A key issue in developing walking machines is to ensure stability of the machine during gait. The complexity of this problem increases with a decreasing number of legs. Where hexapods can guarantee static stability for all the time, in quadrupeds this is limited to special gait patterns and in bipeds the dynamical stability is imminent, especially if the intention is to build humanoid robots. In this paper we introduce a new artificial spine driven by pneumatic actuators for a biped locomotion platform. It is described how the hardware is designed and how the components have been modeled mathematically to be able to test and develop different control strategies for body stabilization tasks.