Problem Statement

In a study of 87 normal, older adults, measurement of walking patterns and mood showed correlational evidence that gait could provide an index of level of depression in a clinical population [1]. In addition, improving gait pattern has been shown to reduce the risk of pain and injuries, utilize the body's natural shock absorption mechanisms, and distribute energy workload from walking and running over time. Our project intends to promote a proper gait to improve the wellbeing of those who use it.

[1] Sloman, L, et al. “Mood, Depressive Illness and Gait Patterns.” Current Neurology and Neuroscience Reports., U.S. National Library of Medicine, Apr. 1987, www.ncbi.nlm.nih.gov/pubmed/3567834.

Overview of How It Works

Our device evaluates a user's gait and determines if they’re walking in the most optimal manner, based on their foot pressure distribution. We achieved this through pressure-sensitive conductive sheets in a set of portable floor pads. We evaluated their gait based on the average amount of pressure placed on their heel or ball of their foot. This triggers a strand of RGB LEDs to light up according to the gait evaluation result.

When initializing the pads, the first round of white LEDs allows the user to flip over the pad onto the floor and placed in the desired position. When the second round of blue LEDs lights up, this is when the user must step on the pads. This records the maximum and minimum applied pressures for the front and back of the foot. Using these numbers we used it to normalize future readings of the velostat. In addition, we calculate a variable threshold that detects when the pad should start reading values, based on if someone is stepping on the pad.

Image

Our final iteration of the project is displayed in the images above.

Step 1: Materials

List of Materials (for a single pad)

1 Lilypad Arduino (https://amzn.to/2Pjf5dO)

¼ of a Sheet of Velostat (https://amzn.to/2Pkfrke)

¼ of a NeoPixel RGB Strip (https://amzn.to/2E1dGGG)

14" x 16" ¾ Inch Plywood (https://amzn.to/2QJyPf8)

1 1.3V Lithium-Ion Battery (https://bit.ly/2AVIcP7)

Wire (https://amzn.to/2G4PzcV)

Copper Tape (https://amzn.to/2SAIBOf)

Aluminum Foil (https://amzn.to/2RFKs47)

Wood Glue (https://amzn.to/2Qhw7yb)

Step 2: Laser Cutting

We laser cut two pieces of 1/2" plywood for each foot pad. The bottom part houses the wires and electronics, whereas the top frame features the pressure pads and protects the parts below. A total of 8 pieces will make 4 footpads when joined together.

The Illustrator file is the final dimensions of the footpad. The RED lines are to be set to CUT, and the BLACK is to be engraved. Depending on the laser cutting machine, different power/speed combinations will be needed to get an engraving deep enough to have the Arduino Lilypad sit flush under the footpad. For reference, we used 50 speed, 40 power, and made 3 passes.

Footstep Prototype Full Size.ai
Download

Step 3: Wiring

We used the LilyPad Arduino AT, which comes with a total of 11 connector pins.

Here are the details for wiring the Gait Keeper as shown in the Fritzing diagram and prototype images above:

Front Velostat Positive > A5
Back Velostat Positive > A4
Velostat Grounds > GND Pin
LED Signal > A3
LED GND > GND Pin
LED Positive > Positive Pin

Step 4: Code

Below is a link to our code, and attached is a picture of our pseudocode and approach:

gaitkeeper.ino
Download

Step 5: Assembly

For the final assembly process, we first cut the NeoPixel RGB Strip into pieces long enough to wrap around the circumference of the pad and cut wire to fit into the tracks that we had engraved into the pads. We then soldered the wires to the appropriate pins on each of the Lilypads, as indicated in the first image above, and uploaded our code onto the boards. Next, we threaded strips of aluminum foil through the slots we had laser cut and taped them in place, as displayed in the second and third images. Then, we used the tracks for the wiring to attach to the aluminum foil using copper tape and soldered the wiring connected to Lilypads to the corresponding contact points (pin A5 to the front pad through the top of laser cut wiring tracks, pin A4 to the bottom, and the ground through the middle - shown in the fourth image).

As displayed in the fifth image, we secured strips of Velostat that were cut to the same size as the aluminum foil strips, taping them in place to ensure they made uniform contact with the conductive material. For the top layer of conductive material, we used copper tape for its durability, creating a spiraling pattern to cover the entire surface of the rectangular wood piece seen in the sixth image above, holding everything in place. We also used the copper tape to create a connection between these spiraling layers threaded through the laser cut slots to reach the soldered ground wiring.

Finally, we sandwiched all of the materials and connected the entire wooden framing pieces, connected the charged batteries, and glued the Lilypad into its designated housing unit. Once everything was set in place, we used wood glue to stick the wooden framing together and then attach the cut RGB strips to the outer rim and left the glue to dry overnight.