[xavi]

(11-27-2013 05:28 PM)Nicola Wrote:  

(10-03-2013 05:37 AM)trener Wrote:  I found reason of problem - it was unstable soil!

I performed tests on artificial grass. I thought it's stable and solid enough, but obviously it has negative effect on flight time.

So my recommendation would be to be carefull when choose ground for testing.

Cheers

to make measurements on soil type grass you can use tools such as inertial sensors type Sensorize http://www.sensorize.it. They measure the height of the jump second protocol Bosco, or measure the height derived from the time of flight, but also also estimate the maximum height that the center of mass of an individual reaches. In addition, you will also have many other data related to the elongation phase of muscle shortening of the lower extremities in vertical jumps and much more ...

Systems with accelerometers like Sensorize, Humotion, Axlo, Keimove, Myotestor or Vertimetric don't need a platform. Usually they have the problem on detecting the start of the jump, but they are improving this. Another problem is accurate knowing jump height, because they rely on double-integration from acceleration to space, and this has an accumulated error. On the other hand, as the jump is a know movement and it's cinematic data is easy to model, they have algorithms to fix this error.

Another solution is infrared or laser platforms. They have to be very close to the floor and you have to take care that floor (grass) is not interfering. We are working on releasing one of this platforms because we don't like accelerometers.

Cheers.