EP2729815A2

EP2729815A2 - Device for measuring angle and angular velocity or distance and speed

Info

Publication number: EP2729815A2
Application number: EP12729975.8A
Authority: EP
Inventors: Heinrich Acker
Original assignee: Continental Teves AG and Co OHG
Current assignee: Continental Teves AG and Co OHG
Priority date: 2011-07-06
Filing date: 2012-06-26
Publication date: 2014-05-14
Also published as: WO2013004540A3; DE102011078717A1; US20140116132A1; CN103635811A; KR20140045539A; WO2013004540A2; CN103635811B; US9482687B2

Abstract

A device for measuring angle and angular velocity or distance and speed of a moving part is described. The device has a sensor which is or can be arranged in a stationary manner and an encoder which is or can be arranged on the moving part and, together with the sensor, generates a modulation signal to be demodulated by the sensor. For the frequency measurement which is needed to measure the angular velocity/speed, the encoder has a structure which reproduces a periodic pattern and is interrupted by at least one index area for the angle/distance measurement. In the index area, the encoder has a substitute pattern which differs from the periodic pattern by at least one physical variable which can be detected by the sensor but has a structure which also enables the frequency measurement in the index area.

Description

Device for measuring angle and angular velocity or path and velocity

The present invention relates to a device for Mes ^¬ solution of angle and angular velocity or displacement and Ge ^¬ speed of a moving part with a statio ^¬ nar arrangeable or arranged sensor and moving on to part arrangeable or arranged encoder, which together with the sensor is a generated by the sensor to be demodulated modulation signal, the encoder for the required angular velocity / speed measurement frequency measurement has a periodic pattern reflecting structure, which is interrupted by at least one index range for the angle / distance measurement.

Such devices are used both for linear travel and speed measurements and for angular and angular velocity or rotational speed measurements, whereby linear and, on the other hand, annular encoder are used. find a turn. The present invention relates to both types of measuring devices.

The measurement of a speed, which is required in the technology on many machines and systems, is physically synonymous with the measurement of the angular velocity. It is well known to measure the speed of waves by an encoder in the form of a periodic pattern is applied to the shaft on the circumference, for example, a tooth ^¬ wheel, which is scanned by a next to the shaft fixedly mounted sensor. The sensor has the ability to Zvi ^¬ rule tooth and tooth gap or other periodically changing properties or physical quantities such as magnetic field direction or optical transparency to distinguish. The sensor then generates an output signal having the same periodicity as the sampled pattern.

If an absolute position or an absolute angle to be detected in conjunction with rpm and throttle position / angular velocity measurement or speed measurement, it is known to use a separate, additional system having Anstel ^¬ le of the periodic pattern an index mark or a plurality of index marks. If the index mark is detected by the separate system, the sensor is at the index position, ie a position or an angle whose absolute value is known. The overall system can determine all of the following positions or angles by the change is detected on the basis of the index Posi ^¬ tion with the aid of the periodic pattern.

However, for cost reasons, for example in motor vehicle applications, a separate system is often used to Detection of an absolute position waived, although an absolute measurement is required. Then the periodic pattern of the angular velocity / velocity measurement system is interrupted at one point. From the interruption of the otherwise periodic signal sequence can thus close on the index position. The only prerequisite is a limitation of the acceleration or angular acceleration, so that an interruption of the signal sequence at the index position can be distinguished from the regular sequence with the strongest delay. This is common in technical applications due to the inertia of the systems or can be easily accomplished by choosing the parameters of the periodic pattern.

As mentioned, the periodic structure of the single En ^¬ coders must be interrupted at one point to avoid the cost of an additional system. This is done üb ^¬ SHORT- characterized in that the periodic structure of two periods is exposed to, for example the two missing teeth in the tooth row. The index position can thus be reliably detected. For the frequency measurement, which is required for the angular velocity / speed measurement, but a new problem arises because the frequency is now temporarily breaks and an interpolation and Extrapolati ^¬ onsverfahren is needed to be able to measure the frequency on the index away without the index mark provides an error contribution.

An interpolation is sufficient if the signal delay may be enter ^¬. If the output is instantaneous, extrapolation is required. The present invention has for its object to provide a cost-effective device of the specified type, which allows a particularly accurate angle ^¬ speed / speed measurement with a simple structure.

This object is achieved in a device of the specified type in that the encoder in the index region has a replacement pattern that differs from the periodic pattern by at least one detectable by the sensor physical ^¬ cal size, however, has a frequency measurement in the index range enabling structure.

The device designed according to the invention requires only one system with pattern and index mark and thus only one scanning sensor to perform both types of measurements. The device allows an absolute measurement by index marking and is further designed so that without In ^¬ terpolation or extrapolation an accurate frequency measurement across the index position can be made away. It goes without saying that the encoder here represents only a part of the measuring system and the scanning sensor is provided with the matching properties.

The present invention is based on the consideration not to interrupt the periodic pattern at the index mark or in the index area not completely (in the sense of an unstructured surface), but to replace it with another pattern. This replacement pattern has the property that it is clearly distinguishable from the periodic pattern by at least one property or physical quantity, but at the same time offers a structure that supports the Fre ^¬ quenzmessung. This support is that at certain positions or angles within the index range. Changes in the sensor signal occur, so that the frequency measurement in the index area on the real motion progress, rather than on an interpolation or extrapolation in the sense of continuing the movement that existed when entering the index area.

Since in the known procedure by interpolation or extrapolation the time of exit from the Indexbe ^¬ rich is not yet known, it can only be assumed there from the ^¬ movement state at the entrance, either by assuming a constant speed or by assuming a constant acceleration. The measurement uncertainty is therefore during the passage of the In ^¬ dexbereiches growing. In contrast, in the invention, the structure of the replacement pattern provides a remedy by the actual position (or the actual angle) within ^¬ half the index range is measurable.

The task of the sensor is to detect the transition between the periodic pattern and the replacement pattern, while the frequency measurement, which relies on the periodicity of the periodic pattern, is little or not disturbed. In this case, it is also possible, for example, to switch over between two measuring methods to be used in regions, one in the region of the periodic pattern, one in the index region.

Preferably, the sensor and encoder are formed in accordance with the invention formed a ^¬ a direction that a signal in the form of a modulated signal having a carrier frequency and two different modulated "news" for the index area and the remaining area of the encoder is generated. The sensor is in this case preferably Technically designed so that it extracts the carrier frequency and demodulates the transmitted "message".

Which is supplied (the physical converter) due to the action of the encoder from the sensor element, the signal is considered as a modulated signal, wherein the measure ^¬ de frequency (the speed or Winkelgeschwindig ^¬ ness represented) represents the carrier, the periodic pattern or the replacement pattern, on the other hand, two different modulated "messages." The sensor then has the task of extracting the carrier frequency and demodulating the "transmitted message". Depending on the modulation method very different circuit parts may be necessary. The sensor is therefore preferably designed according to the invention as a receiver for modulated signals according to known modulation ^¬ method with known receiver circuit concepts.

The inventively designed device (encoder with a corresponding sensor) can be used for the measurement of rotational movements and linear movements. In addition to general applications on any rotating shafts or linearly moving machine or vehicle parts, the following application areas are of particular importance: measurement on wheels of vehicles (wheel speed sensors), measurement on crankshafts of internal combustion engines, measurement on drive train components of motor vehicles, for example transmissions.

In a preferred embodiment of the invention, the periodic pattern is continuously present in the index area, but there with a different amplitude from the rest of the range. In this embodiment, an amplitude modulation (AM), in particular with a modular tion factor m <1 or an amplitude shift keying (ASK, Amplitude Shift Keying) use. In this embodiment of the invention, the periodic pattern is continuous EXISTING ^¬, but with a variable amplitude. The device for extracting the carrier is sensitive enough to work with both amplitudes, while the demodulation provides different binary values for the pattern and the replacement ^¬ pattern. For the practical embodiment of the Enco ^¬ earth electrode with different patterns amplitude example ^¬ example are: teeth of different length or shape, different material thickness, different material, different distance from the sensor element, etc.

In a further preferred embodiment of the device designed according to the invention, the periodic pattern in the index region is replaced by a similar pattern with a different frequency. Here comes a Frequenzmodula ^¬ tion (FM) or Frequenzumtastung (FSK, Frequency Shift

Keying). The periodic pattern is replaced in the index area by a similar pattern with a different frequency, in particular twice the frequency. In particular, with a digital circuit technology, it is easy to halve the double frequency in the index area in order to obtain a continuous frequency signal that is affected in any way by the Indexmar ^¬ cation. As in the embodiment described above, it is also possible to modify two periods of the pattern in this case. How many times will be modified, but is letztend ^¬ Lich irrelevant to the operation.

In still another embodiment of the invention, a pattern corresponding to a phase modulation is provided in the index area. In this embodiment, a phase senmodulation (PM) or phase shift keying (PSK) for use. For example, in this case a tooth is offset by 90 ° in the grid of the other teeth and causes an inverted binary signal at a suitable demodulator. The advantage over AM (ASK) and FM (FSK) consists in the lower requirements for the amplitude of the signal. While in AM two distinctly different Amplitu ^¬ must be processed directly and the FM - depending on the physical implementation - different amplitudes can be Doomed? ^¬ gently by a frequency dependence of the sensitivity is at PM no need for a related reserve. In the present exporting ^¬ approximately form a dislocation is only one pattern period considered preferred because a particularly high apparent temporal frequency change is caused (Pha ^¬ senverschiebung by 90 °, then immediately, starting from the new instantaneous value, to -90 °), which particularly easy to separate from rotation ^¬ number changes.

Thus a device for measurement of angle and angular velocity or displacement and VELOCITY ^¬ ness according to the invention is provided which comprises an encoder and an associated sensor. Other circuit parts, if any erfor ^¬ sary are not described here. Their arrangement is at the discretion of the skilled person. Encoder and sensor erzeu ^¬ gen together a modulation signal from the sensor to demo ^¬ demodulate. The carrier is extracted for frequency measurement. The demodulated signal is used to find ei ^¬ ner or more, the same or different index marks that are used for an absolute path or angle measurement. The corresponding modulation is generated by the encoder, namely by structuring any physical quantity along the measuring direction. The sensor sets a structuring corresponding demodulation method to find the index marks. Due to the modulation, the frequency measurement is not or only slightly ^{impaired ¬} .

As used herein, "sensor" therefore refers to the actual sensor element, which generates along with the En ^¬ coder the signal and the associated signal processing tung / evaluation unit. For these parts be ^¬ known elements / circuits may find use.

By the sensor (sensor element) detectable physical groE ^¬ SSE may be of any nature, for example the geometric type (tooth / tooth surface), magnetic type or optical type. The invention in any case all possible types of detectable physical quantities.

For modulation, preferably the following methods are used: AM (ASK), FM (FSK), PM (PSK), sub and hybrid digital modulation methods such as QAM (Quadrature Amplitude Modulation), QPSK (Quadrature Phase Shift Keying), 4-PSK, 8-PSK, 16 -QAM etc. (several bits per symbol, attractive for distinguishing many index marks), because of the close relationship also pulse modulation methods (partly from the signal image not to be distinguished from PSK), such as PPM (pulse-pause modulation, pulse-phase modulation) and for cases with analog signal processing (less circuitry, but generally preferred if possible), AM, FM, PM.

It should be noted that the method according to the prior art, wherein the periodic pattern of a Sys tems ^¬ easily at a location (index portion) interrupted can also be considered as amplitude modulation (AM) with the modulation factor m = 1 or as OOK (on-off keying). This procedure or ^variant of the method of the prior art is not covered by the invention, since the invention expressly requires a replacement pattern in the index range.

The encoder is preferably designed as a permanent magnetic encoder.

The invention will be explained below with reference to Ausführungsbei ^¬ games in conjunction with the drawings in detail. Show it:

Figure 1 is a schematic representation of an encoder mold according to the prior art;

Figure 2 is a schematic representation of an encoder mold according to a first embodiment of the invention;

Figure 3 is a schematic representation of an encoder mold according to a second embodiment of the invention;

Figure 4 is a schematic representation of an encoder mold according to a third embodiment of the invention; and

Figure 5 is a schematic representation of a device for measuring angle and Winkelge ^¬ speed (speed). The reproduced in Figures 1-4 encoder forms are shown linearly for reasons of simplicity of drawing. However, the structure of the encoder along the measurement coordinate also applies to ring-shaped encoders. The presentation then corresponds to a corresponding settlement. The direction of movement is indicated by the arrow.

The selected schematic representations of the encoder shapes are not concerned with the exact geometry of the respective pattern, but merely exemplify the representation of tooth and tooth space as such. The difference ^¬ Liche nature of encoders, ie the physical quantity modulated within the pattern is, this is not betrach ^¬ tet. All modulating quantities, whether geometrical, magnetic, optical or otherwise, are exemplarily symbolized by tooth and tooth space.

The representation of the encoder forms always shows only one index mark. A variation only as required, parameters or type of index mark within an encoder is mög ^¬ Lich.

Furthermore, no details are given in the embodiments for the formation of the respective sensor. In particular, the procedure is in the demodulation not described in individual ^¬ nen, but it is given only to dial the modulation method. The carrier frequency and the demodulated signal are then located at the two outputs of the circuit considered to be known.

5 shows a device for angular and Winkelge ^¬ schwindigkeitsmessung is shown schematically. The device has a on the surface of a rotating Tei ^¬ les, for example a shaft 1, arranged Encoder 2 and a stationary sensor 3 arranged adjacent to the encoder. The encoder 2 has a structure representing a periodic pattern, which may be, for example, individual teeth. The intended index range is not specifically shown here.

Figure 1 shows an encoder according to the prior art. The figure shows a series of teeth which form a periodic ^pattern 4, wherein in an index region 5 two teeth are missing.

Figure 2 shows a first embodiment of the invention in which the encoder in turn has a series of teeth forming a periodic pattern 4. In this case, five teeth 2 are provided in the Indexbe ^¬ rich 5 with a shorter length, so that in this embodiment, the amplitude modulation described above (AM) with a modulation factor m <1 may find application.

In the embodiment of Figure 3, the encoder has a series of teeth, which also form a periodic pattern 4, wherein here in the index region 5 a similar tooth pattern 7 with double frequency is present. In this device, as described above Frequenzmodu ^¬ lation (FM) applies.

In the case of the encoder shown in FIG. 4, the periodic tooth pattern 4 in the index region 5 has a tooth 8 offset by 90 ° in the raster from the other teeth. In this embodiment, takes the above-described Pha ^¬ senmodulation (PM) application.

Claims

claims

1. Device for measuring the angle and angular velocity or displacement and velocity of a bewe ^¬ constricting portion with a stationary arrangeable or arranged sensor and moving on to part arrangeable or arranged encoder, which together with the sensor is a from the sensor to be demodulated Modulati ^¬ onssignal wherein the encoder for the angular velocity / velocity measurement required frequency measurement has a periodic pattern reproducing structure, which is interrupted by at least one index range for the angle / displacement measurement, characterized in that the encoder (2) in the index area (5) a includes replacement pattern from the periodic pattern (4) detectable by at least one from sensor (3) physical quantity failed ^¬ det, but a frequency measurement in the index region (5) has enabling structure.

2. Device according to claim 1, characterized in that sensor (3) and encoder (2) are formed so that a modulated signal with a carrier frequency and two different modulated "messages" for the index area (5) and the remaining area of the encoder (2) is generated.

3. Device according to claim 2, characterized in that the sensor (3) is circuitically designed so that it extracts the carrier frequency and demodulates the transmitted "message".

4. Device according to one of the preceding claims, characterized in that the periodic pattern (4) continuously in the index region (5) is present, but there with deviating amplitude, in particular un ^¬ ferent tooth length or tooth shape, different material thickness, different material, different Distance to the sensor element, opposite to the remaining area.

5. Device according to one of claims 1 to 3, characterized in that the periodic pattern (4) in the In ^¬ dexbereich (5) is replaced by a similar pattern (7) with a different frequency.

6. Device according to one of claims 1 to 3, characterized in that in the index region (5) a Pha ^¬ senmodulation corresponding pattern is provided.

7. Device according to one of the preceding claims, characterized in that it serves for speed measurement.

8. Device according to one of the preceding claims, characterized in that the periodic pattern (4) is formed by a series of juxtaposed equidistant teeth whose shape, number and / or position in the index region (5) from the periodic pattern (4 ) deviates.

9. Device according to one of the preceding claims, characterized in that the encoder is designed as a permanent ^¬ magnetic encoder.