Approximating a Slider-Crank Acceleration Profile w/ Vibration Motors

In summary, the conversation discusses the possibility of building a mechanical device with an asymmetric acceleration profile using eccentric rotating mass vibration motors that are synchronized and initialized properly. The idea of using a DCT or FFT to synthesize the acceleration pattern is mentioned, along with the use of sinusoidal harmonic vibrators. The accuracy of the alternative implementation is not important, as long as the asymmetric acceleration is achieved. The suggestion of using a miniature device such as a speaker voice coil or piezo electric transducer is brought up, with a MOSFET used to connect it to the supply to achieve the desired acceleration profile. The idea of using a jack hammer or hammer drill for larger scale applications is also mentioned.
  • #1
adishavit
5
0
Say I have a mechanical device like this one:

mdk6l.png


If I plot the acceleration profile at (trace-) point D I get something that looks something like this:
thSNy.png


Now, here's the question:

Can I build a device composed of one of more (eccentric rotating mass) vibration motors that when rotating will approximate this acceleration profile?
Let us assume that they can be synchronized and initialized properly (as stepper motors can).

Ideally I'd like to have as few such motors as possible.
Maybe some DCT-like transform of the profile?

I'm not a-physicist nor a mechanical engineer, so be gentle.
 
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  • #2
I don't know the answer,but is it a Whitworth shaper? Asking because the acceleration profile looks so skewed.
 
  • #3
The mechanism is as drawn in the diagram. It is not the Whitworth shaper, but it was designed to has an asymmetric acceleration profile.
 
  • #4
You might synthesise that acceleration pattern from the Fourier components.
If you have sinusoidal harmonic vibrators that are synchronised, then you will need several harmonics to approximate the acceleration spike.
 
  • #5
Baluncore said:
You might synthesise that acceleration pattern from the Fourier components.
If you have sinusoidal harmonic vibrators that are synchronised, then you will need several harmonics to approximate the acceleration spike.

Yes. That was my thinking too.
I mentioned DCT ([Discrete] Cosine transform) which has good signal de-correlation attributes. I'm glad this idea was not so far-fetched.
Would FFT be better than DCT (or DST = Sine Transform)?

What exactly are "sinusoidal harmonic vibrators"?
 
  • #6
They are something like your "Can I build a device composed of one of more (eccentric rotating mass) vibration motors that when rotating will approximate this acceleration profile? Let us assume that they can be synchronized and initialized properly (as stepper motors can)."
Stepper motors can miss steps during acceleration so they would need some form of phase trimming to keep them in time.
I would use an FFT to compute the most significant phase and amplitude requirements for emulation.
 
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  • #7
Seems to me that the acceleration spikes are the key and the recovery waveform is probably non-critical. So why not use an electric jack hammer or a hammer drill to make the acceleration pulses.
Then, if you need to cultivate the rest of the signal, use a simple eccentric vibrator.
How accurate does the alternative implementation need to be?
 
  • #8
Baluncore said:
How accurate does the alternative implementation need to be?
Not very. Indeed, the important part is the asymmetric acceleration - higher in one direction with a slower return.

Baluncore said:
Seems to me that the acceleration spikes are the key and the recovery waveform is probably non-critical. So why not use an electric jack hammer or a hammer drill to make the acceleration pulses.
Then, if you need to cultivate the rest of the signal, use a simple eccentric vibrator.

I want a miniature device - think pager-motors.
Jack hammers are a tad too big.
 
  • #9
Sorry, but I misinterpreted the scale by several orders of magnitude.
I really don't like the idea of multiple motors at that scale.

This seems like an application for a speaker voice coil or a piezo electric transducer.
Use a MOSFET to connect it to the supply momentarily, then discharge slowly through a resistor, wait and repeat.
 
  • #10
Baluncore said:
This seems like an application for a speaker voice coil or a piezo electric transducer.
Use a MOSFET to connect it to the supply momentarily, then discharge slowly through a resistor, wait and repeat.
Thanks. I'll consider that.
 

Related to Approximating a Slider-Crank Acceleration Profile w/ Vibration Motors

1. What is the purpose of approximating a slider-crank acceleration profile with vibration motors?

The purpose of approximating a slider-crank acceleration profile with vibration motors is to simulate the motion of a slider-crank mechanism, which is commonly used in various mechanical systems, such as engines and pumps. This simulation can be used for testing and optimization of the mechanism's performance.

2. How does the approximation process work?

The approximation process involves using vibration motors to generate acceleration pulses that mimic the motion of a slider-crank mechanism. These motors are controlled by a microcontroller, which can be programmed to produce specific acceleration profiles based on the desired simulation.

3. What are the key factors to consider when approximating a slider-crank acceleration profile with vibration motors?

The key factors to consider include the size and power of the vibration motors, the programming of the microcontroller, and the placement of the motors to accurately replicate the motion of the slider-crank mechanism. It is also important to consider the materials and design of the simulated system to ensure a realistic simulation.

4. What are the advantages of using vibration motors for approximating a slider-crank acceleration profile?

Using vibration motors for approximation offers several advantages, including cost-effectiveness, ease of control and programming, and the ability to simulate a wide range of acceleration profiles. It also allows for a non-intrusive simulation, as the motors can be attached to the outside of the mechanism rather than being integrated into it.

5. Are there any limitations to using vibration motors for approximating a slider-crank acceleration profile?

One limitation of using vibration motors is that they may not be able to accurately replicate all aspects of the motion of a slider-crank mechanism, such as the rotational component. Additionally, the accuracy of the simulation may be affected by factors such as motor wear and tear, environmental conditions, and the complexity of the desired acceleration profile. Further research and testing may be necessary to optimize the accuracy of the approximation.

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