Quad Steer vs. Single Steer AGVs

In an effort to provide additional options for customers Transbotics developed quad steer capability as an option for their Automatic Guided Vehicles.  Through many years of research and development Transbotics engineered a quad steer solution that is more flexible and efficient than traditional single steer mode.


The big advantage to using Quad mode, of course, is that it is flexible and able to perform all of the steering modes. Because of this ability, it is usually used in areas where there is not much room for mobility.  It can change direction at any time and/or steering mode, as well. 

Another advantage of the Quad mode is its ability to maintain the highest level of traction in wet/slippery environments.  The wheels work independently of each other allowing them to compensate for one another should slippage occur.  This gives the vehicle maximum error recovery capability and accuracy throughout the layout.

The only disadvantage, and we really wouldn’t call it a disadvantage, is that it costs a little bit more than the basic steer drive vehicle.  Of course, this makes sense because it has more features and pliability, so to say.

Example of Quad Steer Drive

Quad Directional Drive2


A single Steer Drive vehicle is basically a tricycle configuration, and much like a tricycle, it must do overturns in radii.  This, too, can cut cost, and, if you don’t need to travel in ‘Diff’ mode and you have plenty of room to navigate, it would make more sense than Quad or Diff Drive configurations.  However, it is not advantageous if you need to make tight turns and/or have tight areas where a vehicle can only gain access via Diff Drive mode.

Overall, you will find that, while the Quad vehicle may cost a bit more, it is far more flexible and capable than any of the other steer/drive configurations.  It is recommended to go with a Quad vehicle if the layout is tight, aisles are narrow, and simply for the possibility of expanding the system and maintaining complete functionality of the vehicle, no matter what type of environment is involved in the expansion.

Example of Single Steer Drive

Single Steer Drive

Example of Directional Movement

Directional Movement

The Quad Vehicle has much more maneuverability than the single steer drive vehicle. Single Steer Drive has the ability to move the vehicle either right or left while moving forward or backward.  The Quad Vehicle has the ability to move in any direction, giving you more flexibility in your facility by saving aisle room, time, and money.  Please note that the Dual Steer Drive configuration does not have all of the features of a Quad Vehicle.

Example of Single Steer Turn

Single Steer Turn

Single Steer Vehicles must overturn to maintain the guide path. This generally takes more room and time for the vehicle to travel. The Single Steer Vehicle must also compensate for the approach into the next station.

Example of Quad Steer Turn

Quad Steer Turn

Quad Steer Vehicle follows the curve by using both of the drive wheels to turn in opposite directions. This allows the vehicle to turn tighter curves while maintaining the reference point over the segment.

Notice that the drive wheels do not always have the same angle as the vehicle moves through the curves.  This allows the vehicle to move through narrow isles and doorways without repositioning for an overturn.

Example of Quad Crab Move

Quad Crab Move

On a ‘Crabwise’ segment, the vehicle maintains the angle that it had at the start of the segment and maintains the same orientation throughout the curve(s).

The drive wheels always appear to have the same angle as the vehicle moves through the curves.

AGV Guide Path

Below is an AGV guide path for a Quad Steer Vehicle and a Single Steer Vehicle.  The Quad AGV uses less room and fewer movements to complete a pickup and/or drop-off than that of the Single Steer AGV.

Quad vs Single Steer

AGV Movement Diagram

Below is an AGV movement path for a Quad Steer Vehicle and a Single Steer Vehicle.  Both vehicles are exactly the same size and the pickup/drop-off points are same size.  Single Steer drive takes more room to maneuver in order to get into the pickup/drop-off area.

Quad vs Single Steer2

Segment/Movement 1

Segment 1 illustrates the first point in which both AGV’s begin making the turn into the pickup/drop-off location.  The Single Steer Vehicle has to approach the point much like that of an automobile that is going to parallel park.


Segment/Movement 2

Single Steer Vehicle must pass the pickup/drop-off point so that it can back into the desired position.  The Quad Vehicle is able to approach the pickup/drop-off point from forward movements and moves into position quickly and accurately.


Segment/Movement 3

The Quad Steer Vehicle is now loading/dropping-off while the Single Steer Vehicle is still backing into position. 


Segment/Movement 4

The Quad Steer Vehicle is now leaving the pickup/drop-off area and the Single Steer Vehicle is in the loading/drop-off position.  Again, the Quad Steer Vehicle is able to pull away without backing up or adjusting for an overturn.


Segment/Movement 5

The Single Steer Vehicle has now backed up in order to position itself to compensate for the overturn and the obstruction in the front of the vehicle.  The Quad Steer vehicle is already on its way to its next position and/or task.


Segment/Movement 6

The Single Steer is now leaving the pickup/drop-off position and moving onto its next position and/or task while the Quad Steer Vehicle has left the area.

Segment 6

Segment/Movement 7

Quad Steer Vehicle completed the process in two fewer steps than that of the Single Steer Vehicle.  The Quad Steer Vehicle has the ability to move in any direction so that the facility space is maximized with production/product.  The Quad Steer AGV will also minimize the travel time so that throughput remains high and constant.


To learn more about AGVs or to find the right AGV solution for your business, consult with an AGV Specialist today.


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