ActivitySense - how does it work?

  • February 20, 2015

Our RockSTAR and RockFLEET devices are used throughout the world, tracking all sorts of things - people, vehicles, machines, animals. Most of the time you set a transmission frequency for the unit (e.g. once every 15 minutes), attach the tracker, and then leave it to do its job.

However, over the years we've been asked whether this speed could vary, depending on the motion of whatever the tracker was attached to.

What we've come up with, is a system called ActivitySense. ActivitySense has been introduced in the latest version of firmware for RockSTAR and RockFLEET units, and It uses a combination of sensors to determine whether something is 'moving'. The problem is, different 'things' move in different ways. How do we cope with that? Well, let's take a couple of examples:

ActivitySense on cars/bikes

When a car's engine is running, and when it's driving along the road, there tend to be an element of vibration. When the car or bike is stopped, and the engine turned off, that vibration goes away. We use a mode called 'Bump' which employs the accelerometer inside the tracker to detect this. If we detect vibration continually for a period of 10 seconds then we start transmitting at a faster rate. When that vibration has stopped, for 60 seconds or more, then we drop the unit back down to its normal transmission rate.

Obviously different vehicles have different levels of vibration though, so we have an adjustable threshold, so you can tune the detection to match your particular requirements.

ActivitySense on airplanes

Whilst an airplane will tend to vibrate and bump around when on the ground, once it reaches cruising altitude and throttles back most of that vibration goes away. So we can't use the same vibration-detection method as we use on cars/bikes. Instead we also use the GPS chip, and have a mode called 'Bump+GPS' - the vibration on the ground initially wakes the unit up, and turns on the GPS chip. The transmission speed increases. We then monitor the speed of the plane via the GPS chip, and we keep transmitting more quickly until the GPS speed drops below 4mph.  The plane is unlikely to be in the air at that speed! Then we drop the transmission rate down again, and wait for bumps to wake it up next time.

ActivitySense via power

For some applications, we have been asked if our units can transmit more quickly when receiving external power - and less quickly when running from batteries. Again, we have a mode in ActivitySense to detect this, simply called 'Power'. If external power is applied then the tracking frequency can be faster than if running on battery. A good example of this is one of our customers who uses units on rapid deployment rigid-inflatable-boats. Whilst the boats are 'docked' on the mother-ship, they transmit once every 2 hours. As soon as the ignition is switched on, they start taking positions every 5 seconds and transmitting once a minute.

Cost savings

Apart from the flexibility ActivitySense gives our customers, by automatically managing how often it transmits at different times, it also saves them money. Each position report transmitted over the Iridium satellite network costs money, so why transmit every 5 minutes for days on end when whatever you're tracking is sat in the same place?

To find out more about ActivitySense, or any of the other features of our products, get in touch!

 

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