tracking position by using bluetooth low energy (ble ...cc2540 chip comes with an accelerometer...
TRANSCRIPT
IntroductionBluetooth Low Energy (BLE) is an emerging
wireless transmission standard part of Bluetooth’s
Core Specifications v4.0 and aimed towards
applications which require small wireless
transceivers with low power consumption,
reduced bandwidth and simple connections. The
CC2540 chip comes with an accelerometer which
is manufactured by VTI and capable of detecting
motion along three axis.
Materials and methodsBy default, the drivers supplied by TI activate the
±2g range; however, it can also work with a ±8g
range and in free fall mode. It has a sensitivity of
56/14 counts per g, resolution of 18/ 71 mg. We
have designed GUI so that the users can turn
on/off accelerometer and choose the axis that
they want to measure. The device operates in an
interrupt type protocol, these interrupt messages
are referred to as notifications because they are
only sent back from the Keyfob to the dongle
when new data is available to be sent. The value
then needs to be interpreted from a byte to g
values. The Keyfob reads the data from the
accelerometer every 10ms.
Area n = (Sample n + (Sample n – Sample n-1 )/2 ) *T
Formulas to obtain the velocity and position;
• Velocity[1] = Velocity[0] + ((Acceleration[0] + Acceleration
[1])/2)*0.01
• Position[1] = Position[0] + ((Velocity[0] +
Velocity[1])/2)*0.01
ConclusionsLimitation
1) The device has to be moved fast so that
error percentage becomes smaller.
2) The device cannot differentiate between
tilted and translation movement.
3) Testing conditions are far from ideal.
Future Work
1) The accelerometer will be installed into a ball,
therefore the motion will be fast enough to make
the error percentage small
2) The accelerometer will be combined with
the gyroscope so that the device can
differentiate between tilted and translation
movement.
Tracking Position by Using Bluetooth Low Energy (BLE)
Texas Instruments CC2540 Development KitMohd Hazeeq Hanafi, Thanh Ngon Tran and Tho Le - Ngoc
Department of Electrical & Computer Engineering, Broadband Communication Research Lab, McGill University
Fig 2. Offset Calibration
Fig. 4a). Acceleration, Fig. 4b). Velocity, Fig. 4c). Position
Fig 4a) is the graph of acceleration; we have set
certain direction that the acceleration will increase
first then decrease. Fig 4b) velocity is the
integration of acceleration graph, it increases
(positive area) then decreases (negative area)
Fig 4c) position will always increase as the area
below velocity graph is all positive.
Future Applications
Fig. 1. These are the
CC2540 Keyfob board,
CC2540 USB Dongle
and Debugger
Results
SOFTWARE DESIGN CONSIDERATIONS :
1) Signal is not noise free, so we implement
moving average filter to filter the signal.
2) Real value of acceleration is sampled
acceleration minus calibration value
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146
151
acc
(m
/s^
2)
Samples
0
0.1
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0.5
0.6
0.7
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Vel
oci
ty (
m/s
)
Samples
0
0.05
0.1
0.15
0.2
0.25
1 6
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1
Posi
tion
(m)
Samples
Actual Distance(cm) Result
Distance(cm)
Error
Percentage
(%)
X 24.0 23.13 3.6
Y 27.5 27.13 1.35
Z 19.0 19.9 4.7
2DX = 21
Y = 30
X = 20.21
Y = 28.57
X = 3.76
Y = 4.76
We’ll combine the accelerometer and
gyroscope so that we can track the balls
position in 6 degree of freedom.
We can also add this application to our
medical sensors so that we can detect if
the patient is falling.
We can add this application to video
game such as Wii, plus with ultra low
power consumption it’ll be great
prospect for future market.
Table 1
Fig. 3a) .GUI
References- Freescale Semiconductor Application Note,
AN3397 REV 0, 02/2007
- CMA300 data sheet from VTI Technologies,
Doc Nr. 8281000A.04
Fig 3b). 3D Display
4a)
4b)
4c)