controller.cpp

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/*
 * Copyright (c) 2017, James Jackson and Daniel Koch, BYU MAGICC Lab
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * * Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.
 *
 * * 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.
 *
 * * Neither the name of the copyright holder 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
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 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <stdint.h>
#include <stdbool.h>

#include "command_manager.h"
#include "estimator.h"
#include "rosflight.h"

#include "controller.h"

namespace rosflight_firmware
{

Controller::Controller(ROSflight &rf) :
  RF_(rf)
{
  RF_.params_.add_callback([this](uint16_t param_id)
  {
    this->param_change_callback(param_id);
  }, PARAM_PID_ROLL_ANGLE_P);
  RF_.params_.add_callback([this](uint16_t param_id)
  {
    this->param_change_callback(param_id);
  }, PARAM_PID_ROLL_ANGLE_I);
  RF_.params_.add_callback([this](uint16_t param_id)
  {
    this->param_change_callback(param_id);
  }, PARAM_PID_ROLL_ANGLE_D);
  RF_.params_.add_callback([this](uint16_t param_id)
  {
    this->param_change_callback(param_id);
  }, PARAM_PID_ROLL_RATE_P);
  RF_.params_.add_callback([this](uint16_t param_id)
  {
    this->param_change_callback(param_id);
  }, PARAM_PID_ROLL_RATE_I);
  RF_.params_.add_callback([this](uint16_t param_id)
  {
    this->param_change_callback(param_id);
  }, PARAM_PID_ROLL_RATE_D);
  RF_.params_.add_callback([this](uint16_t param_id)
  {
    this->param_change_callback(param_id);
  }, PARAM_PID_PITCH_ANGLE_P);
  RF_.params_.add_callback([this](uint16_t param_id)
  {
    this->param_change_callback(param_id);
  }, PARAM_PID_PITCH_ANGLE_I);
  RF_.params_.add_callback([this](uint16_t param_id)
  {
    this->param_change_callback(param_id);
  }, PARAM_PID_PITCH_ANGLE_D);
  RF_.params_.add_callback([this](uint16_t param_id)
  {
    this->param_change_callback(param_id);
  }, PARAM_PID_PITCH_RATE_P);
  RF_.params_.add_callback([this](uint16_t param_id)
  {
    this->param_change_callback(param_id);
  }, PARAM_PID_PITCH_RATE_I);
  RF_.params_.add_callback([this](uint16_t param_id)
  {
    this->param_change_callback(param_id);
  }, PARAM_PID_PITCH_RATE_D);
  RF_.params_.add_callback([this](uint16_t param_id)
  {
    this->param_change_callback(param_id);
  }, PARAM_PID_YAW_RATE_P);
  RF_.params_.add_callback([this](uint16_t param_id)
  {
    this->param_change_callback(param_id);
  }, PARAM_PID_YAW_RATE_I);
  RF_.params_.add_callback([this](uint16_t param_id)
  {
    this->param_change_callback(param_id);
  }, PARAM_PID_YAW_RATE_D);
  RF_.params_.add_callback([this](uint16_t param_id)
  {
    this->param_change_callback(param_id);
  }, PARAM_MAX_COMMAND);
  RF_.params_.add_callback([this](uint16_t param_id)
  {
    this->param_change_callback(param_id);
  }, PARAM_PID_TAU);
}

void Controller::init()
{
  prev_time_us_ = 0;

  float max = RF_.params_.get_param_float(PARAM_MAX_COMMAND);
  float min = -max;
  float tau = RF_.params_.get_param_float(PARAM_PID_TAU);

  roll_.init(RF_.params_.get_param_float(PARAM_PID_ROLL_ANGLE_P),
             RF_.params_.get_param_float(PARAM_PID_ROLL_ANGLE_I),
             RF_.params_.get_param_float(PARAM_PID_ROLL_ANGLE_D),
             max, min, tau);
  roll_rate_.init(RF_.params_.get_param_float(PARAM_PID_ROLL_RATE_P),
                  RF_.params_.get_param_float(PARAM_PID_ROLL_RATE_I),
                  RF_.params_.get_param_float(PARAM_PID_ROLL_RATE_D),
                  max, min, tau);
  pitch_.init(RF_.params_.get_param_float(PARAM_PID_PITCH_ANGLE_P),
              RF_.params_.get_param_float(PARAM_PID_PITCH_ANGLE_I),
              RF_.params_.get_param_float(PARAM_PID_PITCH_ANGLE_D),
              max, min, tau);
  pitch_rate_.init(RF_.params_.get_param_float(PARAM_PID_PITCH_RATE_P),
                   RF_.params_.get_param_float(PARAM_PID_PITCH_RATE_I),
                   RF_.params_.get_param_float(PARAM_PID_PITCH_RATE_D),
                   max, min, tau);
  yaw_rate_.init(RF_.params_.get_param_float(PARAM_PID_YAW_RATE_P),
                 RF_.params_.get_param_float(PARAM_PID_YAW_RATE_I),
                 RF_.params_.get_param_float(PARAM_PID_YAW_RATE_D),
                 max, min, tau);
}

void Controller::run()
{
  // Time calculation
  if (prev_time_us_ == 0)
  {
    prev_time_us_ = RF_.estimator_.state().timestamp_us;
    return;
  }

  int32_t dt_us = (RF_.estimator_.state().timestamp_us - prev_time_us_);
  if (dt_us < 0)
  {
    RF_.state_manager_.set_error(StateManager::ERROR_TIME_GOING_BACKWARDS);
    return;
  }
  prev_time_us_ = RF_.estimator_.state().timestamp_us;

  // Check if integrators should be updated
  bool update_integrators = (RF_.state_manager_.state().armed)
                            && (RF_.command_manager_.combined_control().F.value > 0.1f) && dt_us < 10000;

  // Run the PID loops
  turbomath::Vector pid_output = run_pid_loops(dt_us, RF_.estimator_.state(), RF_.command_manager_.combined_control(),
                                 update_integrators);

  // Add feedforward torques
  output_.x = pid_output.x + RF_.params_.get_param_float(PARAM_X_EQ_TORQUE);
  output_.y = pid_output.y + RF_.params_.get_param_float(PARAM_Y_EQ_TORQUE);
  output_.z = pid_output.z + RF_.params_.get_param_float(PARAM_Z_EQ_TORQUE);
  output_.F = RF_.command_manager_.combined_control().F.value;
}

void Controller::calculate_equilbrium_torque_from_rc()
{
  // Make sure we are disarmed
  if (!(RF_.state_manager_.state().armed))
  {
    // Tell the user that we are doing a equilibrium torque calibration
    RF_.comm_manager_.log(CommLink::LogSeverity::LOG_WARNING, "Capturing equilbrium offsets from RC");

    // Prepare for calibration
    // artificially tell the flight controller it is leveled
    Estimator::State fake_state;
    fake_state.angular_velocity.x = 0.0f;
    fake_state.angular_velocity.y = 0.0f;
    fake_state.angular_velocity.z = 0.0f;

    fake_state.attitude.x = 0.0f;
    fake_state.attitude.y = 0.0f;
    fake_state.attitude.z = 0.0f;
    fake_state.attitude.w = 1.0f;

    fake_state.roll = 0.0f;
    fake_state.pitch = 0.0f;
    fake_state.yaw = 0.0f;

    // pass the rc_control through the controller
    // dt is zero, so what this really does is applies the P gain with the settings
    // your RC transmitter, which if it flies level is a really good guess for
    // the static offset torques
    turbomath::Vector pid_output = run_pid_loops(0, fake_state, RF_.command_manager_.rc_control(), false);

    // the output from the controller is going to be the static offsets
    RF_.params_.set_param_float(PARAM_X_EQ_TORQUE, pid_output.x + RF_.params_.get_param_float(PARAM_X_EQ_TORQUE));
    RF_.params_.set_param_float(PARAM_Y_EQ_TORQUE, pid_output.y + RF_.params_.get_param_float(PARAM_Y_EQ_TORQUE));
    RF_.params_.set_param_float(PARAM_Z_EQ_TORQUE, pid_output.z + RF_.params_.get_param_float(PARAM_Z_EQ_TORQUE));

    RF_.comm_manager_.log(CommLink::LogSeverity::LOG_WARNING, "Equilibrium torques found and applied.");
    RF_.comm_manager_.log(CommLink::LogSeverity::LOG_WARNING, "Please zero out trims on your transmitter");
  }
  else
  {
    RF_.comm_manager_.log(CommLink::LogSeverity::LOG_WARNING, "Cannot perform equilibrium offset calibration while armed");
  }
}

void Controller::param_change_callback(uint16_t param_id)
{
  (void) param_id; // suppress unused parameter warning
  init();
}

turbomath::Vector Controller::run_pid_loops(uint32_t dt_us, const Estimator::State &state, const control_t &command,
    bool update_integrators)
{
  // Based on the control types coming from the command manager, run the appropriate PID loops
  turbomath::Vector out;

  float dt = 1e-6*dt_us;

  // ROLL
  if (command.x.type == RATE)
    out.x = roll_rate_.run(dt, state.angular_velocity.x, command.x.value, update_integrators);
  else if (command.x.type == ANGLE)
    out.x = roll_.run(dt, state.roll, command.x.value, update_integrators, state.angular_velocity.x);
  else
    out.x = command.x.value;

  // PITCH
  if (command.y.type == RATE)
    out.y = pitch_rate_.run(dt, state.angular_velocity.y, command.y.value, update_integrators);
  else if (command.y.type == ANGLE)
    out.y = pitch_.run(dt, state.pitch, command.y.value, update_integrators, state.angular_velocity.y);
  else
    out.y = command.y.value;

  // YAW
  if (command.z.type == RATE)
    out.z = yaw_rate_.run(dt, state.angular_velocity.z, command.z.value, update_integrators);
  else
    out.z = command.z.value;

  return out;
}

Controller::PID::PID() :
  kp_(0.0f),
  ki_(0.0f),
  kd_(0.0f),
  max_(1.0f),
  min_(-1.0f),
  integrator_(0.0f),
  differentiator_(0.0f),
  prev_x_(0.0f),
  tau_(0.05)
{}

void Controller::PID::init(float kp, float ki, float kd, float max, float min, float tau)
{
  kp_ = kp;
  ki_ = ki;
  kd_ = kd;
  max_ = max;
  min_ = min;
  tau_ = tau;
}

float Controller::PID::run(float dt, float x, float x_c, bool update_integrator)
{
  float xdot;
  if (dt > 0.0001f)
  {
    // calculate D term (use dirty derivative if we don't have access to a measurement of the derivative)
    // The dirty derivative is a sort of low-pass filtered version of the derivative.
    differentiator_ = (2.0f * tau_ - dt) / (2.0f * tau_ + dt) * differentiator_
                      + 2.0f / (2.0f * tau_ + dt) * (x - prev_x_);
    xdot = differentiator_;
  }
  else
  {
    xdot = 0.0f;
  }
  prev_x_ = x;

  return run(dt, x, x_c, update_integrator, xdot);
}

float Controller::PID::run(float dt, float x, float x_c, bool update_integrator, float xdot)
{
  // Calculate Error
  float error = x_c - x;

  // Initialize Terms
  float p_term = error * kp_;
  float i_term = 0.0f;
  float d_term = 0.0f;

  // If there is a derivative term
  if (kd_ > 0.0f)
  {
    d_term = kd_ * xdot;
  }

  //If there is an integrator term and we are updating integrators
  if ((ki_ > 0.0f) && update_integrator)
  {
    // integrate
    integrator_ += error * dt;
    // calculate I term
    i_term = ki_ * integrator_;
  }

  // sum three terms
  float u = p_term - d_term + i_term;

  // Integrator anti-windup
  float u_sat = (u > max_) ? max_ : (u < min_) ? min_ : u;
  if (u != u_sat && fabs(i_term) > fabs(u - p_term + d_term) && ki_ > 0.0f)
    integrator_ = (u_sat - p_term + d_term)/ki_;

  // Set output
  return u_sat;
}

} // namespace rosflight_firmware