The AGV detects the magnetic guiding strip laid on the ground by the magnetic induction navigation sensor, and then obtains the relative one-dimensional coordinate signal of the magnetic induction sensor and the magnetic guiding belt, and transmits the coordinate signal to the AGV controller, and the AGV controller controls the AGV wheel rudder according to the signal state. Magnetic guide tape.
The purpose of the magnetic induction sensor is to guide the AGV along the tape. The magnetic navigation AGV also needs a landmark sensor or RFID device to identify the current site ID of the AGV, and then obtain the location information of the AGV on the current route or perform other functions.
AGV tape navigation schematic
In the historical development of AGV, AGV navigation mode is mainly based on electromagnetic navigation and tape navigation. Due to the complicated construction and high cost of electromagnetic navigation, tape navigation has gradually replaced electromagnetic navigation, but electromagnetic navigation is in harsh environment (high temperature, acid and alkali environment). Under the higher adaptability, electromagnetic navigation is still present in specific situations.
Compared with electromagnetic navigation, tape navigation has the advantages of cost advantage, simple construction, stable and reliable, anti-interference to photoelectricity, etc. Currently, tape navigation applications are common in industrial applications. Especially in automobile assembly plants, engine assembly plants, etc.
Let’s compare the advantages and disadvantages of electromagnetic navigation and tape navigation:
|
Electromagnetic navigation |
Tape navigation |
|
Need electromagnetic signal generation equipment (high cost, maintenance required) |
Permanent magnet tape (low cost, no maintenance required) |
|
Ground slotted embedded electromagnetic signal cable (complex construction, long construction period) |
Tape on the ground (simple construction, short construction period) |
|
Adding or changing AGV lines later requires re-grooving |
To add or change an AGV line later, you only need to paste a new tape. |
|
Suitable for high temperature environment, acid and alkali environment |
Not suitable for high temperature environment, acid and alkali environment |
|
Embedded electromagnetic signal cable is not easily damaged |
Tape is subject to wear or damage |
How does the tape navigation sensor work?
The AGV magnetic navigation sensor has a stepped analog voltage output type. The magnetic navigation sensor consists of a plurality of magnetic sensor elements “”saturable coil””, a decoder and a D/A conversion. The step analog voltage is proportional to the relative position between the tapes. The magnetic navigation sensor has a selection function (straight, right or left) on the branch section. The step voltage is changed according to the command signal by inputting the branch path selection signal. The gate signals of the controllable area are simultaneously output.
How to choose the tape navigation sensor at the branch intersection?
Straight line mode
Normally, this mode is always selected.
The magnetic navigation sensor outputs a specific step analog quantity (typical voltage output) when the above-described route travel detection is performed. Each voltage step may vary under air gap fluctuations as described below.
02
Right branch selection mode
This mode should be selected in the following lines.
The magnetic navigation sensor outputs a specific step analog quantity (typical voltage output) when the above-described route travel detection is performed. Each voltage step may vary as described below under air gap fluctuations
03
Left branch selection mode
This mode should be selected in the following lines
The magnetic navigation sensor outputs a specific step analog quantity (typical voltage output) when the above-described route travel detection is performed. Each voltage step may vary under air gap fluctuations as described below.
The tape navigation sensor is kept at a distance from the device that generates the magnetic field, such as the motor. If the magnetic navigation sensor is mounted on a ferrous metal material, keep the navigation sensor at the following distance from the iron material.
There are currently two types of tapes available on the market, with widths of 25mm and 50mm. A unipolar tape must be used, one of which is a magnetic N pole and the other side is S-shaped. You cannot select the tape polarity to alternate mode.
When using a 25mm wide tape, the sensor can be checked to a height of 50mm, and when using a 50mm wide tape, the detection height can be up to 60mm. At higher detection heights, the magnetic field of the tape is weaker and the noise of the sensor is smaller.
We mainly introduced the working principle of magnetic navigation sensor. In the AGV of magnetic navigation technology, the main purpose of the magnetic navigation sensor is to guide the AGV to walk and ensure that the AGV always advances/reverses along the tape.
In industrial production, the AGV needs to walk along a tape to a station to perform the corresponding action, thus requiring a positioning function. How does AGV implement positioning?
There are several ways as follows.
1. An additional magnetic inspection sensor is added. A landmark (tape, the polarity of the tape is opposite to the guiding tape) is deployed at a specified position of the AGV walking line. The sensor is used to check the landmark to realize the positioning function. The sensor is called a landmark sensor.
2. An additional RFID sensor is added. On the same principle, an RFID tag is deployed at a specified position on the line on which the AGV walks. The purpose is that the AGV acquires the tag information of the current location through the RFID sensor, thereby implementing the AGV positioning function.
- Remove dust, water or oil from the floor.
Use tape or self-adhesive tape to lay the tape on the floor.
Distinguish between the N pole and the S pole on the upper surface of the tape。
Precautions
The tape can be mounted on a ferrous floor, but it cannot be embedded under an iron floor because the magnetic flux caused by the iron floor is greatly reduced.
A magnet near the tape may cause an order change in the distribution of the magnetic flux. The proximity of a strong magnet (above about 1KG) to the tape may change the flux distribution of the conduction band.
The distance between the tape and the tape is 500mm or more.
The adhesion of iron powder (iron cutting, etc.) to the conductive tape may result in a decrease in magnetic flux density. Regularly remove the binder iron powder (iron cut, etc.) from the guide tape.
When the tape is attached to the tape, the gap between the two tapes cannot exceed 2 mm.
Chemicals and solvents (acetone, thinner, etc.) are prohibited as it may change the shape and characteristics of the tape.
Non-ferrous metals (aluminum, stainless steel 304, etc.) can cover the magnetic tape to protect it. However, the ferrous material (iron, stainless steel 303, etc.) cannot cover the tape because the ferrous material covers the tape, causing the magnetic flux of the tape to be shielded.