Positioner in ASRS
When considering sensing technologies, it is important that each technology maintains an absolute level of repeatability and accuracy to the highest degree; not all methods are the same.
Pallet shuttles and vertical cranes require absolute positioning at all times.
Tray shuttle:
aisle location
row position
Vertical crane:
high
Linear position
Several methods can be used for positioning:
Wheel encoder
Barcode reader
Discrete sensors at fixed positions along the rail
Non-contact laser rangefinder
Practical application of different positioning methods
Wheel encoder
This has always been a popular choice.
Many wheel encoders used are integrated with the SSI encoder output protocol. A challenge with wheel encoders is that they often slip, wear, and change size, or become out of round due to inactivity . All three of these issues can lead to positioning errors, which can cause problems if left unaddressed. Systems with wheel encoders typically require a regular seek process to overcome this limitation.
Barcode reader
While barcode readers are reliable, they also have their weaknesses.
A full strip of barcode tape must be installed along the length of the aisle or row . The distance resolution of the barcode reader becomes the spacing between the barcodes.
Discrete sensors at fixed positions along the rail
They have the same resolution problem as barcode readers.
For example, if you have a groove sensor looking for grooves on a track, the resolution will be the spacing between the grooves. This also requires more complex tracks and makes installers more reliant on the location of track sections.
Non-contact laser rangefinder
Non-contact laser distance sensors have advantages in this application. They typically offer the best accuracy, repeatability, and resolution . Most laser sensors are absolute measurement type. Not all laser sensors are created equal.
Some targets require special reflective surfaces, while others can handle natural targets, such as corrugated steel structures 100 meters away. It is equally important to acknowledge that the laser needs to remain in the target position throughout the entire shuttle's operation.
Features of laser rangefinder sensors
Laser distance sensors are the best choice for ASRS shuttle and crane positioning. The key characteristics you should consider when selecting a sensor are as follows:
Measurement range
Accuracy, repeatability, and resolution
Near and far from the laser
Spot size (importantly, the area under the measuring tray)
Measurement speed
Operating temperature (especially for cold storage)
Industrial Communication Protocol
Visible light laser or easy aiming
HK-Dimetix Non-Contact Positioning Solution for ASRS Systems
Dimetix laser distance sensors are the ideal solution for monitoring the position of ASRS shuttles and cranes to accurately load or unload pallets .
Laser sensors measure the distance to a stationary target at a distance in a straight line, either upwards to the bottom of a vertical lifting platform or downwards from the bottom of the platform to the floor. The Hongke Dimetix D-series laser distance sensors feature long-range measurement capabilities, small spot size, and multiple industrial outputs commonly used on ASRS shuttles.
Dimetix D-Series laser rangefinders offer the best position sensors for achieving this goal because they deliver the following key characteristics:
Long measurement range for large warehouses : Dimetix laser measurement ranges from 0.05 meters to 500 meters.
Capable of measuring the distance to targets under the tray : The Hongke Dimetix laser rangefinder provides a very small spot size, growing to only 30 millimeters at a distance of 100 meters.
High repeatability of absolute position accuracy : The D-series laser sensors offer 3 mm or 1 mm absolute accuracy and 0.3 mm repeatability. Unlike traditional wheel encoders, the code is not lost due to wheel slippage. The Hongke Dimetix laser rangefinder does not require rezeroing.
Low-temperature operation in cold storage : Dimetix offers lasers with a wider temperature range, from -40°C to +60°C.
The output protocols are compatible with typical ASR control systems: DIMEIX D-series laser sensors offer a variety of output protocols as standard equipment.
Multiple interfaces
