pid/pidcontroller.cpp

/**
 * Copyright 2017 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "pidcontroller.hpp"

#include "ec/pid.hpp"

#include <cmath>

namespace pid_control
{

double PIDController::calPIDOutput(double setpt, double input,
                                   ec::pid_info_t* info)
{
    double output;
    auto name = getID();

    if (info->checkHysterWithSetpt)
    {
        // Over the hysteresis bounds, keep counting pid
        if (input > (setpt + info->positiveHysteresis))
        {
            // Calculate new output
            output = ec::pid(info, input, setpt, &name);

            // this variable isn't actually used in this context, but we're
            // setting it here in case somebody uses it later it's the correct
            // value
            lastInput = input;
        }
        // Under the hysteresis bounds, initialize pid
        else if (input < (setpt - info->negativeHysteresis))
        {
            lastInput = setpt;
            info->integral = 0;
            output = 0;
        }
        // inside the hysteresis bounds, keep last output
        else
        {
            lastInput = input;
            output = info->lastOutput;
        }

        info->lastOutput = output;
    }
    else
    {
        // if no hysteresis, maintain previous behavior
        if (info->positiveHysteresis == 0 && info->negativeHysteresis == 0)
        {
            // Calculate new output
            output = ec::pid(info, input, setpt, &name);

            // this variable isn't actually used in this context, but we're
            // setting it here in case somebody uses it later it's the correct
            // value
            lastInput = input;
        }
        else
        {
            // initialize if the value is not set (NAN) or abnormal (+INF or
            // -INF)
            if (!(std::isfinite(lastInput)))
            {
                lastInput = input;
            }

            // if reading is outside of hysteresis bounds, use it for reading,
            // otherwise use last reading without updating it first
            else if ((input - lastInput) > info->positiveHysteresis)
            {
                lastInput = input;
            }
            else if ((lastInput - input) > info->negativeHysteresis)
            {
                lastInput = input;
            }

            output = ec::pid(info, lastInput, setpt, &name);
        }
    }

    return output;
}

void PIDController::process(void)
{
    double input;
    double setpt;
    double output;

    // Get setpt value
    setpt = setptProc();

    // Get input value
    input = inputProc();

    auto info = getPIDInfo();

    // Calculate output value
    output = calPIDOutput(setpt, input, info);

    info->lastOutput = output;

    // Output new value
    outputProc(output);

    return;
}

} // namespace pid_control