Phides is a planar biped robot developed at the Delft University of Technology. Being a 2D running robot, Phides has actuated knees and hips that are connected to a boom construction. The running robot, Phides has achieved a successful flight phase, which is a phase in a running stride wherein the feet are off the ground. Phides is 80 cm (31 inches) tall and has a weight of 13.5 kg (29 pounds).
The knee design of Phides includes a spring in parallel as well as a sprig in series with the actuation. The spring in parallel with the actuation helps to store and release energy and the spring in series with the actuation helps to prevent high impact forces on the actuator. The running robot can reach a speed of 1m/s and has a flight time of 54%.