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DE-102024210849-A1 - Method for operating a power steering system

DE102024210849A1DE 102024210849 A1DE102024210849 A1DE 102024210849A1DE-102024210849-A1

Abstract

Method for operating a power steering system comprising a rack driven for steering, wherein the method is executed when a fault occurs in the power steering system, a rack position requested for steering is specified, which is compared with an actual rack position so that a rack position deviation is determined, the rack speed is monitored, for which purpose it is recorded, the recorded rack speed is compared with at least one limit value, and the at least one limit value is set depending on the direction in which the rack is moving.

Inventors

  • Thomas Wanner
  • Jishnu Radhakrishnan
  • Akshay Cariappa Panathale Nandakumar

Assignees

  • Robert Bosch Gesellschaft mit beschränkter Haftung

Dates

Publication Date
20260513
Application Date
20241112

Claims (9)

  1. A method for operating a power steering system (502) comprising a rack (504) driven for steering, wherein: the method is executed when a fault occurs in the power steering system (502); a rack position (203, 300, 412, 432) requested for steering is specified and compared with an actual rack position (204, 410, 430) so that a rack position deviation (208) is determined; the rack speed is monitored, for which purpose it is recorded; the recorded rack speed is compared with at least one limit value (216); and the at least one limit value (216) is determined depending on the direction in which the rack (504) is moving.
  2. Procedure according to Claim 1 , in which a first limit is set for the case that the rack (504) moves towards the requested rack position (203, 300, 412, 432), and a second limit is set for the case that the rack (504) moves away from the requested rack position (203, 300, 412, 432), wherein the first limit is higher in magnitude than the second limit, resulting in asymmetric monitoring.
  3. Procedure according to Claim 1 or 2 , in which a factor is determined depending on the vehicle speed and the rack position deviation (208) with which at least one limit value (216) is determined.
  4. Procedure according to one of the Claims 1 until 3 , in which an additional limitation is imposed on the control of the rack (504).
  5. Procedure according to one of the Claims 1 until 4 , in which at least one countermeasure is initiated when at least one limit value (216) is reached.
  6. Procedure according to Claim 5 , in which, upon reaching at least one limit value (216), a limitation of the torque of the motor (110) that drives the rack (504) is implemented.
  7. Procedure according to Claim 5 or 6 , in which a warning is issued to the driver (22) when at least one limit value (216) is reached.
  8. Procedure according to Claim 7 , in which an optical and/or acoustic warning message is issued when at least one limit value (216) is reached.
  9. Arrangement for operating a power steering system in a vehicle (500) with an evaluation unit (508) for carrying out a method according to one of the Claims 1 until 8 is set up.

Description

The invention relates to a method for operating a power steering system and an arrangement for carrying out the method. State of the art Power steering, also known as assisted steering, reduces the force required to operate steering controls, particularly the steering wheel. This is helpful, for example, when steering while stationary, maneuvering, and at low speeds. Typically, an additional torque is provided by a motor, which compensates for the steering effort applied by the driver. In such a power steering system, for example, a rack and pinion drive is used, in which a rack is moved by a pinion turned by the steering handle and then usually moves a tie rod. The movement of this rack, especially its speed, is monitored to ensure the safe operation of the entire power steering system. Different levels of automation can be implemented in vehicle operation, depending on the extent to which the driver is supported in using the vehicle. SAE levels (SAE: Society of Automotive Engineers) are defined to precisely classify the degree of automation, using a scale of six levels. Level 0 corresponds to driving without any automation, while Level 5 represents full automation. These levels thus classify assisted, automated, and autonomous driving (Level 5). This section discusses SAE Level 2 and SAE Level 2+ in more detail, where the driver is permitted to remove their hands from the steering handlebars or steering wheel. During such driving operations, it must be ensured that safe continued driving is guaranteed even in the event of a system malfunction. Disclosure of the invention Against this background, a method with the features of claim 1 and an arrangement according to claim 9 are presented. Embodiments are described in the dependent claims and in the description. The presented method is used to operate a power steering system that includes a rack and pinion driven for steering. The method is executed particularly when a fault occurs in the power steering system. A rack position requested for steering is specified and compared with the actual rack position to determine any rack position deviation. The rack speed is then monitored by recording it, compared to a limit value, and the limit value is set depending on the direction of rack movement. In this method, a first limit value can be set for the case that the rack moves towards the requested rack position, and a second limit value can be set for the case that the rack moves away from the requested rack position, with the first limit value being higher in magnitude than the second limit value, resulting in asymmetric monitoring. In another embodiment, a factor is determined based on the vehicle speed and the rack position deviation, which is then used to define the limit value. Reference is made to the table below. The method can also include a limitation on the control of the rack. This can also be done asymmetrically. When the limit value is reached, at least one countermeasure can be initiated. For example, the torque of the motor driving the rack can be limited and/or a warning can be issued to the driver. In this procedure, the driver is permitted to take their hands off the steering wheel. This falls under SAE Level 2+. The aim is to ensure that, in the event of an error, the deviation from the trajectory does not exceed a certain degree within the driver's reaction time. Safety limits can be specified by the customer or driver. The presented arrangement serves to carry out the described procedure and is equipped with an evaluation unit for this purpose. The arrangement and/or the evaluation unit are implemented in hardware and/or software. Furthermore, the arrangement can be integrated into a vehicle's control unit or be designed as such a control unit. This control unit, in turn, is, for example, a steering control unit. Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings. It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention. Brief description of the drawings 1 A block diagram shows a vehicle at the vehicle level.2 A block diagram shows a steering control unit.3 A block diagram shows an embodiment of the presented safety mechanism.4 The diagram illustrates the mode of action of the presented method.5 shows different use cases.6 A flowchart shows a possible, highly simplified representation of the presented procedure.7 The figure shows, in a schematic, highly simplified representation, a vehicle with one embodiment of the described arrangement.8 It shows different scenarios in a graph. Embodiments of the invention The invention is schematically illustrated with reference to embodiments in the drawings and is described in detail below with reference to the drawings. 1 The block diagram shows the basic str