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Author Topic: Parts/Materials needed for Force Control  (Read 644 times)

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Offline TheBokserTopic starter

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Parts/Materials needed for Force Control
« on: January 26, 2014, 08:54:28 PM »
My team would like to build a robot that utilizes force control. However, we are not sure which materials to use. We would prefer to use high speed linear actuators or hydraulic pistons with at least 150 lbs of moving force. It should be around 10" long with a stroke of at least 6".

I don't expect any of you to find a motor of these exact specifications for me, I just wish to know what kind of force controller is needed for this and where I can find it. I've been searching the internet but the seller's specifications on  motors, sensors and controllers have been very confusing. Sorry if I seem like a complete ignoramus.

Offline jwatte

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Re: Parts/Materials needed for Force Control
« Reply #1 on: January 27, 2014, 10:22:14 AM »
There is one key piece of information missing from your requirements: How fast do you need to actuate with the given force?
Applying 150N at 1 mm/s is very different from applying 150N at 100 mm/s!

Offline waltr

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Re: Parts/Materials needed for Force Control
« Reply #2 on: January 27, 2014, 11:22:34 AM »
The first step if you want a control feedback is how are you going to sense (speed, position, Force, etc). So, if you want to control the Force applied then you must find a way to measure (sense) this force.
There are direct and indirect methods.
Direct may be a 'force' sensor (like a scale to measure weight) and can be done with various methods.
In-direct would be measuring some factor that is driving the actuator. Like current for a DC motor or cylinder pressure for hydraulics.
Your team has a lot of research to do before you can make any decision. Has your team an adviser to discuss options and budget?

Offline TheBokserTopic starter

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Re: Parts/Materials needed for Force Control
« Reply #3 on: January 27, 2014, 12:16:34 PM »
There is one key piece of information missing from your requirements: How fast do you need to actuate with the given force?
Applying 150N at 1 mm/s is very different from applying 150N at 100 mm/s!

I would say that it is closer to 100 mm/s. Since that speed with that force is unlikely with a single linear actuator, two high speed linear actuators working together is definitely also an option.

Offline TheBokserTopic starter

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Re: Parts/Materials needed for Force Control
« Reply #4 on: January 27, 2014, 12:35:39 PM »
The first step if you want a control feedback is how are you going to sense (speed, position, Force, etc). So, if you want to control the Force applied then you must find a way to measure (sense) this force.
There are direct and indirect methods.
Direct may be a 'force' sensor (like a scale to measure weight) and can be done with various methods.
In-direct would be measuring some factor that is driving the actuator. Like current for a DC motor or cylinder pressure for hydraulics.
Your team has a lot of research to do before you can make any decision. Has your team an adviser to discuss options and budget?
We probably need a direct force sensor, as the actuator will be interacting with outside forces.

We do have a member managing budget and funding; however his level of expertise is not much more than mine mechanics-wise. Before this we've only really built RC robots with little autonomous capability.

Offline TheBokserTopic starter

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Re: Parts/Materials needed for Force Control
« Reply #5 on: January 27, 2014, 01:07:05 PM »
This is early on in the design process and we are planning on receiving funding from local companies, so there is not a fixed budget yet. We do expect this project's cost to be at least in the four digits.

Offline bdeuell

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Re: Parts/Materials needed for Force Control
« Reply #6 on: January 28, 2014, 10:45:59 AM »
two high speed linear actuators working together is definitely also an option.

A note of caution is that while using two actuators in parallel can be done (and with great success) special consideration must be taken to properly design the system. Any two actuators will have some degree of difference between them and as a result they will not behave identically. To ensure they operate in unison you can use feedback control systems or design the mechanics to robustly link them together. While I suspect that you wouldn't need two hydraulic cylinders this issue is very common in hydraulics and I have seen some elaborate systems conceived to try and solve the problem.

 


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