PDS technology works to detect people or vehicles in the vicinity of an enabled vehicle and alarm the hazard to both parties – CAS systems can take the further action of automatic vehicle intervention if collision is imminent.
Presently the capability of these systems remain shrouded due to perceived complexity, lack of understanding of the technology (or its limitations), operational requirements and the industry’s fledgling state.
In this series Minetec’s Rohan Mathew will discuss PDS and CAS in detail – attempting to demystify the confusion. This first article provides a brief introduction to the technology…
Why | The Human Factor
Mining is a dangerous industry which has successfully improved its risk profile by developing a culture of safety around safe operating practices and corporate responsibility. The industry has been able to dramatically reduce the rate of occupational death and injury in recent years, however the target of a zero harm environment still seems out of reach for the time being.
Increasingly, the industry is finding technological solutions to safety problems – especially those scenarios subject to human error, however the process for technological change is slow and requires significant investment from all parties.
In light of this slow process, legislation is now acting as the driver to force operations, manufacturers and developers into picking the higher hanging fruit at the advantage of saving lives.
Technology capability to prevent death and injury due to vehicle interactions is now emerging rapidly and has yielded some impressive results in field trials. However, implementation of these systems without an informed, strategic and organised approach is likely to limit larger success in site operation.
With careful consideration, implemented technology can even present a return on investment through operational capability and productivity gains.
The relationship between human and machine in safely conducting a vehicle in mining operations cannot entirely be resolved by technology. We will investigate why and the often overlooked considerations through an exploration of the technology further in this series.
Terminology | Nightmare of Names
Terminology around PDS and CAS is a nightmare.
Definitions and acronyms varying across regulatory bodies, OEM’s and mining companies alike. At present there is no standard for interoperability between systems meaning that even fundamental components have different names.
In this series we will define a consistent and simple to understand set of terms for reference:
A Proximity Detection System (PDS) is able to detect assets (vehicles + people) in the vicinity of the enabled vehicle and register the event. The system is solely concerned with detection and alarming and does not take further action. There are three types of detection:
- PVD – Person to Vehicle Detection
- VVD – Vehicle to Vehicle Detection
- IVD – Infrastructure/Plant to Vehicle Detection
A Vehicle Control System (VCS) is able to interact with the machine directly, however does not have an understanding of what is around the vehicle. It is able to read machine health and telemetry information such as vehicle speed and operating gear and (in some vehicles) control the vehicle including idling the engine and applying brakes.
Collision Avoidance = Proximity Detection + Vehicle Control
A Collision Avoidance System (CAS) utilities combination of the above two systems PDS and VCS as a minimum, but may utilise further components. Using these components the system can detect and act to avoid underlying hazards before an incident occurs.
Not a Safety System | Wait …. What?
PDS and CAS systems are not safety systems in their entirety – merely systems designed to help assist the operator to make a judgement. They should never be considered a replacement for due care and operator caution.
They cannot (and will not) prevent incidents in every circumstance and I will further examine these edge case conditions.
Operational Overview | Under the hood
Most radio frequency (RF) systems (Wi-Fi, WASP, Magnetic Wave, RFID, UHF, VHF) work with the following principle:
- Transmitters on the vehicles and personnel send a signal
- The receivers on nearby assets detect the sent signal and sends collected signal information to a Control Unit.
Alternative methods include scanning systems (infra-red, radar, ultrasonic and light based) which work accordingly:
- (Some) Transmitters emit a pulse to illuminate up the surrounding environment.
- Sensors on the vehicle detect changes to surrounding environment between successive and feed sensor information to a Control Unit.
Control Units register the presence, reliability and strength of the detection and uses this information to calculate the distance to the nearby object. If the distance falls within a certain range the system will take action, alarming all users involved of the hazard.
When used with a VCS the system can govern the operation of the vehicle forcing it to idle and stop when an incident appears imminent.
Existing systems can utilise one or more of the supporting technologies in combination to support each other but as complexity increases so too do the number of points of failure, cost and maintainability. I’ll discuss the different technology options in more detail in later articles.
Failure Modes | Who is General Failure?
There are two main ways in which a system can fail:
- Failure to detect (False negatives) a proximity detection event – this can occur predominantly because the system is unable to hear a transmission from a nearby device, unable to distinguish an asset correctly or miscalculates the range. Identification of this mode of failure can be difficult as it requires incident replay, repeatable circumstances and data logging and may manifest itself only under specific circumstances.
- Detecting wrongly (False positives) – this can occur when the system in unable to distinguish an asset correctly or miscalculates the range. Identification can be obvious but can have an unidentified prolonged impact on system deployment affecting the end users: users lose trust the system and are “deafened / blinded” to system alarms.
PDS and CAS systems operate on a Fail-To-Safe principle. In the event of failure of one or more components, the system alarms and prevents operation of the entire vehicle until the fault is rectified.