Biomechanikstudy_MRI_AKT-O_EN.pd - VACOped

Pressure distribution measurement vacopedes 2004Mathematical summary of load analysis1. The sensor i measures the pressure p i (t) at each point in time t in thecourse of rolling the foot,2. Each individual pressure sensor i, is geometrically assigned a representativearea a i (cf. Fig. 13), pressure p i (t) times area a i results in the force exerted onthis partial area,3. The total force F total in the standing phase is determined by the body weightM of the test person (in kg)F total= M · g ,g = 9.8msec 24. The summation of the pressure values of all sensors multiplied by theirrepresented area must also result, in the middle part of the standing phase,in the body weight (cf. Fig. 14), and a scaling factor s is introduced for thispurpose so that:all _ sensorsF total= M · g = s · ∑ a i · p i(t)iand.:all _ sensorss = (M · g )/(∑a i · p i(t))i(since the total force also varies somewhat in the middle standing phase, anaverage value is formed),5. So that the load on partial areas of the foot sole can now be calculated foreach point in time t:Sensors in the partial areaF part(t ) = s · ∑ a i · p i (t )i6. If the partial force F part is integrated over the period of time of the groundcontact, this results in the overall load (the impulse K) in this area:Lifingt footK part= ∫ F part · dtt = Putting foot down7. The overall measurement time is divided into individual step cycles. Anaverage step cycle is formed from these individual sequences. This averagingout can in principle be performed at almost any point in the entire procedure:If it is for example performed straight after point 1, you will obtain averagepressure profiles for individual sensors.Page 12