Motivation and what I am trying to do:
I got this idea when I was watching Daredevil on TV. Our hero is a blind person with a heightened senses. He even fights crimes in his spare time. But we live in reality and don't get superhuman senses from unknown chemicals.
On the other hand, a very crude form of echo location might be something within reach of a hacker. This is not meant to be a toy prop, but an experiment to see if I can design something low cost that would help a visually impaired person to navigate indoors.
It is a serious problem as there are 40 millions people world wide and 1.3 millions in the US that are legally blind. This is a personal project right now funded by myself. At some point when the project is ready for alpha release, I'll present this and work with the local groups in the area for a trial and hopefully production.
What this can do and how it is different than similar projects:
There are a few projects/design that I came across. My design has a different design philosophy. I want tighter integration for better battery life, size, weight reductions than is possible with using off the shelf modules. The design should also be intuitive and ergonomic for the end user.
Two range finders (one for each side) are located on a pair of glasses. As the head is turned, each of the range finders would try to map out the distances in front. With simple math, the device can figure the amount of correction to get the user to walk parallel to the hallway.
With simple geometry, the angle ϴ can be worked out. The device can then inform the user how much correction is needed to stay parallel to the wall.
tanϴ = w / (d1 - d2), so ϴ = arctan( w / (d1 - d2) )
The device can detect the distance and the amount of drop in front e.g. a staircase Since the head mounted sensors have a relative a fixed height (vs sensors on hand) makes it easier for the detection.
We can calculate the following from what we know or measure. Angle ϴ - measured by the Accelerometer; distance l return by the range finder while h is the height of the transducer from the floor.
depth of the stair from the sensor is h2 = l x cos ϴ so the relative depth of the stairs is h2 - h
distance from the step is d = l x sin ϴ
This type of information can be presented more easily by voice feedback.
One of the reason for a head mounted device is that voice feedback can be provided easily and discretely. Voice feedback allows for more complex information to be presented. e.g. the device should be able to tell the user the measured distance to a wall or the object.
The dual speakers or dual haptic feedback from the differences of the distances would help the person to align the heading towards the centre of a hallway. When walking, the body naturally follows the direction of one's head. The absolute distances from the sensor can be used to implement a proximity alarm that tells the me that he/she is about to run into a wall or a person approaches.
The sampling alternates between one of the two range finders. This reduces the interference otherwise would result. It also reduce peak power consumption and allows me to share the same receiver circuit. The update rate can be reduced if the person is moving slowly or that the reflection is far away.
The unit is powered by a rechargeable Li-ion battery with a target battery life of weeks. Readily available AA Alkaline/NiMH batteries can be used as emergency replacement. The circuit is designed to optimize power consumptions. Unused circuits are shut down to minimize power consumption. The unit can be placed in sleep mode if it remains stationary for a long time.
Unlike most of my projects, this is a new area for me. As such the project logs documents my learning process. I have compiled a TOC of the projects logs and organize them as below. At some further point, I might come back and document the implementation in a more conventional way like my other projects. Until then, hopefully they help the...Read more »