Feeding knees angle to the walking robot

Asked by Sizhe An on 30 Jun 2019

Latest activity Commented on by Sizhe An on 9 Aug 2019 at 23:33

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Hi,

I'm doing gait analysis for human-being.

I watched a great video about how to build a walking robot and observe many metrics when the robot walking in this following link:https://www.mathworks.com/videos/matlab-and-simulink-robotics-arena-walking-robots-part-1-modeling-and-simulation-1505941655157.html

However, my target is in an opposite aspect. I recored the real knees degree data when people walking. Now I want to feed these degree data into the robot then observe how the robot walks. Is this possible?

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Simscape Multibody

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Answer by Sebastian Castro on 1 Jul 2019

Accepted Answer

Thanks for tagging this post with roboticsarena so we got that notification! Much appreciated.

In Simscape Multibody, you can choose to actuate joints either with torques or with motion profiles. I am guessing you want to put in a motion profile from the real knee angle data. See the "Motion Input" section below.

https://www.mathworks.com/help/physmod/sm/ug/joint-actuation.html

Or, this example:

https://www.mathworks.com/help/physmod/sm/ug/prescribe-joint-motion-in-four-bar-model.html

- Sebastian

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Sizhe An on 3 Jul 2019

I found some other parameters seem related to my issue. Like contact_stiffness, contact_damping, contact_point_radius and so on...

How can I tune these parameters? Is there a explanation regarding them?

Sebastian Castro on 4 Jul 2019

That's right. The heavier the robot, the higher the stiffness needs to be... else it might fall through.

You should pick something big enough to hold the weight at a specified displacement (much smaller than the thickness of the foot).

Force = Stiffness*Displacement

For more information, see here:

https://blogs.mathworks.com/racing-lounge/2017/09/12/introduction-to-contact-modeling/

Sizhe An on 9 Aug 2019 at 23:33

one_hip_leg.slx

Hi Sebastian,

I kind of modify the four bar through revolute joints to a easy robotic lower lambs. And I give the input angles to the leg then observe how it works. It turns out it works very well and now I want to add one more legs but I got stuck.

As shown in Fig.1, l1 is the hip and l2 is the leg. This is exactly the model I wanna build. α and β I got from sensors, which is the input. I wanna observe how l1 and l2 rotates when α, β is changing.

However, as shown in Fig.2, I can only build one hip and leg here. I have no idea how to add another lamb on the same pivot mount. I have a look in https://ww2.mathworks.cn/help/physmod/sm/ug/model-four-bar.html but it doesn't help much...

My design file is attached. Can you please give me an idea how I can make the model I want?

Thank you very much!!

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Simscape Multibody

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