PIController.h

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/* Copyright (c) 2021 Skyward Experimental Rocketry
 * Author: Vincenzo Santomarco
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 
#pragma once
 
#include <limits>
 
namespace Boardcore
{
 
class PIController
{
public:
    PIController(float Kp, float Ki, float Ts = 1,
                 float uMin = -std::numeric_limits<float>::infinity(),
                 float uMax = std::numeric_limits<float>::infinity())
        : Kp(Kp), Ki(Ki), Ts(Ts), uMin(uMin), uMax(uMax)
    {
    }
 
    float update(float error)
    {
        if (!saturation)
            i = i + Ki * Ts * error;
 
        float u = Kp * error + i;
 
        lastOutput = antiWindUp(u);
        return lastOutput;
    }
 
    float antiWindUp(float u) { return antiWindUp(u, uMin, uMax); }
 
    float antiWindUp(float u, float uMin, float uMax)
    {
        if (u < uMin)
        {
            u          = uMin;
            saturation = true;
        }
        else if (u > uMax)
        {
            u          = uMax;
            saturation = true;
        }
        else
        {
            saturation = false;
        }
 
        return u;
    }
 
    float getI() { return i; }
 
    float getLastOutput() { return lastOutput; }
 
    bool isSaturated() { return saturation; }
 
    float Kp;          // Proportional factor.
    float Ki;          // Integral factor.
    float Ts;          // Sampling period.
    float uMin, uMax;  // Anti-windup limits.
 
private:
    float i = 0;       // Integral contribution.
    float lastOutput;  // Last computed controller output.
    bool saturation = false;
};
 
}  // namespace Boardcore