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Experiments

Experiments with ette…

“ette is the first of its kind finger-tracking controller. Powered by TG0’s patented technology, etee allows user to control VR without gloves, camera, or other encumbering equipment. Etee is lightweight and intuitive to use. The controller has a battery life of 8 hours that enables the user hours of time to build, explore and immerse themselves into the world of VR”

Product Description, TG0

After reading Tony’s (a.k.a Skarredghost’s) recent review of the ette controllers I was intrigued and wanted to know more – especially in light of some ergonomic concerns he raised in his article:

This was a comment I posted on his blog post after reading the review:

“Hi Tony, Great review, very detailed. The ergonomics aspect is an interesting problem, due to wide variation in hand sizing. Typically we have 3 blunt measurements:

1. length: measured from tip of the longest finger to crease under the palm.
2. breadth: measured across widest area where fingers join the palm.
3. circumference: measured around the palm of the dominant hand below the knuckles excluding the thumb.

Creating a gripped or held object to cater for the wide variation is an interesting challenge.

This challenge effect many objects whether pistol grip on weapon, household item like cutlery or cooking tool, and of course VR controller; the Valve Index controllers (Knuckles) have the ability to use clip-on Palm boosters.

I’d be interested to try the TG0 Etee controller, without getting my hands into them it’s impossible to make any valid judgement; however some physical adjustment within their structure (a clip on spacer or sliding component with locking) may be beneficial to optimise the fitting for different hands.” 

Happy XR! Cheers. Rob Cole.


Tony introduced me to TG0 who are also based in London, UK. They quickly arranged a courier delivery and within a couple of days a small box containing an Etee dev kit had arrived; many thanks to TG0.

Packaging was neat and minimalist, although I must admit I damaged the cardboard box trying to remove the controllers as their handles were very firmly wedged into the foam. I resorted to pulling the entire foam slab upwards to release them from the box, which freed the controllers but also separated the adhesive tape holding the box together.

Physical examination

The etee controllers are wonderfully simple, yet very sophisticated in terms of material technology compared to the mechanical switches and sensors we commonly see in motion controllers.

TG0’s “secret sauce” is their patented material technology used to build the sensing strips, which I understand is already used in different commercial applications – this being their first foray into motion controllers for XR.

TG0 list these as the key features of their “Etee” motion controllers:-

-Multi function TG0 thumb-pad technology

-Wireless connection

-5 finger 100 level of sensing

-6hr continue using battery life

-Gesture sensing

-Magic Trackpad with swiping, scroll, rotation and pressure sensing

-Soft silicone shore A 60 touching surface

-Weight: 75g

-Size: L136 x W60 x H30 mm

Despite coming in a little heavier than advertised at 88g vs.75g, a single Etee controller is still considerably lighter than one of my Valve Index controllers which are 197g each.

I’m also using 3D printed Valve Index ‘Palm Booster’ clip-ons, which I have to use to put controls at correct “reach” and to increase controller body “volume” to suit my medium sized hand fit, but this takes a single Index controller up to a weighty 224g.

Releasing the Palm Booster was a smart move by Valve’s designers to widen the range of hand fits possible on a single device, and many Index owners placed orders with 3D printing shops soon after Valve released all the Index mod files for free under the Creative Commons License.

From nearly a year’s experience of using “naked” Index controllers and “Palm Booster” Index controllers, the clip-on added an important tactile enhancement as the additive printing process creates a warmer, more textured surface.

This helped balance the “material mismatch” I’d experienced as a proprioceptive challenge between the soft, warm fabric strap and cold, hard plastic controller body in the weeks following the Index launch.

As well as the weight difference between the Etee and Index controllers, there is a big difference in physical size as can be seen in the side by side image below:

The Valve Index is used for comparison here as its the most advanced VR motion controller currently available to the consumer, whilst Etee offers a new approach to hand input championing a revolutionary material technology and different way of thinking.

Unlike many controllers past and present, Etee lacks physical buttons or triggers, instead providing full finger tracking across a rubberised controller body – an oval shape 26mm deep facing the palm (palmer side) and 32mm wide across the hand, combined with a large tracked thumb pad up top.

The low durometer (60a shore) controller skin has moulded vertical ribs which curve around a glowing status window, giving a soft, tactile feel with a small moulded ridge to separate the index and ring finger.

This moulded ridge protrudes 6mm from the surface, what I took to calling the “index” ridge (not to be confused with Valve Index!) to assist in locating and separating the index and ring fingers.

Controllers are marked “L” (left) and “R” (right) at the top of each handle as they are orientated specifically for each hand.

Perhaps the standout piece of the controllers is a rose gold coloured “finger bar” which provides a stiff brace for a sculpted foam cushion which is glued with adhesive tape to a channel along the inside face of the bar.

This foam bar “sandwiches” the finger against the rubber controller body, effectively capturing Etee to the hands without requiring any adjustable straps or safety lanyards which is a good “quality of life” improvement if regularly putting on and taking off.

This foam cushion is punched through with 8 triangular holes which increases its flexibility, perhaps helping to accommodate larger fingers. The foam is a relatively high density, possibly a requirement to maintain structural integrity as its only 12mm wide and 10mm deep at maximum.

The foam also has a forward extension protruding 9mm at the same vertical height as the “index” ridge on the controller skin, although rotated approximately 30 degrees around a vertical axis to the side of each ridge.

This locates the index finger of each hand and secures firmly in place by encircling that finger, whilst the remaining fingers are left “open” especially the little finger (pinky) which floats about unencumbered.

FITTING NOTES

My first quick setup attempt at fitting Etee was strange, being in a rush I pushed them on horizontally through the finger bar foam, finding a comfortable position across my “middle phalanxes”. I had tried pushing the controllers further up my fingers but found the opening between the body and foam a bit too small, I was concerned to snap or bend the finger bar if I forced them.

They felt odd but seemed to fit in some way, until both Tony and TG0 pointed out from a photo I’d emailed them, that I had them incorrectly fitted! So much for reading the instructions….

The hand anatomy image below shows the names of the 27 different bones that make up each human hand. From this image we can see the Middle Phalanx where I’d incorrectly first fitted them, and the Proximal Phalanx which was the correct location.

Image: Paul Jarrett, Murdoch Orthopaedic Clinic

TG0 advised me to fit by “sliding” the controllers vertically down over stretched hands, aiming for the foam to make contact with the proximal phalanxes of the index, middle and ring fingers. I watched the videos on their website again and it started to make more sense.

I tried fitting them again, and despite being a tight squeeze that felt sure to rip the foam off the finger bar, I finally got them on and gave my fingers a quick outstretched wiggle which felt very liberating as I now had “hands free” controllers firmly clamped in place.

I also found it a lot more comfortable to remove my wedding ring as this was being uncomfortably squashed into my ring finger during the fitting attempts.

SETUP

Setup was very easy with a USB dongle, an email I had earlier received from Tg0 contained a download link for their software.

These dev kit controllers have 3 degrees of freedom (3DoF) tracking like the older Samsung GearVR and Google Daydream headsets and remote controllers.

This means only rotational motion is tracked around a fixed location:- pitch, yaw, and roll, but not able to move forwards, backwards, side to side or up and down.

All contemporary PCVR systems and the Oculus Quest stand-alone use 6 DoF tracking for headsets and controllers; 6DoF allows movement forwards and backwards, up and down, left and right (translation in three perpendicular axes) combined with the rotation (pitch, yaw, and roll) of 3DoF systems.

I was interested to see how 3 DoF motion controllers would mesh with a 6DoF headset, in my case the Valve Index. My previous experience of using two different tracking systems together was limited to brief sessions with Lenovo’s Mirage Solo and HTC’s Vive Focus.

Both of those devices 6DoF headsets felt comfortable and immersive but compromised by a “fixed point” 3DoF controller which acted like a strange laser pointer fixed to my hip.

Is 6DoF possible?

It is possible to attach an HTC Vive Steam VR tracking puck to a special bracket, but after speaking to TG0 they advised me to wait for the new 6DoF SteamVR version of ette which is due later this year.

For the purposes of these experiments I limited myself to using the Etee visualiser whilst viewing the desktop through my Index headset, as I was more interested in the direct “hand feel” of using the controllers rather than interacting with virtual worlds.

After charging the controllers using 2 USB leads provided with the dev kit, I installed the software and took them for a test drive after starting steamVR alongside the Etee visualiser.

Calibration and rotation are easily handled through the Etee application, with a simple keyboard input starting each process, and on-screen instructions which indicate the position the controllers should be orientated against.

After getting them calibrated and setting rotation, I started my journey…

SO WHAT ARE THEY LIKE?

They feel surprisingly light in the hands, though unstable as they roll inwards towards the palm as the fingers are closed.

For quick comparison I looked at what happened when squeezing an Index controller and what happened when squeezing an Etee controller

Because Etee is clamped to the upper bones (proximal phalanxes) of the fingers rather than across the palm like index, closing my hands causes the controller to rotate as my phalanxes change angle, a large gap of 30mm before making contact with my palm.

This also causes the thumb to pivot backwards, if using the thumbpad whilst trying to close your hand! The image below shows the immediate difference in how the Etee and Index controllers are clamped to the hands.

Moving my fingers produced an immediate response in the Visualiser application and I started noticed haptic feedback loudly buzzing inside the controllers as “gestures” were made using combinations of fingers.

The most impressive aspect was their finger tracking, which I found to be very reliable once the controllers were fitted correctly and calibrated.

Individual finger tracking was almost flawless, even when lifting fingers off the body surface and placing back down in a slightly different pose; unlike my Valve Index controllers which sometimes struggle to maintain accurate per-finger tracking despite the “drum roll” recalibration and hardware reset tricks.

Etee’s pinky (little finger) tracking was especially reliable, and allowed me to finally include my little finger as a reliable participant in my experiments

Another impressive feat was their sensitivity to finger pressure, as mentioned in their literature “100 levels” per finger and its easy to understand this is no idle boast but a reflection of the precision of their material sensing technology.

This sensitivity allows controlled ramping up of pressure, and it was great fun “driving” my fingers and watching the finger levels rising from green to orange on the Visualiser.

I found the calibration process which uses outstretched hands created a strange finger input pressure if I tried to relax my hand into a neutral pose; try relaxing your arm and hand, and watch your fingers curl inwards as if holding a drink.

I tried to recalibrate from this neutral position but it caused the calibration to go a little wonky so I reset it to the outstretched fingers position again. This meant unless I kept my fingers outstretched (an unnatural pose) the input pressure rose typically on the pinky and ring fingers.

In terms of hand fit, I immediately found the foam finger bar too close to the controller body, causing my fingers to feel compressed to the point of discomfort, limiting my session time.

This sensation felt much more pronounced as Etee are securing the controller to the hand by clamping a foam block across the dorsal side (backside) of the Proximal Phalanxes.

The dorsal side of the hand is unused to pressure as its pretty much unused in everyday life, unlike the palmer side which is familiar with contact as we hold objects by using fingers to pull objects against our palms (try picking up your smartphone).

I refer back to my ergonomics article on the Valve Index controllers:-

The skin of the palmer side including the fingers is tough, thick and hairless with your fingerprints (double rows of papillae) help you grip objects as well as protect the skin from ripping.

Straight away with the Index controller I have the odd sensation of having something clamped across the back of my hand, it’s unusual as it goes against a lifetime of not having anything clamped across the back of my hand!”

The Etee controllers go one further than the Index controllers in clamping to a more sensitive part of the hand with thinner skin, and clamping using a high density foam of narrow width which is readily felt as it localises clamping pressure causing a proprioceptive challenge like Index.

Where Etee is less problematic is that the hand has soft rubber on side and foam on the other with Index having fabric on one side and hard plastic on the other which causes a material mismatch.

There wasn’t any way to adjust the position of the foam, as the bar was a fixed length to the controller body, so I turned my attention to the foam itself; thankfully this was only secured with adhesive tape so it quickly came loose.

Now with a blank finger bar, I searched through my fitting toolbox and found a number of different pads from bicycle helmets as well as foam pipe lagging of different thickness. Getting to work I trimmed different pads and stuck them in place, quickly realising the difference between ‘just too tight’ and ‘just too loose’ was critical to hold the controllers firmly in place without discomfort.

The alternative cushioning was interesting to try out, but made the controllers less stable as the material was a little too soft allowing free movement of the fingers, it needed to be a higher density like the original Etee foam cushion.

Moving further I removed the finger bars completely and tried using the controllers “naked” which was interesting, though a bit frustrating as without clamped fingers the sensitivity was all over the place making reliable inputs less frequent.

After spending a while trying the Etee controllers without their finger bars I decided to strip them down further and had a good look inside after peeling off the rubber controller body. The sensor strips were clearly visible, and some internal hardware.

Before putting the Etee controllers back together, I wanted to examine how changing the shape of the controller body would alter the hand fit so cut and taped together a larger diameter foam shape with a forward offset to create a relaxed hand pose.

Without the finger bar the controller felt like an oversized GearVR or Daydream remote and surprisingly comfortable to hold though the sensors did not register buried far underneath the foam. The big difference was that the controller did not “roll” in the palm when pulling the fingers as there was no gap with my hand “filled” by the new shape, creating a more stable grip pose.

Looking at other grips used for different sports equipment, handlebar grips on bicycles were an immediate comparison.

Round, constant diameter rubber grips are used on flat-bar sports and mountain bikes to allow the hand to move dynamically as the rider moves their body about on the bicycle, especially when standing up or sitting down. This instability of grip in the hand is what helps give a sports bicycle their agility, but at expense of stability and comfort.

In contrast, shaped ergonomic grips are commonly used for leisure bikes which are typically ridden in a seated position; another use for ergonomic grips is for riders with ulnar nerve damage whom benefit from a reduction in pressure on the wrists by having the palm fully supported.

After my quick test with the foam the solution to adjust the shape of the controller body and rubber skin would be the decision of TG0 as it would require a new design of controller (though using the same technology). Satisfied that adjusting the body shape could prove very beneficial. I refitted the rubber skins and thought more about the finger bar.

Adjustment time

I needed to create an adjustable distance finger bar; using the original high density foam piece and accommodating for different hands by moving the finger bar in or out, rather than trying to adjust a fixed distance using different thickness foam pieces…which hadn’t proven successful so far.

After sketching out the existing design and looking at the measurement I realised that creating a method of adjustment was going to be tricky due to the lack of physical space around the finger bar and body junction.

Following a number of iterations in my workshop using different cog parts (commercial off the shelf goods) like metal brackets from bicycle mudguards, plastic light fixings and different sized metric fitting bolts I finally managed to create a working prototype which actually surpassed my expectations in terms of its adjustment range.

By removing the finger bar’s attachment block (which has 2 angled keys that lock into slots on the body) I created an empty volume of space in which to fit an adjustment mechanism; 2 steel plates with oval slots to allow “infinite” sliding adjustment within its range.

A fixing bolt was captured with a knurled plastic knob with its own internal screw thread, and various bolts, nuts, grub screw used to attach the controller body to one of the steel plates, and to attach the finger bar to the other steel plate.

Finally I cleaned up the finger bar with isopropyl alcohol and firmly stuck some male velcro in place, and female velcro on the rear of the original finger bar foam so that the foam cushion could be adjusted from left to ride along the chanel of the bar – this would allow fine tuning of the foam ridge relative to the index finger on each hand.

After assembling my prototype I sent an email to TG0:

Previously I found the controller squashed my fingers which was quite uncomfortable and limited my time using them, unfortunately no way to adjust the clamping force though I tried a number of different cushions inside the finger bar (always slightly too loose or too tight). 

I quickly realised a method of adjustment was required. 

I went through many iterations to try and get this right as space was very limited whilst it needed to be easy to adjust whilst wearing, and offer “infinite” adjustment within the range of movement (clicks/notches are often just too tight or too loose).


This modification allows 3 adjustments to accommodate a wider range of hands/fingers. 

1. Distance (depth) from controller body to finger bar 

2. Angle of finger bar relative to controller

3. Lateral position of foam relative to index finger

Adjustments 1 and 2 are made using the black knurled knob which loosens and tightens a bolt, easy to do whilst wearing. 

Loosening the knob allows forward and backwards sliding movement to set the distance and adjust angle if required; tightening the knob locks the position. 

Adjustment 3 is made by repositioning the foam on the finger bar, because the foam is now velcro backed it’s easy to adjust left to right(can also swap to different shapes or materials)”.

The proof is always in using something practically, so I slipped both controllers on and started the Visualiser. For the purpose of this experiment I had modified only the left controller, as I didn’t want to risk damaging both if it didn’t work properly.

Thankfully, this was not the case, with the new adjustable left controller allowing me to find the ideal depth and best angle for the finger bar foam to maximise comfort whilst maintaining enough clamping pressure to retain the controllers in place.

This adjustment was easily done whilst wearing both controllers, with the knurled knob very easy to turn due to its vertical orientation.

The adjustment angle of the finger bar foam was limited by its square cross section, perhaps cutting a slight chamfer on each outside edge would soften its presence and allow more angle adjustment whilst providing enough flat contact against the load bearing bone to stabilise the controller.

Having the adjustable left controller and fixed right controller to compare against each other allowed easy assessment of the differences in comfort; the adjustable controller now accomodating my hand fit without squashing my fingers.

In terms of function, still very similar with the controller body rotating towards my palm every time I closed my hand.

Clamping the controllers to the proximal phalanxes will always cause this rotation but without a 6DoF version to assess using steamVR applications, I was unable to properly assess the etee controllers as virtual reality input devices.

The question of whether the mechanical switches, for example the trigger common to existing motion controllers, can be replaced by TG0 sensing technology; wasn’t something I managed to properly assess during my experiment.

The day following the completion of the adjustable left controller, the rigid plastic finger bar of the right controller snapped across its middle whilst I was removing the controller, putting an end to my experiments with Etee.

I suspect it fractured from being overloaded by my fingers being too large to accommodate, stressing the plastic over time and failing at the weakest part of the finger bar.

After speaking to TG0 they advised me the plastic was not production strength but a weaker 3D printed piece; this failure should not occur on production controllers and so my failure with the Dev kit should not be considered representative.

Immediate improvements to my adjustable concept would be a more rigid adjustment structure as the steel plates were rigid enough for my testing purposes but would benefit from being stiffer for day to day use especially for larger hand users with more strength and finger leverage.

Additionally, a “captive” bolt for the sliding adjuster plate to make it even more responsive to adjustment (the existing bolt can start turning if the knurled knob is unscrewed too far).

Finishing my time with the Etee controllers, I thought about the improvements that could be made to their ergonomic shape, and adjustment to suit a wider percentile of users.

The sensing technology itself was very impressive, and with a successful Kickstarter now backed and a SteamVR version due towards the end of the year there is a lot of potential waiting to be unlocked from this interesting product.

Thanks to TG0 for supplying this sample, I wish them luck in their developments. And thanks to you for reading! Rob Cole, immersivecomputing.org

By immersivecomputing.org

Human exploration of the immersive computing interface

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