_DERIVMODE_CALC) { + derivative = (error - lerror) / delta_time; + + // discrete low pass filter, cuts out the + // high frequency noise that can drive the controller crazy + float RC = 1 / (2 * M_PI * fCut); + derivative = lderiv + + (delta_time / (RC + delta_time)) * (derivative - lderiv); + + // update state + lerror = error; + lderiv = derivative; + + } else { + derivative = error_deriv; + } + + // add in derivative component + output += Kd * derivative; + } + + printf("PID derivative %i\n", (int)(1000 * derivative)); + + // scale the P and D components + output *= scaler; + + // Compute integral component if time has elapsed + if ((fabs(Ki) > 0) && (dt > 0)) { + integrator += (error * Ki) * scaler * delta_time; + + if (integrator < -imax) { + integrator = -imax; + + } else if (integrator > imax) { + integrator = imax; + } + + output += integrator; + } + + printf("PID Integrator %i\n", (int)(1000 * integrator)); + + return output; +} + |