Abstract: Backrest for supporting the back of a seated person comprising a rigid backrest frame and a back support structure comprising substantially non-elastic, flexible sheet material. The non-elastic, flexible sheet material comprising a central region and at least four lateral segments, wherein the backrest support surface in its loaded condition has a form-stable, a three-dimensionally curved shape of which a cross-sectional view in the sagittal plane shows a backrest support surface curvature. Preferably, this backrest support surface curvature corresponds with the vertebral curvature at least in a region which corresponding with the lumbar region and a transition region which is formed by a lower part of the thoracic region and an upper part of the lumbar region.

Abstract: Wheel assembly, in particular for a wheel chair comprising. The wheel assembly includes a wheel shaft extending along a shaft axis and which is configured to be non-rotatably connectable to a frame of the wheelchair. A wheel with a wheel hub is mounted on the wheel shaft so as to be rotatable around the shaft axis. The wheel assembly is provided with a hub motor having a power input and with a rim handle connected to the wheel and being rotatable relative to the wheel over an angle. A resolver assembly of the wheel assembly comprises a wheel resolver which is configured to generate a wheel resolver signal, a rim handle resolver which is configured to generate a rim handle resolver signal, and at least one resolver assembly output for outputting the wheel resolver signal and the rim handle resolver signal.