Using a Symmetric Rotor as a Tool for Balancing

In the Humanoid Leagues balancing during walking and running is still the biggest challenge for most of the teams. We present here some work in which a dynamic walker is stabilised by using a fast heavy rotor, a gyro. The dynamics of a symmetric, fast rotating gyro is different from that of a non-rotating solid body, e.g. in the case of small disturbances it tends to keep the axes the same. Results show that the rotor enhances the stability of the walking in the simulations. In a model for an actuated robot the rotor is used as a reaction wheel, i.e. the pitch of the robot is stabilised by accelerating and decelerating it. We see this method –though it is not biologically inspired – as an intermediate step for learning balancing in biped robots. The control algorithm responsible for balancing the pitch is discussed in detail. The simulations show that, by using this kind of stabilisation, movements like stand up, walk and jump are easily possible by using open loop control for the legs, however high torques for the rotor are necessary. Finally, a robot design that consists just of a trunk is presented.