WO2009000576A2

WO2009000576A2 - Method and device for detecting the rotation direction of a drive unit

Info

Publication number: WO2009000576A2
Application number: PCT/EP2008/055174
Authority: WO
Inventors: Stefan Heimburger
Original assignee: Robert Bosch Gmbh
Priority date: 2007-06-27
Filing date: 2008-04-28
Publication date: 2008-12-31
Also published as: DE102007029708A1; WO2009000576A3

Abstract

The invention relates to a method and a device for detecting the rotation direction of a drive unit, especially of an adjustment drive (64) in a motor vehicle. Said device comprises a motor (12) the rotation direction of which can be reversed by means of switches (20). The speed of the motor (12) is detected by means of at least one incremental sensor signal (56) and is supplied to an evaluation unit (40), a digitized motor current state signal attributing the current motor current to the states -1, 0, +1 being used to evaluate the rotation direction.

Description

description

Title Method and device for detecting the direction of rotation of a drive unit

State of the art

The invention is based on a method and a device for rotational direction recognition according to the preamble of the independent claims.

With EP 0 603 506 Bl a method for determining the position of an electric drive has become known which, for example, electrically actuates an adjustable part in the motor vehicle. In this case, an electric motor is operated such that the direction of rotation of the electric motor can be switched.

To determine the position of the electrically driven part of the time interval of pulse edges of an incremental signal is analyzed after switching off the drive motor. For this purpose, in particular the time interval to the switch-off time is measured and compared with a predetermined measure. In such a device, the distinction between a reversing process of the electric motor and a discharge process may be subject to errors, in particular if the electric motor rotates slightly when it comes to rest under load.

Disclosure of the invention

The inventive method and apparatus according to the features of the independent claims have the advantage that in addition to the one incremental sensor signal, the successive changes of direction of the electric motor can be detected reliably by the use of the current state signal of the electric motor. For this purpose, a qualitative statement about the motor current direction is sufficient, so that the motor current can be assigned a digitized signal which corresponds to the current direction -1 or +1, or a motor current of approx. wisely = 0. This has the decisive advantage that, on the one hand, only a single incremental sensor signal is required for reliable position detection or rotation direction detection, and the outlay for the current measurement can be kept very low on account of the merely qualitative evaluation.

By the measures set forth in the dependent claims advantageous refinements and improvements of the features specified in the independent claims are possible. Since a motor current is induced in the opposite direction when switching off the electric motor in this, a first change of the current state signal can be assigned to the switch-off of the electric motor.

If there is a second change in the current direction, which is measured by a change in the digitized current state signal, this is an indication that the motor is turning back after switching off. This is the case, for example, when a window lift drive is switched off when lifting the disc.

In addition, depending on a change in the engine state signal, the transit time between the flanks of the incremental sensor signal can also be measured, whereby the time segments during a constant motor current state can be compared with empirical values in order to additionally secure the evaluation of the direction of rotation. In this case, the times between the edge changes can be determined particularly favorably by a moving averaging.

To more reliably detect a reversing operation of the electric motor, the times between the edge changes of the incremental transmitter signal can be advantageously compared with previously determined times between the edge changes at a maximum speed of the electric motor. As a result, it can be reliably detected whether the electric motor is decelerated, accelerated or has assumed its normal operating state. Furthermore, in addition, the number of edge changes of the incremental sensor signal can be counted after the turn-off time, which is detected by a change of the current state signal. The number of edge changes can also be compared with an empirical value, which is typical for a reversing operation of the electric motor, for example.

To generate the current state signal, for example, the voltage between the two terminals of the electric motor is measured and evaluated, in particular, even when the electric motor is still a motor current can be measured, the sign for determining the

Direction of rotation can be used. It is particularly favorable if the tapped-off voltage signal in the evaluation unit is fed to an amplifier circuit, since then very small currents can also be detected which flow through the contact resistances of the switches when the electric motor is switched off. This has the advantage that can be dispensed with by the use of the contact resistance of the switch to a separate current measuring shunt, whereby the power loss is reduced, and the complete battery voltage for operating the electric motor is available. As a result of this direct tapping of the voltage signal at the motor contact terminals, the installation space on the printed circuit board is also significantly reduced compared to the current shunt measurement and the relatively expensive shunt is saved. It is particularly advantageous to realize the amplifier circuit as an integral part of a microcontroller, since this is at the same time necessary for determining the position of the part to be adjusted, and possibly for an anti-trap function.

To determine the direction of rotation of the electric motor, it is sufficient if the signal is digitized at the output of the amplifier circuit, which is a measure of the motor current. Since no exact analog measurement signal of the motor current is necessary, it does not matter that the contact resistances of the switch may be subject to certain fluctuations. To determine the direction of rotation of the electric motor, the amplifier circuit is assigned the three motor current states -1, 0 and +1 as a digitized signal. This can be achieved, for example, by dividing the output voltage of the amplifier voltage into different regions to which the corresponding current state is assigned. Due to the - A -

Operating voltage of the microcontroller of about 5 volts, it is particularly favorable to dimension the amplifier circuit such that without current flow through the motor, the amplifier circuit provides a voltage value of approximately 2.5 volts. Since the particular difficulty of detecting the direction of rotation in the area of small currents occurs when the electric motor is switched off or reversed, the amplifier circuit can be dimensioned so that it delivers an amplified signal at high currents, for example greater than +/- 0.5 amperes. whereby the amplifier circuit can be sensitized to the detection of small motor currents.

To generate the incremental sensor signal, for example, a signal generator is arranged on the armature shaft of the electric motor, the signal of which is detected by a housing-mounted signal sensor. The signal generator is designed, for example, as a multipole magnetic ring.

Particularly advantageous is the use of the direction of rotation determination according to the invention in a device for operating an electric motor, which is controlled by relay switches. The amplifier circuit at the motor connection terminals can be integrated directly into the control electronics of the electric motor. Together with the incremental sensor signal can thus achieve a clear characterization of the rotational movement of an electric motor. If the electric motor drives a part to be adjusted, the position of the part can be precisely detected at any time by the method according to the invention and thereby also a jamming protection function can be realized in which, in the case of an obstacle, the part to be adjusted is reversed or stopped in the direction of rotation. The method according to the invention for determining the direction of rotation is also particularly suitable for the use of a central control device, which activates a plurality of electric motors, for example in the motor vehicle.

Brief description of the drawings

Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. Show it

FIG. 1 shows a device according to the invention for detecting the direction of rotation,

Figure 2 schematically shows the inventive method for determining a

Current state signal,

Figure 3 is an illustration of the startup and shutdown behavior of the drive unit and

Figure 4 is an illustration of a reversing process of the drive unit.

Embodiment of the invention

1 shows a device according to the invention for operating an electric motor 12 is shown, which is operated with a voltage source 14, which is formed for example as a battery 16. The voltage source 14 is connected via switches 20 to the electric motor 12, so that by driving the switch 20, the direction of rotation of the electric motor 12 can be reversed. In the exemplary embodiment, the switches 20 are arranged in a relay 18, and will be actuated via a control signal 22 of a control unit 24.

The control signals 22 are generated, for example, by actuating a control button, not shown. If, for example, the left upper relay switch 26 and the right lower relay switch 27 are closed, a motor current 30 flows from the motor terminal 32 marked with + to the motor terminal 34 marked with. If, on the other hand, the switches are closed on the bottom left 28 and 29 on the top right, a motor current flows 30 in the opposite direction from - (34) to + (32). If the electric motor 12 is to be stopped, the relay switches 27 and 28 are closed, so that both motor connection terminals 32, 34 are grounded. If the relay switches 28, 27 closed (dashed lines in Fig. 1), the electric motor 12 is no longer energized from the outside, however, currents are further induced by the inertia of the electric motor 12 for a certain time, via contact resistances 72 of the closed switch contacts 74 of Drain switch 20. Between the motor connection terminals 32, 34 and the respective relay 18 electrical connections 38 are arranged to an evaluation unit 40, which is an e- Tapping lektrisches voltage signal 42, which rests between the motor terminals 32, 34. The evaluation unit 40 has an amplifier circuit 44, which amplifies the tapped voltage signal 42, for example according to FIG. In this case, the amplifier circuit 44 may be formed as part of a microcontroller 46. The amplifier circuit 44 supplies an output signal 48, which enables a determination of a current state signal 50. Furthermore, a speed sensor 52 is rotatably mounted on the electric motor 12, which together with a stationary signal sensor 54, an incremental sensor signal 56 for the speed, or rotational speed delivers. The speed sensor may in particular be formed as a magnetic pole ring 53, which cooperates with a magnetic Hall sensor 55. If this incremental sensor signal 56 is evaluated together with the current state signal 50, this can clearly determine the position of a part 62 of an adjustment drive 64 to be adjusted. For such an adjustment device 64, the evaluation unit 40 can also be designed as anti-pinch protection electronics 60 which are used during anti-pinch protection

Occurrence of an obstacle 66 in the adjustment 68, the electric motor 12 stops or reverses.

In a further embodiment, not shown, the switches 20 are designed as transistors or MOSFETs or in some other way, the transition resistances 72 of which are also detected by means of the amplifier circuit 44 for determining the current direction.

In FIG. 2, the time profile 31 of the motor current 30 is shown in the upper half of the picture and the time profile 47 of the output signal 48 is shown in the lower half of the picture

Amplifier circuit 44 is shown. If, for example, at the time To the electric motor 12, which was previously in the normal driving state, switched off by the two (relay) switches 28 and 27 are closed, thereafter the motor current 30 drops from a normal operating current within a certain period of time 76th until it reaches the value about 0.0 ampere. For a motor current above predeterminable thresholds of, for example, +0.5 ampere or below -0.5 ampere, the amplifier circuit 44 provides a value 78 as an output signal 48 which is either at approximately 5 volts or 0 volts. In this case, the amplifier circuit 44 is in the saturation region. Only after the absolute amount of current has become less than 0.5 amperes does the actual starting point Beitsbereich the amplifier circuit 44, wherein the output signal 48, starting from 5 volts or 0 volts approaches an average value of about 2.5 volts, which corresponds to a current state of 0 amps. For determining the direction of rotation of the electric motor 12, it can now be easily distinguished whether the output signal 48 assumes a value greater than the currentless state 0 corresponding value, or a smaller value. Therefore, the value range of the output signal 48 can be divided into a middle, an upper and a lower range 80, 82, 84, to which a digital Stromzustandssig- signal 50 with the values 0, +1, -1 can be assigned. Thus, without the use of an additional electrical component such as a measuring shunt the

Direction of the motor current 30 and, if appropriate, in conjunction with the incremental sensor signal 56, the rotational speed and the rotational direction of the electric motor 12. Thus, with only a single incremental sensor signal 56 (for example, a single Hall sensor 55) a reliable Position detection and a closing force limit for the part to be adjusted 62 can be realized.

In Fig. 3, the on and off behavior of the electric motor 12 is shown, wherein on the x-axis, the time scale t is shown, and on the y-axis, the measured value 51 for the motor current (dotted curve), the incremental sensor signal 56 (solid Curve) and a direction of rotation signal 86 (dashed curve) is shown. At time t = 0.0, the electric motor 12 is turned on, whereby the current state signal 50 assigned to the signal of the motor current 51 changes from 0 to -1, which corresponds to a motor current in a specific direction. The incremental sensor signal 56 forms a rapid sequence of edge changes 88, which takes place after a short start-up phase in approximately the same time intervals. At the shutdown time 90 t = about 0.19 sec, the electric motor 12 is turned off, whereby in this a motor current is induced in the opposite direction, which is recognizable by the change of the current state signal 50 from -1 to 1. The electric motor 12 continues to run after switching off, so that even after the switch-off time 90 there is still an edge change 91 of the incremental sensor signal 56. By detecting the first current state change from -1 to +1, the edge changes 91 after the switch-off time 90 of the electric motor 12 can be unambiguously assigned to the tracking of the electric motor 12 in the same direction. In Fig. 3 comes it at the time t = about 0.21 to a new power state change from +1 to -1, after which a further edge change 92 of the incremental sensor signal 56 follows. This edge change 92 can be recognized as a return of the electric motor 12 due to the two-time change of the current state signal 50, whereby the direction of rotation signal 86 with the edge change 92 indicates a change in direction of rotation, for example, from left (I) to right (r) as a result of the signal evaluation. Thus, by assigning the edge changes 91, 92 to a change in the current state signal 56, the current direction of rotation of the electric motor 12 can be reliably determined.

4, a reversing process of an electric motor 12 is shown with an enlarged time scale t. In this case, the electrical connection of the electric motor 12 is reversed at time t = approximately 0.465, whereby the current state signal 56 changes from -1 to +1. The time interval 94 between the edge change 88 of the incremental sensor signal 56 increases first and then decreases again until the time interval 94 approximately reaches the value before the changeover point 93. The evaluation unit 40 recognizes the reversing process of the electric motor 12 from the fact that after a single power state change from -1 to +1 additionally the time interval 94 between the edge changes 88 is taken into account. The time interval 94 between edge change 88 is measured, for example, by means of a moving averaging, so that it is recognized in FIG. 4 that the time interval 95 between two edge changes is shorter than the time interval of the directly preceding interval 96 see with the edge change 97 between the two time intervals 95 and 96, the direction of movement of the electric motor has changed, which is represented by the change of the direction of rotation signal 86 from (I) to (r). In addition, the time interval 94, 95, 96 (time intervals) can be compared with a previously determined and stored value at a maximum speed. This can be identified when the electric motor has returned to its normal operating state with its target speed. Furthermore, it can be empirically determined beforehand how many edge changes 88 occur after the changeover point 93 of the reversing process in the normal operating state. With a single change of the current state signal 50, this number can be compared with the current number of edge changes. Let 88 be compared, so as to check the presence of a reversing operation of the electric motor 12.

It should be noted that, with regard to the exemplary embodiments illustrated in the figures and in the description, a variety of possible combinations of the individual features are possible with one another. Thus, for example, the changes in the current state signal 50 can be combined with various evaluation methods of the incremental sensor signal 56, the edge change of which can be counted and their interval lengths compared with one another and / or with stored values. The evaluation method is independent of the determination of the digital current state signal 50, which can also be obtained, for example, by means of a direct motor current measurement or estimation. The evaluation unit 40 may be combined with the control electronics 24 of the electric motor 12 or may be formed as a separate component, preferably on a printed circuit board. In this case, the device 10 for operating the electric motor 12 can be arranged locally directly directly at the electric motor 12 or in a central control unit. The inventive method and the corresponding device 10 are particularly suitable for the realization of a position detection and / or an anti-trap for comfort drives in the motor vehicle, such as windows, sunroof or

Seat adjustment. However, the method of detecting the direction of rotation can also be used for rotary drives, such as blowers or pumps.

Claims

claims

1. A method for detecting the direction of rotation of a drive unit, in particular an adjusting drive (64) in the motor vehicle, with an electric motor (12) which can be reversed by means of switch (20) in its direction of rotation, wherein the speed of the electric motor (12) by means of exactly one incremental sensor - Nals (56) is detected and an evaluation unit (40) is supplied, characterized in that for evaluating the direction of rotation, a digitized motor current state signal (50) is used, the current motor current (30) the states -1, 0, +1 (84 , 80, 82).

2. The method according to claim 1, characterized in that the edge changes (88, 91, 92) of the incremental sensor signal (56) in response to a change of the digitized motor current state signal (50) are associated with a particular direction of rotation, whereby in particular the leakage of the electric motor e (12) is detected by a single change of the current state signal (50) after switching off the electric motor (12).

3. The method according to any one of claims 1 or 2, characterized in that a second change of the current state signal (50) after switching off the electric motor (12) as reverse rotation of the electric motor (12) - for example, under a load - is interpreted.

4. The method according to any one of the preceding claims, characterized in that the duration of the last edge change (97) of the incremental sensor signal (56), as long as the motor current state signal (50) is not equal to zero, until the change of the motor current state signal (50) is measured to zero in order in particular to reliably detect a reverse rotation of the electric motor (12).

5. Method according to one of the preceding claims, characterized in that the transit time between the edge change (97) of the incremental sensor signal (56) - in particular by means of moving averaging - will be measured, and in particular with a stored value for a reversal in direction when reversing the electric motor (12) is compared.

6. The method according to any one of the preceding claims, characterized in that the running time between the edge change (97) of the incremental sensor signal (56) is compared with a previously determined running time at maximum electric motor speed.

7. The method according to any one of the preceding claims, characterized in that by the evaluation of the moving average value of the edge spacings (94, 95, 96) in conjunction with the number of edge changes (97) the direction of rotation change after a reversing operation of the electric motor (12) is recognized.

8. The method according to any one of claims 1 or 2, characterized in that for detecting the motor current signal (51) an amplifier circuit (44) to terminals (32, 34) of the electric motor (12) is connected, which is also when the electric motor (12) provide an evaluable measure of the current flow through the contact resistors (72) of the switches (20).

9. The method according to any one of the preceding claims, characterized in that the measuring range of the output signal (48) is divided into three areas, wherein a mean range (80) or a limit, the motor current state signal (50) equal to zero (0), a upper area (82) the positive one

Motor current condition signal (50) (+1) and a lower portion (84) the negative motor current state signal (50) (-1) is assigned.

10. The method according to any one of the preceding claims, characterized in that for generating the current state signal (50), the amplifier circuit (44) remains in saturation when the motor current (30) - in particular in the normal operating state of the electric motor (12) - a predetermined absolute current value, for example, about + / ~ 0.5 A, exceeds.

11. The method according to any one of the preceding claims, characterized in that for the position detection of the adjusting drive (64), the incremental sensor signal (56) by means of a magnetic signal generator (52) is generated with a magnetic signal sensor (54) - in particular a HaII sensor (55) - cooperates.

12. Device (10) for operating an electric motor (12) by means of switch (20) - for example by means of relays (18) - reversible in its direction of rotation, and exactly one magnetic signal sensor (54) - in particular Hall sensor (55) - arranged is precisely one incremental sensor signal (56) provides the rotational movement, in particular according to one of the preceding claims, characterized in that at the terminals (32, 34) of the electric motor (12) an amplifier circuit (44) is arranged, at least a qualitative measure of the motor current (30) through the contact resistances (72) of the switch contacts (74) detected.

13. Adjustment drive (64), in particular in a motor vehicle, according to one of the preceding claims, characterized in that the position detection is part of a anti-trap function (60) which stops a part to be adjusted (62) and / or reversed when by means of the position detection of Part (62) is detected that an obstacle (66) in the adjustment path (68) is located.