Getting different results on different pc

asked 2019-12-20 04:36:37 -0600

So I am running a simulation of a simple ground robot via ROS. I am using ROS Kinetic and Gazebo 7 on both my laptop and pc.

I first ran it on my laptop, making sure to set the flag "use_sim_time" to true. I send out a constant cmd_vel of -0.6 around the z-axis. I expected the robot in my simulation to rotate around it's z-axis clockwise at a constant speed, yet it didn't. As you can see in the bottom picture (the top graph labeled laptop).

My laptop is old and slow, so I assumed it might be that it just can't run it properly (i5, intel graphics, nothing fancy). I decided to run the test again on my pc (i7, 16gb ram, nvidia geforce gtx 980). I assumed that the problem would be resolved and my robot would rotate around a constant speed.

What I noticed is two things, first (looking at the bottom pic) both times during my simulation, the speed at which my robot rotates is anything but constant. They also both have similar patterns, yet individually there seems to be a repeating pattern in the speeds. The second thing I noticed is that, by looking at the top picture, the speed of the two simulations isn't equal. In the simulation of my laptop, the speed ends up around -0.6. On my pc on the other hand, the speed ends up around 0.8.

Now for my actual question part, why does my simulation behave differently on two different systems and why is my speed not constant? If anybody would be able to help me solve my problems, it would be greatly appreciated.

image description

first graph is on my laptop, the second one on my pc. This is the angle around the z-axis of my robot as given by the gazebo/model_states topic. The x-axis of the graph is in ms

image description

first graph is on my laptop, the second one on my pc. This is the velocity around the z-axis of my robot as given by the gazebo/model_states topic. The x-axis of the graph is in ms

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