Patent ID: 11887780
Assignee: HITACHI HIGH-TECH CORPORATION
Field: Measurement (Instruments)
Classification: CPC H  B  G | IPC B  G  H

Claim 0:
1. A conveyance apparatus comprising:
a first magnetic body that is provided on a conveyance target object side;
two or more magnetic circuits, each including a core formed of a second magnetic body and a winding wound around an outer periphery of the core;
two or more drive circuits that are provided to correspond to the magnetic circuits one by one, each supplying a current to the winding;
two or more current detection units, each detecting a value of a current flowing in the winding; and
a computation unit that computes a position of the first magnetic body based on the current value detected by each of the current detection units, and controls the current supplied from each of the drive circuits to the winding on the basis of position information of the first magnetic body obtained by the computation,
wherein each of the current detection units is a resistor connected to the winding, and
the computation unit
controls the drive circuit to apply a pulse voltage having at least two or more different frequencies and detects a current from a voltage value of the resistor,
sets the pulse voltage applied to compute the position of the first magnetic body in the pulse voltage applied by the drive circuit, to be equal to or lower than a voltage used to drive the first magnetic body,
stores, in advance, a relational expression for determining a relation between a current waveform generated by the pulse voltage, and a distance, or table data for determining the relation between the current waveform and the distance, and
detects inductance from the current waveform and computes the position of the first magnetic body from any one or more of a difference in inductance between the adjacent windings, a slope of the inductance of each of the windings, and a value of the inductance.