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Force Channel

Posted on Aug 6, 2020

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.

This is compiled for Dexterit-E 3.6 and MATLAB 2013a.

Please note that this task is only possible to run on the Kinarm EP and Exoskeleton (not classic!) lab. The Kinarm Exoskeleton Classic Lab and Kinarm NHP Labs do not provide appropriate stiffness to make a force channel useful.

KINVASION!

Posted on Aug 6, 2020

This is a task written by Ethan Heming, a Ph.D. canditate in Steve Scott’s lab. Kinarm would like to thank Ethan for allowing us to post his task! This is easily the most sophisticated task program I have seen. This game really stretches what can be done with Simulink, Stateflow and indeed Dexterit-E.

This task requires a bilateral Kinarm End-Point robot with force-torque sensors.

The object of this game is to destroy as many enemies as possible on each level. You control a ship represented by a green bar between your hands. The thickness of this line shows your ship’s health. Any enemies or enemy shots that hit this bar reduce your health and the game ends when ship has no health left. If you get hit there will be a haptic response (i.e. you will feel it)! At each handle you have a “gun” that fire perpendicular to the green health bar. They are fired by ’tilting’ robot handle (applying a pitch or roll torque). The farther apart your hands are, the faster your guns recharge, but the larger a target you present to enemies.

At the start of each level you can buy upgrades to your guns and shields by moving the cursor to the desired selection and torquing on the handle. There are also addition options such as auto-cannon or bombs. During a level you can catch coins to earn money to buy things. You also earn coins by killing enemy ships.

Some extra special features are:

If you have an End-Point robot with force plates then stomping on the plate will release a bomb if you have purchased that upgrade.

I have compiled this task for Dexterit-E 3.8 and MATLAB 2015a.

Have fun!

Image Display Spring

Posted on Aug 6, 2020

This isn’t really a task per se, it’s really just a demonstration of how to dynamically manipulate an image and use forces. When you start the task an image of a spring will be displayed between the hands. As you try to move your hands apart or together you will feel a spring trying to hold you at one distance. The task will work on a Kinarm Exoskeleton or EP robot.

The task was built for Dexterit-E 3.5 and MATLAB 2013a.

Note: This is a much improved version of the task. This has been cleaned up substantially since the first version.

End-Point Perturbation

Posted on Jul 14, 2020

This task is a simple reaching task where the subject is perturbed during the reach. The perturbations will only work for a Kinarm EP, though this could easily be modified for a Kinarm Exoskeleton.

The attached model was compiled using MATLAB 2013a for Dexterit-E 3.5.