Ebara Corporation

Shinichi Moriyama

Katsuhide Watanabe

Naoji Hiraki

Yoichi Kanemitsu

Hiroyuki Shinozaki

Takahide Haga

A magnetic levitation control apparatus comprises a pair of electromagnets for holding a levitated body having a magnetic body in the levitated state. A signal source for supplying a voltage signal of a frequency on a level such that enables the electromagnets to function as the position sensor, wherein a control voltage signal for controlling the magnetic attraction of the electromagnets is superimposed on the voltage signal. A circuit differentially supplies the voltage signal to the pair of electromagnets to form a position signal of the levitated body from an add signal of currents respectively from the electromagnets, and a circuit detects a control current of the electromagnets from a subtraction signal of currents respectively from the electromagnets. A controller generates a control voltage signal of the electromagnets from the detected position signal of the levitated body and, in addition, corrects the position signal detected from the detected control current of the electromagnets.

Magnetic levitation control apparatus

A displacement sensor system is provided which is capable of simultaneously and independently detecting displacements in two directions orthogonal to an axis of an object to be detected, using a less number of displacement sensors than before. The displacement sensor system, for enabling the simultaneous detection of displacements in two directions orthogonal to an axial direction of a pillar-shaped member, has a plurality of displacement sensors positioned around the pillar-shaped member, and a detector circuit for receiving outputs of the plurality of displacement sensors to output signals indicative of displacements in the two directions orthogonal to the axial direction of the pillar-shaped member. The detector circuit includes a multi-bridge circuit for parallelly connecting a circuit having the plurality of displacement sensors connected in series to a plurality of resistor circuits. In one embodiment of the present invention, the pillar-shaped member has a square prism portion, and the plurality of displacement sensors include four displacement sensors, where the displacement sensors are positioned in a plane parallel to a set of opposite surfaces of the square prism portion and in the vicinity of four corners of the square prism portion, respectively. The four displacement sensors are connected in series to form an inductance circuit which constitutes a part of the multi-bridge circuit.

Inductive displacement sensor system detecting displacements in two

A control system for controlling a linear actuator including magnetic bearings for levitating a robot arm and a pulse motor for linearly driving the arm in a non-contact manner is disclosed, which comprises a displacement detection unit including displacement sensors, first and second calculation units, moving amount detection unit and adding circuit. The displacement detection unit detects displacement values of the arm from a reference posture, the first calculation unit calculates guiding (y), levitation (z), roll (p), pitching (q), and yaw (r) control current values in response to the displacement values and provides guiding, levitation, roll, pitching, and yaw control current signals (, , , , ). The moving amount detecting circuit detects a moving amount (X.sub.0) of the arm from a reference position in response to an operation of the pulse motor, and provides a compensation current value (.DELTA.Iq') proportional to the moving amount, and the adding circuit adds the compensation current value (.DELTA.Iq') to the pitching control current signal (). The second calculation unit, in response to the guiding, levitation, roll and yaw control current signals (, , , ) and the added pitching control current signal (+.DELTA.Iq'), calculates drive current control values to compensate drive current flowing through the magnetic bearings.

Control system for a linear actuator including magnetic bearings for

A robot with no mechanically contacting components are suitable for use in special environments such as semiconductor manufacturing processes where dust and lubrication are matters of important concern. The robot has a linear actuator composed of magnetic bearings and a linear motor for moving a robot arm linearly without mechanical contact, and a rotary actuator composed of magnetic bearings and a rotary motor for rotating a body which supports the linear actuator, around the rotary actuator without mechanical contact.

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Iizuka, Japan

Shinichi Moriyama