WO2005071812A1

WO2005071812A1 - Method for evaluating information on the rotational speed and rotational position of a dc-motor

Info

Publication number: WO2005071812A1
Application number: PCT/EP2005/050227
Authority: WO
Inventors: Thomas Lux; Holger Pruessel; Thomas Fischer; Stephan Binhack; Ralf-Peter Bergmann; Axel Schwarz
Original assignee: Robert Bosch Gmbh
Priority date: 2004-01-27
Filing date: 2005-01-20
Publication date: 2005-08-04
Also published as: DE102004004198A1

Abstract

The invention relates to a method for opening and closing an opening by means of a motor driven displaceable part, arranged in particular on a vehicle, with the aid of an electric drive (1), a control unit (4, 7) and a command device. An obstruction is detected during opening and/or closing of the displaceable part, said obstruction being arranged in the displacement path of the displaceable part and a signal is forwarded to the control unit (4, 7), in order to stop or reverse displacement of the displaceable part. The invention is characterised in that after a variable representing the controlling power of the electric drive (1) is measured, it is subjected to an inner FFT step (8) of a fast Fourier transformation with a supply voltage U0 supplied by a voltage source (22). The result thereof is evaluated in an evaluation logical system (11) and from there the closing force of the electric drive (1) is determined in a closing force defining step (13).

Description

Procedure for the evaluation of speed and turning position information of a DC motor

Technical field

Electric drives are increasingly being used in automotive engineering today, for example to move vehicle seats, window panes or sunroofs, whether closed sunroofs or glass sunroofs. DC motors are used to drive such movable vehicle components, the speed and load condition of which must be recorded in order to be able to control the electric drive in a suitable manner. It is necessary, for example, to record different load states of the electric servomotors which can be embodied as direct current motors in order to protect the drives and the users, if necessary, by switching off the motor. Such load states are in fault-free operation, for example, reaching end positions of the drive and, in the case of faulty operation, increased friction due to wear or environmental influences or an obstacle introduced into the drive, such as a user's limbs. Such load conditions must be recognized reliably to protect both the user and the electric drive.

State of the art

From DE 195 14257 Cl a monitoring method of an adjustment system is known which also guarantees a restraint protection function in the start-up phase of the electric drive. The speed or speed is detected by means of a sensor in the form of a Hall sensor, a period value is stored and compared with a predetermined limit value. Since the engine period changes greatly in the start-up phase, it only becomes steady after about three engine periods, ie, the engine runs smoothly, so that a satisfactory level of security against excessive power delivery is only then guaranteed. Therefore, the initial period limit during the motor start-up phase is changed from the due to the stored reference values previous actuation of the engine. The initial period limit value (PGW) * is preferably based on the last period value (PWvn) of the previous adjustment according to the formula:

PGW ^* = 2 • PWvn • (0.5 + E ^" )

certainly. This process is quite complex and complex and depends on the previous adjustment process. A prerequisite for such a method is that the measured values (period values) can be saved continuously and made available for the next engine start. In addition, this method is limited to the use of the speed or the speed as a sensor signal for the emission protection function.

DE 199 08 658 AI relates to a locking device for moving a locking body, such as a window pane or a roof panel in a motor vehicle. A sensor detects a closing force acting on the closing body, which is monitored by a control circuit and this closing device is reversed when a limit value of the force is exceeded. An evaluation unit integrated in the control circuit varies the limit value depending on a force measured at an earlier point in time. This locking device implements reliable, sensitive pinch protection for a stationary operating state of the drive motor, but it does not enable pinching protection in the start-up phase of the motor, since in this area the measured shear force cannot yet be reliably compared with previous measured values. However, compliance with the clamping force limit when the electric drive starts is increasingly required.

A method for opening and closing an opening has become known from DE 102 24 050 AI. An adjusting motor, a control unit and an operating device are provided, an obstacle which is located in the adjusting path of the moving part being detected when the moving part is closed. A signal is passed on to the control unit in order to stop or reverse the movement of the movable part, wherein when the operating device is actuated to close the opening, the movable part is first moved against the closing direction and then the moving part in the closing direction.

The detection of an operating status or a change in an operating status in a system in which at least one analog signal indicating the operating status is present, can be carried out as shown below: The analog signal or a signal dependent thereon is sampled and a sampling signal is generated from it. From a number of signal values of the sampled signal, a transformation signal representing a spectral distribution is generated, which is subsequently compared with a least a reference signal representing a spectral distribution. The reference signal was generated from an analog reference signal representing an operating state to be detected. The reference signal can be a transfoimation signal generated on the basis of previous samples. The transformation signal representing a spectral distribution and the reference signal can be discrete Fourier transformed (FFT) signals.

A device for detecting the operating state or for detecting the changes in the operating state of a system in which at least one analog signal indicating the operating state is present comprises a sampling device for sampling the analog signal and for providing the sampling signal. Furthermore, a transformation unit is provided to which the scanning signal is fed and which generates a transformation signal from a number N of scanning values of the scanning signal. The device further comprises a comparator arrangement to which the transformation signal is fed and which compares the transformed signal with at least one reference transformation signal representing a spectral distribution and the comparator arrangement provides a status signal]

The following procedures are currently being used on adjusting drives used in the automotive sector to record the position and dynamics of the actuator: Hall sensors (HIC) are used, which are located on the drives, for example in the area of the motor axis or on the output , a magnet or a magnetic ring. One or more Hall sensors positioned close to the magnet or magnetic ring react to the generated field and thus provide information about the position, direction of rotation and speed of rotation of the electric drive. Furthermore, rotary encoders are used which are arranged on the motor axis or an output component and which return the relative or absolute position of the electric drive. In electrical drives with brushes, a current ripple is generated by the electrical commutation, which can be detected via a measuring resistor. The evaluation of the current ripple allows conclusions to be drawn about the relative angle of rotation.

In addition, there is the possibility of identifying the grooves of an electric drive via the respective current consumption. If a groove passes a brush of the electric drive, an increased short-circuit is detected by an internal short circuit, which can be evaluated by suitable measures.

Presentation of the invention

According to the invention, a method for speed detection in DC motors (DC motors) is proposed, which enables an evaluation of the current consumption of the electric drive. The fact that current changes are generated by a groove passing a brush of the electric drive is used for this purpose. The current ripple generated is evaluated in the time domain. A discrete signal, which indicates the occurrence of a groove, is generated in a circuit or by an algorithm by means of discrete or arithmetic filters. However, the current fluctuations are relatively weak, so that they can be transformed into the frequency range using a transformation, such as a Fast Fourier Transformation (FFT). The periodically recurring current fluctuations due to the passage of the grooves along the brushes can be shown in the form of a spectral line. The position of this spectral line on the frequency axis is directly related to the speed of the electric drive. This evaluation method enables the average speed to be obtained from the last periods of the signal.

The evaluation of a frequency spectrum of the motor voltage contained via an FFT transformation offers several simplifications compared to the use of known methods, such as, for example, detection by Hall sensors or rotary encoders or evaluation of a ripple count, and the resulting cost advantages. No sensor technology is required, which must be assigned relative to the electric motor or an output component assigned to it. This results in significant simplifications in terms of construction. Since the evaluation electronics do not necessarily have to be in the immediate vicinity of the drive, both central and decentralized design options are available. The subsequent expansion of standard motors is also possible.

The supply and induced motor voltage can be superimposed. This overlay is read back and evaluated using a Fast Fourier Transformation (FFT). The speed and direction of rotation of the DC motor can be deduced from the characteristic frequencies. The electric drive is usually controlled by mechanical switches, such as relays or semiconductor switches (field effect transistors). It is controlled by a control logic, which uses the information obtained from the FFT for different requirements. stanchions used. In this way, the absolute position of an actuator on the engine output can be determined. Furthermore, fluctuations in speed can be compensated for and a pinch protection can be implemented.

drawing

The invention is explained in more detail below with the aid of the drawing:

It shows:

Figure 1 is a block diagram of an evaluation circuit for rotational position and speed detection of an electric drive and

Figure 2 is a representation of the relays' or FFT's with which the electric drive can be controlled.

variants

FIG. 1 shows a block circuit diagram which shows the components of an evaluation circuit for evaluating the speed or the rotational position of an electric drive, such as a direct current motor (DC motor).

The block diagram shown in FIG. 1 shows an electric drive 1 from which two brushes 2, 3 positioned opposite one another in this case can be seen. The electric drive 1 is controlled via a power unit 4. The power section 4 in turn is controlled via a control logic 7. The voltage U_, U ₂ , which prevail in the lines 5, 6 running from the power section 4 to the motor brushes 2, 3, are tapped and fed to an FFT stage 8 on the input side. The detected voltages Ui, U ₂ in the lines 5, 6 to the motor brushes 2, 3 are converted in the FFT stage 8 into a first frequency spectrum and a second frequency spectrum. At the output 10 of the FFT stage 8, the first and second frequency spectra obtained are fed to an evaluation logic 11. The input side of the FFT stage 8 is designated by reference number 9.

The evaluation logic 11 is followed by a closing force limiting stage 13 and a component 154 for detecting a position of the electric drive 1. The closing force limiting stage 13 becomes a dn / dt signal, ie. a speed change signal 12 supplied, while the component 15 (position detection stage) a direction of rotation signal 14 is supplied

The closing force calculated in the shear force limitation stage 13 or the position of the electric drive 1 calculated in the position detection stage 15 is input to the control logic 7 for the power unit 4, i.e. At the input side 16 of the control logic 7 there is a ScMießkraftbegrenzung stage signal 17 and a position signal 18, which represents the current rotational position of the electric drive 1. On the basis of these operating parameters of the electric drive 1 known to the control logic 7, the power section 4 controlling the electric drive 1 is controlled, by means of which the voltages prevailing in the first line 5 and in the second line 6 can be influenced

The closing force limiting signal 17 (SKB signal) obtained in the shear force limiting stage 13 is applied to the input side 16 of the control logic 7. The control logic 7 transmits this signal to the power unit 4, so that the maximum permissible closing force is known there as the operating parameter of the electric drive 1. The dynamic information of the electric drive 1 is evaluated by an algorithm implemented in the leveling force limitation stage 13.

From the input parameter dn / dt and the position, a tripping force limitation parameter dn / ds is formed. In the implemented algorithm, additional feeding functions can be taken into account, taking into account a rough road distance, taking into account hard blows on pane surfaces and signs of aging in order to influence the triggering parameter dn / ds for the limitation of the force of the force.

The closing force limitation can then be adapted adaptively so that signs of aging can be taken into account and a closing force that takes into account better environmental conditions and aging parameters that are required to trigger a shutdown of the electric drive 1 via the power unit 4 are available there in every operating position.

From the view in Figure 2 shows that in the lines 5, 6, the voltage applied to the motor brushes 2, 3 of the electric drive 1, is tapped The voltages Ui, U ₂ are a voltage measurement maximum level 19 supplied. The induced supply voltage and the induced motor voltage are read back and evaluated in an FFT stage 8. The evaluation result is fed to the evaluation logic 11, which switches 20 and 21, which act either as relays or as field effect transistors. ren trained can be abandoned. Switches 20 and 21 are on the one hand connected to supply voltage source 22 and on the other hand to ground 23.

Initially, the triggering parameter for the limitation of the tensile force is determined within the evaluation logic 11. Position-dependent disturbance variables are filtered with the aid of an adaptive measured value adaptation, further filtering can be carried out using an additional filter to take into account a poor road distance; this allows the respective driving situation of the vehicle to be taken into account. The limit value formation within the evaluation logic is determined as a function of the battery voltage Ubat and the kinetic energy of the electric drive 1. Thus, its dynamic behavior is also taken into account.

In the proposed method according to the invention, both the path and the time can be specified in such a way that the electric drive 1 has reached its stationary operating state in the direction of compression. Regardless of the measurement parameter used (amount and ripple of the motor current, speed n, frequency or torque), this ensures that the anti-trap function is guaranteed from the start position of the closing process, regardless of the evaluation method used. If the electric grinder 1 is controlled by means of pulse width modulation, it can first be driven with low power in the direction of compression and later, in a subsequent operating phase, with maximum power in the direction of compression.

Pinching situations can also occur which do not occur when opening or closing an opening, but also when adjusting a part relative to another part or person, e.g. b. with seat control in the vehicle.

Both the front passengers when adjusting the seats or seat parts against the steering wheel or the roof of the vehicle, as well as the rear passengers between the rear seat and the front seat part moved backwards can be pinched.

The electric drive 1 is controlled by means of a control logic 7. If an encroachment is detected when an absolute or relative limit value is exceeded or undershot, the control logic 7 sends a signal to the electric drive 1. Since the measured values change very strongly in the motor start-up phase, there is no reliable clamping force limitation in this operating phase According to the proposed method, however, the moving part has already reached the stationary operating state at the starting point of the closing process, so that a comparison of the measured values with an absolute or relative limit value of the anti-interference function is already possible. The opening to be sealed can be divided into different opening areas, so that an anti-trap area can be defined. If the moving part is outside this area when a closing process is started, the electric drive is actuated immediately in the closing direction.

It is also conceivable to first control the electric drive 1 such that it moves in the opening direction for a predeterminable period of time before the movement of the part closing the opening is reversed. Only after this period has elapsed is the moving part driven to close the opening in the direction of compression, in this way an object that has already been jammed can be released when the motor starts and the legal requirements can be easily met.

BezugszeichenHste

electric drive first motor brush second motor brush

Power section first supply line second supply line

Control logic for the power section

FFT stage

input side

Output side (frequency spectra)

Evaluation logic dn / dt signal

SchHeßkraftbegrenzungs stage

Direction signal

Position detection stage

Control logic input page

Closing force limit signal (SKB signal)

position signal

Voltage measurement level first switch second switch

Supply voltage source

Dimensions

Claims

claims

1. A method for opening and closing an opening by means of a motor-driven movable part, in particular arranged on a vehicle, with an electric drive (1), a control unit (4, 7) and an operating device, the opening and / or closing of the moving part, an obstacle is detected, which is located in the path of the moving part and a signal is passed on to the control unit (4, 7) in order to stop or reverse the movement of the moving part, characterized in that after a measurement a The variable representing the actuating force of the electric drive (1) is subjected to a Fast Fourier transformation within an FFT stage (8) with a supply voltage U ₀ supplied by a voltage queue (22), the result of which is evaluated and evaluated in an evaluation logic (11) which is determined in a limit setting (13) for the electrical drive (1)

2. The method according to claim 1, characterized in that the evaluation of the result of the FFT stage (8) in an evaluation logic (11) with respect to the direction of rotation, the position and dynamic information of the electric drive (1) is carried out.

3. The method according to claim 2, characterized in that the rotational position of the electric drive (1) winL by incrementing or decrementing the motor revolutions from a defined zero position of the electric drive (1)

4. The method according to claim 1, characterized in that in the SchHeßkraftbegrenzungsstufe (13) the determined, representing the actuating force of the electric drive is compared with a limit value.

5. The method according to claim 4, characterized in that when the value of the actuating force of the electric drive (1) representing the size of the limit value of the electric drive (1) is reversed.

6. The method according to claim 4, characterized in that when the size of the electric drive (1) representing the actuating force falls below the limit value, the electric drive (1) is stopped.

7. Procedure according to claim 1, characterized in that the variable representing the actuating force of the electric drive (1) is immobilized within the closing force limitation stage (13) and compared with a limit value.

8. Procedure according to claim 7, characterized in that the variable representing the actuating force is the change in speed dn / dt of the electric drive (1).

9. Procedure according to claim 8, characterized in that a triggering parameter dn / ds is formed from the quantity dn / dt representing the actuating force in the limiting force stage (13).

10. The method according to claim 9, characterized in that the triggering parameter dn / ds in the closing force limitation stage (13) is determined taking into account external influences such as a rough road or the mechanical load on the moving part.

11. The method according to claim 9, characterized in that the triggering parameter dn / ds in the closing force limitation stage (13) is determined taking into account signs of aging.

12. Procedure according to claim 1, characterized in that voltages Ui, U ₂ in leads (5, 6) to the electric drive (1) are measured by means of a voltage measuring stage (19) in which the voltage of a voltage supply queue (22) and the induced voltage Motor voltage are superimposed.

13. The method according to claim 12, characterized in that the superimposed supply voltage Uo and the induced motor voltages Ui, U ₂ are read back and evaluated by means of a Fast Fourier Transformation in the FFT stage (8).

14. Procedure according to claim 1, characterized in that the electric drive (1) is controlled by mechanical switches (20) or semiconductor switches (21) designed as relays.

15. The method according to claim 1, characterized in that the variable representing the actuating force is a variable inverse to the displacing force of the movable part.

16. The method according to claim 1, characterized in that the variable representing the actuating force of the electric drive (1) is its speed n.

17. Process according to claim 1, characterized in that the variable representing the actuating force of the electric drive (1) is a variable proportional to the actuating force of the movable part, in particular the motor current of the electric drive (1).

18. Device for opening and closing an opening by means of a motor-driven moving part - in particular arranged on a vehicle - with an electric drive (1), a control unit (4, 7) and an operating device, with opening and / or When the moving part is closed, an obstacle is detected which is in the adjustment path of the moving part and a signal is forwarded to the control unit (4, 7) in order to stop or reverse the movement of the moving part, in particular according to one of claims 1 to 17, characterized in that an FFT stage (8), which measures the measured actuating force of the electric drive (1), subjects an FFT transformation with a supply voltage U ₀ , which is determined by a voltage source (22), and an evaluation logic (11) and a Determine the closing force limit stage (13) the shear force of the electric drive (1).