Abstract:
A distributed active suspension control system is provided. The control system is based on a distributed, processor-based controller that is coupled to an electronic suspension actuator. The controller processes sensor data at the distributed node, making processing decisions for the wheel actuator it is associated with. Concurrently, multiple distributed controllers on a common network communicate such that vehicle-level control (such as roll mitigation) may be achieved. Local processing at the distributed controller has the advantage of reducing latency and response time to localized sensing and events, while also reducing the processing load and cost requirements of a central node. The topology of the distributed active suspension controller contained herein has been designed to respond to fault modes with fault-safe mechanisms that prevent node-level failure from propagating to system-level fault. Systems, algorithms, and methods for accomplishing this distributed and fault-safe processing are disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of International Application PCT/US2014/029654, entitled “ACTIVE VEHICLE SUSPENSION IMPROVEMENTS”, filed Mar. 14, 2014, which claims the benefit under 35 U.S.C. §119(e) of U.S. provisional application Ser. No. 61/913,644, entitled “WIDE BAND HYDRAULIC RIPPLE NOISE BUFFER”, filed Dec. 9, 2013, U.S. provisional application Ser. No. 61/865,970, entitled “MULTI-PATH FLUID DIVERTER VALVE”, filed Aug. 14, 2013, U.S. provisional application Ser. No. 61/815,251, entitled “ACTIVE SUSPENSION”, filed Apr. 23, 2013, and U.S. provisional application Ser. No. 61/789,600, entitled “ACTIVE SUSPENSION”, filed Mar. 15, 2013, the disclosures of which are incorporated by reference in their entirety. This application also claims the benefit under 35 U.S.C. §119(e) of U.S. provisional application Ser. No. 61/930,452, entitled “ELECTROHYDRAULIC SYSTEMS”, filed Jan. 22, 2014, the disclosure of which is incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     Field 
     Disclosed embodiments are related to highly-integrated, distributed networks of fault-tolerant actuator controllers for a vehicular active suspension control system. 
     Discussion of Related Art 
     Active suspension technologies for vehicular applications are generally categorized as semi-active and fully-active. Semi-active systems modulate mechanical stiffness of the damper according to changing road conditions. Fully-active systems have traditionally utilized actuators to raise or lower the vehicle&#39;s chassis allowing more control of ride quality and handling. 
     There are two primary types of fully active suspension systems: hydraulic and electromagnetic. Hydraulic-based active suspension systems typically use a high pressure pump and an electronic controller that maintain and control desired fluid flow to a hydraulic actuator. Electromagnetic-based fully active suspension systems command a force and velocity profile to a linear electric motor actuator. In both cases an actuator is directly connected to a vertically moving wheel and affects the motion of the associated wheel that is directly connected to a wheel suspension assembly. 
     Depending on the specific implementation of an active suspension, an actuator receives power and control signals from a controller and provides a force or position of the actuators. Vehicular active suspension actuators use control inputs and an external power source to produce a desired force-velocity response in at least three operational quadrants. 
     SUMMARY 
     Unlike most vehicular systems, active suspension power handling is characterized by a unique need to produce and absorb large energy spikes while delivering desired performance at acceptable cost. Furthermore, unlike most vehicular systems, suspension is not a stand-alone and independent function, it is rather a vehicle-wide function with each wheel actuated independently while having some interplay with the actual and anticipated motions of other wheels and the vehicle&#39;s body. The methods and systems disclosed herein are based on an appreciation of the needs dictated by improved vehicle dynamics, safety consideration, vehicle integration complexities and cost of implementation and ownership, as well as the limitations of existing active suspension actuators. To achieve maximum performance from a fully-active suspension actuator, a control system architecture that involves a low-latency communication network between units distributed across the vehicle body is described. 
     One objective of the present methods and systems of distributed active suspension control described herein is to improve performance of active suspension systems based on hydraulics, electromagnetics, electro-hydraulics, or other suitable systems by reducing latency and improving response time, reducing central processing requirements, and improving fault-tolerance and reliability. 
     Aspects relate to distributed, fault-tolerant controllers and distributed processing algorithms for active suspension control technologies. 
     According to one aspect, a distributed suspension control system comprises a number of active suspension actuators (which, in some embodiments, may be valveless, hydraulic, linear motor, ball screw, valved hydraulic, or other actuators) that are disposed throughout a vehicle such that each active suspension actuator is associated with a single wheel. The actuator operates by converting applied energy into motion of a wheel. In one embodiment, the actuator may comprise a multi-phase electric motor for controlling suspension activity of a wheel, and the actuator may be disposed within a wheel-well of a vehicle between the vehicle&#39;s chassis and the vehicle&#39;s wheel. The vehicle&#39;s chassis may be a chassis of any wheeled vehicle, but in at least some embodiments, the vehicle chassis is a car body, a truck chassis, or a truck cabin. Further, each actuator comprises an active suspension actuator controller operably coupled to a corresponding actuator (which, in some embodiments, may be to control torque, displacement, or force). Each controller has processing capability that executes wheel-specific and vehicle-specific algorithms, and in one embodiment, each controller may run substantially similar control algorithms such that any two distributed actuator-controller pairs may be expected to produce similar actuator outputs given the same controller inputs. Further, the active suspension control system comprising a number of actuator-controller pairs disposed throughout the vehicle also forms a network for facilitating communication, control, and sensing information among all of the controllers. The system also comprises at least one sensor which, in some embodiments, may be an accelerometer, a displacement sensor, a force sensor, a gyroscope, a temperature sensor, a pressure sensor, etc. disposed with each controller to provide vehicle chassis motion and/or vehicle wheel motion related information to the controller. The controller acts to process the sensor information and to execute a wheel-specific suspension protocol to control a corresponding wheel&#39;s vertical motions. In one embodiment, the wheel-specific suspension protocol may comprise suspension actions that facilitate keeping the vehicle chassis substantially level during at least one control mode, while maintaining wheel contact with the road surface. In another embodiment, the wheel-specific suspension protocol may comprise suspension actions that dampen wheel movement while mitigating an impact of road surface on wheel movement and consequently on the vehicle vertical motions. In one embodiment, the wheel-specific suspension protocol may measure the actuator inertia used in a feedback loop to control the single wheel motion. In one embodiment, the wheel-specific suspension protocol may comprise two algorithms, one for wheel control and the other for vehicle chassis/body control. Further the controller processes information received over the communication network from any other controller to execute a vehicle-wide suspension protocol to cooperatively control vehicle motion. In one embodiment, the vehicle-wide suspension protocol may be effected by each controller controlling the single wheel with which it is associated. Also, in one embodiment, the vehicle-wide suspension protocol may facilitate control of vehicle roll, pitch, and vertical acceleration. 
     According to another aspect, a distributed active valve system comprises a number of active suspension actuators (which, in some embodiments, may be valveless, hydraulic, linear motor, ball screw, valved hydraulic, or other actuators) that are disposed throughout a vehicle such that each active suspension actuator is associated with a single wheel. Each actuator comprises an electric motor operatively coupled to a hydraulic pump that communicates with hydraulic fluid that moves a piston of the actuator. Each actuator behaves by converting applied energy into a vertical motion of a single wheel in an overall suspension architecture. Further, each actuator comprises a separate active suspension actuator controller operably coupled to control torque/velocity to the electric motor thereby causing rotation capable of both resisting and assisting the hydraulic pump. The distributed active valve system comprising a number of actuator-controller pairs disposed throughout the vehicle also comprises a communication network for facilitating communication of vehicle control and sensing information among all of the controllers. The system also comprises at least one sensor (which, in some embodiments, may be an accelerometer, displacement sensor, force sensor, gyroscope, etc.) disposed with each controller to provide vehicle chassis motion and/or vehicle wheel motion related information to the controller with which the sensor is disposed. Each controller executes wheel-specific suspension protocols and vehicle-wide suspension protocols to cooperatively control vehicle motion. In one embodiment, wheel-specific suspension protocols may perform groundhook control of the wheel to improve damping of an unsprung wheel mass (that is, control that is adapted to maintain contact of the wheel with the ground under conditions that might otherwise results in the wheel losing contact). In one embodiment, wheel-specific suspension protocols may control the actuator at wheel frequencies. In one embodiment, vehicle-wide suspension protocols may perform skyhook control (that is, control adapted to maintain a relatively steady position of the vehicle cabin notwithstanding up and down motion of the wheels), active roll control, and/or pitch control. Further, in one embodiment vehicle-wide suspension protocols may control the actuator at body frequencies. 
     According to another aspect, a distributed active valve system comprises a number of active suspension actuators (which, in some embodiments, may be valveless, hydraulic, linear motor, ball screw, valved hydraulic, or other actuators) that are disposed throughout a vehicle such that each active suspension actuator is associated with a single wheel. Each actuator comprises a separate active suspension actuator controller, and in one embodiment, the controller may comprise a motor controller which applies torque to the active suspension system actuator. Further the distributed active valve system comprises a communication network for facilitating communication of vehicle control and sensing information among the actuator controllers. In some embodiments, the communication network may be a CAN bus, FlexRay, Ethernet, RS-485, or data-over-power-lines communication bus. The system also comprises at least one sensor (which, in some embodiments, may be an accelerometer, displacement sensor, force sensor, gyroscope, etc.) disposed with each controller to provide vehicle chassis motion and/or vehicle wheel motion related information to the controller with which the sensor is disposed. Further the active valve system comprises a localized energy storage facility for each active suspension system actuator. In one embodiment, the localized energy storage facility may be one or more capacitors operatively coupled to the controller to store electrical energy. In another embodiment, the active suspension system actuators may be capable of both consuming energy and supplying energy to the energy storage facility independently of the other actuators. The energy may be supplied by transferring energy harvested from an electric motor operating in a regenerative mode. In addition to the localized energy storage, in one embodiment, the system may comprise a centralized energy storage facility. Energy may be able to flow out from the centralized energy storage to the actuators over a power bus and energy may be able to flow into the energy storage from a vehicular high power electrical system, the vehicle primary electrical system, a DC-DC converter, or a regenerative active suspension actuator. In one embodiment of the system, each controller may be capable of independently detecting and responding to loss of power conditions, which may include providing power to the controller by harvesting power from wheel motion, supplying the harvested power to the controller, and/or applying a preset impedance on the terminals of a motor that controls the active suspension actuator. In one embodiment of the system, there may be a central vehicle dynamics controller that issues commands to the active suspension actuator controllers. In one embodiment, the actuator controllers may communicate sensor data to the central vehicle dynamics controller via the communication network, and in one embodiment, external sensors may be connected to the central vehicle dynamics controller to sense wheel movement, body movement, and vehicle state. 
     According to another aspect, a method of distributed vehicle suspension control comprises controlling a number of vehicle wheels with a number of wheel-specific active suspension actuators disposed in proximity to the wheel and responsible for the wheel&#39;s vertical motion. In one embodiment, the actuators may comprise multi-phase electric motors for controlling suspension activity of the single wheel and the actuator may be disposed within a wheel well of a vehicle between the vehicle body and the vehicle wheel. The method further comprises communicating actuator-specific suspension control information over a network that electrically connects the wheel-specific active suspension actuators. In one embodiment, the communication network may be a private network that contains a gateway to the vehicle&#39;s communication network and electronic control units. At each wheel-specific actuator the method further comprises localized sensing of motion (which, in some embodiments, is one of wheel displacement, velocity, and acceleration with respect to the vehicle chassis), and processing of the sensing to execute a wheel-specific suspension protocol to control the single vehicle wheel. Wheel velocity may be measured by sensing the velocity of an electric motor that moves in relative lockstep with the active suspension system actuator. In one embodiment, the wheel-specific suspension protocol may comprise wheel suspension actions that facilitate maintaining wheel compliance with a road surface over which the vehicle is operating while mitigating an impact of road surface based wheel movements on the vehicle. In one embodiment, the wheel-specific suspension protocol may include a measure of actuator inertia used as feedback to control the actuator. On a vehicle-wide level the method further comprises the processing of information received over the communication network from any other actuator to execute a vehicle-wide suspension protocol to cooperatively control vehicle motion. In one embodiment, the vehicle-wide suspension protocol may be effected by each controller that controls a single vehicle wheel. In one embodiment, the vehicle-wide suspension protocol may facilitate control of vehicle roll, pitch, and vertical acceleration. Further, in one embodiment of the system, the information received by the controller over the communication network may come from a central vehicle dynamics controller. According to another aspect, a fault-tolerant electronic suspension system comprises a plurality of electronic suspension dampers disposed throughout a vehicle so that each suspension damper is associated with a single wheel. In some embodiments, the electronic suspension damper is a semi-active damper or a fully active suspension actuator. Each damper comprises a separate active suspension controller. Further the fault-tolerant electronic suspension system comprises a communication network for facilitating communication of vehicle chassis control information among the controllers, and at least one sensor disposed with each controller to provide vehicle motion information and controller-specific vehicle wheel motion information to the controller. Further the fault-tolerant electronic suspension system comprises a power distribution bus that provides power to each electronic suspension controller. In one embodiment, a power distribution fault may include a bus-wide fault or an actuator-specific fault. Each electronic suspension controller is capable of independently detecting and responding to power distribution bus fault conditions by self-configuring to provide one of a preset force/velocity dynamic and a semi-active force/velocity dynamic. In one embodiment, the controller may be able to independently respond to power distribution bus fault conditions by regenerating energy harvested in the electronic suspension damper from wheel motion and facilitating the self-configuring. In one embodiment, the controller may further self-configure to provide a fully-active force/velocity dynamic. In one embodiment, the system may comprise an energy storage device operatively connected and proximal to each electronic suspension controller. 
     According to another aspect, a distributed suspension control system comprises a number of active suspension actuators (which, in some embodiments, may be valveless, hydraulic, linear motor, ball screw, valved hydraulic, or other actuators) that are disposed throughout a vehicle such that each active suspension actuator is associated with a single wheel. Further the system comprises a number of active suspension actuator controllers disposed so that active suspension actuators on a single vehicle axle share a single controller. The distributed suspension control system also comprises a communication network for facilitating communication of vehicle control and sensing information among all of the controllers. Further the system comprises at least one sensor disposed with each controller to provide vehicle chassis motion and/or vehicle wheel motion related information to the controller. Each controller processes information provided by its sensors to execute a wheel specific-suspension protocol to control the two or more wheels with which it is associated. Each controller also processes information received over the communication network from any of the other controllers to execute a vehicle-wide suspension protocol to cooperatively control vehicle motion. 
     According to another aspect, a power distribution bus and a communication link between a plurality of controller modules disposed throughout a vehicle body comprise a unified communication over power lines architecture. 
     In one embodiment, such architecture utilizes a high power impedance matching medium, capable of transmitting/receiving high-speed data via one of many commonly known RF technologies. Such communication medium may comprise a highly flexible coaxial cable with impedance matching terminations and RF baluns disposed at each power feed input to each controller module to separate data from raw DC power. An RF transformer extracts/injects data streams into the DC power feed while also attenuating low frequency noise associated with bidirectional DC power flow. 
     In another embodiment, communication packets are sent over unterminated power lines between a single DC power cable interconnecting all controllers distributed within the vehicle&#39;s wheel wells and use the vehicle&#39;s chassis as a return path. 
     It should be appreciated that the foregoing concepts, and additional concepts discussed below, may be arranged in any suitable combination, as the present disclosure is not limited in this respect. Further, other advantages and novel features of the present disclosure will become apparent from the following detailed description of various non-limiting embodiments when considered in conjunction with the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The accompanying drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures may be represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings: 
         FIG. 16-1  is an embodiment of an active suspension system topology that includes a distributed active suspension actuator and controller per wheel, power conversion and bus distribution, a communication network and gateway, energy storage, central vehicle processing, and local and central sensors. 
         FIG. 16-2  is an embodiment of an active suspension system topology that shows distributed actuator controller processors utilizing local sensors to run wheel-specific suspension protocols and a communication network for communicating wheel-specific and vehicle body information. 
         FIG. 16-3  is an embodiment of a highly-integrated, distributed active valve that includes a controller, electric motor and hydraulic pump located in fluid, a sensor interface, and a communication interface. 
         FIGS. 16-4  ( 4 A,  4 B,  4 C and  4 D) shows embodiments of communication network topologies for a four node distributed active suspension system with four distributed actuator controllers. 
         FIG. 16-5  is an embodiment of a three-phase bridge driver circuit and an electric motor with an encoder, phase current sensing, power bus, voltage bus sensing, and a power bus storage capacitor. 
         FIG. 16-6  shows an embodiment of a set of voltage operating ranges for a power bus in an active suspension architecture. 
         FIGS. 16-7  ( 7 A and  7 B) shows embodiments of open-circuit and short-circuit bus fault modes and the equivalent circuit models for the respective modes. 
     
    
    
     DETAILED DESCRIPTION 
     Disclosed herein is a distributed active suspension control system consisting of highly-integrated, distributed, fault-tolerant actuator controllers, wherein the controllers implement a suspension protocol that is split into wheel-specific and vehicle-wide suspension protocols. The advantages of the distributed nature of the methods and systems of distributed active suspension control described herein include improved system performance through reduced latency and faster response time to wheel-specific localized sensing and events, and reduced processing load requirements of a central node, freeing up vehicle-wide resources. Additionally the fault-tolerant nature of the distributed actuators and controllers improves on the reliability and safety of the prior art. 
     Referring to  FIG. 16-1 , an embodiment of an active suspension system topology is shown. In the embodiment shown in  FIG. 16-1 , the active suspension topology has four distributed active suspension actuators  16 - 100  disposed throughout the vehicle such that each actuator is associated with and proximal to a single vehicle wheel  16 - 102 . The actuators could be valveless, hydraulic, a linear motor, a ball screw, valved hydraulic, or of another actuator design. The actuators are mechanically coupled  16 - 104  to the vehicle wheel and vehicle chassis such that actuation provides displacement between the vehicle wheel and vehicle chassis. The actuators are individually controlled by separate distributed active suspension actuator controllers  16 - 106  through a control interface  16 - 112 . Further the active valve system comprises a localized energy storage facility for each active suspension system actuator. In one embodiment, the localized energy storage facility may be one or more capacitors  16 - 108  operatively coupled to the controller  16 - 106  to store electrical energy. The controller processes local sensor  16 - 110  information  16 - 140  and communication  16 - 116  received over the communication network  16 - 114  that connects all of the distributed controllers. The active suspension actuators receive electrical power from a power bus  16 - 118  through power bus distribution  16 - 120 . The distribution may be any combination of electrical wiring, fuse boxes, and connectors. 
     In the embodiment shown in  FIG. 16-1  the active suspension system has a set of components  16 - 122  that are not specifically located in a distributed manner on a per vehicle wheel basis. These components include a DC-DC switching power converter  16 - 124  that converts a vehicle battery  16 - 126 , such as the primary vehicle 12V battery, to a higher voltage for the power bus  16 - 118 . The power converter may be a bi-directional DC-DC switching power converter, which would allow it to pass energy in both directions. The power converter in this embodiment utilizes centralized energy storage  16 - 142 , such as supercapacitors or batteries, to buffer energy to the power bus. When the electrical load on the power bus exceeds the power converter&#39;s capabilities, the centralized energy storage can deliver buffered electrical energy. During periods of lighter electrical load, the power converter can recharge the energy storage in anticipation of a future heavy loading. Additionally, the centralized energy storage may serve to buffer electrical energy generated from the actuators in regenerative mode. Energy flowing out of electric motors in the actuators behaving as generators will be stored in the centralized energy storage. The stored energy may be used by the actuators or be transferred to the primary vehicle 12V battery through the power converter. The set of components  16 - 122  also includes a central vehicle dynamics controller  16 - 128  that processes external sensor information  16 - 130  through a sensor interface  16 - 132 , communications received through a communication gateway  16 - 138  from the vehicle ECU  16 - 134  over  16 - 136 , and information received over suspension&#39;s communication network  16 - 114 . The central vehicle dynamics controller is responsible for executing vehicle-wide suspension protocols that may include skyhook control, active roll control, and pitch control. 
       FIG. 16-2  shows an embodiment of wheel-specific processing in an active suspension topology. The processor  16 - 200  is a subcomponent of the distributed actuator controller  16 - 106 . The processor is typically a microcontroller, FPGA, DSP, or other embedded processor solution, capable of executing software implementing suspension protocols. In the embodiment of  FIG. 16-2 , the processor receives sensor information  16 - 140  from a three-axis accelerometer  16 - 204 , which is one example of the local sensing element  16 - 110 , and executes wheel-specific calculations  16 - 202  for a wheel-specific suspension protocols that may include groundhook control or wheel damping. The processor simultaneously receives vehicle body movement  16 - 208  and communication  16 - 116  from other distributed controller processors or a central vehicle dynamics controller over the active suspension communication network  16 - 114 . In this embodiment, the overall active suspension protocol is comprised of two sub protocols, a distributed wheel-specific suspension protocol for calculating wheel control decisions and a vehicle-wide suspension protocol for calculating vehicle-wide decisions. The advantages of dividing the protocol into these two sub protocols include the reduced latency and faster response time with which the wheel-specific control can respond to localized sensing and events, and the reduced processing load requirements of a central node in the distributed network. Thus vehicle-wide decisions such as active roll mitigation can be arbitrated and executed by multiple controllers in conjunction with one another. The distributed actuator controllers are all in communication with each other and the central vehicle controller. 
     In the embodiment shown in  FIG. 16-2 , the wheel-specific calculations may include a preset, semi-active, or fully active force/velocity dynamic. The advantage of this approach is that in the event of a communication fault whereby any of the controllers lose communication capabilities, the controller is able to provide suspension actions and does not adversely impact operation of the other controllers in this fault-tolerant distributed network. The remaining controllers in the distributed network can respond to the fault by managing the remaining nodes of the distributed communication network and the behavior of the faulty controller can be monitored through local and central sensor information. 
       FIG. 16-3  shows an embodiment of a highly integrated, active valve  16 - 300 . The active valve combines the actuator  16 - 100  and controller  16 - 106  into an integrated, fluid-filled  16 - 314  form factor that is compact and more easily disposed in close proximity to the vehicle wheel  16 - 102 . In the embodiment shown in  FIG. 16-3 , the controller  16 - 106  is electrically coupled  16 - 306  to an electric motor  16 - 308 . The electric motor is mechanically coupled  16 - 310  to the hydraulic pump  16 - 312  such that hydraulic flow through the pump results in rotation in the electric motor. Conversely, rotation of the electric motor results in hydraulic flow through the pump. In some embodiments of the methods and systems of distributed active suspension control described herein, the electric motor and hydraulic pump are in lockstep whereby position sensing of the electric motor provides displacement information of the hydraulic actuator and velocity sensing of the electric motor provides velocity information of the vehicle wheel  16 - 102 . 
     The controller in the embodiment of  FIG. 16-3  is comprised of the processor  16 - 200 , a motor controller  16 - 304 , and an analog-to-digital converter (ADC)  16 - 302 . The motor controller is an electrical circuit that receives a control input signal from the processor and drives an electrical output signal to the electric motor for control of any one of the motor&#39;s position, rotational velocity, torque, or other controllable parameter. For a multi-phase brushless DC electric motor, the motor controller has an element per phase for controlling the flow of current through that phase. The controller receives sensor information  16 - 140  and communication  16 - 116  that is used to execute wheel-specific and vehicle-wide suspension protocols. The ADC may be used to condition the sensor information into a form that this interpreted by the processor if the processor cannot do so directly. 
       FIG. 16-4  shows embodiments of communication network topologies for a four node distributed active suspension system with four distributed actuator controllers  16 - 106 . The key aspect of all network topologies is that all distributed actuators and any central vehicle dynamics controller are capable of communicating with each other.  FIG. 16-4A   16 - 400  shows a ring network topology whereby the communication  16 - 116  is passed from controller to controller with a single connection to a communication gateway  16 - 138 . A disadvantage of this topology is that it relies on the distributed nodes to relay messages around the ring, whereby a fault-tolerant controller must be designed to maintain basic forwarding capability. It also limits the bandwidth of communication between the gateway and any of the distributed nodes.  FIG. 16-4B   16 - 402  shows a network topology whereby the communication  16 - 116  to each distributed node passes through a communications gateway to the vehicle ECU. An advantage of this topology is the communication isolation provided such that the nodes are no dependent on each other in their communication to the vehicle ECU.  FIG. 16-4C   16 - 404  shows a network topology whereby each communication connection is shared by two distributed nodes. This topology may be implemented in a vehicle where both wheels on a given side, both wheels in the front or back form the two distributed nodes sharing the communication connection.  FIG. 16-4D   16 - 406  shows a shared network topology whereby every node of the distributed network is connected to the same physical interface. For each embodiment  16 - 4 A,  16 - 4 B,  16 - 4 C, and  16 - 4 D, the present methods and systems of distributed active suspension control described herein may interchange the communication gateway  16 - 138  and central vehicle dynamics  16 - 128  components, or use them both in combination, to achieve the desired suspension functionality. 
       FIG. 16-5  shows an embodiment of a three-phase bridge circuit  16 - 500  and an electric motor  16 - 310  with an encoder  16 - 502 , a power bus  16 - 506 , phase current sensing  16 - 504 , voltage bus sensing  16 - 508 , and a storage capacitor  16 - 510 . Each phase of the bridge circuit contains a half-bridge topology with two N-channel power MOSFETS  16 - 512  and its output stage for controlling the voltage on its respective motor phase. 
     A three-phase bridge circuit as shown in  FIG. 16-5  is typically driven by a set of MOSFET gate drivers capable of switching the low-side and high-side MOSFETs on and off. The gate drivers are typically capable of outputting sufficient current to quickly charge a MOSFET&#39;s gate capacitance, thereby reducing the amount of time the MOSFET spends in the triode region where power dissipation and switching losses are greatest. The gate drivers take pulse-width modulated (PWM) inputs signals from a processor running motor control software. 
     The body diode  16 - 514  on each N-channel MOSFET  16 - 512  of the three-phase bridge circuit as shown in  FIG. 16-5  plays a key role in the regenerative behavior of the circuit and distributed actuator described in the methods and systems of distributed active suspension control described herein. When the motor rotates and the MOSFETs are not driven, these body diodes act to rectify the back electromotive force (EMF) voltage generated by the motor acting as a generator. The electrical energy that is rectified can be stored in the bus storage capacitor  16 - 510  and can be used to self-power the circuit. 
       FIG. 16-6  shows an embodiment of a set of voltage operating ranges for a power bus  16 - 506  in an active suspension architecture. The voltage levels of the bus are important to the operation of the actuators and controllers. On the lowest end of the voltages shown in  FIG. 16-6 , undervoltage (UV)  16 - 602  is a threshold below which the system cannot operate. V Low    16 - 604  is a threshold that indicates a low, but still operational system. Dropping the power bus voltage below V Low  begins a fault response in preparation for a possible undervoltage shutdown. V Nom    16 - 606  indicates the center of the normal operating range  16 - 600 . This is the desired range over which to operate the electrical system. V High    16 - 608  is a threshold that indicates a high, but still operational system. Exceeding V High  and approaching the overvoltage threshold (OV)  16 - 610  begins a load dump response to remove electrical energy from the power bus and reduce the voltage. 
       FIG. 16-7  shows an embodiment of two power bus  15 - 506  fault modes, labelled as open-circuit  16 - 700  and short-circuit  16 - 702 . In the open-circuit fault mode, the power bus has become disconnected from the shared power bus of the active suspension system  16 - 118 . Under these circumstances, the actuator and controller&#39;s performance depend on the state of energy stored on the power bus and the amount of regenerative energy harvested. If the power bus voltage can remain in the normal operating range  16 - 600  based on stored and regenerated energy, the motor controller will continue to operate. In the short-circuit fault mode, the power bus has its positive and negative terminals shorted, collapsing the bus voltage. Under these circumstances, the motor controller is below the undervoltage threshold  16 - 602  and the motor performance is fixed. 
     While the present teachings have been described in conjunction with various embodiments and examples, it is not intended that the present teachings be limited to such embodiments or examples. On the contrary, the present teachings encompass various alternatives, modifications, and equivalents, as will be appreciated by those of skill in the art. Accordingly, the foregoing description and drawings are by way of example only.