FSR Matrix Sensors for Human-Computer Interaction

In a previous post I talked about a capacitive multi-touch solution that can work well for multi-touch computer control, where you don’t want or need a display as part of the multi-touch input surface.

Another alternative that provides even more expressive control is to use a Force Sensing Resistor (FSR) Matrix sensor which not only gives the x and y position of numerous touch points, but also gives a z parameter for how much force is being applied at each touch point. One company, Sensitronics (owned and run by the inventor of FSR sensors, Frank Eventoff), makes the raw matrix sensor sheet and they are happy to partner with other companies who will built the rest of the input device electronics, PC drivers and libraries. The materials used for FSR matrix sensors make them opaque, so this technology will work for trackpads, graphics tablets, etc, but not for displays. Sensitonics recently made available larger sensor sheets, moving beyond the smaller sizes (typically laptop trackpad size range) previously available.

However, Sensitronics has recently also been working on breakthrough clear materials, and can be contacted regarding this new innovation. Clear FSR matrix sensor sheet applied to a display will provide a very attractive alternative multi-touch display for many use cases.

Note that FSR sensors can also be produced as sensing strips, rings or individual buttons, however my primary interest has been in multi-touch x-y-z grids for gesture control of computers.

For anyone wanting to use an FSR matrix sensor in their project there is currently a drawback – input devices utilizing the technology are not widely available, and it is a significant amount of engineering work to develop the electronics, PC drivers and libraries to support a usable solution. One company I know of is producing a more complete FSR matrix solution – Sensible UI from Korea. Check out their ArduMT if you want a development plug in solution for PCs.

Sensible UI - ArduMT multi-touch input controller

Sensible UI - ArduMT multi-touch input controller

Good Multi-Touch Input Devices

I do human-computer interaction (HCI) research in the medical imaging industry, and as part of that work I’ve been tracking touch and gesture surfaces for PC computer control and working up prototypes. Since there is a close correspondence between HCI and human machine interaction (HMI), which is important for robotics, I have a couple of insights to share on recently available very good quality multi-touch pad input devices useful for all sorts of domains including robotics, digital music, and computer users and researchers of all stripes. I’ll describe the first in this post, and add the second in the next post.

Hackers, researchers and DIY’ers have wanted a good programmable solution for desktop touch and gesture input to PCs for a long time. Consumer device solutions without programmable APIs or SDKs have been hacked by brave souls, such as the Wacom Bamboo line of graphics tablets or the Apple Magic Pad, to gain some access to the sensor output through hacked drivers.

These solutions were always a stop gap and not accessible to many because they were unsupported by the vendors, limited in their access and brittle to changes. A quiet change by Wacom with their most recent Bamboo graphics tablet line, released Sept 27, 2011, has completely changed this picture. The Bamboo Capture and Create models now boast significantly revamped capacitive multi-touch input that rivals what you are used to on mobile tablet devices like the iPad. The biggest change is they have also developed and released an SDK to support programmatic access to the touch information coming from these tablets. This makes them ideal for people wanting a custom multi-touch solution.

From using the SDK I’ve discovered that, even better, you can write an application to interpret the touch and gesture input how you want to, while at the same time utilizing your choice of the out-of-box gestures that come with the standard Bamboo driver such as pinch zoom, scroll, full mouse control, etc. They provide a driver configuration panel to enable or disable any out-of-the box touch and gesture support so it’s easy to create a solution mixing some default and custom gestures. Of course, being Wacom graphics tablets they all support pen as well as touch input. The devices span various sizes, prices, and come with a wireless option. I’ve tested all this and it works great, so I’m hoping this helps spread the news to the Internet communities that are interested in multi-touch and the natural user interface (NUI).

Wacom Bamboo Create Tablet

Wacom Bamboo Create Tablet