Abstract: The present invention is related to a motor system, a motor, and to a robot arm device comprising the same. According to the invention, a motor is provided comprising a rack having a periodic surface thereon which is engaged by a plurality of engaging elements. By driving the engaging elements back and forth towards the surface structure in a periodic and time shifted manner, a linear motion can be brought about.

Abstract: The invention is related to a method for generating hardness and/or strain information of a tissue which can be subject to a varying pressure, the method comprising: —positioning at least one signal transmitter (1) outside the tissue (10); —positioning at least one signal receiver (1) outside the tissue (10); —using the signal transmitter (1) to send signals (S) at different angles towards the tissue; —using the signal receiver (1) to receive signals from the tissue (10), wherein the received signals result from the signals that have been sent by said signal transmitter. The invention is also related to an apparatus for carrying out the method.