Jansen's linkage is a planar
leg mechanism
A leg mechanism (walking mechanism) is a mechanical system designed to provide a propulsive force by intermittent frictional contact with the ground. This is in contrast with wheels or continuous tracks which are intended to maintain continuous f ...
designed by the kinetic sculptor
Theo Jansen
Theodorus Gerardus Jozef Jansen (; born 14 March 1948) is a Dutch artist. In 1990, he began building large mechanisms out of PVC that are able to move on their own and, collectively, are titled ''Strandbeest'' (Dutch for 'beach beast'). The ki ...
to generate a smooth walking motion.
Jansen has used his mechanism in a variety of
kinetic sculpture
Kinetic art is art from any medium that contains movement perceivable by the viewer or that depends on motion for its effects. Canvas paintings that extend the viewer's perspective of the artwork and incorporate multidimensional movement are ...
s which are known as (
Dutch for "beach beasts"). Jansen's linkage bears artistic as well as mechanical merit for its simulation of organic walking motion using a simple rotary input. These leg mechanisms have applications in
mobile robotics and in
gait analysis
Gait analysis is the systematic study of animal locomotion, more specifically the study of human motion, using the eye and the brain of observers, augmented by instrumentation for measuring body movements, biomechanics, body mechanics, and the a ...
.
The central '
crank' link moves in circles as it is actuated by a rotary actuator such as an electric motor. All other links and
pin joint
A revolute joint (also called pin joint or hinge joint) is a one- degree-of-freedom kinematic pair used frequently in mechanisms and machines. The joint constrains the motion of two bodies to pure rotation along a common axis. The joint does no ...
s are unactuated and move because of the motion imparted by the crank. Their positions and orientations are uniquely defined by specifying the crank angle and hence the mechanism has only one
degree of freedom
In many scientific fields, the degrees of freedom of a system is the number of parameters of the system that may vary independently. For example, a point in the plane has two degrees of freedom for translation: its two coordinates; a non-infinites ...
(1-DoF). The kinematics and dynamics of the Jansen mechanism have been exhaustively modeled using circle intersection method and bond graphs (Newton–Euler mechanics).
These models can be used to rate the actuator torque and in design of the hardware and controller for such a system.
Illustrations
File:Strandbeest-Walking-Animation.gif, Animation of one leg
File:Strandbeest Leg Proportions.svg, Length of the rods
File:Strandbeest walking with six legs.gif, Animation of six legs
References
External links