Addition automatic ki calculation and small improvement

- Addition of automatic calculation of ki with the task period time since
the arm_pid function need ki*t and not ki for the initialisation.
- Small improvement for the anti WindUp calculation with arm functions
- Addition of a counter for the reset of the pid when the electrical source
is off to avoid inopportune reset with an error of measure.
- Addition of Vsat verification which is the minimum voltage required for the entry
to suit the Vref

src/opalib_pid.c

@@ -58,6 +58,10 @@ static float32_t Vref;
 static float32_t V1_value, Vhigh_value;
 static float32_t error_pid;
 static arm_pid_instance_f32 PID_variables;
+static uint32_t pid_period_us; //The period where the pid is calculated (used for Ki calculation)
+static float32_t WindUp_sub, WindUp_mult; // Transition variables for arm calculation of the WindUp
+static uint32_t Count_pid_reset; // Counter to reset the PID when calculation is off 
+static float32_t Vsat; // Represent the minimum voltage required for the entry to suit the Vref
 static float32_t pid_out_windUp = 0.1;     // stores the current pid output after anti windup and before saturation
 static float32_t prev_pid_out = 0.1; 	// stores the previous unsaturated output
 static float32_t pid_out;        // stores the current pid_output after saturation and anti windUp (the effective duty cycle)
@@ -76,17 +80,19 @@ static uint16_t pwm_period, pwm_phase_shift, pwm_low_pulse_width, pwm_high_pulse
  * This function initializes all the parameters
  * needed for the PID calculation for the buck topoligy
  */
-void pid_init_buck(float32_t vref, float32_t kp, float32_t ki, float32_t kd)
+void pid_init_buck(float32_t vref, float32_t kp, float32_t ki, float32_t kd, uint32_t task_period_us)
 {
 	pwm_period = leg_period();
 	pwm_phase_shift = pwm_period / 2;
 	pwm_low_pulse_width = pwm_period * LOW_DUTY;
 	pwm_high_pulse_width = pwm_period * HIGH_DUTY;
+	pid_period_us = task_period_us;
 
 	Vref = vref;
+	Vsat = Vref/0.9;	// Calculation of the minimum voltage required for the entry to suit the Vref
 
 	PID_variables.Kp = kp;
-	PID_variables.Ki = ki;
+	PID_variables.Ki = ki*pid_period_us/1000000.;
 	PID_variables.Kd = kd;
 
 	arm_pid_init_f32(&PID_variables, 1);
@@ -96,16 +102,18 @@ void pid_init_buck(float32_t vref, float32_t kp, float32_t ki, float32_t kd)
  * This function initializes all the parameters
  * needed for the PID calculation for the boost topoligy
  */
-void pid_init_boost(float32_t vref, float32_t kp, float32_t ki, float32_t kd)
+void pid_init_boost(float32_t vref, float32_t kp, float32_t ki, float32_t kd, uint32_t task_period_us)
 {
 	pwm_phase_shift = pwm_period / 2;
 	pwm_low_pulse_width = pwm_period * LOW_DUTY;
 	pwm_high_pulse_width = pwm_period * HIGH_DUTY;
+	pid_period_us = task_period_us;
 
 	Vref = vref;
+	Vsat = Vref/(1-0.9); // Calculation of the minimum voltage required for the entry to suit the Vref
 
 	PID_variables.Kp = kp;
-	PID_variables.Ki = ki;
+	PID_variables.Ki = ki*pid_period_us/1000000.;
 	PID_variables.Kd = kd;
 
 	arm_pid_init_f32(&PID_variables, 1);
@@ -126,12 +134,14 @@ void pid_calculation_and_pwm_update()
 	Vhigh_value = get_value_converted(2 , 2);
 	arm_sub_f32(&Vref, &V1_value, &error_pid, 1);		// CALCULATING THE ERROR BASED ON THE REFERENCE
 	
-	if (Vhigh_value > Vref)
+	if (Vhigh_value > Vsat)
 	{
 		pid_out = arm_pid_f32(&PID_variables, error_pid);	        // PID CALCULATIONS
 
 		//PID anti WindUp saturation 
-		pid_out_windUp = pid_out + Kw * (pwm_duty_cycle - prev_pid_out);
+		arm_sub_f32(&pwm_duty_cycle, &prev_pid_out, &WindUp_sub, 1);
+		arm_mult_f32(&WindUp_sub, &Kw, &WindUp_mult, 1);
+		arm_add_f32(&WindUp_mult, &pid_out, &pid_out_windUp, 1);
 		PID_variables.state[2] = pid_out_windUp;
 		pwm_duty_cycle = pid_out_windUp;
 		prev_pid_out = pid_out;
@@ -160,14 +170,23 @@ void pid_calculation_and_pwm_update()
 			leg_set(TIMA, pwm_pulse_width, 0);
 			leg_set(TIMB, pwm_pulse_width, pwm_phase_shift);	
 		}		
+
+		Count_pid_reset = 0;
 	}
 	
 	else
 	{
-		arm_pid_reset_q31(&PID_variables);
+		// Prevent from intempestive reset 
+		if (Count_pid_reset > 100)
+		{
+			arm_pid_reset_f32(&PID_variables);
+			Count_pid_reset = 100;
+		}
+
 		pwm_duty_cycle = LOW_DUTY;
 		leg_set(TIMA, pwm_low_pulse_width, 0);
 		leg_set(TIMB, pwm_low_pulse_width, pwm_phase_shift);	
+		Count_pid_reset++;
 	}	
 }
 

src/opalib_pid.h

@@ -40,7 +40,7 @@ extern "C" {
  * @param[in] ki     ki for PID
  * @param[in] kd     kd for PID
  */
-void pid_init_buck(float32_t vref, float32_t kp, float32_t ki, float32_t kd);
+void pid_init_buck(float32_t vref, float32_t kp, float32_t ki, float32_t kd, uint32_t task_period_us);
 
 /**
  * @brief     This function Initialize all the parameters
@@ -51,7 +51,7 @@ void pid_init_buck(float32_t vref, float32_t kp, float32_t ki, float32_t kd);
  * @param[in] ki     ki for PID
  * @param[in] kd     kd for PID
  */
-void pid_init_boost(float32_t vref, float32_t kp, float32_t ki, float32_t kd);
+void pid_init_boost(float32_t vref, float32_t kp, float32_t ki, float32_t kd, uint32_t task_period_us);
 
 /**
  * @brief     This function calculation of the PID for the chosen