Position sensor and method for redundant determination of position
By using a method that directly detects the position using a primary sensor and derives the position based on driving parameters using a secondary sensor, the problems of susceptibility to interference and high cost of multi-chip sensors are solved, thereby improving security and flexibility.
Patent Information
- Application Number
- CN202510438008.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2024-04-10
- Filing Date
- 2025-04-09
- Publication Date
- 2025-10-17
AI Technical Summary
Existing multi-chip position sensors are susceptible to interference and costly in safety-critical applications, leading to an increased risk of system failure.
The primary sensor directly detects the position of the moving element, while the secondary sensor derives the position from the parameters of the driving motor. The motor position is detected by using multiple redundant signal paths, replacing the traditional dual-chip encoder sensor.
It reduces the risk of system failure, improves safety and flexibility, reduces costs, and ensures that the motor position can still be reliably determined in the event of sensor failure.
Smart Images
Figure CN120811203A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to a position sensor and a method for redundantly determining a position and, in particular, to a hybrid strategy for controlling a redundant electric motor in safety-critical applications based on a sensor-based and sensorless control. BACKGROUND
[0002] In particular in safety-critical applications, a redundant detection or determination of the motor position is of great interest in order to continue to determine the motor position even in the event of a sensor failure. Furthermore, redundant sensors can be used to detect errors, for example if there is a deviating measurement. The control of the motor control, for example of a braking or steering process, as well as the engagement of a gear in a gearshift mechanism or another actuator belong to these safety-critical applications. Wherever a high degree of reliability must be ensured, redundant detection is used. This means that possible errors do not lead to a failure of the overall system.
[0003] To this end, in conventional motors, for example, a position sensor with multiple sensor elements is used. For example, position sensors are known which are based on the magnetoresistive effect and in which at least two chips are integrated in the position sensor (so-called "dual-chip"). There, each chip can independently detect the position of an exemplary movable element. However, such a multi-chip application is usually very complex and expensive. Furthermore, it always happens that both chips suffer from errors due to their spatial and functional proximity. Thus, both chips can suffer from a short circuit at the same time. Likewise, external disturbances can adversely affect all chips which use the same measurement principle.
[0004] Therefore, there is a need for alternatives in order to replace these multi-chip position sensors by simple position sensors without endangering the safety of the overall system. SUMMARY
[0005] At least part of these problems is solved by the position sensor according to the present application and the method for detecting a position according to the present application. Further advantageous configurations are described in the description.
[0006] The present application relates to a position sensor for redundantly determining a position of an element movable by a drive motor. The position sensor comprises a primary sensor and a secondary sensor. The primary sensor is configured to directly sense the position of the movable element. The secondary sensor is configured to derive the position of the movable element from at least one secondary measurement. The secondary measurement is based on a drive variable of the drive motor or on a variable caused by the movement of the drive motor.
[0007] The direct position detection of the primary sensor is to be understood as meaning that the primary sensor directly detects the position of the movable element, for example by means of a magnetic or optical sensor, more precisely, independently of the manner in which the position of the movable element changes. In contrast, the secondary sensor is a position sensor which does not directly detect the position of the movable element, but instead detects a physical variable which defines the state of the drive motor, for example of a movable element of the drive motor, in order to achieve an estimate of the position change of the movable element on the basis thereof. For this purpose, for example, the drive signal of the electric motor can be utilized, from which it can be derived how the position of the movable element is changed by the drive signal.
[0008] The secondary sensor thus senses the cause or the consequence of the movement, whereas the primary sensor measures or detects the resulting movement. In this way, the motor position is determined using a plurality of different signal paths or using different approaches for each redundant path. The paths can be different types of encoder sensors, different algorithms for sensorless control or a combination of both approaches.
[0009] Optionally, the primary sensor is a position sensor having at least one of the following sensor elements: a magnetoresistive element, a Hall sensor, an optical sensor, a resistive sensor.
[0010] Optionally, the secondary sensor derives (or estimates) the position of the movable element on the basis of at least one of the following variables:
[0011] - a voltage signal for driving the drive motor,
[0012] - a current signal for driving the drive motor,
[0013] - an electromagnetic field caused by the drive motor,
[0014] - a change in the magnetic field caused by the drive motor,
[0015] - the duration of the drive for the drive motor,
[0016] - a combination formed therefrom.
[0017] Optionally, the position sensor comprises a magnetic element which can be mounted on the movable element. The primary sensor can measure the change in the magnetic field caused by the movement of the magnetic element and derive the position therefrom.
[0018] The embodiments also relate to a drive device having a drive motor and a movable element which can be moved by the drive motor. The drive device comprises the position sensor described previously.
[0019] Optionally, the drive motor can be redundantly actuated by a first phase signal and a second phase signal, wherein the first phase signal is based on the sensor data of the primary sensor and the second phase signal is based on the sensor data of the secondary sensor. The first and the second phase signal can be so-called phase groups, wherein each of the phase groups is configured for actuating the motor.
[0020] The drive motor can be, for example, an electric motor or a three-phase motor. However, it can also comprise a linear motor or another drive element which is configured for moving a movable element. The movement of the movable element can be, for example, a rotational movement, a linear movement or an axial movement, for example a steering movement or a braking process, but can also comprise a movement of a shift fork in a transmission, which engages into a switching element in order to switch a gear of the transmission. When the movable element performs a rotational movement, the position sought is the angular position of the movable element. It is also possible that an axial movement and a rotational movement are detected by the primary sensor and / or the secondary sensor in order to always ensure a reliable position finding when one of the two sensor elements fails.
[0021] The embodiments also relate to a method for redundantly finding a position of an element which is movable by a drive motor. The method comprises:
[0022] - directly detecting the position of the movable element by means of the primary sensor; and
[0023] - deriving the position of the movable element by means of the secondary sensor on the basis of a drive variable of the drive motor.
[0024] Optionally, the method further comprises calibrating the secondary sensor by means of the measurement data detected by the primary sensor.
[0025] It is to be understood that the primary sensor can also be calibrated. For this purpose, the position can be found by other measurement methods. For calibrating the secondary sensor, the drive motor can perform a movement of the movable element, wherein the movement of the movable element is detected by the primary sensor and at the same time by the secondary sensor. The resulting calibration data can be stored accordingly in the evaluation device, which can then perform a redundant detection of the position of the movable element (on the basis of the sensor data of the two sensor elements).
[0026] It is to be understood that all previously described functions of the position sensor are performed as further optional method steps according to further embodiments. Furthermore, it is to be understood that the order of the naming is not necessarily the order in which the method steps are performed. The steps can also be performed in other orders. It can also be necessary to perform only a part of the method steps. BRIEF DESCRIPTION OF DRAWINGS
[0027] The embodiments of the present application will be better understood from the following detailed description of various embodiments, with reference to the following drawings, in which:
[0028] Figure 1 A position sensor according to an embodiment of the present application is shown.
[0029] Figure 2 A schematic flow chart of a method for redundantly determining a position of a movable element according to an embodiment is shown. DETAILED DESCRIPTION
[0030] Figure 1 An embodiment for a position sensor is shown. The position sensor determines a position of an element 10, which can be moved by a drive motor 20. Here, such a movement can comprise an axial movement A and / or a rotational movement R. In order to determine the position of the movable element 10, the position sensor comprises a primary sensor 110 and a secondary sensor 120.
[0031] The primary sensor 110 directly detects a movement of the movable element 10. This can be done, for example, by a magnetic field measurement or an optical measurement and can be done independently of the drive motor 20. In other words, the reason for the movement has no influence on the position measurement itself, e.g. whether the element 10 is moved due to the drive motor 20 or due to another device.
[0032] In contrast, the secondary sensor 120 does not directly sense a movement of the element 10, but senses, for example, a physical quantity caused by the drive motor 20 driving or being driven. For example, the physical quantity can be a current or voltage signal with which the drive motor 20 is driven. For example, when an electric drive motor 20 is driven by an alternating current signal, a zero passage of the voltage or current can indicate the rotational position of the electric drive motor. Then, from this, the rotational position of the element 10 can be estimated or determined. Likewise, the physical quantity can comprise a duration. The duration can be the length of time for which the drive motor 20 is activated, from which the distance covered by the movable element 10 during the activation of the drive motor 20 can be determined. The secondary sensor 120 can also measure with an induced voltage or induced current signal, which is caused by the movement of the drive motor 20, for example by a present coil, wherein the induced voltage or current signal is not necessarily the drive signal of the motor 20 directly, but represents, for example, a secondary signal generated by the rotor.
[0033] Figure 2 An embodiment for redundantly determining a position of a movable element, such as in a position sensor according to the present application, is shown.Figure 1 The method comprises the following steps:
[0034] - detecting the position of the movable element 10 directly by means of the primary sensor 110; and
[0035] - deriving the position of the movable element 10 by means of the secondary sensor 120 on the basis of the drive variable of the drive motor 20.
[0036] Optionally, the method comprises calibrating the secondary sensor 120 by means of the measurement data detected by the primary sensor 110. In this way it can be ensured that in the correct operating mode of the primary sensor 110 and the secondary sensor 120, sensor data are provided which are indicative of the same position. If a deviation occurs, this can indicate an incorrect behaviour of the sensors.
[0037] It is understood that all the previously described functions of the evaluation circuit can be formed as further optional method steps. Furthermore, it is understood that the listed order is not necessarily the order in which the method steps are implemented. The steps can also be implemented in a different order or only a part of the method steps is implemented.
[0038] Likewise, the method can be carried out by a computer, that is to say, it can be implemented by means of instructions stored on a memory medium, and the instructions can implement the steps of the method when they are run on a processor. Typically, the instructions comprise one or more of the following instructions, which can be stored in different ways in the control unit (with processor) or in different media peripheral thereto, which, when read and implemented by the control unit, cause the control unit to implement the functions, performances and operations necessary for the implementation of the method according to the application.
[0039] The advantages of the embodiment lie, inter alia, in the fact that a very expensive dual-sensor element can be avoided for detecting the movement of the movable element 10. Thus, such a dual-Die-Encoder-Sensor can be replaced by a cheaper Single-Die-Variante, which is used here as the primary sensor 110. The desired redundancy is ensured by the secondary sensor 120.
[0040] Thus, these embodiments can be used in safety-critical applications, where a redundant determination of the motor position is of decisive importance in order to achieve a Fail-Operational-Modus. Since some embodiments utilize multiple signal paths, a disturbed signal path (e.g. due to a short circuit) cannot lead to a complete standstill. Thus, an error does not lead to a state of incapability, unlike in conventional dual-chip motor position sensors or conventional applications of multiple position sensors, where a disturbance can make multiple sensors unusable. Thus, there is the great advantage that different ways for determining the motor position significantly reduce the likelihood of a common error. Thereby, the safety of the product is significantly increased.
[0041] Furthermore, some embodiments provide the advantage that flexible sensorless algorithms can be retrofitted or updated over time, even if the control device has already been installed in a vehicle. This enables the implementation of better algorithms and thus an increase in motor power over time.
[0042] Overall, some embodiments thus reduce costs and increase flexibility without compromising safety.
[0043] Conventional motors for 4-level steering systems are for example designed as 2x3-phase groups (phase signals) (e.g. group 1 : XYZ and group 2: ABC), wherein each phase system is controlled by a redundant path and the determination of the motor position is done by a dual-chip encoder sensor (position sensor). According to some embodiments, the dual-chip encoder sensor can be replaced by a single-chip sensor for one of the redundant paths. Then, the required current for the phase group XYZ is calculated based on the position indicated by the magnetic field of a transmitter magnet on the motor shaft (as part of the primary sensor 110). This magnetic field is detected by the encoder sensor. For the other path (phase group ABC), a sensorless motor control algorithm can be used as secondary sensor 120. Depending on the type of algorithm, the position of the rotor can be estimated, e.g. based on the behavior of the motor 20. Then, the estimated position is used to determine the required current in the second phase group.
[0044] The features of the present application disclosed in the specification, claims and drawings can both separately and in any combination thereof be of importance for realizing the application.
[0045] List of reference signs
[0046] 10 movable element
[0047] 20 drive motor (e.g. electric motor)
[0048] 25 secondary measurement
[0049] 110 primary sensor
[0050] 120 secondary sensor
[0051] A, R motion (axial or rotational)
Claims
1. A position sensor for redundantly determining the position of an element (10), said element being movable by a drive motor (20), It is characterized in that - a primary sensor (110) is provided, which is configured to directly sense the position of the movable element (10); and A secondary sensor (120) is provided, which is designed to deduce the position of the movable element (10) from at least one secondary measurement (25), wherein the secondary measurement (25) is based on a drive variable of the drive motor (20).
2. The position sensor according to claim 1, It is characterized in that The primary sensor (110) is a position sensor having at least one of the following sensor elements: a magnetoresistive element, a Hall sensor, an optical sensor, a resistive sensor.
3. The position sensor according to claim 1 or claim 2, It is characterized in that The secondary sensor (120) estimates the position of the movable element (10) based on at least one of the following parameters: - a voltage signal for the drive motor (20), - a current signal for the drive motor (20), - an electromagnetic field caused by the drive motor (20); - a change in the magnetic field, said magnetic field being caused by said drive motor (20), - Duration of driving for the drive motor (20).
4. A position sensor according to any one of the preceding claims, It is characterized by: A magnetic element is provided, which can be mounted on the movable element (10), wherein the primary sensor (110) measures changes in the magnetic field caused by the movement of the magnetic element.
5. A drive device comprising a drive motor (20) and a movable element (10), wherein the movable element can be moved by the drive motor (20). It is characterized by: A position sensor according to any of the preceding claims is provided.
6. The driving device according to claim 5, wherein: The drive motor (20) can be controlled redundantly by a first phase signal and a second phase signal, It is characterized in that The first phase signal is based on sensor data of the primary sensor (110), and The second phase signal is based on sensor data of the secondary sensor (120).
7. A method for redundantly determining the position of an element (10), said element being movable by a drive motor (20), It is characterized in that - directly detecting (S110) the position of the movable element (10) by means of a primary sensor (110); and - Based on the drive variable of the drive motor (20), the position of the movable element (10) is derived (S120) by means of a secondary sensor (120).
8. The method according to claim 7, It is characterized in that The secondary sensor (120) is calibrated with the aid of measurement data detected by the primary sensor (110).