Mitutoyo Corporation

Andermotion Technologies LLC

Micro Encoder, Inc.

Nils Ingvar Andermo

Karl G Masreliez

Kim W Atherton

David Skurnik

Patrick H Mawet

Kurt E Steinke

Mark L Delany

Philip S Lane

Tracy E Hanley

Various alternative embodiments of a multi-turn capacitive encoder device are disclosed. The device includes two members that are fixed relative to each other and that include respective capacitive electrodes that are capacitively coupled between the two members. The respective capacitive electrodes on one member act as transmitter electrodes and the respective capacitive electrodes on the other member act as receiver electrodes. One or more modulation members are relatively movable between the two fixed members to alter or modulate the capacitive coupling to correspond to the rotational or angular position of the modulation member(s). At least one of the modulation members is driven using a gear reduction system such that its angular or rotational position corresponds to a plurality of turns of the input shaft of the multi-turn encoder. A plurality of signals that depend on the capacitive coupling are used to determine the rotational or angular position of the modulation member(s) relative to the first two members. The present invention combines the elements outlined above to provide a multiturn encoder including few parts, simple assembly, a small axial dimension, and relatively high resolution and accuracy.

Low-profile multi-turn encoder systems and methods

A capacitive encoder includes a signal-balanced shield electrode configuration that does not require electrical ground connection or active sensing and control in order to maintain the shield electrode(s) at a sufficiently constant voltage during capacitive position measurements. The shield electrode configuration is positioned in a capacitive coupling gap between transmitter electrodes and receiver electrodes during operation. The shield electrode configuration is patterned in a manner that complements the layout of the transmitter electrodes, such that the shield electrode configuration inherently floats at a nominally constant electrical potential when coupled to the signals present on the transmitter electrodes. The resulting capacitive encoder is thus more economical to build, convenient to install, and reliable during operation than capacitive encoders which use an electrical connection, compensation drive circuitry, or grounding in order to control the potential of a shield member that operates at a potential that is not inherently constant.

Single-balanced shield electrode configuration for use in capacitive displacement sensing systems and methods

A reduced offset absolute position transducer has at least one magnetic field generator that generates a first changing magnetic flux in a first flux region. A plurality of coupling loops have a first plurality of coupling loop portions spaced at a first wavelength along a measuring axis and a second plurality of coupling loop portions spaced at a second wavelength along a measuring axis. One of the first plurality of coupling loop portions and the second plurality of coupling loop portions are inductively coupled to a first changing magnetic flux from a transmitter winding in a first flux region to generate a second changing magnetic flux outside the first flux region in the other of the first plurality of coupling loop portions and the second plurality of coupling loop portions. A magnetic flux sensor is positioned outside the first flux region and is responsive to the second changing magnetic flux to generate a position-dependent output signal. The output signal varies at the first or second wavelength of the corresponding other of the first plurality of coupling loop portions and the second plurality of coupling loop portions that generates the second changing magnetic flux.

Reduced offset high accuracy induced current absolute position transducer

An inductive absolute position sensor has at least one magnetic field generator that generates a first changing magnetic flux in a first flux region. A plurality of coupling loops have a first plurality of coupling loop portions spaced at an interval related to a first wavelength along a measuring axis and a second plurality of coupling loop portions spaced at an interval related to a second wavelength along a measuring axis. One of the first plurality of coupling loop portions and the second plurality of coupling loop portions are inductively coupled to a first changing magnetic flux from a transmitter winding in a first flux region to generate a second changing magnetic flux outside the first flux region in the other of the first plurality of coupling loop portions and the second plurality of coupling loop portions. A magnetic flux sensor is positioned outside the first flux region and is responsive to the second changing magnetic flux to generate a position-dependent output signal. The output signal varies at the first or second wavelength of the corresponding other of the first plurality of coupling loop portions and the second plurality of coupling loop portions that generates the second changing magnetic flux.

The invention provides a method of sampling precision measurement signals to achieve an accurate measurement position at a particular measurement time, such that the measurement accuracy is unaffected by the velocity of motion. The method involves sampling each signal during a predetermined sampling period such that a signal from one sensor is sampled first, a signal from a second sensor sampled second, etc., and then the signals are sampled in reverse order such that the first signal sampled is sampled last. These sampled signals are averaged and produce a precision measurement at a time measured at one-half of the sampling time. In addition, this method can be applied to the use of separate scale tracks where each scale track is alternately sampled, or alternatively, where one scale track is sampled in the middle of the sampling period of another scale track.

Symmetric sampling

An absolute position transducer system has two members movable relative to each other and includes a code track transducer and at least one fine wavelength transducer. The code track is arranged to form a sequential pattern of base-N code words, where N is greater than two (i.e., non-binary). Each sequential non-binary code word identifies an absolute position of one member with respect to the other at a first resolution. Alternatively, the code track is arranged to form a pseudo-random non-binary code word pattern. In this case, the transducer system compares a non-binary code word with a look-up table to determine an absolute position of one member with respect to the other at a first resolution. In order to generate a non-binary code word pattern, code track transducer employs different-sized flux disrupters, different-sized flux enhancers, or a combination of flux disrupters and enhancers.

Absolute position transducer having a non-binary code-track-type scale

Methods and systems for calibrating an absolute position encoder where a read head is moved relative to a scale of the absolute position encoder and the absolute position encoder is comprised of a fine scale and a coarse scale. An absolute position of a coarse scale is determined which corresponds to the measurement in a fine wavelength. An ideal coarse absolute position is determined from the fine scale measurements. A deviation between the determined coarse absolute position and the ideal coarse absolute position is then determined. The mean of the maximum positive and negative deviations from the ideal coarse scale absolute position for different intervals of the scale are then stored for the entirety of a measured range. These stored correction values are then used to correct the coarse scale values. The concept can be utilized also in a system with more than two wavelengths, for instance a fine wavelength, a medium wavelength and a coarse wavelength.

Systems and methods for calibrating an absolute position encoder

A high-accuracy inductive absolute position transducer system has two members movable relative to each other and includes a code track transducer and may include a fine track transducer. The code track transducers includes a code track transmitter winding and at least one set of code track receiver windings. Each set of code track receiver windings includes n balanced pairs. Each balanced pair extends along the measuring axis and includes a positive polarity winding and a negative polarity winding. A code track has a plurality of flux modulator zones distributed along the measuring axis. Flux modulators are formed in at least some of the flux modulator zones. A signal generating and processing circuit is connected to the transmitter winding and each balanced pair. The code track transmitter winding and each balanced pair form an inductive coupling. The flux modulators modulate the inductive coupling between each balanced pair and the code track transmitter winding based on the relative position between the read head member and the scale member. The flux modulators are distributed along the measuring axis such that each pair of adjacent flux modulator zones forms one of a set of output states in an overlying balanced pair. The pairs of adjacent flux modulator zones form a series of code elements extending along the measuring axis such that each set of m adjacent code elements forms a unique codeword. Each unique codeword defines an absolute position of the read head member relative to the scale member to a first resolution.

Induced current absolute position transducer method using a

An electronic linear scale having a reduced offset position transducer that uses at least one coupling loop on a scale to inductively couple a transmitter winding on a read head to one or more receiver windings on the read head. The transmitter winding generates at least one primary magnetic field. The transmitter winding is inductively coupled to first loop portions of the coupling loops by the primary magnetic field. Second loop portions of the coupling loops generate secondary magnetic fields. Each receiver winding is inductively coupled to the second loop portions of the coupling loops by the secondary magnetic fields. At least one of the transmitter winding or the receiver windings is formed in a periodic pattern complementary to the dimensions of the coupling loops. Prescribed winding configurations are used to reduce the effects of extraneous inductive coupling in the device. Depending on the relative position between the read head and the scale, the receiver windings inductively couple to the second loop portions of the coupling loops to various degrees. A compact, high accuracy, high resolution inductive position sensor results. Low power operation is possible.

Electronic linear scale using a reduced offset high accuracy induced

A self-calibrating position transducer system and method uses the position transducer itself as a position reference during calibration, thus eliminating using an external reference during calibration. The transducer signals are sampled at a plurality of evenly-spaced positions within each sampled scale wavelength, using the transducer itself as a position reference. The calibration values for the DC signal offsets, the amplitudes and non-orthogonality of the fundamental signals, the amplitudes of the signal harmonic components and position offsets are then determined using Fourier analysis techniques. The transducer signals are corrected using the determined calibration values, which are in turn used to revise the stored calibration values in anticipation of the next calibration operation. The self-calibrating position transducer uses the stored calibration values to enhance its accuracy.

Self-calibrating position transducer system and method

An inductive transducer system for use in high accuracy applications such as linear or rotary encoders, employs two members movable relative to each other. A first, active member induces eddy currents in a second, passive member that lacks a power source or electrical wires connected thereto. The first, active member contains both a transmitter for generating a magnetic field and a receiver for receiving the field. The receiver has a plurality of symmetric loops. Electronic circuitry coupled to the receiver evaluates the relative position between the two members as the passive member disrupts the magnetic field received by the receiver. The inductive transducer can be readily manufactured using known printed circuit board technology, and is substantially immune to contamination by particles, including ferromagnetic particles, oil, water and other fluids. A pulse-driven drive circuit allows the inductive transducer to consume little power, and thus allows the transducer to be readily incorporated into hand-held, battery-powered measurement tools.

Induced current position transducer having a low power electronic circuit

A reduced offset position transducer uses at least one coupling loop on a scale to inductively couple a transmitter winding on a read head to one or more receiver windings on the read head. The transmitter winding generates at least one primary magnetic field. The transmitter winding is inductively coupled to first loop portions of the coupling loops by the primary magnetic field. Second loop portions of the coupling loops generate secondary magnetic fields. Each receiver winding is inductively coupled to the second loop portions of the coupling loops by the secondary magnetic fields. At least one of the transmitter winding or the receiver windings is formed in a periodic pattern complementary to the dimensions of the coupling loops. Prescribed winding configurations are used to reduce the effects of extraneous inductive coupling in the device. Depending on the relative position between the read head and the scale, the receiver windings inductively couple to the second loop portions of the coupling loops to various degrees. A compact, high accuracy, high resolution inductive position sensor results. Low power operation is possible.

Reduced offset high accuracy induced current position transducer

An electronic linear scale, which uses an induced current position transducer, includes a slider assembly mounted adjacent to an elongated beam. The slider assembly is mounted on one mounting member of a device such as a machine tool. The elongated beam is mounted on a second mounting member of the device. The first and second mounting members move relative to each other. The position of the slider assembly on the beam is indicative to of the position between the first and second mounting members. Relative movement is determined by an inductive read head mounted on the slider assembly that couples to flux modulators on the beam. The read head includes a transmitter winding and a pair of receiver windings, preferably fabricated in a planar form, carried by a common printed circuit board. The flux modulators, which can include flux disrupters and/or flux enhancers, are carried by the beam and modulate the magnetic fields produced by the transmitter. Thus, the receiver windings produce output voltages corresponding to the overlap between the modulators and the receiver windings. Signal processing electronics are connected to the read head and determine the relative positions of the first and second mounting members by monitoring the output of the receiver windings. A digital display displays the determined position. The relatively insensitive nature of the induced current position transducer to contaminants allows the linear scale to function with improved reliability when operating in industrial environments. Low power operation of the linear scale is possible.

Electronic linear scale using a self-contained, low-power inductive

A pitch-compensated induced current position transducer includes a scale having a plurality of scale elements arranged along a measuring axis and a read head positioned adjacent to and movable relative to the scale. The read head has a transmitter winding that generates a changing magnetic field and at least one receiver winding. One of the transmitter winding and receiver winding is formed from a spatially modulated section having an associated phase. The spatially modulated section has flux coupling areas distributed relative to a plurality of polarity zones. The spatially modulated section has at least one pitch balancing section. In one type of pitch balancing section the positive polarity winding loops and the negative polarity winding loops have their centroid axes aligned. The total flux coupling area in at least one polarity zone may optionally be different than the total flux coupling area in an adjacent polarity zone while the total negative flux coupling area remains equal to the total positive flux coupling area. In general, the pitch balancing sections are configured so that the overall centroids of all spatially modulated sections are aligned along the measuring axis. The distribution of the flux coupling area may be symmetrical.

Pitch-compensated induced current position transducer

An electronic caliper using a low power induced current position transducer includes a slider assembly mounted on an elongated beam with first and second measuring jaws projecting from the main beam and slider assembly. The position of the slider assembly on the beam is indicative of the distance between the first and second jaws. A depth bar is also attached to, and projects from, the slider assembly. Relative movement between the measuring jaws is determined by an inductive read head mounted on the slider assembly that couples to flux modulators on the beam. The read head includes a transmitter winding and a pair of receiver windings carried by a common printed circuit board. The flux modulators, which can include both flux disrupters and flux enhancers, are carried by the beam and modulate the magnetic fields produced by the transmitter. Thus, the receiver windings produce output voltages corresponding to the overlap between the modulators and the receiver windings. Signal processing electronics are connected to the read head and determine the relative positions of the jaws by monitoring the output of the receiver windings. A digital display displays the determined position. In one embodiment, either flux enhancers or flux disrupters are used. In another embodiment, both flux disrupters and flux enhancers are used. The relatively insensitive nature of the low power induced current position transducer to industrial contaminants allows the caliper to function with improved reliability when operating in traditional shop environments.

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Kirkland, WA, United States of America

Nils Ingvar Andermo