Interpetting a stream of cmd_vels

edit

Investigating weird observed behavior of my TurtleBot3 (previous question: #q300209) I monitored the cmd_vel topic during the observed behavior. The conditions are as follows:

• turtlebot3 running kinetic
• map made by gmapping followed by teleoping to visit the maze
• I changed the resolution of the map from 0.05 to 0.01 (I don't think this matters)
• Saved the map
• Stopped gmapping
• start navigation

The robot was able to navigate to a variety of corners of the maze relatively well (it did get confused often.) but when I set up a goal where it would try to drive in reverse (twist x < 0) it would exhibit the bucking behavior. And looking at the cmd_vel message stream I did indeed see negative cmd_vels right next to positive ones. I was not running any teleop at the time. Here is some of the data. I had to search for it but you see negative x's next to positive x's. The maximum linear speed specified for TurtleBot3 is 0.22 so -0.11 is about half the maximum.

Any comments on whether this is normal or weird? And whether this can explain the "bucking" (very intense shuddering motion) that I've reported seeing?

linear: 
  x: -0.113387688994
  y: 0.0
  z: 0.0
angular: 
  x: 0.0
  y: 0.0
  z: -0.661418616772
---
linear: 
  x: -0.12927775085
  y: 0.0
  z: 0.0
angular: 
  x: 0.0
  y: 0.0
  z: -0.976840138435
---
linear: 
  x: 0.126691520214
  y: 0.0
  z: 0.0
angular: 
  x: 0.0
  y: 0.0
  z: -1.05274891853
---
linear: 
  x: -0.148515239358
  y: 0.0
  z: 0.0
angular: 
  x: 0.0
  y: 0.0
  z: -0.77896797657
---
linear: 
  x: -0.127474233508
  y: 0.0
  z: 0.0
angular: 
  x: 0.0
  y: 0.0
  z: -0.721023142338
---
linear: 
  x: 0.134267643094
  y: 0.0
  z: 0.0
angular: 
  x: 0.0
  y: 0.0
  z: -1.08932781219
---