Suspension system with magnetorheological clutch apparatus and set inertance

Abstract

A suspension system may have a suspension member operatively connected to a sprung mass and to an unsprung mass, the unsprung mass having an invariant resonance frequency relative to the sprung mass. A MR actuator unit(s) is configured to be positioned between the sprung mass and the unsprung mass, the at least one MR actuator unit including a torque source, and at least one MR clutch apparatus having an input operatively coupled to the torque source, and an output, the at least one MR clutch apparatus controllable to transmit a variable amount of torque between the input and the output. A mechanism between the output and one of the sprung mass and the unsprung mass, the mechanism configured to transmit a force from the output between the sprung mass and the unsprung mass. At least the output has at least one rotating component rotating to transmit the force between the sprung and the unsprung mass. The at least one rotating component has a cumulative inertia associated with a rotation around a rotational axis, the cumulative inertia contributing to a total inertance value of the suspension system. The total inertance value is in a range of 0.2 to 2.2 times a reference value of inertance to minimize an amplitude of transmissibility to the sprung mass at the invariant resonance frequency.

Description

SUSPENSION SYSTEM WITH MAGNETORHEOLOGICAL CLUTCH APPARATUS AND SET INERTANCECROSS-REFERENCE TO RELATED APPLICATION

[0001] The present application claims the priority of United States Patent Application No. 63 / 648,904, filed on May 17, 2024, the contents of which are incorporated herein by reference.TECHNICAL FIELD

[0002] The present application relates generally to magnetorheological (MR) fluid clutch apparatuses, and more particularly, to bodies using such apparatuses for dynamic control of motion in active motion control, such as in suspension systems or collaborative robots.BACKGROUND OF THE ART

[0003] A body moving in a desired direction, such as a vehicle, inevitably experiences motion in other directions as well. An undesired motion often arises from disturbances in the medium through which the body travels. For example, in a vehicle, whether one travels by land, sea, or air, one might encounter imperfections, bumps, waves, air pockets, and the like. Such undesired motion causes displacement, discomfort or annoyance to those in the body. This can also cause vibration and undesired horizontal or vertical movement to goods in the body. For certain susceptible individuals, the random accelerations resulting from the undesired motion can trigger a bout of motion sickness. In some cases, a particularly violent acceleration may even cause the operator to briefly lose control of the body. Also, goods can be damaged when submitted to acceleration or shocks. Even when stationary, there may be some residual vibration associated with the vehicle's engine. In motion, even on smooth roads, this residual vibration can become tiresome to occupants of the vehicle.

[0004] A primary purpose of a body’s suspension system is to provide vertical or horizontal compliance between the medium, such as the road, and the chassis or frame, in order to isolate the vehicle’s occupants or goods, supported by the chassis, from the roughness in the road and to maintain the contact point(s) with the road, thus providing a path for transferring forces from the contact point(s) to the chassis. In applications where the body is a wheeled body, the contact point is the wheel, thus also used to change the speed or direction of the body. In a wheeled body, examples of some common independent suspension linkages are known generally as strut & link (also called MacPherson strut), double A-arm (also called double wishbone or SLA), trailing arm, semi-trailing arm, multi-link, fork, scissor, pivot to name but a few.

[0005] In vehicles such as automobiles, each wheel assembly may be connected to the chassis by one or more links. A link is defined as a substantially rigid member with a joint or joints at each end that allows a particular motion to take place. It is these links that control the motion (or path) of the wheel as it moves up and down over road bumps.

[0006] The design of the suspension system for damping oscillations of the wheel usually represents a compromise between isolating the vehicle body from high-frequency oscillations (secondary ride) that may be produced by road surface irregularities and, on the other hand, achievinga high level of driving comfort for low-frequency oscillations of the vehicle body (primary ride). Each vehicle suspension combination will naturally have a wheel invariant resonance frequency that may refer to the characteristic frequency at which a wheel and tire assembly exhibits resonance, which remains relatively constant or invariant under certain conditions. Resonance refers to the natural tendency of a mechanical system to oscillate at specific frequencies when subjected to external forces or vibrations. In the context of a vehicle's wheel and tire assembly, the resonance frequency, also known as the natural frequency or eigenfrequency, is the frequency at which the wheel and tire system vibrates most easily. This resonance frequency depends on various factors including the mass distribution of the wheel and tire, the stiffness of the tire sidewall, and the properties of the suspension system. The term invariant suggests that this resonance frequency remains relatively consistent despite changes in other factors such as vehicle speed, road surface conditions, load distribution, or damping coefficient. This consistency in resonance frequency, i . e. , the invariant resonance frequency, can have implications for vehicle performance and stability, particularly in relation to a wheel hop phenomenon, or in relation to ride comfort.

[0007] The wheel invariant resonance frequency is important in the automotive industry as car designers design and tune suspension systems, tires, and other components to minimize unwanted vibrations, improve ride quality, and enhance vehicle handling characteristics. It may be a goal of identifying and optimizing the wheel resonance frequency, to mitigate issues such as wheel hop and ensure a smoother, more controlled driving experience.

[0008] Generally, all kinematically-induced wheel forces are either forces created by the interaction between the tires and the road, or inertial forces generated by the motion of the unsprung mass. The forces occurring between the tires and the road are transferred to the body via the suspension system. As long as the wheel assembly does not change its horizontal position or angular orientation relative to a smooth road surface, no substantial lateral or longitudinal tire forces (ignoring friction) will be created.

[0009] In semi-active suspension systems, damping forces are controlled, such as by variable valves of an hydraulic damper, by varying the viscosity of a magnetorheological fluid that flows in holes, etc. Active suspension systems may introduce forces that are independent of relative wheel motions and velocities.

[0010] In an active suspension, controlled forces are generated in the suspension, such as by hydraulic or electric actuators, between the sprung mass of the vehicle body and its occupants, and the unsprung mass of the wheel assemblies. The unsprung mass is the equivalent mass that reproduces the inertial forces produced by the motions of those parts of the vehicle not carried by the suspension system. This primarily includes the wheel assemblies, any mass damper associated with the wheel assemblies, and some portion of the mass of the suspension links. The sprung mass is the mass of the parts of the vehicle carried by the suspension system, including the body of the vehicle. Active suspension systems may introduce forces that are independent of relative wheel motions and velocities.

[0011] One type of active suspension system uses a linear motor direct drive approach. While this approach may be efficient from a performance standpoint, it may also be viewed as being relatively costly and heavy. Another type of electro-hydraulic active system is based on a pump adjusting the pressure of the hydraulic fluid in a conventional hydraulic damper. The electro-hydraulic approach may not be reactive enough from a dynamics standpoint (not enough bandwidth) to cope will all the spectrum of the road induced perturbations. This approach is usually able to cope with the primary ride attitude vehicle change (e.g. pitch and roll) but may deteriorate the secondary ride because it adds some inertance or reflected inertia on the unsprung mass side. In other word, the improvement of the primary ride is achieved, but instead of reducing the vibration associated with the frequencies of the secondary ride, some active suspension systems worsen them. In order to resolve this problem, a spring has been added in series with the suspension actuator and the unsprung mass in order to achieve a series-elastic suspension system. However, this added spring usually comes with a decrease in the natural frequency of the system, hence less mechanical bandwidth and reduced controllability.

[0012] A suspension inerter is a relatively newer component in vehicle suspension systems designed to enhance the vehicle's handling characteristics, particularly its ability to maintain tire contact with the road surface under varying conditions. The suspension inerter works alongside traditional suspension components such as springs, dampers (shock absorbers), to control the movement of the vehicle's body and wheels. Its function is to provide additional control over the relative motion between the vehicle's sprung mass and its unsprung mass.

[0013] The inerter typically consists of a mechanical device that utilizes the principles of inertance, which is the tendency of a mechanical system to resist changes in velocity. When integrated into a vehicle's suspension system, the inerter adds inertia to the system, which effectively helps decouple the motion of the sprung and unsprung masses. Inertance is an actuator’s resistance to linear acceleration, analogous to how a mass resists acceleration in Newton’s second law. It is a dynamic property that relates force to acceleration, just as stiffness relates force to displacement and damping relates force to velocity. Inertance is typically modeled in a 2-port system, where the actuator connects two masses or nodes (e.g., attachment positions of an unsprung mass muand a sprung mass ms). The force generated by the actuator is proportional to the relative acceleration between these two points on the unsprung mass muand the sprung mass ms). The inertance can be in the following equation: F=Js x" (force proportional to the relative acceleration x" between the two point attachment positions on). Here, Js is the inertance, with units of kilograms (kg) in linear systems (or kg- m2in rotational systems). When multiplied by acceleration, it yields a reactive force opposing motion.

[0014] By adding inertance, the suspension inerter may: A) improve grip and traction by helping to maintain consistent tire contact with the road surface, especially during cornering, braking, and acceleration, B) enhance vehicle stability by reducing unwanted oscillations and vibrations, particularly at high speeds or on uneven road surfaces, and / or C) increase responsiveness and control by optimizing the dynamic behavior of the suspension system, improving handling and overall drivingperformance. However, inertance is also known to increase transmissibility offeree between unsprung mass and sprung mass.

[0015] Magnetorheological (MR) fluid actuators have been proposed to solve most of the previous problems. Some suspension systems feature pairs of MR fluid clutch apparatuses that result in a high bandwidth active suspension system with high transparency (e.g., U.S. Patent No. 10,625,556). Also, some suspensions allow tunable inertance and damping shock absorber. However, in comparison to passive damping systems, active suspension systems and tunable inertance dampers are usually more complex and cost-intensive. They also may need high resolution and expensive sensors to operate. In addition, any pure delay introduced in the signal treatment may decrease the performance of such inertance, making it difficult to have the desired inertance by adding or removing inertance virtually.

[0016] For that reason, there is still a need for a more economical active suspension system that may combine both features.SUMMARY

[0017] It is an aim of the present disclosure to provide a method and system for minimizing force transmission between an unsprung mass and a sprung mass specifically at the wheel invariant resonance frequency.

[0018] It is a further aim of the present disclosure to provide novel active suspension control systems using magnetorheological fluid clutch apparatuses.

[0019] It is a still further aim of the present disclosure to use such systems in passenger vehicles.

[0020] Therefore, in accordance with a first aspect of the present disclosure, there is provided a suspension system comprising: a suspension member operatively connected to a sprung mass and to an unsprung mass, the unsprung mass having an invariant resonance frequency relative to the sprung mass; at least one MR actuator unit configured to be positioned between the sprung mass and the unsprung mass, the at least one MR actuator unit including a torque source, and at least one MR clutch apparatus having an input operatively coupled to the torque source, and an output, the at least one MR clutch apparatus controllable to transmit a variable amount of torque between the input and the output; a mechanism between the output and one of the sprung mass and the unsprung mass, the mechanism configured to transmit a force from the output between the sprung mass and the unsprung mass; wherein at least the output has at least one rotating component rotating to transmit the force between the sprung and the unsprung mass; wherein the at least one rotating component has a cumulative inertia associated with a rotation around a rotational axis, the cumulative inertia contributing to a total inertance value of the suspension system; and wherein the total inertance value is in a range of 0.2 to 2.2 times a reference value of inertance to minimize an amplitude of transmissibility to the sprung mass at the invariant resonance frequency.

[0021] Further in accordance with the first aspect, for instance, the torque source of the at least one MR actuator unit is at least one motor.

[0022] Still further in accordance with the first aspect, for instance, the torque source of the at least one MR actuator unit is a connection to a frame, whereby the at least one MR actuator unit is a motorless brake.

[0023] Still further in accordance with the first aspect, for instance, multiple of the MR clutch apparatuses may be present and arranged in parallel, and wherein the total inertance value includes the cumulative inertias of the outputs of the MR clutch apparatuses.

[0024] Still further in accordance with the first aspect, for instance, the mechanism converts a rotation of the output to a translation.

[0025] Still further in accordance with the first aspect, for instance, the mechanism is a rack and pinion.

[0026] Still further in accordance with the first aspect, for instance, the mechanism includes a ballscrew system displacing a threaded rod whereby the ballscrew and the threaded rod contribute to the total inertance value.

[0027] Still further in accordance with the first aspect, for instance, the threaded rod is located within a coil spring.

[0028] Still further in accordance with the first aspect, for instance, the mechanism includes at least one structural link rotatably coupled to the output, whereby the at least one structural link contributes to the total inertance value.

[0029] Still further in accordance with the first aspect, for instance, a reduction mechanism may be between the torque source and the MR clutch apparatus, whereby the reduction mechanism does not contribute to the total inertance value.

[0030] Still further in accordance with the first aspect, for instance, the mechanism includes a reduction mechanism connected to the output of the MR clutch apparatus, whereby the reduction mechanism contributes to the total inertance value.

[0031] Still further in accordance with the first aspect, for instance, the suspension system includes two of the MR actuator unit, wherein the MR actuator units are antagonistic to one another.

[0032] Still further in accordance with the first aspect, for instance, the two MR actuator units are operatively connected to a common member of the mechanism.

[0033] Still further in accordance with the first aspect, for instance, the common member of the mechanism is a ball nut.

[0034] Still further in accordance with the first aspect, for instance, the suspension system includes a floating rack operatively coupled to a pinion of the output, and wherein the total inertance value includes the inertias of the floating rack and of the pinion.

[0035] In accordance with a second aspect of the present disclosure, there is provided a suspension system comprising: a suspension member operatively connected to a sprung mass and to an unsprung mass, the unsprung mass having an invariant resonance frequency; at least one MR actuator unit configured to be positioned between the sprung mass and the unsprung mass, the at least one MR actuator unit including a torque source, and at least one MR clutch apparatus having an input operatively coupled to the torque source, and an output, the at least one MR clutch apparatuscontrollable to transmit a variable amount of torque between the input and the output; a mechanism between the output and one of the sprung mass and the unsprung mass, the mechanism configured to transmit a force from the output between the sprung mass and the unsprung mass; wherein at least the output has at least one component rotating to transmit the force between the sprung and the unsprung mass; wherein the at least one component has a cumulative inertia, the cumulative inertia contributing to a total inertance value of the suspension system; and wherein the total inertance value is in a range of 0.2 to 2.2 times a reference value of inertance to minimize an amplitude of transmissibility to the sprung mass at the wheel invariant resonance frequency.DESCRIPTION OF THE DRAWINGS

[0036] Fig. 1 is a schematic view of a generic magnetorheological (MR) clutch apparatus that may used in a suspension system of the present disclosure;

[0037] Fig. 2 is a sectioned schematic view of the MR clutch apparatus of Fig. 1 , in accordance with an embodiment;

[0038] Fig. 3A is a representation of a MR actuator unit using a single motor and a single clutch, that may used in a suspension system of the present disclosure;

[0039] Fig. 3B is a representation of a MR damper using a single clutch, that may used in a suspension system of the present disclosure;

[0040] Fig. 4 is a representation of a MR actuator unit using a single motor and double clutches, that may used in a suspension system of the present disclosure;

[0041] Fig. 5A is a representation of two MR actuator unit using organized in a parallel path, that may used in a suspension system of the present disclosure;

[0042] Fig. 5B is a representation of one MR actuator unit using organized in a parallel path with a MR clutch apparatus, that may used in a suspension system of the present disclosure;

[0043] Fig. 6 is s representation of a MR actuator unit used to control a vehicle seat;

[0044] Fig. 7 is a representation of a MR actuator unit used to control a truck cabin;

[0045] Fig. 8 is a representation of a MR actuator unit used to control the frame of a vehicle;

[0046] Fig. 9 is a representation of the Force versus Speed of a typical vehicle active suspension;

[0047] Fig. 10 is the typical bode plot of a MR actuator unit;

[0048] Fig. 11 is a typical PSD graph of an active suspension using MR actuator unit versus a passive (stock) suspension;

[0049] Fig 12 is a graph showing typical comfort improvement of an active suspension using a MR actuator unit versus state of the art technologies;

[0050] Fig. 13 is the representation of an ISO2631 filter used to qualify the Mechanical Vibration And Shock - Evaluation Of Human Exposure To Whole-Body Vibration;

[0051] Fig. 14 is a schematic representation of a vehicle suspension system using a linear MR actuator unit in accordance with the present disclosure;

[0052] Fig. 15 is a schematic representation of a linear MR actuator unit, that may used in a suspension system of the present disclosure;

[0053] Fig. 16A is a more detailed representation of the linear MR actuator unit of Fig. 15;

[0054] Fig. 16B is an alternative configuration of the linear MR actuator unit of Fig. 15 with a single motor;

[0055] Fig. 17 is a schematic representation of a vehicle suspension system using a rotary MR actuator unit, that may be in accordance of the present disclosure;

[0056] Fig. 18A is a schematic representation of a rotary MR actuator unit, that may used in a suspension system of the present disclosure;

[0057] Fig. 18B is an alternative configuration of the linear actuator of Fig. 18 with a single motor, that may used in a suspension system of the present disclosure;

[0058] Fig. 19 is a more detailed representation of the rotary MR actuator unit of Fig. 15;

[0059] Fig. 20 is a schematic representation of a linear MR actuator unit using a rack and pinion couple with a single motor and a single clutch, that may used in a suspension system of the present disclosure;

[0060] Fig. 21A is a schematic representation of a semi-active vehicle suspension with controllable spring stiffness and controllable damping that has an intrinsic inerter (or inertance value), all acting in parallel;

[0061] Fig. 21 B is schematic representation of a vehicle active suspension with controllable spring stiffness, controllable damping, controllable force actuator, that has an intrinsic inerter (or inertance value) ), all acting in parallel;

[0062] Fig. 22A is a schematic representation of a vehicle semi-active suspension with controllable spring stiffness, controllable damping, that has an intrinsic inerter (or inertance value) acting in series with the damper;

[0063] Fig. 22B is a schematic representation of a vehicle active suspension with controllable spring stiffness, controllable damping, controllable force actuator, that has an intrinsic inerter (or inertance value) acting in series with the damper;

[0064] Fig. 23A is a graph of the force versus velocity of typical MR damper (MagneRide) and typical valve controllable damper acting in two quadrants;

[0065] Fig. 23B is a graph of the force vs. velocity of a typical valve controllable damper acting in two quadrants in function of the current at the input of the damper;

[0066] Fig. 24 is a graph of the force versus velocity of a typical MR clutch based controllable damper acting in two quadrants;

[0067] Fig. 25 is a graph of the force versus velocity of a typical MR clutch based controllable active suspension acting in four quadrants;

[0068] Fig. 26 is a table of typical vertical RMS sprung weight weighted acceleration vs unsprung weight weighted acceleration according to ISO 2631 filter of Fig. 13;

[0069] Fig. 27 is a schematic illustration of a typical quarter car model, that may used in a suspension system of the present disclosure;

[0070] Fig. 28 represents equations when an inerter is added to the equations of motion, the state equations being rederived;

[0071] Fig. 29 is a 3D PSD map of an active suspension system using a MR actuator unit for various inertance values;

[0072] Fig. 30 is a PSD graphic of an active suspension system using a MR actuator unit for various inertance values;

[0073] Fig. 31 represents the equation to decrease the wheel invariant resonance frequency;

[0074] Fig. 32 are bode diagrams of the transfer function between the inertance force and the spring force;

[0075] Fig. 33 are 3D PSD graphics of sprung mass acceleration with various suspension inertance;

[0076] Fig. 34 is a PSD graph of sprung mass acceleration with various suspension inertance;

[0077] Fig. 35 is a table showing properties of an exemplary vehicle used, a BMW 330Ci;

[0078] Fig. 36 is a table of weighted sprung mass acceleration for various suspension types;

[0079] Fig. 37 are a series PSD graphs sprung mass acceleration for various suspension types showing the frequency and the amplitude of the wheel invariant resonance frequency;

[0080] Fig. 38 shows the amplitude of the wheel invariant resonance frequency for various inertance values for the BMW 330Ci;

[0081] Fig. 39 is a schematic view of a suspension ratio for a double-wishbone suspension type;

[0082] Fig. 40 is sectional view the linear actuator of Fig. 16b with the main components contributing to the inertance identified; and

[0083] Fig. 41 is a schematic view of a suspension system with set inertance in accordance with another aspect of the present disclosure, with a linear floating rack.DETAILED DESCRIPTION

[0084] Referring to the drawings and more particularly to Fig. 1 , there is illustrated a magnetorheological (MR) fluid apparatus 10 configured to provide a mechanical output force based on a received input current. The MR clutch apparatus 10 is shown as being of the type having collinear input and output shafts. However, the concepts described herein may apply to other configuration of MR clutch apparatuses, for instance some with an input or output outer shell / casing for an output or input shaft, etc. The principles illustrated here will be performed using a MR clutch apparatuses of drum type but could also be applied to a disc type MR clutch apparatus. In the following description, starting with Fig. 3, reference is made to systems and MR actuator units having one or more MR clutch apparatuses 10. When such reference is made, the MR clutch apparatus 10 may be as described in Figs. 1 and 2, or may be any other MR clutch apparatus 10 such as versions with discs, unless stated otherwise. In some embodiments, MR clutch apparatus 10 may be normally open, normally closed, or partially closed clutch type unit.

[0085] The MR clutch apparatus 10 may transmit an output force in response to an input current received from an operator, to transmit an input force and an output force based on the magnetization level of a magnetizable part in the magnetic circuit when there is no input current. The example MR clutch apparatus 10 may have a stator 10A to which the MR clutch apparatus 10 is connected to astructure. The MR clutch apparatus 10 features driven member 11 and driving member 12 separated by gaps filled with an MR fluid, as explained hereinafter. The driving member 12 may receive rotational energy (torque) from a power device, such as a motor, with or without a transmission, such as a reduction gear box, etc.

[0086] According to an embodiment, the driving member 12 may be in mechanical communication with a power input, and driven member 11 may be in mechanical communication with a power output (i.e. , force output, torque output). The stator 10A, the driven member 11 and the driving member 12 may be interconnected by bearings 12A and 12B. In the illustrated embodiment, the bearing 12A is between the stator 10A and the driving member 12, whereas the bearing 12B is between the driven member 11 and the driving member 12. Seals 12C may also be provided at the interface between the driven member 11 and the driving member 12, to preserve MR fluid between the members 11 and12. Moreover, the seals are provided to prevent MR fluid from reaching the bearing 12B or to leak out of the apparatus 10.

[0087] As shown with reference to Fig. 2, drums are located circumferentially about the rotational axis CL. The drums are one possible configuration of shear surface, and the present disclosure may use MR clutch apparatuses with disks instead of drums. The configuration shown in Figs. 1 and 2 is just given as an example of a MR clutch apparatus, with multiple other configurations being usable in accordance with the present disclosure. Some support must therefore extend generally radially to support the drums in their circumferential arrangement. In accordance with one embodiment, referring to Fig. 2, a low permeability input drum support 13 (a.k.a., radial wall) projects radially from a shaft of the driving member 12. The input drum support 13 may be connected to an input rotor 14 defining the outer casing or shell of the MR clutch apparatus 10. The input rotor 14 may therefore be rotatably connected to the driven member 11 by the bearing 12B. In an embodiment, the input rotor 14 has an input rotor support 14A which forms a housing for the bearing 12B. According to an embodiment, the input rotor support 14A is an integral part of the input rotor 14, and may be fabricated as a single piece. However, this is not desirable as the input rotor support 14A is ideally made from a low permeability material and the input rotor is made from a high permeability material. As another embodiment, as shown in Fig. 2, the input rotor support 14A may be defined by an annular wall fabricated separately from a remainder of the input rotor 14, though both are interconnected for concurrent rotation. Therefore, the shaft of the driving member 12, the input drum support 13 and the input rotor 14 rotate concurrently. In an embodiment, it is contemplated to have the outer shell of the MR clutch apparatus 10 be part of the stator 10A, or of the driven member 11 .

[0088] The input drum support 13 may support a plurality of concentric annular drums 15, also known as input annular drums. The input annular drums 15 are secured to the input drum support13. In an embodiment, concentric circular channels are defined (e.g., machined, cast, molded, etc) in the input drum support 13 for insertion therein of the drums 15. A tight fit (e.g., force fit), an adhesive and / or radial pins may be used to secure the drums 15 to the input drum support 13. In an embodiment, the input drum support 13 is monolithically connected to the shaft of the driving member12, whereby the various components of the driving member 12 rotate concurrently when receiving the drive from the power source.

[0089] The driven member 11 is represented by an output shaft, configured to rotate about axis CL as well. The output shaft may be coupled to various mechanical components that receive the transmitted power output when the clutch apparatus 10 is actuated to transmit at least some of the rotational power input. In some embodiments, some other components of MR clutch apparatus 10 may be attached or combined to other components (i.e. , the driving member 12 may be combined with the stator 10a, the drum support 13, the input rotor 14 and the rotor support 14A so all those part may be anchored to a chassis while not rotating).

[0090] The driven member 11 also has a one or more concentric annular drums 16, also known as output drums, mounted to an output drum support 17. The output drum support 17 may be an integral part of the output shaft, or may be mounted thereon for concurrent rotation. The annular drums 16 are spaced apart in such a way that the sets of output annular drums 16 fit within the annular spaces between the input annular drums 15, in intertwined fashion. When either of both the driven member 11 and the driving member 12 rotate, there is no direct contact between the annular drums 15 and 16, due to the concentricity of the annular drums 15 and 16, about axis CL.

[0091] The annular spaces between the input annular drums 15 of the driving member 12, and the output annular drums 16 of the driven member 11 are filled with the MR fluid 19. The MR fluid 19 used to transmit force between the driven member 1 1 and the driving member 12 is a type of smart fluid that is composed of magnetisable particles disposed in a carrier fluid, usually a type of oil, but the carrier fluid may also be present in a gaseous form (a.k.a., dry MR fluid). As another possibility, the MR “fluid” may be a powder. Hence, reference is made herein to a MR fluid, and encompasses these various options. Moreover, while reference is made to MR clutch apparatus, other known terms for such clutches includes MR fluid clutch apparatus, MR clutch, MR fluid clutch, among other names. Likewise, MR actuator unit(s) described herein may also be known as MR fluid actuator unit(s), MR fluid actuator(s), among other names. When subjected to a magnetic field, the fluid may increase its apparent viscosity, potentially to the point of becoming a viscoplastic solid. The apparent viscosity is defined by the ratio between the operating shear stress and the operating shear rate of the MR fluid between opposite shear surfaces. The magnetic field intensity mainly affects the yield shear stress of the MR fluid.

[0092] According to Fig. 3A, a MR actuator unit 20 (also known as a MR fluid actuator unit) is shown having a MR clutch apparatus 10 of the type described above or of any other suitable type. The actuator is composed of a motor 21 , an input gearbox 22, a MR clutch apparatus 10, an output gearbox 23 and an output 24, though one or both of the gearboxes may be optional.

[0093] According to Fig. 3B, a MR actuator unit (or damper) 26 has a single MR clutch apparatus 10 of the type described above or of any other suitable type. The actuator has the MR clutch apparatus 10, an output gearbox 23 and an output 24, though the gearboxes may be optional. In this configuration, the driving member 12 may be combined with the stator 10a, the drum support 13, theinput rotor 14 and the rotor support 14A so all those part may be anchored to a chassis while not rotating.

[0094] Another type of MR actuator unit is shown on Fig. 4 and includes a single motor, an input gearbox 22, two MR clutch apparatuses 10A and 10B receiving torque from the motor 21 , the MR clutch apparatuses 10A and 10B turning in opposite direction an applying antagonistic forces on the output 24, each through gearbox 23A and 23B.

[0095] Another type of MR actuator unit is shown on Fig. 5A and includes two MR actuator units similar to the one of Fig. 3, and working in parallel in order to apply a force on a single output 24, with the gearboxes being optional. The first branch of actuation is composed of a motor 21A, an input gearbox 22A, a MR clutch apparatus 10A, an output gearbox 23A driving the output 24. The first second branch of actuation is composed of a motor 21 B, an input gearbox 22B, a MR clutch apparatus 10B, an output gearbox 23B driving the same output 24.

[0096] Another type of MR actuator unit is shown on Fig. 5B and is composed of one MR actuator unit similar to the one of Fig. 3A working in parallel with one MR actuator unit similar to the one of Fig. 3B in order to apply a force on a single output 24, with the gearboxes being optional. The MR clutch apparatus 10B may be used to apply braking torque as a possibility.

[0097] Figs. 6, 7 and 8 show a MR actuator unit 20 of any type taken from Figs. 3, 4 or 5 integrated in an active suspension system 60 that may be arranged in accordance with the present disclosure, as detailed herein. The suspension 60 is said to be “active”, in that it applies forces to different types of masses, such as a platform, by a controlled MR actuator unit 20 relative to a structure of the vehicle. More specifically, Fig. 6 shows an active suspension 60 controlling the seat of a vehicle, Fig. 7 shows an active suspension 60 controlling the cabin of a truck and Fig. 8 shows an active suspension 60 installed to control the frame of a vehicle. Each active suspension 60 may control the forces between a suspended platform or like mass and an underlying base or like structure. The forces may be independent of relative motions and velocities in the environment of or at a suspended platform. The active suspension system 60 receives energy from at least a power source such as a motor to which it is coupled by one or more MR clutch apparatuses. Motor 21 may be electric, pneumatic, hydraulics, ICE or any other type. The active suspension system 60 has a mechanism, in the form of linkage system, coupled to platform 61 (e.g., seat, pallet, stretcher, truck cabin, transportation box, only to name a few) for transmitting motion output by the MR clutch apparatus(es) 10 to the platform 61 . A sensor or sensors 62 provide information indicative of a state of the suspended platform 63, and a controller 64 receives the information indicative of the state of the platform 63 and outputs a signal to the MR clutch apparatus(es) 10 to cause the MR clutch apparatus(es) 10 to exert a force on the suspended platform 63. Alternatively, the sensor(s) 24 may be on the structure supporting the platform 63, and / or on components of the active suspension system 60, to measure the state of any such component. Additional components may be provided, such as an air spring 65 or like biasing device or suspension component, in parallel to the linkages. Other actuator or damping device 66 may also be added in parallel or in series with the MR actuator units 20. Damping devices may be of adjustable type or non-adjustable type. It is to be noted that for a reason of simplicity, the explanationis described with the control of one degree of freedom but that multiple actuators could be used to control multiple degrees of freedom of the body. Moreover, the multiple MR clutch apparatuses could share the same power source, as is the case in Fig. 3 with both MR clutch apparatuses 10 receiving the actuation power from the single motor 21 , via a transmission 22. The transmission 22 is illustrated as featuring a gearbox but pulleys and belts may be used. Transmission 22 but may also be of other type such as a, chain and pinions, etc., only to name a few. Other devices can be used as variable force sources as alternatives to the air spring 65.

[0098] The combination of a variable power source with the MR clutch apparatus(es) 10 presents advantages of a hybrid system where one device or the other (or both simultaneously) can be controlled depending on the condition of operation. In an example where the power source is an electric motor, the electric motor speed and available torque can be controlled as well as the torque transmitted by the MR clutch apparatus(es) 10. This may increase the potential points of operation while increasing the overall performance or efficiency of the system. The output of the MR clutch apparatuses can be decoupled from the input. In some application, this can be useful to decouple the inertia from the input in order not to affect the time of response of the output.

[0099] Figs. 6 to 8 are representative of an implementation of the suspension system of the present disclosure. Sensors 62 gather information indicative of a state of the platform 63, of the structure supporting the platform 62 and / or components of the active suspension system 60, and controller 64 outputs a signal to the MR actuator unit 20 based on the state. For example, the controller 64 may include one or more processing units, and a non-transitory computer-readable memory communicatively coupled to the processing unit(s) and comprising computer-readable program instructions executable by the processing unit to operate the MR actuator unit 20 to achieve a desired behavior for the platform 63. The desired behavior may be a comfort behavior, in which the platform 63 must not be exposed to accelerations beyond a given level, in a particular direction (e.g., up and down). Therefore, the controller 64 will control the action of the MR actuator unit 20 to ensure that the platform 63 moves within the limits of the desired behavior, in spite of disturbances sustained by the structure (e.g., vehicle chassis). Likewise, the desired behavior could be a control behavior entailing that the platform 63 limits its span of movements in some controllable directions. Therefore, the active suspension system 60, and other embodiments of suspension described below, adopt an active control in that force is applied to control the movement behavior of an item, such as a passenger supporting platform or a wheel assembly, to name but a few examples.

[0100] Fig. 9 shows an exemplary the force versus velocity (F-V) graph of a typical active suspension of vehicle. The F-V of each of the four wheels is illustrated.

[0101] Fig. 10 shows an exemplary mechanical transfer function of a MR actuator unit 20 when the MR clutch apparatus 10 is maintained in slippage. Such transfer function is illustrated when used with and without feedforward controller. MR actuator units such as 20 are known to provide high mechanical bandwidth (e.g. >10Hz) when one or more MR clutch apparatuses are maintained in slippage.

[0102] Fig. 11 is an exemplary power spectral density (PSD) graph showing the typical frequencies that a vehicle suspension system is submitted to. Significant power may be present up to roughly 50Hz so it may be an advantage for an active suspension system to provide a counter force up to that frequency.

[0103] Fig. 12 shows the discomfort index J of various passive, semi-active, slow active and full active suspension. The lower the discomfort index J is the more comfortable the suspended platform may be.

[0104] Fig. 13 shows the ISO 2631 filter used to qualify the Mechanical Vibration And Shock - Evaluation Of Human Exposure To Whole-Body Vibration. It may be seen that the most important frequencies to improve human comfort are between 1 Hz and 30Hz, frequencies for which the gains are larger than 0.5 on the filter.

[0105] Fig. 14 shows a linear MR actuator unit that may be used in various wheel suspension systems, such as those in accordance with the present disclosure, for suspending a wheel assembly from a sprung body of a wheeled vehicle. The MR actuator unit 20 allows the wheel assembly to move relative to the sprung body (i.e. , the chassis of the vehicle supported by the suspension system of Fig. 14, through a bounce and rebound vertical travel, as limited by mechanical stops. The wheel assembly may be the rear wheel assembly and / or the front wheel assembly of a passenger vehicle such as an automobile, a front or rear wheel assembly of a motorcycle, the front or rear wheel assembly of a transportation cart, only to name a few. In some configurations, the relative rotational centers are disposed rearward and outboard of their respective pivots.

[0106] In some cases, the upper relative rotation center and upper pivot are disposed along a first generally horizontal line, and the lower relative rotation center and lower pivot are disposed along a second generally horizontal line, with the automobile at rest and loaded to its design weight. The upper and lower rotation centers are preferably separated from their respective pivots by different arm lengths, though this is optional. The term “design weight” should be understood from ISO / IS 2958, which specifies the loading for passenger vehicles as a function of the number of seats. Typically, the suspension is roughly at the center of its vertical travel at rest at the design weight. In some embodiments, the active suspension system includes an electric motor adapted to receive electrical power, coupled with one of more of the MR clutch apparatus 10 of the active suspension system 60 to produce the active control force.

[0107] The active suspension system may include subsystems 140 for each wheel assembly. In some configurations, a first structural link 141 may be coupled to the wheel assembly to define a first relative rotation center, and may be rotationally coupled to the sprung body at a first pivot, with the suspension further including a second structural link 142 coupled to the wheel assembly to define a second relative rotation center above the first relative rotation center, and rotationally coupled to the sprung body at a second pivot above the first pivot. The wheel suspension may define a geometry selected to minimize the horizontal kinetic displacement of the wheel assembly as the structural link 143 attached between any of the first or second structural and the sprung body moves through an active control range over its vertical travel.

[0108] Referring to Fig. 15, the subsystem uses a pair of MR clutch apparatuses 10, 10’ to control the rotation of a threaded rod 151 of a ballscrew or like actuator featuring a threaded nut 152, using the power provided by the motors 21 ,21 ’ (although a single motor could be used as well as exemplified previously). The rotational outputs from motors 21 , 21’ are hence converted into back and forth translation of the threaded rod 151. The subsystem of Fig. 15 may be placed in the middle of a coil spring (as in Fig. 15) as an option or in parallel to a strut or spring / damper system. The characteristics of a suspension system featuring the subsystem of Fig. 15 may be selected to be in accordance with the present disclosure.

[0109] The rotational output from the motors 21 and 2T is transmitted to the input of MR clutch apparatuses 10 and 10’ using mechanisms 84 and 84’. The input reduction mechanism 84 may turn in the clockwise direction, while the input reduction mechanism 84’ may turn in the counter clockwise direction. A belt system may present the advantage that it has less backlash than some other types of reduction mechanism. Other type of backlash reduction strategies may also be desirable, like preloaded gear or preloaded ball screw, only to name a few. Hence, the rotations caused by either one of the MR clutch apparatuses 10 or 10’ are converted by the engagement of the ballscrew rod 151 and nut 152 into back and forth translations of the nut 152 connected to the sliding member 88. The subsystem may be placed in the middle of the hollow central volume of a coil spring 65 or in parallel to a strut or spring / damper system.

[0110] Fig. 16a shows a cross section of the device of Fig. 15, illustrating that the output members of both MR clutch apparatuses 10 and 10’ may be connected to a single output, being in this case the threaded ballscrew rod 151 of a ball-screw mechanism, or other rod for other types of linear actuators. In the shown embodiment, the outputs are connected to the screw but other embodiments may be possible where the output of the MR clutch apparatuses 10 and 10’ may be connected to a common ball nut, or each to separate ball nuts. Though optional, connecting each MR clutch apparatus to an individual ball nut may present the advantage of reducing the backlash of the system when both clutches are working antagonistically.

[0111] Fig. 16b shows a cross section of a device similar to the device of Fig. 16a with an alternative configuration where only one MR clutch apparatus 10 is connected to the motor 21. The MR clutch apparatus 10’ is connected to the chassis of the device, and may for instance introduce braking torque. The output members of both MR clutch apparatuses 10 and 10’ are connected to a single output, being the threaded ballscrew rod 151 of a ball-screw mechanism.

[0112] In the embodiments shown in Fig. 17, the motor and MR clutch apparatuses 10 may be located distally from the wheel assemblies, in which various configurations are shown to transmit motor actuation to wheel assemblies. Fig. 17 shows a rotary mechanism that is configured to receive force from the MR clutch apparatuses 10 as part of the active suspension system 60, to actively control the wheel assemblies or other parts of a vehicle. Distal actuation may be transmitted using a push rod, but could also use hydraulic tubes or cables, forming part of the mechanism.

[0113] Referring to Figs. 18a and 19, a similar configuration to that of Fig. 15 is illustrated, but using an output reduction transmission 86 (e.g., bevel gears) and 86’ instead of ball screw, the outputreduction mechanisms 86 and 86’ each having an output shaft 87 and 87’ that is connected to a single actuator output member 88. In an alternative configuration, both MR clutch apparatuses 10 and 10’ may be connected to the same output reduction transmission 86 instead of having a second output reduction mechanisms 86’ or other transmission.

[0114] The embodiment of Fig. 18a, or other embodiments described herein, may also be used as part of a robot joint. Such systems are described in International patent application publication no. WO2021155478A1 , incorporated herein by reference.

[0115] Fig. 18b shows a cross section of a device similar to the device of Fig. 18a with an alternative configuration where only one MR clutch apparatus 10 is connected to a motor 21 . The MR clutch apparatus 10’ is connected to the chassis of the device. The output members of both MR fluid MR clutch apparatuses 10 and 10’ are connected to a single output.

[0116] In accordance with another embodiment (not shown), the active suspension system may be applied to a roll bar for a motor vehicle. Roll bars may be on the rear wheels of the vehicle, but another roll bar could be used on the front wheels as well. Roll bar may be a split torsion bar, which is fastened rotatably to a vehicle chassis. It is also considered for the clutch arrangement to connect the first roll bar portion to the second roll bar portion in such a way that they rotate in unison as a function of the actual and / or expectable lateral acceleration of the vehicle. It is thus possible to automatically uncouple the roll bar during the straight-line travel of the vehicle and to automatically couple it again during travel in a curve.

[0117] A clutch arrangement of a roll bar can be embodied according to an alternative embodiment if the first roll bar portion and the second roll bar portion are connectable to one another, to rotate in unison, such that it is axially displaceable as a whole by the clutch arrangement. The clutch arrangement can be preferably controlled as a function of the velocity of the vehicle and the steering angle and / or the angular velocity of the steering wheel and / or the lateral acceleration of the vehicle, all of which may be part of the state of the vehicle obtained by the sensors 24. To rule out a safety hazard during a possible malfunction, the clutch arrangement may have redundancy such that remains at least partially functional in case of a defect. In another embodiment, the active suspension system with the MR clutch apparatuses 10 can be installed in parallel or concentrically to a soft torsion bar and only used as a stiffness increaser. Accordingly, the active suspension system as described above is a relative cost-effective semi-active or fully active roll bar which is always sufficiently effective during travel in a curve as well as in evading maneuvers and also affects the spring action characteristics of the vehicle in order to enhance driving smoothness.

[0118] In another embodiment (not shown), the MR actuator units such as 20 are located distally while a spring 65 and a hydraulic actuator or piston are located at each wheel, in a parallel arrangement. The MR clutch apparatuses 10 provide active motion control to each wheel in two directions using two distinct hydraulic conduits. One of the hydraulic conduits may be used to transmit the required active motion control forces to hydraulic actuator or piston at the wheel in one direction while the other conduit may be used to transmit the force in the other direction. The biasing memberor spring 65 may be used to support the sprung weight and transmit part of the load to the unsprung weight.

[0119] Fig. 20 shows a system with single motor 21 and single MR clutch apparatus 10. A single MR clutch apparatus 10 is used with a pinion 203 on the structural link 201 , acting as a MR fluid brake by providing braking of the movement of the structural link 201 in the unbiased direction by applying a force on rack portion 204. The motor 21 may be a bi-directional motor in any of the embodiments described herein.

[0120] Fig. 21 A shows a semi-active suspension 60 with inerter or intrinsic inertance 210. On this figure, the spring 65 is of controllable type and the damper 66 is of controllable type. The spring, 65, the controllable damper 66 and the inerter 210 are all applying forces in parallel between the unsprung mass 61 and the sprung mass 63.

[0121] Fig. 21 B shows an active suspension system 60 similar to the one of Fig. 21 A with an actuator 62 able to apply a force in parallel between the unsprung mass 61 and the sprung mass 63.

[0122] Fig. 22A shows a semi-active suspension 60 where the inerter or intrinsic inertance 210 is in series with the controllable damper 66.

[0123] Fig. 22B shows an active suspension system 60 similar to the one of Fig. 22A with an actuator 62 configured to apply a force in parallel between the unsprung mass 61 and the sprung mass 63.

[0124] All of the suspension systems and components thereof shown from Fig. 15 to Fig. 20, Fig. 21 B and Fig. 22B may be or may be part of a suspension system arranged in accordance with the present invention. More particularly, as described below. More particularly, the suspension systems and components thereof shown from Fig. 15 to Fig. 20, Fig. 21 B and Fig. 22B may be or may be part of a suspension system that may include a suspension member operatively connected to a sprung mass and to an unsprung mass, the unsprung mass having an invariant resonance frequency sometimes called the wheel resonance frequency or wheel eigenfrequency; at least one MR actuator unit configured to be positioned between the sprung mass and the unsprung mass, the at least one MR actuator unit including a torque source, and at least one MR clutch apparatus having an input operatively coupled to the torque source, and an output, the at least one MR clutch apparatus controllable to transmit a variable amount of torque between the input and the output; a mechanism between the output and one of the sprung mass and the unsprung mass, the mechanism configured to transmit a force from the output between the sprung mass and the unsprung mass; wherein at least the output has at least one rotating component rotating to transmit the force between the sprung and the unsprung mass; wherein the at least one rotating component has a cumulative inertia associated with a rotation around a rotational axis, the cumulative inertia contributing to a total inertance value of the suspension system; and wherein the total inertance value is in a range of 0.2 to 2.2 times a reference value of inertance to minimize an amplitude of transmissibility to the sprung mass at the invariant resonance frequency.

[0125] For example, Figs. 21 B and 22B are active suspension systems 60 in accordance with the present disclosure. While the active suspension systems 60 of Figs. 21 B and 22B show the damper66 and the inerter 210 as components separate from the MR actuator unit 20, it is the MR actuator unit 20 that may in and of itself act as damper 66 and inerter 210. In the active suspension systems 60 of Figs. 21 B and 22B, and output of the MR actuator unit and mechanism transmitting force between sprung mass and unsprung mass have components rotating according to the relative movement between the sprung and the unsprung mass. At the very least, such rotating component is the output of the MR fluid actuator. Such mechanism may include the threaded rod 151 in the suspension system of Figs. 15, 16A, 16B, link 141 in the suspension system of Fig. 17, the reduction mechanisms 86 and 86’ in Figs. 18A, 18B and associated shafts (e.g., 87, 87’ in Fig. 19), i.e., the mechanism includes components rotating with the output of the MR actuator unit 20. The components are specifically selected to have a cumulative inertia associated with the rotation around a rotational axis, the cumulative inertia contributing to the inertance. The components are selected to obtain a total inertance value to be in a range of 0.2 to 2.2 times an optimal value of inertance to minimize the amplitude of transmissibility to the sprung mass at the invariant resonance frequency of the unspring mass or wheel.

[0126] Thus, the main inertias about their rotating axis of the components contributing to the inertance to take in account in the calculation may be any one or more of: in the ball screw, rotating component of the ball-screw (screw or nut), rotating components of the bearings (i.e. inner or outer race, balls, cage), rotating components of the seals, for the mechanism transmitting a force from the output of the MR actuator unit to the between sprung mass and unsprung mass. For the MR actuator unit, rotating components of the output of the MR clutch apparatuses (i.e., shaft, drums, drums holder, MR fluid), rotating gearing elements between the pinion and the MR clutches outputs, the accelerated mass of the MR fluid (though this may be said to be part of the mechanism). In a rack and pinion system, the components contributing to the inertance to take in account in the calculation are: rotating component of the pinion (not the rack), rotating components of the bearings (i.e., inner or outer race, balls, cage), rotating components of the seals, rotating components of the output of the MR clutches (i.e. shaft, drums, drums holder, MR fluid), rotating gearing elements between the pinon and the MR clutch apparatuses outputs (i.e. belt, pulley,... ), the accelerated mass of the MR fluid. In a rotating system the components contributing to the inertance to take in account in the calculation are: rotating output, rotating gears (i.e., planets, sun, ring gear if also turning), rotating internal structure, rotating components of the bearings (i.e., inner race, balls, cage), rotating components of the seals, rotating components of the output of the MR clutch apparatuses (i.e. shaft, drums, drums holder, MR fluid), the accelerated mass of the MR fluid. The method for calculating the inertance at the output should take into account that the relationship between inertance and the inertia of a component is proportional to the square of the gear ratio.

[0127] Fig. 23A shows a graphic of the force versus velocity of typical MR damper (MagneRide) and typical valve controllable damper acting in two quadrants.

[0128] Fig. 23B shows a graphic of the force vs. velocity of a typical valve controllable damper acting in two quadrants in function of the current at the input of the damper. It is to be noted that the reference scheme of Fig. 23B is reversed vs. the scheme of Fig. 22A to better fit a typical actuatorreference scheme. On a typical valve controllable damper, a relative speed is required between the two ports of the damper (one connected to the unsprung mass and the other connected to the sprung mass) in order to generate a force (i.e., you cannot have a high reaction force at 0 speed).

[0129] Fig. 24 shows a graphic of the force vs. velocity of a typical MR clutch based controllable damper acting in two quadrants. On a typical clutch based controllable damper of the proposed type, a relative speed is not required between the two ports of the damper (one connected to the unsprung mass and the other connected to the sprung mass) in order to generated a force (i.e you may generate a high reaction force at 0 speed).

[0130] Fig. 25 shows a graphic of the force vs. velocity of a typical MR clutch based controllable active suspension acting in four quadrants. The force may be applied in both positive and negative speed of the relative movement between the unsprung mass and the sprung mass. An active system may decrease the RMS sprung mass acceleration to a lower level than the semi-active system. Lower sprung mass acceleration may translate to higher comfort.

[0131] Fig. 26 shows typical vertical RMS sprung weight weighted acceleration vs unsprung weight weighted acceleration, both weighted according to ISO 2631 filter of Fig. 13, for a semi-active suspension system of the type of Fig. 21 A and an active suspension system of the type of Fig. 21 B.

[0132] Fig. 27 shows the schematic of a typical quarter car model.

[0133] Fig. 28 shows the equations when an inerter or intrinsic inertance is added to the equations of motion and state equations are rederived. Fig. 29 shows a 3D PSD map of an active suspension using a MR actuator unit for various inertance values when simulated to get the sI r transfer function. The 3D map shows that the inerter effect on dynamics is best understood by looking at the problem from an inertance point of view, and not from a frequency point-of-view as standard in vibrations. There is a critical inertance value that minimizes the ZsIZr transfer function, at about 3-6 kg for the vehicle studied (see Fig. 32 parameters). The effect is active at all frequencies, even on the two resonance modes, showing a reduction of -20dB at all frequencies as seen on Fig. 30, that depicts the PSD graphic of an active suspension using a MR actuator unit for various inertance values. The critical inertance behavior is not a resonance problem, it is a transmissibility problem. Looking at the equations of motion of Fig. 31 , the Zs equation of motion becomes decoupled from the motion of the unsprung mass, Zu, when the coefficient in front of the Zu term becomes zero. After some algebra, this happens when:

[0134] The transmissibility problem is a perfect (180 degrees) out-of-phase behavior between the spring force and the inerter force, and this across all frequencies. The effect on the amplitude is not a perfect cancellation, but a partial cancellation as seen on the Bode plot of Fig. 32.

[0135] The same attenuation effect at the critical inertance is seen on Fig. 33 when damping is added at low frequencies. However, around the 2nd mode, adding damping curves to the amplitude map moves the critical inertance values (red line) around the undamped value.

[0136] Adding damping increases the transmissibility at high frequencies and reduces the effect of the inerter. Thus, when using the critical inertance, the first resonance mode is attenuated by - 15dB, while the second resonance mode (wheel invariant resonance frequency or wheel hop mode) is attenuated by -2dB, in contrast to the -20dB global attenuation of the no-damping case. The result of the combined effect of the damping and the inertance may be seen on the graphics of Fig. 33 and Fig. 34 where the red line shows a decrease of inertance for around 5kg inertance at the wheel vs no inertance, or higher inertance. The value calculated from the variable of Fig. 35 indicates a Js value of 4.75kg of inertance.

[0137] Fig. 38 shows the amplitude of transmissivity to the sprung mass at the unsprung mass invariant resonance frequency (wheel hop), in which the minimum value of inertance, i.e. , for lowest amplitude, is around 5 kg of inertance. This optimum value of inertance may be used as reference value of inertance for the setting of a total inertance value of the cumulative inertia of the rotating components affecting the inertance. The total inertance value should be set based on the lower value of transmissivity to the sprung mass. In accordance with the present invention, the total inertance value can be set at around 0.5dB reduction, which may correspond to about 0.2x of the reference value of inertance, and may be up to 2.2x of the reference value of inertance. For the case of a BMW vehicle (merely given as an example), merely used as an example, it corresponds to a total inertance value of to 0.95kg to 10.45kg at the wheel.

[0138] Fig. 39 shows the wheel ratio or suspension ratio for a double-wishbone suspension type. The wheel ratio is the ratio between the wheel movement and the actuator movement. In the shown example, the wheel ratio is 0.6. For such a wheel ratio, the inertance at the wheel vs the inertance at the actuator is following the formula Jsw =where Jsw is the inertance at the wheel and N is the wheel ratio . In essence, the square term in the reflected inertia formula (Jsw =accounts for the combined effect of the gear ratio on both speed and force (or torque), giving an accurate picture of the inertance the wheel experience due to the actuator inertance. For the BMW example, the optimal inertance at the actuator would be 4.75 / (0.6)2= 13.2kg and the corresponding window of good inertance to 0.2x 13.2kg = 2.63kg up to 2.2x 13.2kg = 29.04kg.

[0139] In some of the embodiments, a ball screw may be used to convert the linear movement to „ .2 a rotary movement as shown in Figs. 16A and 16B. The formula Js = Jrp j where Jrp is the inertia of the rotating part (or parts) in kg*m2p is the pitch of the ball screw, the screw, or the roller screw element expressed in meter and Js is the equivalent inertance in kg.

[0140] According to Fig. 40, for an actuator composed of a motor 21 , powering a MR clutch apparatus 10 similar to the one of Fig. 1 the main components contributing to the inertance are the driven member 11 that has a one or more concentric annular drums 16, also known as output drums, mounted to an output drum support 17. All those components will contribute to the inertance. In addition, a second MR clutch apparatus 10’ is also connected to the same output 11 so the driven member 1 T that has a one or more concentric annular drums 16’, mounted to an output drum support 17’ will also contribute to the inertance. Also contributing to the inertance will be the ball screw itself.Other components like bearing, sensors, only to name a few may also contribute to the inertance of the actuator. It is the sum of the individual inertance calculated at the output that is important to adjust to meet the wheel invariant resonance frequency.

[0141] Referring to Fig. 41 , a suspension system with set inertance in accordance with the present disclosure is illustrated, with a rack and pinion assembly similar to the one of Fig. 20. In Fig. 41 , there is a MR fluid actuator unit that may have a single motor 21 and a single MR clutch apparatus 10, though there could be mode. In a variant, the single MR clutch apparatus 10 is used with a pinion 203 on the structural link 201. The MR clutch apparatus 10 may act as a MR fluid brake by providing braking of the movement of the structural link 201 in the unbiased direction by applying a force on rack portion 204. The reaction force of the MR actuator unit may be transmitted by the structural link 412 through a rotating pivot or bearing (not shown) that is attached to the output of MR clutch apparatus 10, letting the output rotate. The motor 21 may be a bi-directional motor in any of the embodiments described herein. The output member of the MR clutch apparatus 10 may be connected to another linear rack using a gear 410 in order to change the movement ratio between the rack 201 and the floating rack 411 . If a 1 :1 ratio is desired, the floating rack 411 may be meshed directly to the pinion 203. In this configuration, the floating rack 411 that may be guided by guiding elements for translation, such that the floating rack 41 1 may contribute to increase the inertance of the MR fluid actuator. The inertance of this linear component needs to be taken in account when tuning the total inertance of the actuator and will contribute to the inertance between mu and ms. Therefor

[0142] e, in the active suspension systems described herein, there is at least one MR actuator unit. The MR actuator unit has components rotating according to the relative movement between the sprung and the unsprung mass. The components have a cumulative inertia associated with the rotation around a rotational axis, the cumulative inertia contributing to the inertance. The components are selected to obtain a total inertance value to be in a range of 0.2 to 2.2 times an optimal value of inertance to minimize the amplitude of transmissibility to the sprung mass at the wheel invariant resonance frequency.

[0143] The active suspension system described herein may be that found at one of the wheels of the vehicle. A vehicle may therefore have more than one of the suspension system of the present disclosure. The suspension system may generally be described as a suspension system comprising: a suspension member operatively connected to a sprung mass and to an unsprung mass, the unsprung mass having an invariant resonance frequency relative to the sprung mass; at least one MR actuator unit configured to be positioned between the sprung mass and the unsprung mass, the at least one MR actuator unit including a torque source, and at least one MR clutch apparatus having an input operatively coupled to the torque source, and an output, the at least one MR clutch apparatus controllable to transmit a variable amount of torque between the input and the output; a mechanism between the output and one of the sprung mass and the unsprung mass, the mechanism configured to transmit a force from the output between the sprung mass and the unsprung mass; wherein at least the output has at least one rotating component rotating to transmit the force between the sprung and the unsprung mass; wherein the at least one rotating component has a cumulative inertia associatedwith a rotation around a rotational axis, the cumulative inertia contributing to a total inertance value of the suspension system; and wherein the total inertance value is in a range of 0.2 to 2.2 times a reference value of inertance to minimize an amplitude of transmissibility to the sprung mass at the invariant resonance frequency.

[0144] In a variant, the suspension system may be described as A suspension system comprising: a suspension member operatively connected to a sprung mass and to an unsprung mass, the unsprung mass having an invariant resonance frequency; at least one MR actuator unit configured to be positioned between the sprung mass and the unsprung mass, the at least one MR actuator unit including a torque source, and at least one MR clutch apparatus having an input operatively coupled to the torque source, and an output, the at least one MR clutch apparatus controllable to transmit a variable amount of torque between the input and the output; a mechanism between the output and one of the sprung mass and the unsprung mass, the mechanism configured to transmit a force from the output between the sprung mass and the unsprung mass; wherein at least the output has at least one component rotating to transmit the force between the sprung and the unsprung mass; wherein the at least one component has a cumulative inertia, the cumulative inertia contributing to a total inertance value of the suspension system; and wherein the total inertance value is in a range of 0.2 to 2.2 times a reference value of inertance to minimize an amplitude of transmissibility to the sprung mass at the wheel invariant resonance frequency. This suspension system may include translating member(s) that contribute to the cumulative inertia.

Claims

CLAIMS:1 . A suspension system comprising: a suspension member operatively connected to a sprung mass and to an unsprung mass, the unsprung mass having an invariant resonance frequency relative to the sprung mass; at least one MR actuator unit configured to be positioned between the sprung mass and the unsprung mass, the at least one MR actuator unit including a torque source, and at least one MR clutch apparatus having an input operatively coupled to the torque source, and an output, the at least one MR clutch apparatus controllable to transmit a variable amount of torque between the input and the output; a mechanism between the output and one of the sprung mass and the unsprung mass, the mechanism configured to transmit a force from the output between the sprung mass and the unsprung mass; wherein at least the output has at least one rotating component rotating to transmit the force between the sprung and the unsprung mass; wherein the at least one rotating component has a cumulative inertia associated with a rotation around a rotational axis, the cumulative inertia contributing to a total inertance value of the suspension system; and wherein the total inertance value is in a range of 0.2 to 2.2 times a reference value of inertance to minimize an amplitude of transmissibility to the sprung mass at the invariant resonance frequency.

2. The system according to claim 1 , wherein the torque source of the at least one MR actuator unit is at least one motor.

3. The system according to claim 1 , wherein the torque source of the at least one MR actuator unit is a connection to a frame, whereby the at least one MR actuator unit is a motorless brake.

4. The system according to claim 1 , including multiple of the MR clutch apparatuses being arranged in parallel, and wherein the total inertance value includes the cumulative inertias of the outputs of the MR clutch apparatuses.

5. The system according to any one of claims 1 to 4, wherein the mechanism converts a rotation of the output to a translation.

6. The system according to claim 5, wherein the mechanism is a rack and pinion.

7. The system according to claim 5, wherein the mechanism includes a ballscrew system displacing a threaded rod whereby the ballscrew and the threaded rod contribute to the total inertance value.

8. The system according to claim 7, wherein the threaded rod is located within a coil spring.

9. The system according to any one of claims 1 to 4, wherein the mechanism includes at least one structural link rotatably coupled to the output, whereby the at least one structural link contributes to the total inertance value.

10. The system according to any one of claims 1 to 9, including a reduction mechanism between the torque source and the MR clutch apparatus, whereby the reduction mechanism does not contribute to the total inertance value.

11. The system according to any one of claims 1 to 9, wherein the mechanism includes a reduction mechanism connected to the output of the MR clutch apparatus, whereby the reduction mechanism contributes to the total inertance value.

12. The system according to any one of claims 1 to 11 , wherein the suspension system includes two of the MR actuator unit, wherein the MR actuator units are antagonistic to one another.

13. The system according to claim 12, wherein the two MR actuator units are operatively connected to a common member of the mechanism.

14. The system according to claim 13, wherein the common member of the mechanism is a ball nut.

15. The system according to claim 1 , wherein the suspension system includes a floating rack operatively coupled to a pinion of the output, and wherein the total inertance value includes the inertias of the floating rack and of the pinion.

16. A suspension system comprising: a suspension member operatively connected to a sprung mass and to an unsprung mass, the unsprung mass having an invariant resonance frequency; at least one MR actuator unit configured to be positioned between the sprung mass and the unsprung mass, the at least one MR actuator unit including a torque source, and at least one MR clutch apparatus having an input operatively coupled to the torque source, and an output, the at least one MR clutch apparatus controllable to transmit a variable amount of torque between the input and the output; a mechanism between the output and one of the sprung mass and the unsprung mass, the mechanism configured to transmit a force from the output between the sprung mass and the unsprung mass; wherein at least the output has at least one component rotating to transmit the force between the sprung and the unsprung mass;wherein the at least one component has a cumulative inertia, the cumulative inertia contributing to a total inertance value of the suspension system; and wherein the total inertance value is in a range of 0.2 to 2.2 times a reference value of inertance to minimize an amplitude of transmissibility to the sprung mass at the wheel invariant resonance frequency.

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