A wheelchair includes a pivoting drive assembly having a drive wheel, a motor drive connected to the drive wheel, and a first pivoting linkage fixedly attached to the motor drive. The pivoting drive assembly is pivotally coupled to a frame at a first frame pivot axis such that the drive wheel, motor...http://www.google.co.uk/patents/US8172015?utm_source=gb-gplus-sharePatent US8172015 - Wheelchair suspension
