Method and apparatus for operating an electric motor

Abstract

The invention relates to a method for operating an electric motor (10) depending on a speed specification, in particular by means of a speed control, wherein the speed specification is determined depending on the detection of discrete position encoder pulses, wherein the method comprises the following steps: - Providing (S1) a rising starting voltage to start the electric motor (10); - Detection (S2) of a voltage value of the increasing starting voltage when a first position encoder pulse (P1) occurs at a discrete rotor position of the electric motor (10); - Determine (S3) a pre-control voltage dependent on the voltage value of the rising start voltage detected for the first position encoder pulse (P1); and - Operation (S5) of the electric motor (10) depending on a control voltage specified by an operating procedure, which is supplied with the pilot voltage, in particular additively or multiplicatively.

Description

Field of the invention

[0001] The invention relates to a method for operating an electric motor, e.g., by means of a control system that requires a speed indication, wherein the speed indication is preferably determined by detecting discrete position sensor pulses. Technical background

[0002] In automotive engineering, electrical systems are crucial for supporting various vehicle functions to meet the needs and requirements of vehicle occupants. These systems rely heavily on electric drives, which must operate smoothly, trouble-free, and reliably. Reliable control of these motors, especially under the changing load conditions that can occur during normal vehicle operation, is an important aspect of automotive engineering.

[0003] Currently known operating modes for electric motors in vehicle applications, such as power windows and sunroofs, provide for control systems that require a speed signal, such as speed control. A common problem is that the applied load is unknown during startup. An operating procedure, such as control, that requires a speed input cannot therefore be executed in the initial phase, because determining the speed input requires the detection of two consecutive position sensor pulses. If the applied load is too high, the motor will not start.

[0004] Furthermore, a control system with an unknown load requires a feedforward control in order to avoid manipulated variables in the case of small control deviations that do not produce an effective torque that can be converted into a movement for the control system.

[0005] It is therefore an object of the present invention to provide a method for operating an electric motor which ensures reliable start-up of the electric motor and enables proper operation based on a predetermined manipulated variable. Disclosure of the invention

[0006] This object is achieved by the method for operating an electric motor depending on a speed specification, in particular by means of a speed control, according to claim 1 and by the device and the system according to the independent claims.

[0007] According to a first aspect, a method is provided for operating an electric motor depending on a speed indication, in particular with the aid of a speed control, wherein the speed indication is determined depending on the detection of discrete position sensor pulses, the method comprising the following steps: - Providing an increasing starting voltage to start the electric motor; - detecting a voltage value of the rising starting voltage when a first position sensor pulse occurs at a discrete rotor position of the electric motor; - Determining a pilot voltage dependent on the voltage value of the rising starting voltage detected at the first position sensor pulse; and - Operating the electric motor depending on a control voltage specified by an operating method, to which the pilot control voltage is applied, in particular additively or multiplicatively.

[0008] The position sensor pulses are detected at discrete rotor positions of the electric motor, in particular by one or more of the following position sensors: Hall sensor, optical encoder, resolver, rotary encoder, incremental encoder, magnetic sensor. The method is directed to a control system that requires a speed signal, in particular speed control and the control of the electric motor during a starting phase.

[0009] First, during the start-up phase—that is, when the electric motor starts operating from a standstill—a gradually increasing starting voltage is applied to start the electric motor. This gradually increasing starting voltage serves to determine a voltage value at which the electric motor will start reliably. The voltage value required to achieve start-up can vary depending on the load.

[0010] The voltage value of the time-rising starting voltage is recorded at the time of the first position sensor pulse occurring at a discrete rotor position of the electric motor. This means that the voltage value of the time-rising starting voltage is recorded as soon as the rotor of the electric motor has reached a specific position sensor position and thereby generates a position sensor pulse from a position sensor. The detection of the first position sensor pulse indicates that the electric motor has started or started running.

[0011] Furthermore, a pre-control voltage is determined, which depends on the detected voltage value of the time-increasing starting voltage when the first position sensor pulse occurs. This enables improved operation or control of the electric motor, since the pre-control voltage is determined based on the actual operating conditions of the electric motor and takes the applied load into account.

[0012] The determined pilot voltage is used to operate the electric motor. The pilot voltage serves as a pilot control in closed-loop control. Depending on the operating method, such as in open-loop controlled operation, the pilot voltage can also be used to simply apply a control voltage resulting from the operating method. The pilot control helps ensure efficient operation of the electric motor even at low control voltages.

[0013] The described method enables improved and more efficient operation, in particular of a closed-loop or closed-loop control, of an electric motor by determining a pilot control voltage before starting regular operation, which ensures that the electric motor starts up under given load conditions.

[0014] It can be provided that the electric motor is operated according to a control system, whereby the specified control voltage is provided by the control system

[0015] Furthermore, the control voltage can be further increased after the first position sensor pulse, in particular in the form of a time-dependent function with a ramp-shaped, step-shaped, piecewise linear or sigmoidal curve.

[0016] It can be provided that after the first position sensor pulse, a second position sensor pulse is detected, wherein the speed indication is determined depending on the detection times of the first and the second position sensor pulse, wherein the electric motor is operated depending on the speed indication thus determined.

[0017] Furthermore, it can be provided that after the second position sensor pulse or after a third position sensor pulse, a control is started which provides the control voltage.

[0018] One aspect of the invention relates to a device, in particular a control unit, for operating an electric motor depending on a speed specification, in particular with the aid of a speed control. The device is designed to - Providing a time-increasing starting voltage to start the electric motor; - detecting a voltage value of the time-increasing starting voltage when a first position sensor pulse occurs at a discrete rotor position of the electric motor; - Determining a pilot voltage dependent on the control voltage detected at the first position sensor pulse; and - Operation of the electric motor depending on a specified control voltage, which is supplied with the pilot control voltage.

[0019] A position sensor can be provided to detect the position sensor pulses. The position sensor, which generates discrete position sensor pulses at specified rotor positions of the electric motor, can be a sensor that monitors the rotation of the electric motor and generates signals / pulses known as position sensor pulses at certain rotor positions (rotation angles). These signals transmit information, including the time of the respective position sensor pulse and the corresponding rotor positions, which can be used to determine the speed / rotational frequency of the electric motor.

[0020] The device can be used to generate the time-increasing starting voltage needed to start the electric motor. The starting voltage is required to bring the motor from a resting state and initiate rotation. Once the start of rotation has been detected by the first position sensor pulse, the starting voltage value can be stored. The occurrence of this first position sensor pulse indicates that the electric motor has been successfully started and is rotating.

[0021] The control unit can determine the pilot voltage, which is dependent on the detected voltage value of the time-rising starting voltage or can correspond to it. The pilot voltage enables pilot control of the electric motor during controlled operation. By adjusting the pilot voltage based on the detected voltage value of the time-rising starting voltage, efficient control of the electric motor can be achieved, as a voltage threshold below which proper control of the electric motor cannot be achieved can be taken into account. The pilot voltage is thus adapted to the specific requirements of the electric motor and its current operating conditions, enabling stable and efficient operation of the electric motor, particularly through closed-loop control.

[0022] The controller then provides a feedforward control based on the determined feedforward voltage. This feedforward control allows the electric motor to be efficiently controlled by compensating for potential load fluctuations or other operational disturbances in a timely manner to ensure stable operation of the electric motor.

[0023] One aspect of the invention relates to a computer-readable storage medium for permanently storing computer program instructions that can be executed by a processor, the computer program instructions implementing the steps of any of the preceding method claims.

[0024] The features, effects and advantages associated with the described aspects of the invention are described below.

[0025] Discrete position encoder pulses can be generated using a variety of sensors that detect the rotor position or the movement of the motor shaft, such as Hall sensors, optical encoders, or magnetic sensors. These sensors are typically located at specific rotor positions on the rotor or motor shaft and generate an electrical pulse each time the rotor reaches a specific angular position. The resulting pulse sequence provides information about the speed of the electric motor – the faster the speed, the more position encoder pulses are generated in a given period of time, or the time interval between two consecutive position encoder pulses becomes shorter. The speed of the electric motor can be determined in a conventional manner from the time between two position encoder pulses.It has proven advantageous to design the sensors equidistantly at an angular distance of 90° divided by the number of pole pairs of the position sensor.

[0026] By providing a starting voltage at motor start and detecting the voltage value at the first position sensor pulse, the electric motor can be started in a controlled manner. A pre-control voltage is then determined from the detected values, allowing the control behavior to be adapted to the respective motor load.

[0027] According to one embodiment, the starting voltage can be further increased after the first position sensor pulse. In this context, a higher value of the pre-control voltage means that this value is greater in magnitude than the detected voltage value. By further increasing the starting voltage, a load-related stoppage after the first position sensor pulse and before the occurrence of the second position sensor pulse is avoided and continuous operation is ensured. This approach improves the robustness of the control and prevents the electric motor from coming to a standstill after the first position sensor pulse, for example, due to frictional influences.

[0028] Increased motor load can be caused by increased friction between the parts moved by the electric motor, e.g., due to the ingress of dust or dirt between the moving parts. In such a case, the described concept can enable reliable starting of the electric motor, detection of starting conditions, and thus adapted feedforward control.

[0029] The determined pilot voltage is used for control to prevent excessively low control voltages from failing to achieve control intervention, as the friction cannot be overcome. Applying the pilot voltage prevents delayed start-up even with low control voltages.

[0030] The starting voltage can be in the form of a time-dependent, monotonically increasing function with a ramp-like progression, with the function preferably being constant at the beginning and end of a time range and increasing linearly in the middle time range. When an 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. A ramp-like progression of the starting voltage allows for a gradual increase in torque, which advantageously helps prevent the electric motor from stalling, particularly at higher loads, which can be caused by increased friction between the parts moved by the electric motor.

[0031] According to one embodiment, if the speed is known, control of the electric motor can begin after the second or third position sensor pulse. Before the first position sensor pulse is detected, operation can be controlled purely by the rising starting voltage. Short description of the characters

[0032] In the following, the invention is explained in more detail using exemplary embodiments and with reference to the drawing, in which: Fig. 1 is a block diagram of a device for controlling the speed of an electric motor according to the present invention; Fig. 2 is a schematic flow chart of a method for controlling the speed of an electric motor according to the present invention; and Fig. 3a-3c Diagrams illustrating the time course of the starting or control voltage for different loads on the electric motor. Description of implementation examples

[0033] Fig. 1 shows a device 20 according to the invention for operating an electric motor 10. The device 20 comprises: - A position sensor 22 which is designed to generate discrete position sensor pulses at discrete rotor positions of the electric motor 10; - an actuator 24 designed to provide a voltage for operating the electric motor 10; and - a control unit 26 which is coupled to the position sensor 22 and the actuator 24 and is designed to determine a pilot control voltage and to operate the electric motor 10 depending on the pilot control voltage.

[0034] The position sensor 22 can be designed as a Hall sensor, optical encoder, resolver, rotary encoder, incremental encoder, or magnetic sensor. The position sensor 22 delivers position sensor pulses when the rotor of the electric motor reaches a specific rotor position. Depending on the design, the distances between the positions of the position sensor at which position sensor pulses are generated vary.

[0035] The actuator 24 can be designed in the form of a power circuit to apply a voltage to the electric motor under the control of the control unit 22. The power circuit can comprise power semiconductor components and can be controlled, for example, by the control unit using pulse width modulation to apply a specific voltage to the electric motor 10.

[0036] The control unit 26 preferably comprises a microcontroller that executes a control algorithm in which the electric motor is operated in a starting phase to determine a pilot voltage and to provide a first speed indication for the further operation of the electric motor 10 in a normal operating phase.

[0037] The functions implemented by the control unit 26 include: - providing an increasing starting voltage for application to the electric motor 10; - the detection of position sensor pulses; - storing a voltage value of the starting voltage on the electric motor 10 upon occurrence of a first position sensor pulse, - the determination of a pilot voltage dependent on the voltage value of the control voltage detected at the first position sensor pulse, - determining a rotational speed after receiving a second position sensor signal, and - operating the electric motor based on the pilot voltage and speed.

[0038] Fig. 2 shows a flow chart of a method according to the invention for controlling the speed of an electric motor 10 as a function of a speed, wherein the speed is determined as a function of the detection of discrete position sensor pulses.

[0039] The procedure includes the following steps: - Providing in a step S1 a varying, time-increasing, starting voltage for starting the electric motor 10. The starting voltage begins at a temporally constant voltage level and increases monotonically after an initial period of time. - Storing in a step S2 the voltage value of the starting voltage when the first position sensor pulse occurs at a discrete rotor position of the electric motor 10. - Determining in a step S3 a pilot control voltage as a function of the stored voltage value; - After receiving a second position sensor pulse, determining in a step S4 a rotational speed of the electric motor 10; and - Providing in a step S5 a pilot control based on the pilot control voltage for operating the electric motor in a control dependent on the speed.

[0040] Furthermore, the starting voltage can be further increased after the first position sensor pulse in order to ensure reliable continued running of the rotor.

[0041] After the second position sensor pulse, a third position sensor pulse can be waited for before the control with the feedforward control is activated. This way, in addition to the speed, an acceleration can also be obtained, which results from the speed based on the time between the first and second position sensor pulses and the speed based on the time between the second and third position sensor pulses. The acceleration can be taken into account for the control of the electric motor, especially if it has a D component and is designed as a PD or PID control.

[0042] In the Fig. 3a-3c show time courses of the starting voltage and the control voltage for different loads.

[0043] Fig. Figure 3a shows a voltage U curve across the electric motor at low load. The starting voltage curve is initially constant and, due to the low load, causes the electric motor 10 to start. After the first position sensor pulse P1, the starting voltage is increased in a ramp-like manner by a predetermined amount for a period of time Z1 and then left constant. In the following constant voltage phase, the second and third position sensor pulses P2, P3 are detected in order to obtain the speed and acceleration for a control of the electric motor 10 that is initiated upon detection of the third position sensor pulse P3.

[0044] Fig. Figure 3b shows a voltage U curve across the electric motor at medium load. The starting voltage curve is initially constant and, due to the medium load, does not yet cause the electric motor 10 to start. The electric motor 10 starts up with the ramp-like increase in the starting voltage. After the first position sensor pulse P1, the starting voltage is further increased in a ramp-like manner by a predetermined amount for a time period Z1 and then left constant. In the following constant voltage phase, the second and third position sensor pulses P2, P3 are detected in order to obtain the speed and acceleration for a control of the electric motor 10 that is initiated upon detection of the third position sensor pulse P3.

[0045] Fig.Figure 3c shows a waveform of the voltage U across the electric motor at high load. The waveform of the starting voltage is initially constant and, due to the high load, does not yet cause the electric motor 10 to start. The electric motor starts up with the ramp-like increase in the starting voltage. After the first position sensor pulse P1, the starting voltage is increased in a ramp-like manner by a predetermined amount for a period of time Z1 and then left constant. In the following constant voltage phase, the second and third position sensor pulses are detected in order to obtain the speed and acceleration for a control of the electric motor 10 that is initiated upon detection of the third position sensor pulse.

[0046] By providing a temporally increasing starting voltage at the motor start and detecting the voltage value of the starting voltage at the first position sensor pulse, the electric motor 10 can be started in a controlled manner and, on the other hand, a suitable pilot control voltage can be determined so that subsequent operation can be adapted to the respective motor load.

Claims

[1] Method for operating an electric motor (10) depending on a speed indication, in particular with the aid of a speed control, wherein the speed indication is determined depending on the detection of discrete position sensor pulses, the method comprising the following steps: - Providing (S1) an increasing starting voltage for starting the electric motor (10); - determining (S2) a voltage value of the rising starting voltage upon occurrence of a first position sensor pulse (P1) at a discrete rotor position of the electric motor (10); - determining (S3) a pilot control voltage dependent on the voltage value of the rising starting voltage detected for the first position sensor pulse (P1); and - Operating (S5) the electric motor (10) as a function of a control voltage predetermined by an operating method, to which the pilot control voltage is applied, in particular additively or multiplicatively. [2] Method according to claim 1, wherein the electric motor (10) is operated according to a control, wherein the predetermined control voltage is provided by the control [3] Method according to claim 1 or 2, wherein the control voltage is further increased after the first position sensor pulse (P1), in particular in the form of a time-dependent function with a ramp-shaped, step-shaped, piecewise linear or sigmoidal course. [4] Method according to one of claims 1 to 3, wherein a second position sensor pulse (P2) is detected, wherein the speed indication is determined as a function of detection times of the first and the second position sensor pulse (P1, P2), wherein the electric motor (10) is operated as a function of the speed indication thus determined. [5] Method according to one of claims 1 to 4, wherein after the second position sensor pulse (P2) or after a third position sensor pulse (P3) a control is started which provides the control voltage. [6] Method according to one of claims 1 to 5, wherein the discrete position sensor pulses (P1, P2, P3) are supplied by one or more of the following sensors: Hall sensor, optical encoder, resolver, rotary encoder, incremental encoder, magnetic sensor. [7] Method according to one of claims 1 to 6, wherein the electric motor (10) is operated with a control, in particular a speed control, a position control or a torque control. [8] Device (20) for operating an electric motor (10) with a speed indication, in particular with the aid of a speed control comprising: - a position sensor (22) which is designed to generate discrete position sensor pulses at discrete rotor positions of the electric motor (10); - an actuator (24) designed to provide a voltage (U) for operating the electric motor (10); and - a control unit (26) which is coupled to the position sensor (22) and the actuator (24) and is designed to - to provide an increasing starting voltage for application to the electric motor (10) by the actuator (24); - to store the voltage value of the rising starting voltage applied to the electric motor (10) when a first position sensor pulse (P1) occurs at a discrete rotor position, - to determine a pilot voltage dependent on the voltage value of the rising starting voltage detected at the first position sensor pulse (P1), and - to operate the electric motor (10) depending on a predetermined control voltage, which is generated depending on the pilot control voltage, with the aid of the actuator (24). [9] Computer program product comprising instructions which, when the program is executed by at least one data processing device, cause the latter to carry out the steps of the method according to one of claims 1 to 7 by controlling the actuator (24). [10] Machine-readable storage medium comprising instructions which, when executed by at least one data processing device, cause the device to carry out the steps of the method according to one of claims 1 to 7.

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