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Thread: Permobil C300 with Total Control Head Array

  1. #1
    Senior Member SCI_OTR's Avatar
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    Permobil C300 with Total Control Head Array

    As 2012 comes to a close, I will remember it as the year of my most-challenging cases. As emergency medicine and trauma care have evolved, there are a small, but growing number of individuals who survive very high level injuries. For a variety of reasons, some may be unable to use traditional alternative driving systems such as a sip-n-puff or head array. I have worked with a number of individuals who fall into this category during the past 3 months.

    For me, the most innovative product to hit the market this year has been Permobil's Total Control Head Array. I've spent quite a few hours with a prototype figuring out unique solutions for some very, very, challenging cases.

    This C300 is the first powerchair I've spec'd to be equipped with the production version. It is being used by a high level quad who has very limited ability to turn his head due to the hardware that was surgically-implanted to stabilize his spine...






    Before I discuss the actual head array, I'll briefly cover the other significant features and custom configuration options that can be found on this chair.



    1) HMC Compact Joystick Lite on Stealth Gatlin Mount. This currently functions as a forward mounted attendant control to allow a caregiver to be able to "pull" the C300 through a narrow doorway or into a modified van. This individual does have some movement in his right upper extremity, so it is conceivable he may be able to use this to drive the chair at some point in the future. Because of this, it was mounted so that the top of the joystick handle is roughly even with the surface of the arm trough.

    2) Motion Concepts Ergo Arm Troughs/Hand Pads attached using the "direct mount" technique. While Permobil offers an optional "Arm Trough Adapter" to install arm troughs on their chairs, I have found that they are not long enough to properly mount the arm troughs in the optimal location and that even minor adjustments are time consuming. Attaching hardware used to mount displays, joysticks, and routing cables is also rather tedious. I've found that it is much easier to order the standard 4x16 Corpus 3G arm pads, remove the padded insert, and mount the arm trough directly to the base of the arm pad.

    3) Custom Elbow Stops. Whenever I do something custom that I anticipate I will do again in the future, I try to work with the manufacturer so that it gets done at the time the chair is being built. Permobil was already doing these custom elbow stops as a custom config option with their standard arm pads. They were willing to revise this option slightly to make them compatible with my "direct mount technique". They do an excellent job of keeping upper extremities in place when the user tilts the chair.

    4) 18" Wide Back Cushion Installed on 16" Wide Corpus 3G Ergo Back. I've been doing this "+2" option for over a year now to add additional contour to the Permobil Corpus Back to increase the amount of lateral support without having to resort to bolt on laterals.

    5) Custom "PermoFix" Lower Switch Arm. Normally, the lower switch arm hardware on the new head array is a longer version of the upper arm (see next post). Because this individual needs more-precise positioning of their mode switch, Permobil provided a custom lower arm using their PermoFix hardware. I was able to fabricate a flexible custom mount out of Loc-Line for the Microlight switch. The rod between the PermoFix joint and Loc-Line needs to be threaded at one end in order to attach the first segment of Loc-Line. On future versions, I will be using one of the many TiLite caster axles that have accumulated in our store room over the years after being replaced with FrogLegs "wide axle kits" on our TiLite chairs.

    6) Stealth TWB480 Headrest Hardware with Flip Down Mount.

    7) 15" UniTrack Accessory Rail. Used to attach the power seating switch box and attendant control.

    8) Retractable Attendant Control. Includes extra linkage to allow the attendant control to be stowed as close to the backrest as possible when not in use. The left/right axis is always inverted so that the caregiver is able to walk in the same direction they move the joystick (more intuitive).

    To truly appreciate why this head array is so innovative, one must understand some of the technical challenges of installing other manufacturer's head arrays on Permobil's Corpus 3G seating system. Here is a pic of a C500 from earlier this year that has an ASL proximity head array installed on it...



    That C500 took hours to configure because there was no place to easily mount the extra interface box on the backrest. It had to be mounted exactly where its at using custom hardware so that it would be offset from the backrest. Otherwise, it would come in contact with the sheer plate when the backrest was reclined. Note that there is also a significant amount of cable that had to be bundled/routed, and that the connectors for the proximity sensors use a proprietary 3 pin design.

    Aesthetics aside, the true beauty of the Total Control Head Array lies in its occipital unit. The Occipital Unit is the brains of the head array and it is a brain with a pretty high IQ. Instead of having a separate switch interface box that needs to be mounted somewhere else on the powerchair, the switch interface is incorporated into the occipital unit itself via a panel of input jacks on the back. Proximity sensors are electronic switches which require a power source in order to work. Instead of developing a proprietary connector, Permobil chose to use the second ring of a 1/8" (3.5mm) stereo plug for the sensor's power supply. These two design features alone allow for the entire head array to be contained within the headrest assembly with a minimal amount of cable. The head array can be easily connected to the powerchair using a single harness with 9 pin connector that plugs into the Omni display at the front of the armrest.



    But it is another feature of this design that makes it truly innovative. Because they went with a standard 1/8" (3.5mm) stereo plug for their proximity sensors, they were able to give the input jacks on the back "plug & play" capability. The decision to go with a standard input jack means that any mechanical switch which has a 1/8" mono plug can be used instead of a proximity sensor. When the occipital unit detects a stereo plug, it registers it as a proximity sensor. If it detects a mono plug, it registers it as a mechanical switch. The ability to mix and match switches easily gives it unprecedented flexibility in how it can be configured.

    I'll discuss these in the next post.
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    Last edited by SCI_OTR; 12-31-2012 at 02:59 PM.


  2. #2
    Senior Member SCI_OTR's Avatar
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    "Hybrid" Alternative Driving Systems

    For those who have high level SCI's or those with severe loss of function in multiple areas due to ALS, MS, or polytrauma, a single alternative driving system may not be enough.

    True sip-n-puff systems require the user to be able to consistently provide two types of sips, two type of puffs, and the ability to quickly master latched driving (a concept similar to cruise control where the chair will continue forward at a given speed until the user provides a command to stop). Traditional head arrays require sufficient cervical range of motion to be able to activate the lateral proximity sensors for steering and enough strength in neck muscles to be able to activate the sensor for forward/reverse in the occipital pad.

    For that subset of users who can not use those types of systems, the Total Control switch interface provides the capability to combine characteristics of more than one type of system to allow essential functions to be matched to the specific abilities of the user. I refer to these as Hybrid Alternative Driving Systems.

    A "common" example of a Hybrid Alternative Driving System is a sip-n-puff head array. Back in 2009, I posted a thread about this TDX SR which was equipped with an ASL109 Stealth Sip-n-Puff Head Array. This was a dedicated system which incorporated the sip-n-puff input into the ASL interface box that was mounted on the back of the chair. It couldn't be used as either a pure sip-n-puff system nor could it be used as a traditional proximity head array.

    The Permobil Total Control Head Array can be easily converted to a sip-n-puff head array by adding a basic sip-n-puff switch module like the one made by Saje Technology. This particular unit has an MSRP of less than $200 and it is compact enough to fit between the upper switch arms on the head array...



    The combination of the Permobil head array, Saje sip-n-puff switch, and P&G R-net Omni display provides the ability to install a dedicated sip-n-puff system, a traditional proximity head array, and a sip-n-puff head array on a single chair in less than 10 minutes. Furthermore, the switch interface on the occipital pad provides the flexibility to incorporate other types of mechanical switches to take advantage of any functional movements that might exist in one or more extremities. It is ironic that the proximity switches in the occipital pad itself are not even used in this type of application.

    Here is an example where I had to think a little bit more "out of the box". The end user was unable to turn his head to the right, had just enough oral motor function to do a soft sip and a soft puff, and could turn their head slightly to the left. I came up with this configuration which locates everything on the left (moving left to turn right is a strange experience).



    It turned out that it didn't work for him. Failure? Not exactly, I eventually came out with a variation of that configuration that he could use successfully. Instead of steering using the switches, he uses the sip-n-puff to steer and a Tash Mini Cup switch for forward/reverse.



    Ironically, no proximity sensors were even used in the final configuration. Still, it would not have been possible for this individual to become a driver had this product not been available (or should I say a pre-production prototype). For the first time, it became possible for me to come up with a very specific configuration for the user, find out if it was going to work, and be able to quickly reconfigure the system to try something else if it didn't.

    The freedom to have multiple failures led to one of my greatest success stories.
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    Last edited by SCI_OTR; 01-01-2013 at 02:14 PM.


  3. #3
    Thanks for sharing. It's great to know that technology has come a long way to enable people with the severest impairments and people like you who can put it all together to make it work.
    C5-C6 ASIA C - October 15, 1984
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  4. #4
    Senior Member SCI_OTR's Avatar
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    I should note that it is possible to configure hybrid alternative driving systems using other manufacturer's products, it just technically more-challenging.

    Additionally, while Permobil sells this head array for their products, it would probably work with Quantum's Q-Logic display or any display module that uses a standard 9 pin input.


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