One Step Closer; Towards Dynamic Walking on AAU-BOT1

Student thesis: Master thesis (including HD thesis)

  • Jes Andersen
  • Henrik Dalsager Christensen
The thesis treats the development of a dynamic walk controller for AAU-BOT1. AAU-BOT1 is a biped robot developed at Aalborg University.

A Biped Robot system, can be described as a hybrid system, as long time spans of the gait are governed by continous motions, and the impacts with the ground can be considered discrete events. Planning a trajectory, and applying it on the system must take this into account.

AAU-BOT1 is physically unable to walk statically, this is partly due to kinematics, and weight distribution, and partly due to the combination of small actuators and large frictions in the joints.

It has been suggested numerous times during the development, that a traditional PID regulator can be used as a servo controller, and that all the non-linear effects, both discrete as well as continuous can be suppressed on the robot. This claim is put to the test in this thesis, as a traditional PID regulator is tuned and applied for the physical system.

The gait is generated on line, based on model prediction, and numeric integration, of a nonlinear inverted 3d pendulum. Applying the trajectory to the robot requires that the implemented PID controller can handle the system sufficiently well, it is however shown that non-linearity's can occur which can destabilize a PID regulator.

Slowing down the trajectory, and keeping the knees stretched counters the problems, and a stable quasi-static gait is achieved.
Publication date3 Jun 2010
Number of pages255
Publishing institutionAalborg University
ID: 32312725