Professor Theo Jansen has developed many walking machines . Here is one example, presented schematically. This walking mechanism needs very little energy because the "hip" stays at the same level. Usually at least two such mechanisms cooperate, running out of phase. Move the slider slowly to make the mechanism walk. You can make a second mechanism visible by clicking the "2" button for "machines". Choose "2" for "display" to make the machine walk by.
Professor Theo Jansen's machines usually are built from electrical conduit pipes, and they run on temporarily stored wind energy.
However, his walking mechanism can be and has been used for motor-driven gadgets as well.
Snapshot 1: the machine is stationary, and a moving floor is simulated by a series of moving dots
Snapshot 2: the machine walks past
Snapshot 3: here all measurements are given (in arbitrary units) and the floor is divided into these arbitrary units; the slider does not work in this display
 Theo Jansen. "Strandbeest." (May 31, 2016) http://www.strandbeest.com/.