FORCE-BASED CORROSION DETECTION FOR A VEHICLE STEERING RACK

Abstract

A method for monitoring a corrosion status of a steering rack (101) in a steering system of a vehicle, the method comprising: detecting, from a rack position sensor (217, 117), first rack position data describing a first displacement of a pinion (103) of a vehicle with respect to an associated steering rack (101) of the vehicle; detecting, from a rack force sensor (115, 215), first rack force data describing a first force required to achieve the measured first displacement of the pinion (103); detecting, from a speed sensor (119, 219), first speed data describing a first speed of movement of the vehicle during the first displacement of the pinion (103); Generating a first estimated characteristic defined as the change in force divided by the change in displacement at the speed of movement; and Defining a corrosion status condition of the steering rack (101) based at least in part on a comparison of the estimated characteristic with a reference characteristic defining the expected results of a non-corroded steering rack (101), wherein the corrosion status condition of the steering rack (101) is defined as a high corrosion status if the estimated characteristic does not indicate performance within a threshold value of the reference characteristic, wherein the reference characteristic value is defined by one of the following: (a) a characteristic curve of relative rack force values versus rack position values corresponding to the behavior of a non-corroded steering rack (101) at a reference speed value, or (b) a lookup table of rack force values corresponding to rack position values at a reference speed value for a non-corroded steering rack (101). wherein the threshold value is defined by a characteristic curve of relative rack force values versus rack position values corresponding to the behavior of a non-corroded steering rack (101) at a reference speed value; further comprising instructions that, when executed by a processor (121), cause the processor (121) to perform a step of updating a data set of estimated curves stored in a curve data store that is in data communication with the processor (121); detecting, from the rack position sensor (217, 117), second rack position data describing a second displacement of the pinion (103) following the first displacement; detecting, from the rack force sensor (115, 215), second rack force data describing a second force required to achieve the measured second displacement of the pinion (103); detecting, from the speed sensor (119, 219), second speed data describing a second speed of movement of the vehicle during the second displacement of the pinion (103); Generating a second estimated characteristic defined as a second rack force data value divided by the second rack position data value at the second movement speed; Storing the generated second estimated characteristic curve in the curve data memory; and Updating the corrosion status condition of the steering rack (101) based at least in part on a comparison of the stored estimated characteristic curves with the reference characteristic curve defining the expected results of a non-corroded steering rack (101), wherein the corrosion status condition of the steering rack (101) is defined as a high corrosion status when an analytical representation of the values in the estimated characteristic curves does not indicate performance within a threshold value of the reference characteristic curve.

Description

TECHNICAL FIELD

[0001] This disclosure relates to the field of vehicle diagnostics and, in particular, diagnostics associated with vehicle steering systems. GENERAL STATE OF THE ART

[0002] Motor vehicles may use a steering mechanism that includes a rack-and-pinion system to control the direction of rotation of the vehicle's wheels. Under normal operating conditions, a vehicle's steering rack may be exposed to water, dirt, salt, or other road conditions known to cause corrosion. Steering rack corrosion can contribute to suboptimal performance of the steering mechanism, including requiring a greater amount of force to position the wheels during movement. Steering racks that have experienced sufficient corrosion may require maintenance, repair, or replacement for continued optimal vehicle operation.

[0003] Steering racks can corrode at varying rates depending on a number of factors, including localized exposure to corrosive conditions. Additionally, certain portions of the steering rack may corrode at a slower rate due to more consistent interaction with the pinion gear. Vehicles with autonomous or semi-autonomous capabilities may also benefit from a self-diagnostic feature to determine the level of corrosion on the steering rack.

[0004] DE 10 2012 005 116 B4 discloses a method and a device for monitoring an EPS steering system, as well as an EPS steering system. DE 11 2014 001 555 T5 discloses a power steering device comprising a steering load average calculation circuit 39 and an abnormality detection circuit 40. DE 10 2006 017 775 A1 discloses a method for detecting a defect in a steering system. SUMMARY

[0005] According to the invention, a method for monitoring a corrosion status of a steering rack in a steering system of a vehicle having the features of claim 1, a non-transitory computer-readable medium having the features of claim 2, and a corrosion detection system having the features of claim 3 are provided.

[0006] One aspect of this disclosure is directed to a method for monitoring the corrosion status of a steering rack in a steering system. The method may include measuring a displacement of a pinion relative to the rack, measuring the force required to achieve the displacement, and measuring the speed of movement of the vehicle during the displacement. Using these measurements, an estimated characteristic curve may be estimated for comparison with known data to determine a relative condition of the steering rack. The estimated characteristic curve may be compared to a reference curve or a lookup table of reference values to evaluate whether the steering rack requires maintenance, repair, or replacement.

[0007] Another aspect of this disclosure is directed to a non-transitory computer-readable medium comprising instructions stored thereon that, when executed by a processor, cause the processor to collect rack position sensor data, rack force sensor data, and speed sensor data. The instructions further cause the processor to define an estimated characteristic based on the collected data and compare the estimated characteristic to a reference characteristic defined by a characteristic curve or a lookup table of values. In some embodiments, instructions may cause the processor to add the estimated characteristic to a data set of estimated characteristics that form an estimated characteristic curve.In some embodiments, the instructions may cause the processor to repeat the functions and create an estimated characteristic curve that can be compared to a reference characteristic curve.

[0008] Another aspect of this disclosure is directed to a corrosion detection system operable to detect corrosion of a steering rack of a vehicle. The corrosion detection system includes a series of sensors operable to generate rack position data, rack force data, and speed data, a corrosion level indicator, a processor, and a data store including instructions operable to cause the processor to use the rack position data, the rack force data, and the speed data to activate the corrosion level indicator when the data corresponds to a high corrosion condition of the steering rack. In some embodiments, the high corrosion condition is determined using a reference curve or a reference lookup table.In some embodiments, the processor may comprise an electronic control unit (ECU) associated with the vehicle, a diagnostic dongle configured to connect to a diagnostic port of the vehicle, or a mobile processing device such as a smartphone or tablet computer.

[0009] The above aspects of this disclosure and other aspects are described in more detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is an illustration of the components of a corrosion detection system. Fig. Figure 2 is a diagrammatic illustration of the processor signal flow of a corrosion detection system. Fig. Figure 3 is a graph of characteristic curves useful in performing an analysis of steering rack corrosion based on measured rack force exertions. Fig. Figure 4 is a flowchart illustrating a method for corrosion detection. DETAILED DESCRIPTION

[0010] The illustrated embodiments are disclosed with reference to the drawings. It should be understood, however, that the disclosed embodiments are intended merely as examples that may be embodied in various and alternative forms. The figures are not necessarily to scale, and some features may be exaggerated or minimized to show details of particular components. The specific structural and functional details disclosed are not to be considered limiting, but rather as a representative basis for teaching one of ordinary skill in the art how to practice the disclosed concepts.

[0011] Fig. 1 illustrates a diagrammatic view of the components of a corrosion detection system 100. The corrosion detection system 100 monitors the condition of a steering rack 101 having a rack gear 102 operable to engage a pinion gear 103. The pinion gear 103 is coupled to a torsion bar 105 and operable to create movement within the steering rack 101 in a rack movement direction 106 in response to movement of a steering column 107 in a rotational direction 108 oriented in a torsional direction along the length of the steering column 107. The torsional forces causing the movement of the steering column 107 along the rotational direction 108 are a reaction to a torsional force exerted by a driver of the vehicle on a steering wheel 109 in a rotational direction 110. This interaction allows a driver to use a steering wheel 109 to steer the direction of wheels 111 of the vehicle.Each of the wheels 111 may be connected to the steering rack 101 via a tie rod 113 and a steering pin 114.

[0012] The steering rack 101 may be exposed to corrosive elements and environments during normal operation of the associated vehicle. When portions of the steering rack 101 are corroded, the associated force required to translate the steering rack 101 through the rack teeth 102 along a rack movement direction 106 increases compared to a non-corroded condition. Extensive corrosion of the steering rack 101 may cause suboptimal performance or possible failure to operate within specified parameters. It is therefore desirable to monitor the corrosion condition of the steering rack 101 to optimize vehicle operation.

[0013] In the illustrated embodiment, a pair of wheels 111 are coupled to a single steering rack 101, although other embodiments may include other arrangements without departing from the teachings disclosed herein. In the illustrated embodiment, the rack gearing 102 comprises a portion of the steering rack 101, although other embodiments may include other configurations of the rack gearing 102 without departing from the teachings disclosed herein.

[0014] The corrosion detection system 100 includes a series of sensors operable to provide data useful in making a determination about the corrosion conditions of the steering rack 101. A rack force sensor 115 is operable to measure the force of the torque along the rotational direction 108 on the steering column 107. Although the torque force is measured as being applied to the torsion bar 105 in the depicted embodiment, other embodiments may measure the force applied to shift the relative position of the pinion 103 with respect to the steering rack 101 on the steering wheel 109, the steering column 107, or the pinion 103 without departing from the teachings disclosed herein. The rack force sensor 115 may also be advantageously linked to other systems of the vehicle without departing from the teachings disclosed herein.In the depicted embodiment, the rack force sensor 115 is disposed on the steering rack 101, although other embodiments may include other arrangements, such as the torsion bar 105, the steering column 107, the steering wheel 109, or any other location operable to monitor the force applied to the torsion bar 105 without departing from the teachings disclosed herein. In some embodiments, the rack force sensor 115 may include a motor torque sensor, a torsion bar torque sensor, a differential force sensor, or any other alternative equivalent known to those of ordinary skill in the art without departing from the teachings disclosed herein.

[0015] In some embodiments, the corrosion detection system 100 may further include a power steering feature, such as a steering motor 116. The steering motor 116 may be operable to apply a supplemental force to the steering rack 101 so that the position and movement of the steering rack 101 are optimally controlled. In the depicted embodiment, the steering motor 116 may include an electric steering motor. In some embodiments, the steering motor 116 may include a hydraulic steering motor, a pneumatic steering motor, a combination of the above steering motor configurations, or any other alternative equivalent known to those of ordinary skill in the art without departing from the teachings disclosed herein.

[0016] The corrosion detection system 100 also includes a rack position sensor 117 operable to measure the displacement of the pinion 103 from a neutral position of the steering rack 101 within the range of the rack teeth 102. Larger displacements from the neutral position are expected to require greater torque under normal operating conditions, and thus, the displacement must be linked to the force measured by the rack force sensor 115 to estimate the corrosion level. Furthermore, since different portions of the steering rack 101 may corrode at different rates, the displacement measurements can advantageously reveal that only certain portions of the steering rack 101 are suffering from corrosion.For example, because the pinion gear 103 is subjected to smaller displacements more frequently than larger displacements, the pinion gear 103 may exert a "polishing" effect on the rack gear 102, with repeated interaction with portions of the rack gear 102 preventing buildup of corrosion or corroded elements near the neutral position. In contrast, because the pinion gear 103 may not be translated as frequently near the endpoints of the rack gear 102, greater corrosion and a greater buildup of corrosive elements near the endpoints of the rack gear 102 can be expected during normal operation.In the depicted embodiment, the rack position sensor 117 is disposed in close proximity to the pinion gear 103, although other embodiments may include other locations, such as along the steering rack 101, near the rack gears 102, along the steering column 107, within the steering wheel 109, coupled to the steering motor 116, at another point within the vehicle, or at any other point within the displacement of the pinion gear 103 with respect to the rack gears 102, without departing from the teachings disclosed herein. In some embodiments, the rack position sensor 117 may also be advantageously linked to other systems of the vehicle without departing from the teachings disclosed herein.

[0017] During normal operation, the speed of movement of the vehicle may also affect the force required to successfully turn the wheels 111. For example, if the vehicle is moving at very high speeds, more energy may be required to change the position of the wheels 111 during movement. In general, very high speeds may require greater force to overcome lateral acceleration, and very low speeds may require greater force to overcome friction between a wheel 111 and the road surface. A speed sensor 119 may be operable to measure the speed of movement of the vehicle.In the depicted embodiment, the speed sensor 119 is located within the structure of one of the wheels 111, although other embodiments may include other locations, such as along an axle, within proximity of an axle or wheel not associated with the corrosion detection system, elsewhere within the vehicle, external to the vehicle, or at any other location operable to monitor the speed of movement of the vehicle without departing from the teachings disclosed herein. In some embodiments, the speed sensor 119 may determine the speed of movement of the vehicle using Global Positioning System (GPS) tracking. In some embodiments, the speed sensor 119 may also be advantageously associated with other systems of the vehicle without departing from the teachings disclosed herein.

[0018] Each of the rack force sensor 115, the rack position sensor 117, and the speed sensor 119 may be in data communication with a processor 121 operable to perform analytical functions on the measured data provided by the sensors. In the depicted embodiment, the processor 121 may comprise an electronic control unit (ECU) of the vehicle, although other embodiments may comprise a diagnostic dongle configured to interface with a diagnostic port of the vehicle, or a portable processing device such as a smartphone or tablet computer, a cloud-based processing device, a network computer, a personal computer, a laptop computer, or any other alternative equivalent device known to those of ordinary skill in the art without departing from the teachings disclosed herein.In the illustrated embodiment, a processor 121 is disposed proximate the steering rack 101, although other embodiments may have different arrangements without departing from the teachings disclosed herein.

[0019] The processor 121 may also be in data communication with a data store 123, which may include instructions for execution by the processor 121. The data store 123 may also function as a data repository for the processor 121 or other processors associated with other systems of the vehicle. The data store 123 may be implemented as a non-transitory computer-readable medium or a machine-readable storage medium for carrying or having computer-executable instructions or data structures stored thereon. Such non-transitory computer-readable media or machine-readable storage media may be any available media implemented in hardware or a physical form accessible by a general-purpose or special-purpose processor.By way of example and not limitation, such non-transitory computer-readable media or machine-readable storage media may include random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), optical disk storage, magnetic disk storage, linear magnetic data storage, magnetic storage devices, flash memory, or any other medium that can be used to carry or store desired program code means in the form of computer-executable instructions or data structures. Combinations of the above should also be included within the scope of non-transitory computer-readable media or machine-readable storage media.In the depicted embodiment, processor 121 is in wired communication with data storage 123, although other embodiments may have a wireless configuration without departing from the teachings disclosed herein.

[0020] The processor 121 may also be in data communication with a corrosion level indicator 125 operable to provide an indication to a user, technician, or driver of the estimated level of corrosion on the steering rack 101. In the depicted embodiment, the corrosion level indicator 125 may include a warning light, an indicator within the vehicle, an indicator separate from the vehicle, an audible alarm, a haptic alarm, or any other indicator known to those of ordinary skill in the art as suitable for communicating a condition of the vehicle to a user, technician, or driver without departing from the teachings disclosed herein.In the depicted embodiment, the processor 121 is in wireless communication with the corrosion level indicator 125, although other embodiments may include wired configurations without departing from the teachings disclosed herein.

[0021] In some embodiments, the corrosion detection system 100 may advantageously utilize existing sensors to collect rack force data, rack position data, and speed data describing the conditions of the vehicle.

[0022] Fig. Figure 2 is a diagrammatic illustration of the signal flow of a processor 200 in a corrosion detection system. The processor 200 may include a processor 121 (see Fig. 1) or, in other embodiments, include other alternative arrangements without departing from the teachings disclosed herein. Processor 200 includes an input array 201, a processing group 203, and an output array 205.

[0023] The input array 201 may include input channels that provide measurement data from a rack force sensor 215, a rack position sensor 217, and a speed sensor 219. In the illustrated embodiment, these sensors may be the sensors of the corrosion detection system 100 (see Fig. 1) or any alternative configuration operable to provide measurement data including rack force data, rack position data, and speed data, respectively. The measurement data provided by the rack force sensor 215, the rack position sensor 217, and the speed sensor 219 may be processed by the processing group 203 to estimate corrosion levels in a steering rack.

[0024] The processing group 203 may utilize a lookup table comparator 225 to estimate corrosion levels in a steering rack. The lookup table comparator 225 may include a 2-dimensional lookup table of expected rack force data values for a predetermined set of rack position data and speed values. The expected rack force data values of the lookup table may be populated based on measurements of a non-corroded steering rack. The expected rack force data values of the lookup table may be determined based on the steering rack and vehicle specifications. The lookup table comparator 225 may output a comparison result based on a comparison of the measured rack force data with the expected rack force data.In the depicted embodiment, the lookup table comparator 225 outputs an indication signal based on whether the measured rack force data from the rack force sensor 215 is within a predetermined tolerance of the associated expected rack force data from the lookup table. Since other factors, such as improperly inflated tires or poor wheel alignment, can increase the rack force required to achieve a particular displacement, the threshold values can be selected to minimize or eliminate the possibility of factors other than steering rack corrosion. The output of the lookup table comparator 225 can then be fed to a condition check 231, where the output of the lookup table comparator 225 can be used to determine a corrosion condition.

[0025] The processing group 203 may utilize a characteristic curve comparator 233 to estimate corrosion levels in a steering rack. The characteristic curve comparator 233 may include a set of 2-dimensional reference curves representing expected characteristics of a non-corroded steering rack at a particular speed of travel. The set of reference curves may advantageously provide interpolated values for comparison in cases where the measured rack displacement or the measured rack force do not match the expected values of the reference measurements. The shape of the reference curves provides an indication of expected changes in rack force relative to a displacement in rack position.The reference curves may be compared to a measured curve formed by repeated measurements of rack force versus rack displacement during normal operation of a vehicle. The curve comparator 233 may be configured to compare relative changes in the rack force data against changes in the rack position data. The curve comparator 233 may be operable to generate an indication signal based on whether the measured rack force data from the rack force sensor 215 is within a predetermined tolerance of the associated expected rack force data from the curves. The output of the curve comparator 233 may then be fed to a condition checker 231, wherein the output of the curve comparator 233 may be used to determine a corrosion condition.

[0026] In some embodiments, the vehicle load may affect the necessary rack force required to adjust the rack position for a given displacement. Generally, a larger load carried by the vehicle may require a larger rack force for a given displacement. However, the relative change in rack force versus a change in displacement is known to be consistent across vehicle loads. Thus, the curve comparator 233 may advantageously compare the relative changes in rack force rather than the absolute rack force to adapt to vehicle operation at different loads.

[0027] The condition check 231 may generate output signals in response to the received indication signals from the lookup table comparator 225 or the characteristic curve comparator 233. The output signals may be generated based on one or more of the output signals from the comparators indicating a particular corrosion condition of a steering rack. By way of example, and not limitation, the output signal may include activation of a visual indicator, a display of an estimated condition of the steering rack, an audible alarm, or other alternative output recognizable by one of ordinary skill in the art without departing from the teachings disclosed herein. Other embodiments may include other forms of comparison without departing from the teachings disclosed herein.

[0028] Fig. 3 comprises a set of characteristics of the type used by the characteristic comparator 233 (see Fig. 2) can be used. The curves illustrate a rack force required to achieve a particular rack position of displacement. In the depicted embodiment, the force f is measured in Newtons (N) and the displacement d is measured in millimeters (mm) from a neutral position, although other embodiments may include other configurations without departing from the teachings disclosed herein. In some embodiments, the force f may be a torque applied to a torsion bar, the steering column, or the steering wheel, measured in Newton-meters, foot-pounds, or any other equivalent metric known to one of ordinary skill in the art without departing from the teachings disclosed herein.In some embodiments, the displacement d may be measured in feet, inches, meters, or any other linear distance metric known to one of ordinary skill in the art without departing from the teachings disclosed herein. In some embodiments, the displacement d may be a rotational distance of a torsion bar, steering column, or steering wheel measured in degrees, radians, or any other equivalent rotational distance metric known to one of ordinary skill in the art without departing from the teachings disclosed herein. A series of reference curves 301 represent the expected characteristics of an uncorroded steering rack at different speeds.The reference curve 301a represents the force required for each displacement when the associated vehicle is stationary, whereas the reference curves 301b, 301c, 301d, and 301e each represent the force required for the displacements at increasing vehicle speeds. Superimposed over the reference curves 301 is a measurement curve 303 representing a characteristic curve developed by taking rack force measurements and rack position measurements for a vehicle during normal operation. In the illustrated embodiment, the measurement curve 303 corresponds to a single speed of movement of the vehicle, although other embodiments may include additional measurement curves corresponding to other speeds of movement. The measurement curve 303 consists of a series of measurement points, with each measurement point corresponding to a specific rack position on the curve.The measurement points of the measurement curve 303 are interpolated to form the remaining portions of the curve by approximation. In the illustrated embodiment, linear interpolation was used; however, other embodiments may use other interpolations, such as higher-order interpolations, geometric interpolations, or any other interpolation known to one of ordinary skill in the art, without departing from the teachings disclosed herein.

[0029] In some embodiments, the characteristic curve comparator may depend on the discrete measurement points of the measurement curve 303 compared to the one or more reference curves 301. In some embodiments, the characteristic curve comparator may depend on interpolations between the measurement points, utilizing a change in the rack force value, Δf, versus a change in the rack position value, Δd. Comparisons of changes in value may provide an alternative interpretation of the measurement value, which may be useful in determining whether the measurement data falls within a selected threshold of expected data. In the depicted embodiment, a particular Δf 305 is illustrated for a particular Δd 307 between displacements of -50 and -60 degrees, although Δf and Δd values may be calculated between any two points on the measurement curve 303.

[0030] In some embodiments, a curve comparator may determine a high corrosion condition if some or all of the measured curves do not fall within a threshold of expected results dictated by the associated reference curve for the same vehicle speed of travel. In some embodiments, the curve comparator may make such a determination based on measured curves associated with multiple different travel speeds. In some embodiments, a high corrosion condition may be determined if a measured curve for a particular travel speed intersects one or more of the reference curves at other travel speeds.

[0031] Fig. 4 represents a method for determining a corrosion condition of a steering rack of a vehicle according to an embodiment of the teachings herein. The illustrated method may be implemented by a corrosion detection system 100 (see Fig. 1) or a processor thereof, such as a processor 200 (see Fig. 2), although other embodiments may include other methods without departing from the teachings disclosed herein.

[0032] The method begins at step 400, where measurements of rack displacement data describing the displacement of a steering gear from a neutral position along the steering rack, rack force data describing the force required to achieve the displacement, and speed data describing the speed of movement of the associated vehicle are acquired. The rack displacement data, rack force data, and speed data may be collectively referred to in this specification as "measurement data."

[0033] After acquiring the measurement data, the method may proceed to step 402, where the measurement data is used to compare the measured rack force data with an expected reference value found in a lookup table. The difference between the measured values and the lookup table values may then be recorded for analysis in a later step. Some embodiments may not include step 402 and may instead include only other analytical steps.

[0034] After acquiring the measurement data, the method may proceed to step 403, where the measurement data is used to update a measured characteristic curve describing the relationship of the rack force data with respect to the rack displacement data at the speeds defined by the velocity data. This measurement curve may be stored as a pre-existing data set that is updated using the method or may be instantiated upon first execution of the method. In some embodiments, the measurement data is used to develop a measured characteristic curve that utilizes a weighted data history to develop an average of measured data and previously measured data. In some embodiments, a combination of the measured data and previously measured data is combined using a windowed data average.In some embodiments, both a weighted average and a window average may be used to update the measured characteristic curve. In some embodiments, the measured characteristic curve may be represented by a matrix of characteristic curves corresponding to different movement speeds.

[0035] After the measured characteristic curve has been correctly updated in step 403, the method proceeds to step 404, where the measured characteristic curve is compared to a set of reference curves defining expected data based on a non-corroded steering rack. The difference between the measured characteristic curve and the associated reference characteristic curve may then be recorded for output to the next step. In some embodiments, the differences between the measured characteristic curve and the associated reference characteristic curve may be represented by a single data value, a vector of difference values, or a matrix of difference values without departing from the teachings disclosed herein. Some embodiments may not include steps 403 and 404 and instead include only other analytical steps.In the depicted embodiment, step 402 is performed concurrently with steps 403 and 404, although other embodiments may include performing the steps sequentially without departing from the teachings disclosed herein. In practice, the steps may be performed in any order as long as step 403 is performed before step 404. In some embodiments, step 403 may be omitted, and the measured characteristic curve may be instantiated using only the measurement data acquired in step 400.

[0036] After performing some of steps 402, 403, and 404, the recorded difference data is considered at step 406, where each of the differences represented in the difference data is analyzed to determine whether all of the difference data represent differences within a predetermined tolerance of the method. The tolerance may be selected based on a particular specification of the vehicle and steering rack and may be selected to reflect normal operating variances of the vehicle using a non-corroded steering rack.

[0037] If the difference data indicates that some difference values are not within tolerances, the method proceeds to step 408, where a corrosion status indicator is set to indicate a high corrosion status. In some embodiments, different thresholds may be used to correspond to respective increasing levels of corrosion, such as a minimal corrosion status or a moderate corrosion status of the steering rack. If the difference data corresponds to conditions compliant with the tolerances, step 408 may not be performed. After determining compliance with tolerances, the method proceeds to step 410, where it is determined whether monitoring for the vehicle is complete. If further monitoring is desired, such as continued operation of the vehicle, the method returns to step 400 to perform another iteration of the method.If no further monitoring is desired, the method instead proceeds to step 412, where the method ends.

[0038] Although exemplary embodiments are described above, these embodiments are not intended to describe all possible forms of the disclosed device and method. Instead, the terms used in the description are for the purpose of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure as claimed. The features of various implementing embodiments may be combined to form further embodiments of the disclosed concepts.

Claims

[1] A method for monitoring a corrosion status of a steering rack (101) in a steering system of a vehicle, the method comprising: detecting, from a rack position sensor (217, 117), first rack position data describing a first displacement of a pinion (103) of a vehicle with respect to an associated steering rack (101) of the vehicle; detecting, from a rack force sensor (115, 215), first rack force data describing a first force required to achieve the measured first displacement of the pinion (103); detecting, from a speed sensor (119, 219), first speed data describing a first speed of movement of the vehicle during the first displacement of the pinion (103); Generating a first estimated characteristic defined as the change in force divided by the change in displacement at the speed of movement; and Defining a corrosion status condition of the steering rack (101) based at least in part on a comparison of the estimated characteristic with a reference characteristic defining the expected results of a non-corroded steering rack (101), wherein the corrosion status condition of the steering rack (101) is defined as a high corrosion status if the estimated characteristic does not indicate performance within a threshold value of the reference characteristic, wherein the reference characteristic value is defined by one of the following: (a) a characteristic curve of relative rack force values versus rack position values corresponding to the behavior of a non-corroded steering rack (101) at a reference speed value, or (b) a lookup table of rack force values corresponding to rack position values at a reference speed value for a non-corroded steering rack (101). wherein the threshold value is defined by a characteristic curve of relative rack force values versus rack position values corresponding to the behavior of a non-corroded steering rack (101) at a reference speed value; further comprising instructions that, when executed by a processor (121), cause the processor (121) to perform a step of updating a data set of estimated curves stored in a curve data store that is in data communication with the processor (121); detecting, from the rack position sensor (217, 117), second rack position data describing a second displacement of the pinion (103) following the first displacement; detecting, from the rack force sensor (115, 215), second rack force data describing a second force required to achieve the measured second displacement of the pinion (103); detecting, from the speed sensor (119, 219), second speed data describing a second speed of movement of the vehicle during the second displacement of the pinion (103); Generating a second estimated characteristic defined as a second rack force data value divided by the second rack position data value at the second movement speed; Storing the generated second estimated characteristic curve in the curve data memory; and Updating the corrosion status of the steering rack (101) based at least in part on a comparison of the stored estimated characteristic curves with the reference characteristic curve defining the expected results of a non-corroded steering rack (101), wherein the corrosion status of the steering rack (101) is defined as a high corrosion status when an analytical representation of the values in the estimated characteristic curves does not indicate performance within a threshold value of the reference characteristic curve. [2] A non-transitory computer-readable medium comprising instructions stored thereon which, when executed by a processor (121), cause the processor (121) to perform the following steps: detecting, from a rack position sensor (217, 117), first rack position data describing a first displacement of a pinion (103) of a vehicle with respect to an associated steering rack (101) of the vehicle; detecting, from a rack force sensor (115, 215), first rack force data describing a first force required to achieve the measured first displacement of the pinion (103); detecting, from a speed sensor (119, 219), first speed data describing a first speed of movement of the vehicle during the first displacement of the pinion (103); Generating a first estimated characteristic defined as the change in force divided by the change in displacement at the speed of movement; and Defining a corrosion status condition of the steering rack (101) based at least in part on a comparison of the estimated characteristic with a reference characteristic defining the expected results of a non-corroded steering rack (101), wherein the corrosion status condition of the steering rack (101) is defined as a high corrosion status if the estimated characteristic does not indicate performance within a threshold value of the reference characteristic, wherein the reference characteristic value is defined by one of the following: (a) a characteristic curve of relative rack force values versus rack position values corresponding to the behavior of a non-corroded steering rack (101) at a reference speed value, or (b) a lookup table of rack force values corresponding to rack position values at a reference speed value for a non-corroded steering rack (101). wherein the threshold value is defined by a characteristic curve of relative rack force values versus rack position values corresponding to the behavior of a non-corroded steering rack (101) at a reference speed value; further comprising instructions that, when executed by a processor (121), cause the processor (121) to perform a step of updating a data set of estimated curves stored in a curve data store that is in data communication with the processor (121); detecting, from the rack position sensor (217, 117), second rack position data describing a second displacement of the pinion (103) following the first displacement; detecting, from the rack force sensor (115, 215), second rack force data describing a second force required to achieve the measured second displacement of the pinion (103); detecting, from the speed sensor (119, 219), second speed data describing a second speed of movement of the vehicle during the second displacement of the pinion (103); Generating a second estimated characteristic defined as a second rack force data value divided by the second rack position data value at the second movement speed; Storing the generated second estimated characteristic curve in the curve data memory; and Updating the corrosion status of the steering rack (101) based at least in part on a comparison of the stored estimated characteristic curves with the reference characteristic curve defining the expected results of a non-corroded steering rack (101), wherein the corrosion status of the steering rack (101) is defined as a high corrosion status when an analytical representation of the values in the estimated characteristic curves does not indicate performance within a threshold value of the reference characteristic curve. [3] A corrosion detection system (100) operable to detect corrosion of a steering rack (101) of a vehicle, the system comprising: a rack position sensor (217, 117) operable to generate rack position data describing the current rack position of a pinion (103) associated with the steering rack (101); a rack force sensor (115, 215) operable to generate rack force data describing the force exerted on the pinion (103); a speed sensor (119, 219) operable to generate speed data describing the speed of movement of the vehicle; a corrosion level indicator (125); a processor (121) in data communication with the rack position sensor (217), the rack force sensor (115, 215), the speed sensor (119, 219) and the corrosion level indicator (125); and a data memory comprising instructions operable by the processor (121) which, when operated, cause the processor (121) to perform the following steps: detecting, from a rack position sensor (217, 117), first rack position data describing a first displacement of a pinion (103) of a vehicle with respect to an associated steering rack (101) of the vehicle; detecting, from a rack force sensor (115, 215), first rack force data describing a first force required to achieve the measured first displacement of the pinion (103); detecting, from a speed sensor (119, 219), first speed data describing a first speed of movement of the vehicle during the first displacement of the pinion (103); Generating a first estimated characteristic defined as the change in force divided by the change in displacement at the speed of movement; and Defining a corrosion status condition of the steering rack (101) based at least in part on a comparison of the estimated characteristic with a reference characteristic defining the expected results of a non-corroded steering rack (101), wherein the corrosion status condition of the steering rack (101) is defined as a high corrosion status if the estimated characteristic does not indicate performance within a threshold value of the reference characteristic, wherein the reference characteristic value is defined by one of the following: (a) a characteristic curve of relative rack force values versus rack position values corresponding to the behavior of a non-corroded steering rack (101) at a reference speed value, or (b) a lookup table of rack force values corresponding to rack position values at a reference speed value for a non-corroded steering rack (101). wherein the threshold value is defined by a characteristic curve of relative rack force values versus rack position values corresponding to the behavior of a non-corroded steering rack (101) at a reference speed value; further comprising instructions that, when executed by a processor (121), cause the processor (121) to perform a step of updating a data set of estimated curves stored in a curve data store that is in data communication with the processor (121); detecting, from the rack position sensor (217, 117), second rack position data describing a second displacement of the pinion (103) following the first displacement; detecting, from the rack force sensor (115, 215), second rack force data describing a second force required to achieve the measured second displacement of the pinion (103); detecting, from the speed sensor (119, 219), second speed data describing a second speed of movement of the vehicle during the second displacement of the pinion (103); Generating a second estimated characteristic defined as a second rack force data value divided by the second rack position data value at the second movement speed; Storing the generated second estimated characteristic curve in the curve data memory; and Updating the corrosion status of the steering rack (101) based at least in part on a comparison of the stored estimated characteristic curves with the reference characteristic curve defining the expected results of a non-corroded steering rack (101), wherein the corrosion status of the steering rack (101) is defined as a high corrosion status when an analytical representation of the values in the estimated characteristic curves does not indicate performance within a threshold value of the reference characteristic curve. [4] The corrosion detection system (100) of claim 3, wherein the processor (121) comprises an electronic control unit (ECU) of the vehicle. [5] The corrosion detection system (100) of claim 3, wherein the processor (121) comprises a diagnostic dongle operable to connect to a diagnostic port of the vehicle. [6] The corrosion detection system (100) of claim 3, wherein the processor (121) comprises a mobile device in wireless communication with the rack position sensor (217, 117), the rack force sensor (115, 215), and the speed sensor (119, 219). [7] The corrosion detection system (100) of claim 6, wherein the mobile device comprises a smartphone. [8] The corrosion detection system (100) of claim 6, wherein the rack force sensor (115, 215) comprises a torsion bar torque sensor. [9] The corrosion detection system (100) of claim 8, wherein the system further comprises a steering motor (116) operable to apply a second force to the rack and pinion, and wherein the processor (121) is operable to calculate the rack force data by summing the force measured by the torsion bar torque sensor and the second force from the steering motor (116). [10] The corrosion detection system (100) of claim 9, wherein the steering motor (116) comprises an electric steering motor (116).

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