degrees before then falling again to zero at 90 u00b0 thus energy storage and release from the spring only occurs between 270 u00b0 and 90 u00b0 in other embodiments this region may be narrower for example it may extend from around 290 u00b0 to 70 u00b0 a plot of the total rotor torque against its rotational position corresponding to the configuration of fig1 and 13 is shown in fig1 it can be seen that the bias cam profile of fig1 facilitates provision of stable rest positions 400 as shown in fig1 defined by passive magnetic force between the rotor and the stator an actuation cam displacement graph and cam profile 422 for use in combination with the bias cam profile of fig1 are depicted in fig1 and 16 respectively it can be seen that the displacement is zero between 270 u00b0 and 90 u00b0 continuing clockwise from 90 u00b0 it increases to a maximum at 180 u00b0 before then decreasing again down to zero at 270 u00b0 in this configuration one or more of the rotor positions at 90 u00b0 180 u00b0 and 270 u00b0 may be denoted as primary rest positions each of these stable rest positions 400 at 135 u00b0 180 u00b0 and 225 u00b0 may represent u201c second rest positions u201d in the context of the present application an actuator.