How do I create a force channel?

Force channel demo   Submitted by dmclean on Fri, 12/16/2011 - 22:43 Forums:

• Task Library

Note: This task has been updated and cleaned up significantly from the first version. Note 2: I have just updated this again so that there are different force values applied for primary vs. secondary encoder systems.   This is a sample task that implements a force channel similar to what is described here:

http://jn.physiology.org/content/84/2/853.full.pdf

This sample is just a modified reaching task that implements a force channel between the reaching targets. The supplied protocol has 8 targets 10cm from the center. The configurable parameters are:

• Channel width (width over which there is no force, may be zero)
• Wall width (the width of the virtual wall that will push you back to center)
• Wall stiffness
• Viscosity (viscous force perpendicular to the channel, this is required to keep things stable).

  Some other key concepts here are:  

• The force channel is ramped up over 1.5s once the destination target is turned on. This stops a potential violent jerk into the channel.
• The forces are ramped down over the last 25% of the wall's width.
• If you break out of the channel then the forces are all off until you re-enter the channel.

This is compiled for Dexterit-E 3.3 and matlab 2010a.

Please note that this task is only possible to do on the KINARM EP lab. The KINARM Exoskeleton Lab and KINARM NHP Labs do not provide appropriate stiffness to make a force channel useful.

Duncan Please download the Task from the Sample Custom Tasks.