Simulating Small Differential Drive Robot in Gazebo

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Hi,

I am trying to simulate a small 4WD differential drive robot in Gazebo. I am using the erratic_gazebo_plugin diffdrive_plugin controller which I modified to work with a 4WD system.

My simulation works fine when I use the erratic's wheel diameter of .15 m. But when I change the diameter to .1 m for my wheels the odometry published claims the robot is moving at .7 m/s despite me commanding 1 m/s in the Twist msg.

I am using a moment of inertia of ixx = 0.01 ;ixy = 0 ; ixz = 0 ; iyy= .01 ; iyz = 0 ; izz = .01.

My wheel mass is .1 kg

I think my issue has to do with the mu1, mu2, kp, and kd parameters currently I have them set at mu1 = 200 ; mu2 = 100 ; kp = 1000000 ; and kd = 1.

I guess my issue is I am unclear how these parameters are used in the simulator as well as what is the effect decreasing the wheel diameter. I can trick the simulator by decreasing my wheel diameter in the controller's parameters but I would like to understand why this phenomenon occurs.

Any help would be much appreciated.

Thanks, Matt