Strata Takes a Look at the Technologies that Drive Proximity Detection

No matter how advanced mining machinery becomes, reducing the risk of unintentional interaction between miner and machine continues to be a vital component of safety. Each year, the industry reports injuries and even deaths due to unsafe contact with mobile equipment.

In response, a range of proximity detection technologies and collision avoidance solutions have emerged on the market over the years, all in an effort to reduce – and hopefully eliminate – these hazards.

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But how does a mine decide which one will be most suitable for its needs? Some questions to ask include:
– Do you want a system to simply assist machine operators to see their surroundings before and during operation?
– Do you want a system that warns operators with alarms to alert them of hidden obstacles and potential dangers?
– Or do you want a fully interactive system that detects possible dangers, sends warnings to personnel involved and can take action to prevent a collision?

Different mining operations and working environments require different levels of detection and safety, and in this blog, we look at the different technologies available now, reviewing the capabilities and highlighting a few pros and cons of each.

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Camera systems with display screen are perhaps the simplest available detection system. Placing cameras on the front and rear of a machine, as well as in any blind spots, provide a view of the surrounding areas and the ability to monitor when personnel and other vehicles are approaching or in a precarious location.

Cameras are easy to install and are relatively inexpensive; however, they are passive systems with no active detection or warnings, so to be effective, they rely on the machine operator to monitor the screen.

Radar systems work by installing a sensor at the front and rear (and sides as applicable) of machinery to send out pulse waves and detect reflections or shifts in frequency. Such an indicator represents the presence of an object or pedestrian, and an alarm is triggered for the machine’s operator. Any object will be detected, and no receiver/tag is required.

Radar systems provide a robust, reliable detection capability for object position and distance identification. With sensors installed on both the front and back, the direction of travel is irrelevant.

Since radar is subject to alarm triggers when any object enters its field – regardless of what that object is – benign objects could cause false detects and nuisance alarms, resulting in loss of efficiency and wasted caution for the operator. Cameras and display screens will typically become necessary at that point.

This lack of object discernment also makes radar less suitable for autonomous braking capabilities. Radar is alarm-only to the operator and does not warn personnel on foot.

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Radio Frequency Identification (RFID) systems for proximity detection in mining and construction, work by using an “activator” installed on machinery and small battery-powered “tags” worn on a miner’s person. The activator sends out RF pulses to create a “read field” around the machine and any tag within range is, per the name, activated. When this happens, the tag sends out a location signal to alert of its presence and trigger a warning alarm to the machine operator.

RFID is a highly versatile, readily available technology that has the benefit of being cost-efficient as well. The systems are easy to install and work with any number of tags.

It can, however, be susceptible to interference, and the radio waves can be easily blocked. Since batteries are required to operate individual tags, a false sense of safety could result if the battery power isn’t checked regularly.

RFID can be an effective warning solution for machine operators, but typically pedestrians are not alerted.

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Global Positioning Systems (GPS)
Global Positioning Systems are one of the best-known methods of position tracking for surface operations and have become very popular across the industry. Similar to consumer products, GPS uses satellite signals to triangulate a position based on latitude and longitude. For collision avoidance, the system then shares location data with other vehicles by using radio frequencies. Two-way communication between vehicles allows operators to monitor the locations and movements of others so collisions can be avoided.

The primary benefit of using GPS to track workers and machines is accuracy; the technology is highly accurate and can be used to cover a very wide area. With the use of an on-dash display screen, it provides a 360° view of the machinery’s surroundings, including all other vehicles within a specified range.

A potential downside to GPS is that it only works with an unobstructed view of the sky. It can be affected by overhangs or highwalls and can also experience difficulties in canyons. GPS is also an alarm-only system, but can be programmed to alert all parties involved, including pedestrians, with the incorporation of RF.

A critical disadvantage with GPS is that it is not ideal for close-range proximity detection. Therefore, it is generally ineffective for start-ups, reverse operation and covering blind spots.

Ultra-Wide Band (UWB)
Ultra-Wide Band is a newer technology that uses a wide spectrum of radio frequencies to create two-way communication between system transceivers. Transceivers are installed on machinery and vehicles and are carried by personnel. The time-of-flight (ToF) of the RF signals is used to obtain the distance between and the position of the objects.

UWB offers the benefit of highly precise positioning, which allows operations to identify different levels of proximity zones such as “warning” or “hazard” zones.
Two-way communication between transceivers ensures that all parties are alerted if an imminent collision is detected.

UWB does experience multipath reflection, which in layman’s terms means the signals bounce or reflect off surrounding surfaces. Multipath benefits the system by ensuring that the signals are registered; however, it can alter the ToF calculations which could lead to erroneous position estimates of the objects.

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Electromagnetic (EM)
Electromagnetic systems work with field generators and personnel-worn receivers. The generators are installed onto equipment and create electromagnetic zones that surround the unit. Personnel wear Personal Alarm Devices (PADs), which detect these zones and trigger alarms of warning to all parties when the zones are breached. As with UWB, electromagnetic enables operations to identify different levels of safety zones such as “warning” and “hazard” zones.

When the warning zone is breached, parties receive audible and visual alarms, and if elected, the machine will automatically slow its speed. If the hazard zone is breached, the system will alarm and can be programmed to completely stop to avoid a collision. This interlocking capability ensures the highest level of personnel safety while working around operating machinery.

EM is unaffected by its environment and the atmosphere and can easily penetrate coal, rock, construction barriers, stoppings and ventilation curtains.
The technology sees what people can’t and warning alarms will be triggered by personnel hidden from view and around corners.

Electromagnetic systems are proven technology for “near field” hazards – meaning the fields are highly stable and the system works at extremely close range. It warns both equipment operators and personnel-on-foot simultaneously and can be interlocked into machinery controls to reliably slow or stop the machinery.

Every mining machinery working environment has individual levels of safety requirements, which helps determine a company’s choice in proximity detection technology. All technologies discussed here have been used in active working environments. Radar and GPS have been strongly adopted into surface applications, as well as the use of cameras. Electromagnetic systems, while newer to the surface mining industry, can be used in conjunction with far-field technologies. It is ideal for close-range blind spot coverage for vehicles starting up, reversing and traveling at slow speeds.

Given the nature of the underground working environment, with factors such as low visibility, confined work areas, physical barriers and the heavy presence of mobile machinery, electromagnetic proximity detection has over the years been proven to be the most effective technology for these environments. The risks associated with working alongside mobile machinery underground are well known, and the requirements for the proximity detection systems have been defined.

The core technology of Strata’s HazardAvert® system is refined for these applications and has demonstrated high accuracy in close quarters. It has the capacity to function with hundreds of vehicles and pedestrians in close proximity without latency or delay.

Strata has over 1500 HazardAvert® systems currently active in both surface and underground mining environments, and in underground tunnelling operations around the world.

To learn more about Strata Proximity Detection go to the CONTACT tab or WEBSITE link below to reach Strata Worldwide directly.

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Strata Worldwide , established in 1992, has spent decades becoming a leading global provider of many products, services and technologies that are vital to bringing the highest level of safety to mining operations across the globe.

From its global headquarters in Atlanta, Georgia, USA, Strata has built upon a diverse product portfolio that includes the leading proximity detection and collision avoidance technology, HazardAvert®. HazardAvert, designed to increase miners’ safety while working around heavy machinery, promotes safer working practices through increased safety awareness and modified worker behavior. It works to prevented accidents and collisions which in-turn improves overall productivity and efficiency.