Author Topic: Sensors for exoskeleton  (Read 665 times)

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Offline nikola.efremovTopic starter

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Sensors for exoskeleton
« on: September 24, 2013, 04:57:38 AM »
Hello guys,

I'm really new to this, but I'm part of a team that is trying to built an exoskeleton. The initial prototype will be pre-programmed to walk and it should support below-pelvis disabled people, so that will include legs only.

I need to choose sensors for the task, we are planning a very basic construction with accelerometers and gyroscopes. Can you please go through the pros and cons of both and suggest which ones to use and where?

Thank you!

Kind Regards,
Nikola

Offline vipulan12

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Re: Sensors for exoskeleton
« Reply #1 on: September 24, 2013, 02:25:24 PM »
well if you doing something like HAL you dont really need those since the exoskeleton would make movement based on the data or the muscle movements it detects
https://www.youtube.com/results?search_query=hal+exoskeleton&oq=hal+exoskeleton&gs_l=youtube.3...41540.50044.0.50225.22.16.6.0.0.1.273.2322.5j1j9.15.0...0.0...1ac.1.11.youtube.VpSXSpuzJbA

if you were making a biped robot you would probably need those
unless you plan on making the exoskeleton do all the walking then you would need them

Offline nikola.efremovTopic starter

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Re: Sensors for exoskeleton
« Reply #2 on: September 25, 2013, 02:51:24 AM »
Hello,

Thanks for the response.

I took a look at HAl and a few others beforehand. However, he exoskeleton we are doing will be targeted for paraplegics and therefore no muscle movement can be detected. We will need some kind of a controller to move the exoskeleton later on, but as I said the initial prototype will just be pre-programmed to travel X distance.

Therefore I still think I will need gyros and accelerometers as I see it, but I need more details on the pros and cons of each (should I use only gyros/accelerometers or a combination of both) and where to place them for maximum effect in this case.

Offline vipulan12

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Re: Sensors for exoskeleton
« Reply #3 on: September 28, 2013, 08:27:20 AM »
well you would need both since accelerometers  measure acceleration both static and dynamic but can measure orientation this is why gyros are needed  since they measure angular or rotational velocity which is also key in stabilizing
which is why you need an IMU (inertial measurement unit)
where is would be places shouldn't matter(not 100% sure) but placing it at the center of gravity would be best
look at this the tutorials for spark fun:
https://www.sparkfun.com/pages/accel_gyro_guide

but since gyros have a tendency to drift a magnetometer  would be needed  to 9 degrees
« Last Edit: September 28, 2013, 12:00:10 PM by vipulan12 »

Offline jwatte

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Re: Sensors for exoskeleton
« Reply #4 on: September 28, 2013, 11:55:21 PM »
Generally, you want both a gyroscope and an accelerometer, as they measure different things.
There are lots of affordable, high-quality solutions on the market now, because of MEMS sensing technology where you basically build the sensors as part of an IC.
You may even get a 9-DOF system (3 DOF gyro, 3 DOF accel, 3 DOF compass) for the same price. Although I think the compass wouldn't be that useful for your application, and would be confused if you have lots of steel/motors in your device.

Offline nikola.efremovTopic starter

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Re: Sensors for exoskeleton
« Reply #5 on: October 02, 2013, 04:54:28 AM »
Thank you for your responses, guys.

I didn't check the topic for a few days - I already ordered 3-axis digital accelerometers. I think about placing a gyro and accelerometer on the waist, and on each hip and under the calf. Do you think that might be an overkill or do I need more (say on the metatarsus)?


Right now I'm focused on getting free sampling for the gyros. I tried Analog Devices but to no avail as of yet, do any of you have suggestions on the topic?

Regards,
N

 


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