Patent Application
20140172124
This application claims priority under 35 U.S.C. §119 to patent application no. DE 10 2012 223 573.6, filed on Dec. 18, 2012 in Germany, the disclosure of which is incorporated herein by reference in its entirety.
The present disclosure relates to a method for monitoring signal levels, to a device for monitoring signal levels, and also to a corresponding computer program product.
A position of a magnetic field of a rotor can be taken into consideration in order to control the process of electronically commutating a DC motor. At least one Hall sensor can be used for determining the position.
DE 10 2007 031 385 A1 describes a method and a device for detecting a low voltage supply at least of one Hall sensor.
On the basis of this background, the present disclosure discloses a method for monitoring signal levels of signals that are generated, for the purpose of detecting a magnetic field, by means of Hall sensors, the disclosure further discloses a device for monitoring signal levels that are generated, for the purpose of detecting a magnetic field, by Hall sensors and finally the disclosure discloses a corresponding computer program product in accordance with the independent claims. Advantageous embodiments are evident from the respective dependent claims and the description hereinunder.
In addition to monitoring a supply voltage of the Hall sensors, it is possible by forming an average value of the signals of several Hall sensors using electrical resistors to detect malfunctions in the connection lines. A malfunction site can be detected by means of comparing an expected progression of the average value with an actual progression.
The disclosure discloses a method for monitoring signal levels of signals that are generated, for the purpose of detecting a magnetic field, by means of Hall sensors, wherein the method comprises the following steps:
Furthermore, the disclosure discloses a device for monitoring signal levels of signals that are generated, for the purpose of detecting a magnetic field, by means of Hall sensors, wherein the device comprises the following features:
The object of the disclosure can also be achieved in a rapid and efficient manner by means of this design variant of the disclosure in the form of a device.
The term ‘signal level’ can be understood to mean an electric variable, by way of example an electric voltage. The signal level can result from a sensor detecting a change in a variable that is to be measured and said signal level can be ascertained in the signal line. The signal level can be dependent upon a supply voltage. The term “signal from a Hall sensor” can be understood to mean information regarding the strength of a magnetic flux of a magnetic field at the Hall sensor. The signal can be in an analog format or a binary format. If the signal is in a binary format, the signal can indicate whether the magnetic flux at the Hall sensor is greater or less than a threshold value. In order to form an average value of the signal levels, the signal levels can be directed by way of a respective electrical resistor and can be captured at a common point. The resistors can be identical for each of the signal levels. By way of example, a line resistance between the common point and the Hall sensors can also be of equal magnitude in each case. An expected progression can be an ideal progression. A tolerance range can represent a tolerable deviation of the signal level of the average value from the ideal progression. The expected progression can be stored in a memory device. Moreover, the tolerance range can be a tolerable temporal deviation of the average value from the ideal progression.
The term ‘device’ can be understood in this case to mean an electrical device that processes sensor signals and outputs control signals and/or data signals in dependence thereon. The device can comprise an interface that can be embodied in the form of hardware and/or software. In the case of interfaces in the form of hardware, the interfaces can be by way of example part of a so-called system—ASIC that includes the most varied functions of the devices. However, it is also possible that the interfaces are dedicated, integrated switching networks or are embodied at least in part from discrete components. In the case of interfaces in the form of software, the interfaces can be software modules that are provided in addition to other software modules by way of example on a microcontroller.
The error message can be provided if in the case of a transition between the values the average value dwells longer than a predetermined transition time outside a first tolerance range around the first value or outside a second tolerance range around the second value. The first tolerance range and the second tolerance range can be separated by a transition range. A predetermined transition time can be a transient recovery time that can occur in response to a change at least of one of the signal levels. By way of example, the average value can comprise an overshoot in the case of the transition between the values, which overshoot can be tolerable. The average value can likewise comprise an asymptotic approximation to the other value in the case of transition. In both cases, a tolerable time passes prior to the error message being provided.
The error message can be provided if the average value dwells longer than the transition time outside the first tolerance range or outside the second tolerance range or at least outside an additional tolerance range, wherein the additional tolerance range is arranged adjacent to the first tolerance range and/or the second tolerance range. The average value can by way of example comprise three stable values in the case of an even number of signals, which stable values each comprise a tolerance range. In the case of three signals, six discrete values of the average value can result as a result of using three resistors of different sizes in the lines to the Hall sensors, which discrete values can be monitored by means of the disclosed method. The tolerance ranges can be separated by means at least of an additional transition range and/or the transition range from the first tolerance range and/or the second tolerance range. The first tolerance range can be separated by a first blocking region from a minimum value of the average value. The second tolerance range can be separated by a second blocking region from a maximum value of the average value. The error message can be provided if the average value dwells longer than the transition time in the first blocking region or second blocking region.
The error message can include additional information that indicates from which tolerance range the average value deviates. As an alternative or in addition thereto, the error message can include additional information as to whether the average value dwells adjacent to a rising signal edge or adjacent to a falling signal edge. As a result of the content of detailed information, it is possible on the basis of the error message to locate a fundamental malfunction, by way of example, of the Hall sensors, in the signal lines and/or in the voltage supply more rapidly than in the case of a non-differentiated error message.
In the comparing step, position information regarding the magnetic field that is monitored by the Hall sensors is obtained from the average value, wherein the position information is determined from a correlation between an actual signal level of the average value and an angular position of the magnetic field. The expected progression can represent the correlation. The expected progression can be determined by way of example by recording the average value and the actual angular position of the magnetic field under controlled conditions. The expected progression can also be determined using a processing specification.
The average value can be determined from a first signal level, a second signal level and a third signal level. An angular resolution of 60° can be achieved in an electric motor using three Hall sensors if the Hall sensors are angularly displaced by 120° with respect to one another. When a function is performed correctly, the average value can comprise all the components of a regular progression that changes between a value of a third of a supply voltage of the Hall sensors and two thirds of the supply voltage.
Moreover, the average value can be determined from at least one additional signal level. As a result of additional Hall sensors, it is possible to achieve a higher level of angular resolution than in the case of three Hall sensors. By way of example, an angular resolution of 36° can be achieved using five Hall sensors that are arranged at regular intervals around the magnetic field.
The disclosure also advantageously discloses a computer program product having program code that can be saved to a machine-readable medium such as a semiconductor memory, a hard-disk storage device or an optical storage device and if the program product is implemented on a computer or a device said computer program is used to perform the method in accordance with one of the previously described embodiments.
The disclosure is further described hereinunder in an exemplary manner with reference to the attached drawings. In the drawings:
In the description hereinunder of preferred exemplary embodiments of the present disclosure, like or similar reference numerals are used for elements that are illustrated in the different figures and function in a similar manner, wherein the description of these elements is not repeated.
Different malfunctions in the signals 400 are illustrated in the second range 406. By way of example, a line defect 414 is illustrated in the second signal. The line defect 414 causes the second signal to fall prematurely from the high voltage value to the low voltage value, whereas the first signal and the second signal are undisturbed. The line defect 414 causes the average value 402 to fall from the second value 410 to the first value 408. Since the line is interrupted, the average value 402 traverses the transition range 412 at a sufficiently rapid rate and said average value comprises subsequently the first value 408. Consequently, the average value 402 fulfills the expected criteria and an error message is not provided. Once the magnetic field in the electric motor has deviated by 60°, the first signal falls as intended from the high voltage value to the low voltage value. The average value 402 therefore falls from the first value 408 to the ground potential and consequently into the first blocking region. At this point, the average value is outside the expected criteria and a first error message 416 is provided. It is clearly evident from the error message 416 that the malfunction relates to the second signal.
Subsequently, the figure illustrates by way of example a voltage drop 418 in the supply voltage at all the sensors. As a result of the voltage drop 418, the signals 400 in each case are no longer able to achieve the high voltage value. The low voltage value is maintained in the illustrated malfunction event. Since the average value 402 is formed by summating the three signals 400 whilst utilizing the resistors, illustrated in
For the purpose of monitoring Hall sensor signals 400 in particular in EC motors, three Hall sensor signals 400 that are to be monitored are combined by way of a diode network and conclusions relating to the Hall sensor supply voltage are drawn on the basis of measuring the resulting voltage. The Hall sensor signals 400 can be monitored using the disclosed method without having to use diodes. It is not the maximum voltage of the three Hall signals 400 that is determined but rather an arithmetic average value 402 is determined. The evaluation can be performed by means of a hardware device, as illustrated in
Since a non-statically allowed voltage range 412 is traversed for a short period of time during the transition from a statically allowed voltage value 408 to the other statically allowed voltage value 410, an evaluating device can detect this transition state and allow said transition state for a short period of time without triggering an error message. In the hardware version, this can be achieved by means of a downstream filter function. Alternatively, a software function can implement the filtering process.
The exemplary embodiments that are described and illustrated in the figures are selected only as examples. Different exemplary embodiments can be stand-alone or can be combined with one another in relation to individual features. An exemplary embodiment can also be supplemented by means of features of a further exemplary embodiment.
Moreover, method steps in accordance with the disclosure can be repeated and can be performed in a sequence that differs from the described sequence.
One exemplary embodiment comprises an “and/or”—combination between a first feature and a second feature, in other words, the exemplary embodiment in accordance with an embodiment comprises both the first feature and also the second feature and in accordance with a further embodiment comprises either only the first feature or only the second feature.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2012 223 573.6 | Dec 2012 | DE | national |
