How the phone in your pocket is helping inspire the next generation of humanitarian demining equipment

Quadrupolar Resonance (QR) has long been recognised as one of the most promising methods for the detection of explosives [1]. Its potential stems from the fact that, unlike most other methods, QR can discriminate between different chemical compounds or even different structures of the same compound. Nitrogen (14N) is found in most commercial and improvised explosives which makes 14N QR a perfect method for use in detection devices.

Unfortunately, today’s commercially available equipment is composed of various bulky – and expensive – components, most notable being the QR spectrometer and the power amplifier. The spectrometers were in the recent years successfully made smaller and a lot cheaper by using FPGA chips, leaving the RF power amplifier as the key component which needs improvements to allow for building a truly portable system. The main drawback of the current, class AB power amplifiers is their power efficiency, which is in practice limited to below 50%. As a consequence, large heavy heatsinks must be used to provide for adequate heat dissipation while high power consumption makes the device unsuitable for battery-powered use.Quadrupolar Resonance (QR) has been long time ago identified as one of the most promising methods for the detection of explosives [1]. Its potential stems from the fact that, unlike most other methods, QR can discriminate between different chemical compounds or even different structures of the same compound. Nitrogen (14N) is found in most commercial and improvised explosives which makes 14N QR a perfect method for use in detection devices.

In the recent decades, class D amplifier technology has seen significant progress due to its widespread use in audio signal amplification. Compared to classical (A, B, or AB) topologies, class D amplifiers feature 100% theoretical power efficiency and can attain over 90% in practice. It is therefore no surprise to find class D chips from major semiconductor companies in portable music players and mobile phones. Unfortunately, the requirements for audio amplification differ significantly from the ones for NQR pulse amplification. Besides the different frequency range which is 0.02 – 20 kHz for audio and 0.1 – 5.5 MHz for 14N NQR, the key feature of audio amplifiers is exact reproduction of input waveforms whereas for NQR the main focus is on exact shaping and repeatability of pulses, e.g., fast rise and fall times, low pulse overshoot and tilt, long term amplitude and phase stability.

Taking the inspiration from the portable audio amplification technology, we have set out to build a drop-in replacement for the current power amplifier in our portable QR detector. There are several approaches to class D amplification, the most common being the full H-bridge (4 transistor switches) and half-bridge (2 transistor switches) topologies.

Usually, a technique called pulse width modulation is employed to drive the switches. However, for accurate signal reproduction, the reference frequency has to be much higher than the maximum frequency of the signal with factors 5-50 typically used in practice. For NQR pulse amplification, a simpler modulation scheme was proposed [2]. Since in standard pulse sequences, the amplitude of the transmitted pulses does not vary, the original signal can be approximated with just 2 square pulses per period. In this way, the operational frequency of the driving circuit does not need to be increased.

We have designed a prototype half-bridge stage and verified its behaviour with SPICE-based computer simulations. In the following months, the device will be manufactured and tested on printed circuit boards with the goal of achieving fully working class D amplification at frequencies up to 5MHz and power levels up to 300W. In the future, we will incorporate the class D amplifier into our portable QR detector. This will allow for higher pulse power levels while sustaining or even extending the autonomous operational time running on a smaller, more lightweight battery. 

The phone in your pocket.  Helping to inspire the next generation of humanitarian demining equipment.

References

1. A. N. Garroway, M. L. Buess, J. B. Miller, B. H. Suits, A. D. Hibbs, G. A. Barrall, R. Matthews and L. J. Burnett, Remote Sensing by Nuclear Quadrupole Resonance, IEEE Trans Geo. Remote Sens. 39, 1108–1118 (2001).

2. Mandal, S., Utsuzawa, S., Cory, D. G., Hürlimann, M., Poitzsch, M., Song, Y., An ultra-broadband low-frequency magnetic resonance system. Journal of Magnetic Resonance, 242, 113–125 (2014).

Development Technology Workshop (DTW) - A short History

By Harold Pearson

DTW’s history goes back to 1994 when I came up with the original concept for developing cost effective quality de-mining equipment to be manufactured in countries affected with land mine and UXO pollution. The main aim of DTW is to provide a research and development, prototyping and where required, a production service to NGO’s and small private sector industry both in Cambodia and where appropriate, internationally.

By 1996 DTW, in association with the University of Warwick, was established as a limited company and a registered British Charity. At that time DTW had already carried out meaningful development work on protective clothing (PPE), visors and body armour as well as the development of de-mining hand tools. A number of us received field training with the British Royal Engineers who also helped us with the field testing of PPE and visors.  Most of the practical work was carried out in the University of Warwick’s workshops where I had very good relations with the workshop technicians or at my home workshop in Solihull in the west midlands.

In 1997 work began in UK on Tempest T1, a remote controlled vegetation cutter, with the completed machine being shipped to Cambodia in Nov 1998 where we had set up a small workshop funded through Norwegian Peoples Aid (NPA) based upon a proposal submitted some 12 month earlier. In 2000, we shipped all of our equipment from UK establishing DTW’s HQ in Cambodia. We do not now have any offices or salaried staff other than a part time accountant in UK, which makes us a very cost effective INGO.

Our engineers are all very experienced but non hold degrees, we use the CAD programme Solid Works and there are only two part time expatriate engineers who are resident in Cambodia

Though our main area of activity centred on demining activities DTW has also been involved in development of other equipment not related to demining, based upon the need identified by the recipient. (Please keep this in mind as it is an important factor when considering DTW’s relative success).

We already had several Cambodians working with us from previous time spent in Cambodia. These people became the core personnel of CDW (Cambodia Demining Workshop) involved with tailoring personal protective equipment (PPE), and visor manufacture.  CDW was handed over around 2001 and all protective equipment is now manufactured in Cambodia through Envostar a branch of Envotec. The Laing Foundation funded much of the PPE programme.

Some of DTW’s development achievements are:

• Tempest - 28 built and operated worldwide. The last two Tempests were withdrawn from service in Mozambique in 2014 after 13 years of service; Note the estimated working life was 3 years!
• PPE – unknown quantities manufactured and in use worldwide.
• De-mining hand tools around 1,000 sets produced in use with various organizations.
• Tractor towed graders developed for FAO, several in use.
• Two Container workshops- These were fully equipped workshops designed for the shipping and in field maintenance of Tempest.
• Folding guide canes for the blind – Several hundred manufactured and distributed as well as a complete manufacturing package of workshop tools and equipment including training being exported to South Africa in 2005 where manufacture continues.
• Development of a low cost Braille typewriter.
• Biogas cooker- Researched and developed by DTW with over 45,000 made and in use, a new model presently being developed. Please refer to the Cambodian National Biogas Programme (NBP) http://nbp.org.kh/
• Development and production of a disruptor/dearming system that utilises a blank cartridge for destroying AP mines in situ or dearming large ordnance by removing the fused cone. There is a hydraulic system for destroying soft targets and IED’s.
• A secure radio detonating system that obviates the use of long lengths of detonating cable when destroying recovered munitions.
• Training programmes in basic fabrication skills, machine shop skills, diesel engine maintenance. We would also be able to train in hydraulics, electrics and radio control systems. 

The above by no means covers all our activities over the last 17 years but I hope gives some idea.

I believe DTW also has design, development and prototyping capacity that is unique in the context of what is available in developing countries.  Complex design and prototyping has been completed by DTW for costs unimaginably low compared with those in developed countries. It is unfortunate the development community both private and humanitarian has failed to recognize this which has resulted in DTW being underutilized and severely underfunded. It is a fact that over the past ten years we have not received a donation or support funding for any projects proposed by us. All our income has been derived from projects requested and specified by outside organisations and completed by DTW according to an agreed contract. DTW differs from most NGOs in that it operates in many ways like a private company, working to contracts, delivering to customer orders, and being paid for goods and services provided.

I would like to address the issue raised by Mr Thrish Nanayakkara concerning the apparent lack of interest by the demining community in new ideas related to mine clearance:

There is an old saying that goes “If it ain’t broke don’t fix it” The operating procedures (SOP’s) for the humanitarian clearance of land mines and UXO have taken years to develop. Operators worldwide tend to work to these standards and therefore the left hand has a good idea what the right hand is doing anywhere in the world.

As I understand the international standard for humanitarian mine clearance is 99% and that to date a machine does not exist to achieve this. Over the years there have been a number of “crackpot” ideas proposed, that have even gained financial support from those who do not know better. Some of you reading this will be aware of current ideas doing the rounds.

The demining community has a problem understanding why they should use a machine that will only partially clear mines as existing processes would still be required to complete the process to a satisfactory standard?

There are good reasons why deminers are reticent to make changes and that is because of the risk involved. There is a parallel here with farmers and farming. Try to get a farmer anywhere in the world to change his practices or equipment and see how far you get! Having worked in rural Africa for 30 years I do know what I am talking about.

So what to do?

First it is very important to convince the potential users you know what you are talking about and fully understand the existing problems and not those related only to clearance. A photograph or video of a prototype working in a nice flat field out the back of a university is unlikely achieve this.

Disposal is becoming more refined, simply blowing things up using HE is becoming less acceptable with demands for more ergonomic methods. With the now present terrorist threat the less HE around the better! 

I can assure the reader that DTW was given the “brush off” on a number of occasions in the early days but gradually gained respect by not trying to impose ideas; rather we requested input concerning the needs of the demining community. This resulted, for example, in requests for a better design of PPE and protective visors more suited to humanitarian needs and cost effective. Being based in Cambodia we were able to develop prototype PPE using cardboard for the filler and appropriate material for the outer covering. The deminers came for fittings and gave their inputs to the design. Then within weeks we had a satisfactory design that continues to set the standard internationally.

Development of the ballistic lining was also carried out by DTW using initially Kevlar but later Twaron. Obtaining official accreditation to be able to manufacture protective clothing is both expensive and time consuming involving international testing at thousands of $ per day. We got round this problem by developing our own ballistic test facility using chronographs and simulated fragments and velocities that conformed to STANAG 2902 - V50. This service is still available should anyone need it?

Upon the completion of our testing samples were sent to the USA, tested and given official accreditation. All this took place from concept to production in just over one year.

The Tempest programme was also a result of requests from the demining community for an affordable easy to fix machine for clearing brush and heavy vegetation, not mines! It was also important the machine was light enough to be carried on a 3 ton truck across the small bridges found in Cambodia and other countries.

I won’t go on only to say that all our projects have been the result of needs as identified by the end users and not DTW promoting its own inventions/innovations. To all the academics, those working on high powered R&D programmes please remember there is no substitute for experience. DTW sits in a unique position of not being a demining organisation but of having 17 years working experience in that field. We are able to communicate with the deminers, to be heard and respected.

Please take the time to look at our website at www.dtw.org.kh

Harold Pearson – DTW General Manager                                                  
Mobile +855(0)12812031

AQUAREOS: The Story So Far

If we look at the procedure for humanitarian mine clearance we see that, once the ground is prepared, the process has two steps: 1) target location; and 2) confirmation that the target is a buried landmine.  Target location is accomplished by some form of remote sensing – a metal detector swept over the ground, or a dog doing a search etc; while confirmation that the target is a buried landmine generally involves direct contact with the target – the so-called “prodding and excavation” procedure.  There are new sensors, and combinations of sensors (e.g. MINEHOUND – MD+GPR) that allow, or aim to allow, for remote sensing for confirmation that the target is a buried landmine – when you consider that there may be 1000 false alarms for

every mine found it is easy to see why this is so: it removes the need to investigate every target located, saving a lot of time.

One technique being considered for confirming the target is a landmine is Quadrupole Resonance (QR), its great advantage being it directly detects the chemical signature of the explosive content of the mine.  As a radiofrequency technique, QR lends itself to remote sensing.  However, as a near-field method (frequencies for nitrogen QR range from 0 – 5.5 MHz) there is considerable signal attenuation with increasing separation between the sensor and the target (i.e the deeper the mine, the weaker the signal).  There is equally, a great deal of RF power attenuation for the same reason, meaning that considerable RF power is needed to “reach” buried mines.  In combination with the already-weak QR response, these factors represent a considerable challenge for the implementation of QR as a remote sensor for confirming that a target is a buried mine.  Our AQUAREOS project is designed to meet that challenge, using a combination of novel hardware design and advanced signal processing in a rugged, simple-to-use package.

Progress across the first six months of the project has been good.  A proof of concept AQUAREOS quadrupole resonance mine sensor device has been constructed and mounted on an all-terrain cart.  The proof of concept device uses a digital spectrometer platform with a class A/B RF power amplifier, both powered by a single rechargeable battery with ca 4 hours of battery life.  Control of the device can be via either a laptop/ tablet, or via the controls on the handle.  In addition to be operated from the cart, the device is inside a weatherproof carry case that suspends from the shoulder by a strap.  This is to test portability.  Output is a simple yes/no for the presence of the explosive being searched for indicated both by lights on the handle and on the laptop/tablet display.  Right now the signal processing algorithm uses primarily the signal intensity for discrimination, but this will be refined as the project progresses. 

This proof of concept device is used primarily for optimisation of the CONOPS (concept of operation).  In the next stage of the project, this aspect of the work will focus on the design and construction of the second-generation device with upgraded RF power in a smaller package. Jamie Barras.

Jamie Barras (http://nms.kcl.ac.uk/core/?page_id=895) is the leader of the Quadrupole Resonance Group within the Department of Informatics, King’s College London.  The AQUAREOS team thank Find A Better Way (http://www.findabetterway.org.uk/) for funding this work.

Further Reading

1.  J. Barras, M. J. Gaskell, N. Hunt, R. I. Jenkinson, K. R. Mann, D. A. G. Pedder, G. N. Shilstone and J. A. S. Smith, Detection of Ammonium Nitrate inside vehicles by nuclear quadrupole resonance, Applied Magnetic Resonance 2004, 25, 411 – 434.

2.    A. N. Garroway, M. L. Buess, J. B. Miller, B. H. Suits, A. D. Hibbs, G. A. Barrall, R. Matthews and L. J. Burnett, Remote Sensing by Nuclear Quadrupole Resonance, IEEE Trans Geo. Remote Sens. 2001, 39, 1108 – 1118.

Project AQUAREOS at King's College London & Find A Better Way

Welcome to the Humanitarian demining R&D blog. The purpose of this blog is to provide a forum for researchers and end users in humanitarian demining to exchange views and to start collaborations. The initial step of this effort is supported by an award from the UK Royal Academy of Engineers (RAE).

We will create an initial group of engineering researchers who will try to engage with end users and obtain feedback on the research they are doing. We will also keep Philanthropists informed about the technology needs and other practical problem faced at the ground level.

About me: At present, I am an academic in the Department of Informatics, King's College London. I was born in Sri Lanka, where there has been a 30 year long war that left behind a large number of anti-personal landmines to be cleared before re-settlement of civilians. When I was at University of Moratuwa, Sri Lanka, my laboratory tried to train mongoose to detect landmines, which was also featured in Harvard magazine. I also tried to develop semi-autonomous mobile robots to either carry metal detectors or to guide trained animals like mongoose in unchartered terrain. With the above R&D work, I engaged with several NGOs and Government groups that were involved in demining.

Why I am interested in this public engagement project: Having tried various ways to contribute some technology for humanitarian demining for more than 10 years, still none of what I tried is being used on the ground level on a regular basis. Still, vast majority of end users choose gardening rakes or metal detectors despite their high false alarm rate. One of the barriers to introduce more efficient technologies often quoted by end-users is that the technology must be simple enough to suit the local people being employed in many demining projects in the World. I am not entirely convinced that it is the technology that causes the problem, because most of these so-called "underprivileged" local people use mobile phones and use reasonably sophisticated other electronic consumer products in their households. So, the problem is more likely to be in the user interface or in the recommended training procedures. There can be other reasons why most technologies do not reach the ground level. This public engagement project is to share views of other research engineers and end-users to charter a new interdisciplinary engagement approach to empower both academic researchers and end-users so that the affected communities in nearly 70 countries in the World will see faster and safer humanitarian demining methods at the ground level.

How to write posts: Please email me your posts with a suggested title.