(eng): The collocated virtual holonomic constraints for the planar mechanical three-link system are designed to impose the fully exact feedback linearizable constrained dynamics. The linear methods are then applicable both to generate and exponentially track the target walking-like trajectory. More specifically, for every double support phase at the beginning of the step, the mass placed on the torso can be adjusted and the specific constraint designed to ensure the above mentioned full exact feedback linearizability. Furthermore, the design of the impact invariant families of trajectories inside that constrained dynamics is provided as well. To illustrate these results the hybrid cyclic walking-like trajectory is designed and simulated.