Detection of high friction in a servo-electric steering gear due to rust

Abstract

System for detecting high friction in a steering system for a vehicle, comprising: a first set of vehicle sensors (17) to monitor initial vehicle parameters, a trigger block (15) which is operationally connected to the plurality of first vehicle sensors (17) for monitoring signals from the plurality of first vehicle sensors (17) and for determining whether the signals are within a predetermined range, a second set of vehicle parameter and steering system sensors (23) to monitor second vehicle parameters and steering system parameters, a depot (27) in which normal values ​​for the multitude of second vehicle parameters and steering system parameters for a functionally identical normal steering system are loaded, a correlation calculation and comparison block (21) which is operationally connected to the depot (27), the trigger block (15), the second set of vehicle parameter and steering system sensors (23), wherein the correlation calculation and comparison block (21) is designed to calculate a correlation from the second vehicle parameters and the steering system parameters of the second set of vehicle parameter and steering system sensors (23) with corresponding data of the second vehicle parameters and steering system parameters in the depot (27) within the framework of an MTS evaluation and to determine a respective MD parameter, wherein the correlation calculation and comparison block (21) is designed to send a warning signal if an MD parameter exceeds a predetermined value, and wherein the trigger block (15) is designed to activate the correlation calculation and comparison block (21) when the signals from the plurality of first vehicle sensors (17) are within the predetermined range.

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a system for detecting high friction in a steering system for a vehicle.

[0002] DE 10 2006 017 775 A1 discloses a method for detecting a defect in a steering system having at least one steering assistance means acting on a steering gear for providing a steering assistance torque to assist the manual torque applied by the driver and having an electronic unit for controlling and / or regulating the steering assistance means, wherein the current actual steering assistance torque is compared with a target steering assistance torque dependent on the current driving situation, and wherein, if the actual steering assistance torque exceeds the target steering assistance torque, increased friction is detected.

[0003] DE 10 2010 033 066 A1 discloses a method for detecting external shocks in vehicle steering systems.

[0004] US 2010 / 0 256 870 A1 discloses a method for estimating friction in a steering system controlled by a control module which performs the steps of: estimating a steering load gain, estimating a steering load hysteresis and determining the friction based on the steering load gain, the steering load hysteresis and a reference model.

[0005] In most vehicles today, the steering system is power assisted, and it is difficult to determine when problems are developing in the system. In particular, the steering gear for the steering system is usually located very low at the front of the vehicle. It is not uncommon for the steering gear to become damaged in such a way that water can enter the steering gear. There is usually a rubber bellows around the steering gear area, and damage to the bellows can allow water to enter the steering gear. The presence of water can cause the steering gear to rust, and if the rust becomes significant, the steering gear can fail. Unfortunately, due to the power assistance provided to the driver of the vehicle, the driver of the vehicle is not always aware of the higher frictions present in the steering system.If the rust damages the steering gear sufficiently, it is possible for the gear to fail, resulting in an inoperable vehicle. As the rust increases, the force required to operate the steering gear increases. If the force required to operate the steering gear becomes too high, the power boost provided to the steering system will be overtaxed in compensating for the increased force required to steer the vehicle, which could result in an unacceptably high force required to turn the steering wheel. Furthermore, if rust is present, if the power boost in the steering system fails, the force required to steer the vehicle may reach an unacceptable level for safe operation.Furthermore, allowing rust to develop to the point where the steering gear components are compromised will result in costly repairs that could have been prevented had the presence of rust been detected earlier.

[0006] It is an object of the invention to provide a system for detecting high friction in a steering system for a vehicle, which system warns the driver when the force required to operate the steering system has increased beyond a normal level.

[0007] The detection system is required to calculate a correlation between the various vehicle and steering gear parameters during vehicle operation. The system then calculates the normal parameters for the steering system and issues a warning if the correlation between the current and normal parameters for the steering system indicates that the friction loads in the steering system are not at an acceptable level. SUMMARY OF THE INVENTION

[0008] The invention provides a system for detecting high friction in a steering system for a vehicle according to claim 1.

[0009] The system is designed to detect high friction in a steering gear used in a vehicle. The device comprises a first sensor that monitors at least vehicle speed and a steering angle, a plurality of vehicle sensors to monitor vehicle parameters, and a plurality of steering system sensors to monitor steering system parameters. A repository stores the normal operating values ​​for the vehicle and steering system sensors. A correlation calculation and comparison block calculates a correlation for the vehicle and steering system values ​​and compares them with the values ​​in the repository. A trigger block receives signals from the speed and steering angle sensors and activates the correlation calculation and comparison block when the speed and steering angle sensors are within a selection range. Signals from other operating parameters can also be selected.The correlation calculation and comparison block sends a warning signal if the values ​​from the depot and the signal from the speed and steering angle sensors exceed a predetermined value. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram of an embodiment of the invention. Fig. Figure 2 is a graph of a set of variables measured as part of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0010] The invention relates to a system for detecting anomalies in a vehicle's steering system. In particular, the invention is directed to detecting any rust present in the steering system that may affect the functionality of the steering system. The rust is typically found in the steering gear, which is actuated to deliver steering inputs to the vehicle's steered wheels, but rust may also be found in other components of the steering system. The features of the invention will become more apparent upon consideration of the accompanying drawings and the following description.

[0011] Today's vehicles have a variety of systems that provide information that can be monitored and evaluated to determine the vehicle's condition. The multitude of available variables makes it difficult to properly evaluate the information and determine if an abnormal condition exists that requires further investigation. Mathematical systems have been developed to overcome this problem and enable evaluation of multiple variables. The Mahalanobis-Taguchi (MTS) system is a diagnostic or pattern recognition tool that can be used to detect anomalies for a combination of multiple variables. Samples of observations are taken from the various variables, and normal groups are created for these variables. Once a sample for the variables has been established from normal observations, a reference baseline, the Mahalanobis (MS), is identified.Once the reference baseline is established, the MTS system is able to distinguish normal measurements from an abnormal group of measurements. Using the sample of normal parameters / signals, a normal correlation matrix and mean values ​​are determined. These normal groups of parameters are used to calculate the Mahalanobis Distance (MD). The MD provides an evaluation tool that helps separate normal groups of parameters from abnormal groups of parameters. The difference between the correlation of the normal group and the abnormal group is the Mahalanobis Distance (MD). Essentially, a relatively high MD value is used to generate a signal that an abnormal condition exists.The mathematical calculations used for MTS evaluation are well known in the field, as is the calculation of the MD, which allows the identification of abnormal states in a group of variables. The details of the mathematical analysis are well known in the field, so a detailed description is unnecessary.

[0012] Fig. 1 shows the system of one embodiment of the present invention. The high friction detection system 10 includes a trigger block 15 operatively connected to a correlation calculation and comparison block 21. The trigger block 15 is also operatively connected to first sensors 17, which provide the trigger block with parameters related to the operation of the vehicle in which the high friction detection system 10 is located. Signals from the first sensors 17 are provided to the trigger block 15. The trigger block monitors signals received from the first sensors 17 and determines whether the signals are within a predetermined specific range. The first sensors 17 typically monitor the vehicle speed and the steering angle of the vehicle, and these parameters are provided to the trigger block 15.It should be noted that the first sensors can also monitor other vehicle parameters, and these other parameters can be used to activate the trigger block. To correlate with vehicle operating parameters, a specific range is pre-determined for the steering angle and vehicle speed within which high friction in the steering system can be detected. If the steering angle is below the preset value, there is not enough load in the steering system to detect high friction. If the vehicle is moving below a certain speed, the friction load caused by the vehicle's wheels makes it difficult to detect high friction in the steering system. Once the preset values ​​for the steering angle and vehicle speed are reached, the vehicle is in an operating state where the condition of the steering system can be evaluated.

[0013] A second set of sensors 23 is operatively connected to the correlation calculation and comparison block 21. The second set of sensors 23 monitors various driving and steering system parameters, such as rack force, lateral acceleration, longitudinal acceleration, vehicle speed, yaw rate, steering angle, steering speed, rotor angle, rotor speed, rotor motor torque, and handwheel (steering wheel) torque. The second set of sensors 23 provides the correlation calculation and comparison block 21 with a signal providing values ​​for these various parameters. The second set of sensors 23 continuously provides the input signals to the correlation calculation and comparison block while the vehicle is operating.

[0014] A normal sample repository 27 is connected to the correlation calculation and comparison block. Information regarding the normal ranges for the signals from the second set of sensors 23 can be loaded into the repository. The normal sample repository 27 then contains information consisting of the mean standard deviation, the correlation matrix, and the MD value for a normal steering system, i.e., a rust-free system. In most applications, the repository 27 is preloaded with these values ​​based on observations and measurements taken on a steering system functionally identical to the monitored steering system, wherein the identical steering system has been evaluated and exhibits no rust or other defects that would affect the readings from the second set of sensors 23.It is also possible for the depot 27 to learn or obtain normal operating parameters for the signals received from the second set of sensors 23 over a period of operation of the vehicle. The only difficulty with having the depot learn the normal values ​​for the signals from the second set of sensors is that the creation of the normal values ​​will be corrupted if rust or another defect already exists in the steering system. It is also possible for the depot 27 to monitor the signals from the second set of sensors 23 during operation of the vehicle. The information learned while monitoring these signals can be added to the depot and used to adjust the normal range for the signals from the second set of sensors 23 as conditions for the vehicle change over a period of time.The degree of adjustments based on changes in the signals during the vehicle's operating period could be limited so that the normal values ​​initially preloaded into the depot 27 are not unduly affected by changes in the signal that have developed over a period of time.

[0015] In operation, the trigger block 15 is used to activate the correlation calculation and comparison block 21 only when the signals from the first set of sensors 17 are within a specific range. The first set of sensors 17 is used to monitor the steering angle and vehicle speed, so the trigger block activates the correlation calculation and comparison block when these parameters are determined to be within the specific range. A correlation is then calculated for the incoming signals from the signals from the second set of sensors 23, and the incoming signals are compared with the standard sample data located in the standard sample repository 27. The correlation calculation and comparison block performs an MTS evaluation.If one of the parameters provided by the second set of sensors 23 has an MD, which is one of the calculated values ​​from the second set of sensors 23 that clearly differs from the standard sample, a signal is sent indicating a rust problem or other defect in the steering system. The signal sent by the correlation calculation and comparison block 21 indicates that the vehicle's steering system requires maintenance.

[0016] If the operating conditions of the steering angle and vehicle speed are outside the specific range specified in trigger block 15, the trigger block does not activate the correlation calculation and comparison block to perform an MTS evaluation of the steering system. If the parameters read by trigger block 15 are within the specified range, the trigger block activates correlation calculation and comparison block 21, and a continuous evaluation of the various signals from the second set of sensors 23 is performed. This evaluation of the signals from the second set of sensors 23 continues until the signals received by trigger block 15 are no longer within the specified range.

[0017] Fig. Figure 2 shows the basic evaluation process, where a group of signals from a second set of sensors 23 are similar to each other and are indicated by filled dots 35. Furthermore, Fig. 2, a cross-hatched point 37 is shown, which is so far removed from the filled points that it is clearly distinguishable from the other elements. The distance between the grouped signals represented by points 35 and the spaced point 37 is the MD for the parameters represented by the signals. In this case, the MD exceeds the predetermined level, indicating the presence of a defect in the steering system and a high probability that rust is present in the steering system.

Claims

[1] A system for detecting high friction in a steering system for a vehicle, comprising: a first plurality of vehicle sensors (17) for monitoring first vehicle parameters, a trigger block (15) operatively connected to the plurality of first vehicle sensors (17) for monitoring signals from the plurality of first vehicle sensors (17) and determining whether the signals are within a predetermined range, a second plurality of vehicle parameter and steering system sensors (23) for monitoring second vehicle parameters and steering system parameters, a depot (27) in which normal values ​​for the plurality of second vehicle parameters and steering system parameters for a functionally identical normal steering system are loaded, a correlation calculation and comparison block (21) operatively connected to the depot (27), the trigger block (15), the second plurality of vehicle parameter and steering system sensors (23), wherein the correlation calculation and comparison block (21) is designed to calculate a correlation with corresponding data of the second vehicle parameters and steering system parameters in the depot (27) from the second vehicle parameters and the steering system parameters of the second plurality of vehicle parameter and steering system sensors (23) as part of an MTS evaluation and to determine a respective MD parameter, wherein the correlation calculation and comparison block (21) is designed to send a warning signal if an MD parameter exceeds a predetermined value, and wherein the trigger block (15) is designed to activate the correlation calculation and comparison block (21) when the signals of the plurality of first vehicle sensors (17) are within the predetermined range. [2] The system of claim 1, wherein the first vehicle parameters are the speed of the vehicle and the steering angle in the steering system. [3] The system of claim 2, wherein the trigger block (15) is configured to activate the correlation calculation and comparison block (21) when the speed of the vehicle and the steering angle of the vehicle exceed a predetermined value. [4] The system of claim 1, wherein the second vehicle parameters monitored by the second plurality of vehicle parameter and steering system sensors (23) are selected from the group consisting of lateral acceleration, longitudinal acceleration, and yaw rate. [5] The system of claim 1, wherein the steering system parameters monitored by the second plurality of vehicle parameter and steering system sensors (23) are selected from the group consisting of steering speed, steering rotor angle, steering rotor speed, steering rotor torque, and steering wheel torque.

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