PowerForce – User Manual
Radlabor GmbH | Heinrich-von-Stephan-Str. 5c | 79100 Freiburg | Germany
www.smartfit.bike | www.radlabor.de
Inhalt
Important warnings ................................................................................................................................... 3
1. Introduction ........................................................................................................................................... 4
1.1 Pedal forces .................................................................................................................................... 4
1.2 Force components .......................................................................................................................... 5
Fr (resultant / total – force) .............................................................................................................. 5
Fe (effective / tangential – force) .................................................................................................... 5
Fu (unused / radial – force) .............................................................................................................. 5
1.3 Measuring Principle ........................................................................................................................ 6
1.4 Technical Data – Wireless edition ................................................................................................. 7
2. After unpacking ..................................................................................................................................... 8
2.1 components .................................................................................................................................... 8
2.2 Mounting .......................................................................................................................................... 9
3. Software Installation ........................................................................................................................... 12
3.1 Install NI-DAQmx Driver ................................................................................................................ 12
3.2 Install NI LabVIEW 2009 Runtime Engine Library ....................................................................... 12
3.3 Install IMAGO Records® ............................................................................................................... 12
4. IMAGO Record® .................................................................................................................................. 13
4.1 Introduction ................................................................................................................................... 13
4.2 First start and setup ...................................................................................................................... 13
4.2.1 Load Setup-files ..................................................................................................................... 14
4.2.2 Set, save and load calibration values ................................................................................... 15
4.3 Description of IMAGO® ................................................................................................................ 17
4.3.1 Main Menu .............................................................................................................................. 17
4.3.2 Index Tab ................................................................................................................................ 18
4.4 Measurement ................................................................................................................................ 21
5. CyclePlotAssistent .............................................................................................................................. 22
5.1 Quick buttons and contents ......................................................................................................... 24
5.2 Charts and Design ......................................................................................................................... 25
5.3 Graph Selection ............................................................................................................................. 26
5.4 Caption and legend ....................................................................................................................... 27
5.5 Save quick button.......................................................................................................................... 28
PowerForce – User Manual
Radlabor GmbH | Heinrich-von-Stephan-Str. 5c | 79100 Freiburg | Germany
www.smartfit.bike | www.radlabor.de
Important warnings
Please read the following warnings, before beginning to use your PowerForce System. Otherwise,
your PowerForce could be damaged, or not function properly.
✓ Do not over tight the pedals in the PowerForce System. Give some grease to the
connective sites to improve the reassembling of the pedals.
✓ If your open a sensor, the transmitter unit or the connection box, the warranty is no
longer valid.
✓ Never clean the sensor or the transmitter unit with water or use it in wet conditions.
✓ Do not cramp the position switch – it is sensitive for pressure.
✓ Check before each ride, that the sensors and the pedals are fixed properly.
✓ When unplugging any connection, always pull straight down rather than sideways,
or you could damage connector pins. Never pull on the cable itself, but rather the
plug.
✓ Carefully read through the full installation instructions before beginning, as
mounting the PowerForce System incorrectly can cause a fall or damage the
system.
✓ Do not load the sensor with loads higher than 300kg.
PowerForce – User Manual
Radlabor GmbH | Heinrich-von-Stephan-Str. 5c | 79100 Freiburg | Germany
www.smartfit.bike | www.radlabor.de
1. Introduction
1.1 Pedal forces
In cycling the transfer of metabolic energy into physical power or velocity of the rider-bike-system is
not one-to-one. Environmental as well as mechanical and biomechanical factors affect cycling
performance. The propulsion of the bike is generated by pedal forces. Therefore, the determination
of pedal forces is a major prerequisite to analyze cycling performance capability from a
biomechanical point of view.
The question is not why to measure pedal forces but how to do it. Comparing other existing
instruments whose purpose is the determination of divers mechanical parameters concerning
cycling propulsion, there are some methodological or practical limitations regarding the
requirements of either a biomechanical lab or a sports related center.
The most important advantage of the PowerForce System is the fact that there is no restriction to a
certain pedal system. Cyclists do not have to change their pedal-shoe interface (cleats) if they want
to measure their pedal forces with the PowerForce.
PowerForce – User Manual
Radlabor GmbH | Heinrich-von-Stephan-Str. 5c | 79100 Freiburg | Germany
www.smartfit.bike | www.radlabor.de
1.2 Force components
The PowerForce records the forces, which are performed on the pedal axis, separately for each leg.
Three force components (Fe, Fu und Fr) have to be differentiated.
Fr (resultant / total – force)
This is the total force which is generated by the athlete on the pedal. It is the vectorially sum of Fe
and Fu an is calculated, not measured.
Fr tells us about the total load, the rider applies to the system – the bike as well as to his own body.
Joint moments and forces result from (or cause) this component. Thus, e.g. inverse dynamics are
based on Fr.
Fe (effective / tangential – force)
Fe is the component of Fr which lies in moving direction of the crank/pedal which is a circle.
Therefore, the vector of Fe is always tangential to this circle or perpendicular to the crank. Fe is
responsible for the propulsion, but only if it is aligned forward with the rotating direction. If it is
aligned backward, e.g. if a rider does not pull up the pedal in the upstroke phase, Fe of the one side
must be subtracted from the other side.
Fu (unused / radial – force)
Fu is the component of Fr which does not generate any propulsion. It results in very small
deformation of the crank and pedal-axis. The direction off this force component is lengthwise to the
crank. The highest values appear around the bottom dead center (180° crank angle) where the
weight component (induces by the mass of the leg) adds to the muscular component.
PowerForce – User Manual
Radlabor GmbH | Heinrich-von-Stephan-Str. 5c | 79100 Freiburg | Germany
www.smartfit.bike | www.radlabor.de
1.3 Measuring Principle
The pedal force measuring device is built as an own mechanical construction which is mounted
between the crank and the pedal with an 12° forward rotation about the crank.
The system determines the magnetic field variations (Hall-Effect) because of the angular
displacement (~ 1/1000mm) of a small magnet in respect to a sensor.
Due to the specific circular construction of the force transmitting elements the applied force can be
divided into a radial and a tangential part. Positive tangential force (FT = Fe) is in the pedaling
direction and positive radial force (FR = Fu) is in the centrifugal direction. This principle allows every
pedal system to be screwed on.
12°
new (virtuell)
crank arm
pedal
PowerForce – User Manual
Radlabor GmbH | Heinrich-von-Stephan-Str. 5c | 79100 Freiburg | Germany
www.smartfit.bike | www.radlabor.de
1.4 Technical Data – Wireless edition
Mass of single sensor including radio: 370 g
Mass of receiver: 116 g
Measurement range: -500 up to 1500 N
Breaking load: ~3000 N
Sampling frequency pedal force: ~500 Hz
Wireless band: ISM Band: 2,4 GHz
Transmission distance:
Indoor: 3 – 5 m
Outdoor: 2 – 3 m
Battery Type: NiCd
800 mAh
Time for continual use: 6 – 8 h
Resolution: 12 Bit
PowerForce – User Manual
Radlabor GmbH | Heinrich-von-Stephan-Str. 5c | 79100 Freiburg | Germany
www.smartfit.bike | www.radlabor.de
2. After unpacking
✓ First read and follow these instructions!
✓ Unpack all materials very carefully!
✓ The PowerForce System is high sensitive electronic. So, handle all parts with highest
care
2.1 components
Check the content inside the suitcase
[1] 2x PowerForce sensor (left & right), with mounted transmitter (Accumulator included,
two protector caps mounted)
[2] 1x Base station (receiver)
[3] 1x Adjustment Tool
[4] 2x adjustment tools screws
[5] 2x crank – sensor screws
[6] 2x Accumulator Charger
[7] 1x Serial USB cable (Base station to PC)
[8] 1x USB License Dongle
[9] 1x 10mm Allen Key
[10] 1x 2,5mm Allen Key
[11] 1x 10mm Wrench
[12] 1x Calibration printout
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PowerForce – User Manual
Radlabor GmbH | Heinrich-von-Stephan-Str. 5c | 79100 Freiburg | Germany
www.smartfit.bike | www.radlabor.de
2.2 Mounting
To improve the measurement, it is important to fix the sensor in appropriate position on the ankle.
Before the mounting, make sure, that the adjustment screws are screwed out:
so, that the sensor has some space to move. Then mount the sensor on the crank:
PowerForce – User Manual
Radlabor GmbH | Heinrich-von-Stephan-Str. 5c | 79100 Freiburg | Germany
www.smartfit.bike | www.radlabor.de
Adjust the apex on the cone-bolt. Put the little bolts in the middle and fix the adjustment tool (hand-
tight) onto sensor, by using the corresponding screw for each site:
Put the cone of the adjustment tool into the center of the bottom bracket screw:
PowerForce – User Manual
Radlabor GmbH | Heinrich-von-Stephan-Str. 5c | 79100 Freiburg | Germany
www.smartfit.bike | www.radlabor.de
Then fix the sensor using the two adjustment screws. Tighten the screws alternating. It means first
a little the left, then a little the right, until the screws fixing the sensor in position.
Make sure, that the cone of the adjustment tool stays in the center of the bottom bracket screw:
After the adjustment screws fixing the sensor, tight the sensor – crank-screw:
Then you can take off the adjustment tool.
PowerForce – User Manual
Radlabor GmbH | Heinrich-von-Stephan-Str. 5c | 79100 Freiburg | Germany
www.smartfit.bike | www.radlabor.de
3. Software Installation
For the installation of the PowerForce software you need to download the software package on our
homepage:
http://www.smartfit.bike/en/download/
3.1 Install NI-DAQmx Driver
Before you install the IMAGO Record-Cycle Software, you must install the NI-DAQmx-Driver.
Click on the icon in the saved file and follow the setup instructions. The Installation will take some
minutes.
3.2 Install NI LabVIEW 2009 Runtime Engine Library
After installing the DAQmx Driver, you must install the NI LabVIEW Runtime Engine. This library is
necessary to read out the data from IMAGO.
Click on the icon and follow the setup instructions. The Installation will take some minutes.
3.3 Install IMAGO Records®
After the previous installation, you can install IMAGO Record. Therefore, you must open the
setup.exe and follow the setup instructions.
PowerForce – User Manual
Radlabor GmbH | Heinrich-von-Stephan-Str. 5c | 79100 Freiburg | Germany
www.smartfit.bike | www.radlabor.de
4. IMAGO Record®
4.1 Introduction
IMAGO® is a LabVIEW® based program developed at the University of Freiburg for data acquisition
and processing. The cycling lab (Radlabor®) out a lot of effort into the development of this software.
The PowerTec® measurement device and the IMAGO® software are developed parallel and are
therefore well concerted.
Besides force measurements, any other analogue channel can be recorded in IMAGO®. The program
also includes a processing routine. The data output from this routine is a MS Excel (2003) sheet
containing the mean of all recorded channels resampled to 360 data points (1° steps). It was
developed for movement analysis with the PowerTec® pedal force measurement system and EMG
recordings. For training and training studies the program provides an online feedback.
This feature, called “Cycle Plot” simplifies the data stream in a circular graph, to enable any athlete
to work with feedback without previous knowledge.
As the program has many more features used at the University, which are not available in your
version, there might be a few buttons and other options, which have no further relevance for pedal
force measurements. But as far as possible, they are hidden or deleted.
If you have any further questions, please contact the Radlabor®.
4.2 First start and setup
Start IMAGO Records by clicking on the Icon on your desktop.
Make sure, the USB-license dongle is in your PC, otherwise this error message may occur:
In this case close the program, insert the right dongle and restart IMAGO Records.
Your system firewall might want to block the application. You should allow the “Imago record.exe”
to pass the firewall.
PowerForce – User Manual
Radlabor GmbH | Heinrich-von-Stephan-Str. 5c | 79100 Freiburg | Germany
www.smartfit.bike | www.radlabor.de
On the first time, you start IMAGO two windows will open:
- The main record window (IMAGO record.vi)
- and a window with the overview of all channels (Wireless Cycling Instrument.vi).
4.2.1 Load Setup-files
To load the optimum setup files, you must click on setup.
Find the folder “record” on the following data path
Then you can insert the downloaded setup file called “RECORD_CYCLE1.set”.
After this step, the optimal set-up settings should be present in IMAGO.
PowerForce – User Manual
Radlabor GmbH | Heinrich-von-Stephan-Str. 5c | 79100 Freiburg | Germany
www.smartfit.bike | www.radlabor.de
4.2.2 Set, save and load calibration values
To enter the calibration parameters, you need the calibration protocol, which was attached to the
case. There you can see the offset settings and the correction values that were determined during
the calibration of your system in the Radlabor Company.
Now enter the, for your system, individual parameters in the “Wireless Cycling Instrument.VI” as seen
in the picture.
Note, that the gain for the power channels must be calculated with 500 𝑁
𝑉 to get from the voltage in
[V] to the force in [N].
Then press on the save button to save these parameters. You can find these settings under the file
path:
PowerForce – User Manual
Radlabor GmbH | Heinrich-von-Stephan-Str. 5c | 79100 Freiburg | Germany
www.smartfit.bike | www.radlabor.de
To have these settings at each start of IMAGO you need these “. set” files loaded in the “Read Write
Global Variables.VI”. You find this VI under the path:
Options Extras Paths
Then you must load the set files as shown in the picture:
After these adjustments, your system is ready to use.
PowerForce – User Manual
Radlabor GmbH | Heinrich-von-Stephan-Str. 5c | 79100 Freiburg | Germany
www.smartfit.bike | www.radlabor.de
4.3 Description of IMAGO®
The following chapters describe some of the most common functions in the analyze software
IMAGO Recors.
4.3.1 Main Menu
IMAGO
In this Tab, you are able to select the point, that IMAGO is always
selected. During the processing routine, some settings need to be
confirmed. But you can also let the system confirm most of the
automatically. To stop this automatism, you need to switch the
“Always Active” option.
Further here is the setting the page and for printing the actual window.
“Beenden” means to close IMAGO.
Tools
Via the Tab “Tools” you can do the Binary Export. You need this
binary export to transform your binary data in an excel readable
file format, e.g. for analyzing the separated force channels or the
acceleration channels.
Extras
Here you can select further options. If you click on it,
a window appears with four different index tabs.
In the tab “General” you can select your decimal separator, which is set to your Excel version. This
setting is dependent on your country and the way MS Excel reads decimal numbers.
PowerForce – User Manual
Radlabor GmbH | Heinrich-von-Stephan-Str. 5c | 79100 Freiburg | Germany
www.smartfit.bike | www.radlabor.de
Under “Recording” you can adjust some settings of the inserts of channels like the first channel of
the analog/digital-converter or the beginning position of your digital trigger channel.
In “Instruments” you can select different instruments- and wireless selections of the PowerForce
systems. But in usual case you should take the default selections.
The “paths” are already described in chapter 4.2.2.
Help
Via the “Help”-tab you have three selection
possibilities. If you select
WOZU KONTEXTHILFE?
If you select “About IMAGO”, you can check
which version of IMAGO you have.
Further you can see the key number of your USB-license-dongle.
Under “User Manual” you can call up further usage instructions for IMAGO Records. To this your PC
must be connected to the internet.
4.3.2 Index Tab
Via the Index Tab you can choose different viewing possibilities while the data acquisition.
Index tab Record
After the use of the “measurement” button you can follow the actual course of the curve in the
record-window. All selected channels are displayed in this window. By moving the bar on the left side
of the window you can change the viewing area.
PowerForce – User Manual
Radlabor GmbH | Heinrich-von-Stephan-Str. 5c | 79100 Freiburg | Germany
www.smartfit.bike | www.radlabor.de
Index tab cycle plot
The cycle plot window plots circular forces. An additional curve shows the summation of both force
signals.
Above the cycle plots you see different index tabs:
The power tab shows you the generated power of the left and the right leg, as well as their
summation.
In the settings, you can set the start angle, the crank length and the used data pieces.
Index tab Wireless
Before you start the measurement, it is recommended to check the wireless-connection of your
PowerForce system. So, you have an overview about the current wireless signals in [V], the base
station receives.
Under the wireless signals you see an overview about the arriving frequency samples. Usually they
are about 500 Hz (1). When you just turned on the System it takes a few seconds until the transmitter
is booted and the maximum sample frequency is reached.
Further you see a button for manual time correction and an overview about the number of connection
interrupts.
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