Programming 3 degrees of freedom into the knee

[Jim Darke]

My name is Jim Darke and I work at the Human Motion Biomechanics Lab at Cal Poly. Recently my team and I programmed 2 new degrees of freedom into the knee of the 3d_gaitmodel_Prescribed_Patella model that is available in Opensim. These new degrees of freedom account for abduction/adduction and internal/external rotation of the knee.

Has anyone done something similar to this and know of any complications that could arise from doing this? One thing we have noticed is that the Opensim model does not have any tendons or soft tissue programmed in it that would control abduction/adduciton and internal/external rotation of the knee. Will this effect our model kinematics?

Thanks,
Jim

[jimmy d]

Hi Jim,

The biggest issue you will face is cross-talk from the flexion axis. You will also have to have a method for setting the initial rotation/adduction values during scaling. Those coordinates have very small values and are very sensitive and generally are not reliable measures of REAL values, hence why they are not included in the Model by default.

When doing motion analysis, you are capturing the net effect of all structures in the body. Since the motion is tracked from experimental data, there is no 'control' needed by ligaments, etc. If you were interested in their values, you could then add them to the model and do computations to get their contribution to motion.

Goodluck,
-James

[Julian Atkinson]

My name is Jim Darke and I work at the Human Motion Biomechanics Lab at Cal Poly. Recently my team and I programmed 2 new degrees of freedom into the knee of the 3d_gaitmodel_Prescribed_Patella model that is available in Opensim. These new degrees of freedom account for abduction/adduction and internal/external rotation of the knee.

Has anyone done something similar to this and know of any complications that could arise from doing this? One thing we have noticed is that the Opensim model does not have any tendons or soft tissue programmed in it that would control abduction/adduciton and internal/external rotation of the knee. Will this effect our model kinematics?

Thanks,
Jim

Hi there

Is there any update on the success of the 3 degree of motion model on the knee?

Regards
Julian

[Namrata Kaundal]

In attempting to program a revolute-coordinate (arm-and-elbow) robot directly from data about required end-effector positions expressed in spatial (x, y, z) coordinates, users of smaller ‘teaching’ robots face a lack of information about the necessary transformation from spatial coordinates to joint coordinates. The purpose of this paper is to provide that information in the form of simplified trigonometrical expressions which, while not representing a completely general solution to all possible cases, nevertheless provide the solution for a large class of tasks to which small robots are commonly applied. Application of the algorithm to a Smart Arms 6E robot is described, and a summary of the interfacing and programming requirements is included.