How does AGV navigation work?

How does AGV navigation work?

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AGV Navigation Methods

How do AGVs actually know where they are going? The robots use unmanned navigation technology to guide them. The method of navigation used by an AGV determines how the device operates.

Currently, there are 7 main navigation methods to guide AGVs: laser navigation, magnetic nail navigation, electromagnetic navigation, magnetic tape navigation, contour navigation, ranging navigation and multi-type navigation. Let’s take a look at their differences, advantages and disadvantages.

Laser Navigation

First, and the most widely used guidance system, is laser navigation.

Laser navigation technology applies the principle of triangulation. Reflector plates (like mirrors) are installed at different angles around the driving path of the AGV. The AGV projects laser beams onto the reflector plates receives the laser beams reflected back and uses the angle between the transmitting and receiving directions to navigate via continuous triangular geometry calculation. 

Laser Navigation Advantages:

  • Precision (precision level of 10mm)
  • Higher movement speed
  • No additional positional equipment required
  • Path of movement can be flexibly changed to fit a variety of environments

Laser Navigation Disadvantages:

  • Requires visibility and no sunlight on the path (inoperable in direct sunlight)
  • Suitable only for unobstructed environments
  • High cost for AGV equipment and reflector plates
Magnetic Tape Navigation

Another popular method is magnetic tape navigation. Magnetic tape navigation is a relatively mature technology, in use on many site floors.

The way it works is that AGVs receive magnetic induction signals from the tape laid on the target path. Then, the magnetic navigation sensors on the equipment enables the vehicle to navigate.

Magnetic Tape Advantages:

  • Simple installation with low technical requirements
  • No interference caused by light or sound
  • Easy to modify or expand paths, low cost of modification, allows for short modification cycles
  • AGV path of operation is readily visible

Magnetic Tape Disadvantages:

  • Tape is exposed to the environment and therefore vulnerable to mechanical damage and contamination
  • To prevent the AGV from rolling over the tape when turning, the tape cannot be laid continuously, affecting navigation stability
  • Attracts nearby metallic substances, which may cause AGV equipment malfunction
  • Requires additional sensors for site location functions
Magnetic Nail Navigation

Magnetic nails works like magnetic tape, except they are installed beneath the floor. The control module for magnetic peg navigation is even the same as that used for magnetic tape navigation. The difference is that magnetic tape navigation uses intermittent sensing while magnetic nail navigation uses continuous sensing. For this reason, the distance between nails must not be too large. Since AGVs continuously measure the distance between two nails, they require an encoder to measure the distance traveled.

Magnetic Nail Navigation Advantages:

  • Low cost, mature technology
  • Magnetic nails are buried underground; no other navigation aids are needed above ground
  • Magnetic nails are resistant to abrasion, acid, alkali and oil, etc., and are suitable for both indoor and outdoor use

Magnetic Nail Disadvantages:

  • Technical requirements : There can be no other magnetic material near the magnetic nail navigation route; the path cannot tolerate interference from any demagnetizing or anti-magnetic material
  • Some floor damage during construction, i.e., holes will be cut in the ground and then backfilled, which requires precise construction techniques
  • Lack of flexibility in making modifications: Modification will require work similar to installation, thus incurring a high construction cost and construction time
Electromagnetic Navigation

Electromagnetic navigation is a more traditional navigation method. Currently, it is mainly used in certain kinds of AGV working environments, such as narrow passages, high-temperature environments, and environments that require a high level of path straightness. The path consists of a metal wire buried along the AGV driving path that sends out an electromagnetic guidance frequency through the frequency generator. A position sensor installed on the AGV receives and renders the electromagnetic guidance frequency, which the AGV uses to navigate.

Electromagnetic Navigation Advantages:

  • Low cost, mature technology
  • Enables high-precision path planning
  • Path is well concealed and therefore resistant to interference, abrasion, acid and alkali, oil and other disturbances
  • Suitable for both indoor and outdoor use

Electromagnetic Navigation Disadvantages:

  • Requires additional equipment to generate electromagnetic signals
  • Lack of flexibility in modifying navigation path: Path modification requires work similar to installation, meaning additional costs and construction time
  • Some floor damage during construction, i.e. slotting and backfilling
Ranging Navigation

Ranging navigation technology primarily uses a two-position laser scanner to scan and measure its surroundings, obtain measurement data and then integrate the data with a navigation algorithm to achieve AGV navigation.

The navigation sensor typically uses a safety laser scanner with safety features, simultaneously achieving both safety functions and navigation measurement functions. AGVs with range-finding and navigation technology can enter the interior of containers for automatic pickup and delivery.

Contour Navigation

Contour navigation is the most advanced navigation technology available for AGVs. This guidance method uses a 2D laser scanner to measure and learn the field environment and map the navigation environment, and then performs measurement learning to correct the map and thus achieve contour navigation.

Contour navigation uses free range navigation of the natural environment (walls, columns and other fixed objects) to update the position based on environmental measurements.

Contour Navigation Advantages:

  • No need for reflectors or other artificial markers
  • Decreased installation cost
  • Decreased maintenance work
  • Laser navigation alternative
Hybrid Navigation

Hybrid navigation is an amalgamation of multiple navigation methods that have been created to meet the needs of a changing field environment. When one type of navigation is temporarily unable to perform adequately due to changes in the site environment, the AGV switches to another type of navigation to allow continuous operation.

ASAP Rental AGV Solutions

AGV equipment is a deeply customized product. Choosing the AGV equipment and technology that meets the needs of the enterprise itself is a professional choice faced by each customer.

The parent company of ASAP Rentals and the European AGV equipment manufacturer Rocla have been collaborating in the international market for more than 20 years. In 2017, they began working together to expand the automated material handling equipment market in China

With the rich experience of working with Rocla on several AGV projects and ASAP Rentals’ unique one-stop fleet solution, ASAP Rentals is confident that we can provide full support to Chinese enterprises to upgrade their intelligent manufacturing.

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