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6 Applications and Methods in Biosignal Processing

Fig. 6.10: Superimposed curves of the total force and the knee angle of the second knee bend; force

(lined) and knee angle (dotted); spreading of the seven phases.

6.

P6: Moment of inertia phase – further reduced support of muscle force

7.

P7: Deceleration of the upward movement – activation of muscle force and center

of mass slowed to halt

In preliminary assessments it appeared that the second upright stand phase between

the first and the second knee bend as well as the third upright stand phase between

the second and the third knee bend would be a well attribute for synchronisation [36].

In these two stand phases the patients have two physical releases between the knee

bends which result in a roughly symmetric part of the force curve in these two sections.

These characteristics of the force signal provide an attribute for the development of a

synchronisation algorithm.

The joint angle achieves his maximal value in the upright stand phase whereas

the total force achieves approximately the body weight of the patient. Sometimes there

would be a local minimum in the peak of the upright stand phase [36], but in the pa-

tient data a clear maximum is apparent. These characteristic properties of the force

curve in the second and third upright stand phase are suitable for the determination

of two instants of time for the synchronisation (cf. Figure 6.11). There is the possibility

to use these two upright stand phases as features for the superimposition of the force

and the angle curve in the algorithm development.