4
\$\begingroup\$

I am working on a project, where I have to measure the pressure exerted by a punch. I am trying to understand how an arcade machine works, and see if I could replicate the same mechanism in my project.

Additionally, I would like for the sensor to be in the punch-bag itself, which is different from an arcade machine. (They have the sensor directly on the back of the machine.)

\$\endgroup\$
9
  • 1
    \$\begingroup\$ I'm not sure but, an accelerometer maybe? The higher the punch pressure, the higher the moving speed (thus acceleration for a static object). \$\endgroup\$ – Rohat Kılıç Feb 12 at 5:24
  • 1
    \$\begingroup\$ There are a number of ways to do this. You need to be able to measure the acceleration of the object struck and there is a lot of danger in hitting something that doesn't move, which is probably why the ones I've seen use a pendulum. As long as you can measure the acceleration to an adequate accuracy, the pendulum formulas are pretty easy to figure out based on the mass of the pendulum, so you can calibrate it initially, but you would need a known striking force to calibrate it with to get real accuracy. \$\endgroup\$ – K H Feb 12 at 5:33
  • \$\begingroup\$ What kind of acclerometers would they have used in the past though? Haven't arcade boxing machines existed a lot longer than consumer MEMS accelerometers? Would they have really used an accelerometers and not just a spring centered mass connected to what is basically a joystick-like mechanism? \$\endgroup\$ – DKNguyen Feb 12 at 5:43
  • \$\begingroup\$ I know home use body weight balance has 4 HX711 pressure sensors on its four corners. Perhaps we can put say, 20 HX711s inside the bag, and use WiFi controller ESP32 to send report to Tarzan and Mike Tyson youtube.com/watch?v=JvdJ9cfJAfI. \$\endgroup\$ – tlfong01 Feb 12 at 5:49
  • 1
    \$\begingroup\$ I'm not sure exactly what they use, but I built my own punchbag project for my boxing training. I used an FSR (force sensitive resistor) underneath a few layers of padding. That worked well for me and could work in your project \$\endgroup\$ – MCG Feb 12 at 8:00
6
\$\begingroup\$

I do not know how it is done in arcades, but there are several ways of doing this.

  • A hollow gas filled interior and a pressure sensor to record the pressure change profile when struck
  • An accelerometer (probably the easiest) to record the acceleration profile for a known mass
\$\endgroup\$
2
  • \$\begingroup\$ Given the fact that the device is intended to be wall-mounted, the gas-filled interior is a good idea. I have to figure out how to stuff the exterior to give it a punch-bag feel. \$\endgroup\$ – hegemon8 Feb 12 at 12:02
  • 1
    \$\begingroup\$ The gas cylinder idea is very nice. It also doubles as a dampener! \$\endgroup\$ – Lorenzo Marcantonio Feb 12 at 16:57
4
\$\begingroup\$

Well, the really low tech way to do this is to use a seismic mass (i.e. a chunk of iron:D) attached to a spring or a pendulum and some kind of sensor to detect the movement. Since we are literally punching the device you need something sturdy.

You can also use a load cell if it's fast enough. Most standard cell are quite slow and may damp the peak.

Really, any way to turn a mechanical movement into a signal can be useful. Accelerometers, even simple potentiometers can do the job. MEMS device as suggested in the comments are game too, but maybe they are too 'refined' for the application.

\$\endgroup\$
1
\$\begingroup\$

The problem of measuring force of a punch is more complicated than it seems.

The first challenge is to figure out what variable you are trying to measure. You could measure velocity, acceleration, pressure, impulse, etc.

Pressure is force over area. If I concentrate the force of my body weight into a small area like my top two knuckles and punch something, there will be a large pressure at that point. If the force is spread over 4 knuckles and the front of my fingers, the pressure will be lower since the area is larger. Imagine hitting a single rib with one knuckle or hitting a hard skull with an entire fist. The pressure on both the hand and the target will be very different.

But with respect to boxing, pressure doesn't tell you the entire story. For boxing it is more useful to measure impulse or change of momentum. That will you give a better read of knock out power.

Check out "Fight Like a Physicist: The Incredible Science Behind Martial Arts" Book by Jason Thalken. This book goes pretty deep into the subject of knockouts.

The machines in arcades usually have a punching bag on hinge. When you punch the bag, the bag accelerates until slams into a hard stop.

There a few ways you could approach this problem. You could measure the change in velocity of the bag and calculate change in momentum. You could measure the acceleration of the bag directly using accelerators. You could use a compressible material and measure the deflection. You could also measure the force exerted on the hard stop by the bag. You could measure force over area to determine pressure. It largely depends on which variable you decide to investigate.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.