This blog will mainly consist of a video demonstration of the V-SAS in an indoor setting. The previous blog (#11) covered the system objectives and features. There will be a third blog in this mini-series to demonstrate operation of the system in a vehicle.
Ultrasonic Distance Sensing
Ultrasonic sensors need to be very sensitive to detect distant reflections off small objects, but this makes them very prone to detection of spurious noise and pressure variations. To prevent these spurious detections from confusing the readings some signal processing is normally required. A simple low-pass filter on the distance readings can minimize the possibility of showing a full-scale reading, but it also means that any spurious signal will influence good data and make it less accurate. A better solution is to take several readings and choose the median reading as the most accurate reading. This solution will tend to ignore full scale spurious readings at either end of the scale. I found this works reasonably well, but it does require a fairly complicated algorithm to find the median reading. In my limited testing, the sensor seems to detect a lot more spurious “short” reflections than long reflections, so it may be more effective to choose a reading above the median reading. Currently, I am using the largest of 3 readings as the most accurate choice, and this is performing better than choosing the median reading. If I go to 5 readings, the median is likely to be better than the largest, but it also slows down response of the system. So far, I think I would rather use my brain to help ignore spurious readings than allow the system to take more time to present better data. In applications where the machine must be correct without human help, a different approach would be used.
The LED Road Test page is here:
http://www.element14.com/community/roadTests/1481
The Lighting Group page is here:
Here are links to my other blog entries for this road test:
LED Road Test - Proposal - Blog 0 Jan 1, 2016
Light Emitting Diodes Road Test - Blog 1 Nov 1
LED Road Test - 3D Printed Housings - blog 2 Nov 10
LED Road Test - Dodecahedron Light Fixture Blog 3 Nov12
LED Road Test - Wearable Interactive Lights - Blog 4 - Nov 13
LED Road Test - Interactive Trophy - Blog 5 Nov 16
LED Road Test - Making Household Objects Interactive - Blog 6 Nov 22
LED Road Test - Power LEDs - Up & Running - Blog 7 Nov 24
LED Road Test - Star Wars - The Force Awakens - Blog 8 Nov 28
LED Road Test - Selfie Phenomenon - Blog 9 Nov 29
LED Road Test - MSP EXP430FR4133 Launchpad IDE - Blog 10 Dec 6
LED Road Test - Vehicle Situational Awareness System Blog 11 Dec 14
LED Road Test - Vehicle Situational Awareness System Indoor Demo - Blog 12 Dec 20
LED Road Test - Maple Leaf Christmas Decoration - Blog 13 Dec 24
LED Road Test - Reflow Soldering Power LEDs - Blog 15 Jan 10
LED Road Test - Induction Heating Reflow Soldering - Blog 16 Jan12
LED Road Test - Summary - Blog 17 Jan 15
Associated Video Links
Creating a Light Fixture using 123D Design
Wearable Interactive Arc Reactor
Interactive Illuminated Household Objects
Star Wars - Let The Force Be With The Light
Vehicle Situational Awareness System in Operation
Vehicle Situational Awareness System Operating at Night
Induction Heating Reflow Soldering
Top Comments