1 files changed, 34 insertions, 36 deletions

diff --git a/src/modules/systemlib/pid/pid.c b/src/modules/systemlib/pid/pid.c
index 2aafe0636..9308100b0 100644
--- a/src/modules/systemlib/pid/pid.c
+++ b/src/modules/systemlib/pid/pid.c
@@ -1,9 +1,11 @@
 /****************************************************************************
  *
- *   Copyright (C) 2008-2012 PX4 Development Team. All rights reserved.
- *   Author: @author Laurens Mackay <mackayl@student.ethz.ch>
- *           @author Tobias Naegeli <naegelit@student.ethz.ch>
- *           @author Martin Rutschmann <rutmarti@student.ethz.ch>
+ *   Copyright (C) 2008-2013 PX4 Development Team. All rights reserved.
+ *   Author: Laurens Mackay <mackayl@student.ethz.ch>
+ *           Tobias Naegeli <naegelit@student.ethz.ch>
+ *           Martin Rutschmann <rutmarti@student.ethz.ch>
+ *           Anton Babushkin <anton.babushkin@me.com>
+ *           Julian Oes <joes@student.ethz.ch>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -36,14 +38,21 @@
 
 /**
  * @file pid.c
- * Implementation of generic PID control interface
+ *
+ * Implementation of generic PID control interface.
+ *
+ * @author Laurens Mackay <mackayl@student.ethz.ch>
+ * @author Tobias Naegeli <naegelit@student.ethz.ch>
+ * @author Martin Rutschmann <rutmarti@student.ethz.ch>
+ * @author Anton Babushkin <anton.babushkin@me.com>
+ * @author Julian Oes <joes@student.ethz.ch>
  */
 
 #include "pid.h"
 #include <math.h>
 
 __EXPORT void pid_init(PID_t *pid, float kp, float ki, float kd, float intmax,
-		       float limit, float diff_filter_factor, uint8_t mode)
+		       float limit, uint8_t mode, float dt_min)
 {
 	pid->kp = kp;
 	pid->ki = ki;
@@ -51,17 +60,15 @@ __EXPORT void pid_init(PID_t *pid, float kp, float ki, float kd, float intmax,
 	pid->intmax = intmax;
 	pid->limit = limit;
 	pid->mode = mode;
-	pid->diff_filter_factor = diff_filter_factor;
+	pid->dt_min = dt_min;
 	pid->count = 0.0f;
 	pid->saturated = 0.0f;
 	pid->last_output = 0.0f;
-
 	pid->sp = 0.0f;
-	pid->error_previous_filtered = 0.0f;
-	pid->control_previous = 0.0f;
+	pid->error_previous = 0.0f;
 	pid->integral = 0.0f;
 }
-__EXPORT int pid_set_parameters(PID_t *pid, float kp, float ki, float kd, float intmax, float limit, float diff_filter_factor)
+__EXPORT int pid_set_parameters(PID_t *pid, float kp, float ki, float kd, float intmax, float limit)
 {
 	int ret = 0;
 
@@ -100,13 +107,6 @@ __EXPORT int pid_set_parameters(PID_t *pid, float kp, float ki, float kd, float
 		ret = 1;
 	}
 
-	if (isfinite(diff_filter_factor)) {
-		pid->diff_filter_factor = diff_filter_factor;
-
-	}  else {
-		ret = 1;
-	}
-
 	return ret;
 }
 
@@ -144,20 +144,16 @@ __EXPORT float pid_calculate(PID_t *pid, float sp, float val, float val_dot, flo
 
 	// Calculated current error value
 	float error = pid->sp - val;
-	float error_filtered;
 
 	// Calculate or measured current error derivative
-
 	if (pid->mode == PID_MODE_DERIVATIV_CALC) {
+		d = (error - pid->error_previous) / fmaxf(dt, pid->dt_min);
+		pid->error_previous = error;
 
-		error_filtered = pid->error_previous_filtered + (error - pid->error_previous_filtered) * pid->diff_filter_factor;
-		d = (error_filtered - pid->error_previous_filtered) / fmaxf(dt, 0.003f);		// fail-safe for too low dt
-		pid->error_previous_filtered = error_filtered;
 	} else if (pid->mode == PID_MODE_DERIVATIV_CALC_NO_SP) {
+		d = (-val - pid->error_previous) / fmaxf(dt, pid->dt_min);
+		pid->error_previous = -val;
 
-		error_filtered = pid->error_previous_filtered + (- val - pid->error_previous_filtered) * pid->diff_filter_factor;
-		d = (error_filtered - pid->error_previous_filtered) / fmaxf(dt, 0.003f);		// fail-safe for too low dt
-		pid->error_previous_filtered = error_filtered;
 	} else if (pid->mode == PID_MODE_DERIVATIV_SET) {
 		d = -val_dot;
 
@@ -165,6 +161,10 @@ __EXPORT float pid_calculate(PID_t *pid, float sp, float val, float val_dot, flo
 		d = 0.0f;
 	}
 
+	if (!isfinite(d)) {
+		d = 0.0f;
+	}
+
 	// Calculate the error integral and check for saturation
 	i = pid->integral + (error * dt);
 
@@ -175,7 +175,7 @@ __EXPORT float pid_calculate(PID_t *pid, float sp, float val, float val_dot, flo
 
 	} else {
 		if (!isfinite(i)) {
-			i = 0;
+			i = 0.0f;
 		}
 
 		pid->integral = i;
@@ -184,19 +184,17 @@ __EXPORT float pid_calculate(PID_t *pid, float sp, float val, float val_dot, flo
 
 	// Calculate the output.  Limit output magnitude to pid->limit
 	float output = (error * pid->kp) + (i * pid->ki) + (d * pid->kd);
-	if (output > pid->limit) output = pid->limit;
-
-	if (output < -pid->limit) output = -pid->limit;
 
 	if (isfinite(output)) {
-		pid->last_output = output;
-	}
+		if (output > pid->limit) {
+			output = pid->limit;
 
-	pid->control_previous = pid->last_output;
+		} else if (output < -pid->limit) {
+			output = -pid->limit;
+		}
 
-	// if (isfinite(error)) {				// Why is this necessary?  DEW
-	// 	pid->error_previous = error;
-	// }
+		pid->last_output = output;
+	}
 
 	*ctrl_p = (error * pid->kp);
 	*ctrl_i = (i * pid->ki);