How does a smart floor work?

As sports engineers we develop lots of systems to help athletes perform better. Many of these system help by giving the athletes and their coaches more information about the way they move whilst they perform a sporting action. This includes measures such as speed, direction and many other specialised measurements for biomechanical analysis.

An example of such a system is our smart floor (or dance floor), something which lots of visitors to our museum exhibition have been asking about and enquiring how it works. To give you an overview I’ll give you a rundown of what it actually is, what all the bits in the system are, how they work and what the system can be used for.

What is a smart floor?

Our smart floor is a custom-built piece of equipment designed and manufactured by two of my colleagues at the Centre for Sports Engineering Research- Ben Heller and Terry Senior.

As its name suggests the smart floor is just that- an intelligent floor. Through the ‘intelligent tiles’ the floor is able to determine where you are stood on the floors surface and the way you are stood. The smart floor consists of a number of ‘intelligent tiles’, mounted on a supporting framework, a projector, projection screen and a controlling computer.

The video below shows all the component parts of the system and how they fit together.

How does it work?

clip_image002The functionality of the smart floor is achieved through its intelligent tiles. Think of each tile as an electronic bathroom scale and the floor as lots of bathroom scales connected together. So before we can start to understand how the smart floor works we need to understand the principals behind a bathroom scale.

When you take the top off a typical electronic bathroom scale you will see something similar to the picture above. The silver bars you see crossing the scale are in contact with the top of the scale when it is fitted. The bars are pivoted in each corner of the scale, meaning when someone stands on the top of the scale the bars are allowed to move downwards. The bars are all connected together so that when they move down they press on the large silver block you can see at the bottom middle of the scale. This metal block is actually a load cell and it is this which is used to determine how much you weigh.

clip_image004The load cell in the scales above looks something like the one above. There’s nothing magical about a load cell, it’s actually just a block of metal with a hole cut in the middle and some simple electronics. We’ll now talk more about how a load cell works.

When weight is applied to the scale the bars push down on one end of the load cell and deform it slightly, whilst the other end remains fixed. This means that the metal block from which the load cell is constructed is bent in relation to your weight. This bend is measured using strain gauges inside the load cell which convert the mechanical bending action into electrical energy.

A close up of a typical strain gauge found inside a load cell is shown in the image below. A strain gauge is essentially a number of loops of stretchy wire mounted on an equally stretchy backing. The strain gauges are glued to the metal block of the load cell so that as the load cell is bent the strain gauge is allowed to expand in length.clip_image006

As the load cell bends the strain gauge will expand in length. This also means that the wire loops in the strain gauge will also expand and will increase in length. Just like when you stretch a rubber band, as the wire loops are stretched in length they also become thinner.

This change in size of the wire loops changes their electrical properties. The diagram below helps to explain this.

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To help understand this, consider water moving through a pipe. It’s much easier for water to flow through a big pipe than a small pipe. Equally it’s much easier for the water to travel a short distance than a long distance.

Electricity is just the same, so when it passes through the wire coils in the strain gauge whilst no load is applied; it flows easily as the wire loops are short and thick. When load is applied the wire becomes longer and thinner, less electricity can flow through the wire and also has a longer distance to travel.

Reduction in the flow of electricity in this way is known as resistance. The resistance of the strain gauge will therefore change with the weight applied to the scales. The changing resistance of the strain gauge can be measured by connected electronic circuitry and used to determine the weight that was applied.

With this background we can now start to look at how our smart floor works.

The image below shows the underlying framework when two tiles have been removed. You can see that just like the bathroom scales there are load cells which are pressed down by the tile. The tile presses directly onto the load cells so we have no need for the metal bars we saw above.

A big difference you notice is that each tile or scale has four load cells under it instead of just one. This is the magic ingredient! With four load cells under each tile it means that not only can we determine the weight applied to the tile we can also determine where it is applied.

The strain gauges in each load cell are wired back to a circuit board as you can see above. The circuit board looks at the changing resistance of the load cells and uses this information to determine the weight applied to the tile and where it was applied. The circuit board is a custom made circuit board with an on board programmable chip to do the required mathematical calculations. The chip, known as a PIC chip is essentially a smaller and simpler version of the processor chips that are found inside everyday computers.clip_image010

The smart floor is a network of tiles that works in such a way that we can detect not only where someone is stood on each tile but where a group of people are standing on the floor.

What can we do with it!

So that’s all well and good, we can determine the weight or pressure applied to the tiles and where on the tile it is applied, but what can we actually do with that information? Or have we just made a big bathroom scale?

I’ll outline below some of the ways in which we’ve used the floor to date.

The smart floor we have installed at the museum is a smaller version of the one we have installed here at the Centre for Sports Engineering Research, Sheffield Hallam University. The version we have installed here (shown below) works in exactly the same way but has 36 floor tiles. In addition to this we have a projector mounted overhead, meaning that we can project images onto the floor surface as well as in front of the user. This opens up a whole world of additional possibilities!!

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Computer Games

An application of the smart floor which became quickly apparent was as a games controller for computer games.

The dance game used with the smart floor on show at the museum is a prime example of this. The floor tracks where and how you are stood on the floor and uses this information to animate a virtual reality character that is displayed on the projection screen. The character moves around with you and leans from side to side as you move from one side to another.

Another example is the implementation of a traditional ‘Pong’ game.

The smart floor tracks where two players on either side of the floor are stood and uses this information to move a puck in line with their feet. The game has an animated ball which players must prevent from exiting the court at their side by moving from side to side which in turn moves the puck to allow the ball to be bounced back to the opposition!

Whilst these games are fun to do, it’s also good for you! Applications such as this can be used to help encourage young children to become active and to exercise more.

Healthcare and rehabilitation

Applications in healthcare, rehabilitation and in particularly sports, was the primary intention of the floor when it was designed.

Sports and healthcare professionals are often interested in the way which we walk or run, something known as Gait analysis. This involves measuring factors such as stride length and foot spacing. The smart floor enables factors such as these to be measured by detecting the location of the feet after a stride has been completed.

Rehabilitation after illness or injury was another primary intention of the smart floor. Users can perform pre-set routines such as jumping or reaching at regular intervals and their performance analysed to determine if they are improving over time. Users can be provided visual feedback by the projection screen as well as providing visual encouragement.

A typical application in rehabilitation would be one of balance. The load cells in the smart floor enable you to determine if a user is leant to one side or not, meaning that we can get a measure of a person’s balance. We’ve developed software to project an image of the tightrope onto the floor for someone to walk along and for the data from the floor to be collected whilst they do this. This allows us to obtain balance measurements for a particular person, but also allows means we can test out products designed to improve your balance and see if they have any noticeable effect.

Summary

Hopefully everything I’ve discussed makes sense and has given you an insight into how our smart floor works.

Whilst the smart floor works well, and does everything we set out to achieve it’s worth mentioning that the technology in the floor is only at a very early stage. We’re expecting it to develop greatly over the forthcoming years and to add a whole bundle of new features.

The applications we’ve developed here to demonstrate what we can do with the floor only scratch the surface of the potential and diverse ways in which the floor can be used.

The smart floor we have currently are obviously standalone units, but in the future I expect technology such as this to become much smaller and even to become integrated into standard floors themselves!

As the technology and its implementation develops we hope to see systems such as this in use within the healthcare sector for diagnosis, treatment and post injury rehabilitation. We’d also like to see it in use in the sports sector to aid athletes in developing training routines to obtain their maximum performance.

If reading this potential has sparked any ideas for potential applications of the smart floor we’d love to hear from you!

Sean Clarkson

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About yachtingnut

Sean started his engineering career at the tender age of 4, continually ‘wiring’ up his parents’ house with string, wool and plastic socket protectors designed to stop him from being interested in electrics! The fact that he never managed to decapitate his mum and dad remains a mystery, but with this early interest Sean’s future career was sealed. Also apparent from an early age was Sean’s addiction to water, whether it be on top of it, under it or floating on it. After pursuing many water related sports including kayaking, scuba diving and sailing it was Sean’s first water sport he settled on- Sailing, something which he also started at a very young age. Sean competes regularly in many local and national yacht racing championships throughout England are Ireland with varying degrees of success, always attributed to the poor weather…..or so he says! Sean also has interests in other sports including; cycling, badminton, archery and golf. After graduating from Sheffield Hallam University with a BEng (Hons) degree in Electronic Engineering Sean then went onto complete an MSc in Electronics & IT also at Sheffield Hallam University. With such a strong interest in engineering and sport his next move of joining the Centre for Sports Engineering Research as a PhD researcher was only a natural progression. Sean’s main research area is developing 3D camera systems to analyse the way in which the body moves during motion (producing pretty pictures). From his electronics background Sean is also interested in developing instrumentation and feedback systems to measure the movement of athletes and the equipment they use. Sean has a strong interest in the application of consumer hardware such as the Xbox Kinect and Nintendo Wii remote to sports and has developed lots of fancy pieces of software to show off what they can do.

2 Responses

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