Method for determining rotor angular velocity

Abstract

This invention relates to a method for determining the rotor angular velocity of a power steering motor in a vehicle. [Solution] In this method, data representing information about the rotor angular velocity is used, the detected data is filtered by a filter, thereby obtaining filtered data, the filtered data is evaluated and the rotor angular velocity is determined.

Description

Technical Field

[0005] , ,

[0001] The present invention relates to a method for determining the rotor angular velocity of a motor of a power steering in a vehicle, particularly an automobile, and an apparatus for implementing the method.

Background Art

[0002] Prior Art Power steering (EPS: Electric Power Steering) is used to reduce the force required to operate the steering wheel of an automobile when steering during parking, driving, or low-speed driving. Power steering assists the driver's steering by amplifying the force applied by the driver for steering with a hydraulic system or a motor, particularly an electric motor.

[0003] In power steering, usually, a so-called steering control device (SCU: Steering Control Unit), that is, a control device equipped with an electric motor, is used, and this control device supports all driver assistance functions and, if necessary, also supports the function of autonomous driving.

[0004] Such a steering control device basically includes, particularly, a magnetic rotor attitude sensor or a rotor position sensor (RPS: Rotor Position Sensor). The rotor attitude sensor or the rotor position sensor has a permanent magnet and a detector for detecting a magnetic field to measure the rotor angle or the rotor attitude of the motor, particularly the rotor angular velocity. The motor drives the rack of a conventional power steering or controls or drives an actuator of a steer-by-wire steering system, a steering rack actuator (SRA: Steering Rack Actuator), and a steering wheel actuator (SWA: Steering Wheel Actuator).

[0005] To ensure safer operation of the steering system, a certain degree of interference resistance to magnetic field interference is necessary. This interference resistance can be tested within the framework of product verification related to electromagnetic compatibility (EMC). Such verification can be conducted not only to check the safety of operation but also to check driver comfort, in which case it is checked whether driver comfort is being compromised. [Overview of the project] [Problems that the invention aims to solve]

[0006] Magnetic interference affecting the SCU can be caused, for example, by a wire harness supplying power to a high-power vehicle, which is routed near the EPS-ECU. The magnetic field of high-current flowing through the cable harness can affect or interfere with systems for magnetic rotor attitude measurement. Since rotor attitude is an essential parameter for motor control, any static or alternating interference with rotor attitude measurement, particularly rotor angular velocity measurement, can affect motor operation. This can lead to adverse effects on comfort, such as audible and perceptible vibration (NVH: noise, vibration, harshness), which can affect the driver and passengers, even if the safe operation of the vehicle is guaranteed.

[0007] Known methods for reducing magnetic interference in rotor attitude measurement systems include, for example, implementing mechanical and magnetic shielding elements around the rotor attitude measurement system. The drawbacks are the additional costs for the mechanical and magnetic shielding elements, as well as the cost of installing shielding elements inside the control unit, and the residual magnetic effect of the shielding elements in clockwise and counterclockwise rotating motors, which particularly negatively impacts the accuracy of rotor attitude measurement. Further drawbacks include increased control unit package size, reduced possibility of integration into vehicle architectures, and reduced possibility of reusing existing control units.

[0008] Further known methods involve using alternative magnetic sensors with integrated interference compensation. In this case, the disadvantage is that interference-compensated rotor attitude sensors are more expensive than standard TMR sensors. Furthermore, such rotor attitude sensors require more sophisticated peripheral electrical circuitry, which incurs additional costs and necessitates an increased printed circuit board surface area. [Means for solving the problem]

[0009] Disclosure of the invention Based on the above background, a method having the features described in claim 1 and a control device described in claim 8 are proposed. Embodiments can be obtained from the dependent claims and the specification.

[0010] The proposed method is used to determine the rotor angular velocity of a power steering motor in a vehicle, particularly an automobile. In this method, data provided or detected by, for example, a rotor attitude sensor is used, and this data represents information about the rotor attitude, and especially the rotor angular velocity. The detected data is filtered, thereby obtaining filtered data, which is then evaluated to determine the rotor attitude, and specifically the rotor angular velocity. The determined rotor angular velocity can then be used to drive the motor, in particular.

[0011] The proposed method can improve customer satisfaction in power steering systems, particularly when magnetic field interference is present due to high-current vehicle power supply units, such as eDrive, electric stabilizers, heating systems, and boost regeneration modules, as well as corresponding cable harnesses wired near the SCU.

[0012] The proposed method makes it possible to reduce NVH effects caused by magnetic interference in the rotor attitude measurement system in power steering. Interference in the rotor attitude measurement system can be caused, for example, by external static or alternating magnetic fields near the SCU, and also by interference in the rotor attitude measurement system, which consists of permanent magnets attached to the motor shaft and, for example, a TMR sensor.

[0013] To address this, the proposed method suggests applying filtering software to rotor attitude measurement data, particularly rotor angular velocity, thereby reducing the effects caused by interfering external magnetic fields.

[0014] In one embodiment of the proposed method, a software filter is applied to the rotor attitude measurement data and the calculated rotor angular velocity in the motor control software. This reduces the influence of rotor attitude angle measurement, particularly in the important frequency range of 100 to 1000 Hz, thereby reducing NVH effects caused by interference from external magnetic fields and improving NVH performance.

[0015] In this method, a software filter is typically used, that is, software is used to perform filtering.

[0016] The data can be filtered to include rotor attitude measurement data and data on the derived rotor angular velocity.

[0017] In a further embodiment, the filter is configured to filter in a frequency range of 100 to 1000 Hz.

[0018] A notch filter can be used as a filter. Also called a bandstop filter or stop filter, a notch filter is designed to allow signals above and below a specific frequency band to pass through with as little alteration as possible. This allows for filtering and removal of frequencies within a specific narrow frequency range, depending on the situation. Therefore, conceptually, a notch is inserted into the frequency response diagram.

[0019] Furthermore, adjustable filters can be used, providing good customizability, for example, in software solutions.

[0020] The control device of this proposal is used to carry out the method described herein and for that purpose has a filter and an evaluation unit. The filter and / or evaluation unit may be implemented by hardware or software. Typically, the control device is provided in a steering control device.

[0021] The advantages of the solution presented here, which uses filtering software, are as follows:

[0022] There is no significant effect on steering feel from software stop filters or notch filters applied to rotor attitude and angular velocity data.

[0023] The characteristics of the software filter can be configured to suit the intended use, for example, by balancing steering feel and NVH performance.

[0024] No additional mechanical shielding against external magnetic fields is required, and therefore, no additional costs are incurred for mechanical and electronic devices. Furthermore, there is no increase in package size due to the incorporation of additional mechanical shielding elements.

[0025] The standard rotor attitude measurement system can be reused. Therefore, no budget is required for the development and certification of a new hardware rotor attitude measurement system. Thus, the hardware cost does not increase. The risks associated with the development of an alternative and more robust rotor attitude measurement solution are avoided.

[0026] Further advantages and embodiments of the present invention can be obtained from the specification and the attached drawings.

[0027] It is self-evident that the features described above and the features to be further described below can be used not only in the presented combinations but also in other combinations or alone without departing from the scope of the present invention.

Brief Description of the Drawings

[0028] [Figure 1] It is a diagram showing graphically the performance potential of the EPS system against magnetic interference. [Figure 2] It is a diagram showing graphically the filter characteristics for rotor attitude measurement data and the corresponding NVH performance at the target. [Figure 3] It is a diagram showing graphically the performance improvement by the rotor attitude filter software. [Figure 4] It is a diagram showing graphically the possible sequence of the proposed method by a flowchart. [Figure 5] It is a diagram showing a vehicle having an embodiment of the above-described device for implementing the present method in a purely schematic and greatly simplified representation.

Embodiments for Carrying Out the Invention

[0029] Embodiments of the Invention The present invention is schematically shown in the drawings based on embodiments and will be described in detail below with reference to the drawings.

[0030] Figure 1 shows the changes in requirements (envelope) and evaluation results in Graph 10, where frequency [Hz] is plotted on the horizontal axis 12 and magnetic field strength [A / m] on the vertical axis 14.

[0031] Based on Graph 10, it is possible to determine whether unacceptable NVH phenomena occur. For this purpose, the performance potential is compared to the required magnetic field test level for EMC product verification. The solid curve 20 and the dashed curve 22 show the customer envelope regarding the severity of the magnetic test, and the dotted curve 24 shows the NVH performance potential for various SCU generations.

[0032] Whenever the NVH performance potential 24, i.e., the maximum magnetic field without NVH, falls below the magnetic field test levels for product verification represented by curves 20 and 22, the EPS system will not meet the requirements for comfort performance in the vehicle in the presence of interference levels required for EMC certification.

[0033] Figure 2 shows the filter characteristics for RPS measurement data and the corresponding rotor speed for NVH performance in the target region in a graph 50 where frequency is plotted on the horizontal axis 52 and attenuation on the vertical axis 54.

[0034] The figure shows the filter curve 56 with respect to rotor speed decay. The filter characteristics, i.e., frequency and decay, are derived from Figure 1.

[0035] The motor control software considers the first derivative (dφ / dt) of the RPS angle measurement with respect to time, so a corresponding filter function is generated and applied to the calculated motor angular velocity.

[0036] Figure 3 shows the NVH performance potential achieved by the applied filter software in both enabled and disabled states in a specific EPS software. The figure shows graph 100, with frequency [Hz] plotted on the horizontal axis 102 and magnetic field strength [A / m] on the vertical axis 104. The figure shows the envelope for the required magnetic interference level 110 and two curves 112 and 114 for the NVH performance potential.

[0037] In the graph shown in Figure 3, there are still some frequency bands where the required characteristics are not provided by the initial measurements using the stop filter, which is a topic for filter configuration. The initial results clearly show the target improvement in the most important frequency range, denoted by reference numeral 120.

[0038] Figure 4 is a flowchart illustrating a significantly simplified possible process of the proposed method. In the first step 200, data from the rotor attitude sensor is used. In a further step 202, the rotor angular velocity is calculated using this data and filtered using the proposed notch filter. The filtered data is finally evaluated in step 204 to obtain information about the rotor attitude.

[0039] Figure 5 shows a vehicle, denoted by reference numeral 250, in a purely schematic and greatly simplified form. This vehicle 250 includes a steering control device 252, which itself includes a control device 260 and a motor 261. The control device 260 is equipped with a calculation unit 262, in which software that implements a filter 264 and an evaluation unit 266 is executed.

[0040] A rotor attitude sensor 270 is associated with the motor 261, and the rotor attitude sensor 270 provides data 272 about the rotor attitude, which is then provided to the control unit and, consequently, to the calculation unit 262. This data 272 is first filtered by a filter 264, which yields filtered data 280, and then the filtered data 280 is evaluated by an evaluation unit 266 so that the rotor attitude, particularly the rotor angular velocity 282, is presented as independently as possible of interference.

Claims

1. A method for determining the rotor angular velocity (282) of a power steering motor (261) in a vehicle (250), Data (272) representing information about the rotor angular velocity (282) is used. The detected data (272) is filtered by the filter (264), thereby obtaining filtered data (280). The filtered data (280) is evaluated to determine the rotor angular velocity (282). method.

2. The motor (261) is driven using the specified rotor angular velocity (282). The method according to claim 1.

3. Software filters are used. The method according to claim 1 or 2.

4. The filter (264) is configured to filter in a frequency range of 100 to 1000 Hz. The method according to any one of claims 1 to 3.

5. A notch filter is used. The method according to any one of claims 1 to 4.

6. An adjustable filter is used. The method according to any one of claims 1 to 5.

7. The aforementioned data (272) is provided by the rotor attitude sensor (270). The method according to any one of claims 1 to 6.

8. A control device for determining the rotor angular velocity (282) of a power steering motor (261) in a vehicle (250), comprising a calculation unit (262) for carrying out the method according to any one of claims 1 to 7.

9. The calculation unit (262) includes a filter (264) and an evaluation unit (266), The control device according to claim 8.

10. The filter (264) and / or the evaluation unit (266) are implemented by software. The control device according to claim 9.

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