can i stop a urdf model using moveit based on signals from two ultrasonic sensors

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I created two separate node which is subscribed to two separate ultrasonic range message individually.That is each node is subscribed to only one ultrasonic range message.Based on some threshold of ultrasonic range i stopped the urdf model from path planning. other wise it is randomly executing some path.For node 2 i gave only one condition,that is this node will not execute any trajectory but stops the robot when ultrasonic range crosses the threshold.I want to stop the robot if node2 receives stop signal while node1 is executing a trajectory.I implemented this using move it and i use group.stop() function to stop the robot. But the robot is not stopping . What is the reason ,can anyone help me?