RateControl.hpp

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/**
 * @file RateControl.hpp
 *
 * PID 3 axis angular rate / angular velocity control.
 */

#pragma once

#include <matrix/matrix/math.hpp>
#include <mathlib/math/filter/LowPassFilter2pVector3f.hpp>

#include <lib/mixer/MultirotorMixer/MultirotorMixer.hpp>
#include <uORB/topics/rate_ctrl_status.h>

class RateControl
{
public:
    RateControl() = default;
    ~RateControl() = default;

    /**
     * Set the rate control gains
     * @param P 3D vector of proportional gains for body x,y,z axis
     * @param I 3D vector of integral gains
     * @param D 3D vector of derivative gains
     */
    void setGains(const matrix::Vector3f &P, const matrix::Vector3f &I, const matrix::Vector3f &D);

    /**
     * Set the mximum absolute value of the integrator for all axes
     * @param integrator_limit limit value for all axes x, y, z
     */
    void setIntegratorLimit(const matrix::Vector3f &integrator_limit) { _lim_int = integrator_limit; };

    /**
     * Set update frequency and low-pass filter cutoff that is applied to the derivative term
     * @param loop_rate [Hz] rate with which update function is called
     * @param cutoff [Hz] cutoff frequency for the low-pass filter on the dervative term
     * @param force flag to force an expensive update even if the cutoff didn't change
     */
    void setDTermCutoff(const float loop_rate, const float cutoff, const bool force);

    /**
     * Set direct rate to torque feed forward gain
     * @see _gain_ff
     * @param FF 3D vector of feed forward gains for body x,y,z axis
     */
    void setFeedForwardGain(const matrix::Vector3f &FF) { _gain_ff = FF; };

    /**
     * Set saturation status
     * @param status message from mixer reporting about saturation
     */
    void setSaturationStatus(const MultirotorMixer::saturation_status &status);

    /**
     * Run one control loop cycle calculation
     * @param rate estimation of the current vehicle angular rate
     * @param rate_sp desired vehicle angular rate setpoint
     * @param dt desired vehicle angular rate setpoint
     * @return [-1,1] normalized torque vector to apply to the vehicle
     */
    matrix::Vector3f update(const matrix::Vector3f &rate, const matrix::Vector3f &rate_sp, const float dt,
                const bool landed);

    /**
     * Set the integral term to 0 to prevent windup
     * @see _rate_int
     */
    void resetIntegral() { _rate_int.zero(); }

    /**
     * Get status message of controller for logging/debugging
     * @param rate_ctrl_status status message to fill with internal states
     */
    void getRateControlStatus(rate_ctrl_status_s &rate_ctrl_status);

private:
    void updateIntegral(matrix::Vector3f &rate_error, const float dt);

    // Gains
    matrix::Vector3f _gain_p; ///< rate control proportional gain for all axes x, y, z
    matrix::Vector3f _gain_i; ///< rate control integral gain
    matrix::Vector3f _gain_d; ///< rate control derivative gain
    matrix::Vector3f _lim_int; ///< integrator term maximum absolute value
    matrix::Vector3f _gain_ff; ///< direct rate to torque feed forward gain only useful for helicopters

    // States
    matrix::Vector3f _rate_prev; ///< angular rates of previous update
    matrix::Vector3f _rate_prev_filtered; ///< low-pass filtered angular rates of previous update
    matrix::Vector3f _rate_int; ///< integral term of the rate controller
    math::LowPassFilter2pVector3f _lp_filters_d{0.f, 0.f}; ///< low-pass filters for D-term (roll, pitch & yaw)
    bool _mixer_saturation_positive[3] {};
    bool _mixer_saturation_negative[3] {};
};