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https://github.com/bjoernellens1/cps_rmp220_support.git
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113 lines
3.6 KiB
Python
113 lines
3.6 KiB
Python
#!/usr/bin/env python
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import rospy
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import tf
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from nav_msgs.msg import Odometry
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from std_msgs.msg import Header
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from segway_msgs.msg import ticks_fb # Correct message import
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import math
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class EncoderOdometry:
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def __init__(self):
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rospy.init_node("encoder_odom_publisher")
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# Robot parameters (update these according to your robot)
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self.wheel_radius = 0.05 # Wheel radius in meters
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self.wheel_base = 0.3 # Distance between wheels (m)
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self.ticks_per_revolution = 1000 # Encoder ticks per wheel revolution
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# State variables
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self.x = 0.0
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self.y = 0.0
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self.theta = 0.0
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self.last_l_ticks = None
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self.last_r_ticks = None
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self.last_time = None
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# ROS publishers (Updated topic to /odom_new)
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self.odom_pub = rospy.Publisher("/odom_new", Odometry, queue_size=10)
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self.odom_broadcaster = tf.TransformBroadcaster()
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# ROS subscriber to /ticks_fb topic
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rospy.Subscriber("/ticks_fb", ticks_fb, self.ticks_callback)
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rospy.spin()
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def ticks_callback(self, msg):
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if self.last_l_ticks is None or self.last_r_ticks is None or self.last_time is None:
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self.last_l_ticks = msg.l_ticks
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self.last_r_ticks = msg.r_ticks
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self.last_time = msg.ticks_timestamp / 1e6 # Convert to seconds
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return
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# Compute time delta
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current_time = msg.ticks_timestamp / 1e6 # Convert to seconds
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dt = current_time - self.last_time
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if dt <= 0:
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return # Skip if time is invalid
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# Compute tick differences
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delta_l = msg.l_ticks - self.last_l_ticks
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delta_r = msg.r_ticks - self.last_r_ticks
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# Convert ticks to meters
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meters_per_tick = (2 * math.pi * self.wheel_radius) / self.ticks_per_revolution
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delta_s_l = delta_l * meters_per_tick
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delta_s_r = delta_r * meters_per_tick
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# Compute linear and angular velocity
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v = (delta_s_l + delta_s_r) / 2.0 / dt
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omega = (delta_s_r - delta_s_l) / self.wheel_base / dt
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# Integrate motion (basic differential drive kinematics)
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delta_theta = omega * dt
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self.theta += delta_theta
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delta_x = v * math.cos(self.theta) * dt
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delta_y = v * math.sin(self.theta) * dt
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self.x += delta_x
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self.y += delta_y
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# Create odometry message
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odom = Odometry()
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odom.header = Header(stamp=rospy.Time.from_sec(current_time), frame_id="odom")
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odom.child_frame_id = "base_link"
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# Position
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odom.pose.pose.position.x = self.x
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odom.pose.pose.position.y = self.y
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odom.pose.pose.position.z = 0.0
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# Orientation (as quaternion)
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q = tf.transformations.quaternion_from_euler(0, 0, self.theta)
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odom.pose.pose.orientation.x = q[0]
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odom.pose.pose.orientation.y = q[1]
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odom.pose.pose.orientation.z = q[2]
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odom.pose.pose.orientation.w = q[3]
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# Velocities
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odom.twist.twist.linear.x = v
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odom.twist.twist.angular.z = omega
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# Publish odometry to /odom_new
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self.odom_pub.publish(odom)
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# Publish TF transform
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self.odom_broadcaster.sendTransform(
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(self.x, self.y, 0),
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q,
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rospy.Time.from_sec(current_time),
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"base_link",
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"odom"
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)
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# Update previous values
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self.last_l_ticks = msg.l_ticks
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self.last_r_ticks = msg.r_ticks
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self.last_time = current_time
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if __name__ == "__main__":
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try:
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EncoderOdometry()
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except rospy.ROSInterruptException:
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pass
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