Rotary Joints and Modulo Axes

Modulo axes are only allowed for rotary joints of kinematics. These are rotary joints for which SMKinematicWithInfo.GetAxisProperties returns the value props.eType = Axis_Type.Rotary. If a modulo axis is used for a linear joint or for a kinematic which does not implement ISMKinematicWithInfo, then MC_GroupEnable returns the SMC_MODULO_AXIS_FOR_NON_ROTARY_JOINT error. If a modulo axis is used and the kinematics limit the range of a rotary joint, then MC_GroupEnable returns the SMC_MODULO_AXIS_FOR_LIMITED_ROTARY_JOINT error.

Modulo axes are supported only if the modulo period is 360°. The reason for this is that axes connected to rotary joints have to be configured is such a way that one technical unit [u] corresponds to one angular degree [°]. One period has to correspond to one full rotation. If a modulo axis with a period other than 360° is used, then MC_GroupEnable returns the SMC_MODULO_AXIS_PERIOD_NOT_360 error.

As of version 4.12.0.0, SoftMotion supports only the shortest mode (MC_DIRECTION). This means that the distance and direction of a modulo axis are selected is such a way that they are as close as possible to the start position of the axis. For example, if the orientation axis is at a2 = 30° at the beginning of the movement and at a2 = 290° at the target position, then the position a2 = 290° – 360° = –70° is selected and the axis moves 100° in the negative direction instead of moving 260° in the positive direction.