SYSTEM AND METHOD FOR DETECTING A DEFECT IN A GROUND CLEARANCE SENSOR

Abstract

Procedure, comprehensive: Generating samples from a ground clearance signal output by a ground clearance sensor (112) that detects the ground clearance of a vehicle; characterized by Determining the variance of the samples; and Detecting a defect in the ground clearance sensor (112) when the variance is less than a predetermined first value and when a vehicle speed is greater than a predetermined speed while the samples are generated from the ground clearance signal; where the predetermined first value increases with increasing vehicle speed.

Description

AREA

[0001] The present disclosure relates to vehicle suspensions and in particular to a method for detecting a defect in a ground clearance sensor according to the preamble of claim 1, as is known essentially from US 2007 10 129 865 A1.

[0002] Regarding the further state of the art, reference is made to US 4 718 695 A. BACKGROUND

[0003] Vehicle suspensions typically comprise springs, shock absorbers, and linkages that connect a vehicle's frame or body to its wheels. Suspension systems affect a vehicle's ride comfort and handling. Ride comfort and handling, in turn, influence safety, driving characteristics, and the protection of vehicle occupants from road noise, shocks, and vibrations.

[0004] An air suspension system is a type of vehicle suspension that typically includes air shock absorbers or air springs, an air pump or compressor (electrically or by an internal combustion engine), and a control valve that can be adjusted to release air from the air cushions. The compressor pressurizes the air in the air cushions, which then act as springs. The pressure in the air cushions can be controlled to improve ride comfort and / or to provide a self-leveling suspension. A self-leveling suspension maintains a desired ground clearance regardless of the load on the vehicle. Self-leveling suspensions may include a ground clearance sensor to control the vehicle's ground clearance using a closed-loop control system.

[0005] The invention is based on the objective of providing a method by which a defect in a ground clearance sensor can be detected particularly reliably. SUMMARY

[0006] This problem is solved by a method having the features of claim 1.

[0007] A system according to the principles of this disclosure comprises a variance determination module and a defect detection module. The variance determination module determines the variance of samples generated from a ground clearance signal. The ground clearance signal is output by a ground clearance sensor that detects the ground clearance of a vehicle. The defect detection module detects a defect in the ground clearance sensor based on the variance.

[0008] Further areas of applicability of the present disclosure will become apparent from the detailed description provided below. It is understood that the detailed description and specific examples are intended solely for illustrative purposes. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The present revelation becomes more easily understood with the help of the detailed description and accompanying drawings. These show: Fig. 1 partly a perspective view and partly a functional block diagram of an exemplary suspension system according to the principles of the present disclosure; Fig. 2 a functional block diagram of an exemplary suspension control system according to the principles of the present disclosure; and Fig. 3 and Fig. 4 flowcharts illustrating an exemplary suspension control procedure in accordance with the principles of the present disclosure. DETAILED DESCRIPTION

[0010] A suspension control system, including its associated procedures, can control a vehicle's ground clearance based on feedback received from a ground clearance sensor. The ground clearance sensor outputs an electrical voltage indicating the ground clearance. For example, the voltage can range from 0 volts (V) to 5 V, and at a desired ground clearance, the voltage might be around 2.5 V. A fault can be detected if the voltage falls outside a predetermined range (e.g., between 0.25 V and 4.75 V) after a predetermined number of samples. A fault, such as an open circuit or short circuit, can cause the voltage to remain outside the predetermined range.

[0011] In some cases, a defect can cause the electrical voltage output by the ground clearance sensor to remain stuck within its predetermined range. Detecting this type of defect can ensure that a vehicle maintains the desired ground clearance despite inaccuracies in the output voltage. However, this type of defect cannot be detected if a ground clearance sensor malfunction is only detected when the output voltage falls outside the predetermined range.

[0012] A suspension control system, including a method as disclosed herein, detects a defect in a ground clearance sensor based on the variance of a ground clearance signal, such as a voltage signal, output by the sensor. The ground clearance signal is expected to fluctuate by a certain amount due to suspension movement when a vehicle is in motion. A defect is detected if the ground clearance signal does not fluctuate as expected. Samples are generated from the ground clearance signal, and the variance of these samples is calculated. If the variance is less than a threshold and the vehicle speed is greater than a predetermined speed, a defect is detected.Detecting a defect based on the variance of the ground clearance signal ensures that a defect is detected regardless of whether the defect causes the ground clearance signal to become stuck outside or inside the predetermined range.

[0013] Corrective actions are taken when a fault is detected to maintain the vehicle at a desired ground clearance. If a vehicle has multiple ground clearance sensors, the corrective actions may include controlling a self-leveling suspension, such as air suspension, based on feedback from a ground clearance sensor that does not detect a fault. If a fault is detected in all ground clearance sensors, the corrective actions may include controlling the air suspension based on feedback from a pressure sensor that detects pressure in the air cushions within the air suspension. If a fault is also detected in the pressure sensor, the corrective actions may include holding a control valve open to release pressure from the air cushions.

[0014] With reference to Fig. 1 comprises a suspension system 100, an air pump or compressor 102, air cushions 104, air lines 106, a control valve 108, a pressure sensor 110, and ground clearance sensors 112. The compressor 102 can be operated to pressurize air in the air cushions 104. The compressor 102 can be electrically powered or driven by the internal combustion engine. The air cushions 104 can be contained in air dampers or air springs. Although the suspension system 100 is presented as an air suspension, a suspension control system and method according to the principles of this disclosure are transferable to other types of suspension.

[0015] The air lines 106 run between the compressor 102 and the air cushions 104. The control valve 108 can be adjusted to release air from the air cushions 104. The pressure sensor 110 outputs an air pressure signal (APS) 114, which indicates the pressure in the air cushions 104. The control valve 108 and the pressure sensor 110 can be located in the compressor 102, the air cushions 104, and / or the air lines 106.

[0016] The ground clearance sensors 112 output a ground clearance (RHS) signal 116, which indicates the ground clearance of a vehicle. The ground clearance sensors 112 each comprise a sensor body 118 and a sensor arm 120. The sensor body 118 can be mounted on a frame or body, and the sensor arm 120 can be attached to a suspension component such as a linkage.

[0017] The sensor body 118 accommodates a sensor that detects the absolute position of the sensor arm 120 relative to the sensor body 118 and / or a movement of the sensor arm 120 relative to the sensor body 118. The sensor can be an inductive sensor (e.g., an anisotropic magnetic resistance sensor), an optical sensor, or a Hall effect sensor. Although the suspension system 100 is shown comprising two ground clearance sensors, the suspension system 100 can include more or fewer ground clearance sensors.

[0018] A control module 122 controls the suspension system 100 to maintain the desired ground clearance of the vehicle despite changes in the load. The control module 122 adjusts the pressure in the air cushions 104 to adjust the ground clearance. The control module 122 controls the compressor 102 and the control valve 108 to adjust the pressure in the air cushions 104. The control module 122 outputs a compressor control signal (CCS) 124 to control the compressor 102. The control module 122 outputs a valve control signal (VCS) 126 to control the control valve 108.

[0019] The control module 122 adjusts the ground clearance based on an input received from the pressure sensor 110 and / or the ground clearance sensors 112. The control module 122 detects a fault in the ground clearance sensors 112 based on an input received from the pressure sensor 110, the ground clearance sensors 112, and / or a vehicle speed sensor 128, as described below. The vehicle speed sensor 128 outputs a vehicle speed signal (VSS) 130, which indicates a vehicle speed. The control module 122 takes corrective action when a fault is detected in the pressure sensor 110 and / or the ground clearance sensors 112, as described below.

[0020] With reference to Fig. Figure 2 comprises an exemplary implementation of the control module 122, a signal sampling module 202, a variance determination module 204, a defect detection module 206, and a ground clearance control module 208. The signal sampling module 202 generates samples from the ground clearance signal 116 and outputs the generated samples. The signal sampling module 202 can sample the ground clearance signal 116 at a predetermined sampling rate. The signal sampling module 202 can generate a number of samples from the ground clearance signal 116 before outputting the generated samples. The number can be predetermined and / or can vary based on the sampling rate used to generate the samples.

[0021] The variance calculation module 204 determines the variance of samples generated from the ground clearance signal 116. The number of samples used to determine the variance can be predetermined and / or can vary based on the sampling rate used to generate the samples. The variance calculation module 204 can determine the mean (AVG) and the variance (V) of N samples (X). 1-N ) using the following equations: V(X1−N)=∑(X1−N−AVG)2 / N; and AVG=∑(X1−N) / N.

[0022] The variance calculation module 204 outputs the variance.

[0023] The defect detection module 206 detects a defect in one of the ground clearance sensors 112, which outputs the ground clearance signal 116 from which the samples are generated, based on the variance of the ground clearance signal 116.

[0024] The defect detection module 206 can detect a defect if the variance of the ground clearance signal 116 is smaller than a first value (e.g. 0.004 millimeters). 2 ) and the vehicle speed indicated by the vehicle speed signal 130 is greater than a first speed (e.g., 10 kilometers per hour (km / h)). The first value and the first speed can be predetermined by calibration through driving a vehicle at low speeds (e.g., between 1 km / h and 10 km / h) on a smooth surface where almost no suspension movement is expected. The first value increases as the vehicle speed increases, and the first value decreases as the vehicle speed decreases.

[0025] The fault detection module 206 can detect a fault in the pressure sensor 110 based on the air pressure signal 114. The air pressure signal 114 can be a voltage signal ranging from 0 V to 5 V. The fault detection module 206 can detect a fault in the pressure sensor 110 if the air pressure signal 114 lies outside a predetermined range (e.g., between 0.25 V and 4.75 V) after a predetermined number of samples (e.g., 80 out of 100). The fault detection module 206 outputs a signal indicating whether a fault has been detected in the pressure sensor 110 or the ground clearance sensors 112.

[0026] The ground clearance control module 208 controls the vehicle's ground clearance based on the ground clearance signal 116. The ground clearance control module 208 can control the ground clearance to minimize the difference between the actual ground clearance indicated by the ground clearance signal 116 and the desired ground clearance. The ground clearance control module 208 can control the ground clearance by adjusting the operation of the compressor 102 via the compressor control signal 124. Additionally or alternatively, the ground clearance control module 208 can control the ground clearance by adjusting the control valve 108 via the valve control signal 126.

[0027] The ground clearance control module 208 can control the ground clearance based on an input received from either of the two ground clearance sensors 112 if a fault is detected in either sensor. For example, the ground clearance sensors 112 can be located on opposite sides of the vehicle, and the ground clearance control module 208 can control the ground clearance on each side based on an input received from the corresponding sensor. The ground clearance control module 208 can also control the vehicle's ground clearance (e.g., on both sides) based on an input received from only one of the ground clearance sensors 112 if a fault is detected in the other sensor.

[0028] Based on the air pressure signal 114, the ground clearance control module 208 can deactivate the compressor 102 and / or control the vehicle's ground clearance if, for example, a fault is detected in both ground clearance sensors 112. The ground clearance control module 208 can control the ground clearance by adjusting the control valve 108 to minimize the difference between the actual air pressure indicated by the air pressure signal 114 and a desired air pressure. The desired air pressure can be preset to achieve a specific ground clearance. The ground clearance control module 208 can keep the control valve 108 open to reduce the pressure of the air cushions 104 if a fault is detected in the pressure sensor 110 and in both ground clearance sensors 112.

[0029] With reference to Fig. Paragraph 3 employs a method for controlling a suspension system at 302. The method is applicable to air suspension and other types of suspension. The suspension system includes a ground clearance sensor that outputs a ground clearance signal indicating the ground clearance of a vehicle. At 304, the method samples the ground clearance signal.

[0030] At 306, the procedure determines a variance of the ground clearance signal. The number of samples for which the variance is determined can be predetermined and / or can vary based on a sampling rate at which the samples are generated. The procedure can determine the variance using equations (1) and (2) described above.

[0031] In case 308, the procedure determines whether the variance is smaller than a first value (e.g., 0.004 millimeters). 2The first value can be predetermined by calibration through driving a vehicle at a low speed (e.g., 3 km / h) on a smooth surface where virtually no suspension movement is expected. If the variance is smaller than the first value, the procedure continues at 310. Otherwise, the procedure continues at 304.

[0032] At step 310, the procedure determines whether a vehicle speed is greater than a first speed (e.g., 10 km / h). If the vehicle speed is greater than the first speed, the procedure continues at step 312. Otherwise, the procedure continues at step 304. The procedure can also determine whether a fault is detected in a vehicle speed sensor that measures the vehicle speed. If condition 310 is met and no fault is detected in the vehicle speed sensor, the procedure can continue at step 312. Otherwise, the procedure can continue at step 304.

[0033] In case 312, the method detects a defect in the ground clearance sensor. Even if the variance is smaller than the first value, the method thus does not detect a defect in the ground clearance sensor if the vehicle speed is less than or equal to the first speed. Additionally or alternatively, the method may not sample the ground clearance signal or determine a variance if the vehicle speed is less than or equal to the first speed. In case 314, the method takes a corrective action. The method can be described with reference to Fig. 4. Take remedial action by carrying out one or more of the steps described below.

[0034] With reference to Fig. At step 402, the procedure determines whether a defect is detected in all ground clearance sensors on the vehicle. If no defect is detected in any of the ground clearance sensors, the procedure continues at step 404. Otherwise, the procedure continues at step 406. At step 404, the procedure controls the ground clearance based on an input received from one or more ground clearance sensors in which no defect is detected. At step 406, the procedure deactivates a compressor that pressurizes the air in the suspension system (e.g., the air cushions).

[0035] In procedure 408, the method determines whether a fault is detected in one or more pressure sensors that measure pressure in the suspension system. The method can identify a defect in the pressure sensor(s) with reference to Fig.2 detect in the manner described above. If no defect is detected in the pressure sensor(s), the procedure continues at 410. Otherwise, the procedure continues at 412. The procedure may refrain from deactivating the compressor until a defect is detected in the pressure sensor and in all ground clearance sensors. At 412, the procedure holds open a control valve that releases air from the suspension system (e.g., from its air cushions).

[0036] As used herein, the term module may refer to, or be part of, an application-specific integrated circuit (ASIC); an electronic circuit; a combinational logic circuit; a field-programmable gate array (FPGA); a processor (shared, dedicated, or group) that executes code; other suitable hardware components that provide the described functionality; or a combination of some or all of the foregoing, such as a system-on-a-chip. The term module may also include memory (shared, dedicated, or group) that stores code executed by the processor.

[0037] The term "code," as used above, can include software, firmware, and / or microcode, and can refer to programs, routines, functions, classes, and / or tasks. The term "shared," as used above, means that some or all of the code from multiple modules can be executed using a single (shared) processor. Furthermore, some or all of the code from multiple modules can be stored in a single (shared) memory. The term "group," as used above, means that some or all of the code from a single module can be executed using a group of processors. Furthermore, some or all of the code from a single module can be stored using a group of memories.

[0038] The devices and methods described herein can be implemented by one or more computer programs executed by one or more processors. The computer programs comprise instructions executable by a processor, stored on a non-volatile, tangible, machine-readable medium. The computer programs may also include stored data. Non-restrictive examples of the non-volatile, tangible, machine-readable medium are permanent storage, magnetic storage, and optical storage.

Claims

[1] Procedure, encompassing: Generating samples from a ground clearance signal output by a ground clearance sensor (112) that detects the ground clearance of a vehicle; characterized by Determining the variance of the samples; and Detecting a defect in the ground clearance sensor (112) when the variance is less than a predetermined first value and when a vehicle speed is greater than a predetermined speed while the samples are generated from the ground clearance signal; where the predetermined first value increases with increasing vehicle speed. [2] Method according to claim 1, which further comprises controlling the ground clearance by controlling at least one of a compressor (102) pressurizing air in an air suspension (104) and a valve (108) releasing air from the air suspension (104). [3] Method according to claim 2, wherein the ground clearance sensor (112) comprises several sensors (112), wherein the method further comprises controlling the ground clearance based on an input from at least one of the sensors (112) when no defect is detected in the at least one of the sensors (112). [4] Method according to claim 3, which further comprises terminating the control of the ground clearance based on an input from the at least one of the sensors (112) when a defect is detected in the at least one of the sensors (112). [5] Method according to claim 2, which further comprises deactivating the compressor (102) when a defect is detected in the ground clearance sensor (112). [6] Method according to claim 2, which further comprises controlling the ground clearance based on an input received from a pressure sensor (110) when a defect is detected in the ground clearance sensor (112), wherein the pressure sensor (110) detects pressure in the air suspension (104). [7] Method according to claim 6, which further comprises holding the valve (108) in an open position when a defect is detected in the pressure sensor (110).

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