How can I choose spring stiffness and damping coefficient of the motor for walking robot?

walking robot

[Walter Roberson]

Who is sebastian ?

[madhan ravi]

@sir Walter my thoughts exactly ?

[Rik]

@sameh: Have a read here (or here for more general advice) and here. It will greatly improve your chances of getting an answer.

@Walter: are you knighted?

[Walter Roberson]

@Rik: no, I am Canadian, and cannot accept "foreign honours" (in particular, cannot accept Knighthood), not even from the UK.

[sameh ibrahim]

Walter Roberson, how i can choice spring stiffness and damping coefficient of the motor for walking robot?

[Star Strider]

‘Sebastian’ likely refers to: Sebastian Castro.

[sameh ibrahim]

yes how can i mail him please @star strider

[Image Analyst]

Since he works at the Mathworks, you can likely call him on the phone or use his mathworks email address, which I think is the same for all Mathworks employees: [e-mail]

[madhan ravi]

+1 @sir Image Analyst and @star rider

[Sebastian Castro]

Well... this is the 5th place I found this same question, after YouTube, Twitter, our [e-mail] mailing list, and my personal email. This explains the email part, haha.

Confirming I've replied to Sameh via email.

- Sebastian

Answer 1

[Sebastian Castro]

The email answer here for reference, in case others run into this question:

There are actually two sources of stiffness and damping in such a model.

1. The mechanical joint -- In the picture you attached, this would represent the physical stiffness and damping of the robot's mechanical assembly. For example, if there is friction in the joint or you place a spring to make the articulation compliant, this is part of your robot's design.

2. The actuator -- In addition to the joint, the motor has its own dynamic characteristics (resistance, inductivity, inertia, damping, etc.). Typically, motors do not have any springs in them so stiffness is zero. For the damping, you can set this by looking at datasheets or collecting experimental data and estimating the parameter.

With datasheet, you can use parameters like the stall torque and no-load speed to estimate damping from the torque-speed curve.

• Datasheet for Dynamixel: http://support.robotis.com/en/product/actuator/dynamixel/ax_series/dxl_ax_actuator.htm
• From a picture like the one below, this would be the slope of the line (Torque/Speed): https://www.groschopp.com/start-vs-stall-torque-brushed-brushless-dc-motors/

Using experimental data, you can also estimate parameters

• With analytical methods: https://www.hindawi.com/journals/mse/2012/189757/
• With optimization: https://www.mathworks.com/videos/estimating-dc-motor-parameters-97057.html

- Sebastian

[superman]

Thanks for sharing. However, how to set the damping coefficient of joint?

Could you share an example? Thanks again.

[Rabé Andersson]

Hi Superman,

Have you solved the issue?

Mail me if you want to get a help : []@yahoo.com

Best regards