Patent ID: 6091215
Filing Date: 2000-07-18
Classification: B23K

Abstract:
A welding apparatus comprising:an electromagnetic actuator including a stationary member and a movable member adapted to be coupled to a workpiece to be welded, the actuator including at least one phase coil and a core, wherein the phase coil is positioned to establish a flux in the core when the phase coil is energized, and wherein the presence of flux in the core will tend to exert a force on the movable member, resulting in movement of the movable member;a force control system having an input that receives a desired force command and an output coupled to the phase coil, the force control system comprising:a flux observer that provides a flux feedback signal corresponding to the flux in the core;a flux controller coupled to the phase coil and to the flux observer, the flux controller receiving as inputs the flux feedback signal and a flux command signal, the flux controller providing to the phase coil a phase energization signal to energize the phase coil to increase the flux in the phase coil when the flux command signal is greater than the flux feedback signal and to energize the phase coil to decrease the flux in the control system when the flux feedback signal is greater than the flux command signal; anda force-to-flux controller having an output coupled to the flux controller, the force-to-flux controller receiving as an input a desired force command in a given reference frame and providing at the output the flux command signal wherein the force-to-flux controller converts the desired force command to the flux command signal based on the relationship between the forces associated with the movable member and the flux in the core;a position observed that provides at an output a position feedback signal corresponding to the instantaneous position of the movable member; anda position controller having a first input coupled to the output of the position observer and an output coupled to the input of the force controller, the position controller receiving as a second input a position command signal corresponding to the desired position of the movable member, wherein the position controller compares the position command signal with the position feedback signal and generates at its output a force command signal, wherein application of the force corresponding to the force command signal will tend to bring the movable member to the position corresponding to the position command signal.