Patent Publication Number: US-2022234598-A1

Title: High accuracy vehicle load managment

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the benefit of U.S. Provisional Application No. 63/199,754 filed on Jan. 22, 2021, in the U.S. Patent and Trademark Office, the entire content of which is herein incorporated by reference. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure relates to automotive vehicles and more particularly to a vehicle load calculation for an air suspension system of an automotive vehicle. 
     2. Description of Related Art 
     Suspension systems for automotive vehicles provide vehicle passengers with a more comfortable ride. Demand from vehicle owners for improved comfort, fuel economy, and more controls and options has led to the development of adjustable air suspension systems. Depending on the current driving surface, different suspension operating modes may be selected by the vehicle operator. The suspension operating modes have preset suspension parameters to provide the ideal suspension arrangement for various driving situations. Typical operating modes a driver may select include, a standard driving mode, such as a comfort or sport mode, a snow mode, an off-roading mode, etc. In addition to providing selected operating modes for various driving situations the suspension system may be adjusted when select operating conditions are met. 
     An air suspension system has four corner assemblies. One corner assembly is located at a suspension position corresponding to each of the wheel corners for the vehicle. An air supply unit including an electronic control unit is connected to the corner assemblies. The air supply unit is capable of independently adjusting the corner assemblies. A vehicle load calculation system comprises a plurality of height sensors each associated with a corner assembly to measure the current ride height and at least a pressure to measure the current pressure in each air spring. 
     For load detection the data of the pressure sensor and the several ride height sensors are used. The pressure sensor senses the air pressure in each air spring. The ride height sensors measure the current ride height at each corner assembly. The signals of those sensors are combined to determine the current vehicle load. 
     The vehicle load at the individual corner assemblies can be calculated based on the data from the pressure sensor and the plurality height sensors. The vehicle load at each corner is used to calculate at least one load dependent vehicle characteristic which can be used by a vehicle system to adjust at least one vehicle operating parameter to compensate for the at least one load dependent vehicle characteristic. 
     The accuracy of load detection is mainly limited by the fact, that only these signals are used the determine the current vehicle load. But the vehicle frame and more specific the corner assemblies are affected by other forces, which are not considered on determination of the vehicle load. 
     This results in limited accuracy of the load detection algorithm. The inaccurate detected vehicle load leads to false air pressure in the air springs. The air springs could become damaged in a case of high dynamic pressure during driving. Furthermore, an inaccurate vehicle load leads to false operations of dynamic vehicle stability control systems critical to vehicle safety. 
     The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
     SUMMARY 
     A vehicle load calculation system comprising an air suspension system having at least four corner assemblies, wherein one corner assembly is located at a suspension position corresponding to each of the wheel corners for the vehicle and the corner assemblies each comprising an air spring; wherein at least two of the corner assemblies are associated with a vehicle axle. An air supply unit, wherein the air supply unit is capable of independently adjusting the air springs from one another. A pressure sensor located at a valve block of the air supply unit, wherein the pressure sensor is capable of measuring the air pressure in each air spring. A plurality of height sensors, wherein one of the height sensors is located at the suspension position corresponding to each of the wheel corners for the vehicle, wherein each height sensor is capable of measuring a height for an associated corner assembly. An electronic control unit connected to the corner assemblies, wherein the electronic control unit includes instructions for calculating a vehicle load. A first vehicle load value is calculated based at least upon the data of the pressure sensor and a plurality of height sensors associated to the vehicle axle. A second vehicle load value is determined based on the change of track width of the vehicle axle. At least the second vehicle load value is subtracted from the first vehicle load value to calculate the vehicle load. 
     A method of calculation a vehicle load comprising measuring for one of a plurality of air pressures in a plurality of air springs, wherein each air spring is associated with a corner assembly located at a suspension position corresponding to each of the wheel corners for a vehicle. Measurement of a plurality of heights sensors at the suspension position corresponding to each of the wheel corners for the vehicle. Calculating a first vehicle load value with an electronic control unit based at least on the measured pressure and height data of a vehicle axle, wherein at least two of the corner assemblies are associated with the vehicle axle. Determining a second vehicle load value with the electronic control unit which is based on the change of track width of the vehicle axle. Calculating the vehicle load by at least subtracting the second vehicle load value from the first vehicle load value. 
     To compensate the inaccurate vehicle load determination an acting vertical force due to a change of track width of the first vehicle axle is considered in the load detection algorithm. Tension forces are acting on the suspension while the track width of the first axle is changed. Those forces are effective when the vehicle is for example lowered in a stationary state due to a change of load. This leads to a false vehicle load determination. 
     Due to the trajectory of a wheel there is a kinematic coloration between the track width and the change of height of the vehicle. If the vehicle is loaded the height lowers and the track width increases. By that an additional force is applied to the corner assemblies due to the change of track width. This force is acting in the opposite way compared to the load forces. 
     The vehicle load is determined by calculation the vehicle load based on the information of the pressure sensor and the plurality of height sensors, while the acting force based on the changed track width is subtracted. This leading to a more accurate vehicle load. A corrected vehicle load or a corrected axle load is calculated based on the pressure signal, the height signal and the acting forces due to changes of the track width. 
     The described calculation of a vehicle load is not limited to a single vehicle axle. This vehicle load calculation can be also performed on the other vehicle axle. Both calculated vehicle load values are then combined to an overall vehicle load. 
     Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the disclosure, are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a schematic illustration of an air suspension system according to an embodiment; 
         FIG. 2  is a pneumatic wiring diagram of the air suspension system shown in  FIG. 1 ; 
         FIGS. 3 a  and 3 b    are diagrams illustrating an exemplary change of track width; and 
         FIG. 4  is a flowchart of a method for calculating the vehicle load. 
     
    
    
     The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible. 
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. 
       FIG. 1  illustrates a vehicle  10 , in this instance a pickup truck. Vehicle  10  includes an air suspension system  12 . The air suspension system  12  is supported by a frame  14 . The air suspension system has four corner assemblies  16 A-D located at each of the wheel  18  locations of the vehicle  10 . The four corner assemblies  16 A-D may be independently adjustable. Two corner assemblies  16 A, B are located at the front wheel  18 A, B corners of the vehicle  10  and two corner assemblies  16 C, D are located at the rear wheel  18 C, D corners of the vehicle. The two corner assemblies  16 A, B are associated with a first axle of the vehicle  10  and the two corner assemblies  16 C, D are associated with a second axle of the vehicle  10 . 
     The air suspension system  12  includes an air supply unit  20  fluidly connected to the four corner assemblies  16 A-D. The air supply unit  20  includes an electronic control unit (ECU)  22 , a compressor  24 , a reservoir  26  and a valve block  30 . The individual components of the air supply unit  20  may be assembled together or supported on the vehicle  10  at separate locations. In the embodiment shown, the electronic control unit  22  is located remote from the compressor  24 , reservoir  26  and valve block  30  (electrical connections not shown). Alternatively, the air suspension system  12  may be an open loop system and the air supply unit  20  may not include a reservoir  26 . 
     The air supply unit  20  is connected to the four corner assemblies  16 A-D through the supply lines  28 . In the example shown, the air suspension system  12  is a closed system. The valve block  30  is controlled by the electronic control unit  22  to regulate the air supply between the compressor  24 , the reservoir  26  and the four corner assemblies  16 A-D. The valve block  30  may be a single unit defining multiple valves, multiple valves located together, or multiple valves at different locations. Additionally, the reservoir  26  may be a single or multiple tank assembly. 
     While the embodiment disclosed has four corner assemblies  16 A-D, the suspension system  12  may also be a system in which the front and rear axle are separately adjustable, and does not necessarily require separate adjustment at each of the corner assemblies  16 A-D. The four corner assemblies  16 A-D are adjustable to accommodate various driving conditions. Based upon the selected suspension mode the electronic control unit  22  will regulate the air supply between the compressor  24 , reservoir  26  and the four corner assemblies  16 A-D to adjust the four corner assemblies  16 A-D from the current positions to the desired positions. When lowering any of the corner assemblies  16 A-D the excess air is sent to the reservoir  26  for storage. When raising any of the corner assemblies  16 A-D the required air is sent from the reservoir  26  to the appropriate corner assembly  16 A-D. The compressor  24  ensures that the air pressure within the system  12  is maintained at the desired level. Alternately, in the instance of an open system the excess air is released to the environment or pulled from the environment and pressurized as needed. The compressor  24  ensures that the air pressure within the system  12  is maintained at the desired level. 
     The air suspension system  12  may be adjusted at the direction of the vehicle operator by moving a selector, or when pre-determined operating conditions exist, e.g. the vehicle  10  accelerates above a certain speed then the suspension system  12  is lowered, when the vehicle  10  decelerates below a predetermined threshold the suspension system  12  raised. Therefore, the air suspension system  12  may be adjusted while the vehicle  10  is in motion. In this instance, the front corner assemblies  16 A, B may be adjustable together and the rear corner assemblies  16 C, D may be adjustable together. To provide the most aerodynamic adjustment possible, when the vehicle is travelling in a forward direction, the rear corner assemblies are adjusted to the new position first when the suspension system  12  is raised. However, when the suspension system  12  is lowered, the front corner assemblies  16 A, B are adjusted to the new position first. Alternately, each corner  16 A-D could be adjusted separately, or all corners  16 A-D could be adjusted simultaneously. The air suspension system  12  may also be adjusted in a stationary state of the vehicle. The corner assemblies  16 A-D may be adjusted after the vehicle  10  have been loaded. For example, the vehicle  10  is then raised back to the normal ride height to compensate the loading. 
     Referring to  FIGS. 1 and 2 , the solenoid valve block  30  has four air spring valves, an exhaust valve and a pressure sensor  32 . The fluid lines  28  connect the reservoir  26  to the compressor  24 , e.g. the fluid line  28  is a 6×1 mm tube, the compressor  24  to the valve block  30 , e.g. the fluid line  28  is a 6×1.5 mm tube, and the valve block  30  to the air springs e.g. the fluid lines  28  are a 6×1.5 mm tube. The pressure sensor  32  may be proximate to or directly connected to the valve block  30 . 
     The solenoid valve block  30  is used to manage the air flow between the system components  16 A-D,  24 ,  26 . The signal from the pressure sensor  32  can be used to determine a vehicle load. The vehicle load information is then used by the electronic control unit  22  to help determine the desired adjustments for the air suspension system  12 , e.g. increasing height to accommodate for heavy vehicle load. 
     Therefore, a vehicle load calculation system comprises an air suspension unit  12  having four air spring corner assemblies  16 A-D. One air spring corner assembly  16 A-D is located at a suspension position corresponding to each of the wheel corners  18 A-D for the vehicle  10  and an air supply unit  20  including an electronic control unit  22  is fluidly connected  28  to the air spring corner assemblies  16 A-D. The air supply unit  20  is capable of independently adjusting the air spring corner assemblies  16 A-D from one another. 
     One method of determining a vehicle load for a vehicle  10  equipped with an air suspension system  12  comprises detecting a pressure signal from a sensor  32  located within a valve block  30  for the air suspension system  12 . The pressure sensor  30  determines the air pressure within each air spring. A vehicle load is calculated based at least on the pressure signal. 
     The method of determining the vehicle load comprises also signals from height sensors. Ride height sensors are associated with each corner assembly  16 A-D. Those sensors can gather information on the current height at each of the corner assemblies  16 A-D. Those sensors can gather information on the current height in stationary or moving state of the vehicle. 
     The detected information, including the height at each corner assembly  16 A-D and the air pressure in each air spring are reported to the electronic control unit  22 . The load calculation system uses the suspension electronic control unit  22  to calculate the vehicle load based at least on this information. The vehicle load at each corner assembly  16 A-D or at the front and back axle can be calculated based on this information. 
     Furthermore, the determined vehicle load is corrected by subtracting loads resulting out of track width bindings. The overall vehicle load is calculated by subtracting a load value based on the track width from another load value based on the pressure a height data. The load value based on the track width is a result of acting vertical forces which are applied to the axle while the vehicle is lowered or raised. These kinematical characteristics (wheel trajectory) could be measured in advance and applicated by vehicle test via levelling up and down with sliding plates. Height data points will be assigned to a track width. This leading to predetermined values for a vehicle load based on the changed track width. 
     Referring to  FIGS. 3 a  and 3 b    a change of track width of a vehicle axle is exemplary shown. In  FIG. 3 a    the vehicle is at standstill and for example in its lowest height h 0 . At this first height the track width  0  for example is 1610 mm. At this point the proposed method stores the current track width at the current height. This is followed by an up-level request. Therefore, as shown in  FIG. 3 b    the vehicle height is increased to a second height h 1 . For example, the vehicle was raised by 60 mm. At this height h 1  the track width  1  will be 1590 mm. Meaning the track width changed due to an up-level request from 1610 mm to 1590 mm. Thus, the change of track width is 20 mm. While the vehicle is raised the tires are pulled inwards. Due to the kinematical characteristics a vertical force is applied to the corner assemblies of that axle. The road friction results in a counter force acting on the tires indicated by the bold arrows showing outwards. 
     Due to the wheel trajectory this force is transitioned to the vertical force acting on the corner assemblies. This force distorts the correct calculation of the vehicle load. Therefore, a correction load value is determined. The proposed determination takes the change of track width into account. The changed track width value will be multiplied by a constant stiffness factor. This constant stiffness factor is predefined for the specific suspension characteristics of each vehicle. Furthermore, the current coefficient of road surface friction can be applied to the constant stiffness factor. By multiplying the changed track width value with the constant stiffness factor the vertical acting force on the corner assemblies is calculated. In order to calculate the correction load value, the vertical acting force is divided by the acceleration of gravity (9.81 m/s 2 ). This calculation leads to a correction load value which then can be subtracted from the standard vehicle load calculation. The standard vehicle load calculation is based on the air spring pressure and vehicle height. Thus, by taking the change of track width into account a more accurate calculation of vehicle load is performed. 
     The increased accuracy of the load detection can be used to more finely adjust the suspension system  12  based on the provided readings. In addition, the increased accuracy can be used to more closely monitor load (especially on the rear axle for a pick up) to prevent overload situations and provide a more robust measurement for failsafe operation in overload conditions. In fact, the overall high payload specification may even be increased due to the increased measurement accuracy that is available to the system because the load measurement is more accurate the design margin to protect against overloading situations can be smaller. 
     Referring to  FIG. 4  is a flowchart illustrating a method of determining a vehicle load. The method comprises the following steps. In step S 1  the vehicle speed decreases to 0 mph, so the vehicle is in a stationary state. In step S 2  the current track width for the current height is stored in the electronic control unit. 
     In step S 3  there is an uplevel request. Either by the driver or the autonomous vehicle itself. Thereafter the vehicle height is raised. In step S 4  a change of load of the vehicle takes place. Thus, i.e. the vehicle height is decreased. 
     In step S 5  a measurement of the air pressure and the current height is fulfilled. This leading in step S 6  to a calculation of a first vehicle load value load_m based upon the pressure and height measurement. 
     In step S 7  a second vehicle load value load_tw is determined by taking the track width at the current height into account. The track width of an axle applies a specific vertical force to the suspension at a specific height. Due to this kinematical characteristic a look-up table is provided containing specific load values for each type of vehicle. 
     Finally, in step S 8  the overall and accurate vehicle load can be calculated by subtracting the second vehicle load value from the first vehicle load value. 
     While embodiments have been described in detail the true scope of the disclosure should not be so limited, since those familiar with the art to which this disclosure relates will recognize various alternative designs and embodiments for practicing the concepts within the scope of the appended claims.