Holonomic Mobility Information
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This is the case for Holonomic Mobility.
which operate on a floor or ground usually employ wheels.
refers to a robot’s sum of its
Degrees of Freedom (DoF)
and the relationship to the controllable Degrees of Freedom.
This term is usually applied to robotic arms.
A robot that controls all of its work space Degrees of Freedom (DoF) is said to be Holonomic.
A robot or robotic part with fewer controllable DoF than total workspace DoF
is said to be non-holonomic
and a robot with more controllable DoF than total workspace DoF is said to be redundant
usually has more DoF
controllable motions than DoF available in its task or work space.
For example, a train can only move on the X axis work space (the train tracks), 1-DoF,
and can control its position on that one axis, thus it is holonomic.
Most automobiles can be orientated and move to any position in 2-Dimensional (2D) work space.
The auto requires 3-DoF to describe its position (X, Y and gamma),
but at any point, it can move only along the vehicles centerline and turn with a steering angle input.
(ignoring skidding and “drifting”) Thus, it has only two control DoF and three positional DoF;
so, it is non-holonomic.
This illustration shows a holonomic three wheeled vehicle / robot.
The vehicle or robot is capable of moving in any X – Y – gamma direction or orientation.
The holonomic ability allows for synchronous movements (top of illustration) and fully holonomic movements (bottom).
Note how the F
= Front orientation changes,
as well as each wheel utilizing its own unique steering angle for a pivot point near the front of the vehicle or robot.
With holonomic mobility, precise positioning during navigation movements and expanded movements are possible.
Now, some holonomic movements are unique.
One such unique holonomic movement is the rotational translating movement, called the
“Frisbee Glide” effect.
This graphic illustrates the “Frisbee Glide
” rotational translating movement.
The robot moves forward in the X axis direction, while rotating on its Z axis.
Other movement types are possible, using software emulation to move in a Differential mode,
a Synchronous move or combinations including other mobility modes.
The ability to simulate a crab, skid or slew movements plus this Holonomic Mobility has the ability to
simulate of other drive types such as the Ackermann,
Differential and Synchronous drives.
This Holonomic Mobility ability allows for precise moves for operating in crowded elevators or hallways.
Having holonomic movement abilities eliminates the need for a rotating chassis section with the associated slip ring and
cable tether design limitations found in
Synchronous Mobility Systems, the whole chassis can be rotated by the wheel assemblies.
But more software code is involved to take advantage of its increased mobility.
The benefits for a holonomic vehicle or robot include economy in movements.
Spend a few milliseconds of computer time on some complex trajectory calculations,
and save or conserve energy in making that tricky maneuver.
No wasted motion
Compare this to the non-holonomic robot.
Such as performing a tricky move, if even possible for its mobility type,
could take several minutes of crude maneuvering to position the robot.
For environments requiring precise movements, use a holonomic drive.
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