pd.h

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 * @details
 * This file defines the @ref control_system::pd::PD class, which
 * implements a discrete-time proportional-derivative (PD) controller.
 *
 * The controller combines proportional and derivative actions to
 * generate a control output based on the error between a reference
 * value and the measured or current value.
 *
 * The controller maintains the previous control error as internal
 * state and applies a configurable maximum output limit.
 *
 * @tparam T Numeric data type used for the controller calculations.
 *
 * @author Abhinay Kumar
 * @version 1.0.0
 * @date 2026-08-11
 *
 * @copyright
 * Copyright (c) 2026 Abhinay Kumar
 */
 
#ifndef CONTROL_SYSTEM_PD_PD_H
#define CONTROL_SYSTEM_PD_PD_H
 
#include "../utility/utility.h"
 
namespace control_system
{
 
    namespace pd
    {

         * The PD class implements a discrete-time proportional-derivative
         * controller using configurable proportional and derivative gains.
         *
         * The controller uses the sampling time for its discrete-time
         * derivative action and maintains the previous control error as
         * internal state.
         *
         * @tparam T Numeric data type used for the controller.
         *
         * @par Example
         * @code{.cpp}
         * control_system::pd::PD<double> controller;
         *
         * controller.init(
         *     0.001,
         *     Kp,
         *     Kd,
         *     100.0
         * );
         *
         * double output = controller.update(reference, measurement);
         * @endcode
         */
        template <typename T>
        class PD
        {
        public:

             * @details
             * Constructs the controller with its parameters and internal
             * state initialized to their default values.
             */
            PD();

            /**
             * @brief Initializes the PD controller.
             *
             * @param[in] dt_ Controller sampling time in seconds.
             * @param[in] Kp_ Proportional gain.
             * @param[in] Kd_ Derivative gain.
             * @param[in] u_max_ Maximum allowed controller output.
             *
             * @details
             * Initializes the controller sampling time, proportional and
             * derivative gains, and output limit.
             */
            void init(T dt_, T Kp_, T Kd_, T u_max_);


             * @param[in] Kp_ Proportional gain.
             * @param[in] Kd_ Derivative gain.
             * @param[in] u_max_ Maximum allowed controller output.
             *
             * @details
             * Updates the controller sampling time, proportional and
             * derivative gains, and maximum output limit.
             */
            void set_param(T dt_, T Kp_, T Kd_, T u_max_);


            T update(T x_0, T x);

            void reset();

            void merge(T u_k_1_);

            void set_dt(T dt_);

            void set_Kp(T Kp_);

            void set_Kd(T Kd_);

            void set_u_max(T u_max_);

            T get_dt();

            T get_Kp();

            T get_Kd();

            T get_e_k_1();

            T get_u_max();
 
        private:
            T dt = 0.0;

            T e_k_1 = 0.0;

            T Kp = 0.0;

            T Kd = 0.0;

            bool start = true;

            T u_max = 9999999999;
        };
 
#include "../../src/pd/pd.tpp"
    }
}
 
#endif