Is it possible to time synchronize two topics in ROS of same message type?

问题

I try to map robot gripper position to the resistance exerted by the object held by the gripper. I subscribed the gripper position from one topic and resistance value from another topic, since I want to ensure that the gripper position corresponds to the exact resistance value at that position. Given that both are float messages, how can I synchronize them?

self.sub1 = rospy.Subscriber("resistance", Float64, self.ard_callback)
self.sub2 = rospy.Subscriber("gripperpos", Float64, self.grip_callback)

回答1:

You could use TimeSynchronizer in rospy.

This is an example to subscribe to multiple topics to get data at the same time:

import message_filters
from sensor_msgs.msg import Image, CameraInfo

def callback(image, camera_info):
  # Solve all of perception here...

image_sub = message_filters.Subscriber('image', Image)
info_sub = message_filters.Subscriber('camera_info', CameraInfo)

ts = message_filters.TimeSynchronizer([image_sub, info_sub], 10)
ts.registerCallback(callback)
rospy.spin()

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If your problem not resolved, there is ApproximateTimeSynchronizer rather than TimeSynchronizer:

ts = message_filters.ApproximateTimeSynchronizer([image_sub, info_sub], 1, 1)  

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来源：https://stackoverflow.com/questions/55458218/is-it-possible-to-time-synchronize-two-topics-in-ros-of-same-message-type