Leg mechanism

A leg mechanism (walking mechanism) is an assembly of links and joints (a linkage) intended to simulate the walking motion of humans or animals. Mechanical legs can have one or more actuators, and can perform simple planar or complex motion.

Compared to a wheel, a leg mechanism is potentially better fitted to uneven terrain, as it can step over obstacles.

Another design goal can be, that stride height and length etc. can be controlled by the operator. This can relatively easily be achieved with a hydraulic leg mechanism, but is not practicable with a crank-based leg mechanism.

The optimization has to be done for the whole vehicle – ideally the force/torque variation during a rotation should cancel each other out.

Richard Lovell Edgeworth tried in 1770 to construct a machine he called a "Wooden Horse", but was not successful.

The Plantigrade Machine by Pafnuty Chebyshev was shown at the Exposition Universelle (1878).

Jansen linkage

Klann linkage

Eight-bar leg mechanism

Tokyo Institute of Technology walking chair

2 DOF pantograph leg mechanism

2 DOF leg mechanism of the RPRPR type.

Strandbeest (applied Jansen linkage)

Ghassaei Linkage

Tchebyshevs plantigrade machine

Shown above are only planar mechanisms, but there are also more complex mechanism:

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