Holonomic Mobility



The CYCOGS® company wishes to inform our web site visitors with some useful AI Robotic information.  Please note,  the CYCOGS® company owns and or controls the copyright of all material in this website.  The content of the “ Education ” portion of this web site is still under the CYCOGS® company registered copyright protection.

This is the case for Holonomic Mobility.

Mobile Robotics which operate on a floor or ground usually employ wheels.  Holonomicity 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. 

Degrees of Freedom

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  redundantHolonomic Redundancy  usually has more  DoF  controllable motions than  DoF  available in its task or work space. 

Red Train

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. 

Ackermann Steering

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.

Holonomic SteeringHolonomic Drive Path

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. 

Holonomic Frisby

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.

Holonomic MotionHolonomic Elevator

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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