## Practical noise reduction tips for biomedical ECG datasets

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In ECG signal processing, the Removal of 50/60Hz powerline interference from delicate information rich ECG biomedical waveforms is a challenging task! The challenge is further complicated by adjusting for the effects of EMG, such as a patient limb/torso movement or even breathing. A traditional approach adopted by many is to use a 2nd order IIR notch filter:

$$\displaystyle H(z)=\frac{1-2cosw_oz^{-1}+z^{-2}}{1-2rcosw_oz^{-1}+r^2z^{-2}}$$

where, $$w_o=\frac{2\pi f_o}{fs}$$ controls the centre frequency, $$f_o$$ of the notch, and $$r=1-\frac{\pi BW}{fs}$$ controls the bandwidth (-3dB point) of the notch.

### What’s the challenge?

As seen above, $$H(z)$$ is simple to implement, but the difficulty lies in finding an optimal value of $$r$$, as a desirable sharp notch means that the poles are close to unit circle (see right).

In the presence of stationary interference, e.g. the patient is absolutely still and effects of breathing on the sensor data are minimal this may not be a problem.

However, when considering the effects of EMG on the captured waveform (a much more realistic situation), the IIR filter’s feedback (poles) causes ringing on the filtered waveform, as illustrated below:

Contaminated ECG with non-stationary 50Hz powerline interference (IIR filtering)

As seen above, although a majority of the 50Hz powerline interference has been removed, there is still significant ringing around the main peaks (filtered output shown in red). This ringing is undesirable for many biomedical applications, as vital cardiac information such as the ST segment cannot be clearly analysed.

The frequency reponse of the IIR used to filter the above ECG data is shown below.

IIR notch filter frequency response

Analysing the plot it can be seen that the filter’s group delay (or average delay) is non-linear but almost zero in the passbands, which means no distortion. The group delay at 50Hz rises to 15 samples, which is the source of the ringing – where the closer to poles are to unit circle the greater the group delay.

ASN FilterScript offers designers the notch() function, which is a direct implemention of H(z), as shown below:

ClearH1;  // clear primary filter from cascade
ShowH2DM;   // show DM on chart

interface BW={0.1,10,.1,1};

Main()

F=50;
Hd=notch(F,BW,"symbolic");
Num = getnum(Hd); // define numerator coefficients
Den = getden(Hd); // define denominator coefficients
Gain = getgain(Hd); // define gain

## Savitzky-Golay FIR filters

A solution to the aforementioned mentioned ringing as well as noise reduction can be achieved by virtue of a Savitzky-Golay lowpass smoothing filter. These filters are FIR filters, and thus have no feedback coefficients and no ringing!

Savitzky-Golay (polynomial) smoothing filters or least-squares smoothing filters are generalizations of the FIR average filter that can better preserve the high-frequency content of the desired signal, at the expense of not removing as much noise as an FIR average. The particular formulation of Savitzky-Golay filters preserves various moment orders better than other smoothing methods, which tend to preserve peak widths and heights better than Savitzky-Golay. As such, Savitzky-Golay filters are very suitable for biomedical data, such as ECG datasets.

### Eliminating the 50Hz powerline component

Designing an 18th order Savitzky-Golay filter with a 4th order polynomial fit (see the example code below), we obtain an FIR filter with a zero distribution as shown on the right. However, as we wish to eliminate the 50Hz component completely, the tool’s P-Z editor can be used to nudge a zero pair (shown in green) to exactly 50Hz.

The resulting frequency response is shown below, where it can be seen that there is notch at exactly 50Hz, and the group delay of 9 samples (shown in purple) is constant across the frequency band.

FIR  Savitzky-Golay filter frequency response

Passing the tainted ECG dataset through our tweaked Savitzky-Golay filter, and adjusting for the group delay we obtain:

Contaminated ECG with non-stationary 50Hz powerline interference (FIR filtering)

As seen, there are no signs of ringing and the ST segments are now clearly visible for analysis. Notice also how the filter (shown in red) has reduced the measurement noise, emphasising the practicality of Savitzky-Golay filter’s for biomedical signal processing.

A Savitzky-Golay may be designed and optimised in ASN FilterScript via the savgolay() function, as follows:

ClearH1;  // clear primary filter from cascade

interface L = {2, 50,2,24};
interface P = {2, 10,1,4};

Main()

Hd=savgolay(L,P,"numeric");  // Design Savitzky-Golay lowpass
Num=getnum(Hd);
Den={1};
Gain=getgain(Hd);

## Deployment

This filter may now be deployed to variety of domains via the tool’s automatic code generator, enabling rapid deployment in Matlab, Python and embedded Arm Cortex-M devices.

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## Industry 4.0: Asset Track and Trace

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When considering an asset track and trace IoT application in a factory or warehouse, many think of the well-established Barcode or QR code. Although this technology is firmly embedded into modern society as a reliable, low cost and easy to understand pillar for tracking and tracing assets, many companies were quick to adopt the technology as an easy way of minimising human errors and increasing process efficiency.

However, when managing the location of thousands of assets, this simple system is somewhat limited in the overview that it can provide an ERP (enterprise requirements system) system. A significant aspect of Industry 4.0 is process transparency, providing the ERP and BI (business intelligence) systems with the most update-to-date information, allowing management to identify bottlenecks and potential areas of weakness.

Until several years ago, asset tracking was strengthened by combining RFID tags with GPS (global positioning system) technology. Although this was certainly a step in the right direction, the implementation costs were high and technology suffered from RF interference, short range and moderate location accuracy. GPS also had the big disadvantage of only being able to work outdoors and has a location accuracy of several metres – not really suitable!

## Industry 4.0 real time location systems (RTLS)

Over the years, different technology has appeared as solution to providing real-time assets location information to the ERP system. As mentioned above, technologies, such as RFIDs, bar codes and GPS have certainly been a step in the right direction, but didn’t fully meet the requirements of modern businesses look to optimise their processes.

With advances in radar technology over the last few years, a few silicon vendors are now producing affordable UWB radar devices suitable for trace and trace applications. Radar technology that used to cost thousands of Euros, and was primarily aimed a military technology, is now available for tens of Euros, making it viable candidate for track and trace applications.

UWB highlights

• Ten times more accurate than GPS, Wi-Fi or Bluetooth with typical accuracies a good as 10cm.
• Hundreds of metres range with data communication options.
• Very low power and safe for humans – power emission typically a fraction of percent of a typical Wi-Fi router.
• Licence free ISM band, meaning no complicated ETSI/FCC certification and lower implementation costs.
• Penetrates walls and doors, making it ideal for warehouses and buildings.

Contemporary UWB based solutions finally allow for a true RTLS implementation, giving enterprises control over their personnel and assets. Whether tracking containers through a supply chain, optimising manufacturing processes, or providing asset traceability, an RTLS-UWB system provides an ERP system with real-time situation awareness that can be acted upon instantly.

• Inventory accuracy: achieve 99.9% inventory accuracy without the need for meticulous manual audits that can take hours or even days. An RTLS-UWB system provides you with all of your asset location information in real-time.
• Live situation update: feed the ERP and BI systems with an accurate real-time picture of asset location and personnel trends.
• Personnel safety: attaching tags to your employees helps track process efficiency and may also be used to alert personnel about entering dangerous areas. The tag locations are also invaluable in case of an emergency, such as fire, as the location of all personnel is known at all times.
• e-paper and sensors: modern tags use e-paper technology to only display the most up-to-date information (e.g. QR code, sensor readings). Extra sensor information, such as temperature, humidity and vibration provide a simple way of establishing anti-tampering and asset health.

Advanced Solutions Nederland (ASN) BV is an international market leader in innovative IoT smart sensor and track and trace RTLS-UWB technological solutions.

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## How drones fuel ‘smart air’: Delivery drones

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Where ‘smart traffic’ has already 417 billion hits on google, I only found ‘smart air’ for a kind of door lock and ‘smart drone’ for an advanced toy drone. But definitely, drones are so hot that they will become part of something called ‘smart air’. The SESAR project predicts that drones will make 250 billion hours of flight in the European Union alone. For comparison: this is far more than the air traffic of ‘normal’ airplanes today.

Because drones are using many sensors, we did some research how the use of drones can grow to maturity and fuel ‘smart air’. Today we talk about challenges for delivery drones.

## Delivery drones

No wonder, drones have proven to be very convenient already and have even more promises in store. Soon, it will be commonplace that drones are delivering packages, from hot pizzas to even more urgent medicines. And even humans: the first drone taxis are already being tested. At this moment, drones are already used for drag-and-drop deliveries in some rural and faraway areas. Most articles on the internet talk about the use in drones in big city areas. And there they have the big advantage of an -still- almost empty sky instead of congested roads and overfull parking places. For that, delivery by drones will be faster and more predictable.

But until use of drones are entirely tried and tested, most drone developments will take place on rural environments. Because here the risk of large damage is a lot smaller when something will go wrong. In time, delivery drones will still be used in rural places. Maybe as a standalone, maybe in combination with self-driving trucks. Reach will not be a big problem, since the whole word is getting connected fast. So, reach will almost only depend on battery endurance. And for now, these batteries have only a limited capacity for distance and cargo.

## Challenges while travelling

Like all delivery services, drone delivery has to a pick-up a package, travel to the destination and drop-of the package.  While travelling, drones have to know how to reach their destination. Meanwhile, there are some challenges:

• Risk of colliding, with other drones, birds and other air users. Just like other traffic
• And at point in time, some traffic rules have to be set in place. Sensors can help to let the drone follow these rules
• How drones can stay on course, even with wind
• Preventing drones to cross over forbidden (known) areas and unexpected ‘wrong’ areas (e.g. a building or a wood on fire)
• How to prevent a package from falling? How to alert that a package will probably fall? Or maybe the drone itself? If so, measurement can be taken. Already, there are experiments with self-destruction. But maybe more practical solutions can be found to let the drone aim for a ‘safe area’, such as a park, river, etc. for an ‘emergency landing’
• Acceptance of drones beside safety: how to guarentee privacy when drones are flying over peopled areas? Then there is the issue of noise: research shows that people find the noise of drones one of the most annoying forms of noise

## Challenges with dropping the cargo

For now, the drop-of is literally done by dropping-of the cargo. Maybe with the aid of a cord which places the package as soft as possible to the ground. But anyhow: the drone stays in the air. So, technology has to get safe: for the package to be delivered undamaged. How does the drone know that the right person gets the package? And we have to prevent dogs from biting the package. And of course, to prevent that the dropped cargo will harm humans, animals or buildings or even worse.

## The use of sensors

The application possibilities of drones are very promising for delivery uses. It is still in its experimental phase. But with developments going fast, soon it will reach the maturity phase. For this, there are two-fold kind of challenges.

Some are challenges on privacy, safety and security. These challenges have to be solved before the use of drones will get widespread trust and acceptance. The other are technical and communication issues: where multiple drones are being used – especially in cities- challenges how drones can and have to behave in traffic has to be solved.

In both challenges, sensors play a pivotal role in solving the technical questions. In all cases, ASN Filter Designer can help with sensor measurement with real-time feedback and the powerful signal analyzer. How? Look at ASN Filter Designer or mail ASN consultancy: designs@advsolned.com

Do you agree with this list? Do you have other suggestions? Please let us know!

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## How to measure preventative maintenance

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Typical challenges faced by assets managers include:

• How to measure mechanical component fatigue?
• How to assess electrical wiring health?
• How to reduce overall operating costs, but not comprise on public safety?
• Risks posed by hackers & terrorists
• Asset damage due to vandalism

Preventative Maintenance aims to solve the aforementioned problems by acting pre-emptively. This is achieved by constantly monitoring the performance of critical components (usually with sensors) and then alerting the maintenance team that a component is about to fail. The asset management team can then schedule maintenance in order to replace the failing component(s) with minimum disruption to the public, and overall lower operational costs.

• Plan maintenance
• Machine health care
• Motor health care
• Secure firmware updates and anti-tampering

## Plan maintenance

Monitoring the health of critical component, such as a lamp, motor or machine component and input power supply. Our algorithms and analytics help asset management departments provide planned maintenance.

A better maintenance program is achieved by constantly monitoring the performance of critical components (usually with sensors or other devices) and then alerting the maintenance team that a component is about to fail.

## Machine health care

The health of a machine can be determined by ‘listening’ to the sound it makes via microphones. Algorithms filter and compare recorded audio to fingerprint templates of known failures.

## Motor health care

The health of an industrial motor be determined by analysis the phase currents. Algorithms filter and compare captured data to fingerprints templates of known failures. The phase current data can also be used to check for wire breaks or phase failure.

## Secure firmware updates & Anti-tampering

ASN’s security module provides asset protection up to military grade, and while at the same time allowing for secure (encrypted) firmware updates.

ASN contactless measurement, smart algorithms and alerting offers the ideal condition for this programme. The asset management team can then schedule maintenance in order to replace the failing component(s) with minimum disruption to the public, and overall lower operational costs.

Let’s make an appointment to see how can help you create an effective maintenance programme and reduce your Total Cost of Ownership.

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## Preventative motor maintenance: save up to 51% of your maintenance budget!

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Industrial induction motors are found everywhere: Lifts, escalators, cable cars, water sluices, cranes, and even washing machines etc. Motors form the backbone of these devices. Since they are mission critical, a failure of a motor may disrupt the whole production line, crippling your precious infrastructure as a whole. As an example: if the motor fails on a water sluice, the disruption means that ships can’t deliver their cargo on time. Our experience has shown that with preventative motor maintenance, you can save up to 51% of your maintenance budget!

## Common sources of industrial motor failure

Of course, each industrial motor has its own characteristics. However, common sources of failure in an industrial induction motor are:

• Ball bearing and rotor crack/break
• Stator winding faults
• Rotor winding faults (rotor bars, end-rings etc.)

## Save up to 51% with preventative maintenance

For public infrastructure, industrial motors are mission critical. They need to be regularly be checked under expensive maintenance programmes. With ASN’s IoT solutions, you can predict and prevent equipment failure by monitoring product wear and replacement rates.  And if you recognize a slight disturbance, you can solve them easily. Before little faults have become big and expensive problems. When little faults are recognized, they can be repaired without any signifcant downtime. At a time it suits your client best. As such, you can improve the reliability of your assets and reduce downtime.

## Effective and efficient use of an engineer’s precious time

Motor health care starts with sensors. With these sensors, you can monitor the running of your monitors automatically by placing sensors in the vicinity of your motors. When a signal pops up that there might be a problem, an engineer can repair this motor. Previously, engineers did their inspection rounds, giving every motor the same attention. Now, engineers can focus on motors that really need attention.

With preventative maintenance, your customers  can save a fortune and minimise any disruption to service. You can save up to 51% on your maintenance costs with our Preventative Maintenance solutions. They are based on safe contactless sensor measurement, and optimize the life expectancy of your industrial motor. Learn more at: https://www.advsolned.com/motor-health-care/ or drop us a line at: info@advsolned.com

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## Keeping the employee satisfied: coffee drinks dispenser case

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A leading coffee manufacturer wanted to add a function to their coffee machines that could fill every kind of mug (small, large, glass, ceramic) fully or half-fully. The requirement was that system must be able to automatically find the dimensions of the mug and track the filling process in real-time without human intervention.

A lot of time is wasted due to coffee spills due to overfilled coffee mugs, but the challenge was to see if this could be done for a reasonably low cost – around 10 EUR.

As no other coffee machine manufacturer had a flexible solution for their coffee machines, this would give them a competitive advantage as well as add a exciting new gadget to their product portfolio.

Find out how we solved this challenge here: coffee drinks dispenser case

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## How sensor measurement can improve the performance of drones

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Until now, the professional use of drones is mostly still in an experimenting stage. However, drones are one of the golden nuggets in IoT because they can play a pivotal role, for instance in congested cities and faraway areas for delivery. Further, they can be a great help to give an overview of a large area or for places which are difficult or dangerous to reach.

In one of our previous blogs, we concluded that sensor measurement has mostly been a case of trial and error. In this blog, we list some of the challenges we see for sensor measurement which has to be solved to bring the professional use of drones to full maturity.

Practical challenges which can and must be solved with sensors

Here are some of the challenges we have found:

• Risk of colliding, with other drones, birds and other air users. Just like other traffic
• And at point in time, some traffic rules have to be set in place. Sensors can help to let the drone follow these rules
• How drones can stay on course, even with wind
• Preventing drones to cross over forbidden (known) areas and unexpected ‘wrong’ areas (e.g. a building or a wood on fire)
• Without damage
• Without harming people, animals, buildings
• How the drone will know that the right person gets the package? Can we prevent dogs from biting the package?
• How to prevent a package from falling? How to alert that a package will probably fall? Or maybe the drone itself? If so, measurement can be taken. Already, there are experiments with self-destruction. But maybe more practical solutions can be found to let the drone aim for a ‘safe area’, such as a park, river, etc. for an ‘emergency landing’.

In all cases, ASN Filter Designer can help with sensor measurement with real-time feedback and the powerful signal analyser? How? Look at ASN Filter Designer or mail us: info@advsolned.com

Do you agree with this list? Do you have other suggestions? Please let us know!

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## Why motor producers should care about their life expectancy

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Motor producers are beginning to see that they can add value through preventative maintenance. However, when we speak to motor producers, sometimes companies begin to laugh when we ask them if they deliver health care monitoring through sensors to their customers already. They think that preventative maintenance is an enemy of their motor production:

“if motors can be made to run longer, we have less to sell”.

And sometimes companies just look glassy-eyed:

“We’re an old-fashioned company”.

Customers want you to deliver solutions, not motors

This is old fashioned thinking indeed. And like every other lagged thinking, these companies will get obsolete.  In old days, you could sell a ‘product’ with features such and such. Nowadays, customers are solely interested in the solution a company delivers. Customers want their business to run smoothly and without downtime. In this way of thinking, a motor is not a thing with a rotor, bearings and such, but it is a means which guarantees that a whole production line runs smoothly and without interruption.

Safe and sound running motors makes a customer satisfied

So, customers are more satisfied when their motor is running properly. And when it begins not to run properly, they want to know beforehand before a slight disturbance has become a real problem. When they know beforehand, they can take proper action on time, which means lesser costs and in most cases without downtime or at least as short as possible. Because downtime affects the production line in the whole. When the motor has really problems, your customer is forced to get their production on hold for a long time. Then customers not only have to face bigger repair costs. But mostly, costs are higher because now the whole production line has fallen out.

Motor health care starts with sensors

By placing sensors in the vicinity of your motors or even building them in, you can monitor the running of your motors automatically. When a signal pops up that there might be a problem, an engineer can repair this motor. This is also the modern way: previously, engineers did their rounds of motor inspections, giving every motor attention. Now, engineers can focus on motors that need attention.

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## ASN Filter Designer supports all Arm Cortex-M demo-boards

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Did you know that there are 23 billion IoT embedded devices currently deployed around the world? This figure is expected to grow to a whopping 1 trillion devices by 2050!

Less known, is that 80% of IoT devices are based around Arm’s Cortex-M microcontroller technology. Sometimes clients ask us if we support their Arm Cortex-M based demo-board of choice. The answer is simply: yes!

## 200+ IC vendors supported

The ASN Filter Designer has an automatic code generator for Arm Cortex-M cores, which means that we support virtually every Arm based demo-board: ST, Cypress, NXP, Analog Devices, TI, Microchip/Atmel and over 200+ other manufacturers. Our compatibility with Arm’s free CMSIS-DSP software framework removes the frustration of implementing complicated digital filters in your IoT application – leaving you with code that is optimal for Cortex-M devices and that works 100% of the time.

The Arm Cortex-M family of microcontrollers are an excellent match for IoT applications. Some of the advantages include:

• Low power and cost – essential for IoT devices
• Microcontroller with DSP functionality all-in-one
• Embedded hardware security functionality
• Cortex-M4 and M7 cores with hardware floating support (enhanced microcontrollers)
• Freely available CMSIS-DSP C library: supporting over 60 signal processing functions

## Automatic code generation for Arm’s CMSIS-DSP software framework

Simply load your sensor data into the ASN Filter Designer signal analyser and perform a detailed analysis. After identifying the wanted and unwanted components of your signal, design a filter and test the performance in real-time on your test data. Export the designed design to Arm MDK, C/C++ or integrate the filter into your algorithm in another domain, such as in Matlab, Python, Scilab or Labview.

Use the tool in your RAD (rapid application development) process, by taking advantage of the automatic code generation to Arm’s CMSIS-DSP software framework, and quickly integrate the DSP filter code into your main application code.

Let the tool analyse your design, and automatically generate fully compliant code for either the M0, M0+, M3, M4 and the newer M23 and M33 Cortex cores. Deploy your design within minutes rather than hours.

## Proud Arm knowledge partner

We are proud that we are an Arm knowledge partner! As an Arm DSP knowledge partner, we will be kept informed of their product roadmap and progress for the coming years.

Try it for yourself and see the benefits that the ASN Filter Designer can offer your organisation by cutting your development costs by up to 75%!

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