6.2 Signals of the Muscles and Motions

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0

1

2

3

4

5

6

7

8

9

10

Time t/s

300

400

500

Force F/N

a) Raw Force data

Force

0

1

2

3

4

5

6

7

8

9

Time t/s

60

80

100

120

140

160

Angle /°

b) Raw Angle data

Angle

0

1

2

3

4

5

6

7

8

9

10

Time t/s

300

400

500

Force F/N

c) Force Data with Threshold and Start and End Points of Local Minima

Force under Threshold

Force Raw

Threshold

Local Minima Start

Local Minima End

0

1

2

3

4

5

6

7

8

9

Time t/s

0

100

200

Angle /°

d) Angle Data with Threshold and Start and End Points of Local Minima

Angle under Threshold

Angle Raw

Threshold

Local Minima Start

Local Minima End

0

1

2

3

4

5

6

7

8

9

10

Time t/s

300

400

500

Force F/N

100

200

300

Angle /°

e) Force and Angle data with corresponding trigger points

Force

Force Trigger Point

Angle

Angle Trigger Point

0

1

2

3

4

5

6

7

8

9

10

Time t/s

300

400

500

Force F/N

100

200

300

Angle /°

f) Synchronised Force and Angle Data

Force

Force Trigger Point

Angle

Angle Trigger Point

Fig. 6.13: Application of a threshold and average procedure with biomechanical conditions (the

number of local minima as characteristic pattern in the force and joint angle data of the three knee

bends); the second and third stand phase as synchronisation features.

local minima for knee joint angle and the force data the points which are required for

the synchronisation of both data sets, the so called trigger points, are calculated. Due

to the characteristic pattern of the force curve the two trigger points in the standing

phases are between the second and the third local minimum and the fourth and fifth

local minimum (cf. Figure 6.11).

To determine the first trigger point (TP1) the average of the time of the first force

value (x Local Minima Start) in the third local minimum (cf. Figure 6.13, c) and the time

of the last force value (o Local Minima End) in the second local minimum is calculated.

To determine the second trigger point (TP2) the average of the time of the first force

value (x Local Minima Start) in the fifth local minimum (cf. Figure 6.13, c) and the time

of the last force value (o Local Minima End) in the fourth local minimum is calculated.

The resulting trigger points are shown as upward pointing triangles in Figure 6.13, (e).