  Tensegrity structures are lightweight, can undergo large deformations, and
have outstanding robustness capabilities. These unique properties inspired
roboticists to investigate their use. However, the morphological design,
control, assembly, and actuation of tensegrity robots are still difficult
tasks. Moreover, the stiffness of tensegrity robots is still an underestimated
design parameter. In this article, we propose to use easy to assemble, actuated
tensegrity modules and body-brain co-evolution to design soft tensegrity
modular robots. Moreover, we prove the importance of tensegrity robots
stiffness showing how the evolution suggests a different morphology, control,
and locomotion strategy according to the modules stiffness.
