An absolute encoder configured to, when a rotation range of a measurement target member is limited by a brake mechanism, generate an AB-phase signal and a Z-phase signal for calculating a rotation angle of the measurement target member. The absolute encoder includes a brake mechanism, a plurality of Z-phase-signal-detection-target portions each having a Z-phase-signal-rise-detection-target portion and a Z-phase-signal-fall-detection-target portion, a plurality of AB-phase-signal-detection-target portions each located between a Z-phase-signal-rise-detection-target portion and a Z-phase-signal-fall-detection-target portion that are adjacent to each other in a circumferential direction, to thereby form a plurality of restriction ranges each including at least one of the Z-phase-signal-rise-detection-target portions and at least one of the Z-phase-signal-fall-detection-target portions. An interval in the circumferential direction between a Z-phase-signal-rise-detection-target portion and a Z-phase-signal-fall-detection-target portion that are adjacent to each other in the circumferential direction is different among the plurality of restriction ranges.

A position encoder comprises: a first and second member, with the first member movable relative to the second member; a first sensor arranged at one of the first or second members, and a first track arranged at the other one of the first or second members such that the first sensor moves along the first track when the first member moves relative to the second member, with the first sensor capturing at least one of its position or displacement along the first track; a second sensor arranged at one of the first or second members, and a second track arranged at the other one of the first or second members such that the second sensor moves along the second track when the first member moves relative to the second member, with the second sensor capturing at least one of its position or displacement along the second track.

Apparatus and associated methods relate to cascaded sets of two or more individual permanent magnets distributed in a predetermined spatial relationship on a source carrier configured to translate proximate two or more magnetic field sensors distributed in a predetermined spatial relationship on a reference carrier. In an illustrative example, the permanent magnets may be arranged in at least two predetermined orientations. For example, each of the permanent magnets may direct its field in a predetermined orientation to produce a unique output code from a set of the magnetic field sensors. The output code may, for example, uniquely identify a relative position between the source carrier and the reference carrier. The magnetic field sensors may be, for example, anisotropic magneto-resistive elements. Cascaded sets of permanent magnets may cost-effectively increase the dynamic range of the relative position between the source carrier and the reference carrier by adding additional magnetic targets.

A method of operating a position encoder apparatus, including a scale having features defining position information and a readhead for reading the scale. The method includes: calculating extrapolated position information from at least one previous reading of the scale; comparing an extrapolated position with a position calculated from a reading of the scale to determine any discrepancy between them; using the extrapolated position information whether or not there is a discrepancy; and maintaining a record of any discrepancies.

An absolute position sensor having a detector with a plurality of Wiegand wire sensors that each have a pair of Hall sensors bracketing or straddling the Wiegand wire used by a processor in interpolating relative ratios of signals from the bracketing Hall sensors in not only providing increased fine position determination between magnets but also providing coarse position count increment or decrement verification. Such an absolute position sensor provides increased fine position determination accuracy while also enhancing increment and/or decrement error prevention and/or correction during position sensor operation.

There is provided an absolute encoder advantageous in accuracy of an output thereof against a defect in a scale thereof. In the absolute encoder, a detector detects a part of an array of marks of the scale, and outputs a data sequence corresponding to the part. A processor stores information indicating a correspondence between each of a plurality of code sequences and an absolute coordinate of motion of the scale, and outputs information of the absolute coordinate based on the data sequence and the information. The processor detects an error of the data sequence, and performs rewriting of the information based on the detected error.

A system and method for determining information related to a rotation of a shaft. The method includes receiving a signal associated with a plurality of targets and gaps passing by a sensor. The targets and gaps are positioned around a circumference of a wheel that is fixed for rotation with the shaft. The method includes forming a sensed target-and-gap sequence based on the signal, wherein the sensed target-and-gap sequence represents a subset of the targets and gaps. The method further includes comparing the sensed target-and-gap sequence to a set of known target-and-gap sequences stored in memory. Each known target-and-gap sequence is associated with a respective known circumferential portion of the wheel. The method also includes determining which respective, known target-and-gap sequence is identical to the sensed target-and-gap sequence.

A rotary coding disc and a method for designing the same is applied to an optical encoder. N-bit De Bruijn sequences include 1 and 0. The N-bit De Bruijn sequence has the maximum binary code and the minimum binary code. When a binary code having M bits is located between the maximum binary code and the minimum binary code, the corresponding N-bit De Bruijn sequences are selected as diagonal De Bruijn sequences, wherein $\frac{2^N-2N}{2}-\frac{N}{2}<M<\frac{2^N-2N}{2}+\frac{N}{2}.$
The De Bruijn sequence may be converted into a De Bruijn energy level. The total number of 1 consecutively neighboring 0 and (N−1) consecutively neighboring N of the De Bruijn energy level is calculated. The transparent areas and the opaque areas are located based on the De Bruijn sequence or the De Bruijn energy level that corresponds to the total number less than or equal to N.

A vernier sensor including a coarse sensor and a fine sensor may require calibration to ensure accurate position measurements. Calibration may include determining coefficients for harmonics that can be added to the coarse sensor output and the fine sensor output to reduce harmonic distortion. The disclosure describes using the offset and variance of a difference signal as the basis for calibration. This approach is possible at least because the frequencies of the coarse sensor and fine sensor can be selected to reduce the complexity of these calculations.

A magnetic sensor is provided with first and second magnetoresistive effect elements that can detect an external magnetic field. The first and second magnetoresistive effect elements are a plurality of layers of multilayer body including free layers where their magnetization directions vary due to the external magnetic field. Shapes of the first and second magnetoresistive effect elements viewed from the upper side in the lamination direction are different from each other. The first magnetoresistive effect element has a shape that can increase a slope of an output of the first magnetoresistive effect element relative to the change of the external magnetic field. The second magnetoresistive effect element has a shape that can decrease a slope of an output of the second magnetoresistive effect element relative to the change of the external magnetic field compared to the slope of the output of the first magnetoresistive effect element.