Linear Direct Drive with Inductive Energy Transmission

Linear direct drives, which based on the electrodynamic operating principle, are designed with a moving coil or magnet system. The advantage of such a system with moving magnets is the unnecessity for current supply at the armature, while its disadvantage lies in the increased material and control effort caused by the coils in the stator. Those drives with a moving coil system have higher dynamics due to a lower moving mass, but in turn require the power supply to be carried along. Trailing cables, which also carry the cable for data transmission, are used for longer travel ranges. As an additional disturbance due to its length and weight, the trailing cable is a mechanical component, which limits the dynamics and positioning accuracy. It also increases the sensitivity to cable breakage. A moving coil system with inductive energy transmission makes the trailing cables superfluous and benefits from the higher dynamics as well as from the prevention of cable breakage. This paper presents a concept that enables a linear direct drive to be powered wirelessly. The energy transfer takes place inductively according to the transformer principle. As a coaxial transformer, an inductive coupling is established between a stationary primary coil and a moving secondary coil via a toroidal ferrite. This allows the armature with toroidal core and secondary coil without mechanical contact. The control and power electronics are mounted entirely on the armature. Creating a linear direct drive with a moving coil system, that can be operated without a trailing cable and with position control.