FR2786563A1 - DEVICE AND METHOD FOR MEASURING A ROUTE, PARTICULARLY A TRAVEL OF A BRAKE PEDAL - Google Patents

Abstract

Device for measuring a path, in particular the path of a brake pedal in the case of a motor vehicle, characterized by at least one detector (2, 4), operating in an analog manner, which outputs a signal analog as a function of the path to be measured, and at least one detector (7, 8) which operates incrementally, and which delivers, as a function of the path to be measured, a signal consisting of a series of pulses, the analog signal and the signal formed by a series of pulses that can be related to each other to determine the path to be measured.

Description

I State of the Art The present invention relates to a device and a

  method for determining a route, in particular the

  brake pedal travel of a motor vehicle.

  Route sensors are needed, for example in the case of electro-hydraulic brakes, to sense the route taken by the brake pedal. Habitually

  from a course signal taking into consideration

  tion a master cylinder pressure signal and a signal

  provided by the stop light switch,

  ends the driver's wish to brake, and we repeat it

  transmits either as the setpoint brake pressure or as the setpoint deceleration of the vehicle to

  braking adjustment devices and it is adjusted for this

  law. This detection of the driver's wish is an operation which strongly concerns safety and which requires

  consequently high availability of the parking sensor

course used.

  Course sensors detect positions

  Travel conditions usually by means of measurement methods which use friction contacts or also contactless methods. Typical types of detectors

  are core-plunger systems that operate

  operate for example by induction, in particular differential transformers. Potentiometer detectors or Hall detectors are also used many times in conjunction with permanent magnets. It can be used as incremental detectors, which deliver as signal

  a series of pulses, in particular ba detectors

  optical or magnetic scanning layering, in particular

  Hall elements or AMR elements (magnetoresistance aniso-

  tropic). Numerous digital route detectors are also used many times with absolute programming scales (optically or magnetically). The disadvantage in the case of conventional path detectors is that they are not cut to the length of the measurements

  of course in suitable security systems. The trust

  bility and precision that are required, in the case

  electro-hydraulic braking, for example for

  sensors used to capture the course of the brake pedal, is only possible with detection arrangements

  very expensive or signal reprocessing circuits.

  Document DE-OS 196 25 058 discloses a device used to determine a rotation rate with a

  first detection system which delivers a signal in operation

  tion of the turnover rate, and operates according to a first

  measuring principle, with means of exploiting the

  which determine the turnover rate from the

  general, device in which there is provided in addition a second detection system, which delivers a signal which is a function of the rotation rate and operates according to a

  second measurement principle, the signals of the second system

  detection tem being brought to the means of processing the signals and being at the same time taken into consideration when determining the rotation rate. As a first detection system, an electronic compass is provided in this case, which delivers an output signal, which is a function of the earth's magnetic field, and as a second detection system, an oscillating structure is provided,

  which delivers a signal which is a function of the force of Co-

  riolis. The subject of the invention is the definition of a

  measuring device with which one can indicate in a ma-

  a simple and reliable route, in particular the

  brake pedal in a motor vehicle.

  This problem is solved by means of a device serving to measure a course, in particular the course of a brake pedal in the case of a motor vehicle, characterized by at least one detector, operating in an analog manner, which delivers an analog signal as a function of the path to be measured, and at least one detector which operates incrementally, and which delivers as a function of the path to be measured a signal constituted by a

  series of pulses, the analog signal and the signal con-

  formed by a series of pulses which can be brought into relation with each other to determine the path to be measured.

  The invention also relates to a method for

  before measuring a course, in particular a brake pedal course in a motor vehicle, using a device of the type concerned above, method comprising the following sequences:

  * determination of at least one analog signal in function

the route to be measured,

  * determination of at least one incremental signal in function

the route to be measured, and

  * connection of the analog signal and the signal

  incremental to get a signal that represents the par-

  course to be measured, taking into account both the

  analog signal as the incremental signal.

  The device according to the invention has the advantage of being able to perform particularly reliable and precise measurements. In this case it is particularly advantageous that the device according to the invention can be manufactured

  under economic conditions as well as the fact of

  see doing probability research without an im-

  bearing, and to have a quasi redundant system because we

  has another signal at all times

  signal failure. These advantages are obtained through

  fact that we realize a combination of two independent units

  pendants of detectors to measure routes in a single system, the combination taking place in such a way

  that the disadvantages of individual systems are minimal

  bet and that we have the respective advantages of the systems

  individual. The output signals from the two detection systems

  tectors are combined with each other for the calculation, the

  combination taking place in corresponding means of ex-

  signal processing, for example in the form of micro-

  processors. The device according to the invention responds both from the point of view of the manufacturing technique and from the functional point of view to the severe requirements imposed on

  a pedal path detector.

  Advantageous embodiments of the dis-

  positive according to the invention and the method according to the invention

  are the subject of the subclaims.

  According to an advantageous configuration of the device

  tif according to the invention it has two detectors which operate in an analog manner and / or two detectors

  which work incrementally. In this way

  lesson we have a redundancy which even in the event of failure of a detector working in an analogical way or of a detector working in an incremental way allows a combination by the calculation of an analog signal and a signal formed by a series of pulses. In addition

  we can combine one with the other for example the two if-

  gnals formed by a series of pulses to obtain a

  which has a higher resolution.

  According to a higher embodiment of the present invention at least one of the detectors which functions in an analog manner is constituted under the

  form of a Hall element which cooperates with a magnetic bar

  tick. Detectors of this type are available at very advantageous prices and deliver measurement results.

  reliable and accurate. In addition Hall elements are of cons-

  very small truction. For example, it would also

  likely to use AMR (Anisotropic Magnetoresistance) detectors. It is further advantageous that at least one

  detectors that work incrementally

  is constituted in the form of a Hall switch

  cooperating with a series of magnetic alternations. De-

  tectors constituted in this way can also be

  built in a very small way and turn out to be in pra-

very reliable tick.

  According to another preferred embodiment at least one of the detectors which operate in an incremental manner is constituted in the form of an opto-incremental detection system. With a detection system

  of this type one can reach particular resolutions-

high.

  Appropriately the detector which functions

  incrementally consists of

  means used to determine and / or identify a

  indexing father, by reference to which the signal formed by

  a series of pulses can be defined. By means of a re-

  Indexing father of this type, a particularly reliable and precise measurement of a path can be indicated on the basis of the signal formed by a series of pulses. In addition, the analog signal can also be defined by reference to

an indexing mark of this type.

  The means for determining and identifying an index mark are suitably constituted

  in the form of a Hall switch cooperating with an

  magnetic tarnish or in the form of a detection system

opto-incremental tion.

  According to a preferred configuration of the device

  according to the invention the magnetic bars and the alternating

  these are put on a piston rod, especially a

  compression rod of a brake master cylinder

  motor vehicle, and Hall elements and switch

  Hall are put on a housing that surrounds the piston rod.

  In this way one can obtain an embodiment having a particularly compact construction of the

device according to the invention.

  It is preferable that the detectors that operate

  are incrementally arranged in such a way

  so that they deliver signals taking place in a ma-

  90 phase shifted relative to each other. We can reprocess signal sequences of this type in a simple way by calculation to obtain a resolution

precise route.

  According to a preferred configuration of the process,

  lon the invention calibrate at least one of the analog signals

  giques by means of at least one signal constituted by a series of pulses, the values of the analog signal being associated respectively with the values of the signal constituted

by a series of pulses.

  Appropriately, a value is determined from a difference between the values of the analog signal and of the signal constituted in the form of a series of pulses.

  correction for the analog signal.

  Appropriately connecting the si-

  analog and signal consisting of a series of pulses takes place taking into account a

  indexing mark of the incremental signal.

  According to an advantageous configuration of the method according to the invention, two incremental signals phase shifted relative to each other at 90 are determined, a quadrature signal being determined on the basis of these signals. A quadrature signal has a higher resolution than individual incremental signals, so

  that it is possible to determine on its very precise basis-

the path of the pedal.

  Appropriately after switching on the device according to the invention until the indexing mark is identified, the path to be measured is determined on the basis of the analog signals. Thanks to this measure we take for example into consideration the fact that after the ignition of a motor vehicle is connected

  already apply the brake pedal so that

  is a security measure, not using or

  to consider as invalid the incremental signal until

  at the first identification of the indexing mark.

  The present invention will be described below

  in more detail from an embodiment, shown

  shown in the accompanying drawings, in which: * FIG. 1 shows a lateral sectional view of a preferred embodiment of the device according to the invention used to measure a route, * FIG. 2 shows a sectional view of the device according to line II of figure 1, * figure 3 shows the signals or the sequences of

  signals that occur in the case of a preferred form

  implementation of the method according to the invention.

  In Figures 1 and 2 is shown by the

  reference 1 the housing of a piston rod 6, in particular

  link of a compression rod of a brake master cylinder of a motor vehicle. The piston rod 6 can

  slide inside the housing 1 depending on the ac-

  operation of a brake pedal (not shown). To detect the position of the piston 6 inside the housing 1, there are provided according to the embodiment shown in Figures 1 and 2 different detection systems. A first detection system consists, in the example of

  shown, in two elements Hall 2, 4 functions

  analogously operating, which deliver by cooperating

  with two magnets 3 and 5 two analog output signals

  ques. The Hall elements 2, 4 are in this case integrated in the housing 1, and the magnets 3, 5 in the form of bars are

  integrated into the piston rod 6. In principle, the sensitivity

  lity and linearity of such an arrangement after an adaptation

  The dimensions of the magnets and the parameters of the Hall elements are suitable for the path to be measured for the requirements imposed, for example in the case of electro-hydraulic braking. The magnets 3, 5 are constructed in the piston rod 6 in such a way that their poles of the same name, in the embodiment shown as

  for example the south pole S, touch by their frontal side.

  Thanks to the corresponding arrangement of the Hall elements 2, 4 operating in an analog manner, there occurs during the sliding of the piston rod 6 two unwinds of the voltages of the signals U2, U4 in opposite directions, as they have been represented in principle on Figure 3, bottom. Of

  Hall components appropriately amplify

  internal generator, which is designed so that the

  sions of signals in connection with inexpensive Alnico magnets are in the area between 1 volt and 4 volt, so there is no need to have

  further amplification of the detector output signals

  Hall tors. The individual length of the bar-shaped magnets 3, 5 is suitably chosen such that it is greater than the maximum path to be measured of the piston rod 6 (path of the pedal of

brake).

  Another detection system, unlike the first detection system, is constituted under the

  form of an incremental system. In the example of realization

  tion shown the second detection system consists

  in Hall switches 7, 8, which cooperate with a se-

  Rie of alternating magnetic poles 10. The alternating poles 10 are, in a manner analogous to the two magnets 3.5 in the form of bars of the housing 1, components which are an integral part of the piston rod 6. They are of

  preferably made of magnetizable and insertable materials

  res in the form of bands in the piston rod 6. The in-

  Hall switches 7 and 8 are arranged in such a way that they deliver, in connection with the series of alternating magnetic poles 10, two sequences of signals of rectangular shape A, B, which are 90 ° out of phase with each other , as shown in Figure 3 above. We arrive at this for example thanks to the fact that the

  geometric distance from the magnetic centers of the interrup-

  Hall 7, 8 reaches n. (0.5.a) times the distance from the cen-

  very magnetic poles (in this case n is an integer and a is the width of a polar alternation or the distance between the centers of the poles). It is for example

  possible to establish alternating poles with dis-

  tances between centers of 1 mm, so that in

  such a case for example the distance from the centers of the two in-

  breakers Hall 7, 8 can reach 4.5 mm. By means of a rectangular signal of this type phase shifted to 90 or to n / 2, it is possible (using known operating techniques) to carry out with a microcontroller 13 an identification of the direction of movement of the piston rod 6. If one exploits in addition the rising and falling sides of the two series of rectangular pulses, one obtains by alternation of the poles four pulses (quadrature). It is therefore possible to obtain, in the case of a polar distance of for example 1 mm, a resolution of 0.25 mm of the path. The quadrature signal Q such as that which is generated and which is exploited by means of the microcontroller 13, is represented in FIG. 4,

line 3.

  Another Hall switch 9 is used to scan a

  separate polar alternation 11, which forms an information mark

  dexation (see Figure 3, line 4, signal I). The signal

  incremental is defined starting from this index mark-

  tion. The incremental path detector delivers in con-

  sequence in total three signal sequences, namely signals A, B, I, shown in Figure 3, which are put

  at the input of an operating circuit or microcontroll-

their 13.

  In the embodiment shown the magnets 3, 5 in the form of bars form an integral part of the piston rod 6, while the Hall detectors 2, 4 respectively associated are located in the housing 1 of the piston rod 6. The housing 1 may consist of such

  so that it has a through bore, in the-

  which moves the piston rod 6, that is to say a U-shaped recess with which the detection block can be put on the piston rod 6. To have the assurance that the Hall elements 2, 4 as well as the Hall switches 7, 8, 9 are placed in the correct position relative to the magnets 3,, 10, 11 or remain in the correct position, we realize

  rotational locking thanks to the fact that the outer contour

  of magnets 3, 5 protrudes from the outside diameter

  laughing rod 6 and engages in a corresponding enlargement 20a of the passage bore 20 (see Figure 2). Thanks to this configuration of the magnets 3, 5 or the passage bore 20, it is guaranteed to have a

  rotation lock in the case of a possibility without

  mite for the piston rod 6 to slide inside the housing 1, for which no additional component is necessary. The housing 1 is further constituted with a recess, in which are housed a wiring support 14

  and the microcomputer 13, including the necessary components

  saries to its functioning such as for example the voltage regulator, a quartz, etc. The microcontroller is connected

  for example by means of lines 12 to a communication device

brake system command.

  To obtain higher resolutions we can also set up the incremental detection system

  in the form of an opto-incremental detection system.

  In such a case the polar alternations 10 are replaced by a series of holes, which is located in a support in

  form of ribbon, which projects laterally from the rod of the

  your. The scanning of this series of holes takes place for example with a coding block, such as that which is produced by II the company Hewlett Packard (HEDS 97 02). With elements

  of this type, resolutions of 0.05 mm can be obtained.

  It is also possible to use landmarks

  indexing res using opto-incremental systems.

  It is also conceivable to use combinations of

  magneto-incremental systems and opto-systems

  incremental. In this case it is for example possible to obtain the signal constituted by a series of pulses at the

  means of an optical encoder and to realize the information marks

  dexation by a magnetic polar alternation and an inter-

  corresponding Hall breaker. The incremental course detection system delivers, after identification of the indexing marks, a very precise course signal. This course signal does not need to be calibrated, because in principle there is no offset and no faults

  of linearity. Due to the incremental operating mode

  neither does the route signal show any

  temperature dependence. However as a disadvantage

  in the case of a purely incremental operating mode

  tiel, we have from time to time the fact that in case of non-identi-

  tification of the indexing mark, no absolute position of the course can be deduced. By combining the incremental detection system with the analog system described

  above, this drawback is eliminated.

  The incremental course signal can be

  used to calibrate the two measurement systems

  courses running analog or detectors

  2, 4. For this purpose, plug in during a start-up procedure.

  rage the microcontroller 13, which exploits the detection signals, by means of corresponding software on a calibration mode. To carry out the calibration procedure, it is necessary to actuate the piston rod 6 once over the entire path to be measured. In this case the indexing mark 11 or the signal I of the incremental system must be identified. Beginning with the detection of the indexing mark, the two voltage values of the

  analog Hall detectors 2, 4 by means of an analog-to-digital converter (not shown) in the microcomputer. In this case, a measurement value of the incremental system is associated with their respective voltage value5. From a difference between the analog values and the values

  their determined incrementally, a correction value is calculated for the strongly non-linear analog path signals of the Hall 2 and 4 detectors, and for example it is placed in a table in the micro-

  computer 13 (EEPROM - memory erasable per channel

  electronic). It is also possible to measure the tem-

  ambient temperature of the device by means of a temperature detector (not shown).

  correct the typical temperature run of the two de-

  Hall tectors 2, 4 operating analogically, when this is necessary for reasons of minimization of measurement errors. Signal correction takes place in

  this case for example using software in the micro-

  computer. The illustrated calibration procedure is not necessary.

  only once, for example when mounting the system in the vehicle. The prerequisite for this type of detector calibration is to have an interface

  which works bidirectionally at the outlet of the

  guardian, a CAN (Controller Area Network) interface for

  before being used in this case preferably.

  As a result of the calibration procedure, there are available for generating the path signal to be delivered from three signals independent of each other, namely the output signal, corrected or linearized, of the Hall 2 detector which operates in analog manner, the signal of corrected or linearized output of Hall 4 detector which works analogically and the signal from the three switches

  Hall 7, 8 and 9 obtained by squaring and counting the increments

ment.

  A typical possibility of applying the provision

  sitive according to the invention for the operation of a vehicle

  motor cule will now be described in detail. After

  having connected the ignition of the motor vehicle, you must

  firing of the fact that the brake signal can be actuated. In such a case, the output signal of the detection system 8, 9, 11, which operates incrementally, is first considered as invalid, because there is no

  yet identified the indexing mark, which is the condition

  prerequisite for initialization of the incremental system

  tiel. For this reason, one of the two signal signals is used.

  output of system 2, 4, which operates in an analog

* only to generate the output signal from the parking detector

  Classes. In the illustrated embodiment, the Hall 2 detector is used, for example, which operates in an analog manner. Its output voltage (linearized by means of the calibration described above) is for example delivered after various probability searches which we will have to explain later, by means of the CAN interface

(Controller Area Network).

  During the next course after the branch-

  of the ignition there will be an instant during which the

  brake pedal will be released. By means of a configuration

  tion corresponding to the construction of the arrangement of the Hall switch 9 or of the index mark 11 it is ensured, in the case where the brake pedal is not actuated, that the index mark 11 is securely identified by Hall switch 9. The identification of the index mark 11 triggers, in particular by being

  controlled by software, a conversion of the metering system

  on analog in incremental measurement system, so that during the following sequence it is possible to deliver a measurement value, which is obtained digitally, and

  which does not have an offset or lack of sensitivity

  through the CAN interface of the computer.

  There is a limitation in the accuracy of the digital signal due to the resolution that can be obtained from the path signal, resolution which is determined by the

  distance from the magnetic polar alternations. We always leave

  However, as a general rule, it is sufficient to have a resolution, with regard to the path, of 0.25 mm in the case of a path length to be detected of 22 mm. A resolution of this type can be obtained with distances between the centers of the poles of 1 mm and by producing a quadrature signal. If the requirements for path resolution should be higher, there is for example the possibility of interpolating the incremental signal with the help of

  one of the two Hall signals obtained analogically.

  In addition to the possibility represented to have

  very precise detection of the route the principle of

  tection according to the invention also offers the possibility of

  read independent route signals from each other to obtain proper system security. We can

  for example in a first phase control the two

  analog output sions of Hall elements 2, 4 in a subtractor. In the case of a probability of difference

  you can compare the state of the incremental detector counter

  tiel with one of the two output voltages, which exist

  analogically, Hall elements 2, 4 and we can add

  dre valid in this way the detector output signal

  tor. Even if one of the three systems fails

  measurement we can detect the fault. In this case, you can

  apply information via the CAN output of the detector

  without affecting the availability of the detector.

  Another possibility of exploiting si-

  gnals of the detectors received consists in using only the analog travel signals of Hall elements 2, 4 and in using the digital signal only to support these analog values. This mode of action can also be implemented at no additional hardware cost using software

microcomputer 13.

  By means of the device according to the invention, there is a self-calibrating path detector, the output signal of which is largely linear and independent.

  of the temperature. This is guaranteed by the fact that a system

  incremental tem caliber two analog detectors

  to their sensitivity and their shift, the calibration of the

  guardian which can take place on site. The respective signals

  output of the various detection systems of the device according to the invention are combined with each other in a microprocessor, whereby the limitations of the various detectors which exist in

  principle, so that the device as a whole

  ble takes into account the security requirements which are im

  applied to a braking system. It is possible to put

  other detection signals, for example an in-

  switch for the stop lights or a pressure detector signal, in the microcomputer, and to reprocess it at

  new with signals from the different detectors.

Claims (10)

R E V E N D I C A T I O N S   1) Device used to measure a route, in particular   link the course of a brake pedal in the case of a vehicle   motor vehicle, characterized by at least one detector (2, 4), operating in an analog manner, which delivers an analog signal according to the path to be measured, and at least one detector (7, 8) which operates in an incremental manner , and which delivers a signal consisting of a   series of pulses, the analog signal and the signal con-   formed by a series of pulses which can be put in relation   tion with each other to determine the route to be measured. 2) Device according to claim 1, characterized in that   it includes two detectors operating analogously   icing (2, 4) and / or two detectors operating in such a way incremental (7, 8).   3) Device according to one of claims 1 or 2, characterized in that   at least one of the detectors, which operate in a ma-   analog, is constituted in the form of a Hall element (2, 4) which cooperates with a bar-shaped magnet (3, 5).   4) Device according to one of claims 1 or 2,   characterized in that at least one of the detectors (7, 8), which operate in an incremental manner, is constituted in the form of a Hall switch which cooperates with a series of alternations magnetic poles (10).    ) Device according to one of claims 1 to 3,   characterized in that at least one of the detectors which operate in an incremental manner is constituted in the form of an opto-incremental detection system.   6) Device according to one of the preceding claims, characterized in that   the detector (7, 8) which operates incrementally   This is constituted by means (9, 11) which serve to fix and identify an indexing mark, with respect to which the signal constituted by a series of pulses can be defined. 7) Device according to claim 6, characterized in that the means which serve to fix and identify a mark   of indexing are constituted in the form of an interrup-   Hall (9) cooperating with the alternation of magnetic poles   ques (11), or an opto-incremental detection system.   8) Device according to one of the preceding claims 3 to 7, characterized in that   the stick-shaped magnets (3, 5) and the alternations po-   laires (10, 11) are put on a piston rod (6), in particular the compression rod of the master brake cylinder of the motor vehicle, and the Hall elements (2, 4) as well as the Hall switch (7 , 8, 9) are put on a   housing (1) which surrounds the piston rod (6).   9) Device according to one of the preceding claims 2 to 8, characterized in that   the detectors (7, 8) which operate incrementally   are arranged in such a way that they deliver 90-phase phase-shifted signal sequences compared to others.    ) Method for measuring a course, in particular a brake pedal course in a motor vehicle,   using a device according to one of claims   above, method comprising the following sequences:   * determination of at least one analog signal in function the route to be measured,   * determination of at least one incremental signal in function the route to be measured, and   * connection of the analog signal and the signal   incremental to get a signal that represents the par-   course to be measured, taking into account both the   analog signal as the incremental signal.   11) Method according to claim 10, characterized in that at least one of the analog signals is calibrated by means of at least one of the incremental signals, the values of   analog signal being associated respectively with a value   their incremental signal starting from an information mark dexation.   12) Method according to claim 11, characterized in that   a correction value for the analog signal is determined   gic starting from a difference between the values of the signal   analog and incremental signal.   13) Method according to one of claims 10 to 12,   characterized in that two phase-shifted incremental signals are determined, one by   compared to the other of 90 and a quadrature signal is calculated on the basis of these signals.   14) Method according to one of claims 10 to 13, characterized in that   the path to be measured is determined on the basis of the analog signals after switching on the device until the indexing mark is identified.