# The Role of Feedback in Morphological Computation with Compliant Bodies

**H. Hauser, A. J. Ijspeert, R. M. Füchslin, R. Pfeifer, and W. Maass**

### Abstract:

The generation of robust periodic movements of complex nonlinear robotic
systems is inherently difficult, especially, if parts of the robots are
compliant. It has previously been proposed that complex nonlinear features of
a robot, similarly as in biological organisms, might possibly facilitate its
control. This bold hypothesis, commonly referred to as morphological
computation, has recently received some theoretical support by Hauser et al.
(2012). We show in this article that this theoretical support can be extended
to cover not only the case of fading memory responses to external signals,
but also the essential case of autonomous generation of adaptive periodic
patterns, as, e.g., needed for locomotion. The theory predicts that feedback
into the morphological computing system is necessary and sufficient for such
tasks, for which a fading memory is insufficient. We demonstrate the
viability of this theoretical analysis through computer simulations of
complex nonlinear mass-spring systems that are trained to generate a large
diversity of periodic movements by adapting the weights of a simple linear
feedback device. Hence, the results of this article substantially enlarge the
theoretically tractable application domain of morphological computation in
robotics, and also provide new paradigms for understanding control principles
of biological organisms.

**Reference:** H. Hauser, A. J. Ijspeert, R. M. Füchslin, R. Pfeifer, and
W. Maass.
The role of feedback in morphological computation with compliant bodies.
*Biological Cybernetics*, published 06 Sept 2012.
doi: 10.1007/s00422-012-0516-4.