Simulator v. reality

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The robot, the simulator and the DH parameters

We have three modules performing angle to cartesian coordinates conversion:

  • The robot
  • the simulator
  • any forward kinematics from the robot's DH parameters (e.g. KDL library)

The robot appears to match the KDL kinematics from the DH parameters. The differences are probably due to errors in the calibration of the encoders. A better calibration procedure (for example using the inertial sensor of the robot placed in the hand) could fix this.

The simulator and the KDL kinematics do not match very well. We do not know what is the cause of this, it could be due to a misalignment between reference frames or errors in the kinematic parameters of the simulator. Since robot and DH parameters seem to be in agreement, we suspect the problem could be in the simulator. Vincent is going to check this with Vadim.

Outcome

The DH parameters were not in sync with the robot. There were also some issues with the simulator. See VVV08 Grasping Group page for corrected parameters, which at the time of writing (July 2008) are being propagated to the "official" documentation (should be done shortly).