DE19822843A1 - Method to determine angular position or velocity of rotating shaft or axle, for use with IC engine - Google Patents

Abstract

A coded disc (54) is fixed to the axle (52). The disc has incremental angular sensors (10) that generate a sinusoidal analogue signal, which is sampled using an ADC to convert it to digital form.The digital values are filtered and normalized in an analysis unit and compared with stored reference values to produce high-resolution angular position data.- DETAILED DESCRIPTION - An INDEPENDENT CLAIM is made for a circuit arrangement for making high resolution angular position measurements of a rotating axle

Description

The invention relates to a method and circuit order for high-resolution determination of the angle of rotation position and / or speed of a shaft, in particular the crankshaft or camshaft of an internal combustion engine.

It is known to detect angles of rotation, angles of rotation sensors or encoders to use, one with Um Catch marks provided with the measuring shaft rotatably connected coding disk and a stationary sensor have, which the contactless scanning of Markers provides a periodic analog signal. The Analog signal converted into digital pulses and the rotation angle information obtained by pulse counting. Which he Reachable resolution is therefore due to the angular distance of the markings on the coding disk, where un ter taking into account the required mechanical Stability or service life and the required low Manufacturing effort no significant resolution increases are possible. A higher resolution ana logen signal processing stands in the way that the ampli tud of the sampled signals especially when on strong interference in the area of motor technology  such as speed and temperature fluctuations as well as drifters appearances are subject.

Based on this, the object of the invention reasons, an insensitive process and a corresponding arrangement for high-resolution determination of rotation angle information, with which at low construction effort of the rotation angle sensor even with rough hem measuring operation accurate and even when changing the measuring reproducible measurement results obtained who the.

To solve this problem, according to the invention indicated in independent claims 1 and 11 NEN combinations of features proposed. Beneficial Refinements and developments of the invention ben from the dependent claims.

The invention is based on the idea of a di gital amplitude evaluation of the detected sensor signals in connection with stored reference data an increase in resolution and at the same time an error rate enable rectification. The procedure is accordingly proposed solution of the aforementioned task conditions that a rotatably connected to the shaft, in order markings arranged in a distributed direction on the circumferential direction send coding disk to generate a when scanning of the markings in a respective sampling cycle are sinu soidal varying analog signal is sampled, the  Analog signal using an analog / digital converter in a variety of digital values in each sampling cycle is implemented sequentially, and through the digital values an evaluation unit prepared arithmetically and with in a storage medium, a respective one Angle position of the shaft assigned reference data be compared. By a suitable choice of the clock rate of the analog / digital converter can be compared the simple pulse counting considerable resolution achieve increases, with the mathematical Processing of measurement data interference effects on simple Way can be corrected and compared with Reference data a compensation of manufacturing tolerance zen of the coding disk allowed.

In order to change the amplitude, especially with differ Chen measuring conditions, it is from Advantage if the digital values are linked by a predetermined correction value arithmetically to a the amplitude adapted to the reference data are normalized. This can be easily achieved by that the correction value is given from the ratio of one calibration value and one from the digital values determined effective or integral value is determined.

According to a preferred embodiment, the digital values are converted bipolar into positive and negative half-periods in a given sampling cycle and assigned to the four quadrants of a harmonic oscillation by linking them with their time derivative. This means that the digital values can be clearly distinguished from one another in each sampling period, even with the same amount of their analog signal amplitudes. It also makes it possible to obtain information about the angular position even in a marking gap on the coding disk. For these purposes, it is particularly favorable if the stands from at predetermined Zeitab t _i consecutively detected digital values f f (t _i) a processed waveform. (T _i) according to the relationship

f. (t _i ) = f (t _i ) / f '(t _i )

is determined, where f '(t _i ) means the time derivative of f (t).

To determine the absolute angular position of the Allow shaft with respect to a fixed bearing Chen, can be caused by a gap in the Win mark spacing from each other Coding disc generated gap signal evaluated who the.

For clear, cycle-by-cycle assignment of the digital values to the markings on the coding disc and one thereby possible tolerance compensation, it is advantageous if from the analog signal or digital derived from it sizes by evaluating characteristic signal progression  fe like zero crossings the number of sampling cycles continues is determined continuously.

For obtaining the angle of rotation information even under different test setups, it is advantageous if the Reference data through reference measurements at given Angular positions of the shaft from detected ge if necessary, determined averaged digital values and as value pairs in fixed assignment to the respective Angle of rotation position can be saved. It is advantageous in this context, a multi-dimensional background supply, the reference data depending on meas parameters such as shaft speed or ambient temperature parameterized and recorded in the form of a table or reference function can be saved.

Another advantageous embodiment of the invention provides that the mo. determined from the digital values mental angular position and / or speed of the shaft via a digital / analog converter as an analog signal a display unit, for example an oscilloscope, for the possible execution of real-time examinations is issued.

With regard to a device, the task set out at the outset is achieved by combining the following features:

• - A rotation angle sensor for generating a during scanning most of the marks in a respective scan cycle  klus sinusoidally varying analog signal, which a rotatably connected to the shaft, with in Um markings arranged in the direction of the circumference has coding disc,
• - An analog / digital converter for sequential implementation zen of the analog signal into a variety of digital value in each sampling cycle, and
• - An electronic evaluation unit, the preparation means for arithmetic processing of the digi Tal values and comparison means for comparing the prepared digital values with in a memory tel deposited, a respective angle of rotation position has reference data assigned to the shaft.

To a first approximation of the angular velocity To obtain an independent measurement signal, the rotary kelsensor a Hall generator, a field plate or egg NEN magnetoresistive cooler as a signal generator, and the marks on the coding disc are as the magne table flux density in a containing the signal generator magnetic circle changing teeth or recesses educated. In principle, an optical one can also be used here Donors should be provided. To determine absolute win The data are the markings on the coding disc in the Finished angular distance from each other, where due to a missing marking one of a given one absolute angular position of the shaft corresponding gap  is formed.

To eliminate interference, it is advantageous if the processing means program routines for fil include and normalize the digital values. Here can the evaluation unit by a program routine formed digital film formed as a bandpass filter ter for preferably speed-dependent filtering of the Di have capital values.

To specify a time base for the digital values and in order to set the resolution, it is provided that the evaluation unit one with a predetermined Clock operating clock to control the Ana log / digital converter.

For clear assignment of the markings when scanning digital values recorded as a sine curve proper angular positions, it is advantageous if the Analog / digital converter or a downstream on unit for bipolar or DC voltage-free implementation of the analog signal and the evaluation means for differentiating the in chronological order has detected digital values.

A rough determination of the current angular position is made by a to which the analog signal can be applied and responsive to a predetermined threshold, Com. connected on the output side to the evaluation unit  parator for generating assigned scan cycles digital increment signals.

To the high computing required for real-time measurements To provide performance, the evaluation unit as digital signal processor, as an application-oriented Hardwired semiconductor device (ASIC) or as Programmable semiconductor gate arrangement formed be. It is also conceivable here that the evaluation unit thanks to a microprocessor with suitably high processing speed is formed.

Another preferred embodiment of the invention provides before that the evaluation unit for control, regulation or triggering especially of the internal combustion engine associated external units at least one synchro nization output. It is also advantageous if the evaluation unit has at least one input for Feeding of external operating conditions, in particular Engine functions assigned to the internal combustion engine Has measurement signals.

To exercise tax functions and additional evaluations to be able to carry out in off-line operation if necessary NEN, is advantageously a preferably Mi krocontroller or personal computer trained Kon troll unit provided for the transmission of Measurement data preferably via a dual-port RAM with the  Evaluation unit is connected.

For the investigation of vibration processes, in particular Torsional vibrations, it is advantageous if on the Shaft two rotation angle sensors at an axial distance of are arranged one another.

In the following the invention is based on one in the Drawing shown in a schematic manner example explained in more detail. Show it

Figure 1 is a block diagram of a circuit arrangement for high-resolution determination of the angle of rotation position or speed of a shaft.

Figure 2 is a rotation angle sensor of the circuit arrangement with a non-rotatably connected with the shaft encoder.

Fig. 3 is a diagram of the temporal course of the analog signal detected by the rotation angle sensor;

Fig. 4 is a timing diagram of the converted and filtered digital values in discrete time intervals, and

Fig. 5 is a diagram of the temporal course of computing severally processed digital values.

The circuit arrangement shown in the drawing serves to supplement high-resolution digital speed and angle information and includes a sinusoidal analog signal providing incremental angle sensor 10 , a connected via an upstream measuring amplifier 12 with the angle sensor 10 connected NEN analog / digital converter 14 and a processing device 16, an input side to the Ana log / digital converter 14 coupled via a parallel input bus 18, a digital signal processor to comprehensive evaluation unit 20 and a dual-port RAM 22 and a control bus 24 to the evaluation unit 20 connected to the microcontroller 26 has.

To feed a digital incremental signal a be connected to the analog signal of the rotational angle sensor 10 aufschlagbarer comparator 28 is connected to an input of the evaluation unit 20 is connected. Via a further digital input 30 , measurement signals assigned to external operating states can be fed into the evaluation unit 20 for correlation with the rotation angle information. The momentary rotational angle position and / or rotational speed determined by means of the evaluation unit 20 can be output to a display unit 38 via an output bus 32 , a digital / analog converter 34 and a downstream output amplifier 36 . A digital output 40 of the evaluation unit 20 is used to control, regulate or trigger external units.

The microcontroller 26 enables offline evaluation of the measurement data provided by the evaluation unit 20 via the RAM 22 . In addition, control commands, configuration data and measurement event data can be transmitted between the microcontroller 26 and the evaluation unit 20 via the control bus 24 . External systems can be coupled to the microcontroller 26 via bus interfaces (e.g. CAN bus 42 , RS232 interface 44 ) as well as via digital control inputs 46 and outputs 48 . An LED display 50 enables simple display of status and operating mode information.

The rotation angle sensor 10 shown in FIG. 2 has a coding disk 54 connected to the measuring shaft 52 in a rotationally fixed manner, which interacts via circumferential markings 56 with a signal generator 58 , for example, as a Hall generator. The markings 56 shown for the sake of simplicity are formed by radial edge recesses which are arranged in the circumferential direction of the coding disk at the same angular distance from one another. Due to a missing marking 56 , a gap 60 is formed at a circumferential point of the coding disk 54 , which enables ei ne absolute rotation angle determination. When running around cause the markings 56 in a magnetic circuit closed by the fixed fixed signal generator 58 , temporal changes in the magnetic flux density, which are reflected in a sinusoidal curve of the analog signal supplied by the signal generator. Because of this magnetogalvanic coupling, the signal amplitude is independent of the speed of the encoder disk 54 . Each mark 56 can be assigned a period in the analog signal and accordingly a sampling cycle.

Fig. 3 shows the time course of the thus obtained analog signal S (t). Whose amplitude is subject to fluctuations depending on measurement parameters such as the ambient temperature and can be superimposed by interference. The individual periods or scanning cycles can vary due to the angular tolerances of the markings 56 . When the gap 60 passes, a gap signal 62 arises corresponding to a missing signal period. For digital detection of the analog signal, the analog / digital converter 14 is driven at a predetermined clock rate 1 / t _i by means of a clock generator (not shown), as a result of which the achievable angular resolution is determined at a given speed n of the shaft 52 .

The digital values sampled sequentially at time intervals t _i are computationally processed in the evaluation unit 20 . In a first preparation step, the digital values are digitally filtered by a preparation stage 64 , a bandpass filter being implemented in software by a suitable program routine. The filtered digital values f (t _i ) thus obtained and shown in FIG. 4 can then be normalized in a further processing step in order to compensate for amplitude fluctuations. In a simple amplitude standardization, it is provided that the digital values f (t _i ) are divided by a correction value, which is formed from the effective value ratio between the data f (t _i ) and a predetermined effective value. As an alternative or in addition, standardized digital values f. (T _i ) can be calculated according to the relationship

f. (t _i ) = f (t _i ) / f '(t _i )

are determined, with f '(t _i ) being the time derivative of f (t) obtained by a differentiation routine. It should be taken into account here that the digi tal values are determined in a given sampling cycle in positive and negative half-periods without DC voltage. A corresponding signal curve is shown in FIG. 5 for two signal periods containing the gap signal 62 , the values f. (T _i ) between the transition points 66 marking the inflection points of f '(t _i ) increasing monotonously. In this way, the digital values can be unambiguously assigned to the four quadrants of the sampled sine wave on the basis of the respective signs of the signal profiles f (t _i ) and f. (T _i ) in each sampling interval.

To determine the angle of rotation information contained in the processed digital values, these are compared by comparison means 68 of the evaluation unit 20 with reference data stored in a storage means 70 . The reference data are recorded by previous reference measurements at predetermined rotational angle positions of the shaft 52 in the manner described above and stored as a so-called template in the form of a table or an analytical reference function. External measurement parameters can be taken into account by appropriately parameterized, multidimensional reference data acquisition. The reference data can represent a complete revolution of the shaft 52 or, in the case of existing signal periodicity, only a corresponding sector section. In order to obtain a clear cycle-wise assignment of the reference data and the digital values to the markings 56 of the coding disk 54 , the scanned markings 56 are continuously counted by evaluating the zero crossings of the digital values or on the basis of the increment signal supplied by the comparator 28 . It is thus possible, by comparing the values between the sampled digital values and the reference data, to determine the corresponding angle of rotation α of the shaft 52 and to calculate the associated instantaneous speed, taking into account the sampling time t _i .

The principle of rotation angle and speed detection described above opens up advantageous application possibilities, especially in the field of control technology for internal combustion engines. Here, switching times of the quantity solenoid valves or the injection times of the injection nozzles queried via the input 30 can be set in relation to the rotation angle information sensed by means of one or more rotation angle sensors 10 on the crankshaft or camshaft. At the same time, it is also possible, by outputting control signals via the output 40 , to control or regulate engine functions which are dependent on the rotation angle, such as the start of injection, the ignition timing, the closing and opening angles.

In summary, the following can be stated: The invention relates to a method and a circuit arrangement for determining the rotational angle position and / or rotational speed of a shaft 52 . For this purpose, by means of an egg ne-rotatably connected to the shaft encoder 54 having incremental shaft angle sensor 10, a si nusförmig varying analog signal is sampled and converted into digital values by an analog / digital converter fourteenth The digital values can be processed arithmetically in an electronic evaluation unit 20 by suitable filter and standardization routines 64 , 68 and compared with reference data stored in a storage means 70 in order to obtain high-resolution rotation angle information in this way.

Claims (23)

1. A method for high-resolution determination of the rotational angle position and / or speed of a shaft ( 52 ), in particular the crankshaft or camshaft of an internal combustion engine, in which a rotationally fixed to the shaft ( 52 ) connected in the circumferential direction ver arranged marks ( 56 ) having Co dierscheibe ( 54 ) to generate a when scanning the markings ( 56 ) in a respective scanning cycle sinusoidally varying analog signal is sampled, the analog signal by means of an analog / digital converter ( 14 ) sequentially into a plurality of digital values in each sampling cycle is implemented, and the digital values are processed arithmetically by an evaluation unit ( 20 ) and compared with reference data stored in a storage means ( 70 ) and assigned to a respective rotational angle position of the shaft ( 52 ). 2. The method according to claim 1, characterized in that that the digital values by linking with a predetermined correction value arithmetically on a the amplitude adapted to the reference data is normalized the. 3. The method according to claim 2, characterized in that that the correction value from the ratio of one before given calibration value and one from the digital  value determined effective or integral value is true. 4. The method according to any one of claims 1 to 3, characterized characterized in that the digital values in a bipolar scanning cycle in positive and negati ven half-periods implemented and by linking with their time derivative of the four quadrants can be assigned to a harmonic vibration. 5. The method according to any one of claims 1 to 4, characterized in that from the stands in predetermined Zeitab t _i consecutively detected digital values f (t _i) a processed waveform f. (T _i) according to the relationship
f. (t _i ) = f (t _i ) / f '(t _i )
is determined, where f '(t _i ) means the time derivative of f (t). 6. The method according to any one of claims 1 to 5, characterized in that for determining the absolute angular position of the shaft ( 52 ) by a gap ( 60 ) at a defined angular distance from each other marks ( 56 ) of the coding disk ( 54 ) generated gap signal ( 62 ) is evaluated. 7. The method according to any one of claims 1 to 6, characterized in that from the analog signal or from derived digital quantities by evaluating cha characteristic signal waveforms such as zero crossings, the number of sampling cycles for the clear cycle assigning the digital values to the markings ( 56 ) of the coding disk ( 54 ) is determined continuously. 8. The method according to any one of claims 1 to 7, characterized in that the reference data by reference measurements at predetermined rotational angle positions of the shaft ( 52 ) from the detected, given, if any, averaged digital values are determined and stored as pairs of values in a fixed assignment to the respective rotational angle position . 9. The method according to any one of claims 1 to 8, characterized in that the reference data in dependence speed of measurement parameters such as the speed of the shaft ( 52 ) or ambient temperature is detected parameterized and saved in the form of a table or reference function. 10. The method according to any one of claims 1 to 9, characterized in that the instantaneous angular position and / or rotational speed of the shaft ( 52 ) averaged from the digital values via a digital / analog converter ( 34 ) as an analog signal on a display unit ( 38 ) is output. 11. Circuit arrangement for the high-resolution determination of the angle of rotation position and / or speed of a shaft ( 52 ), in particular the crankshaft or camshaft of an internal combustion engine, with a non-rotatably connectable to the shaft ( 52 ), with markings ( 56 ) distributed in the circumferential direction. verse hene coding disc ( 54 ) having rotation angle sensor ( 10 ) for generating an analog signal when scanning the markings ( 56 ) in a respective scanning cycle si nusoidally varying, an analogue / digital converter ( 14 ) for sequentially converting the analog signal into a plurality of digital values in each sampling cycle, and an electronic evaluation unit ( 20 ), the processing means ( 64 ) for processing the digital values and comparing means ( 68 ) for comparing the processed digital values with a respective rotational angle position of the shaft stored in a storage means ( 70 ) ( 52 ) assigned reference data. 12. Circuit arrangement according to claim 11, characterized in that the angle of rotation sensor ( 10 ) has a Hall generator, a field plate or a magneto-resistive sensor as a signal generator ( 58 ), and that the markings of the coding disc ( 54 ) as the magnetic flux density in one signal generators are formed (58) containing magnetic changing teeth or recesses (56) circuit. 13. Circuit arrangement according to claim 11 or 12, characterized in that the markings ( 56 ) of the coding disc ( 54 ) are arranged at a defined angular distance from one another, with a missing absolute marking of a predetermined absolute angular position of the shaft ( 52 ) gap ( 60 ) is formed. 14. Circuit arrangement according to one of claims 11 to 13, characterized in that the processing means ( 64 ) include program routines for filtering and nor ming the digital values. 15. Circuit arrangement according to one of claims 11 to 17, characterized in that the evaluation unit ( 20 ) has a formed by a program routine, designed as a bandpass filter digital filter for preferably speed-dependent filtering of the digital values. 16. Circuit arrangement according to one of claims 11 to 15, characterized in that the evaluation unit ( 20 ) has a clock for controlling the analog / digital converter ( 14 ) with a predetermined sampling rate. 17. Circuit arrangement according to one of claims 11 to 16, characterized in that the analog / digital converter ( 14 ) is designed for bipolar conversion of the analog signal, and that the evaluation unit ( 20 ) has means for differentiating the digital values recorded in chronological order. 18. Circuit arrangement according to one of claims 11 to 17, characterized by a loadable with the analog signal and len len on a predetermined threshold, on the output side with the evaluation unit ( 20 ) connected comparator ( 28 ) for generating digital incremental signals associated with the sampling cycles. 19. Circuit arrangement according to one of claims 11 to 18, characterized in that the evaluation unit ( 20 ) is designed as a digital signal processor, as an application-oriented hard-wired semiconductor component (ASIC) or as a programmable semiconductor gate arrangement. 20. Circuit arrangement according to one of claims 11 to 19, characterized in that the evaluation unit ( 20 ) has at least one synchronization output ( 40 ) for controlling, regulating or triggering in particular the internal combustion engine associated external units. 21. Circuit arrangement according to one of claims 11 to 20, characterized in that the evaluation unit ( 20 ) has at least one input ( 30 ) for feeding in external operating states, in particular motor functions assigned to the internal combustion engine, measurement signals. 22. Circuit arrangement according to one of claims 11 to 21, characterized by a control unit ( 26 ) which is preferably designed as a microcontroller or personal computer and which is connected to the evaluation unit ( 20 ) for the transmission of measurement data, preferably via a dual-port RAM ( 22 ) . 23. Circuit arrangement according to one of claims 11 to 22, characterized in that on the shaft ( 52 ) two rotation angle sensors ( 10 ) are arranged at an axial distance from one another.