I am a French engineering student working on a project about tennis racket vibrations. I would like some advice on choosing the most suitable sensor for my application. I want to find the optimal spot of impact on a racket, validate my model, and find some interesting results. I do not know what sensor I must choose to archieve my project. I have heard about piezoeletric sensor or strain gauge.
The code is already finished and ready to go, the only thing missing is the sensor?
Would you know how to bond a strain gauge to your racket and where to put it?
There are quite a few commercial products that use accelerometers.
A piezo disk can give you vibrations at one spot with high fidelity.
Vibrations of machines and equipment are commonly measured as accelerations in units of distance per time squared. Is this what you are looking for? What is the physics of your project based on? Do you intend to compare your measurements with some previously defined limit or threshold? If so, what are the units of this parameter?
If you do want to measure accelerations, there are simple and inexpensive accelerometers that can interface to Arduino products.
Will you be trying to measure it is use during a game or will you set up a test rig and do it under controlled conditions?
I would imagine - never made it to Wimbledon - that the sweet spot is roughly in the centre in the handle axis (vertical), but not so in the horizontal axis.
It's going to be the point where the string deflection is optimum.
In the horizontal axis, it will vary with the head shape.
When you do manage to hit the sweet spot, it gives off a satisfying ping.
Cricket bats have a sweet spot, usually at the thickest part of the blade.
It could be tricky to do as anything attached to the racket could affect the measurement.
Eum no I am starting my projet
With a video i think I am able to do it
I don't think you are going to find a video of someone applying a strain gauge to a tennis racket for measuring sweet spot but maybe you will.
Have you looked?
I want to show that with the vibrations as only source of information I can find a lot of informations on the racket. In a first time i want to study the racket from a static point of view.(the racket will be attached to something) and maybe later in real conditions
No i want first to choose the sensor
Not for the moment but maybe later
The aim is to use vibrations in order to differentiate my sensor from the existing one that use accelerometers
Well if you choose strain gauge and have no idea of how or where to bond it to the racket then what is the point of choosing it first.
As I said it seems that the commercial products use accelerometers.
Do you have some notion of how you will know when you've found the sweet spot or is that something you need to determine as well?
I've played tennis (badly) and I've bonded hundreds of strain gauges. I can envision placing them alone the shaft of the tennis racket in such a way as to measure the "flex" and the "torque" of the shaft that might be somehow able to determine when the tennis ball has hit the sweet spot. Does that come anywhere near what you are proposing?
Define vibrations in scientific terms. You’re an engineering student- start with the basics of the problem before you start worrying about what sensor you’re going to use.
Yes insinctively I think that this is the spot where vibrations are the lowest because the energetical transfert is the best
I was thinking to place them around the frame of the racket but maybe your idea is better I need to test it
That may be true. How will you know that the ball hit the sweet spot so that you can correlate that with the vibration pattern? Is that one of the things you'll discover with you initial static tests?
Yes, doing some tests is in order. Maybe build a pneumatic ball cannon to use in a static test.