WO2013152925A1

WO2013152925A1 - Determination of the position of a hydrostatic actuator

Info

Publication number: WO2013152925A1
Application number: PCT/EP2013/055600
Authority: WO
Inventors: Markus Dietrich; Steffen LINZ; Jürgen GERHART
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2012-04-11
Filing date: 2013-03-19
Publication date: 2013-10-17
Also published as: CN104204592A; DE102013204752A1; DE112013002025A5; DE112013002025B4; CN104204592B

Abstract

A hydrostatic actuator comprises a gearing spindle with two elements which are rotatable relative to one another. A magnet element is mounted on the first element, and on the second element there are mounted a first magnetic field sensor for the determination of an absolute angular position of the two elements and a second magnetic field sensor for the provision of a signal indicative of a predetermined rotational position of the two elements. A method for determining a position of the actuator comprises steps for determining a first signal from the first magnetic field sensor and a second signal from the second magnetic field sensor, determining a rotational position of the first element with respect to the second element on the basis of the first signal, and checking the plausibility of the determined rotational position on the basis of the second signal. A control unit is provided for executing the method. A position sensor comprises the two magnetic field sensors for providing a first signal, which is indicative of the absolute position of the first element with respect to the second element, and a second signal, which is indicative of a predetermined rotational position of the two elements.

Description

Position determination of a hydrostatic actuator

The invention relates to a hydrostatic actuator, in particular for actuating a

Friction clutch in a motor vehicle. In particular, the invention relates to a technique for determining a position of the hydrostatic actuator.

In a powertrain, such as a motor vehicle, a clutch is provided to selectively interrupt the powertrain. The clutch is hydraulically actuated, wherein in the region of the clutch, a hydraulic slave cylinder is arranged, which is connected via a pressure line with a hydraulic master cylinder. The master cylinder is displaceable by means of a gear spindle by an electric motor, so that the electric motor can be controlled to engage or disengage the clutch.

In order to allow accurate control of the state of the clutch, it is necessary to determine an opening degree of the clutch as accurately as possible. For this purpose, a rotational position can be removed on the gear spindle, whose position is sufficiently accurately coupled with the opening degree of the clutch.

To sense the rotational position, sensors are available which determine the position of a permanent magnet on the gear spindle based on the magnetic field of the permanent magnet and convert it into a signal indicative of the rotational angle of the spindle. The quality of the sensor in terms of probability of failure and failure frequency can be expressed in classes such as those defined by the standard ISO CD 26262 "ASIL." The higher the ASIL class of the sensor, the more expensive the manufacture and the more expensive the use of the sensor The object of the invention is to improve the quality of a sensor signal beyond the classification of the assigned sensor.

The invention solves this problem by means of a method, a control device and a position sensor and the features of the independent claims. Subclaims give preferred embodiments again. A hydrostatic actuator comprises a gear spindle with two mutually rotatable elements. The first element has a magnetic element and the second element has a first magnetic field sensor for determining an absolute angular position of the two elements and a second magnetic field sensor for providing a signal indicative of a predetermined rotational position of the two elements. A method for determining a position of the actuator includes steps of determining a first signal of the first magnetic field sensor and a second signal of the second magnetic field sensor, determining a rotational position of the first relative to the second element based on the first signal, and plausibility checking the determined rotational position on the base of the second signal.

The plausibilized signal may have a quality that is above the classification of the first magnetic field sensor without the second magnetic field sensor having a higher classification than the first magnetic field sensor. As a result, the position of the hydrostatic actuator can be determined in a simple and cost-effective manner, whereby an accurate and highly reliable control of the actuator can be made possible.

In one embodiment, a rotational position determined on the basis of the first magnetic field sensor, which corresponds to the signal of the second magnetic field sensor, is compared with a stored rotational position and accepted as plausible if it does not deviate more than a predetermined amount from the stored rotational position. For this, a determination of the rotational position based on the signal of the first magnetic field sensor may be performed when the signal of the second magnetic field sensor arrives, or one of a series of rotational positions determined on the basis of the signal of the first magnetic field sensor may be selected corresponds to the signal of the second magnetic field sensor, for example on the basis of time stamping of the signals. In a learning phase, the rotational position to which the second signal is provided can be determined. As a result, the method can be adapted to a specific arrangement of magnetic field sensors, so that, for example, manufacturing tolerances can be compensated.

In a further embodiment, the stored rotational position comprises an interval which contains the predetermined rotational position to which the signal of the second magnetic field sensor points. By a suitable choice of the interval, a tolerance of the method against small deviations between the signals can be controlled. Alternatively, it can also be determined whether the determined rotational position deviates from the stored rotational position by more than a predetermined amount. An inventive control device is adapted to determine the rotational position of the first element with respect to the second element by means of the described method. The control unit may be embodied integrated with the arrangement of magnetic field sensors and may also be optionally configured to carry out further control tasks, for example the control of an electric motor for driving the hydrostatic actuator.

A position sensor for providing signals for determining a position of the described hydrostatic actuator comprises a magnetically fixed to the first element magnetic element, a first magnetic field sensor, which is rotatably mounted with respect to the second element, for providing an indicative of the absolute angular position of the elements signal, and a second magnetic field sensor rotationally fixed with respect to the second element, for providing a signal indicative of a predetermined rotational position of the two elements.

The position sensor according to the invention requires compared with a known, absolute position sensor only a second magnetic field sensor, which does not have to have a high ASIL classification. The existing magnetic element can be used for both magnetic field sensors, whereby costs can be saved. In a preferred embodiment, the second magnetic field sensor provides a digital signal, in particular a rising or falling edge of a bivalent signal, when the two elements occupy the predetermined rotational position relative to one another. On the basis of the flank, a control unit which can be connected to the position sensor can be prompted precisely in time for scanning the signal of the first magnetic field sensor, whereby the correlation of the signals of the two magnetic field sensors can be improved. Such a digital magnetic field sensor may also be available as a low cost integrated device.

It can be provided a plurality of circumferentially offset further second magnetic field sensors. Thereby, several signals can be provided per revolution of the first with respect to the second element, each of which indicates a different predetermined rotational position. The plausibility check can thus be carried out with increased frequency, as a result of which an even higher quality of the position determination can be made possible.

In another alternative that can be combined with the above, the magnetic element may comprise a first magnet associated with the analog magnetic field sensor and a plurality of circumferentially offset second magnets corresponding to the second magnetic field. sensor are assigned. Thus, the number of signals of the second magnetic field sensor per revolution of the first with respect to the second element can also be increased. Compared to the last-mentioned embodiment, although the structure of the magnetic element is more complicated, the second magnetic field sensor is less complex for this purpose.

The processing device may be configured to output an error signal if the signals provided by the magnetic field sensors do not correspond to one another. Thus, a processing device that further evaluates the specific position may be actively informed of a problem in determining the actuator position. Error handling by the processing device can thereby be supported. Optionally, the rotational position determined by the position sensor in the event of a fault can be used under reserve.

The position sensor may further comprise processing means for plausibility checking the absolute angular position determined on the basis of the first magnetic field sensor by means of the signal of the second magnetic field sensor, and transmission means for transmitting the signals of the magnetic field sensors to the processing means via a data bus. Thus, partially processed signals can be transmitted via the data bus, in particular a control bus on board a motor vehicle, in order to enable a final processing in a control unit, which is assigned further tasks or even more signals are provided, which can be combined with the partially processed signals ,

The invention will now be described in more detail with reference to the attached figures, in which:

Figure 1 is a hydraulic clutch actuation with a position sensor;

Figure 2 is a magnetic element of the position sensor of Figure 1;

Figure 3 signals from sensors of the position sensor of Figure 1, and

FIG. 4 shows a flow chart of a method for determining the position of the hydrostatic actuator from FIG. 1; represents. FIG. 1 shows a hydraulic clutch actuation 100 with a position sensor 105. The clutch actuation 100 is configured to actuate a clutch 10, in particular an automated clutch in a drive train of a motor vehicle. The clutch actuator 100 includes a master cylinder 1 15, which is connected via a designated also as a pressure line hydraulic line 120 with a slave cylinder 125. In the slave cylinder 125, a slave piston 130 is movable back and forth, which operates via an actuator 135 and usually with the interposition of a bearing 140 constructed as a double friction clutch clutch 1 10.

The master cylinder 1 15 is connected via a connection opening with a surge tank 145. In the master cylinder 1 15, a master piston 150 is movable back and forth. From the master piston 150 is a piston rod 155, which is translationally movable in the longitudinal direction together with the master piston 150. The piston rod 155 of the master piston 150 is coupled via a threaded spindle 160, which is preferably designed as a magnet-Wälz- threaded spindle, with an electric motor actuator 165. The threaded spindle 160 comprises a first element 170, which is designed here as a spindle, and a second element 175, which is designed here as a socket. The position sensor 105 is configured to determine a rotational position of the first member 170 relative to the second member 175. For this purpose, the position sensor 105 comprises a magnet element 180 rotationally fixed to the first element 170 and a first magnetic field sensor 185 and a second magnetic field sensor 190, which are mounted rotationally fixed relative to the second element 175.

Furthermore, the position sensor 105 comprises an evaluation circuit 200, which may be constructed in different ways. In one embodiment, the evaluation circuit 200 comprises only one processing device that performs all the tasks required to process the signals. The evaluation circuit 200 shown comprises a first processing device 215 which is connected to the first magnetic field sensor 185, a second sampling device 210 which is connected to the second magnetic field sensor 190, a first processing device 215 and a second processing device 220 which are connected to the first sampling device 205 or to the first sampling device 205 The second scanning device 210 is connected. The processing means 215, 220 process the signals provided by the samplers 205, 210 so as to be correlated with each other. For plausibility of the signals may be a third processing means 225, which may be integrated with the elements 205 to 220 or, as shown in Figure 1, discretely constructed thereof. In the illustrated embodiment, a bus driver 230 is provided to facilitate the third processing. processing device 225 by means of a data bus 235, which must not only be included cheaper by the evaluation circuit 200, tie.

The third processing device 225 has the task of the rotational position of the first

To determine elements 170 relative to the second element 175 based on signals of the first magnetic field sensor 185 and to plausibilize on the basis of the signals provided by the second magnetic field sensor 190. The position determined by the third processing device 225 can thereby have a reliability which lies above the reliabilities of the elements of the position sensor 105, in particular above the reliabilities of the magnetic field sensors 185 and 190.

FIG. 2 shows the magnetic element 180 of the position sensor 105 from FIG. 1. In a simple embodiment, the magnetic element 180 comprises only a single magnet 180.1, which is non-rotatably and preferably coaxially connected to the first element 170 of the threaded spindle 160. The first magnetic field sensor 185 is preferably also mounted coaxially with the first element 170 in the region of the first magnet 180.1. The first magnetic field sensor 185 provides a signal indicative of the direction of the magnetic field. From this signal, the rotational position of the first element 170 with respect to the second element 175 can be determined, wherein this determination can be performed integrated within the first magnetic field sensor 185.

The second magnetic field sensor 190 may also be an analog magnetic field sensor, which is preferably arranged coaxially or axially close to the first magnet 180.1. In another preferred embodiment, the second magnetic field sensor 190 is arranged digitally and at a radial distance from the axis of rotation of the first element 170 of the threaded spindle 160. The digital magnetic field sensor 190 provides a digital signal, with a rising or falling signal edge indicative of a predetermined rotational position of the elements 175 and 180. The second magnetic field sensor 190 may in particular comprise an integrated Hall sensor with digital output. If the digital magnetic field sensor 190 is arranged in the region of the individual magnet 180.1, it usually provides a digital signal which comprises one rising and one falling edge per revolution of the first element 170. In different embodiments, only one or both edges can be evaluated.

To a greater number of rising and falling edges per revolution of the first

To achieve elements 170, a plurality of second magnetic field sensors 190 may be included are offset in the circumferential direction in the region of the magnet 180.1. In another embodiment, a coaxial ring may be provided by the second magnet 180.2, wherein the second magnetic field sensor 190 is arranged in the region of the second magnet 180.2. The two measures can also be combined so that a plurality of second magnetic field sensors 190 are arranged in the region of the plurality of second magnets 180.2.

FIG. 3 shows signals of the magnetic field sensors 180 and 190 of the position sensor 105 from FIG. 1. With regard to FIG. 2, it is assumed that the second magnetic field sensor 190 is mounted in the region of the first magnet 180.1 and no second magnets 180.2 are provided. In the horizontal direction, a rotation angle and in the vertical direction, a signal is plotted. A first curve 305 corresponds to the signal of the first magnetic field sensor 185 and a second curve 310 to the signal of the second magnetic field sensor 190. It becomes clear how the rising or falling edges of the digital signal in the second curve 310 correspond to predetermined rotational positions on the basis of the signal of the first signal 305 can be determined.

Depending on the position of the second magnetic field sensor 190 in the circumferential direction, the

Rotation positions, to which a rising or falling edge of the second curve 310 takes place, to be shifted in the horizontal direction. A horizontal shift may also occur on the basis of series variations or temperature effects. Preferably, however, the relationship between an edge of the second curve 310 and a rotational position is known, so that whenever the second curve 310 has a flank, on the basis of the first curve 305, the rotational position is determined and compared with the associated known rotational position. If the determined rotational position coincides sufficiently precisely with the predetermined rotational position, then the specific rotational position is plausible. Otherwise, an error in the area of the position sensor 105 must be assumed.

FIG. 4 shows a flowchart of a method 400 for determining the rotational position of the gear spindle 160 from FIG. 1. In a first step 405, the system waits until a signal for determining the rotational position arrives. Such a signal is usually generated periodically. If the signal has arrived, then in a step 410 the signal provided by the first magnetic field sensor 185 is determined or sampled. On the basis of the determined signal, the rotational position of the first element 170 with respect to the second element 175 of the threaded spindle 160 is then determined in a step 415. This provision is performed by the first processing device 215 in the embodiment shown in FIG. Subsequently, the determined rotational position is transmitted in a step 420 to the third processing device 225, if this is provided.

Regardless of this, the signal of the second magnetic field sensor 190 is scanned in a step 425. If it is an analog magnetic field sensor, processing according to steps 410 and 415 may follow. If it is a digital magnetic field sensor 190, then step 425 may include detecting a falling or rising edge of the provided signal, as described above with reference to FIG. In a following step 430, which corresponds to step 420, the second signal is also transmitted to the third processing device 225. The transmission of steps 420 and 430 may include providing the sampled signal with a measurement time and possibly a checksum in a data message.

In a step 435, the messages transmitted in steps 420 and 430, respectively, arrive at the third processing means 225 and are received. In the case of a digital second magnetic field sensor 190, in a step 440, one or more references to a rotational position of the first element 170 with respect to the second element 175 are obtained from a memory. The instructions may be kept in the form of absolute rotational positions or in the form of intervals.

Then, in step 445, it is checked whether the rotation position determined in step 415 is plausible, that is, sufficiently close to the predetermined rotation position. If this is not the case, an error signal is output in a step 450. Otherwise, a plausible rotation position is available in a step 455. This rotational position can be converted in a subsequent step 460 into a translational position of the first element 170 with respect to the second element 175. Both positions are characteristic of an opening degree of the clutch 1 10. One of the two positions can be used in the following to control the electric motor actuator 165 so that a predetermined time course of the opening or closing of the clutch 1 10 results. LIST OF REFERENCE NUMBERS

100 clutch actuation

102 hydrostatic actuator

105 position sensor

1 10 clutch

1 15 master cylinder

120 pressure line

125 slave cylinder

130 slave pistons

135 actuator

140 bearings

145 expansion tank

150 masterbatches

155 piston rod

160 threaded spindle

165 electromotive actuator

170 first element

175 second element

180 magnetic element

180.1 first magnet

180.2 second magnet

185 first magnetic field sensor

190 second magnetic field sensor

200 evaluation circuit

205 first scanning device

210 second scanning device

215 first processing device

218 storage device

220 second processing device

225 third processing device

230 bus drivers

235 data bus

305 first course

310 second course

400 procedures 405 wait

410 determining first signal

415 Determine rotational position

420 sending on CANbus

425 second signal

430 sending on CANbus

435 Receiving CANbus

440 interval from memory

445 rotational position in interval?

450 output error signal

455 plausibilized rotational position

460 translational position determine

Claims

P120330-10

WO 2013/152925 PCT / EP2013 / 055600

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claims

A method (400) for determining a position of a hydrostatic actuator (102) with a gear spindle (160), wherein

the transmission spindle (160) comprises two mutually rotatable elements (170, 175); a magnetic element (180) is attached to the first element (170);

on the second element (175) a first magnetic field sensor (185) for determining an absolute angular position of the two elements (170, 175) is mounted, and on the second element (175) a second magnetic field sensor (190) for providing one to a predetermined rotational position of the two Elements (170, 175) indicating signal is attached,

the method comprising the steps of:

Determining (410) a first signal of the first magnetic field sensor (185) and a second signal of the second magnetic field sensor (190);

Determining (415) a rotational position of the first (170) with respect to the second element (175) based on the first signal, and

Plausibility (445) of the determined rotational position based on the second signal.

The method (400) according to claim 1, wherein a rotation position determined on the basis of the first magnetic field sensor (185) corresponding to the signal of the second magnetic field sensor (190) is compared with a stored rotation position and accepted as plausible, if not more than one Predetermined measure deviates from the stored rotational position.

The method (400) of claim 2, wherein the stored rotational position comprises an interval including the predetermined rotational position to which the signal of the second magnetic field sensor (190) is indicative.

Control unit (200) for determining a position of a hydrostatic actuator (102) with a transmission spindle (160), wherein the transmission spindle (160) comprises two mutually rotatable elements (170, 175) and on the first element (170) comprises a magnetic element (180) and a first magnetic field sensor (185) for determining an absolute angular position of the two elements (170, 175) and a second magnetic field sensor (190) attached to the second element (175) for providing a signal indicative of a predetermined rotational position of the two elements (170, 175) and the controller (200) is adapted to adjust the rotational position of the first member (170) relative to the second P120330-10

WO 2013/152925 PCT / EP2013 / 055600

The second element (175) can be determined by means of a method (400) according to one of the preceding claims.

5. position sensor (105) for providing signals for determining a position of a hydrostatic actuator (102) with a gear spindle (160), wherein the gear spindle (160) comprises two mutually rotatable elements (170, 175), and the position sensor (105) comprising:

a magnetic member (180) mounted non-rotatably on the first member (170);

a first magnetic field sensor (185) rotationally fixed relative to the second member (175) for providing a signal indicative of the absolute angular position of the elements (170, 175), and

a second magnetic field sensor (190) rotationally fixed relative to the second member (175) for providing a signal indicative of a predetermined rotational position of the two members (170, 175).

6. position sensor (105) according to claim 5, wherein a plurality of circumferentially offset second magnetic field sensors (190) are provided.

A position sensor (105) according to claim 5 or 6, wherein the magnetic member (180) comprises a first magnet (180.1) associated with the analog magnetic field sensor (185) and a plurality of circumferentially offset second magnets (180.2) corresponding to the first magnet associated with the second magnetic field sensor (190).

The position sensor (105) according to any one of claims 5 to 7, wherein the processing means (215, 220, 225) is arranged to output an error signal if the signals provided by the magnetic field sensors (185, 190) do not correspond to each other.

9. position sensor (105) according to any one of claims 5 to 8, further comprising a processing means (225) for plausibility of the determined based on the first magnetic field sensor (185) absolute angular position by means of the signal of the second magnetic field sensor (190), and transmission means (230 ) for transmitting the signals of the magnetic field sensors (185, 190) to the processing means (225) via a data bus (235).