WO2008067392A2

WO2008067392A2 - Load sensor and method of sensing a load

Info

Publication number: WO2008067392A2
Application number: PCT/US2007/085780
Authority: WO
Inventors: Mark A. Joki
Original assignee: Timken Co
Current assignee: Timken Co
Priority date: 2006-11-28
Filing date: 2007-11-28
Publication date: 2008-06-05
Anticipated expiration: 2009-05-28
Also published as: WO2008067392A3

Abstract

A load sensor device (52) for measuring wheel contact loads applied to a suspension system (10) of the vehicle. The load sensor (52) comprises a resilient member (74) operatively connected to the suspension system (10) and to a housing (72). A circuit board (78) attaches to the suspension system (10) and the housing (72), wherein the circuit board (78) has sensors (92) attached thereon. The sensors (92) measure movements of the circuit board (78) that are created in response to the wheel loads applied through the resilient member (74).

Description

LOAD SENSOR AND METHOD OF SENSING A LOAD

CROSS REFERENCE TO RELATED APPLICATIONS

This application derives and claims priority from U.S. provisional application having Serial No. 60/867,535 filed November 28, 2006, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

This disclosure relates in general to monitoring road forces and loads applied to automotive vehicles. In one application, the present disclosure relates to monitoring loads applied to a suspension system of a vehicle. BACKGROUND ART

In many current automotive vehicles, particularly automobiles and light trucks, the road wheels couple to the suspension system of such vehicles through hub-bearing assemblies, often referred to as "wheel ends" which are supplied as preassembled units. The preassembled units reduce the time required to assemble the vehicles and further improve the quality of the vehicles by eliminating critical adjustments from the assembly line. Additionally, these preassembled units are suitable for high volume production. Struts of a suspension system represent one type of these preassembled units that have facilitated the assembly of automotive vehicles.

A typical wheel end of an automotive vehicle includes a housing that is bolted against a steering knuckle or other suspension upright at three or four locations, normally with machine bolts that pass through the suspension system and thread into the housing. These bolts secure the entire wheel end to the suspension system. The suspension system may comprise a strut having a spring and damper which transfer loads to the housing. The housing includes a hub provided with a flange to which the road wheel is attached, wherein a hub spindle projects from the flange into the housing. An antifriction bearing located between the housing and the hub spindle enables the hub to rotate in the housing with minimal friction.

Acquiring information about the loads applied to the road enhances the ability of a vehicle control system to manage drive train power, braking, steering and suspension system components. In particular, the forces exerted on any wheel of the automotive vehicle, particularly on the front wheels, if known, can be employed to enhance safety. Electrical signals representing wheel force can provide electronic braking and power train controls with information about vehicle loading and road conditions, enabling those controls to conform the operation of the vehicle to best accommodate the wheel loads.

It is often difficult for a driver to detect reduced levels of friction of the vehicle's tires on a roadway surface caused by ice formation or hydroplaning until loss of control occurs. Early warning of such a dangerous condition would enhance safety. Measurement of the wheel end loads (radial, lateral, and longitudinal) would be useful for vehicle stability control systems used to protect against loss of vehicle control. By knowing the instantaneous loading condition at each wheel, the onset of potential roll-over or spin-out can be detected and prevented by engine throttling and/or brake application of selected road wheel(s). The present disclosure provides a cost effective method of providing wheel force information suitable for high volume production. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a simplified perspective view of a wheel end connected to a road wheel and a suspension system of a vehicle

Figure 2 is a longitudinal sectional view of the wheel end, a housing of which is fastened to the suspension system;

Figure 3 is a partial cross sectional view of the suspension system illustrating a load sensor having a circuit board that includes sensors operatively connected thereon in accordance with an embodiment of the present disclosure; Figure 4 is a plan view of the circuit board of Figure 3 illustrating radial members and transverse areas of the circuit board;

Figure 5 is a partial view of the circuit board illustrating sensors located at sensor locations that are positioned on the radial members and transverse areas of Figure 4;

Figure 6 is a partial detail view of a sensor of Figure 5 in the form of a circuit trace;

Figure 7 is an electrical schematic of vertical load sensing connections of the sensors of Figure 5; and Figure 8 is an electrical schematic of radial load sensing connections of the sensors of Figure 5.

Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings. DETAILED DESCRIPTION OF THE INVENTION The following detailed description illustrates the invention by way of example and not by way of limitation. The description clearly enables one skilled in the art to make and use the invention, describes several embodiments, adaptations, variations, alternatives, and uses of the invention, including what is presently believed to be the best mode of carrying out the invention.

The present disclosure resides in a device for sensing applied loads in a vehicle. The disclosure can be used in any appropriate load sensor application, however, for illustrative purposes, the disclosure will be described as incorporated with a vehicle strut. The present disclosure describes a unique package that facilitates load sensing and reduces the complex assembly methods needed to create complex structures heretofore considered for sensing loads at wheel ends.

Referring to the drawings, a wheel end generally shown as A, which is in essence a bearing assembly, couples a road wheel R to a suspension system generally shown as 10 of an automotive vehicle (Fig. 1 ). The wheel end A enables the road wheel R to rotate about an axis and to transfer both - A -

radial loads and thrust loads in both axial directions between the road wheel R and the suspension system 10. The suspension system 10 may be used with a steerable wheel end A and may be used with a non- steerable wheel end A. Turning to Figure 2, the wheel end A includes a housing 12 that is bolted to the suspension system 10, a hub 14 to which the road wheel R is attached, and an antifriction bearing generally shown as 16 located between the housing 12 and hub 14 to enable the latter to rotate with respect to the former about an axis "X" of rotation with minimal friction. In one aspect of the disclosure, the antifriction bearing 16 senses wheel loads applied by the road wheel R to the suspension system 10 of the vehicle. The antifriction bearing 16 supports a shaft (not shown) connected to the road wheel R and provides the axis "X" of rotation about which the road wheel R can rotate. The housing 12 includes a generally cylindrical body 18, which is tubular, and ears 20 that project radially from the body 18 generally midway between the ends of the body 18. The inboard segment of the body 18 is received snugly in the suspension system 10 wherein the wheel end A is attached to the suspension upright at flange 22 of the housing 12. The hub 14 includes a spindle 24, which extends through the body

18 of the housing 12, and a flange 26 that is formed integral with the spindle 24 at the outboard end of the spindle 24. The flange 26 is fitted with lug bolts 28 over which lug nuts 30 thread to secure the road wheel R to the hub 14. The spindle 24 merges with the hub flange 26 at an enlarged region that leads out to a cylindrical bearing seat that in turn forms a formed end 32. The formed end 32 is directed outwardly away from the axis "X" of rotation and provides an inside face that is squared off with respect to the axis "X" of rotation and is presented toward the enlarged region. Initially, the flange hub 26 does not have the formed end 32 at the inboard end of the spindle 24. Instead, the flange hub 26 is manufactured with a deformable end that forms the extension of the bearing seat.

The bearing 16 lies between the spindle 24 of the hub 14 and the housing 12 and enables the hub 14 to rotate relative to the housing 12 about the axis "X". The antifriction bearing 16 is configured to transfer radial loads between the housing 12 and hub 14 and also thrust loads in both axial directions. The antifriction bearing 16 comprises an outer race 34 having first and second outer raceways 36, 38 presented inwardly toward the axis "X" of rotation. As shown, the outer race 34 may be part of the housing 12. The two tapered outer raceways 36 and 38 form on the interior surface of the body 18 for the housing 12, the former being outboard and the latter being inboard. The two raceways 36 and 38 taper downwardly toward each other so that they have their least diameters where they are closest, generally midway between the ends of the housing 12.

The antifriction bearing 16 also comprises an inner race 40 having first and second inner raceways 42, 44 carried by the shaft, the first inner raceway 42 being presented toward the first outer raceway 36 and inclined in the same direction as that raceway 36, the second inner raceway 44 being presented toward the second outer raceway 38 and inclined in the same direction as that raceway 38. The inner raceway 42 lies at the outboard position and faces the outboard outer raceway 36, tapering in the same direction downwardly toward the center of the housing 12. The second inner raceway 44 presents outwardly toward the inboard outer raceway 38 on the housing 12 and tapers in the same direction, downwardly toward the middle of the housing 12.

Completing the bearing 16 are rolling elements in the form of tapered rollers 46 organized in two rows, one set located between and contacting the outboard raceways 36 and 42 and the other set located between and contacting the inboard raceways 38 and 44. The rollers 46 of each row are on an apex. The taper of the rollers 46 and raceways is such that there is pure rolling contact between the rollers 46 and the raceways 36, 38, 42 and 44. The rollers 46 of each row are separated by a cage 48 that maintains the proper spacing between the rollers 46 and further retains them in place around their respective raceways in the absence of the housing 12. The rollers 46 transmit thrust and radial loads between the raceways, while reducing friction to a minimum.

Turning to Figure 3, the suspension system 10 comprises a strut, such as a McPherson strut, generally shown as 50 and a load sensor generally shown as 52. The strut 50 and load sensor 52 can be of any size, shape and material composition to accommodate vehicles of any size. The strut 50 comprises a spring 54, a damper 56 and a spring plate 58. The spring 54 and the damper 56 transfer wheel loads to vehicle structure 60. Any load transfer device that can be employed to receive and to transfer applied loads is intended to be within the scope of the disclosure. The spring plate 58 operatively connects the spring 54 and damper 56 combination to antifriction bearing generally shown as 62.

Spring loads, as received from the spring 54 and applied through the spring plate 58 and damper 56, transfer the applied loads to the bearing 62. The bearing 62 includes a fixed race 64 (i.e., non-movable) and a moveable race 66. The bearing 62 also includes rolling elements in the form of balls 68 located between and contacting the fixed race 64 and the moveable race 66. As shown, a cylinder 70 of the suspension system 10 supports the fixed race 64 while the spring plate 58 contacts the moveable race 66. A housing 72, through a resilient member 74, supports the cylinder 70 axially and radially. In one aspect, the resilient member 74 comprises a molded elastomer or elastomeric material. The resilient materials are representative of an embodiment and are not intended to limit the scope of the disclosure. A nut and washer combination 76 of the suspension system 10 sets the position of the moveable race 64. The load sensor 52 comprises a planar element in the form of a disk shaped circuit board 78. The circuit board 78 is disposed coaxially about the cylinder 70. The load sensor 52 can have a variety of shapes beyond the disk shape. As shown, a retainer 80 fixes the circuit board 78 to the cylinder 70. The retainer 80 is secured to the cylinder 70, preferably by press fitting. Optimally, the circuit board 78 contains electronic circuitry for a variety of parameters such as signal amplification, temperature compensation, calibration adjustments, cross axis rejection, power conditioning and excitation, and/or wired or wireless communications.

Fasteners 82 such as rivets attach the circuit board 78 to the housing 72. A portion of the circuit board 78 freely suspends between the retainer 80 and the fastener 82. As shown in Figure 3, a cover 84 seals the circuit board 78 against environmental effects. Cable 86 passes through the cover 84 to connect the circuit board 78 with a vehicle control system generally shown as "VCS", such that the circuit board 78 operatively communicates with the vehicle control system VCS via the cable 86. Optimally, the vehicle control system VCS controls braking, power train torque, steering, and/or suspension stiffness or damping based on signals received from the circuit board 78. In one aspect, the vehicle control system VCS comprises a programmable memory that is in operative communication with the circuit board 78. Turning to Figure 4, the circuit board 78 includes strain sensitive zones generally shown as 88. Each strain sensitive zone 88 includes sensor locations 90 (Fig. 5) which position sensors 92 near or within the strain sensitive zones 88. The sensors 92 operatively connect with the circuit board 78. As will be discussed, the sensors 92 monitor and communicate vertical loads and radial loads applied by the road wheel R to the suspension system 10 and transferred to the circuit board 78 via the resilient member 74 and the cylinder 70. The sensors 92 optimally include any deflection-based sensors, such as strain gauges, piezoelectric elements, micro-electro-mechanic system devices or printed circuit traces. The sensors 92, however, can be construed in any acceptable manner and any acceptable number that allows for sensing and communicating loads and strains.

The circuit board 78 optimally includes an outer ring portion 94, an inner ring portion 96 and radial members 98 (webs) that connect the outer ring portion 94 and the inner ring portion 96 (Figure 5). In one embodiment, the inner ring portion 96 forms a disk shaped center 100 of the circuit board 78. Each radial member 98 has a proximal end 102 and a distal end 104 as measured from the inner ring portion 96. The proximal end 102 and the distal end 104 form corners 106 at the junction of the inner ring portion 96 and outer ring portion 94 respectively. As shown in the Figure 4, the outer ring portion 94, the inner ring portion 96 and the radial members delimit apertures 108 defined through the circuit board 78.

The outer ring portion 94 includes a plurality of elongated slots 110 defined through the circuit board 78. Each slot includes a first end 112 and a second end 114. Optimally, the slots 110 are positioned through the outer ring portion 94 at a substantially perpendicular orientation with respect to the distal ends 104 of the radial members 98. The slots 110 and the radial members define therebetween transverse areas 116 (tangential webs) of the outer ring portion 94. The circuit board 78 optimally includes four radial members 98 and four transverse areas 116. The number of radial members 98 and transverse areas 116 are representative of an embodiment and are not intended to limit the scope. When acted upon by the wheel loads, the radial members 98 flex to allow motion of the disk shaped center 100 of the circuit board 78 to move in the plane of the circuit board 78 and perpendicular to the radial members 98 as well as to move out of plane with respect to the circuit board 78. When acted upon by the wheel loads, the transverse areas 116 flex to allow motion of the disk center 100 parallel to the radial members 98. Figure 5 illustrates sensor locations 90 for one of the load sensitive zones 88 of the circuit board 78. Sensor locations 90 labeled A_L, A_R, B_L and BR are positioned near the corners 106 formed by the radial member 98 and the outer ring portion 94. The sensor locations labeled D_L and D_R are positioned near the transverse area 116 near the first end 112 and second end 114 respectively of the slot. The sensor locations labels C_L and C_R are positioned near the transverse areas 116 near the middle of the slot 110. Sensor locations labeled E_L and E_R are positioned near ends of the transverse area 116. Sensors 92 are generally shown operatively connected to the circuit board 78. Interconnect traces 93 connect the sensor locations and respective sensors 92. Optimally, the interconnect traces are positioned parallel with the sensing locations. The interconnect traces 93 are preferably located near the center axis of the radial members 88 and the transverse areas 116 to minimize sensitivity of the circuit traces 93. In one embodiment shown in Figure 6, the sensors 92 comprise printed circuit traces operatively connected to the circuit board 78. The positions of the sensor locations A_L, A_R, B_L, B_R, C_L, CR, D_L, D_R, E_L, and E_R are representative of an embodiment and are not intended to limit the scope of the present disclosure.

The sensors 92 positioned at locations A_L, A_R, B_L, B_R, C_L, C_R, D_L, DR, EL, and E_R measure strains of the circuit board 78 caused by vertical loads and radial loads applied by the road wheel R by measuring both in plane and out of plane movement of the radial members 98 and the disk shaped center 100 as the suspension system 10 experiences applied loads when the road wheel R traverses the surface In response the movements of the radial members 88 and the disk shaped center 100, the sensors 92 positioned at locations A_L, A_R, B_L, B_R, C_L, C_R| D_L, D_R, E_L, and E_R produce electrical signals that represent the measured loads. The sensor 92 communicate the measured loads to the vehicle control system VCS. The vehicle control system VCS converts the electrical signals representing the measured movements of the circuit board into resolved load values so that the vehicle control system VCS measures driving parameters. Referring to Figure 5 and turning to Figure 7, in one aspect, sensors 92 positioned at locations AL, A_R and B_L, B_R on the radial members 98 connect in a wheatstone bridge configuration. This connection maximizes the response to vertical loads applied by the road wheel R, rejects common mode effects such as thermal resistance change, and rejects effects due to radial deflections. The output of the sensors 92, represented by the meter 118 in the diagram, is amplified and transferred to the vehicle control system VCS over the cable 86.

Referring to Figure 4 and turning to Figure 8, radial members 98 located 180° opposite from each other form a pair. Each pair is aligned with one orthogonal direction of the road wheel loads, i.e., lateral and longitudinal loads. The sensors 92 connect in the arrangement shown in Figure 8, with the sensors having separate outputs to the vehicle control system VCS. This connection maximizes the response to loads in the desired direction, rejects common mode effects and rejects cross axis deflections. The output of the sensors 92, represented by the meter 120 in the diagram, is amplified and transferred to the vehicle control system VCS over the cable 86.

In another embodiment, the resilient member 74 (Fig. 3) includes sensors 122 operatively connected thereon and/or embedded therein. The suspension system 10 transfers the wheel loads to the resilient member 74 such that the resilient member 74 is configured to move in response to the transferred wheel loads wherein the sensors 122 are configured to measure the strains of the resilient member 74 caused by the movements of the resilient member 74. The strain loads of the resilient member 74 are resolved into at least two independent degrees of freedom, i.e., the lateral and radial loads applied by the road wheel R. The sensors 122 then communicate the loads applied by the road wheel R to the vehicle control system VCS. In one aspect of the present disclosure, the sensors 122 of the resilient member 74 are used in conjunction with the sensors 92 of the circuit board 78. During one embodiment of operation, the road wheels R experience forces or loads as the road wheels R move across a surface. The strut 50 transfers the loads to the vehicle structure 60 through the resilient member 74. In particular, the spring 54 receives the loads and applies the loads to the bearing 62 through the spring plate 58 and the damper 56. The bearing 62 transfers the loads to the cylinder 70, the housing 72 and the resilient member 74. The resilient member 74 retracts and expands as the resilient member 74 experiences the transferred loads from the bearing 62. The cylinder 70 in response to the retractions and the expansions of the resilient member 74 moves the circuit board 78. In one aspect, the cylinder 70 flexes the circuit board 78 since the circuit board 78 suspends between the housing 72 and the cylinder 70.

When acted upon by loads, the radial members 98 flex to allow motion of the disk shaped center 100 of the circuit board 78 to move in the plane of the circuit board 78 and perpendicular to the radial members 98 as well move as out of plane with respect to the circuit board 78. The transverse areas 116 flex to allow motion of the disk center 100 parallel to the radial members 98.

The sensors 92 measure both in plane and out of plane movements of the radial members 98, the disk shaped center 100 and the transverse areas 116 as the suspension system 10 experiences applied loads when the road wheel R traverses the surface. The sensors 92 respond to both vertical loads and radial loads as reflected by the movement of the circuit board 78. In one embodiment, the sensors 92 connected to the radial members 98 will measure vertical loads while sensors 92 connected to the transverse areas 90 will measure radial loads.

The sensors 92 measure strains of the circuit board 78 caused by the movements of the circuit board 78. The sensors 92 produce electrical signals that represent the measured loads to which the respective sensors 92 are attached. The sensors 92 communicate the measured loads to the vehicle control system VCS to measure driving parameters. In response, the vehicle control system VCS controls braking, power train torque, steering, and/or suspension stiffness or damping based on signals received from the sensors 92.

In another embodiment of operation, the wheel loads are transferred from the suspension system 10 to the resilient member 74 which moves in response to the transferred wheel loads. The sensors 122, associated with the resilient member 74, measure strains of the resilient member 74 caused by movement of the resilient member 74 in response to the loads transferred to the resilient member 74. The measured strains of the resilient member 74 are resolved into load values of at least two independent degrees of freedom. The sensors 122 communicate the measured loads of the resilient member 74 to the vehicle control system VCS to measure driving parameters.

The materials for the circuit board 78 and sensors 92, 122 may comprise a plurality of materials that can be formed by any acceptable composition or manner that allows for sensing loads and strains. Optimally, the measurements from the load sensor 52 are compared with other vehicle sensors (not shown) over periods of time and corrections will be made to the calibration of the sensor 92, 122. In one embodiment, the measured lateral forces are compared with measured lateral accelerations and lateral accelerations computed from steering angles and vehicle speed to determine corrections to the measured lateral forces. The measured longitudinal forces are compared against brake actuation forces, drive train power, and vehicle longitudinal acceleration/deceleration to determine corrections to the measured longitudinal forces. Additionally, the measured vertical forces are compared against long term observations. Further, in one embodiment, periods of unloaded operation are identified with historical data to compare against the known vehicle weight. The long term comparison of front/rear load transfer during braking and side/side load transfer during cornering can also be used as reference for vertical load recalibration by the vehicle control system VCS. ^[n the embodiments shown, the present disclosure provides the resilient member 74, circuit board 78 and associated sensors 92, 122 of the load sensor device 52, which are robust against environmental effects such as corrosion and are easily serviceable. The mounting surface for the circuit board 78 is protected from the environment and not subjected to corrosion or other environmental effects. The disclosure provides various means for attaching the sensor circuit board 78 to the cylinder 70, means for sealing the mounting surface and means for monitoring and communicating the applied loads. The load sensor device 52 of the present disclosure may be used for a variety of sensor technologies. For illustrative purposes, the load sensor device 52 is shown with a McPherson strut wherein the load sensor device 52 may be used with all strut assemblies. Additionally, the load sensor device 52 of the present disclosure has utility beyond vehicle control systems. Indeed, the load sensor device 52 may be used in any housing that experiences, transfers or receives loads.

Those of ordinary skill in the art will recognize that any strain, displacement, rotation, or temperature sensor technology can be utilized within the scope of the present disclosure to acquire necessary measurements. For example, strain sensors such as, but not limited to, resistive, optical sensors, capacitive sensors, inductive sensors, piezoresistive, magnetostrictive, MEMS, vibrating wire, piezoelectric, and acoustic sensors, printed circuit traces are suitable and may be used within the scope of the disclosure. As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Claims

1. A load sensor positioned in a housing of a vehicle that is configured to sense wheel loads applied to a suspension system of the vehicle, the load sensor comprising: a resilient member operatively connected between the housing and the suspension system; and sensors operatively connected to the resilient member wherein the suspension system is configured to transfer the wheel loads to the resilient member such that the resilient member is configured to move in response to the transferred wheel loads wherein the sensors are configured to measure strains of the resilient member caused by the movements of the resilient member.

2. The load sensor of claim 1 further comprising an annular circuit board disposed co-axially about a cylinder of the suspension system and attached to the housing, the circuit board has an outer ring portion, an inner ring portion and radial members connecting the outer ring portion and the inner portion, wherein the inner ring portion has a disk shaped center.

3. The load sensor of claim 2 further comprising other sensors operatively connected to the circuit board wherein the cylinder is configured to transfer the wheel loads to the circuit board from the resilient member such that circuit board is configured to move in response to the transferred wheel loads wherein the circuit board sensors are configured to measure strains of the circuit board caused by the movements of the circuit board.

4. The load sensor of claim 3 wherein the outer ring portion, the inner ring portion and the radial members define apertures through the circuit board.

5. The load sensor of claim 3 wherein the circuit board sensors comprise printed circuit traces.

6. The load sensor of claim 3 wherein the circuit board sensors attach to the radial members and the radial members are configured to move when the cylinder moves the circuit board to allow the disk shaped center to move in-plane with respect to the outer ring portion and to allow the disk shaped center to move perpendicular with respect to the radial members.

7. The load sensor of claim 6 wherein the circuit board sensors are configured to measure the movement of the disk shaped center.

8. The load sensor of claim 6 wherein the circuit board sensors are configured to measure the movement of the radial members.

9. The load sensor of claim 3 wherein circuit board sensors are configured to measure vertical loads applied by the wheel loads.

10. The load sensor of claim 3 wherein the circuit board sensors are configured measure radial loads applied by the wheel loads.

11. The load sensor of claim 3 wherein the outer ring portion includes a transverse area positioned adjacent to each of the radial members.

12. The load sensor of claim 11 wherein the circuit board sensors are positioned on the transverse area.

13. A suspension system for a vehicle that senses wheel loads applied by a road wheel of the vehicle to a housing and cylinder of the vehicle, the suspension system comprising: a strut connected to the road wheel, the strut being configured to receive the wheel loads; a resilient member operatively connected between the housing and the cylinder; an annular circuit board disposed co-axially about the cylinder and attached to the housing, the circuit board has an outer ring portion, and inner ring portion and radial members connecting the outer ring portion and the inner portion, wherein the inner ring portion has a disk shaped center; and sensors operatively connected to the circuit board wherein the cylinder is configured to transfer the wheel loads received from the strut to the circuit board from the resilient member such that the circuit board is configured to move in response to the transferred wheel loads wherein the sensors are configured to measure the movements of the circuit board.

14. The suspension system of claim 13 wherein the outer ring portion, the inner ring portion and the radial members define apertures through the circuit board.

15. The suspension system of claim 13 wherein the sensors comprise printed circuit traces.

16. The suspension system of claim 15 wherein the sensors attach to the radial members and the radial members are configured to move when the cylinder moves the circuit board to allow the disk shaped center to move in-plane with respect to the outer ring portion and to move perpendicular with respect to the radial members.

17. The suspension system of claim 16 wherein the sensors measure the movement of the disk shaped center and wherein the sensors measure the movement of the radial members.

18. The suspension system of claim 13 wherein the outer ring portion includes a transverse area positioned adjacent to each of the radial members.

19. The suspension system of claim 18 wherein the sensors are positioned on the transverse area.

20. The suspension system of claim 13 wherein the resilient member operatively connects with other sensors that measure strains of the resilient member caused by movement of the resilient member in response to the wheel loads transferred by the antifriction bearing, the other sensors resolving the strains into at least two independent degrees of freedom.

21. A method of monitoring wheel loads applied to a suspension system of a vehicle by road wheels of the vehicle, the method comprising: transferring the wheel loads of the road wheels from the suspension system to a resilient member that is positioned within the vehicle; moving the resilient member in response to the transferred wheel contact loads; measuring strains of the resilient member caused by the movement of the resilient member; and converting the measured strains of the resilient member into resolved load values of at least two independent degrees of freedom of the resilient member.

22. The method of claim 21 further comprising transferring the wheel contact loads from the resilient member to a circuit board within the vehicle.

23. The method of claim 22 further comprising measuring the movements of the circuit board caused by the transferred wheel contact loads by measuring flex movements of radial members of the circuit board.