Biologically-Inspired Control Architecture

The biologically-inspired control architecture has two main advantages compared to traditional feedback control architectures:
1) The co-contraction and therefore, the stiffness is reduced during reaching movements
2) The proprioceptive feedback will adjust the activation based on where the arm is during the reach.

The reduction of co-contraction and lower stiffness results in safer operation for human-humanoid interaction and in movement that is smoother because the muscles do not pull against each other more than is necessary to produce the motion. The proprioceptive adjustments to the activation insure that the correct amount of activation is added/subtracted to/from the muscles based upon their present function (i.e., whether the muscle is causing acceleration, deceleration, or stabilization) during a reach and not solely upon the basis of the instantaneous positional error or history thereof.

In the CRL, we have been working on a biologically-inspired control architecture for the McKibben actuated limbs of a humanoid robot. The antagonistically driven joints are actuated using a biological control model observed in the measurement of human muscle electromyograms (EMG) during reaching movements in the vertical plane. The paradigm uses the summation of tonic and phasic EMG signals to activate the human muscles. The humanoid robot’s muscles, actuated by pressure control, are controlled with feedforward pressure patterns analogous to the tonic and phasic activation in the human model. Proprioceptive feedback is utilized in the control architecture to correct for misperceived loading conditions and time variance of the actuators.

The control architecture, initial experimental results, and experiments are discussed in this paper. A result of this control paradigm is the realization of actuation with lower stiffness and therefore safer operation for human-humanoid interaction. It is expected that such a motion of the humanoid will closely resemble human motion and will facilitate a more human-friendly human-robot interaction.

Additionally, we have broadened our research in the use of EMG signals. We have also developed a testbed for the Shadow Robot actuators (artificial muscles) used on ISAC.