Feeding knees angle to the walking robot

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?

Answer 1

[Sebastian Castro]

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

[Sizhe An]

Hi Sebastian,

Thank a lot for your impressive video. That's really a great work.

And thanks to your quick reponse, I was able to import the real knee data to the robot.

However, I had an additional question:

Are we able to measure the stride length or step length of the robot? If possible, how can we do that?

Thank you very much!

[Sizhe An]

Hi sebastian,

Also, when I tried to increase the length of legs and made it thicker like real human-being, the robot just sunk under the world plane. It seems something to do with the density but even I decrease the density of the robot to make it lighter, it also sunk.

How can I solve this problem?

Thanks!

[Sizhe An]

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]

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]

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!!