Increasingly competitive industrial environments are challenging warehouse and distribution centre managers to reduce costs and increase productivity, while raising quality and safety standards. While many facilities in our market cannot justify a full conversion to completely automated load handling equipment, it would be well worth investigating incorporation of reverse sensing technologies on existing forklifts to help maximise their efficiency.
Adding active systems, such as reverse sensing solutions, to manned forklifts can reduce the risk of a forklift collision with objects such as personnel, products, machinery or building structures. Proper application and use of reverse sensing technology in combination with the driver will reduce collisions, minimising downtime and expenses associated with an accident.
Why use automated technologies on manned vehicles?
Statistics in the United States estimate that there are around 100 000 forklift accidents per year, resulting in over 94 000 injuries. Almost 80% of forklift accidents involve a pedestrian. Additionally, if the forklift causes damage to inventory, the actual replacement costs of the goods can eat into profitability. For example, if the value of a case of goods is R1000, the cost to replace it must come from the margin on future sales. If a company makes a 10% margin on that case of goods, then they will have to sell 10 additional cases to make up for the single damaged case, and this does not include the possible damage to building structures.
Collisions occur for a variety of reasons including;
* Even though forklift drivers are trained to always look in the direction of travel, and to travel in reverse if their load blocks their view, they might not do so consistently.
* Driver controls are frequently located on the fork-side of the forklift and seats are oriented in the same direction. It can be ergonomically and physically difficult for the driver to twist in their seat when reversing.
* There may be one or more blind spots, due to loads or enclosed forklift cabins.
* More and more warehouses are implementing high-density storage with narrower aisles, compressing the turning radii.
All of these factors can contribute to collisions with objects such as personnel, products or building structures.
Considerations when evaluating reverse sensing technology options
To mitigate these risks, many companies are investigating the installation of some type of object detection system, particularly on the back (non-fork) side of the manned forklift. These devices are intended to compensate for driver error and eliminate the costs associated with accidents.
Two primary types of reverse sensing technologies are currently available: passive and active.
Passive systems
Passive systems include visual warning systems, for example; flashing beacon lights or laser lights pointed at the floor a set distance away from the forklift, intended to be a visual cue for pedestrians that a forklift is approaching, alerting them to act appropriately.
Another example is the reverse buzzer which is integrated into most forklifts. While this is commonly used and easy to integrate, it is always on when the forklift is being driven in reverse. This provides feedback to nearby personnel to minimise potential collisions.
However, neither of these systems interact with surrounds or people, consequently they do not help the forklift to avoid static objects and collisions will still occur.
Active systems
Wearable warning systems have been introduced into certain industries. These make use of a proximity antenna, but there are limitations since it requires a transponder unit to be worn by all personnel. In addition, an in-cab unit must be installed within each vehicle to read the transponders. If a person does not wear their transponder and enters the detection zone, an alarm will not be triggered. Such a system still does not allow for collision avoidance with static objects such as racks and pallets.
Alternatively, active sensing devices, such as a laser scanner, continuously monitor a specific area behind the forklift. This technology projects a beam of infrared light away from the forklift and if the light encounters a surface, the surface reflects some of it back to a sensor in the scanner. Internal converters and decoders interpret the information using intelligent algorithms to evaluate the field it is monitoring. These calculations determine the location of the obstacle relative to the position of the forklift. Completely configurable, the projected eye-safe, invisible 2D laser plane is capable of monitoring a radial zone within a range of 8 metres, in a 270 degree field of view. This can be used to monitor the areas where the drivers view is obstructed.
Zone programming can be implemented using a simple graphical interface within the scanners configuration software. One the teach-in process has been completed, the scanner returns to an active monitoring mode. When the system detects an obstacle in the configured field, it triggers a warning to alert the driver to stop the forklift. Systems can provide two warning levels – approaching a collision vs collision is imminent – using a flashing light, audible buzzer, or a combination of these. These laser scanners could also potentially be wired into the forklift’s stop circuit, triggering an automatic ‘slow speed’ or stop state if an obstacle is detected.
The laser scanners generally operate in a variety of ambient conditions, not being negatively affected by lighting conditions, dust, object colour and noise. Some units can be used in applications where the temperature goes down to -10°C, in cold storage for example.
This reverse sensing system can be incorporated into the forklift’s reverse gear, eliminating false alarms due to closely-following vehicles or people crossing directly behind while the forklift is moving away. The reverse sensing system is small enough to fit virtually anywhere on the forklift and has a power consumption of only 5 W, meaning that it will not significantly reduce the forklift’s performance. It could also be powered from a small separate power supply in the case of forklifts using an internal combustion engine.
Summary
When evaluating obstacle detection systems, always consider the following:
* Method of detection.
* Obstacles to be detected.
* Ease of driver use.
* Accuracy in low light conditions.
* Reliability in dirty environments.
* Durability.
* Ease of installation and setup.
* Power requirements.
For more information contact Stephen Eltze, SICK Automation SA, +27 (0)11 472 3733, stephen.eltze@sickautomation.co.za, www.sickautomation.co.za
| Tel: | +27 10 060 0550 |
| Fax: | +27 86 598 7915 |
| Email: | info@sickautomation.co.za |
| www: | www.sick.com/za/en/ |
| Articles: | More information and articles about SICK Automation Southern Africa |
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