Is there any delay in laser scanner output?

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Hi, I am working on erratic robot and I am running it in gazebo. It has a hokuyo laser scanner on it. I have a question that is there any delay in laser scanner output.

What I am doing here is that I have written a simple code that moves erratic robot and avoids it from obstacles and reaches at goal position. Here I performed a simple experiment 2 or 3 times, I placed an obstacle of same size at same location every time. Now when I move my robot to goal position it avoids and reach at goal position successfully but the problem is that every time robot has a different trajectory.

How can I have same trajectory every time?

Thanks