Projets:Perso:2012:controler
Contents
Main Issue
We are trying here to find a solution to our most important technical issue in powerchair football, "over heating", or the fact that after a while, the chairs starts to slow down and this has a huge impact on their way to play the game.
The hypothesis we want to check for now is that the "over heating" phenomenon is due to a temerature rise in the controler , that triggers a "safety mode", which slows the chair down. This has to be verified.
We are currently using 400W motors, with 2X80A controlers. Electronics are made by Dynamic control a New zealand brand owned by an american disability products company, Invacare.
motor controler
Subset Audit
- 2 mosfets half bridges ceach composed with 8 transistors. - current measure by "DC" current sniffer
[To be completed]
In situation controler behaviour analysis
The first idea we had was to observe the behaviour of the chair in play, to understand what is really going on.
That would mean to concomitamently measure physical data la battery voltage, the battery current and the motor controler temerature.
Temperature Measures
a thermocouple is available but the acquisition module we plan on using also accepts PT100 and RTD. http://www.omega.com/prodinfo/rtd.html We can also use a silicium sensor like the KTY81-121 with R25 = 990 Ohms and which varies from 700 Ohms between 20 and 100°C Tmax = 150°C : a simple spreadsheet can then convert it into temperature.
Current measure
200A Shunt available
other measures
The acquisition module we plab on using has numerous channels (20 maybe more, it os possible to do simultenaous measures more thorough than the measures we mentioned earlier. For exemple we can do several temperature measures on the controler, the motors, PWM equivalent voltage, etc.
Acquisition en situation
L'alim de la centrale d'acquisition est "à transformateur" sur 230V : on peut mettre un petit onduleur 150VA pour faire le 230V sur le fauteuil : mais l'onduleur dispo fait du carré, donc pas simple.
Quatre orientations:
- soit ça passe avec le 230V carré (= voir si le transfo s'échauffe pas trop, sachant qu'un essai dure 10 minutes)
- soit on filtre le carré, mais faire un filtre 50Hz qui coupe assez raide vers 70Hz est une véritable gageuse
- soit on trouve un petit onduleur sinus
- soit, on se limite à 2 canaux (tension batterie, température contrôleur), et dans ce cas un scope portable sur batterie fera l'affaire.
Un oscillo ne mesurant que des tensions, il faut utiliser un convertisseur thermocouple -> tension/courant ou PT100 -> tension/courant [dispo] pour faciliter l'enregistrement des données de température. Exemple d'un utre convertisseur température-tension avec sa sonde : http://www.gsamart.com/webdata/prodimg/FLU_e0007903_lg.jpg
Possibilité de faire évoluer le contrôleur moteur
Quelques questions en suspens pour le moment :
- Est ce vraiment le contrôleur qui provoque la chauffe? (la réponse doit venir de l'audit en situation)
- nous avons des contrôleurs de 60A, est il possible de les passer "facilement" à 80A (économie importante à réaliser)?
