Urgent: IC controlled Knees- Due for an Academy discussion?
Edsko Hekman
Description
Collection
Title:
Urgent: IC controlled Knees- Due for an Academy discussion?
Creator:
Edsko Hekman
Date:
11/6/2000
Text:
Hello all,
Interesting questions from Mark Benviste. Being a (bio-)mechanical engineer
I have a hunch as to the answer to question 4.
Firstly, there is less room in a multi-axis hinge for placement of extra
components like links to a controller. The controller can not be placed
just anywhere for proper functioning. Simultaneously the strenght and
stability of the hinge (e.g. avoidance of free play between links) can not
be compromised by insertion of a controller.
Secondly, kinematically the behaviour of a single-axis knee joint is much
simpler than the behaviour of a multi-axis joint. The instantaneous moment
of rotation of a multi-axis joint moves during flexion. Also the controller
usually acts on one of the links or one of the axes, but not directly
between lower and uppr section of the joint. Thise two facts cause
calculation of desired knee moment and accompanying desired controller
force to be relatively complex and time-consuming (though not unfeasible).
This has implications for IC-programming: more complex kinematics, and
increased time lag in the control loop which needs to be taken into account.
I realise that the first disadvantage mentioned above also holds for
'conventional' hydraulically controlled multi-axis knee joints. So I think
that the second reason is more important. I therefore suspect that the
reason why current IC-controlled joints are uni-axial is technically
inspired rather than functionally.
Regards,
Edsko Hekman
>4) With all the purported advantages of multi axis technology, why does
>industry continue to develop expensive and more technically involved
>single axis knees?
...........................................................
.Edsko Hekman MSc .
.Laboratory of Biomechanical Engineering .
.Twente University .
.PO box 217 tel. 31-53-4893173 .
.7500AE Enschede fax. 31-53-4893471 .
.The Netherlands .
.e-mail <Email Address Redacted> .
...........................................................
Interesting questions from Mark Benviste. Being a (bio-)mechanical engineer
I have a hunch as to the answer to question 4.
Firstly, there is less room in a multi-axis hinge for placement of extra
components like links to a controller. The controller can not be placed
just anywhere for proper functioning. Simultaneously the strenght and
stability of the hinge (e.g. avoidance of free play between links) can not
be compromised by insertion of a controller.
Secondly, kinematically the behaviour of a single-axis knee joint is much
simpler than the behaviour of a multi-axis joint. The instantaneous moment
of rotation of a multi-axis joint moves during flexion. Also the controller
usually acts on one of the links or one of the axes, but not directly
between lower and uppr section of the joint. Thise two facts cause
calculation of desired knee moment and accompanying desired controller
force to be relatively complex and time-consuming (though not unfeasible).
This has implications for IC-programming: more complex kinematics, and
increased time lag in the control loop which needs to be taken into account.
I realise that the first disadvantage mentioned above also holds for
'conventional' hydraulically controlled multi-axis knee joints. So I think
that the second reason is more important. I therefore suspect that the
reason why current IC-controlled joints are uni-axial is technically
inspired rather than functionally.
Regards,
Edsko Hekman
>4) With all the purported advantages of multi axis technology, why does
>industry continue to develop expensive and more technically involved
>single axis knees?
...........................................................
.Edsko Hekman MSc .
.Laboratory of Biomechanical Engineering .
.Twente University .
.PO box 217 tel. 31-53-4893173 .
.7500AE Enschede fax. 31-53-4893471 .
.The Netherlands .
.e-mail <Email Address Redacted> .
...........................................................
Citation
Edsko Hekman, “Urgent: IC controlled Knees- Due for an Academy discussion?,” Digital Resource Foundation for Orthotics and Prosthetics, accessed November 28, 2024, https://library.drfop.org/items/show/215381.
