From: Erik Andresen <erik@vontaene.de>
Date: Sat, 30 Jun 2018 15:29:58 +0000 (+0200)
Subject: dwm1000: Use kalman filter for beacon position, not dwm distance
X-Git-Url: https://defiant.homedns.org/gitweb/?p=ros_wild_thumper.git;a=commitdiff_plain;h=bce85b0847856bfd601c434bfdb8ff57ea44fcde;ds=sidebyside

dwm1000: Use kalman filter for beacon position, not dwm distance

Includes position correction from odometry
---

diff --git a/scripts/dwm1000.py b/scripts/dwm1000.py
index 06c6cbc..69ce1c0 100755
--- a/scripts/dwm1000.py
+++ b/scripts/dwm1000.py
@@ -7,10 +7,12 @@ import threading
 import struct
 import rospy
 import tf
-from std_msgs.msg import Float32
+import numpy as np
 from math import *
 from i2c import i2c
 from time import sleep
+from std_msgs.msg import Float32
+from nav_msgs.msg import Odometry
 if VISULAIZE:
 	import matplotlib.pyplot as plt
 
@@ -43,16 +45,9 @@ class DW1000(threading.Thread):
 		threading.Thread.__init__(self)
 		self.setDaemon(1)
 		self.dist = 0
-		self.dist_filter = 0
 		self.offset = offset
 		self.addr = addr
 
-		x_est = 1.0 # Systemzustand
-		P_est = 0.003 # Fehlerkovarianz
-		Q = 10e-4 # Systemrauschen
-		R = 0.05 # Varianz des Messfehlers
-		self.filter = simple_kalman(x_est, P_est, Q, R)
-
 		self.pub = rospy.Publisher(name, Float32, queue_size=16)
 
 		self.start()
@@ -64,21 +59,63 @@ class DW1000(threading.Thread):
 		return ret[0]
 
 	def distance(self):
-		return self.dist_filter
+		return self.dist
 
 	def run(self):
 		while True:
 			self.dist = self.get_value() + self.offset
-			self.dist_filter = self.filter.run(self.dist)
-			self.pub.publish(self.dist_filter)
+			self.pub.publish(self.distance())
 			sleep(0.1)
 
+class Position:
+	def __init__(self):
+		P_est = 0.003 # Fehlerkovarianz
+		Q = 10e-4 # Systemrauschen
+		R = 0.1 # Varianz des Messfehlers
+		self.filter_x = simple_kalman(1.0, P_est, Q, R)
+		self.filter_y = simple_kalman(0.0, P_est, Q, R)
+		self.speed_x = 0
+		self.speed_y = 0
+		self.speed_z = 0
+		self.last_time = rospy.Time.now()
+		rospy.Subscriber("/odom_combined", Odometry, self.odomReceived)
+
+	def odomReceived(self, msg):
+		self.speed_x = msg.twist.twist.linear.x
+		self.speed_y = msg.twist.twist.linear.y
+		self.speed_z = msg.twist.twist.angular.z
+
+	def filter(self, x, y):
+		# Correct estimation with speed
+		current_time = rospy.Time.now()
+		dt = (current_time - self.last_time).to_sec()
+		# Subtract vehicle speed
+		pos = np.array([self.filter_x.x_est, self.filter_y.x_est])
+		# translation
+		pos -= np.array([self.speed_x*dt, self.speed_y*dt])
+		# rotation
+		rot = np.array([[np.cos(self.speed_z*dt), -np.sin(self.speed_z*dt)],
+				[np.sin(self.speed_z*dt),  np.cos(self.speed_z*dt)]])
+		pos = np.dot(pos, rot)
+		# copy back
+		self.filter_x.x_est = pos[0]
+		self.filter_y.x_est = pos[1]
+
+		# run kalman
+		x = self.filter_x.run(x)
+		y = self.filter_y.run(y)
+
+		self.last_time = current_time
+		return x,y
+
+
 if __name__ == "__main__":
 	rospy.init_node('DW1000')
 	dwleft  = DW1000("uwb_dist_left",  0xc2, +0.0)
 	dwright = DW1000("uwb_dist_right", 0xc0, -0.0)
 	dist_l_r = 0.285
 	rate = rospy.Rate(10)
+	pos = Position()
 	tf_broadcaster = tf.broadcaster.TransformBroadcaster()
 
 	while not rospy.is_shutdown() and dwleft.is_alive() and dwright.is_alive():
@@ -96,7 +133,7 @@ if __name__ == "__main__":
 			else:
 				dist_left += off/2
 				dist_right -= off/2
-		print "%.2f %.2f %.2f %.2f %.2f %.2f %s" % (dwleft.dist, dwright.dist, dwleft.dist_filter, dwright.dist_filter, dist_left, dist_right, dir)
+		print "%.2f %.2f %.2f %.2f %s" % (dwleft.distance(), dwright.distance(), dist_left, dist_right, dir)
 
 		a_r = (-dist_right**2 + dist_left**2 - dist_l_r**2) / (-2*dist_l_r)
 		x = dist_l_r/2 - a_r
@@ -104,8 +141,11 @@ if __name__ == "__main__":
 		if t >= 0:
 			y = sqrt(t)
 			print x,y
-			# Rotated 90 deg
-			tf_broadcaster.sendTransform((y, -x, 0.0), (0, 0, 0, 1), rospy.Time.now(), "uwb_beacon", "base_footprint")
+			# Rotate 90 deg
+			x, y = (y, -x)
+
+			x, y = pos.filter(x, y)
+			tf_broadcaster.sendTransform((x, y, 0.0), (0, 0, 0, 1), rospy.Time.now(), "uwb_beacon", "base_footprint")
 
 			if VISULAIZE:
 				circle_left = plt.Circle((-dist_l_r/2, 0), dwleft.distance, color='red', fill=False)