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lib/PID/pid.h

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+/**
+ * @author Aaron Berk
+ *
+ * @section LICENSE
+ *
+ * Copyright (c) 2010 ARM Limited
+ *
+ * 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.
+ *
+ * @section DESCRIPTION
+ * 
+ * A PID controller is a widely used feedback controller commonly found in
+ * industry.
+ *
+ * This library is a port of Brett Beauregard's Arduino PID library:
+ *
+ *  http://www.arduino.cc/playground/Code/PIDLibrary
+ *
+ * The wikipedia article on PID controllers is a good place to start on
+ * understanding how they work:
+ *
+ *  http://en.wikipedia.org/wiki/PID_controller
+ *
+ * For a clear and elegant explanation of how to implement and tune a
+ * controller, the controlguru website by Douglas J. Cooper (who also happened
+ * to be Brett's controls professor) is an excellent reference:
+ *
+ *  http://www.controlguru.com/
+ */
+
+#ifndef PID_H
+#define PID_H
+
+/**
+ * Includes
+ */
+#include <mbed.h>
+
+/**
+ * Defines
+ */
+#define MANUAL_MODE 0
+#define AUTO_MODE   1
+
+/**
+ * Proportional-integral-derivative controller.
+ */
+class PID {
+
+public:
+
+    /**
+     * Constructor.
+     *
+     * Sets default limits [0-3.3V], calculates tuning parameters, and sets
+     * manual mode with no bias.
+     *
+     * @param Kc - Tuning parameter
+     * @param tauI - Tuning parameter
+     * @param tauD - Tuning parameter
+     * @param interval PID calculation performed every interval seconds.
+     */
+    PID(float Kc, float tauI, float tauD, float interval);
+
+    /**
+     * Scale from inputs to 0-100%.
+     *
+     * @param InMin The real world value corresponding to 0%.
+     * @param InMax The real world value corresponding to 100%.
+     */
+    void setInputLimits(float inMin , float inMax);
+
+    /**
+     * Scale from outputs to 0-100%.
+     *
+     * @param outMin The real world value corresponding to 0%.
+     * @param outMax The real world value corresponding to 100%.
+     */
+    void setOutputLimits(float outMin, float outMax);
+
+    /**
+     * Calculate PID constants.
+     *
+     * Allows parameters to be changed on the fly without ruining calculations.
+     *
+     * @param Kc - Tuning parameter
+     * @param tauI - Tuning parameter
+     * @param tauD - Tuning parameter
+     */
+    void setTunings(float Kc, float tauI, float tauD);
+
+    /**
+     * Reinitializes controller internals. Automatically
+     * called on a manual to auto transition.
+     */
+    void reset(void);
+    
+    /**
+     * Set PID to manual or auto mode.
+     *
+     * @param mode        0 -> Manual
+     *             Non-zero -> Auto
+     */
+    void setMode(int mode);
+    
+    /**
+     * Set how fast the PID loop is run.
+     *
+     * @param interval PID calculation peformed every interval seconds.
+     */
+    void setInterval(float interval);
+    
+    /**
+     * Set the set point.
+     *
+     * @param sp The set point as a real world value.
+     */
+    void setSetPoint(float sp);
+    
+    /**
+     * Set the process value.
+     *
+     * @param pv The process value as a real world value.
+     */
+    void setProcessValue(float pv);
+    
+    /**
+     * Set the bias.
+     *
+     * @param bias The bias for the controller output.
+     */
+    void setBias(float bias);
+
+    /**
+     * PID calculation.
+     *
+     * @return The controller output as a float between outMin and outMax.
+     */
+    float compute(void);
+
+    //Getters.
+    float getInMin();
+    float getInMax();
+    float getOutMin();
+    float getOutMax();
+    float getInterval();
+    float getPParam();
+    float getIParam();
+    float getDParam();
+
+private:
+
+    bool usingFeedForward;
+    bool inAuto;
+
+    //Actual tuning parameters used in PID calculation.
+    float Kc_;
+    float tauR_;
+    float tauD_;
+    
+    //Raw tuning parameters.
+    float pParam_;
+    float iParam_;
+    float dParam_;
+    
+    //The point we want to reach.
+    float setPoint_;         
+    //The thing we measure.
+    float processVariable_;  
+    float prevProcessVariable_;
+    //The output that affects the process variable.
+    float controllerOutput_; 
+    float prevControllerOutput_;
+
+    //We work in % for calculations so these will scale from
+    //real world values to 0-100% and back again.
+    float inMin_;
+    float inMax_;
+    float inSpan_;
+    float outMin_;
+    float outMax_;
+    float outSpan_;
+
+    //The accumulated error, i.e. integral.
+    float accError_;
+    //The controller output bias.
+    float bias_;
+
+    //The interval between samples.
+    float tSample_;          
+
+    //Controller output as a real world value.
+    volatile float realOutput_;
+
+};
+
+#endif /* PID_H */