From: Erik Andresen <erik@vontaene.de>
Date: Fri, 29 Jun 2018 09:47:36 +0000 (+0200)
Subject: Added dwm1000 script to localize tf beacon
X-Git-Url: https://defiant.homedns.org/gitweb/?a=commitdiff_plain;h=fd4e260862571dbce04d1e2777f5507dffed4348;p=ros_wild_thumper.git

Added dwm1000 script to localize tf beacon
---

diff --git a/scripts/dwm1000.py b/scripts/dwm1000.py
new file mode 100755
index 0000000..06c6cbc
--- /dev/null
+++ b/scripts/dwm1000.py
@@ -0,0 +1,119 @@
+#!/usr/bin/env python
+# -*- coding: iso-8859-15 -*-
+
+VISULAIZE = False
+
+import threading
+import struct
+import rospy
+import tf
+from std_msgs.msg import Float32
+from math import *
+from i2c import i2c
+from time import sleep
+if VISULAIZE:
+	import matplotlib.pyplot as plt
+
+class simple_kalman:
+	def __init__(self, x_est, P_est, Q, R):
+		self.x_est = x_est # Systemzustand
+		self.P_est = P_est # Fehlerkovarianz
+		self.Q = Q # Systemrauschen
+		self.R = R # Varianz des Messfehlers
+
+	def run(self, y):
+		# Korrektur mit der Messung
+		# (1) Berechnung der Kalman Verstärkung
+		K = self.P_est/(self.R + self.P_est)
+		# (2) Korrektur der Schätzung mit der Messung y
+		x = self.x_est + K*(y - self.x_est)
+		# (3) Korrektur der Fehlerkovarianzmatrix
+		P = (1-K)*self.P_est
+		#
+		# Prädiktion
+		# (1) Prädiziere den Systemzustand
+		self.x_est = x
+		# (2) Präzidiere die Fehlerkovarianzmatrix
+		self.P_est = P + self.Q
+
+		return x
+
+class DW1000(threading.Thread):
+	def __init__(self, name, addr, offset):
+		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()
+
+	def get_value(self):
+		dev = i2c(self.addr)
+		ret = struct.unpack("f", dev.read(4))
+		dev.close()
+		return ret[0]
+
+	def distance(self):
+		return self.dist_filter
+
+	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)
+			sleep(0.1)
+
+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)
+	tf_broadcaster = tf.broadcaster.TransformBroadcaster()
+
+	while not rospy.is_shutdown() and dwleft.is_alive() and dwright.is_alive():
+		dist_left = dwleft.distance()
+		dist_right = dwright.distance()
+		dir = "left" if (dist_left < dist_right) else "right"
+
+		diff = abs(dist_left - dist_right)
+		if diff >= dist_l_r:
+			# difference to high, correct to maximum
+			off = diff - dist_l_r + 0.01
+			if dist_left > dist_right:
+				dist_left -= off/2
+				dist_right += off/2
+			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)
+
+		a_r = (-dist_right**2 + dist_left**2 - dist_l_r**2) / (-2*dist_l_r)
+		x = dist_l_r/2 - a_r
+		t = dist_right**2 - a_r**2
+		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")
+
+			if VISULAIZE:
+				circle_left = plt.Circle((-dist_l_r/2, 0), dwleft.distance, color='red', fill=False)
+				circle_right = plt.Circle((dist_l_r/2, 0), dwright.distance, color='green', fill=False)
+				plt.gca().add_patch(circle_left)
+				plt.gca().add_patch(circle_right)
+				plt.grid(True)
+				plt.axis('scaled')
+				plt.show()
+
+		rate.sleep()