Pid branch revived

lib/lib_div/ProcessControl/PID.cpp

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+/**
+ * Copyright 2018 Colin Law
+ *
+ * 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.
+ *
+ * See Timeprop.h for Usage
+ *
+ **/
+
+
+#include "PID.h"
+
+PID::PID() {
+  m_initialised = 0;
+  m_last_sample_time = 0;
+  m_last_pv_update_time = 0;
+  m_last_power = 0.0;
+}
+
+void PID::initialise( double setpoint, double prop_band, double t_integral, double t_derivative,
+  double integral_default, int max_interval, double smooth_factor, unsigned char mode_auto, double manual_op ) {
+
+  m_setpoint = setpoint;
+  m_prop_band = prop_band;
+  m_t_integral = t_integral;
+  m_t_derivative = t_derivative;
+  m_integral_default = integral_default;
+  m_max_interval = max_interval;
+  m_smooth_factor= smooth_factor;
+  m_mode_auto= mode_auto;
+  m_manual_op = manual_op;
+
+  m_initialised = 1;
+
+}
+
+
+/* called regularly to calculate and return new power value */
+double PID::tick( unsigned long nowSecs ) {
+  double power;
+  double factor;
+  if (m_initialised && m_last_pv_update_time) {
+    // we have been initialised and have been given a pv value
+    // check whether too long has elapsed since pv was last updated
+    if (m_max_interval > 0  &&  nowSecs - m_last_pv_update_time > m_max_interval) {
+      // yes, too long has elapsed since last PV update so go to fallback power
+      power = m_manual_op;
+    } else {
+      // is this the first time through here?
+      if (m_last_sample_time) {
+        // not first time
+        unsigned long delta_t = nowSecs - m_last_sample_time;  // seconds
+        if (delta_t <= 0 || delta_t > m_max_interval) {
+          // too long since last sample so leave integral as is and set deriv to zero
+          m_derivative = 0;
+        } else {
+          if (m_smooth_factor > 0) {
+            // A derivative smoothing factor has been supplied
+            // smoothing time constant is td/factor but with a min of delta_t to stop overflows
+            int ts = m_t_derivative/m_smooth_factor > delta_t ? m_t_derivative/m_smooth_factor : delta_t;
+            factor = 1.0/(ts/delta_t);
+          } else {
+            // no integral smoothing so factor is 1, this makes smoothed_value the previous pv
+            factor = 1.0;
+          }
+          double delta_v = (m_pv - m_smoothed_value) * factor;
+          m_smoothed_value = m_smoothed_value + delta_v;
+          m_derivative = m_t_derivative * delta_v/delta_t;
+          // lock the integral if abs(previous integral + error) > prop_band/2
+          // as this means that P + I is outside the linear region so power will be 0 or full
+          // also lock if control is disabled
+          double error = m_pv - m_setpoint;
+          double pbo2 = m_prop_band/2.0;
+          double epi = error + m_integral;
+          if (epi < 0.0) epi = -epi;    // abs value of error + m_integral
+          if (epi < pbo2  && m_mode_auto) {
+            if (m_t_integral <= 0) {
+              // t_integral is zero (or silly), set integral to one end or the other
+              // or half way if exactly on sp
+              if (error > 0.0) {
+                m_integral = pbo2;
+              } else if (error < 0) {
+                m_integral = -pbo2;
+              } else {
+                m_integral = 0.0;
+              }
+            } else {
+              m_integral = m_integral + error * delta_t/m_t_integral;
+            }
+          }
+          // clamp to +- 0.5 prop band widths so that it cannot push the zero power point outside the pb
+          // do this here rather than when integral is updated to allow for the fact that the pb may change dynamically
+          if ( m_integral < -pbo2 ) {
+            m_integral = -pbo2;
+          } else if (m_integral > pbo2) {
+            m_integral = pbo2;
+          }
+        }
+
+      } else {
+        // first time through, initialise context data
+        m_smoothed_value = m_pv;
+        // setup the integral term so that the power out would be integral_default if pv=setpoint
+        m_integral = (0.5 - m_integral_default)*m_prop_band;
+        m_derivative = 0.0;
+      }
+
+      double proportional = m_pv - m_setpoint;
+      if (m_prop_band == 0) {
+        // prop band is zero so drop back to on/off control with zero hysteresis
+        if (proportional > 0.0) {
+          power = 0.0;
+        } else if (proportional < 0.0) {
+          power = 1.0;
+        } else {
+          // exactly on sp so leave power as it was last time round
+          power = m_last_power;
+        }
+      }
+      else {
+        power = -1.0/m_prop_band * (proportional + m_integral + m_derivative) + 0.5;
+      }
+      // set power to disabled value if the loop is not enabled
+      if (!m_mode_auto) {
+        power = m_manual_op;
+      }
+      m_last_sample_time = nowSecs;
+    }
+  } else {
+    // not yet initialised or no pv value yet so set power to disabled value
+    power = m_manual_op;
+  }
+  if (power < 0.0) {
+    power = 0.0;
+  } else if (power > 1.0) {
+    power = 1.0;
+  }
+  m_last_power = power;
+  return power;
+}
+
+// call to pass in new process value
+void PID::setPv( double pv, unsigned long nowSecs ){
+  m_pv = pv;
+  m_last_pv_update_time = nowSecs;
+}
+
+// methods to modify configuration data
+void PID::setSp( double setpoint ) {
+  m_setpoint = setpoint;
+}
+
+void PID::setPb( double prop_band ) {
+  m_prop_band = prop_band;
+}
+
+void PID::setTi( double t_integral ) {
+  m_t_integral = t_integral;
+}
+
+void PID::setTd( double t_derivative ) {
+  m_t_derivative = t_derivative;
+}
+
+void PID::setInitialInt( double integral_default ) {
+  m_integral_default = integral_default;
+}
+
+void PID::setDSmooth( double smooth_factor ) {
+  m_smooth_factor = smooth_factor;
+}
+
+void PID::setAuto( unsigned char mode_auto ) {
+  m_mode_auto = mode_auto;
+}
+
+void PID::setManualPower( double manual_op ) {
+  m_manual_op = manual_op;
+}
+
+void PID::setMaxInterval( int max_interval ) {
+  m_max_interval = max_interval;
+}
+
+
+double PID::getPv() {
+  return(m_pv);
+}
+
+double PID::getSp() {
+  return(m_setpoint);
+}
+
+double PID::getPb() {
+  return(m_prop_band);
+}
+
+double PID::getTi() {
+  return(m_t_integral);
+}
+
+double PID::getTd() {
+  return(m_t_derivative);
+}
+
+double PID::getInitialInt() {
+  return(m_integral_default);
+}
+
+double PID::getDSmooth() {
+  return(m_smooth_factor);
+}
+
+unsigned char PID::getAuto() {
+  return(m_mode_auto);
+}
+
+double PID::getManualPower() {
+  return(m_manual_op);
+}
+
+int PID::getMaxInterval() {
+  return(m_max_interval);
+}

lib/lib_div/ProcessControl/PID.h

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+/**
+ * Copyright 2018 Colin Law
+ *
+ * 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.
+ **/
+
+ /**
+  * A PID control class
+  *
+  * Github repository https://github.com/colinl/process-control.git
+  *
+  * Given ...
+  *
+  * Usage:
+  * First call initialise(), see below for parameters then
+  * ...
+  * The functions require a parameter nowSecs which is a representation of the
+  * current time in seconds. The absolute value of this is immaterial, it is
+  * used for relative timing only.
+  *
+ **/
+
+
+#ifndef PID_h
+#define PID_h
+
+class PID {
+public:
+
+  PID();
+
+  /*
+    Initialiser given
+
+      current time in seconds
+  */
+  void initialise( double setpoint, double prop_band, double t_integral, double t_derivative,
+    double integral_default, int max_interval, double smooth_factor, unsigned char mode_auto, double manual_op );
+
+
+  /* called regularly to calculate and return new power value */
+  double tick(unsigned long nowSecs);
+
+  // call to pass in new process value
+  void setPv( double pv, unsigned long nowSecs );
+
+  // methods to modify configuration data
+  void setSp( double setpoint );
+  void setPb( double prop_band );
+  void setTi( double t_integral );
+  void setTd( double t_derivative );
+  void setInitialInt( double integral_default );
+  void setDSmooth( double smooth_factor );
+  void setAuto( unsigned char mode_auto );
+  void setManualPower( double manual_op );
+  void setMaxInterval( int max_interval );
+
+  double getPv();
+  double getSp();
+  double getPb();
+  double getTi();
+  double getTd();
+  double getInitialInt();
+  double getDSmooth();
+  unsigned char getAuto();
+  double getManualPower();
+  int getMaxInterval();
+
+private:
+  double m_pv;
+  double m_setpoint;
+  double m_prop_band;
+  double m_t_integral;
+  double m_t_derivative;
+  double m_integral_default;
+  double m_smooth_factor;
+  unsigned char m_mode_auto;
+  double m_manual_op;
+  int m_max_interval;
+  double m_last_power;
+
+
+  unsigned char m_initialised;
+  unsigned long m_last_pv_update_time;   // the time of last pv update secs
+  unsigned long m_last_sample_time;   // the time of the last tick() run
+  double m_smoothed_value;
+  double m_integral;
+  double m_derivative ;
+};
+
+#endif // Timeprop_h