Method and device for operating electric motor

Abstract

The invention relates to a method for operating an electric motor (10) on the basis of rotational speed data, in particular by means of rotational speed control, the rotational speed data being determined on the basis of the detection of discrete position transmitter pulses, the method comprising the following steps:-providing (S1) a rising starting voltage for starting the electric motor (10); detecting (S2) a voltage value of the rising starting voltage when a first position transmitter pulse (P1) occurs in the case of discrete rotor positions of the electric motor (10); -acquiring (S3) a pre-control voltage dependent on a voltage value of the rising starting voltage detected with respect to the first position transmitter pulse (P1); and-operating (S5) the electric motor (10) as a function of a control voltage specified by the operating method, to which the pre-control voltage is applied, in particular in an additive manner or in a multiplicative manner.

Description

Technical Field

[0001] The invention relates to a method for operating an electric motor, for example by means of a control requiring rotational speed data, wherein the rotational speed data are preferably determined by means of detecting discrete position transmitter pulses. Background Art

[0002] In automobile construction, electrical systems for supporting various vehicle functions are of vital importance to the needs and interests of the vehicle occupants. These systems rely heavily on electric drives that must function without friction, without interference and in a reliable manner. Reliable control of these motors, especially under changing load conditions that may occur during normal vehicle operation, is an important aspect of motor vehicle technology.

[0003] The currently known operating modes of electric motors for vehicle applications, such as electric window lifters and sliding roofs, provide for regulation that requires a rotational speed signal, such as, for example, rotational speed regulation. A common problem is that the applied load is not known when switching on. Therefore, in the initial phase, operating methods, such as, for example, regulation that requires rotational speed data, cannot be carried out, since two consecutive position transmitter pulses must be detected in order to obtain the rotational speed data. If the applied load is too high, starting of the motor is prevented.

[0004] Furthermore, control with unknown loads requires a precontrol in order to avoid manipulated variables which, in the case of small control deviations, do not result in an effective torque for the control which can be converted into a movement.

[0005] It is therefore an object of the present invention to provide a method for operating an electric motor which ensures a reliable starting of the electric motor and allows for a correct operation based on predefined manipulated variables. Summary of the invention

[0006] This object is achieved by a method for operating an electric motor as a function of rotational speed data, in particular by means of rotational speed control, according to claim 1 and by a device and a system according to the dependent claims.

[0007] According to a first aspect, a method is provided for operating an electric motor as a function of rotational speed data, in particular by means of rotational speed control, wherein the rotational speed data is determined as a function of detecting discrete position transmitter pulses, wherein the method comprises the following steps:

[0008] -providing a rising starting voltage for starting the electric motor;

[0009] - detecting the voltage value of the rising starting voltage when a first position sensor pulse occurs in the case of a discrete rotor position of the electric motor;

[0010] - obtaining a pre-control voltage which depends on the voltage value of the rising start voltage detected with respect to the first position transmitter pulse; and

[0011] The electric motor is operated as a function of a control voltage which is predefined by the operating method and to which the pilot control voltage is applied, in particular in an additive or multiplicative manner.

[0012] In the case of discrete rotor positions of the electric motor, position transmitter pulses are detected, in particular by one or more of the following position sensors: Hall sensor, optical encoder, resolver, rotary position transmitter, incremental transmitter, magnetic sensor. The method focuses on regulation requiring a rotational speed signal, in particular rotational speed regulation, and controlling the electric motor during the start-up phase.

[0013] First, in the starting phase, that is, when the electric motor is started from a standstill, a starting voltage that increases over time is provided in order to start the electric motor. The starting voltage that increases over time is used to obtain a voltage value from which the electric motor starts reliably. The voltage value required to achieve starting can vary depending on the load.

[0014] The voltage value of the starting voltage that rises over time is detected at the time point when the first position transmitter pulse occurs in the case of a discrete rotor position of the electric motor. This means that the voltage value of the starting voltage that rises over time is detected as soon as the rotor of the electric motor has reached a specific position transmitter position and a position transmitter pulse of the position transmitter is generated there. The detection of the first position transmitter pulse indicates that the electric motor is started or started.

[0015] Furthermore, a precontrol voltage is determined which depends on the detected voltage value of the temporally rising starting voltage when the first position transmitter pulse occurs. Since the precontrol voltage is determined based on the actual operating conditions of the electric motor and takes into account the applied load, this allows for improved operation or improved regulation of the electric motor.

[0016] The obtained pre-control voltage is used to operate the electric motor. The pre-control voltage is used for pre-control during regulation. Depending on the operating method, such as, for example, in controlled operation, the pre-control voltage can also be used to simply apply the control voltage generated by the operating method. The pre-control helps to ensure efficient operation of the electric motor even at low control voltages.

[0017] The described method enables improved and more efficient operation, in particular regulation or control, of an electric motor by detecting a pilot control voltage before starting normal operation, which pilot control voltage ensures starting of the electric motor under given load conditions.

[0018] It may be provided that the electric motor is operated according to a control, wherein a predefined control voltage is provided by the control.

[0019] Furthermore, after the first position sensor pulse, the control voltage can be increased further, in particular in the form of a time-dependent function having a ramp-shaped, step-shaped, piecewise linear or S-shaped profile.

[0020] It may be provided that a second position encoder pulse is detected after the first position encoder pulse, wherein rotational speed data is determined as a function of the detection times of the first and second position encoder pulses, wherein the electric motor is operated as a function of the rotational speed data determined in this way.

[0021] Furthermore, it can be provided that a control system which provides the control voltage is started after the second position transmitter pulse or after the third position transmitter pulse.

[0022] One aspect of the invention relates to a device, in particular a control unit, for operating an electric motor as a function of rotational speed data, in particular by means of rotational speed regulation. The device is designed to:

[0023] - providing a time-increasing starting voltage for starting the electric motor;

[0024] - detecting the voltage value of the starting voltage which rises over time when a first position sensor pulse occurs at a discrete rotor position of the electric motor;

[0025] - obtaining a pre-control voltage which depends on the adjustment voltage detected with respect to the first position transmitter pulse; and

[0026] The electric motor is operated as a function of a predefined control voltage, to which a pilot control voltage is applied.

[0027] A position transmitter for detecting position transmitter pulses can be provided. The position transmitter for generating discrete position transmitter pulses at a predetermined rotor position of the electric motor can be a sensor which monitors the rotation of the electric motor and generates signals / pulses referred to as position transmitter pulses at specific rotor positions (rotation angles). These signals convey information including the time of the respective position transmitter pulses and the rotor position associated therewith, from which the rotational speed / rotational frequency of the electric motor can be determined.

[0028] The device can be used to generate a time-increasing starting voltage for starting an electric motor. The starting voltage is required in order to bring the motor out of a standstill and start rotating. As soon as the start of rotation is detected based on a first position transmitter pulse, the voltage value of the starting voltage can be stored. The occurrence of such a first position transmitter pulse indicates that the electric motor has been successfully started and is rotating.

[0029] In the control unit, a precontrol voltage can be determined which depends on the detected voltage value of the starting voltage which rises over time or can correspond thereto. The precontrol voltage can enable precontrol of the electric motor in the case of regulated operation. By adapting the precontrol voltage based on the detected voltage value of the starting voltage which rises over time, efficient control of the electric motor can be achieved, since a voltage threshold value can be taken into account, below which a prescribed control of the electric motor is not possible. The precontrol voltage is thus adapted to the specific requirements of the electric motor and the current operating conditions of the electric motor, whereby a stable and efficient operation of the electric motor can be achieved, in particular by regulation.

[0030] Finally, the regulator provides a precontrol which is based on the detected precontrol voltage. This precontrol makes it possible to efficiently regulate the electric motor in such a way that possible load fluctuations or other operating disturbances are compensated in good time in order to ensure stable operation of the electric motor.

[0031] One aspect of the invention relates to a computer-readable storage medium for persistently storing computer program instructions executable by a processor, wherein the computer program instructions implement the steps of one of the preceding method claims.

[0032] Features, effects and advantages associated with the described aspects of the invention are described below.

[0033] Discrete position transmitter pulses can be generated using multiple sensors, such as Hall sensors, optical encoders or magnetic sensors, which detect the rotor position or the movement of the motor shaft. These sensors are usually arranged at a specific rotor position of the rotor or motor shaft, and each time the rotor reaches a specific angular position, an electrical pulse is generated. The pulse sequence generated thereby provides information about the rotational speed of the electric motor. The faster the rotational speed, the more position transmitter pulses are generated in a specific time period, or the shorter the time interval between two position transmitter pulses that follow one another. The rotational speed of the electric motor can be determined in a manner known per se from the time between two position transmitter pulses. It has been found to be advantageous that the sensors are designed equidistantly in a manner that is an angular distance of 90° divided by the number of pole pairs of the position transmitter.

[0034] The electric motor can be started in a controlled manner by providing a starting voltage when the motor starts and detecting the voltage value during the first position sensor pulse. The pilot voltage is then taken from the detected value and the control / regulation behavior is thus adapted to the respectively applied motor load.

[0035] According to one embodiment, the starting voltage can be further increased after the first position transmitter pulse. A higher value for the pre-controlled voltage means in this respect that this value is greater in magnitude than the detected voltage value. By further increasing the starting voltage, a load-induced stop after the first position transmitter pulse and before the second position transmitter pulse occurs is avoided and continuous operation is ensured. This procedure improves the robustness of the control and avoids a stop of the electric motor after the first position transmitter pulse, which occurs, for example, due to friction effects.

[0036] The increased motor load can be caused by increased friction between the parts to be moved by the electric motor, for example due to the ingress of dust or dirt between the parts to be moved. In such cases, the described approach enables reliable starting of the electric motor, identification of the starting conditions and thus adaptation of the precontrol.

[0037] The detected pilot control voltage is used for the regulation in order to avoid that a too low control voltage cannot cause a control intervention because the adhesion / friction forces cannot be overcome. By applying the pilot control voltage, delayed starting is avoided even in the case of a small control voltage.

[0038] The starting voltage can have the form of a time-dependent monotonically increasing function with a ramp-like profile, wherein the function is preferably constant at the beginning and end of the time range and extends linearly increasing in the intermediate time range. When the electric motor is set in motion, it must overcome the inertia of its load, and a voltage that is too low or too high can cause the electric motor to stall. The ramp-like profile of the starting voltage allows a gradual increase in torque, which advantageously helps to prevent the electric motor from stalling, in particular in the case of high loads that can be caused by increased friction between the components to be moved by the electric motor.

[0039] According to one specific embodiment, if the rotational speed is known, regulation of the electric motor can begin after the second position transmitter pulse or the third position transmitter pulse. Before the first position transmitter pulse is detected, the operation can be controlled purely by the rising start voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The invention is explained in more detail below with the aid of an embodiment and with reference to the accompanying drawing, in which:

[0041] Figure 1 A block diagram of a device for regulating the rotational speed of an electric motor according to the invention is shown;

[0042] Figure 2 A schematic flow chart of a method for regulating the rotational speed of an electric motor according to the present invention is shown; and

[0043] Figure 3 a - 3c show diagrams for illustrating the time curve of the starting voltage or the regulating voltage under different loads on the electric motor. DETAILED DESCRIPTION

[0044] Figure 1 A device 20 according to the invention is shown for operating an electric motor 10. The device 20 comprises:

[0045] a position transmitter 22 which is designed to generate discrete position transmitter pulses in the case of discrete rotor positions of the electric motor 10 ;

[0046] a control device 24 which is designed to provide a voltage for operating the electric motor 10 ; and

[0047] A control unit 26 which is coupled to the position transmitter 22 and the adjusting device 24 and is designed to detect a pilot control voltage and to operate the electric motor 10 as a function of the pilot control voltage.

[0048] The position transmitter 22 can be designed as a Hall sensor, an optical encoder, a resolver, a rotary position transmitter, an incremental transmitter, a magnetic sensor. When the rotor of the electric motor reaches a specific rotor position, the position transmitter 22 provides a position transmitter pulse. Depending on the embodiment, the spacing between the positions of the position transmitter at which the position transmitter pulses are generated is different.

[0049] Adjustment device 24 may be designed in the form of a power circuit in order to apply a voltage to the electric motor under the control of control unit 22. The power circuit may include power semiconductor components and may be driven by the control unit, for example, by means of pulse width modulation in order to apply a specific voltage to electric motor 10.

[0050] Control unit 26 preferably includes a microcontroller which executes a control algorithm, using which the electric motor is operated in a starting phase in order to determine a pilot control voltage and to provide first rotational speed data for further operation of electric motor 10 in a normal operating phase.

[0051] The functions implemented by the control unit 26 include:

[0052] - providing a rising starting voltage for application to the electric motor 10;

[0053] -Detect position transmitter pulses;

[0054] - storing the voltage value of the starting voltage at the electric motor 10 when a first position sensor pulse occurs,

[0055] - obtaining a pre-control voltage which depends on the voltage value of the adjustment voltage detected with respect to the first position transmitter pulse,

[0056] - obtaining the rotational speed after receiving the second position transmitter signal, and

[0057] - Operate the electric motor based on pre-controlled voltage and speed.

[0058] Figure 2 A flow chart of the method according to the invention for speed-dependent regulation of the speed of electric motor 10 is shown, the speed being determined as a function of the detection of discrete position encoder pulses.

[0059] The method comprises the steps of:

[0060] In step S1 , a variable, temporally increasing starting voltage is provided for starting the electric motor 10 . The starting voltage starts with a temporally constant voltage level and increases monotonically after an initial period of time;

[0061] - in step S2 , storing the voltage value of the starting voltage when a first position transmitter pulse occurs at a discrete rotor position of the electric motor 10 ;

[0062] - In step S3, obtaining a pre-control voltage according to the stored voltage value;

[0063] After receiving the second position transmitter pulse, determining the rotational speed of the electric motor 10 in step S4 ; and

[0064] In step S5 , a pilot control based on a pilot control voltage is provided for operating the electric motor in a speed-dependent manner during regulation.

[0065] Furthermore, after the first position sensor pulse, the starting voltage can be increased further in order to enable reliable further operation of the rotor.

[0066] After the second position transmitter pulse, a third position transmitter pulse can also be waited for before activating the control with the pilot control, so that in addition to the rotational speed, an acceleration is obtained, which is obtained from the rotational speed due to the duration between the first position transmitter pulse and the second position transmitter pulse and the rotational speed due to the duration between the second position transmitter pulse and the third position transmitter pulse. The acceleration can be used for the control of the electric motor, in particular when the control has a D component and is designed as a PD or PID control.

[0067] exist Figure 3 a-3c shows the time curves of the starting voltage and the regulation voltage for different loads.

[0068] Figure 3 a shows the course of the voltage U at the electric motor under low load. The course of the starting voltage is initially constant and causes the start of the electric motor 10 due to the low load. After the first position transmitter pulse P1, the starting voltage increases in a ramp-like manner by a predetermined amount during the duration Z1 and then remains constant. In the subsequent phase of constant voltage, the second and third position transmitter pulses P2, P3 are detected in order to then determine the rotational speed and acceleration for the control of the electric motor 10 that is started with the detection of the third position transmitter pulse P3.

[0069] Figure 3 b shows the course of the voltage U at the electric motor under medium load. The course of the starting voltage is initially constant and does not yet cause the electric motor 10 to start due to the medium load. The electric motor 10 is started with a ramp-like increase in the starting voltage. After the first position transmitter pulse P1, the starting voltage is further increased in a ramp-like manner by a predetermined amount during the duration Z1 and then remains constant. In the subsequent phase of constant voltage, the second and third position transmitter pulses P2, P3 are detected in order to then determine the rotational speed and acceleration for the control of the electric motor 10 that is started with the detection of the third position transmitter pulse P3.

[0070] Figure 3 c shows the course of the voltage U at the electric motor under high load. The course of the starting voltage is initially constant and does not yet cause the electric motor 10 to start due to the high load. The electric motor is started with a ramp-like increase in the starting voltage. After the first position transmitter pulse P1, the starting voltage increases in a ramp-like manner by a predetermined amount during the duration Z1 and then remains constant. In the subsequent phase of constant voltage, the second and third position transmitter pulses are detected in order to then determine the rotational speed and acceleration for the control of the electric motor 10 that is started with the detection of the third position transmitter pulse.

[0071] By providing a starting voltage that rises over time when the motor starts and detecting the voltage value of the starting voltage during the first position sensor pulse, the electric motor 10 can be started in a controlled manner on the one hand, and a suitable pre-control voltage can be obtained on the other hand so that the subsequent operation can be adapted to the corresponding motor load.

Claims

1. A method for operating an electric motor (10) as a function of rotational speed data, in particular by means of rotational speed control, wherein: The rotation speed data is determined by relying on the detection of discrete position transmitter pulses, wherein the method comprises the following steps: - providing (S1) a rising starting voltage for starting the electric motor (10); - acquiring (S2) the voltage value of the rising starting voltage when a first position transmitter pulse (P1) occurs in the case of a discrete rotor position of the electric motor (10); - acquiring (S3) a pre-control voltage which depends on the voltage value of the rising start voltage detected with respect to said first position transmitter pulse (P1); and - operating (S5) the electric motor (10) as a function of a control voltage which is predetermined by an operating method and to which the pilot control voltage is applied, in particular in an additive or multiplicative manner.

2. The method according to claim 1, wherein: The electric motor (10) is operated according to a control system, wherein the predefined control voltage is provided by the control system.

3. The method according to claim 1 or 2, wherein: After the first position sensor pulse (P1), the control voltage is further increased, in particular in the form of a time-dependent function having a ramp-shaped, step-shaped, piecewise linear or S-shaped profile.

4. The method according to any one of claims 1 to 3, wherein: A second position transmitter pulse (P2) is detected, wherein the rotational speed data is determined as a function of the detection time of the first position transmitter pulse and the second position transmitter pulse (P1, P2), wherein the electric motor (10) is operated as a function of the rotational speed data determined in this way.

5. The method according to any one of claims 1 to 4, wherein: After the second position transmitter pulse (P2) or after the third position transmitter pulse (P3), a control is started which provides the adjustment voltage.

6. The method according to any one of claims 1 to 5, wherein: The discrete position transmitter pulses (P1, P2, P3) are provided by one or more of the following sensors: Hall sensor, optical encoder, resolver, rotary position transmitter, incremental transmitter, magnetic sensor.

7. The method according to any one of claims 1 to 6, wherein: The electric motor (10) is operated with regulation, in particular speed regulation, position regulation or torque regulation.

8. A device (20) for operating an electric motor (10) using rotational speed data, in particular by means of rotational speed control, comprising: a position transmitter (22) which is designed to generate discrete position transmitter pulses in response to discrete rotor positions of the electric motor (10); - a control device (24) which is designed to provide a voltage (U) for operating the electric motor (10); and a control unit (26) which is coupled to the position transmitter (22) and the adjusting device (24) and is designed to: - providing a rising starting voltage to be applied to the electric motor (10) via the adjustment mechanism (24); - storing the voltage value of the rising starting voltage which is applied to the electric motor (10) when a first position transmitter pulse (P1) occurs in the case of a discrete rotor position, - obtaining a pre-control voltage which depends on the voltage value of the rising start voltage detected with respect to the first position transmitter pulse (P1), and - operating the electric motor (10) by means of the regulating device (24) as a function of a predefined regulating voltage which is generated as a function of the pilot control voltage.

9. A computer program product comprising commands which, when the program is executed by at least one data processing device, cause the data processing device to carry out the steps of the method according to any one of claims 1 to 7 by actuating the adjustment device (24). 10 . A machine-readable storage medium comprising commands which, when executed by at least one data processing device, cause the data processing device to execute the steps of the method according to claim 1 .

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