Historically, research at the Delft Biorobotics Laboratory focused on the development of walking bipeds, based on the principle of passive dynamic walking. All the walking and running bipedal prototypes and models resulting from that research are given below.
Phides (2012) 2D running robot with actuated hips and knees attached to a boom construction. The knee joints have a spring in parallel with the actuator for energy storage and release and have a spring in series with the actuator to reduce damaging impact forces on the actuator. Phides can run at speeds up to 1m/s and with a flight time of 54%.