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leggedrobotics / raisimLib

RAISIM, A PHYSICS ENGINE FOR ROBOTICS AND AI RESEARCH
http://www.raisim.com
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jointState(18) has 18 datas,how to define it . why we define jointPgain.tail(12) #15

Closed yonchien closed 5 years ago

yonchien commented 5 years ago

jointState(18) has 18 datas,how to define it . why we define jointPgain.tail(12) , how to define the others

jhwangbo commented 5 years ago

yonchien, please write a complete question so that others can understand what you mean. I understand your question but other users cant. I guess you mean why anymal example has 18 dof and why we only define the last 12 elements in pd gains.

For the first question, please refer to the manual. It explains how a generalized coordinate is defined for articulated systems. We only define the last 12 elements of pd gains because they are joints. The first 6 are related to the floating body. And we dont actuate the body. For floating base systems, first 6 elements in p,d gains are always ignored.

yonchien commented 5 years ago

the manual explains a generalized coordinate position and quaternion , it has 7 elemnets not 6 865BA01E-3B1D-4955-BFEB-B9BB908707B4

jhwangbo commented 5 years ago

Dof is not equal to the dimension of the generalized coordinate. Anymal has 18 dofs, and a 19-dimensional generalized coordinate

yonchien commented 5 years ago

what the jointNominalConfig means? How to define the friction coefficient of the ground？

jhwangbo commented 5 years ago

nominal configuration of the joints for ANYmal. That's the generalized coordinate of ANYmal when we turn on ANYmal and the configuration where we start our simulation.