Home Reaching task with force channel
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  • Create Date August 24, 2023
  • Last Updated August 24, 2023

Reaching task with force channel

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.
Note 3: The update I have just added allows the task to be run on the Exoskeleton (not the classic). I have also done some further clean up.

This is a sample task that implements a force channel similar to what is described here:
Scheidt et al. (2000), Persistence of Motor Adaptation During Constrained, Multi-Joint, Arm Movements. J. Neurophys., 84(2): 853-862 (https://www.physiology.org/doi/full/10.1152/jn.2000.84.2.853)
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.

Please note that this task is only possible to run on the Kinarm End-Point Lab and new PN 13568 or later Kinarm Exoskeleton lab. The KINARM Exoskeleton Classic Lab and KINARM NHP Labs do not provide appropriate stiffness to make a force channel useful.

Task last tested in Dexterit-E 3.10 and MATLAB 2015a.

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