PATENT DOCUMENT

Publication Number: US-11065931-B1
Application Number: US-201816129984-A
Country: US
Kind Code: B1

Title: Active suspension system

Abstract:
A suspension system includes a primary actuator, an inertial actuator, and a controller. The primary actuator applies force between a sprung mass and an unsprung mass of a vehicle to control movement therebetween. The inertial actuator applies force between the unsprung mass and a reaction mass to damp movement of the unsprung mass. The inertial actuator has a threshold capacity. The controller controls the primary actuator and the inertial actuator. The controller determines a required damping of the movement of the unsprung mass, and apportions the required damping between the primary actuator and the inertial actuator.

Claims:
What is claimed is: 
     
       1. A suspension system for a vehicle comprising:
 a primary actuator for applying force between a sprung mass and an unsprung mass of the vehicle to control movement therebetween; 
 an inertial actuator for applying force between the unsprung mass and a reaction mass to damp movement of the unsprung mass at a natural frequency of the unsprung mass, the inertial actuator having a capacity threshold; and 
 a control system that controls the force applied by the primary actuator and the force applied by the inertial actuator to damp the unsprung mass at the natural frequency according to the capacity threshold; 
 wherein the control system determines whether the capacity threshold of the inertial actuator will be exceeded by performing a required damping with the inertial actuator without the primary actuator, and if the capacity threshold will be exceeded, the control system controls the inertial actuator and the primary actuator to cooperatively damp the unsprung mass at the natural frequency. 
 
     
     
       2. The suspension system according to  claim 1 , wherein to determine whether the capacity threshold will be exceeded, the control system determines a predicted state of the inertial actuator according to the required damping, and compares the predicted state to the capacity threshold. 
     
     
       3. The suspension system according to  claim 2 , wherein the predicted state is a predicted amount of mechanical energy to be stored by the inertial actuator, and the capacity threshold is an energy storage capacity threshold. 
     
     
       4. The suspension system according to  claim 3 , wherein the control system determines the predicted amount of mechanical energy to be stored according to a position of the reaction mass, a velocity of the reaction mass, and an acceleration of the unsprung mass. 
     
     
       5. The suspension system according to  claim 4 , wherein the inertial actuator further includes a spring coupled to and extending between the reaction mass and the unsprung mass, and the predicted amount of mechanical energy includes kinetic energy of the reaction mass and potential energy of the spring. 
     
     
       6. The suspension system according to  claim 2 , wherein the predicted state is a predicted maximum displacement of the reaction mass, and the capacity threshold is a threshold stroke distance of the reaction mass. 
     
     
       7. The suspension system according to  claim 6 , wherein the control system determines the predicted maximum displacement according to a position of the reaction mass, a velocity of the reaction mass, and an acceleration of the unsprung mass. 
     
     
       8. The suspension system according to  claim 1 , wherein if the inertial actuator is inoperable, the control system controls the primary actuator and not the inertial actuator to damp the unsprung mass at the natural frequency. 
     
     
       9. The suspension system according to  claim 8 , wherein the capacity threshold of the inertial actuator is zero if inoperable. 
     
     
       10. The suspension system according to  claim 1 , wherein if the capacity threshold will not be exceeded, the control system controls the inertial actuator to perform the required damping without the primary actuator. 
     
     
       11. The suspension system according to  claim 1 , wherein the control system controls the primary actuator and the inertial actuator to cooperatively damp the unsprung mass according to a proportional-integral-derivative control methodology. 
     
     
       12. The suspension system according to  claim 1 , wherein the capacity threshold is one of an energy storage capacity, a stroke distance of the reaction mass, or a force capacity of the inertial actuator. 
     
     
       13. The suspension system according to  claim 1 , wherein the unsprung mass includes a wheel of the vehicle, and the sprung mass includes a vehicle body of the vehicle. 
     
     
       14. The suspension system according to  claim 1 , wherein a required damping is determined according to acceleration of the unsprung mass to damp movement of the unsprung mass at the natural frequency, and the control system controls the force applied by the primary actuator and the force applied by the inertial actuator to perform the required damping according to the capacity threshold. 
     
     
       15. The suspension system according to  claim 1 , wherein the control system further determines a required damping force of the inertial actuator for achieving the required damping, and if the control system determines that the required damping force exceeds a force capacity threshold of the inertial actuator, the control system controls the inertial actuator and the primary actuator to cooperatively damp the unsprung mass at the natural frequency. 
     
     
       16. The suspension system according to  claim 1 , wherein the unsprung mass includes a wheel of the vehicle, and the sprung mass includes a vehicle body of the vehicle;
 wherein a required damping is determined according to acceleration of the unsprung to damp movement of the unsprung mass at the natural frequency; 
 wherein if the capacity threshold will not be exceeded, the control system controls the inertial actuator to perform the required damping without the primary actuator; 
 wherein the capacity threshold is an energy storage threshold, and to determine whether the capacity threshold will be exceeded, the control system determines a predicted amount of energy to be stored by the inertial actuator according to a position of the reaction mass, a velocity of the reaction mass, and an acceleration of the unsprung mass, the predicted amount of energy including kinetic energy of the reaction mass and potential energy of a spring of the inertial actuator between the reaction mass and the unsprung mass; and 
 wherein the control system determines a required damping force of the inertial actuator for achieving the required damping, and if the control system determines that the required damping force exceeds a force capacity threshold of the inertial actuator, the control system controls the inertial actuator and the primary actuator to cooperatively perform the required damping. 
 
     
     
       17. A control system for a suspension system of a vehicle, wherein the vehicle includes a sprung mass and an unsprung mass, and the suspension system includes a primary actuator for applying force between the sprung mass and the unsprung mass and includes an inertial actuator for applying force between the unsprung mass and a reaction mass, the control system comprising:
 a position sensor for measuring a position and a velocity of the reaction mass relative to the unsprung mass; 
 an accelerometer for measuring acceleration of the unsprung mass; and 
 a controller that:
 determines, according to the acceleration, a required damping of the unsprung mass at a natural frequency of the unsprung mass; 
 determines, according to the acceleration, the position, and the velocity, a predicted state of the inertial actuator if the required damping were performed by the inertial actuator without the primary actuator; and 
 compares the predicted state to a capacity threshold of the inertial actuator, and if the predicted state exceeds the capacity threshold, controls the inertial actuator and the primary actuator to cooperatively perform the required damping. 
 
 
     
     
       18. The control system according to  claim 17 , wherein the predicted state is determined according to a current state of the inertial actuator and a predicted state change of the inertial actuator, the current state being determined according to the position and the velocity of the reaction mass, and the predicted state change being determined according to the acceleration of the unsprung mass and the velocity of the reaction mass. 
     
     
       19. The control system according to  claim 18 , wherein the capacity threshold is an energy storage capacity of the inertial actuator, the current state includes kinetic energy of the reaction mass and potential energy of a spring of the inertial actuator, and the predicted state change includes predicted work to be performed on the reaction mass to perform the required damping. 
     
     
       20. The control system according to  claim 17 , wherein if the predicted state does not exceed the capacity threshold, the controller controls the inertial actuator to perform the required damping without the primary actuator. 
     
     
       21. The control system according to  claim 17 , wherein the capacity threshold is zero if the inertial actuator is inoperable, and the controller controls the primary actuator to perform the required damping without the inertial actuator when the capacity threshold is zero. 
     
     
       22. The control system according to  claim 17 , wherein the controller further:
 determines a required damping force for the inertial actuator to perform the required damping without the primary actuator, and 
 compares the required damping force to a force capacity threshold of a secondary actuator of the inertial actuator, and if the required damping force exceeds the force capacity threshold, controls the inertial actuator and the primary actuator to cooperatively perform the required damping. 
 
     
     
       23. A method for controlling a suspension system of a vehicle, the method comprising:
 determining, with a controller, a required damping of an unsprung mass at a natural frequency of the unsprung mass, the unsprung mass including a wheel of the vehicle; 
 determining, with the controller, whether an inertial actuator can perform an entirety of the required damping without exceeding a capacity threshold of the inertial actuator, the inertial actuator including a reaction mass and an actuator mechanism for applying force between the unsprung mass and the reaction mass; 
 controlling, with the controller, the inertial actuator and a primary actuator to cooperatively perform the required damping if the inertial actuator cannot perform the entirety of the required damping, the primary actuator being configured to apply force between the unsprung mass and a sprung mass of the vehicle. 
 
     
     
       24. The method of  claim 23 , further comprising monitoring a position and a velocity of a reaction mass of the inertial actuator and monitoring an acceleration of the unsprung mass; wherein:
 the controller determines the required damping from the acceleration; 
 the controller determines whether the inertial actuator can perform the entirety of the required damping by determining a predicted state of the inertial actuator according to the position of the reaction mass, the velocity of the reaction mass, and the acceleration of the unsprung mass, and determines whether the predicted state exceeds the capacity threshold of the inertial actuator; 
 the controller controls the primary actuator and the inertial actuator to cooperatively provide the required damping if the capacity threshold is determined to be exceeded by the predicted state; and 
 the controller controls the inertial actuator to perform the entirety of the required damping if the capacity threshold is determined to not be exceeded by the predicted state. 
 
     
     
       25. The method of  claim 24 , wherein the capacity threshold is an energy storage capacity of the inertial actuator, and the predicted state is an amount of mechanical energy stored by the inertial actuator. 
     
     
       26. The method of  claim 24 , further comprising:
 determining, with the controller, a required damping force of the inertial actuator to achieve the required damping, and whether the required damping force exceeds a force capacity threshold of the inertial actuator; 
 controlling, with the controller, the inertial actuator and the primary actuator to cooperatively perform the required damping if the required damping force exceeds the force capacity threshold.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application Claims priority to and the benefit of U.S. Provisional Application No. 62/559,165, filed Sep. 15, 2017, and U.S. Provisional Application No. 62/559,190, filed Sep. 15, 2017, the entire disclosures of which are incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to suspension systems for vehicles and, in particular, active suspension systems. 
     BACKGROUND 
     Road vehicles include suspension systems that support a body of the vehicle on road surfaces over which the vehicles travel. The suspension system controls vertical movement of tire and wheel assemblies relative to the body due to road disturbances, so as to maintain contact of the tire and wheel assemblies with the road surface and to provide comfort to passengers in the vehicle body. Vertical movements of the unsprung mass due to road disturbances generally occur in a low frequency (e.g., around 3 Hz), which may be referred to primary ride. Additional vertical movements of the unsprung mass may occur in a higher frequency range due to dynamic characteristics of the unsprung mass (e.g., stiffness of the tire), which may be referred to as secondary ride or wheel hop. Typically, movements of the unsprung mass in the low and high frequency ranges are damped by passive fluid dampers, which extend and transfer force between the unsprung mass and the vehicle body. 
     SUMMARY 
     Disclosed herein are implementations of suspension assemblies and suspension actuator assemblies. In one implementation, a suspension actuator assembly includes a first actuator and a second actuator. The first actuator selectively applies a first force between an unsprung mass and a sprung mass of a vehicle to control movement therebetween. The second actuator selectively applies a second force between the unsprung mass and a reaction mass to damp movement of the unsprung mass. The second actuator is coupled to the first actuator to form the suspension actuator assembly as a singular unit. 
     In another implementation, a suspension assembly includes a suspension arm, a tire and wheel assembly, and a suspension actuator assembly. The suspension arm is pivotably coupleable to a vehicle body that forms a sprung mass. The tire and wheel assembly is coupled to the suspension arm to cooperatively form an unsprung mass. The suspension actuator assembly coupleable to the vehicle body and is coupled to the suspension arm. The suspension actuator assembly includes a first ball screw actuator and a second ball screw actuator. The first ball screw actuator includes a first motor, a first ball nut rotatable by the first motor, and a first shaft received by the first ball nut and axially movable relative thereto with rotation of the first ball nut by the first motor. The second ball screw actuator includes a second motor, a second ball nut rotatable by the second motor, and a second shaft received by the second ball nut and axially movable relative thereto with rotation of the second ball nut by the second motor. The second motor is coupled to the first motor in a fixed coaxial arrangement. The first ball screw actuator and the second ball screw actuator are operable to control movement between the vehicle body and the suspension arm, and are further operable to move the first motor and the second motor cooperatively as a reaction mass to damp movement of the unsprung mass. 
     In another implementation, a suspension assembly includes a suspension arm, a tire and wheel assembly, and a suspension actuator assembly. The suspension arm is pivotably coupleable to a vehicle body that forms a sprung mass. The tire and wheel assembly is coupled to the suspension arm to cooperatively form an unsprung mass. The suspension actuator assembly coupleable to the vehicle body and is coupled to the suspension arm. The suspension actuator assembly forms a ball screw actuator for controlling movement between the vehicle body and the suspension arm and forms an electromagnetic linear actuator for controlling movement between the suspension arm and a reaction mass. 
     In another implementation, a suspension system includes a primary actuator, an inertial actuator, and a controller. The primary actuator applies force between a sprung mass and an unsprung mass of a vehicle to control movement therebetween. The inertial actuator applies force between the unsprung mass and a reaction mass to damp movement of the unsprung mass. The inertial actuator has a threshold capacity. The controller controls the primary actuator and the inertial actuator. The controller determines a required damping of the movement of the unsprung mass, and apportions the required damping between the primary actuator and the inertial actuator. 
     In another implementation, a method is provided for controlling a suspension actuator assembly having a primary actuator and an inertial actuator for damping motion of an unsprung mass. The method includes: monitoring a position of a reaction mass of the inertial actuator and monitoring an acceleration of the unsprung mass; determining required damping from the acceleration; determining a predicted state of the inertial actuator according to the required damping and the position of the reaction mass, a velocity of the reaction mass, and the acceleration of the unsprung mass; determining whether the predicted state exceeds a capacity threshold of the inertial actuator; allocating the required damping between the inertial actuator and the primary actuator if the capacity threshold is determined to be exceeded by the predicted state; and controlling the primary actuator and the inertial actuator according to the allocation to perform the required damping. 
     In one implementation, a suspension system for a vehicle includes a primary actuator, an inertial actuator, and a control system. The primary actuator applies force between a sprung mass and an unsprung mass of the vehicle to control movement therebetween. The inertial actuator applies force between the unsprung mass and a reaction mass to damp movement of the unsprung mass at a natural frequency of the unsprung mass. The inertial actuator has a capacity threshold. The control system controls the force applied by the primary actuator and the force applied by the inertial actuator to damp the unsprung mass at the natural frequency according to the capacity threshold. 
     The control system may determine whether the capacity threshold of the inertial actuator will be exceeded by performing a required damping with the inertial actuator without the primary actuator. If the capacity threshold will be exceeded, the control system may control the inertial actuator and the primary actuator to cooperatively damp the unsprung mass, such as by cooperatively performing the required damping. If the capacity threshold will not be exceeded, the control system may control the inertial actuator to perform the required damping without the primary actuator. 
     In one implementation, a control system is for a suspension system of a vehicle. The vehicle includes a sprung mass and an unsprung mass. The suspension system includes a primary actuator for applying force between the sprung mass and the unsprung mass and includes an inertial actuator for applying force between the unsprung mass and a reaction mass. The control system includes a position sensor, an accelerometer, and a controller. The position sensor measures a position and a velocity of the reaction mass relative to the unsprung mass. The accelerometer measures acceleration of the unsprung mass. The controller: determines, according to the acceleration, a required damping of the unsprung mass at a natural frequency of the unsprung mass; determines, according to the acceleration, the position, and the velocity, a predicted state of the inertial actuator if the required damping were performed by the inertial actuator without the primary actuator; and compares the predicted state to a capacity threshold of the inertial actuator. If the predicted state exceeds the capacity threshold, the controller controls the inertial actuator and the primary actuator to cooperatively perform the required damping. 
     In one implementation, a method is provided for controlling a suspension system of a vehicle. The method includes: determining, with a controller, a required damping of an unsprung mass at a natural frequency of the unsprung mass, the unsprung mass including a wheel of the vehicle; determining, with the controller, whether an inertial actuator can perform an entirety of the required damping without exceeding a capacity threshold of the inertial actuator; controlling, with the controller, the inertial actuator and a primary actuator to cooperatively perform the required damping if the inertial actuator cannot perform the entirety of the required damping. The inertial actuator includes a reaction mass and an actuator mechanism for applying force between the unsprung mass and the reaction mass. The primary actuator is configured to apply force between the unsprung mass and a sprung mass of the vehicle. 
     The method may also include monitoring a position and a velocity of a reaction mass of the inertial actuator and monitoring an acceleration of the unsprung mass. The controller may determine the required damping from the acceleration. The controller may determine whether the inertial actuator can perform the entirety of the required damping by determining a predicted state of the inertial actuator according to the position of the reaction mass, the velocity of the reaction mass, and the acceleration of the unsprung mass. The controller may determine whether the predicted state exceeds the capacity threshold of the inertial actuator. The controller may control the primary actuator and the inertial actuator to cooperatively provide the required damping if the capacity threshold is determined to be exceeded by the predicted state. The controller may control the inertial actuator to perform the entirety of the required damping if the capacity threshold is determined to not be exceeded by the predicted state. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a vehicle. 
         FIG. 2  is a schematic view of a suspension assembly connected to a vehicle body. 
         FIG. 3A  is a cross-sectional view of a suspension actuator for use in the suspension assembly shown in  FIG. 2 , the suspension actuator being shown in a first state. 
         FIG. 3B  is a cross-sectional view of the suspension actuator of  FIG. 3A  shown in a second state. 
         FIG. 4A  is a cross-sectional view of another suspension actuator for use in the suspension assembly shown in  FIG. 2 , the suspension actuator being shown in a first state. 
         FIG. 4B  is a cross-sectional view of the suspension actuator of  FIG. 4A  shown in a second state. 
         FIG. 4C  is a cross-sectional view of the suspension actuator of  FIG. 4A  shown in a third state. 
         FIG. 5A  is a cross-sectional view of another suspension actuator for use in the suspension assembly shown in  FIG. 2 , the suspension actuator being shown in a first state. 
         FIG. 5B  is a detail cross-sectional view of the suspension actuator of  FIG. 5A . 
         FIG. 5C  is a cross-sectional view of the suspension actuator of  FIG. 5A  shown in a second state. 
         FIG. 5D  is a cross-sectional view of the suspension actuator of  FIG. 5A  shown in a third state. 
         FIG. 6  is a detail cross-sectional view of another suspension actuator for use in the suspension assembly shown in  FIG. 2 , which is taken as a similar detail to  FIG. 5B  from  FIG. 5A . 
         FIG. 7  is a detail cross-sectional view of another suspension actuator for use in the suspension assembly shown in  FIG. 2 , which is taken as a similar detail to  FIG. 5B  from  FIG. 5A . 
         FIG. 8  is a detail cross-sectional view of another suspension actuator for use in the suspension assembly shown in  FIG. 2 , which is taken as a similar detail to  FIG. 5B  from  FIG. 5A . 
         FIG. 9  is a schematic view of a suspension actuator for use in the suspension assembly shown in  FIG. 2 . 
         FIG. 10  is a schematic view of a control system for use with the suspension assembly of  FIG. 2 . 
         FIG. 11  is a schematic view of a controller of the vehicle of  FIG. 1  and for controlling the suspension actuators the various other figures and for implementing the control system of  FIG. 10 . 
     
    
    
     DETAILED DESCRIPTION 
     Disclosed herein are embodiments of active suspension systems for a vehicle, which provide secondary ride control to damp or limit wheel hop. Unsprung masses of vehicles are generally formed by a wheel, a tire, and various suspension, steering, and braking components, which move relative to a vehicle body of the vehicle in a generally vertical direction. The unsprung mass has a characteristic frequency (e.g., a natural frequency), which may result in the unsprung mass resonating as a unit when force is input to the unsprung mass (e.g., by road disturbances) at or near the characteristic frequency of the unsprung mass. The characteristic frequency of the unsprung mass, which may also be referred to as a natural frequency or a wheel hop frequency, may be between approximately 5 Hz and 20 Hz, such as 10 Hz and 15 Hz, or around 12 Hz. However, the characteristic frequency may be higher or lower depending on properties of the various components forming the unsprung mass (e.g., tire stiffness, mass, material properties, among others). 
     Various embodiments of suspension systems disclosed herein include a reaction mass that is coupled to the unsprung mass and is moved (e.g., oscillated) relative thereto to damp movement of the unsprung mass in at the characteristic frequency or in a characteristic frequency range. As used herein, the term “characteristic frequency range” includes frequencies at or near the natural frequency of the unsprung mass at which force inputs may begin to induce resonance of the unsprung mass (e.g., the natural frequency+/−2 Hz, 1 Hz, 0.5 Hz, or less). Additionally, various embodiments of the suspension systems disclosed herein form a reaction mass with actuator components otherwise configured to provide primary ride control to damp or otherwise control movement of the unsprung mass relative to the sprung mass due to force input at frequencies outside the characteristic frequency range, such as in a low frequency range (e.g., below approximately 5 Hz; primary ride). Still further, a control system is provided for apportioning damping of movement in the characteristic frequency range between a secondary actuator and a primary actuator that additionally controls primary ride. 
     Referring to  FIG. 1 , a vehicle  100  generally includes a vehicle body  110 , a powertrain system  112 , an energy storage system  114 , a steering system  116 , a controller  118 , and a suspension system  120  having one or more suspension assemblies  122  (e.g., four). The vehicle  100  may additionally include a braking system (not shown). The powertrain system  112 , for example, includes one or more electric motors  112   a  operably connected, such as via a gearbox and half-shafts, to two or more tire and wheel assemblies  124  to cause rotation thereof to propel the vehicle  100  along a roadway. The energy storage system  114 , for example, includes a battery electrically connected to the powertrain system  112 , the steering system  116 , the suspension system  120 , and/or the controller  118  for supplying power thereto. The steering system  116  is connected to the tire and wheel assemblies  124  (e.g., at a front end of the vehicle) and causes pivoting thereof about substantially vertical axes for directing the vehicle in left and right directions. The controller  118  is in communication, as indicated schematically by dash-dot lines, with the various systems of the vehicle  100 , for example, including the powertrain system  112 , the energy storage system  114 , the steering system  116 , the suspension system  120 , and the braking system for control thereof. The controller  118  is discussed in further detail below with reference to  FIG. 11 . 
     The suspension system  120  may include one of the suspension assemblies  122 , such as a front left suspension assembly  122 FL, a front right suspension assembly  122 FR, a rear left suspension assembly  122 RL, and a rear right suspension assembly  122 RR. Each suspension assembly may be considered to include one of the tire and wheel assemblies  124 . 
     Referring to  FIG. 2 , the one or more suspension assemblies  122  generally includes the tire and wheel assembly  124  having a tire  224   a  and a wheel  224   b , a suspension arm  226 , a steering knuckle  228 , and a suspension actuator assembly  230  (e.g., suspension actuator assembly). The suspension arm  226  pivotably couples the tire and wheel assembly  124  to the vehicle body  110  to allow vertical motion of the tire and wheel assembly  124  relative to the vehicle body  110 . The steering knuckle  228  pivotably couples the tire and wheel assembly  124  to the suspension arm  226  to allow pivoting about an upright (e.g., generally vertical) axis of the tire and wheel assembly  124  relative to the suspension arm  226  and, thereby, the vehicle body  110 . The suspension actuator assembly  230  extends between the suspension arm  226  and the vehicle body  110  and actively controls movement of the wheel and tire assembly  224  relative to the vehicle body  110 . Portions of the suspension assembly  122  that move relative to the vehicle body  110 , along with any brake components (e.g., disk brakes located within a hub of the wheel), powertrain components (e.g., half shafts coupling a drive source to the wheel  224   b ), and steering components (e.g., the steering knuckle  228 ) may be considered to form an unsprung mass, while the vehicle body  110  may be considered to form the sprung mass. The suspension actuator assembly  230  may, thereby, be considered to extend and transfer force between the sprung mass and the unsprung mass of the vehicle  100 . The suspension actuator assembly  230 , while shown and described for illustrative purposes in one non-limiting example as extending between the suspension arm  226  and the vehicle body  110 , may extend or otherwise transfer force between any suitable portion of the unsprung mass (e.g., the suspension arm  226  or the steering knuckle  228 ) and any suitable portion of the sprung mass (e.g., the vehicle body  110  or other structure fixed thereto). Similarly, the other suspension actuator assemblies described below (e.g., suspension actuator assemblies  430 ,  530 ,  630 ,  730 ,  830 ) may extend or otherwise transfer force between the suspension arm  226  or other suitable portion of the unsprung mass (e.g., the steering knuckle  228 ) and the vehicle body  110  or other suitable portion of the sprung mass (e.g., structures fixed to the vehicle body  110 ). 
     Referring to the detail view of  FIGS. 3A-3B , the suspension actuator assembly  230  is operated to control movement between the wheel and tire assembly  224  relative to the vehicle body  110 . The suspension actuator assembly  230  is coupled at an upper end  330   a  (e.g., first end, or first or upper mount) thereof to the vehicle body  110  and at a lower end  330   b  (e.g., second end, or second or lower mount) thereof to the suspension arm  226  (or other suitable portion of the unsprung mass, such as the steering knuckle  226 ). As the wheel and tire assembly  224  moves vertically toward and away from the vehicle body  110 , the suspension actuator assembly  230 , respectively, compresses axially and extends axially (compare  FIGS. 3A and 3B  showing the suspension actuator assembly  230  in two states). The suspension actuator assembly  230  may also pivot at the upper end  330   a  and/or the lower end  330   b  as the wheel and tire assembly  224  moves relative to the vehicle body  110 . 
     The suspension actuator assembly  230  generally includes a primary actuator  332 , a spring  334 , and a secondary actuator  336 . The primary actuator  332  is configured to control movement in the low frequency range (e.g., primary ride range) by transferring loading between the unsprung mass (e.g., the tire and wheel assembly  124 ) and the sprung mass (e.g., the vehicle body  110 ), and may also be capable of damping movement of the unsprung mass in the high frequency range (e.g., secondary ride range or wheel hop range). The secondary actuator  336  is configured to damp movement of the unsprung mass in the characteristic frequency range (e.g., secondary ride or wheel hop) by transferring loading between the unsprung mass and a reaction mass. The secondary actuator  336  may also be referred to as an inertial actuator or a reaction mass actuator. The suspension actuator assembly  230  may be provided as a singular assembly, which may be installed as a singular unit to the vehicle  100 , for example, by being coupled by the upper end  330   a  and the lower end  330   b  thereof to the vehicle body  110  and the suspension arm  226 , respectively. 
     The primary actuator  332  and the spring  334  form parallel load paths between the vehicle body  110  and the suspension arm  226  to control movement therebetween. More particularly, the primary actuator  332  transfers force between the vehicle body  110  and the suspension arm  226 , and is actuable to apply force (e.g., selectively applies a first force) therebetween to resist or cause movement between the vehicle body  110  and the suspension arm  226  to control movement therebetween. For example, the primary actuator  332  may be coupled to and extend upright between the vehicle body  110  and the suspension arm  226 . 
     The primary actuator  332  is configured as linear actuator, such as a ball screw actuator that generally includes an actuator body  334   a , an electric motor  334   b , a nut  334   c , and a shaft  334   d . The actuator body  334   a  is connected at the upper end  330   a  of the suspension actuator assembly  230  to the vehicle body  110 . The electric motor  334   b  is an electric motor having a stator fixedly coupled to the actuator body  334   a  and a rotor rotatable relative thereto. The nut  334   c  is configured as a ball nut that is fixedly coupled to the rotor of the electric motor  334   b  and is threadably connected to the shaft  334   d  (e.g., having recirculating balls that engage internal threads of the nut  334   c  and external threads of the shaft  334   d ). The shaft  334   d  is rotatably fixed relative to the stator, so as to not rotate relative thereto. As alternatives to a ball screw actuator, the primary actuator  332  may be another type of linear actuator, such as an electromagnetic linear motor or direct drive linear motor (e.g., a tubular linear motor, or a planar linear motor). 
     The electric motor  334   b  is configured to apply force between the vehicle body  110  and the suspension arm  226 , which may include providing energy into the suspension assembly  122  (e.g., converting electrical energy into mechanical energy) and receiving energy therefrom (e.g., converting mechanical energy into electrical energy). When outputting energy, the electric motor  334   b  rotates the nut  334   c , which causes the shaft  334   d  to extend axially away from the actuator body  334   a  and the electric motor  334   b  or to be received axially thereby, so as to move the tire and wheel assembly  124  away from or toward, respectively, the vehicle body  110 . When receiving energy, the electric motor  334   b  is rotated by the nut  334   c  as the tire and wheel assembly  124  moves away from or toward the vehicle body  110  due to forces external to the electric motor  334   b  (e.g., from gravity, the spring  334 , and/or the road surface acting on the tire and wheel assembly  124 ). Such external forces cause the shaft  334   d  to move away from or toward the actuator body  334   a  and the electric motor  334   b  to cause rotation of the nut  334   c  and the electric motor  334   b . It should be noted that the electric motor  334   b  may receive energy, while still resisting external forces by applying a counter-torque to control movement of the tire and wheel assembly  124 . 
     The spring  334 , in parallel to the secondary actuator  336 , presses the vehicle body  110  and the suspension arm  226  away from each other. For example, the spring  334  may press upward against a portion of the primary actuator  332  connected to the vehicle body  110  and press downward against a lower portion (e.g., mount) of the secondary actuator  336  connected to the suspension arm  226 . 
     The secondary actuator  336  is a reaction mass actuator (e.g., an inertial actuator) that moves a reaction mass axially to damp movement of the unsprung mass (e.g., including the tire and wheel assembly  124 , steering knuckle  228 , etc.) in the characteristic frequency range. The secondary actuator  336  is, for example, coupled to the lower portion or mount of the secondary actuator  336 , which is connected to the suspension arm  226 . The secondary actuator  336  may be generally concentric with the spring  334  (e.g., being surrounded thereby). 
     The secondary actuator  336  may be configured as an electromagnetic linear actuator (e.g., a direct drive linear motor or a voice coil) having a housing  336   a  (e.g., body), a coil  336   b  axially fixed to the housing  336   a , and a permanent magnet  336   c  that is moved axially when electrical current is sent through the coil  336   b . Further, a mass member  336   d  is connected to the permanent magnet  336   c  to cooperatively form the reaction mass therewith, and is further suspended axially within the housing  336   a  by an upper spring  336   e  and a lower spring  336   f . The permanent magnet  336   c , the mass member  336   d , the upper spring  336   e , and the lower spring  336   f  form a combined mass-spring system, which may be tuned to the natural frequency of the unsprung mass against the road surface (e.g., formed in part by the stiffness of the tire  224   a  engaging the road surface). 
     The secondary actuator  336  is operated to damp movement of the unsprung mass in the characteristic frequency range. More particularly, the secondary actuator  336  applies force (e.g., oscillation force) between the unsprung mass (e.g., the suspension arm  226 ) and the reaction mass (e.g., the permanent magnet  336   c  and the mass member  336   d ) in a manner to damp the movement in the characteristic frequency range (e.g., by oscillating to oppose the direction of movement of the unsprung mass). Such selective force output of the secondary actuator  336  may, for example, be determined and/or controlled by the controller  118 . 
     The combined reaction mass may be approximately 12 kg and have a stroke of approximately 50 mm. The reaction mass may be, for example, approximately 30% of the unsprung mass. 
     The spring  334 , as referenced above, forms a parallel load path with the primary actuator  332  between the vehicle body  110  and the suspension arm  226 . For example, as shown, the actuator body  334   a  of the primary actuator  332  and the housing  336   a  of the secondary actuator  336  form, respectively, an upper spring seat  334   a ′ and a lower spring seat  336   a ′ against which the spring  334  bears. In one variation of the suspension actuator assembly  230 , the spring  334  may be omitted in which case the suspension system  122  may include another spring (e.g., another coil spring or an air spring) at another location (e.g., inboard of the suspension actuator assembly  230 ), which extends or otherwise transfers force between the unsprung mass (e.g., the suspension arm  226 ) and the sprung mass (e.g., the vehicle body  110 ). 
     In further embodiments discussed below, variations of the suspension actuator assembly  230  include one or more primary actuators that are operated to control primary ride, while mass of the primary actuator is moved to damp movement of the unsprung mass in the characteristic frequency range. 
     Referring to  FIGS. 4A-4C , another suspension actuator assembly  430  may be used in the suspension actuator assembly  230  in place of the suspension actuator assembly  230 . The suspension actuator assembly  430  generally includes an upper actuator  432  and a lower actuator  434 , which are cooperatively configured to control primary ride, while also damping movement of the unsprung mass in the characteristic frequency range by forming and moving a reaction mass. More particularly, the upper actuator  432  and the lower actuator  434  are configured to cooperatively control total displacement between the sprung mass (e.g., the vehicle body  110 ) and the unsprung mass (e.g., the suspension arm  226 ) to control movement therebetween in the low frequency range, while the upper actuator  432  and the lower actuator  434  are additionally configured to move relative to the suspension arm  226  such that a reaction mass formed thereby damps the movement of the unsprung mass in the characteristic frequency range. The suspension actuator assembly  430  may be provided as a singular assembly, which may be installed as a singular unit to the vehicle  100 , for example, by being coupled by an upper mount  430   a  and a lower mount  430   b  thereof to the vehicle body  110  and the suspension arm  226 , respectively. 
     The upper actuator  432  and the lower actuator  434  are in a fixed spatial relationship (e.g., fixed coaxial arrangement) to each other, for example by being connected with an actuator housing  436  (e.g., stator housing) common thereto. The upper actuator  432  and the lower actuator  434  may both be configured as linear actuators, such as the ball screw actuators generally as described above. 
     The upper actuator  432  generally includes an upper motor  432   a , an upper nut  432   b , and an upper shaft  432   c . The upper motor  432   a  includes a stator rotationally and axially fixed to an upper end  436   a  of the actuator housing  436 , and also includes a rotor that rotates relative to the stator in a constant axial position. The rotor of the upper motor  432   a  is fixed to and rotates the upper nut  432   b  to, thereby, move the upper shaft  432   c  axially relative thereto. 
     Similarly, the lower actuator  434  generally includes a lower motor  434   a , a lower nut  434   b , and a lower shaft  434   c . The lower motor  434   a  includes a stator rotationally and axially fixed to a lower end  436   b  of the actuator housing  436 , and also includes a rotor that rotates relative to the stator in a constant axial position. The rotor of the lower motor  434   a  is fixed to and rotates the lower nut  434   b  to, thereby, move the lower shaft  434   c  relative thereto. 
     The upper actuator  432  and the lower actuator  434  may be configured to cooperatively have the same or similar effective output as the primary actuator  332  described previously. For example, the upper motor  432   a  and the lower motor  434   a  may each have a torque capacity that is approximately half that of the electric motor  332   a  of the primary actuator  332 , while the upper nut  432   b , upper shaft  432   c , lower nut  434   b , and the lower shaft  434   c  have half the lead (e.g., 25 mm instead of 50 mm) and half the travel (e.g., 70 mm instead of 140 mm) of the nut  332   b  and the shaft  332   c  of the primary actuator  332 . 
     An upper end of the upper shaft  432   c  is coupled to the vehicle body  110 , such that operation of the upper actuator  432  moves the upper motor  432   a , the upper nut  432   b , and the actuator housing  436 , along with the lower motor  434   a  and the lower nut  434   b , relative to the vehicle body  110 . A lower end of the lower shaft  434   c  is coupled to the suspension arm  226 , such that movement of the lower actuator  434  moves the lower motor  434   a , the lower nut  434   b , and the actuator housing  436 , along with the upper motor  432   a  and the upper nut  432   b , relative to the suspension arm  226 . 
     An upper spring  438   a  and a lower spring  438   b  form a load path between the vehicle body  110  and the suspension arm  226 , which is parallel to a load path formed by the upper actuator  432  and the lower actuator  434  between the vehicle body  110  and the suspension arm  226 . For example, the upper spring  438   a  may press upward against the upper mount  430   a , which is in turn coupled to the vehicle body  110 , and downward against an upper spring seat  436   a ′ formed by the actuator housing  436 . The lower spring  438   b  may press downward against the lower mount  430   b , which is in turn coupled to the suspension arm  226 , and upward against a lower spring seat  436   b ′ formed by the actuator housing  436 . 
     In operation, the upper actuator  432  and the lower actuator  434  of the suspension actuator assembly  430  are cooperatively operated to control movement between the vehicle body  110  and the suspension arm  226  to control primary ride (i.e., movement therebetween in the low frequency range). For example, the upper actuator  432  and the lower actuator  434  may each be operated to selectively apply force to resist or cause movement between the vehicle body  110  and the suspension arm  226  in directions toward and away from each other. This may be referred to as a primary ride control mode. When controlling primary ride, the upper spring  438   a  and the lower spring  438   b  transfer load between the vehicle body  110  (i.e., the sprung mass) and the suspension arm  226  (i.e., the unsprung mass) in series. 
     The upper actuator  432  and the lower actuator  434  are further cooperatively operated to apply force between a reaction mass and the suspension arm  226  (i.e., unsprung mass) to damp movement of the unsprung mass in the characteristic frequency range. This may be referred to as a wheel hop control mode. The reaction mass is cooperatively formed the upper motor  432   a , the upper nut  432   b , the lower motor  434   a , the lower nut  434   b , and the actuator housing  436 , which are moved (e.g., oscillated) in unison relative to the suspension arm  226  to damp movement thereof in the characteristic frequency range. When damping movement of the unsprung mass in the characteristic frequency range, the upper spring  438   a  and the lower spring  438   b  transfer force from the vehicle body  110  and the suspension arm  226 , respectively, to the reaction mass in parallel with the upper actuator  432  and the lower actuator  434 . 
     As a further advantage, upon inoperability of the upper actuator  432  or the lower actuator  434  (e.g., failure of one of the motors  432   a ,  434   a  thereof) to selectively provide force between the unsprung mass and the sprung mass, the other of the upper actuator  432  or the lower actuator  434  is still operable to selectively apply force between the sprung mass and the unsprung mass to control motion therebetween (e.g., to provide primary ride control in some capacity even if reduced). 
     The upper spring  438   a  and the lower spring  438   b  may have the same spring rate. Alternatively, the lower spring  438   b  may have a higher spring rate than the upper spring  438   a , so as to lessen the force transferred via the upper spring  438   a  to the vehicle body  110  from movement (e.g., oscillation) of the reaction mass, such that less disturbance is experienced by passengers in the vehicle body  110 . Instead or additionally, the upper actuator  432  and the lower actuator  434  may be controlled to offset or damp the oscillating force transferred via the upper spring  438   a  to the vehicle body  110  when operating in the wheel hop damping mode. 
     Still further, the upper actuator  432  may not include the upper spring  438   a  but instead include another spring that transfers force between the vehicle body  110  and the suspension arm  226 . For example, the other spring may be compressed between the upper mount  430   a  and the lower mount  430   b . As a result, oscillation forces from moving the reaction mass to damp movement in the characteristic frequency range are not transmitted from the reaction mass via a spring to the vehicle body  110 . 
     For illustration purposes,  FIG. 4B  shows the suspension actuator assembly  430  in a compressed state with a lesser distance between the vehicle body  110  and the suspension arm  226  as compared to  FIG. 4A , which reflects operation of the upper actuator  432  and the lower actuator  434  in the primary ride control mode, thereby functioning as a primary actuator.  FIG. 4C  illustrates the suspension actuator assembly  430  having the same distance between the vehicle body  110  and the suspension arm  226  as compared to  FIG. 4A , but with the combined mass being biased toward the suspension arm  226 . This reflects operation of the upper actuator  432  and the lower actuator  434  in the wheel hop control mode, thereby functioning as a reaction mass actuator to damp movement of the unsprung mass in the characteristic frequency range. 
     Referring to  FIGS. 5A-5D , another suspension actuator assembly  530  may be used in the suspension actuator assembly  230 . The suspension actuator assembly  530  generally includes a stator assembly  534 , a rotor assembly  536  (e.g., rotor-nut assembly), a housing  538 , a shaft  540 , and a primary spring  542 . The suspension actuator assembly  530  is configured to function as both a primary actuator, which transfers loading between the sprung mass and the unsprung mass for damping low frequency movement therebetween, and a reaction mass actuator, which applies forces between the unsprung mass and a reaction mass formed by a functional component of the primary actuator (e.g., the stator assembly  534 ). The suspension actuator assembly  530  may be provided as a singular assembly, which may be installed as a singular unit to the vehicle  100 , for example, by being coupled by the housing  538  (or a mount thereof) and a lower mount  544  thereof to the vehicle body  110  and the suspension arm  226 , respectively. 
     The stator assembly  534  and the rotor assembly  536  cooperatively form an electric motor  530   a , which operates the primary actuator in the form of a ball screw actuator for primary ride control, and also form an electromagnetic linear actuator  530   b , which operates the reaction mass actuator for damping movement of the unsprung mass in the characteristic frequency range. The stator assembly  534  and the rotor assembly  536 , thus, may be arranged such that the electric motor  530   a  and the electromagnetic linear actuator  530   b  are arranged generally concentrically, which may allow for a lesser axial length than if the primary actuator and the reaction mass actuator were instead arranged axially adjacent to each other. The stator assembly  534  is rotatably fixed and axially movable relative to the housing  538 , for example, via a sliding splined connection. The rotor assembly  536  is axially fixed and rotatable relative to the housing  538 . The electric motor  530   a  may also be referred to as a primary actuator mechanism, while the electromagnetic linear actuator  530   b  may also be referred to as a secondary actuator mechanism. 
     The primary spring  542  forms a parallel load path to the actuator  532  between the vehicle body  110  and the suspension arm  226 . For example, the primary spring  542  may generally surround the housing  538  and press upward against a circumferential spring seat  538   a  thereof, while also pressing downward against a lower mount  544 . The lower mount  544  is in turn connected to the suspension arm  226 . 
     The stator assembly  534  generally includes an outer winding  534   a , an inner winding  534   b , and an annular member  534   c . The outer winding  534   a  forms the stator of an electric motor  530   a , while the inner winding  534   b  forms the coil of the electromagnetic linear actuator  530   b . The annular member  534   c  is rotatably fixed and axially movable relative to the housing  538  and the shaft  540  and has coupled thereto the outer winding  534   a  and the inner winding  534   b . This allows transfer of torque from the housing  538  and/or the shaft  540  to the rotor assembly  536  to operate the ball screw portion of the suspension actuator assembly  530  for primary ride control, while being movable axially damp movement of the unsprung mass in the characteristic frequency range. 
     The annular member  534   c  generally includes an outer circumferential wall  534   d , an inner circumferential wall  534   e , and a radial wall  534   f  extending radially therebetween. The outer circumferential wall  534   d  and the inner circumferential wall  534   e  are generally cylindrical and concentric with each other and the shaft  540 , and define a cavity  534   g  therebetween. The outer winding  534   a  is coupled to an inner surface of the outer circumferential wall  534   d  and the inner winding  534   b  is coupled to an outer surface of the inner circumferential wall  534   e , so as to face each other and into the cavity  534   g  therebetween. An outer surface of the outer circumferential wall  534   d  forms the rotatably fixed and axially movable connection with the housing  538  (e.g., via a sliding splined connection, such as with a ball spline). An inner surface of the inner circumferential wall may also form another rotatably fixed and axially movable connection with the shaft  540  (e.g., via another sliding splined connection, such as with a ball spline). As a result, the annular member  534   c  and, thereby, the stator assembly  534  is rotatable fixed relative to the housing  538  and the shaft  540 , while being movable axially relative thereto. 
     The rotor assembly  536  generally includes an outer magnet  536   a , an inner magnet  536   b , an annular member  536   c , and a nut portion  536   d  (e.g., ball nut or ball nut portion). The outer magnet  536   a , along with the outer winding  534   a  of the stator assembly  534 , cooperatively form the electric motor  530   a  for applying torque to the nut portion  536   d  for controlling movement between the vehicle body  110  and the suspension arm  226  for primary ride control (compare  FIG. 5C  to  FIG. 5A ). The inner magnet  536   b , along with the inner winding  534   b  of the stator assembly  534 , cooperatively form the electromagnetic linear actuator, which moves the stator assembly  534  axially as a reaction mass to damp movement of the unsprung mass in the characteristic frequency range (compare  FIG. 5D  to  FIG. 5A ). 
     The annular member  536   c  forms a circumferential wall  536   e  and the nut portion  536   d . The annular member  536   c  is rotatable and axially fixed relative to the housing  538 , for example, with a bearing  546  (depicted schematically). The nut portion  536   d  is configured as a ball nut of a ball screw actuator, and as torque is applied to the nut portion  536   d  as part of the rotor assembly  536 , the nut portion  536   d  engages the shaft  540  to cause or prevent relative movement therebetween. The nut portion  536   d  may be formed integrally with the annular member  536   c  (as shown) or may be formed separately and coupled thereto. 
     The annular member  536   c  forms a circumferential wall  536   e  that is received in the cavity  534   g  between the outer circumferential wall  534   d  and the inner circumferential wall  534   e  of the annular member  534   c  of the stator assembly  534 . The outer magnet  536   a  (e.g., formed by one or more permanent magnets) is coupled to an outer surface of the circumferential wall  536   e , so as to be arranged within a magnetic field produced by the outer winding  534   a  of the rotor assembly  536 . The outer winding  534   a  and the outer magnet  536   a , thereby, cooperatively form the electric motor  530   a , which rotates the rotor assembly  536 , including the nut portion  536   d , relative to the housing  538  and the shaft  540 . The inner magnet  536   b  (e.g., formed by one or more permanent magnets) is coupled to an inner surface of the circumferential wall  536   e , so as to be arranged within another magnetic field produced by the inner winding  534   b  of the rotor assembly  536 . The inner winding  534   b  and the inner magnet  536   b , thereby, cooperatively form the electromagnetic linear actuator  530   b  (e.g., voice coil), which moves the stator assembly  534  axially within the cavity  534   g  of the rotor assembly  536 . 
     The stator assembly  534  is further supported by a secondary spring  548 , which presses upward against a lower portion of the annular member  534   c  and downward against the lower mount  544 , which forms a spring seat against which the primary spring  542  additionally bears. The secondary spring  548 , the reaction mass formed by the stator assembly  534 , and the electromagnetic linear actuator  530   b  (e.g., formed by the inner winding  534   b  and the inner magnet  536   b ) cooperatively form a reaction mass actuator, which may be tuned according to the natural frequency of the unsprung mass. 
     Axial lengths (e.g., axial winding lengths) of the outer winding  534   a  and the inner winding  534   b  are greater than axial lengths (e.g., axial magnet lengths) of the outer magnet  536   a  and the inner magnet  536   b , respectively. This allows outer magnet  536   a  and the inner magnet  536   b  to remain in the magnetic fields, respectively, produced by the outer winding  534   a  and the inner winding  534   b  as the stator assembly  534  is moved axially by the electromagnetic linear actuator  530   b  to damp movement of the unsprung mass occurring at the characteristic frequency thereof. This allows continued operation of the electric motor  530   a  for operating the ball screw actuator for primary ride control and of the electromagnetic linear actuator  530   b  for linear force output for damping movement of the unsprung mass in the characteristic frequency range. The outer winding  534   a  and the inner winding  534   b  may, for example, have axial lengths that are greater than axial lengths of the outer magnet  536   a  and the inner magnet  536   b , respectively, by distances equal to or greater than a stroke (e.g., axial movement) that the stator assembly  534 , as the reaction mass, is movable relative to the rotor assembly  536 . 
     Referring to  FIG. 6 , a suspension actuator assembly  630  is configured as a variation of the suspension actuator assembly  530 . Common elements of the suspension actuator assembly  630  are referred to with common reference numerals of the suspension actuator assembly  530  in the figures and are not discussed in further detail below. The suspension actuator assembly  630  includes an actuator  632  that forms an electric motor  630   a  and an electromagnetic linear actuator  630   b  (e.g., voice coil). The actuator  632  includes a stator assembly  634  and a rotor assembly  636 . The stator assembly  634  includes an outer winding  634   a  and an inner winding  634   b  connected to an annular member  534   c  that is configured as described previously. The rotor assembly  636  includes an outer magnet  636   a  and an inner magnet  636   b  connected to an annular member  536   c  and a nut portion  536   d  that are configured as described previously. The electric motor  630   a  may also be referred to as a primary actuator mechanism, while the electromagnetic linear actuator  630   b  may also be referred to as a secondary actuator mechanism. 
     Axial magnet lengths of the outer magnet  636   a  and the inner magnet  636   b  of the rotor assembly  636  are greater than axial winding lengths of the outer winding  634   a  and the inner winding  634   b , respectively, of the stator assembly  634 . These relative axial lengths allow the outer magnet  636   a  and the inner magnet  636   b  of the rotor assembly  636  to remain within the magnetic fields produced by the other winding  634   a  and the inner winding  634   b , respectively, of the stator assembly  634  as the stator assembly  634  moves axially to maintain torque for primary ride control and linear force output for damping movement of the unsprung mass in the characteristic frequency range. Each of the axial magnet lengths may, for example, be greater than the axial winding lengths by a distance equal to or greater than a stroke distance of the stator assembly  634  (i.e., the distance that the stator assembly  634  may move relative to the rotor assembly  636  when damping movement of the unsprung mass occurring at the characteristic frequency). 
     Comparing the electric motor  530   a  and the electric motor  630   a  with common output capacities (e.g., torque capacities) and mass, the electric motor  630   a  has efficiency advantages but lesser mass advantages. More particularly, by having magnet lengths that are greater than the axial winding lengths, the electric motor  630   a  may operate more efficiently as compared to the electric motor  530   a  by not producing excess magnetic fields with the outer winding  634   a  and the inner winding  634   b  by not extending axially beyond the outer magnet  636   a  and the inner magnet  636   b . However, with the outer magnet  636   a  and the inner magnet  636   b  being longer (i.e., larger) those of the electric motor  530   a , the rotor assembly  636  has a greater moment of rotational inertia that may result in lower responsiveness. Further by having the outer winding  634   a  and the inner winding  634   b  axially shorter, the stator assembly  634  may form a lower reaction mass than the stator assembly  534  and, thereby, provide less capacity for damping movement of the unsprung mass in the characteristic frequency range. 
     Referring to  FIG. 7 , a suspension actuator assembly  730  is configured as a variation of the suspension actuator assembly  530 . Common elements of the suspension actuator assembly  730  are referred to with common reference numerals of the suspension actuator assembly  530  in the figures and are not discussed in further detail below. The suspension actuator assembly  730  includes an actuator  732  that forms an electric motor  730   a  and the electromagnetic linear actuator  530   b  (described previously). A stator assembly  734  includes a series of outer windings  734   a  (e.g., three), the inner winding  534   b , and the annular member  534   c . The outer windings  734   a  are positioned axially adjacent to each other and have a cooperative axial winding length that is greater than the axial magnet length of the outer magnet  536   a  of the rotor assembly  536 . Each one of the outer windings  734   a  may have an axial winding length that is approximately equal to the axial magnet length of the outer magnet  536   a.    
     During operation, as the stator assembly  734  moves axially relative to the rotor assembly  536 , the outer windings  734   a  are configured to selectively produce magnetic fields that the outer magnet  536   a  stay within. For example, with the stator assembly  734  in a middle position, the outer magnet  536   a  is aligned with (e.g., at a common elevation with) a middle one of the outer windings  734   a . The middle one of the outer windings  734   a  is powered to generate the magnetic field in which the outer magnet  536   a  is positioned, while upper and lower ones of the outer windings  734   a  are powered off, so as to not generate the magnetic field. Similarly, when the stator assembly  734  is in a lowered position (outline shown in dashed lines), the outer magnet  536   a  is aligned with the upper one of the outer windings  734   a , which is powered to generate the magnetic field, while the middle and lower ones of the outer windings  734   a  are powered off, so as to not generate the magnetic field. When the stator assembly  734  is in a raised position (not shown), the outer magnet  536   a  is aligned with the lower one of the outer windings  734   a , which is powered to generate the magnetic field, while the middle and upper ones of the outer windings  734   a  are powered off, so as to not generate the magnetic field. 
     As the stator assembly  734  and the outer windings  734   a  move into and out of alignment with the outer magnet  536   a , one or two of the outer windings  734   a  may be powered to provide the magnetic field. For example, when relatively low torque is required from the electric motor  730   a  (e.g., for damping low frequency movement from relatively low magnitude forces), only one of the outer windings  734   a  may be powered, such that axial misalignment of the magnetic field of the powered winding  734   a  may still provide adequate torque output. When high torque is required from the electric motor  730   a  (e.g., for damping low frequency movement from relatively high magnitude forces), two of the outer windings  734   a  may be powered, such that the magnetic fields produced by the two of the outer windings  734   a  axially overlap the outer magnet  536   a  entirely. 
     Comparing the actuator  732  to the actuator  532 , the actuator  732  may operate more efficiently by selectively powering the outer windings  734   a , such that excess magnetic field produced thereby may be lessened, but requires more complex controls and/or circuitry for selectively operating the outer windings  734   a . Comparing the actuator  732  to the actuator  632 , the actuator  732  reduces the moment of inertia of the rotor assembly  536 , which may improve responsiveness of the electric motor  730   a , while also increasing the reaction mass formed by the stator assembly  734 , which may better damp movement of the unsprung mass at the characteristic frequency. 
     For each of the actuators  532 ,  632 , and  732  described previously, the arrangement of the electric motors  530   a ,  630   a ,  730   a  being radially outward of the electromagnetic linear actuators  530   b ,  630   b ,  530   b , respectively, may be switched. For example, directions of the magnetic field produced by the respective outer windings  534   a ,  634   a ,  734   a  and the respective inner windings  534   b ,  634   b ,  534   b , respectively, may be switched therebetween, such that the electromagnetic linear actuator and the linear force produced thereby are positioned radially outward of the electric motor and the torque produced thereby. 
     Referring to  FIG. 8 , a suspension actuator assembly  830  is configured as a variation of the suspension actuator assembly  530 . Rather than incorporating the electromagnetic linear actuator  530   b  for providing the damping function as a reaction mass actuator, the suspension actuator assembly  830  instead incorporates a tuned mass damper of which a stator assembly  834  functions as the moving mass. Common elements of the actuator  832  are referred to with common reference numerals in the figures and are not discussed below. 
     The suspension actuator assembly  830  includes an actuator  832  having the stator assembly  834  and a rotor assembly  836 , along with a housing  838 , the shaft  540 , the primary spring  542 , the bearing  546 , and the secondary spring  548 . The stator assembly  834  may be configured similar to the stator assembly  534 , but omits the inner winding  534   b  and may also omit at least a portion of the inner circumferential wall  534   e  of the annular members  534   c . The rotor assembly  836  may be configured similar to the rotor assembly  536  but omits the inner magnet  536   b.    
     The housing  838 , the stator assembly  834 , and the secondary spring  548  cooperatively form tuned mass damper, which is tuned according to the natural frequency of the unsprung mass. More particularly, the housing  838  defines a chamber  838   b , which contains a damping fluid  850 . As the unsprung mass, which includes the suspension arm  226  moves, the stator assembly  834  moves within the chamber  838   b  as the damping fluid  850  resists movement thereof. That is, the stator assembly  834  functions similar to a piston of a conventional fluid damper. The damper functionality may be tuned, for example, by a spring constant of the secondary spring  548  and/or fluid passing to different axial sides of the stator assembly  834  (e.g., around sides thereof and/or through one or more orifices of tunable size). 
     As is shown, the damping fluid  850  may flow into and out of the housing  838 , for example, through ports  838   c . The ports  838   c  may be tuned to provide desired damping characteristics as the damping fluid  850  flows into and out of the housing  838  therethrough. Still further, the damping fluid  850  may be a cooling liquid, which may be pumped into and out of the housing  838  to cool the stator assembly  834 . Alternatively, the damping fluid  850  may stay contained entirely within the chamber  838   b  defined by the housing  838  in which case the ports  838   c  are omitted. 
     A further variation of the actuator  832  may include an electric motor configured as the electric motor  630   a  described previously by having multiple outer windings (e.g., winding sections). 
     Referring to  FIGS. 9-10 , a control system and methodology are provided for allocating damping of movement in the characteristic frequency range between a primary actuator and an inertial actuator. Broadly speaking, the control methodology includes comparing a predicted state of the inertial actuator to a capacity threshold of the inertial actuator, and cooperatively performing the damping with the inertial actuator and the primary actuator if the predicted state exceeds the capacity threshold. 
       FIG. 9  is a schematic representing a suspension system  920 , which includes both a primary actuator  930  and an inertial actuator  940 . The primary actuator  930  and the inertial actuator  940  may be provided by any of the suspension actuator assemblies  230 ,  530 ,  630 ,  730 ,  830  described previously, or other suitable arrangement (e.g., the inertial actuator  940  being a separate device from the primary actuator  930 ). The inertial actuator  940  is coupled to an unsprung mass  912  (e.g., the tire and wheel assembly  124 , the suspension arm  226 , the steering knuckle  228 , etc.) and functions as a reaction mass actuator to damp high frequency movement of the unsprung mass  912  (e.g., wheel hop). The inertial actuator  940  is the main actuator by which the movement of the unsprung mass  912  at the characteristic frequency is damped. 
     The primary actuator  930  selectively applies force between a sprung mass  910  (e.g., the vehicle body  110 ) and the unsprung mass  912 , so as to control primary ride (e.g., roll, pitch, yaw), while also damping low frequency movement. The primary actuator  930  is additionally configured to supplement the inertial actuator  940  to damp movement at the characteristic frequency by transferring such movement to the sprung mass  910 , so as to maintain contact with the road surface during higher magnitude, high frequency movement (e.g., to provide supplemental wheel hop control). With the primary actuator  930  being capable of damping such high frequency movement, the inertial actuator  940  may be sized smaller (e.g., with reaction mass, motor output, and stroke), while the suspension system  920  is still capable of damping movement at the characteristic frequency, even at higher magnitudes, movement to maintain contact with the road surface for traction purposes. 
     As shown schematically in  FIG. 9 , the primary actuator  930  generally includes a primary actuator mechanism  932  and a spring  934 , which form parallel load paths between the sprung mass  910  and the unsprung mass  912 . The primary actuator mechanism  932  is a linear actuator, such as a ball screw actuator of one of the suspension actuator assemblies described previously. 
     The inertial actuator  940  generally includes a reaction mass  942 , a spring  944 , and a secondary actuator mechanism  946  that is a linear actuator. The secondary actuator mechanism  946  may be an electromagnetic linear actuator, such as those in the suspension actuator assemblies  230 ,  630 , and  730 , or may be a ball screw actuator, such as that in the suspension actuator assembly  530 . As referenced above, the inertial actuator  940  damps movement in the characteristic frequency range of the unsprung mass  912  by selectively applying a reaction force between the reaction mass  942  and the unsprung mass  912 . The reaction force is applied to the unsprung mass  912  in an opposite direction to movement of the unsprung mass  912  at a corresponding frequency. For example, as the unsprung mass  912  moves upward from engaging a road disturbance and downward thereafter, the reaction force may be applied to the unsprung mass  912  downward and upward, respectively. By applying the reaction force between the unsprung mass  912  and the reaction mass  942 , kinetic energy of the unsprung mass  912  is converted into mechanical energy stored by the inertial actuator  940  and electrical energy dissipated by the inertial actuator  940 . More particularly, as force is transferred by the secondary actuator mechanism  946  from the unsprung mass  912  to the reaction mass  942 , the reaction mass  942  is moved relative thereto to store the kinetic energy, the spring  944  is displaced to store the potential energy, and the secondary actuator mechanism  946  is moved to generate electrical energy that may be stored in an electrical storage component (e.g., a battery; not shown). 
     Capacity of the inertial actuator  940  to damp movement of the unsprung mass  912  may be limited by a stroke distance D stroke  of the reaction mass  942 , an energy storage capacity, and/or an output force. Required damping in the characteristic frequency range (e.g., at the natural frequency) to prevent resonance (e.g., to maintain contact between the road surface and the tire) may exceed the capacity of the inertial actuator  940 . 
     For example, the capacity of the inertial actuator  940  may result from the mass M R  and the stroke distance D stroke  of the reaction mass  942 , as well as the stiffness of the spring  944 . For lower magnitude movement of the unsprung mass  912  at the characteristic frequency, lower magnitude displacement of the reaction mass  942  is required to apply the reaction force to the unsprung mass  912  for transferring kinetic energy between the unsprung mass and the reaction mass  942  (e.g., for short movements of the unsprung mass  912 , the reaction mass  942  is moved by the secondary actuator mechanism  946  a small distance). For higher magnitude displacement of the unsprung mass  912  at the characteristic frequency, higher magnitude displacement of the reaction mass  942  is required to convert the kinetic energy between the unsprung mass  912  and the reaction mass  942  (e.g., for longer movements of the unsprung mass  912 , the reaction mass  942  is moved by the secondary actuator mechanism  946  longer distances). The stroke distance D stroke  of the reaction mass  942 , however, limits the magnitude of magnitude of displacement of the reaction mass  942  and, thereby, limits the amount of kinetic energy that may be transferred thereto from the unsprung mass  912 . Thus, the stroke distance D stroke  limits the capacity of the inertial actuator  940  to damp movement of the unsprung mass  912 . 
     Capacity of the inertial actuator  940  may also be limited by an energy storage capacity of the inertial actuator  940 , which is the amount of energy that may be stored mechanically (i.e., as kinetic energy and potential energy) by the inertial actuator  940 . The energy storage capacity E capacity  of the inertial actuator  940  is generally equal to a maximum amount of potential energy E Pcapacity , which may be stored by the spring  944 . Thus, the total energy storage capacity E capacity  is a product of the spring constant K and the stroke distance D stroke  of the reaction mass  942 , where E capacity =E Pcapacity =½×K×D stroke {circumflex over ( )}2. 
     Capacity of the inertial actuator  940  may also be limited by an output force capacity F capacity , which is the maximum force the inertial actuator  940  may apply to the unsprung mass  912 . The output force capacity F capacity  of the inertial actuator  940  is generally limited by the force that the secondary actuator mechanism  946  is able to apply to the reaction mass  942  to accelerate the reaction mass  942 . When damping the movements of the unsprung mass  912  requires output force F required  below the output force capacity F capacity , the secondary actuator mechanism  946  is capable of transferring such force between the reaction mass  942  and the unsprung mass  912 . For example, the secondary actuator mechanism  946  may resist relative motion of the reaction mass  942  and the unsprung mass  912  dissipating energy (e.g., by converting kinetic energy to electrical energy), and may assist relative motion of the reaction mass  942  and the unsprung mass  912  (e.g., by converting electrical energy to kinetic energy). However, when required damping requires output force F required  above the output force capacity F capacity , the secondary actuator mechanism  946  may be unable to transfer sufficient force between the unsprung mass  912  and the reaction mass  942  to provide required damping to maintain contact with the road surface. 
     The output force capacity F capacity  of the inertial actuator  940  may be a fixed value. Alternatively, the output force capacity F capacity  may vary depending on a state of the inertial actuator  940 . As noted above, the output force of the inertial actuator  940  to the unsprung mass  912  requires accelerating the reaction mass  942  relative to the unsprung mass  912 , which the spring  944  also applies force between. Thus, to accelerate the reaction mass  942 , the secondary actuator mechanism  946  must also displace the spring  944 . As a result, the output force from the secondary actuator mechanism  946  may differ from the overall damping force required F required  to be output by the inertial actuator  940  as a unit based on displacement of the spring  944 , for example, being greater if overcoming the spring  944  or lesser if assisted by the spring  944 . 
     Capacity of the inertial actuator  940  may be limited in other circumstances upon reduced operability or inoperability of the secondary actuator mechanism  946 , such as in transient condition (e.g., high temperature of the secondary actuator mechanism  946 , which may reduce capacity) or permanent conditions (e.g., failure, which reduce capacity to zero). 
     When the capacity of the inertial actuator  940 , as limited by the stroke distance D stroke , the energy storage capacity E capacity , and/or the output force capacity F capacity , is predicted to be exceeded if the required damping were provided only by the inertial actuator  940 , the primary actuator  930  may be utilized provide additional damping to maintain contact with the road surface. Otherwise, the reaction mass  942  may travel the entire stroke distance D stroke  (e.g., engaging end stops of the inertial actuator  940 ) and/or exceed the force capacity F capacity , which may result in reduced contact with the road surface (i.e., wheel hop occurs). Instead or additionally, when the capacity of the inertial actuator  940  is reduced due to reduced operability or inoperability, the primary actuator  930  may be utilized to provide further additional damping and/or provide all damping at the characteristic frequency. 
     Referring to  FIG. 10 , a control system  1000  is provided for allocating damping of high frequency movement between the primary actuator  930  and the inertial actuator  940 . Generally speaking, when a capacity threshold of the inertial actuator  940  is predicted to be exceeded if all required damping were to be performed by the inertial actuator  940 , the control system  1000  causes the primary actuator  930  to perform damping of the movement of the unsprung mass in the characteristic frequency range to supplement damping performed by the inertial actuator  940 . That is, the required damping in the characteristic frequency range is provided cooperatively by the primary actuator  930  and the inertial actuator  940 . The control system  1000  may be considered to include the accelerometer  912   a  and the position sensor  946   a . The control system  1000  may include various units, which include software programming, that may be implemented or executed by the controller  118  as described in further detail below with reference to  FIG. 11 . 
     In a first unit  1010 , conditions of the unsprung mass  912  and the inertial actuator  940  are monitored. More particularly, in a first subunit  1012  acceleration of the unsprung mass is determined (e.g., vertical acceleration). For example, referring to  FIG. 9 , an accelerometer  912   a  is coupled to the unsprung mass  912  (e.g., to the steering knuckle  228 ) and measures acceleration A unsprung  of the unsprung mass  912  in a generally vertical direction. In a second subunit  1014 , a relative position D reactionmass  and a velocity V reactionmass  of the reaction mass  942  are determined. For example, the secondary actuator mechanism  946  may include a position sensor  946   a  (e.g., linear encoder) from which the relative position D reactionmass  of the reaction mass  942  is determined (e.g., relative to the unsprung mass  912 ). The velocity V reactionmass  of the reaction mass  942  may be determined by comparing the relative position D reactionmass  of the reaction mass  942  at successive times, as determined with the position sensor  946   a.    
     In a second unit  1020 , a required damping is determined. The required damping is an amount of damping required to damp movement in the characteristic frequency range (e.g., at the natural frequency) to prevent or hinder resonance of the unsprung mass  912  (e.g., to maintain contact with the road surface). The required damping may be the damping force F required  required to be applied to the unsprung mass  912  by the inertial actuator  940 . The required damping force F required  is determined, for example, according to the acceleration A unsprung  of the unsprung mass  912 , as determined in the first unit  1010 . For example, the required damping may be sufficient to generate an equal and opposite moment about the pivot axis of the unsprung mass  912  relative to the vehicle body  110  by accelerating the reaction mass  942 . In one example, the moment τ unsprung  of the unsprung mass  912  is calculated from a mass M unsprung , the acceleration A unspring , and a length L unsprung  of the center of mass from the pivot axis of the unsprung mass  912 . See Equation 1 below:
 
τ unsprung   =M   unsprung   ×A   unsprung   ×L   unsprung   (1)
 
     The damping force required F required  by the inertial actuator  940  to achieve the required damping may thus be calculated as a function of a length L IA  from the pivot axis at which the inertial actuator  940  applies the reaction force to the unsprung mass  912  and the moment τ unsprung  of the unsprung mass  912 . See Equation 2 below:
 
 F   required =τ unsprung   /L   IA   (2)
 
The required damping force F required  be calculated in other manners, for example, accounting for the angle at which the inertial actuator  940  applies the reaction force to the unsprung mass  912  or according to other equations (e.g., accounting for other parameters, such as latency of the sensors and/or the secondary actuator mechanism  946 ).
 
     In a third unit  1030 , a predicted state of the inertial actuator  940  is determined if the total required damping were to be performed by the inertial actuator  940 . The predicted state may be determined from a current state of the inertial actuator  940  and a predicted state change of the inertial actuator  940 . The predicted state of the inertial actuator  940  may, for example, be a predicted amount of mechanical energy E predicted  to be stored (e.g., predicted stored energy) by the inertial actuator  940 , or may be a predicted maximum displacement D predictedmax  of the reaction mass  942  relative to the unsprung mass  912 . 
     The predicted stored energy E predicted  is an amount of energy predicted to be stored in mechanical form (i.e., kinetic energy E kinetic  of the reaction mass  942  and potential energy E potential  of the spring  944 ) at a subsequent time (e.g., t+1, where t equals the current time). The predicted energy stored E predicted  is, for example, derived from the stored energy E_stored currently stored mechanically by the inertial actuator  940 , which is the current state of the inertial actuator  940 , and a predicted change ΔE_stored of the stored energy E_stored, which is the predicted state change of the store of the inertial actuator  940 . See Equation 3 below:
 
 E   predicted   =E _stored+Δ E _stored  (3)
 
     The energy stored E_stored may be determined in a first subunit  1032 , as the sum of the kinetic energy E kinetic  of the reaction mass  942  and the potential energy E potential  of the spring  944 . See equation 4 below:
 
 E _stored= E   kinetic   +E   potential   (4)
 
     By knowing both the relative position D reactionmass  and the velocity V reactionmass  of the reaction mass  942 , the stored energy E_stored of the inertial actuator  940  may be determined regardless of the relative position D reactionmass  when the relative position D reactionmass  (e.g., relative to a static position of the spring  944 ) and the velocity V reactionmass  of the reaction mass  942  are determined. More particularly, the kinetic energy E kinetic  of the reaction mass  942  may be calculated as a function of the mass M reactionmass  of the reaction mass  942  and the velocity V reactionmass  of the reaction mass  942 . See Equation 5 below:
 
 E   kinetic =½× M   reactionmass   ×V   reactionmass {circumflex over ( )}2  (5)
 
The velocity V reactionmass  of the reaction mass  942  is received from the first unit  1010 . The potential energy E potential  of the spring  944  may be calculated in a second subunit  1034  as a function of the relative position D reactionmass  of the reaction mass  942  and the spring constant K of the spring  944 . See Equation 6 below:
 
 E   potential =½× K×D   reactionmass {circumflex over ( )}2  (6)
 
     The relative position D reactionmass  of the reaction mass  942  is received from the first unit  1010 . The predicted change ΔE_stored of the stored energy E_stored is determined according to the acceleration A unsprung  of the unsprung mass  912 . For example, the predicted change Δ E_stored may correspond to (e.g., equal) the amount of work W unsprung  (e.g., the predicted work) to be performed by the secondary actuator mechanism  946  on the reaction mass  942 , which may be calculated as a function of, the required damping force F required , and an estimated change in the relative position D reactionmass  of the reaction mass  942 , which may, for example, be estimated from the velocity V reactionmass  of the reaction mass  942  and a change of time ΔT. See Equation 7 below.
 
Δ E _stored= W   unsprung   =F   required   ×V   reactionmass   ×ΔT   (7)
 
     The predicted change ΔE_stored may be determined directly from the acceleration A unsprung  of the unsprung mass  912 , as indicated by the dashed line  1034   a  (e.g., from an equation derived from Equations 1, 2, and 7 above). Alternatively, the predicted change ΔE_stored may be determined by first calculating the required damping force F required  and, thereby, indirectly from the acceleration A unsprung  of the unsprung mass  912 , as indicated by solid line  1034   b.    
     The predicted state of the inertial actuator  940  may instead be a predicted maximum displacement D predictedmax  of the reaction mass  942 . The predicted maximum displacement D predictedmax  of the reaction mass  942  may be derived from the predicted stored energy E predicted . For example, the reaction mass  942  may be considered to experience the predicted maximum displacement D predictedmax  when the velocity V reactionmass  is zero and, thereby, the kinetic energy E kinetic  is equal to zero. Thus, the predicted maximum displacement D predictedmax  of the reaction mass  942  may be derived from the predicted stored energy E predicted  and the spring constant K of the spring  944 . See Equation 8 below:
 
 D   predictedmax =(2× E   predicted   /K ){circumflex over ( )}½  (8)
 
     In a fourth unit  1040 , it is predicted whether one or more capacities of the inertial actuator  940  will be exceeded if the total required damping force F required  were to be applied by the inertial actuator  940 . That is, it is determined whether the inertial actuator  940  can perform the required damping without the primary actuator. In a first subunit  1042 , the predicted state is compared to one or more capacity thresholds of the inertial actuator  940 . The capacity threshold may, for example, be the energy storage capacity E capacity  of the inertial actuator  940  (e.g., energy storage capacity threshold), the stroke distance D stroke  of the reaction mass  942  (e.g., threshold stroke distance), or a percentage P thereof (e.g., 80%). See Equations 9 and 10 below:
 
 E   predicted   &gt;P×E   capacity   (9)
 
 D   predictedmax   &gt;P×D   stroke   (10)
 
     If Equation 9 is satisfied, then an energy capacity threshold of the inertial actuator  940  is predicted to be exceeded. If Equation 10 is satisfied, then a stroke distance threshold is predicted to be exceeded. Note that Equation 9, Equation 10, or both may be evaluated. 
     The fourth unit  1040  may include a second subunit  1044  in which the required damping force F required  is compared to another capacity threshold (e.g., a force capacity threshold), which may be the damping force capacity F capacity  of the inertial actuator  940 , or a percentage P (e.g., 80%) thereof. See Equation 11 below:
 
 F   required   &gt;P×F   capacity   (11)
 
If Equation 11 is satisfied, then a force a capacity threshold is predicted to be exceeded. To account for reduced operability or inoperability of the inertial actuator  940 , the capacity threshold (e.g., the force capacity F capacity  and/or the percentage P) may vary depending on conditions of the inertial actuator  940  (e.g., temperature or failure). For example, upon detecting inoperability of the inertial actuator  940  (e.g., temporary or permanent failure of the secondary actuator mechanism  946 , as referenced above), the percentage P or the force capacity F capacity  may be zero.
 
     In a fifth unit  1050 , the required damping is allocated between the inertial actuator  940  and the primary actuator  930 . That is, the required damping is determined to be performed cooperatively by the primary actuator  930  and the inertial actuator  940 . If both the predicted state does not exceed the capacity threshold and the required damping force F required  does not exceed the damping force capacity F capacity , then an entirety of the required damping force F required  is allocated to the inertial actuator  940 , with no portion thereof being apportioned (e.g., offloaded) to the primary actuator  930 . That is, the inertial actuator  940  is to perform the required damping at the natural frequency without the primary actuator  930 . If the total energy E predicted  to be stored exceeds the energy storage threshold, the damping force F required  exceeds the threshold of the damping force capacity F capacity , or both, then damping a the natural frequency is performed cooperatively by the inertial actuator and primary actuator  930  (e.g., the required damping force F required  is apportioned between the inertial actuator  940  and the primary actuator  930 , for example, as an inertial actuator force F inertial  and a primary actuator force F primary , respectively). That is a portion of the required damping force F required  is allocated to the inertial actuator  940  and a remaining portion of the required damping force F required  is allocated to the primary actuator  930 . If the primary actuator  930  and/or the inertial actuator  940  act on the unsprung mass at different locations (e.g., relative to the pivot axis) and/or at different angles, the primary actuator force F primary  of the primary actuator  930  may be determined to apply an equivalent moment to the unsprung mass, while accounting for such differences. 
     The required damping force F required  may be allocated between the inertial actuator force F inertial  and the primary actuator force F primary  in different manners. For example, required damping force F required  may be allocated according to a proportional-integral-derivative methodology, which apportions the required damping force F required  between the primary actuator  930  and the inertial actuator  940  based on error between the predicted state and a threshold capacity (e.g., for energy storage and/or stroke distance) and/or based on error between the required damping force F required  and the damping force capacity F capacity  of the secondary actuator mechanism  946 . In the case of the inoperabilty of the inertial actuator  940  (e.g., the percentage P or the force capacity F capacity  is zero), no damping is performed by the inertial actuator  930 , and damping of the unsprung mass at the characteristic frequency (e.g., the required damping) is performed by the primary actuator  930  without the inertial actuator  940 . 
     In a sixth unit  1060 , the primary actuator  930  and the inertial actuator  940  are controlled according to the allocation of the required damping (e.g., the required damping force F required ) between the primary actuator force F primary  and the inertial actuator force F inertial . For example, the suspension controller  118  may send a primary control signal  1063  to the primary actuator  930  and a secondary control signal  1064  to the inertial actuator  940 , which request or cause the primary actuator  930  and the inertial actuator  940  to output the primary actuator force F primary  and the inertial actuator force F I . It should be noted that the primary actuator  930  may overlay additional force to the primary actuator  930 , so as to damp or otherwise control motion outside the characteristic frequency range (e.g., at a low frequency). As such, the primary control signal  1063  may request a combination (e.g., overlay) of the primary actuator force F primary  and the additional force. 
     A method of damping may be performed by the vehicle  100  accordance with the various units of the control system  1000 . For example, the method includes monitoring, determining required damping, determining a predicted state of the inertial actuator, determining whether capacity thresholds of the inertial actuator would be exceeded, allocating the required damping between the inertial actuator and the primary actuator, and controlling the inertial actuator and the primary actuator according to the allocation to perform the required damping. The monitoring includes monitoring the inertial actuator (e.g., the position and velocity of the reaction mass  942 ) and monitoring the unsprung mass  912  (e.g., the vertical acceleration thereof). Determining the required damping is performed according to the acceleration of the unsprung mass. Determining a predicted state of the inertial actuator is performed according to the required damping being performed only by the inertial actuator (e.g., determining a predicted amount of energy stored thereby). Determining whether performing the required damping would exceed the one or more capacity thresholds of the inertial actuator, includes comparing the predicted state to the capacity threshold. Allocating the required damping is performed according to whether the one or more capacity thresholds of the inertial actuator would be exceeded. Controlling the inertial actuator and the primary actuator according to the allocation, includes controlling the inertial actuator to perform up to an entirety of the required damping and controlling the primary actuator to performing any remaining portion of the required damping (e.g., according to a proportional, integral, derivative methodology). 
     Referring to  FIG. 11 , a hardware configuration for the controller  118 , which may implement the control system  1000  and/or otherwise control the actuators described herein, is shown. The controller  118  may include a processor  1181 , a memory  1182 , a storage device  1183 , one or more input devices  1184 , and one or more output devices  1185 . The controller  118  may include a bus  1186  or a similar device to interconnect the components for communication. The processor  1181  is operable to execute computer program instructions and perform operations described by the computer program instructions, such as the units of the control system  1000  described previously. As an example, the processor  1181  may be a conventional device such as a central processing unit. The memory  1182  may be a volatile, high-speed, short-term information storage device such as a random-access memory module. The storage device  1183  may be a non-volatile information storage device such as a hard drive or a solid-state drive. The input devices  1184  may include any input source, such as the various sensors of the suspension systems described herein (e.g., position sensors and/or accelerometers). The output devices  1185  may include any type of system or device for providing an output, such as the powertrain system  112 , the energy storage system  114 , the steering system  116 , and the suspension system  120 .

Metadata:
Filing Date: 20180913
Publication Date: 20210720
Grant Date: 20210720
Priority Date: 20170915
Inventors: KEAS, PAUL J.
HALL, JONATHAN L.
ZHOU, Kan
CARTER, TROY A.
LACKRITZ, NEAL M.
Assignee: APPLE INC
CPC Classifications: [{"code": "B60G2204/1242", "inventive": false, "first": false, "tree": "[]"}, {"code": "B60G2202/12", "inventive": false, "first": false, "tree": "[]"}, {"code": "B60G17/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "B60G2202/422", "inventive": false, "first": false, "tree": "[]"}, {"code": "B60G2400/252", "inventive": false, "first": false, "tree": "[]"}, {"code": "B60G15/065", "inventive": true, "first": false, "tree": "[]"}, {"code": "B60G2202/40", "inventive": false, "first": false, "tree": "[]"}, {"code": "B60G2600/182", "inventive": false, "first": false, "tree": "[]"}, {"code": "B60G2400/252", "inventive": false, "first": false, "tree": "[]"}, {"code": "B60G2202/422", "inventive": false, "first": false, "tree": "[]"}, {"code": "B60G2400/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "B60G17/021", "inventive": true, "first": false, "tree": "[]"}, {"code": "B60G17/01908", "inventive": true, "first": false, "tree": "[]"}, {"code": "B60G2600/182", "inventive": false, "first": false, "tree": "[]"}, {"code": "B60G17/0157", "inventive": true, "first": true, "tree": "[]"}, {"code": "B60G15/061", "inventive": true, "first": false, "tree": "[]"}, {"code": "B60G2400/202", "inventive": false, "first": false, "tree": "[]"}, {"code": "B60G2202/312", "inventive": false, "first": false, "tree": "[]"}, {"code": "B60G17/021", "inventive": true, "first": false, "tree": "[]"}, {"code": "B60G2202/12", "inventive": false, "first": false, "tree": "[]"}, {"code": "B60G17/06", "inventive": true, "first": false, "tree": "[]"}, {"code": "B60G17/01908", "inventive": true, "first": false, "tree": "[]"}, {"code": "B60G2400/102", "inventive": false, "first": false, "tree": "[]"}, {"code": "B60G2400/102", "inventive": false, "first": false, "tree": "[]"}, {"code": "B60G17/0157", "inventive": true, "first": true, "tree": "[]"}, {"code": "B60G2400/202", "inventive": false, "first": false, "tree": "[]"}, {"code": "B60G2202/40", "inventive": false, "first": false, "tree": "[]"}, {"code": "B60G2400/10", "inventive": false, "first": false, "tree": "[]"}, {"code": "B60G17/01908", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 74260981