rrt_exploration when running the demo, there is no blue trajectory

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I tried to run the demo by following the video, but there are no blue trajectories. Besides, the robot will stop after several steps, and it won't explore the full map. I have tried to eliminate all the warnings but there is one left

[ WARN] [1558430783.125936027, 2376.030000000]: Timed out waiting for transform from robot_1/base_link to robot_1/map to become available before running costmap, tf error: canTransform: target_frame robot_1/map does not exist.. canTransform returned after 2376.03 timeout was 0.1.

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