DE4402319A1 - Measurement system for relative movement of oppositely movable bodies - Google Patents

Abstract

One part e.g. of a telescopic damper has regions (111,111') with different magnetic properties arranged along a track (b) and monitored by Hall effect transducers (11,12) which are immovable w.r.t. the other part and produce signals (S1,S2) corresp. to variations in magnetic flux density, phase-offset from each other by 90 deg..These signals and that of a third transducer (13) are conditioned (101) and processed (120) to produce a coarse output corresp. to the number of regions detected in passing, and a fine output corresp. to the flux variation within one region.

Description

State of the art

The invention relates to a movement system for a device two mutually displaceable bodies.

On the prior art, for example from the article "lengths and Incremental Angle: Limits of Accuracy "(Journal Electronics, 3/2. 2. 90, page 88) is known to have lengths and angles to measure optical, inductive or magnetic way. Especially is known to incrementally lengths and angles, d. H. counting to capture sen. For this purpose, rotary encoders and angle measuring devices are used as measured value recordings for rotary movements and connections with threaded spindles or Racks are used for linear motion measurements.

Furthermore, it is known from the prior art that for Design of the chassis of a motor vehicle powerful Suspension systems between the wheel units and the vehicle body are to be provided. Such suspension systems exist in the case of one semi-active suspension control system generally from a spring arrangement with fixed spring constants, that of a damping device  is connected in parallel with adjustable damping. Such dampers with adjustable damping characteristics, for example be realized that the damper piston with a throttle valve is equipped, the flow cross section of the throttle valve is changeable. Damper in their damping characteristics are adjustable, for example in DE-OS 33 04 815 and described in DE-OS 36 44 447. In chassis control systems is generally the essential input variable of the spring deflection or the spring travel speed, d. H. the distance between that Vehicle body and the wheels or its change over time. In addition there are inexpensive and robust spring deflection or spring deflection speed sensors necessary.

Furthermore, for the design of vehicle dynamics control systems or steering systems (front / rear wheel steering systems) in motor vehicles Information regarding the transverse and / or yaw movements is required. Because these movements are indirect or direct with the steering movement related to the vehicle are inexpensive and robust Steering angle and / or steering angle speed sensors necessary.

In the article "Speed detection with a differential HALL IC" (Zeitschrift Elektronik 4/1991, page 86) are magnetic field sensors and sensor evaluation circuits described.

Advantages of the invention

In its general form, the invention relates to a system for measuring solution of the relative movements of two bodies. In possible form The invention can use the two bodies as a suspension system be formed of a motor vehicle chassis, the one body connected to the vehicle body and the other body with a wheel is. In this case, the relative movements described above leveling movements measured. In a further embodiment  can according to the invention the steering movements in a motor vehicle can be measured by one body with the steering shaft and the other whose body is connected to the vehicle-mounted steering housing. Vastness re advantageous applications of the invention are in use with an electrically or hydraulically operated clutch or Throttle valve actuator can be seen in motor vehicles. Independent of the use of the system according to the invention, the invention Advantage of an inexpensive, robust and accurate motion measurement too enable. The system is inexpensive primarily because inexpensive magnetic field sensors are used, the robustness of the Systems results, for example, from the fact that the system is relative is insensitive to temperature, the achievable accuracy of the system is particularly high because the sensor signals are incremental (Coarse signals) and analog (fine signal) can be evaluated.

According to the invention, the motion measuring system for a device with two mutually displaceable bodies to capture one Position of the first body relative to the second body from that

• - The first body has zones that have different magnetic Possess properties, and
• - The zones are arranged in at least one track, and
• - At least one sensor unit is provided, which is relative to the second body is immovably arranged and which by the Zones of the track caused magnetic flux density changes detected and ent during the relative movements of the two bodies speaks at least first signals, and
• - Evaluation units are provided by means of
  • - To form a coarse signal to determine the relative Ver shift of the two bodies, the number of zen detected by a sensor unit during a relative movement of the two bodies is determined (incremental evaluation), and
  • - To form a fine signal to determine the relative Ver shift of the two bodies, the course of the magnetic flux density changes caused by individual zen is detected (analog evaluation) and
• the relative displacement of the two bodies due to the Coarse and fine signal is determined.

The evaluation of a fine and coarse signal described above has the Advantage, an accurate and inexpensive measurement of the relative movement of the to allow both bodies.

In a further embodiment of the invention, the to detect the absolute position of the two bodies, being here

• - The zones are arranged in at least one further track, and
• - At least one sensor unit is provided, which is relative to the second body is immovably arranged and which by the Zones of the wider track caused magnetic flux density changes movements during the relative movements of the two bodies and emits corresponding second signals, and
• - The zones in at least part of the further, first track in different distances from each other and in the other, two th track are equally spaced, and
• - Evaluation units are provided, by means of which the absolute Position of the two bodies to each other due to an off evaluation of the signals is determined.

In an advantageous embodiment of the invention, that the evaluation units are designed such that from the first Signals caused by the zones of the second track magnetic flux density changes represent the number of a relative movement of the two bodies by a sensor unit zones is determined. So there are those with a relative movement of the two bodies past the first sensor means  the zones counted (incremental evaluation). By forming a Such a coarse signal gives a rough estimate of the relative Shift of the two bodies to each other. Roughly because the inevitable errors in the width of the individual zones lies.

If one now additionally evaluates the exact course of the invention magnetic flux density changes caused by the individual zones out of (analog acquisition, fine signal), so you refine the Rough measurement described above (errors up to a zone width), because with such a fine signal the exact position of the two bodies can be determined within a zone.

However, this only leads to an exact specification of the relative displacement of the two bodies, but not to the ge desired absolute position of the two bodies to each other. The determination of the absolute position of the two bodies the other happens because the evaluation units are designed in this way are that a the phase relationship between the first signals and the second signal representing phase signal is formed. in the In the simplest case, only two zones of the first track have one different from the other zones of the first track Distance from each other. In this case, a reference is realized point and the scanning of the zones of the first track provides one Reference mark, i.e. an area within the track in which the zones a phase shift compared to the zoning of the second track exhibit. If the reference mark is now reached and detected, so one arrives with the following precise Er according to the invention version of the relative shift to an exact absolute position position of the two bodies to each other.  

The simple design of the first track to detect a However, the reference mark has the disadvantage that after the start of the invent system according to the invention first detects the reference mark at least once must be to indicate the desired absolute position. Des because it is provided in a further embodiment that the Phasing changes over a wide range of tracks, making it very early on after starting the system from the recorded phase position of the signals representing the zones of the tracks to the absolute Position can be closed.

The system according to the invention finds application in the above-described level measurement, the system contains a cylinder the, with a piston moving with a piston rod in the cylinder Lich is arranged. The piston rod has in its longitudinal ver run at least two zones, the different magnetic Have properties. Furthermore, there is at least one sensor unit provided which is arranged immovable relative to the cylinder, and which detects the different magnetic properties. The two bodies which are displaceable relative to one another are preferably included the structure and a wheel unit of a motor vehicle directly or indirectly related to the company. As a cylinder, piston and piston rod a damper is formed between the vehicle body and the wheel unit is attached.

When using the invention for spring movement measurement results the advantage that differed by the incorporation of the zones Licher magnetic properties the surface of the piston rod remains unchanged. For example, for a damper, that there are no problems with tightness (piston rods from seal) occur. Furthermore, in the case of a damper  entire measuring system including signal conditioning in the damper be integrated. By counting the zones, i.e. H. by Incre mentation of the sensor detecting the different zones impulses, one arrives at a high accuracy and resolution of the measuring path or the speed that can be determined from this. The Speed is directly proportional to the frequency of the Sensor signals.

In an advantageous embodiment of the system according to the invention at least two sensor units are arranged such that these when the bodies move, the different magnetic Record properties at different times. The signals from the sensors units are supplied by means of which the data generated by the two sensor units also recorded first and second sensor signals each other to determine the relative direction of movement of the body be compared. In this embodiment, the fiction provides system not only the displacement of the two bodies to each other or the displacement speeds, but also covers the loading directions of movement of the body to each other.

In a further advantageous embodiment it is provided that the piston rod extends at least two in its longitudinal direction Has traces (zone areas), the traces of at least there are two zones with different magnetic properties. In each case at least one sensor unit detects the zones of the Traces. This allows position markings on the piston rod can be detected, whereby a detection of the absolute damper path is made possible.

In addition to the latter configuration, it can be provided that that the sensor means detecting the tracks first and third sensor emit signals, and these signals supplied to third evaluation units leads. Using the third evaluation units, the  first and third sensor signals for detecting the absolute position of the two bodies to each other and / or determination of the determination compared function of the sensor units.

A particularly advantageous embodiment of the invention Systems, especially the mechanical design of the piston rod, it follows that the piston rod from two into each other which is formed by screwed or nested pipes, the two pipes being made of materials that differed Liche magnetic properties. To form the zones, which, as mentioned, has different magnetic properties can have, the outer tube with an internal thread and / or inner tube, which can also be designed as a solid rod, with be provided with an external thread. Another possibility is that the outer tube on its inside and / or the inner tube is provided on the outside with annular notches. This Design has the advantage that a simple mechanical Her position of the piston rod as a displacement encoder is possible. About that In addition, the mechanical stability of the piston rod remains a conventional one almost unchanged.

Another embodiment of the invention is that for Obtaining the traces (areas of zones of different magne table properties), depending on the design of the interior and Outer tube, the internal and / or the external thread and / or one or both of the annular notches in the longitudinal direction of the pistons rod has or have asymmetry. For example wise in the case where the outer tube has an internal thread and / or the inner tube is provided with an external thread Thread turn removed over a length of about 90 to 180 degrees become. When walking through this path segment, a recognizes accordingly positioned sensor, the above-mentioned sensor for position mar detection, in connection with the sensors or the sensor, which detects the complete thread, the failure of a zone as Position marker.  

Through the system according to the invention or through its configurations the following advantages can still be achieved:

• - The fact that the output signals of the sensor units as analog, sinusoidal or digital signals with constant amplitude lie, one arrives at an interference-free transmission of the Path or speed information between the two Bodies, for example a shock absorber, and the control unit, that further processes this information.
• - In the design of the piston rod with inside and / or outside thread or rings, the increment can be a multiple of that Number of threads. With analog signal transmission the resolution is even higher.
• - The direction of travel and thus the force zero crossing in the event of an impact can be directly connected to the phase position of the output signals of the both capture the movements of the body at different times Sensor units can be read.

Furthermore, in the embodiment of the invention as a spring Motion sensor provided that the zones of different magne properties in one track at equal intervals different and in the other track at different distances are arranged differently. The tracks are in the longitudinal direction Piston rod arranged. Now, as described above, become the zones of the traces sensed, the phase position of the Scan signals the absolute position of the two bodies to each other become.

The integrated deflection travel sensor according to the invention, which the Travel distance or the travel speed between the rides tool structure and a wheel unit can be detected, in particular half of the damper near the piston rod seal become.  

Another embodiment of the motion measuring system according to the invention is that the device as a steering angle detector at one Motor vehicle is formed, the one body that tracks has, is operationally connected to one steering shaft and the other Body formed as a steering housing connected to the vehicle is.

It is particularly advantageous in this embodiment of the invention as a steering angle measuring system that the tracks on a concentric order the steering shaft arranged metal disc as circular orbits different radii around the steering shaft or the tracks on a cylinder surface arranged concentrically around the steering shaft run.

Further advantageous embodiments of the invention are the Unteran to take sayings.

drawing

Fig. 1a is a schematic of a shock absorber with a piston rod and Figs. 1, 2 and 2a are different design options of the piston rod. FIGS. 3a and 3b illustrates waveforms are to be found for evaluating the signals detected according to the invention while in Figs. 4, 5, 6, 7 and 8 TIC arrangements. In Fig. 9 and 12 waveforms can be seen and in Fig. 10 different configurations of the piston rod. FIG. 11 shows the schematic structure of the invention as a steering angle detector and FIG. 12 shows signal curves.

Embodiments

In the exemplary embodiments to be described below, this is System according to the invention first based on the detection of the spring way or the spring deflection speed on a shock absorber Motor vehicle shown. In a further part the Invention described based on the detection of a steering angle.

Such a shock absorber is first shown as a model in FIG. 1a. The shock absorber is located between the vehicle construction A and the wheel unit R. The damper has an outer jacket tube 142 , to which an inner jacket tube 143 is concentrically fastened. The outer jacket tube 142 is closed at the end by the first bottom 144 and the inner jacket tube 143 by the second bottom 148 . In the vicinity of the first floor 144 there are throttling points III and IV in the second floor 148 , through which an exchange of fluid means from the annular space C formed by the casing pipes 142 and 143 into the interior space formed by the casing pipe 143 is possible. The outer casing tube 142 is closed by a cover 145 and the inner casing pipe 143 is closed by a cover 146 . The covers 145 and 146 have central piston rod bushings, through which a piston rod 141 is guided, which continues inside the damper in a damping piston 147 . Due to the damping piston 147 of the interior of the inner jacket tube 143 into an upper working chamber A and a lower working chamber B is under approaches, wherein an exchange of fluid means between the working chambers A and B via the throttle points I and II in the piston 147 is possible. So it is a known (J. Reimpel, chassis technology: shock absorber, Vogel-Buchverlag, Würzburg) twin-tube damper. When the wheels deflect (compression stage) the damper is shortened, the piston 147 goes down and part of the fluid flows from the lower working chamber B through the throttle valve I designed into the upper working chamber A. The amount of fluid medium corresponding to the immersing piston volume is pressed into the annular space C, namely by the Liche located in the second bottom 148 and designed as a valve throttle point III.

When the wheels are extended (rebound stage), the rising piston 147 creates an overpressure in the lower working chamber A. The fluid medium is pressed into the lower working chamber B through the throttle point II designed as a valve. The extension of the piston rod 141 results in a lack of fluid in the work space A. This missing amount is sucked out of the working chamber C through the throttle point IV designed as a valve.

If you now place throttle point II and throttle point III in this way that the throttle cross section is adjustable, so you get to changed damping properties in the tension (throttle point II) and in the pressure stage (throttle point III).

A sectional view of the piston rod 141 can be seen in the left part of FIGS. 1 and 2. The piston rod consists of two tubes that are screwed together. The outer tube 110 is thin-walled and possibly provided with an internal thread. The inner tube 112 consists of a thick-walled steel tube or solid rod to absorb the transverse and longitudinal forces of the damper. This tube 112 has an external thread or annular notches.

The threads of the tubes which are screwed or plugged into one another serve as a replacement for gearwheels, the two tubes 110 and 112 being made of materials with as different a magnetization as possible. The outer tube 110 can have paramagnetic properties, for example, and the inner tube 112 can have soft magnetic properties.

The piston rod 141 is thus divided in its longitudinal course into zones 111 , 111 'of different magnetic properties. A thin liquid varnish or resin can be applied to the threads of the pipes 110 and 112 before assembly, which then hardens. This prevents the damper oil from leaking through the thread and improves mechanical stability.

In some circumstances, however, it is sufficient to provide only one of the two pipes 110 or 112 with a thread. This has the following advantages:

• - In the manufacture of the outer tube, for example made of V2A no cutting of the internal thread necessary (simpler Manufacture).
• - Easier assembly.
• - There is a better fit between the two pipes because no typical thread is necessary.

The sensors S1, S2 and S3 as well as the signal processing electronics 101 and 102 can, for example, be attached as an annular circuit board around the piston rod guide and possibly cast in. The resulting height is compensated for by reducing the height of the piston, since a sensor attached to the piston is not necessary.

Differential Hall sensors can be used as sensors S1, S2 and S3 (Gear sensors) are used, which are from the prior art are known.

From the on the left side of FIGS. 1 and 2 to see orders of the piston rod on the upper surface of the piston rod there are different zones 111 , 111 'with different magnetic properties. In addition to the Hall sensors, a magnetic field is required to record these different magnetic properties. To generate the magnetic field, a permanent magnet is attached to the back of the sensor IC.

Now a piston rod as described above along the Hall sensors passed, the measured magne changes table density depending on the density just below the surface of the Piston rod attached thread. A thread is created Profile approximately proportional sensor AC voltage.

Here, two Hall sensors 11 and 12 are attached such that the output signal of the second sensor 12 is offset in time by, for example, 90 degrees from the signal of the first sensor 11 . The direction of movement of the piston rod can thus be recognized. The 90-degree offset of the output signals S1 and S2 of the sensors 11 and 12 can take place both vertically and horizontally by 90 degrees offset attachment (taking advantage of the thread pitch) of the two sensors 11 and 12 .

The sensor signals S1 and S2 and the sensor signal S3 still to be described are processed in the units 101 and 102 to form the signals S1 ', S2' and S3 'and fed to the further evaluation units 120 and 121, respectively. Furthermore, their power supply (I) and grounding (GND) are fed to the sensors via the sensor signal processing 101 and 102 .

In Fig. 2a an embodiment of the piston rod can be seen in the left part, in which the zones of track b are arranged equidistantly (with equal distances from one another) and the zones of track a are equidistant in the lower part and in the upper part upward decreasing distance are arranged. The advantages that result from this configuration are explained on the basis of the signal profiles shown in FIG. 9.

Referring to Figs. 3a and 3b will now be shown that the piston rod can be detected by the evaluation of the output signals S1 and S2 from the sensors 11 and 12, or by evaluating the processed signals S1 'and S2', the direction of movement.

For this purpose, the signal curves S1 and S2 for an extending damper piston are shown in FIG. 3a. The sensor signals S1 and S2 represent the zones of different magnetic properties of the piston rod. If you now assign the binary levels 0 ("Low") and 1 ("High") to the two levels of the signals S1 and S2, you get to the binary signals BIN1 and BIN2, where BIN1 and BIN2 can represent a two-digit binary value.

Comparing these binary signals BIN1 and BIN2 in a next step leads to signal V. Signal V is the decimal value corresponding to signals BIN1 and BIN2. The signal V assumes the value 0 whenever the signals BIN1 and BIN2 have the value 0 at the same time. Furthermore, the signal V has the value 1 whenever the signal BIN1 has the value 0 and the signal BIN2 has the value 1. The value V = 2 is set when the signal BIN1 has the value 1 and the signal BIN2 has the value 0, while the signal V = 3 is set when both signals BIN1 and BIN2 have the value 1. If one compares the pattern of the signal V in FIG. 3a (signal curve for the extending damper) and the curve of the signal V in FIG. 3b (signal curve for the incoming damper), it can be seen from the sequence of the values for V that by the 90th -Degradation of the signals from the two sensors 11 and 12 enables unambiguous detection of the direction of movement. A corresponding evaluation of the signal V thus leads to a two-stage signal R which indicates whether the piston rod is moving in or out of the damper cylinder. In one embodiment of the invention, this can be done in units 102 ( FIGS. 1 and 2, bottom right).

A third sensor 13 with the output signal S3 can finally be used to detect one or more absolute position markings of the damper path.

This can be achieved, for example, by removing a thread in the middle of the thread (target level position) over a length of approx. 90 to 100 degrees. When passing this Wegseg mentes this sensor 13 recognizes in connection with the signal from the sensors 11 or 12 the failure of a zone (worn thread). The sensor 13 is placed in such a way that only it detects this loss of gear speed (for example, the sensor 13 can be attached to the piston rod side opposite the sensors 11 and 12 ).

The left part of FIG. 1 shows, for example, the lack of a thread in the area of the sensor 13 . Such an arrangement leads to a piston rod configuration which has asymmetry in the longitudinal direction with regard to its zones of different magnetic properties. So you get to two different in the longitudinal direction of the piston rod zones or tracks a and b, which consist of zones 111 and 111 '. Zones 111 and 111 'of tracks a and b detect sensors 11 and 12 (track b) and sensor 13 (track a).

The signal processing can take place, for example, by mounting the sensors 11 and 13 in such a way that they deliver an in-phase output signal. If you subtract these two sensor signals S1 and S3 from each other, you will only get an output signal if the missing thread is passed. Such a subtraction can take place, for example, in the units 101 and 102 , so that a value is only output as the output signal S3 'when the position marker is recognized.

While the absence of a thread is shown in the left part of FIG. 1, a further design can be seen in FIG. 2 in the left part. The omission of only one thread part ( FIG. 1) can lead to initialization problems in a vehicle with level control. In such a system, after starting the vehicle, it is initially not possible to tell whether the damper is above or below the position mark. This can be solved in that a corresponding transition from "high" to "low" takes place for the sensor 13 at the point of the desired level position. Thus, immediately after starting the vehicle, it can be recognized whether the vehicle is above or below the target level position. Now, for example with an active level control system, it is possible to start at a predetermined speed to change the deflection of the vehicle in the direction of the desired level position. The speed of the level shift can already be measured by means of the sensors 11 and 12 . When running through the target level position, the sensor 13 recognizes the transition and adjusts the evaluation circuit, for example by setting an incremental counter according to the target level position.

If the two sensor signals S1 and / or S2 are subtracted from the sensor signal S3, an output signal change is obtained in this embodiment when passing through the missing thread region (upper part of the piston rod in FIG. 2). As a subtraction result, a rectangular signal is only obtained in the area of the missing threads.

The mechanical design of this embodiment can be done for example in such a way that the thread on the running line of the third sensor 13 is milled up to half (coming from above or below to the desired level position). The lower half can also be designed without a thread (solid material). For mechanical stabilization, the milled thread part can be filled with V2A steel or with resin.

In this embodiment, a failure of the sensor 13 can also be detected if the level control in the start phase of the vehicle does not find the transition at the desired level position, controls up to the stop, detects the stop and then informs the evaluation circuit accordingly (position counter reset). The sensors 11 and 12 can monitor each other. This means that if only one sensor fails, the target level position can still be recognized.

In the following, the digital increments mentioned above will now be discussed tal evaluation of the sensor signals S1, S2 and S3 in detail be gone.

Such digital, incremental measuring methods are known for their precise and drift-free path measurement. However, one of their disadvantages is their poor absolute path detection at the start of the measurements. Only after the so-called reference mark (detected by sensor 13 ) has passed through does the system begin to output an absolute path position.

The following is now based on the example of the displacement measurement of a shock absorber described how to get a can recognize absolute path position.

In the embodiment described above and shown in FIG. 2, the piston rod is, as described, the path area below the marking in the area of the sensor 13 identified as a "low" signal, the area above the marking as a "high" signal . In vehicles with active level control, the vehicle level can thus be brought into the desired position immediately after starting. An arrangement according to FIG. 2 is sufficient for such vehicles. For vehicles without active level control, however, it remains to be seen until this zero mark is passed randomly after the start in driving mode in order to obtain an absolute position information.

With the circuits described below you get to a incremental measuring system of a shock absorber, with which to a very early after starting the vehicle (depending on the zone division maximum after 2.8 mm) to achieve an absolute path position is.

FIG. 4 shows the electronics needed basis of a block diagram. This electronics is preferably integrated in the shock absorber. FIGS. 5 and 6 further evaluation positions represent, and Figs. 7 and 8 show evaluation circuits by means of a microprocessor. In the Fig. 9 typical waveforms of the output voltages of the sensors 11, 12 and 13 as well as the evaluation circuits in measuring the spring deflection finally are shown.

In FIG. 4, the sensors and the sensor signal conditioning can be seen. In block 41 , the two sensors 11 and 12 are in the form of bridge circuits (R1, R2, R3, R4) which are supplied by the operating voltage Ub. The sensor 13 can also be seen in the units 42 of FIG. 4 as a bridge circuit (R7, R8, R9, R10) with the supplied operating voltage UB.

The tapped voltage signals of the third circuits are fed to the differential amplifiers 410 , 411 and 412 . On the output side of the differential amplifiers 410 and 411 are then the signals S1 'and S2' required for incremental displacement, which at a fixed zone spacing of 2.8 mm, for example, already represent two analog output signals set at 90 degrees. It is possible to design the two sensors 11 and 12 (bridge circuits in unit 41 ) as a single sensor if one proceeds from the full-bridge circuit and uses the two half-bridges spaced apart on the chip by approximately 0.7 mm (4 × 0.7 mm = 2.8 mm zone distance). The sensor 13 (bridge circuit in units 42 ) is used as a full-bridge Hall sensor and is used to evaluate the reference mark signals. The sensor signals are amplified, possibly temperature compensated and output as analog sinusoidal signals.

In the further evaluation circuit ( FIGS. 5 and 6) a phase-dependent fast level detection is carried out, among other things. The intersection points of the two input signals (U _E1 = S1 ', U _E2 = S2') are determined with the aid of a comparator 519 and 619 , and a sample pulse during a with the aid of a monoflop ( 520 , 620 ) and a gate ( 621 ) of the two intersections. This sample pulse controls the switch ( 616 ), so that the current value of U _E3 is held on the capacitor ( 617 ) and impedance converter ( 618 ).

Since the intersection of the input signals S1 'and S2' offset by 90 degrees of the sensors 11 and 12 is very phase-stable, and the sensor 13 is a very temperature-stable signal conditioning, this circuit arrangement can be used to make a phase analysis that can be easily evaluated between the two racks. In Fig. 9, the curves of the sensor signals U _E1 (S1 '), U _E2 (S2') and U _E3 (S3 ') are shown in a time representation, the zone area 1 (track b, by the sensors 11 and 12 is scanned) and the zone area 2 (track a, which is scanned by the sensor 13 ). In the upper area of FIG. 9, the signals S1 'and S2' of sensors 11 and 12 are shown offset by 90 degrees. The zone spacing, ie the tooth spacing, is 2.8 mm in this exemplary embodiment. The zones scanned by sensors 11 and 12 are arranged at the same distance (2.8 mm) over the entire longitudinal region of the piston rod. In contrast to this, as can be seen in FIG. 2a, the zones which the sensor 13 scans in the area (in the lower area of the piston rod) up to a marking which represents the desired level are also at equal intervals arranged. The phase position of the signals S1 ', S2' and S3 'are the same in this area, ie the phase signal U _A3 has a constant level in this area. The phase and amplitude jump U _A3 is clearly visible when passing through the target level. In the track scanned by the sensor 13 , the zones which lie beyond the desired level (in the upper region of the piston rod) are arranged at different distances from one another. In the embodiment shown in FIGS. 9 and 2a, a total of 5 zones with different distances are arranged in this area of the zones. This results in a phase shift between the signals S1 'and S2' on the one hand and the signal S3 'on the other. This can be seen from the phase signal U _A3 , which has 5 stages in this exemplary embodiment. A third zone region, which is no longer shown in FIG. 2a, is at the same distance from it, as a result of which a fixed phase position of the signals S1 ', S2' and S3 'is again achieved (right part of FIG. 9).

The jump in amplitude when the desired level is reached is evaluated with the aid of the comparator ( 622 ) and the reset logic ( 614 ) and resets the counter ( 69 ). The "Power on reset" resets the V / R counter ( 69 ) and the status bit of the "first zero crossing detection" after the vehicle has started. The first zero-level run after the vehicle has started generates a counter reset and sets a status bit. This status bit can be read from the microprocessor at any time using the analog switch ( 612 ).

After switching on the supply voltage Ub, the analog phase signal U _A3 is available at the latest after a path change of 2.8 mm (distance of the zones in the area of the sensors 11 and 12 ). This phase signal can be evaluated as preliminary information until the status bit, which can also be monitored, reports the first zero-level pass. In order to achieve a better resolution of the analog phase signal, it makes sense to limit the path range in which a continuous phase shift takes place, for example to the typical load-dependent deflection path.

The following is a summary of the absolute path detection Operation of the invention in this regard described again become.

If one assumes that the position measuring system according to the invention is used to record the spring deflection for chassis control, then the detection of the sensor signals S1 and S2 leads to the information as to whether the damper is in the rebound or compression stage and which spring speed is present. After switching on the system (starting the vehicle) there is no absolute reference, ie the information which level is set on the respective damper. In the embodiment of the invention described above, it is now a matter of getting an absolute reference as quickly as possible after switching on the system. This absolute reference point is obtained in that a phase jump takes place between the output signals of the sensors 11 and 12 and the sensor for the reference mark recognition 13 . To detect this phase shift, however, the target level position must be reached.

If we now consider, for example, the case that the vehicle was loaded before it started, it may take a very long time for vehicles that do not have active level regulation until the target level, ie the phase shift, is reached. Only when the loaded vehicle travels through a larger bump in the road, for example, are the deflection movements such that the desired level is reached. In order to maintain an absolute path signal as quickly as possible in such vehicles without active level regulation, the rack detected by the sensor 13 (zone division) is designed below the target level in such a way that the teeth or zones of different magnetic properties differ from each other Have clearances. However, these different distances of the zone area, which is detected by the sensor 13 , now causes a different phase position of the signals from the sensors 11 and 12 to the signals from the sensor 13 . By detecting the phase position (phase signal U _A3 ), an approximate estimate of the absolute path position can be reached in the area below the target level after a very short time. If the vehicle is, for example, in the unloaded state above the target level, one can only see from the phase signal U _A3 in this exemplary embodiment that the vehicle is above the target level. In this case, absolute path detection can only be achieved when the target level is exceeded. Likewise, in the exemplary embodiment shown in FIG. 9, an area is provided far below the target level, in which the zone division is again characterized by the same distances between them. In this area, the phase position of the signals S1 ′, S2 ′ and S3 ′ is again constant (3/4 Ub), but has a different value than the phase position in the area above the target level.

Referring to Figs. 5, 6 and 9, the evaluation according to Invention shall now the signals are shown for determining the spring deflection in the following.

The core of the incremental rough measurement is formed by a forward / backward counter ( 69 ) with a downstream digital-to-analog converter ( 610 ), at the output of which there is a rough analog voltage (U _A1 ) incrementing every 2.8 mm. Due to the coarse resolution (for example 7 bits) the analog value can be read by a microprocessor without errors. The course of the signal U _A1 in particular its dependence on the signals S1 ', S2' can be seen in the lower part of FIG. 9. This leads to the step-shaped signal U _A1 , which can serve as a coarse signal for measuring distance and / or speed. As a rough measurement of the spring deflection, you can see how many of the zones have been recorded.

One of the analog signals S1 'or S2' serves as a fine signal for recognizing in which area of the respective counted zone the system is located. In order to achieve a better evaluation of the analog signals by the evaluation circuit or by the microprocessor, this sinusoidal signal S1 'or S2' can be converted into a type of ramp signal, for example by inverting ( 66 ) the falling sine half. In this way, the fine signal U _A2 shown in FIG. 9 is obtained. In the example shown in FIG. 9, the signal S1 'is evaluated in the manner described above. The switchover criterion for the fine signal U _A2 is the input signal S2 'digitized with the aid of the comparator ( 63 ). In order to get by with just one analog output signal, the analog switches ( 64 , 65 , 611 ) can be used to switch between the four dampers of the vehicle and the analog switch ( 612 ) to switch between coarse, fine, phase and status signals.

If one of the sensors 11 or 12 is not designed as a full bridge circuit, larger temperature-dependent offset and amplification drift phenomena can occur due to the system. These drift phenomena can be compensated for using temperature sensors on the differential amplifiers ( 410 , 411 , 412 in FIG. 4) or by an additional full-bridge evaluation of the sensors 11 and 12 , as can be seen in dashed lines in FIG. 4 / unit 409 is for microprocessor evaluation. This full-bridge evaluation, in particular in the case of an evaluation by a microprocessor, enables a better phase evaluation with respect to S3 '.

But if you want to increase the resolution of the analog signal for a finer path signal, it can come to temperature-dependent measurement errors despite the above-mentioned temperature corrections. For this purpose, a self-regulating correction of offset and reinforcements is shown in FIG. 5.

Since the temperature-dependent signals S1 'and S2' change in the same way, the phase-related intersection of these remains stable for the signals and also the corresponding signal forms. With the aid of the comparator ( 519 ) and the downstream monoflop ( 520 ), a sample pulse is obtained at its intersection points. With the help of switches ( 523 , 524 ) and holding capacitors, the two intersection values can be stored in the impedance converters ( 525 and 526 ). The exact zero crossing of the two signals is statically present at the center of the two resistors (R). With the help of a differential amplifier ( 527 ), the offset drift can thus be subtracted from the useful signal. The difference between the two intersection points also represents a kind of target signal amplitude. With the help of a differential amplifier ( 528 ) and a controllable amplifier ( 529 ), the gain drift can be corrected.

Although the above-mentioned method means additional expenditure on components, it makes any adjustment in the processing of the sensor signal ( FIG. 4) and the signal evaluation ( FIGS. 5 and 6) superfluous.

This can be particularly advantageous when integrating the complete evaluation circuit in a special IC, because no high-quality and critical components are used here. Such an IC could with a pin count of 20 every 4 shock absorbers Process signals at the same time.

FIG. 7 represents a solution that is also interesting for reasons of cost and convenience, with the use of a simple microprocessor. Such microprocessors are relatively inexpensive and can perform all the functions described in FIGS. 5 and 6 and also take over the correction of the initially relative path signals on the absolute path with the help of the rough phase signal as well as the sensor failure detection and linearization of the fine signal from the sine signal.

For this purpose, the microprocessor 71, the output signals or the processed output signals S1 ', S2' and S3 'of the sensors 11 , 12 and 13 are supplied. As indicated in FIG. 7, this happens for all four shock absorbers of the vehicle (VL front left, VR front right, HL rear left, HR rear right). The desired data can then be read out on the output side of the microprocessor 71 by means of a serial interface or a parallel output.

When using a microprocessor, it is particularly advantageous to read in all inputs internally in short time intervals (for example 2.8 ms). In addition to this time-dependent reading, all inputs are read in at each intersection of the input signals U _E1 (S1 ′) with U _E2 (S2 ′). All inputs are read internally every 2.8 ms at the latest. In addition, the inputs are read in at each detected intersection of the input signals S1 'and S2'. The use of external interrupt inputs results in a "recovery" of computing time, which can be used for further processing of the travel and the travel speed. This reduces the load on the computer of a possible downstream control unit. The following advantages should be mentioned for the evaluation devices of the measuring system according to the invention described above:

• - At the latest after a path change of 2.8 mm after "Power on" a rough analog path signal is available.
• - Free choice of the measuring range of the phase-related position (e.g. on the typical load-dependent travel). Thereby He increase in sensitivity.
• - Better mutual sensor failure detection since the Reference mark recognition and the path measurement continuously provides impulses.
• - Low-drift phase reference mark by evaluating the intersection two reference signals offset by 90 degrees.  
• - With an arrangement according to FIGS. 5 and 6, no electrical adjustment is required. This means simple manufacture of a special evaluation IC.
• - Elimination of dead time compared to previous evaluation circuits (approx. 3 ms) to report the zero speed crossing. It is one accurate and fast speed zero point detection possible. Switching of damping characteristics of the damper should ideally be at the single-stroke zero speed crossing occur, which results in a reduction in switching noise Has.
• - Low energy consumption.
• - Good damper stop detection possible.
• - The evaluation circuit of all four displacement sensors can be done by one simple microprocessor to be replaced. This is one affordable overall solution possible.
• - There can be a safe trigger threshold through offset drift compensation tion can be achieved. This results in a safe sensor signal evaluation.

Arrangements of the two rows of teeth of the piston rod can be seen by way of example in FIGS. 10a and 10b. The Fig. 10a shows a sectional view in this case a piston rod for a single-tube damper, while in Fig. Is a sectional view of a piston rod is of a two-pipe damper shown on a front axle 10b. The tooth row or the zone area for phase measurement is marked with the reference number 1004 , and the tooth row or the zone area for distance measurement is marked with the reference number 1003 . 1001 shows a notch as protection against rotation for mounting the damper in the vehicle. Threads for fastening are identified by reference number 1002 . The main direction for the bending load of the piston rod are indicated by arrows with the reference 1010 and the maximum steering angle a is marked with 1013 .

In the following, the Use of the motion measuring system according to the invention in a steering angle detector are explained.

For this purpose, the top view of a steering shaft 1100 of a motor vehicle can be seen schematically in FIG. 11. Such a steering shaft can connect, for example, the steering wheel actuated by the driver of the vehicle to the steering gear. A metal perforated disk 1101 is attached concentrically to the steering shaft 1100 , on which 2 tracks made of punched holes, which form the zones 111 and 111 'of different magnetic properties already described. The tracks a and b are also arranged concentrically around the steering shaft 1100 as circular paths with different radii around the steering shaft.

As another version, a concentric around the steering shaft arranged cylinder may be provided, on the surface of which Tracks also as circular orbits (now with the same radii) around the Steering shaft are formed.

As indicated in FIG. 11, the sensors 11 , 12 and 13 which detect the magnetic flux density changes are firmly connected to the steering housing 1104 . In order to ensure a constant distance between the sensors 11 , 12 and 13 to the zones 111 and 111 'or to the perforated disk 1101 , the sensors 11 , 12 and 13 are attached to a carriage, not shown, which slides on the metal disk 1101 . This results in uniform amplitudes of the sensor signals.

When the steering shaft is actuated, the zones of tracks a and b move past sensors 11 , 12 and 13 which are fixed to the housing and cause the magnetic flux density changes.

Equivalent to the spring deflection sensor already described, the zones of track b are arranged equidistantly, while the zones of track a are at different distances in at least part of track a. As already explained in detail, counting (incrementing, coarse signal U _A1 ) the zones of track b and analog evaluation of the individual zones of track b (fine signal U _A2 ) lead to an exact measurement of the steered steering angle phi.

Likewise, in the manner already described, an evaluation of the phase position of the signals S1 'and / or S2' on the one hand and the signal S3 'on the other hand leads to an absolute angle detection. For this purpose, the course of the phase signal U _A3 already shown in FIG. 9 is shown once again in the upper part of FIG. 12, the phase relationship of the tracks a and b in the region above the desired level being chosen to be constant in the exemplary embodiment described ( Compression).

In contrast, in the case of the steering angle detector, the phase position tracks a and b are not designed to be constant over a wide range. The phase shift, which is advantageous in the straight-ahead position of the steering wheel is selected, as in the case of the deflection sensors by skipping a zone or a 180 ° jump of the track a.

In particular, it is advantageous to design the phase position of tracks a and b non-linear, since the accuracy of the absolute steering angle measurement depends on the change in the phase position. As can be seen in the middle signal train of FIG. 12, the phase changes in the range of the steering angle phi = "0" (straight ahead) can be selected to be large. This has the advantage that at high vehicle speeds only small steering angles are made, but these have a significant impact on driving behavior. Precise absolute steering angle detection is therefore necessary in this area. For small steering angles with regard to driving straight ahead, a precise coarse signal is thus obtained in advance after the system is switched on.

Within a single revolution of the steering shaft (+ 180 ° to -180 °) you get the absolute position of the steering shaft by evaluating the phase signal with high accuracy. However, since the steering shaft in a motor vehicle can generally be rotated more than 360 °, a further arrangement is necessary. It is assumed that the steering shaft 1100 z. B. is designed for a maximum of four revolutions (+/- 720 °).

For this purpose, a gearwheel concentrically attached to the steering shaft 1100 is sketched in FIG. 11, in which a gearwheel 1102 engages. The essence of this idea is that the size of the gear connected to the steering shaft and the gear 1102 are chosen such that the gear 1102 is, for example, four complete revolutions (+/- 720 °) of the steering shaft 1100 by a maximum of half Revolution (+/- 90 °) turns. This can optionally be achieved with an intermediate gear, that is to say by means of a gear between the steering shaft 1100 and gear 1102 . On the gear 1102 , a magnet 1103 is now concentrically attached, the magnetic field of which is measured by means of a sensor 1105 attached to the steering housing 1104 and centrally to the gear 1103 (output signal S4 ', FIG. 7). One thus reaches the signal U _A4 shown in FIG. 12. The sensor 1105 can, just like the sensor 13 in the embodiment described in FIG. 2 be very simple (low resolution) and inexpensive, since it is only used to determine the coarse signal U _A4 , which indicates which Rotation range is the steering shaft 1100 . The coarse signal U _A4 can be seen in the lower area of FIG. 12.

In summary, the following advantages of a gearbox are Permanent magnets and Hall angle sensors to name:

• - There is no mechanical end stop, which is used for possible destruction of the steering angle sender could result.  
• - An incorrect assembly adjustment can be easily recognized or a test output can be provided for setting the straight-ahead travel during assembly. This is shown in FIG. 7 as a test output. In a steering angle measuring system, signal 1 for a steering angle to the right of the straight ahead position and signal 0 for a steering angle to the left of the straight ahead position can be present at this output, for example.
• - It can also be an automatic correction quantity formation, for example in learning systems.

Claims (11)

1. motion measuring system for a device with two mutually ver sliding bodies ( 141 , 147 , 1100 , 1101 and 145 , 146 , 1104 ) for detecting movements of the first body relative to the second body, wherein

• - The first body ( 141 , 1101 ) zones ( 111 , 111 ') which have different magnetic properties, and
• - The zones ( 111 , 111 ') are arranged in at least one track (b), and
• - At least one sensor unit ( 11 , 12 ) is provided, the rela tive to the second body ( 145 , 146 , 1104 ) is immovably arranged and which caused by the zones ( 111 , 111 ') of the track (b) gently caused magnetic flux density changes during the Relativbe movements of the two bodies detected and corresponding at least first signals (S1 ', S2') emits, and
• - Evaluation units ( 120 ) are provided by means of
  • - To form a coarse signal (U _A1 ) to determine the rela tive displacement of the two bodies, the number of zones ( 111 , 111 ') detected during a relative movement of the two bodies by a sensor unit (S1', S2 ') (incremental tale Evaluation), and
  • - To form a fine signal (U _A2 ) to determine the rela tive displacement of the two bodies of the course of the magnetic flux density changes caused by individual zones ( 111 , 111 ') is detected (analog evaluation) and
• the relative displacement of the two bodies is determined on the basis of the coarse and fine signals.

2. System according to claim 1, characterized in that

• - The zones ( 111 , 111 ') are arranged in at least one further track (a), and
• - At least one sensor unit ( 13 ) is provided, which is arranged immovably relative to the second body ( 145 , 146 , 1104 ) and which causes the magnetic flux density changes during the relative movements caused by the zones ( 111 , 111 ') of the further track (a) detect the two bodies and emits corresponding second signals (S3 '), and
• - The zones ( 111 , 111 ') are arranged in at least part of the further, first track (a) at different distances from one another and in the other, second track (b) at equal distances from one another, and
• - Evaluation units ( 120 ) are provided, by means of which the absolute position of the two bodies relative to one another is determined on the basis of an evaluation of the signals (S1 ', S2', S3 ').

3. System according to claim 2, characterized in that the evaluation units ( 120 ) are designed such that a phase position between the first signals (S1 ', S2') and the second signals len (S3 ') representing phase signal (U _A3 ) to determine the absolute position of the two bodies relative to one another, the first signals (S1 ′, S2 ′) representing the magnetic flux density changes caused by the second track (b), and the second signals (S3 ′) representing those through the first track (a) represent magnetic flux density changes caused. 4. System according to one of claims 1 to 3, characterized in that the device is formed as a suspension system of a motor vehicle, the second body as a cylinder ( 145 , 146 ) and as the first body in the cylinder with a piston rod ( 141 , 110 , 111 , 112 , 113 ) has movably arranged pistons ( 147 ), the longitudinal length of the piston rod having the at least two zones ( 111 , 111 ') with different magnetic properties. 5. System according to claim 4, characterized in that the piston rod is formed from two screwed or nested pipes ( 110 , 112 ) or from a plugged or screwed into a solid rod, the two tubes or the tube and the solid rod Materials exist that have different magnetic properties and to form the zones ( 111 , 111 ′)

• - The outer tube ( 110 ) with an internal thread and / or the inner tube ( 112 ) or the solid rod with an external thread ( 111 ) or
• - The outer tube ( 110 ) on its inside and / or the inner tube ( 112 ) or the solid rod on its outside with ringför shaped notches

is provided. 6. System according to claim 5, characterized in that for obtaining the tracks (a, b) depending on the design of the inner and outer tube ( 110 , 112 ), the inner and / or the external thread and / or one or both of the annular notches rod has or have asymmetry in the longitudinal direction of the piston. 7. System according to one of claims 1 to 3, characterized in that the device is designed as a steering angle detector in a motor vehicle, wherein the first body ( 1101 ) with a steering shaft ( 1100 ) is operationally connected and the second body as a connected to the vehicle Steering housing ( 1104 ) is formed. 8. System according to claim 7, characterized in that the tracks (a, b) on a concentric around the steering shaft ( 1100 ) arranged metal disc ( 1101 ) as circular paths with different radii around the steering shaft or or the tracks (a, b) run on a cylinder surface arranged concentrically around the steering shaft ( 1100 ). 9. System according to claim 1, 4 or 7, characterized in that first evaluation units ( 101 , 120 , 102 , 121 ) are provided, by means of the first signals (S1 ', S2'), which through the zones ( 111 , 111 ′) of the second track (b) caused magnetic flux density changes represent, the displacement of the body and / or the displacement speed of the body is determined. 10. System according to claim 1, 4 or 7, characterized in that sensor units ( 11 , 12 ), which he the magnetic flux density changes caused by the zones ( 111 , 111 ') of the second track (b), are arranged such that when the bodies are shifted, they record the changes in flux density at different times and second evaluation units ( 101 , 120 , 102 , 121 ) are provided, by means of which the changes in flux density recorded at different times are compared with one another to determine the relative direction of movement of the bodies.