March 19 2023 Update

In my previous post, I mentioned two projects I would be working on: creating a hybrid VR shoe/slider and a mecanum wheel.

Hybrid VR shoe/slider

In the last post I explained how I made a cheap slidemill and walking on it was very unstable. To improve stability and allow for omnidirectional movement, I designed a slider with a row of wheels on the bottom to keep the foot moving in a straight line while still allowing for sideways movement. So I came up with this design.

The is meant to go on the right foot. The bottom of the slider has a row of wheels under the left side of the right foot. The rest of the slider is covered with a silicone pad. This overall design is very similar to my current pair of VR shoes, but it's mostly 3D printed instead of being made out of aluminum.

Initial testing with one slider have been successful. It feels much more stable than the last time I walked on the simple slidemill, yet I can still easily move my foot sideways. I now need to make the left foot slider.

Mecanum wheel

I managed to make a design for a mecanum wheel that has a 2.063in diameter. I'm going to need to make 3 more and mount them onto a shoe-like frame and see if they work well. I'll be checking how bumpy they are, if they can move nicely under my weight, what kinds of surfaces I can use them on, and how loud they are.

March 2023 Update

In this update I'll be going over several devices I've been experimenting with over the last several months. Then I'll talk about next steps.

Leg Exoskeleton

In my last update I said I was trying to focus on making a new VR locomotion setup using a leg exoskeleton design. Well, that isn't going as planned. I made a few designs to try out. These differ from the first exoskeleton design I tried out a while ago. I wanted a design that would run along the user's leg so that supporting sitting would be easier and the user could cross their feet without the exoskeleton on one leg colliding with the other leg.

Here are a few of the designs I made.

With this design I wanted to make something that was easy to adjust to curve around anyone's butt. Each of the individual links can be rotated to make different curves.

This design was less customizable but had a simpler design. The lengths could still be adjusted by using bolts of different lengths.

The 3D printed parts in both designs are made out of TPU.

With both designs the idea was there would be some flexibility to move back and forth as the user's hips swing, but still be rigid enough to keep the user in place.

Both designs felt awkward to strap my thigh to. It didn't really provide much resistance to me bending or moving my leg around like I'd hoped. Sitting would cause the strap around my thigh to tighten very uncomfortably.

In the last post I listed a series of benefits a leg exoskeleton could provide. Now I'm not so sure about several of them, because of the testing I did with these designs as well as some other testing with other devices I will explain later in this post.

I think I'm going to pause creating a leg exoskeleton, and if I start again it's going to be something like my very first design, which doesn't run tightly along the user's waist, butt, and legs.

A Simple Slidemill

I wanted to see if I could make a slippery surface like a slidemill has, but avoid some of the issues slidemills run into. Slidemills suffer from feeling like you're running on ice and lack stability as you run. I wondered if I could use a slippery surface because it could simplify the design of a device, but also have the device have a way to make running feel more natural and stable. Oh, and hopefully make something not as loud as slidemills are.

My thought was that if the device could always be trying to keep the user's foot centered better than the bowled surface of a slidemill, it would provide stability. As the user brings their foot forward, there will be some resistance they push through, but once they put their foot back down on the platform it won't slip because the device will help the user pull their foot back. The devices I was thinking of were the leg exoskeleton and a device I'll talk about in the next section.

Here is the slippery surface I made.

The materials

To make a slippery surface, I tried out a variety of surface materials and lubricants. The surface materials were acrylic, a few types of wood, HDPE, UHMW, and a metal sheet. The lubricants were silicon spray, heavy grease, a few types of furniture polish, sex lube, vegetable oil (liquid and spray), and dish soap with and without water.

The acrylic sheet seemed to be the best surface type, followed by the HDPE. With acrylic I was not only able to make a slipperier surface than the rest, but it was also quiet. 

The best lubricants were the lube, dish soap with no water added, and a furniture polish spray. The lube was the best, but dish soap was almost just as good. Since dish soap is the most widely available and cheap, I did further testing with it.

I have done a few test sessions where I walk on an acrylic sheet covered in dish soap for up to 15 minutes. The soap didn't dry out in that time. In further testing I'm going to see if while playing it needs to be sprayed with a little bit of water every now and again. Between play sessions, I'm...

Feb 2023 Update

Over the past 8 months I've been making prototypes of many different VR locomotion devices. I've been trying out many different concepts, but now I'm starting to focus on one setup again. 

Tldr

I'll be expanding upon the leg exoskeleton concept I tried. It will be attached to either a VR shoe with wheels or a floor slider. I will attach the leg exoskeletons to my ceiling mounted support rig first, but then I want to try to make a new free standing support rig.

Leg Exoskeleton 

I'll be making the next leg exoskeleton out of EMT conduit like I did with the last prototype. The joints will be 3D printed and designed to be springy. I first wrote about the idea here, with this quick summary -

When the joints flex, they will store some energy and want to return to their original form, like a spring. 

The basic idea is that as the user brings their foot forward, there will be some resistance because the joints will flex, then as they bring their foot back, the joints will help them. The joints store some energy when they bring their foot forward, then release it when they bring their foot back.

Benefits

• Stability. 
  • With the mechanism always wanting to bring the foot back to the starting position, it will be harder for slipping to occur.
  • The shoe could be taller if needed since the mechanism should make it harder to tip the shoes.
• The weight of the shoe can be negated.
  • The mechanism can help the user lift their foot. To lower their foot, they just let the weight of their own legs overcome the force from the joints.
• Springy joints can help reduce impact on knees.
• A taller and/or heavier shoe or floor slider is easier to add more features to, such as something simple like cushioning to reduce impact on ankles or something complicated like simulating stairs.
• Less effort
  • Since energy can be stored in the springy joints, once the user gets going, it should be easier to keep going. 
• Can be paired with an omnidirectional VR shoe or a floor slider to provide omnidirectional movement.
• Can support sitting in the same way wearable chairs can.
• User can be strapped to the leg mechanism, so a climbing harness, waist harness, or vest is not needed.
  • Nothing needs to be strapped to the user's back, reducing the possibility of back pain.
  • Less constrained movement.
• Great tracking.
  • Potentiometers or encoders can be placed in each joint to track leg and foot movement precisely. 
  • Turning will still need to be tracked via an IMU or encoder on the support rig.
• Conduit can be telescoping rods making it adjustable to different heights.
• Simple, durable design made of cheap materials (conduit, 3D printer plastic mostly).
• Coupled to a support rig, this still provides safety and keeps user constrained to a small space (around 42in in diameter in my case).
• No electronics except trackers.
• Design is can be adapted to be motorized later if I want.

Cons

• Compared to motorized VR shoes by themselves -
  • More hardware.
  • More storage space.
  • More constrained.
  • Less convenient to strap into.
• A passive system with springs will probably still not feel as natural as a motorized system.

VR Shoe or Floor Slider

I've been looking into making small omnidirectional wheels, such as the omni-sphere, to use in a VR shoe, as well as looking into if a floor slider could work.

Making small omnidirectional wheels (2in or less in diameter) that are not bumpy, can handle the load, and are not noisy has been a challenge I will write about later. I still have more ideas, including possibly using large omnidirectional wheels in a design similar to these motorized shoes.

Regarding floor sliders, I've made some progress. The issue I've ran into in the past is the friction is too high and they are noisy. Even if I could lower the friction, they are also unstable. However, the leg exoskeleton providing stability means lower friction shouldn't be a problem. With that in mind I've tried various combinations of floor types such as acrylic, wood,...