Abstract:
A charging system for a high voltage battery includes a pair of contactors each electrically connected to one of positive and negative terminals of the battery and configured to enable charging of the battery when closed; and a controller programmed to generate a notification indicating that one of the contactors is welded closed based on port voltage values achieved while issuing a predetermined sequence of open and close commands to the contactors after charge completion.

Description:
TECHNICAL FIELD 
       [0001]    The present disclosure relates to systems and methods for providing direct current (DC) fast charging to a high voltage (HV) battery. 
       BACKGROUND 
       [0002]    A high voltage battery in an electrified vehicle may be recharged using either alternating current (AC) or DC charging. The vehicle may be connected to an AC power grid and receive electric energy via AC Level 1 or AC Level 2 charging using a 120-volt (V) or 240V connection, respectively. A connection to a DC charge-capable charging station may allow for recharging of the high voltage battery at various current rates, such as DC Level 1 200-450V/80 amperes (A), DC Level 2 200-450V/200 A, DC Level 3 200-450V/400 A, and so on. A DC charging session may, therefore, take less time to transfer the same amount of energy as compared with an AC charging session. 
       SUMMARY 
       [0003]    A charging system for a high voltage battery includes a pair of contactors each electrically connected to one of positive and negative terminals of the battery and configured to enable charging of the battery when closed, and a controller programmed to generate a notification indicating that one of the contactors is welded closed based on port voltage values achieved while issuing a predetermined sequence of open and close commands to the contactors after charge completion. 
         [0004]    A method for charging a high voltage battery includes commanding closed a pair of contactors each electrically connected to one of positive and negative terminals of the battery and arranged to enable charging of the battery, monitoring port voltage values between positive and negative nodes associated with the contactors while issuing a predetermined sequence of open and close commands to the contactors, and generating a notification indicating that one of the contactors is welded closed based on the port voltage values. 
         [0005]    A charging system for a high voltage battery includes a pair of contactors each electrically connected to one of positive and negative terminals of the battery, and a controller programmed to generate a notification indicating that both contactors are welded closed based on a difference between port voltage values and pack voltage values achieved upon charge completion, and a port voltage value achieved in response to a command to open the contactors after charge completion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a block diagram of a plug-in hybrid electric vehicle (PHEV) illustrating a typical drivetrain and energy storage components; 
           [0007]      FIG. 2  is a block diagram illustrating a contactor arrangement for DC fast charging; 
           [0008]      FIG. 3A  is a flowchart illustrating an algorithm for providing DC fast charging to a HV battery; 
           [0009]      FIG. 3B  is a flowchart illustrating an algorithm for performing voltage matching during DC fast charging; and 
           [0010]      FIG. 4  is a flowchart illustrating an algorithm for performing DC fast charge contactor fault detection. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Embodiments of the present disclosure are described herein. It is to be understood, however, that the disclosed embodiments are merely examples and other embodiments may take various and alternative forms. The figures are not necessarily to scale; some features could be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. As those of ordinary skill in the art will understand, various features illustrated and described with reference to any one of the figures may be combined with features illustrated in one or more other figures to produce embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. Various combinations and modifications of the features consistent with the teachings of this disclosure, however, could be desired for particular applications or implementations. 
         [0012]      FIG. 1  depicts a typical plug-in hybrid-electric vehicle (PHEV). A plug-in hybrid-electric vehicle  12 , hereinafter vehicle  12 , may comprise at least one traction battery or battery pack  14  configured to receive electric charge via a charging session at a charging station (not shown) connected to a power grid (not shown). The vehicle  12  may, for example, cooperate with electric vehicle supply equipment (EVSE)  16  of the charging station to coordinate the charge transfer from the power grid to the battery pack  14 . The power grid may include a device that harnesses renewable energy, such as a photovoltaic (PV) solar panel, or a wind turbine (not shown). 
         [0013]    The EVSE  16  may include circuitry and controls to regulate and manage the transfer of energy between the power grid and the vehicle  12 . For example, the EVSE  16  may have a charge connector for plugging into a charge port  18  of the vehicle  12 , such as via connector pins that mate with corresponding recesses of the charge port  18 . The charge port  18  may be any type of port configured to transfer power from the EVSE  16  to the vehicle  12 . As will be explained in further detail in reference to  FIG. 2 , a battery charger control module (BCCM)  38  in communication with the charge port  18  may control the charge flow between the charge port  18  and the battery pack  14 . Similarly, the EVSE  16  may include a control module (not shown) that conditions the power supplied from the EVSE  16  to provide the proper voltage and current levels to the vehicle  12 . 
         [0014]    The EVSE  16  may be designed to provide single- or three-phase AC or DC power to the vehicle  12 . Differences in the charge connector and charging protocol may exist between an AC-, a DC-, and an AC/DC-capable EVSE. The EVSE  16  may further be capable of providing different levels of AC and DC voltage including, but not limited to, Level 1 120 volt (V) AC charging, Level 2 240V AC charging, Level 1 200-450V and 80 amperes (A) DC charging, Level 2 200-450V and up to 200 A DC charging, Level 3 200-450V and up to 400 A DC charging, and so on. 
         [0015]    Time required to receive a given amount of electric charge may vary among the different charging methods. It may take several hours to charge a given battery pack using a single-phase AC charging session. The same amount of charge under similar conditions may be obtained in minutes using DC charging. The latter charging method is also referred to as DC fast charging. 
         [0016]    In one example, both the charge port  18  and the EVSE  16  may be configured to comply with industry standards pertaining to electrified vehicle charging, such as, but not limited to, Society of Automotive Engineers (SAE) J1772, J1773, J2954, International Organization for Standardization (ISO)  15118 - 1 ,  15118 - 2 ,  15118 - 3 , the German DIN Specification  70121 , and so on. In one example, the recesses of the charge port  18  may comprise 7 terminals (indicated generally with a double-headed arrow), with terminals 1 and 2 designated for Level 1 and 2 AC power exchange, terminal 3 designated for a ground connection, terminals 4 and 5 designated for control signals, and terminals 6 and 7 designated for DC charging, such as, but not limited to, Levels 1, 2, or 3 DC charging. 
         [0017]    By way of an example, terminal 4 can be used to conduct control pilot signals, and terminal 5 can be used to conduct proximity detection signals. A proximity signal may be a signal indicative of a state of engagement between the charge port  18  and the connector of the EVSE  16 . A control pilot signal, e.g., a low-voltage pulse-width modulation (PWM) signal, may be used to control the charging process. 
         [0018]    The vehicle  12  may further comprise one or more electric machines  20  mechanically connected to a hybrid transmission  22 . The electric machines  20  may be capable of operating as a motor or a generator. In addition, the hybrid transmission  22  is mechanically connected to an engine  24 . The hybrid transmission  22  is also mechanically connected to a drive shaft  26  that is mechanically connected to the wheels  28 . 
         [0019]    The electric machines  20  can provide propulsion and deceleration capability when the engine  24  is turned on or off using energy stored in the battery pack  14 . The electric machines  20  also act as generators and can provide fuel economy benefits by recovering energy that would normally be lost as heat in the friction braking system. The electric machines  20  may also provide reduced pollutant emissions since the vehicle  12  may be operated in electric mode under certain conditions. 
         [0020]    The battery pack  14  typically provides a high voltage DC output. The battery pack  14  may be electrically connected to an inverter system control (ISC)  30 . The ISC  30  is electrically connected to the electric machines  20  and provides the ability to bi-directionally transfer energy between the battery pack  14  and the electric machines  20 . In a motor mode, the ISC  30  may convert the DC output provided by the battery pack  14  to a three-phase alternating current as may be required for proper functionality of the electric machines  20 . In a regenerative mode, the ISC  30  may convert the three-phase AC output from the electric machines  20  acting as generators to the DC voltage required by the battery pack  14 . While  FIG. 1  depicts a typical plug-in hybrid electric vehicle, the description herein is equally applicable to a pure electric vehicle. For a pure electric vehicle, e.g., battery electric vehicle (BEV), the hybrid transmission  22  may be a gear box connected to the electric machine  20  and the engine  24  may not be present. 
         [0021]    In addition to providing energy for propulsion, the battery pack  14  may provide energy for other vehicle electrical systems. For example, the battery pack  14  may transfer energy to high-voltage loads  32 , such as compressors and electric heaters. In another example, the battery pack  14  may provide energy to low-voltage loads  34 , such as an auxiliary 12V battery. In such an example the vehicle  12  may include a DC/DC converter module (not shown) that converts the high voltage DC output of the battery pack  14  to a low voltage DC supply that is compatible with the low-voltage loads  34 . The various components discussed may have one or more associated controllers to control and monitor the operation of the components. The controllers may communicate via a serial bus (e.g., Controller Area Network (CAN)) or via discrete conductors. 
         [0022]    In reference to  FIG. 2 , a contactor arrangement for DC fast charging of a high-voltage battery is shown. The charge port  18  may comprise a DC gateway module (DCGM)  36  in communication with the EVSE  16 . The DCGM  36  may be configured to receive a signal indicative of a request to transfer electric energy between the EVSE  16  and the battery pack  14  via an AC or a DC charging session. 
         [0023]    The DCGM  36  may also be in communication with the BCCM  38 . The DCGM  36  may send a request to the BCCM  38  to initiate a charging session. For example, the DCGM  36  may send to the BCCM  38  via a control pilot signal terminal a signal indicative of a specific charging session type being requested by the EVSE  16 . In one example, the BCCM  38  may be configured to interpret a particular duty cycle of the PWM signal, e.g., 10%, as being indicative of a request to initiate a DC fast charging session. 
         [0024]    The battery pack  14  may comprise one or more battery cells  40 , a bussed electric center (BEC)  42 , and a battery energy control module (BECM)  44 . The battery cells  40 , e.g., electrochemical cells, may have any suitable configuration and serve to receive and store electric energy for use in operation of the vehicle  12 . Each cell may provide a same or different nominal level of voltage. The battery cells  40  may be arranged into one or more arrays, sections, or modules further connected in series or in parallel. 
         [0025]    The battery cells  40  may be electrically connected to the BEC  42  via a positive terminal  46  and a negative terminal  48 . The terminals  46 ,  48  may be of electrically conductive material, such as metal, and may have any suitable configuration. As will be described below in further detail, the BEC  42  may include a plurality of connectors and switches allowing the supply and withdrawal of electric energy to and from the battery cells  40  via a connection with the positive and negative terminals  46 ,  48 . While the battery pack  14  is described to include, for example, electrochemical battery cells, other types of energy storage device implementations, such as capacitors, are also contemplated. 
         [0026]    The BECM  44  is connected with the BEC  42  and controls the energy flow between the BEC  42  and the battery cells  40 . For example, the BECM  44  may be configured to monitor and manage temperature and state of charge of each of the battery cells  40 . In another example, the BECM  44  may command the BEC  42  to open or close a plurality of switches in response to temperature or state of charge in a given battery cell reaching a predetermined threshold. The BECM  44  may further be in communication with other vehicle controllers (not shown), such as an engine control module (ECM) and transmission control module (TCM), and may command the BEC  42  to open or close a plurality of switches in response to a predetermined signal from the other vehicle controllers. 
         [0027]    The BECM  44  may also be in communication with the BCCM  38 . For example, the BCCM  38  may send a signal to the BECM  44  indicative of a DC fast charging session request. The BECM  44  may then command the BEC  42  to open or close a plurality of switches allowing the transfer of electric energy between the EVSE  16  and the battery pack  14  via a DC fast charging session. As will be described in further detail in reference to  FIG. 3 , the BECM  44  may perform voltage matching prior to commanding the BEC  42  to open or close a plurality of switches allowing the transfer of electric energy. 
         [0028]    The BEC  42  may comprise a positive main contactor  50  electrically connected to the positive terminal  46  of the battery cells  40  and a negative main contactor  52  electrically connected to the negative terminal  48  of the battery cells  40 . In one example, closing the positive and negative main contactors  50 ,  52  allows the flow of electric energy to and from the battery cells  40 . In such an example, the BECM  44  may command the BEC  42  to open or close the main contactors  50 ,  52  in response to receiving a signal from the BCCM  38  indicative of a request to initiate or terminate a charging session. In another example, the BECM  44  may command the BEC  42  to open or close the main contactors  50 ,  52  in response to receiving a signal from another vehicle controller, e.g., ECM, TCM, etc., indicative of a request to initiate or terminate transfer of electric energy to and from the battery pack  14 . 
         [0029]    The BEC  42  may further comprise a pre-charge circuit  54  configured to control an energizing process of the positive terminal  46 . In one example, the pre-charge circuit  54  may include a pre-charge resistor  56  connected in series with a pre-charge contactor  58 . The pre-charge circuit  54  may be electrically connected in parallel with the positive main contactor  50 . When the pre-charge contactor  58  is closed the positive main contactor  50  may be open and the negative main contactor  52  may be closed allowing the electric energy to flow through the pre-charge circuit  54  and control an energizing process of the positive terminal  46 . 
         [0030]    In one example, the BECM  44  may command BEC  42  to close the positive main contactor  50  and open the pre-charge contactor  58  in response to detecting that voltage level across the positive and negative terminals  46 ,  48  reached a predetermined threshold. The transfer of electric energy to and from the battery pack  14  may then continue via the positive and negative main contactors  50 ,  52 . For example, the BEC  42  may support electric energy transfer between the battery pack  14  and the ISC  30  during either a motor or a generator mode via a direct connection to conductors of the positive and negative main contactors  50 ,  52 . 
         [0031]    In another example, the BECM  44  may enable energy transfer to the high-voltage loads  32 , such as compressors and electric heaters, via a direct connection to the positive and negative main contactors  50 ,  52 . In still another example, the BECM  44  may command energy transfer to the low-voltage loads  34 , such as an auxiliary 12V battery, via a DC/DC converter (not shown) connected to the positive and negative main contactors  50 ,  52 . 
         [0032]    For simplicity and clarity AC charging session connections between the charge port  18  and the battery pack  14  have been omitted. In one example, the main contactors  50 ,  52  in combination with the pre-charge circuit  54  may be used to transfer AC energy between the EVSE  16  and the battery pack  14 . For example, the BECM  44  may be configured to command the opening and closing of the main contactors  50 ,  52  in response to receiving a signal indicative of a request to initiate an AC charging session. 
         [0033]    The BEC  42  may further comprise a DC fast charge contactor  60  electrically connected to the positive terminal  46 . The BEC  42  may close the negative main contactor  52  and close the DC fast charge contactor  60  in response to a signal indicative of a request for a DC fast charging session. For example, the BECM  44  may command the BEC  42  to close the negative main contactor  52  and to close the DC fast charge contactor  60  in response to receiving a signal from the BCCM  38  indicative of a request for a DC fast charging session. The BECM  44  may selectively command the BEC  42  to open the negative main contactor  52  and to open the DC fast charge contactor  60  in response to receiving a notification of a DC fast charging session completion. As will be described in reference to  FIGS. 3B and 4 , the BECM  44  may be further configured to command the BEC  42  to selectively open and close the negative main contactor  52 , the DC fast charge contactor  60 , and other switches, based on a port voltage V port , e.g., voltage measured at a positive node  75  and a negative node  77 . 
         [0034]    In reference to  FIG. 3A , a control strategy  64  for charging an HV battery via DC fast charging is shown. The control strategy  64  may start at block  66  where the BECM  44  receives a signal indicative of a request to initiate a DC fast charging session from the BCCM  38 . For example, the BCCM  38  may be configured to interpret a particular duty cycle of the DCGM PWM signal, e.g., 10%, as being indicative of a request to initiate a DC fast charging session, and to relay the request to the BECM  44 . 
         [0035]    As will be described in further detail in reference to  FIG. 3B , the BECM  44  determines at block  68  whether a voltage matching fault is present. For example, the BECM  44  may determine that a voltage matching fault exists in response to determining that difference between an EVSE output voltage and a battery pack voltage is greater than a predetermined value. The BECM  44  may then terminate the DC fast charging session at block  74 . 
         [0036]    At block  70  the BECM  44  permits DC fast charge transfer between the EVSE  16  and the battery pack  14  in response to determining that the voltage matching process has been completed without faults. For example, the BECM  44  may command the BEC  42  to close the negative main contactor  52  and to close the DC fast charge contactor  60  allowing energy flow to the battery pack  14 . 
         [0037]    At block  72  the BECM  44  determines whether the DC fast charging session should be continued. For example, the BECM  44  may determine whether there has been a stop charge request, e.g., a manual stop request by a user, an automatic stop request by the EVSE  16 , and so on. The control strategy  64  may return to block  68  where the BECM  44  determines whether a voltage matching process fault is present in response to determining that the DC fast charging session should be continued, e.g., there has not been a stop charge request. 
         [0038]    At block  74  the BECM  44  terminates the DC fast charging session in response to determining at block  72  that the DC fast charging session should not be continued. For example, the BECM  44  may determine that a stop charge request, such as a manual or an automatic stop request, has been received. At this point the control strategy  64  may end. In some embodiments the control strategy  64  described in  FIG. 3A  may be repeated in response to receiving a signal indicative of a request to initiate a DC fast charging session or another request. 
         [0039]    In reference to  FIG. 3B , a control strategy  76  for performing voltage matching is shown. The control strategy may begin at block  78  where the BECM  44  receives a signal indicative of a request to initiate a DC fast charging session. At block  80  the BECM  44  requests the EVSE  16  to set output voltage to a predetermined voltage V set . In one example, the BECM  44  may request the EVSE  16  to set the output voltage level approximately equal to the voltage level of the battery pack  14 , hereinafter battery pack voltage V pack , e.g., 400V. The BECM  44  may be configured to receive battery pack voltage V pack  from a sensor (not shown) connected to the battery cells  40 . 
         [0040]    The BECM  44  determines at block  82  whether an absolute value of a difference between port voltage V port  and a predetermined voltage V set  is less than a predetermined value. In one example, the BECM  44  may be configured to determine port voltage V port  by measuring voltage between the positive node  75  and the negative node  77 . The BECM  44  terminates the DC fast charging session at block  84  in response to determining that the absolute value of the difference between port voltage V port  and a predetermined voltage V set  is greater than a predetermined value, e.g., 20V. In one example, in response to determining that the absolute value of the difference between port voltage V port  and a predetermined voltage V set  is greater than a predetermined value at block  82  and prior to terminating the DC fast charging session at block  84 , the BECM  44  may use a debouncing timer. In such an example, the BECM  44  after a predetermined period may repeat at block  82  the determining whether an absolute value of a difference between port voltage V port  and a predetermined voltage V set  is less than a predetermined value, prior to terminating the DC fast charging session. 
         [0041]    At blocks  86  and  88  the BECM  44  sends a request to the BEC  42  to close the DC fast charge contactor  60  and the negative main contactor  52 , respectively, in response to determining at block  82  that the absolute value of the difference between port voltage V port  and a predetermined voltage V set  is less than a predetermined value. While blocks  86  and  88  show that the negative main contactor  52  is closed after the DC fast charge contactor  60 , the sequence in which the DC fast charge contactor  60  and the negative main contactor  52  are closed may vary based on a given diagnostic strategy adopted by the BECM  44 . The BECM  44  at block  90  performs DC fast charging. At this point the control strategy  76  may end. In some embodiments the control strategy  76  described in  FIG. 3B  may be repeated in response to receiving a signal indicative of a request to initiate a DC fast charging session or another request. 
         [0042]    In reference to  FIG. 4 , a control strategy  100  for detecting a DC fast charging contactor fault is shown. The control strategy  100  may begin at block  102  where the BECM  44  receives a signal indicating that a DC fast charging session is complete, e.g., receives a notification of charge session completion. At block  103  the BECM  44  requests the EVSE  16  to stop converting power. For example, the BECM  44  may send a signal to the EVSE  16  via the BCCM  38  and the DCGM  36  indicative of a request to stop converting power. 
         [0043]    At block  104  the BECM  44  determines whether an absolute value of a difference between port voltage V port  and battery pack voltage V pack  is less than a predetermined value. For example, the BECM  44  may be configured to receive a port voltage value as a voltage level between the positive node  75  and the negative node  77  and configured to receive battery pack voltage V pack  as a voltage level of the battery cells  40 . The BECM  44  performs diagnostics at block  106  in response to determining that the absolute value of the difference between port voltage V port  and battery pack voltage V pack  is greater than a predetermined value. In one example, the BECM  44  may report that the absolute value of the difference between port voltage V port  and battery pack voltage V pack  is greater than a predetermined value, e.g., 20V, and may set a diagnostic trouble code (DTC). 
         [0044]    The BECM  44  commands the BEC  42  at block  108  to open both the DC fast charge contactor  60  and the negative main contactor  52  in response to determining at block  104  that the absolute value of the difference between port voltage V port  and battery pack voltage V pack  is less than a predetermined value. The BECM  44  then determines at block  110  whether port voltage V port  is less than a predetermined value. For example, the BECM  44  determines whether port voltage V port  is less than 50V in response to the command to open both the DC fast charge contactor  60  and the negative main contactor  52 . 
         [0045]    The BECM  44  determines at block  112  whether the EVSE  16  has been disconnected from the charge port  18 , i.e., a state of the EVSE  16 , in response to determining at block  110  that port voltage V port  is greater than a predetermined value, e.g., 50V. For example, the BECM  44  may determine whether the charge connector of the EVSE  16  has been unplugged from the corresponding recesses of the charge port  18 . If the BECM  44  determines that the EVSE  16  has not been disconnected, the BECM  44  at block  114  waits a predetermined period for the EVSE  16  to be disconnected. In one example, the BECM  44  may perform diagnostics if the EVSE  16  has not been disconnected after a predetermined period. The control strategy  100  may then end. 
         [0046]    The BECM  44  determines at block  116  whether port voltage V port  is less than a predetermined value in response to determining at block  112  that the EVSE  16  has been disconnected. For example, the BECM  44  determines whether port voltage V port  is less than 50V in response to determining that the EVSE  16  has been disconnected. At block  118  the BECM  44  performs diagnostics in response to determining that port voltage V port  is greater than a predetermined value. In one example, the BECM  44  may determine that the DC fast charge contactor  60  and the negative main contactor  52  have a fault, e.g., a weld fault. The control strategy  100  may then end. 
         [0047]    At block  120  the BECM  44  performs diagnostics in response to determining that port voltage V port  is less than a predetermined value after the EVSE  16  has been disconnected. In one example, the BECM  44  may determine that the EVSE  16  continued to convert power despite the BECM  44  request to stop converting. The control strategy  100  may then end. 
         [0048]    At block  124  the BECM  44 , in response to determining that port voltage V port  is less than a predetermined value, commands BEC  42  to close the DC fast charge contactor  60  leaving the negative main contactor  52  open. The BECM  44  determines at block  126  whether port voltage V port  is less than a predetermined value, e.g., 50V, in response to a command to close the DC fast charge contactor  60 , leaving the main negative contactor  52  open. The BECM  44  performs diagnostics at block  128  in response to determining that port voltage V port  is greater than a predetermined value. For example, the BECM  44  may determine that the negative main contactor  52  has a weld fault or another fault type. The control strategy  100  may then end. 
         [0049]    At block  130  the BECM  44  commands the BEC  42  to close the negative main contactor  52  and to open the DC fast charge contactor  60  in response to determining at block  126  that port voltage V port  is less than a predetermined value. At block  132  the BECM  44  determines whether port voltage V port  is less than a predetermined value. The BECM  44  may exit the control strategy  100  in response to determining that port voltage V port  is less than a predetermined value. 
         [0050]    The BECM  44  performs diagnostics at block  134  in response to determining that port voltage V port  is greater than a predetermined value, e.g., 50V. For example, the BECM  44  may determine that the DC fast charge contactor  60  has a weld fault or another type of fault and may then exit the control strategy  100 . At this point the control strategy  100  may end. In some embodiments, the control strategy  100  described in  FIG. 4  may be repeated in response to receiving a signal indicating that the DC fast charging session has been completed or another signal. 
         [0051]    The processes, methods, or algorithms disclosed herein may be deliverable to or implemented by a processing device, controller, or computer, which may include any existing programmable electronic control unit or dedicated electronic control unit. Similarly, the processes, methods, or algorithms may be stored as data and instructions executable by a controller or computer in many forms including, but not limited to, information permanently stored on non-writable storage media such as ROM devices and information alterably stored on writeable storage media such as floppy disks, magnetic tapes, CDs, RAM devices, and other magnetic and optical media. The processes, methods, or algorithms may also be implemented in a software executable object. Alternatively, the processes, methods, or algorithms may be embodied in whole or in part using suitable hardware components, such as Application Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), state machines, controllers or other hardware components or devices, or a combination of hardware, software and firmware components. 
         [0052]    The words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure. As previously described, the features of various embodiments may be combined to form further embodiments of the invention that may not be explicitly described or illustrated. While various embodiments could have been described as providing advantages or being preferred over other embodiments or prior art implementations with respect to one or more desired characteristics, those of ordinary skill in the art recognize that one or more features or characteristics may be compromised to achieve desired overall system attributes, which depend on the specific application and implementation. These attributes may include, but are not limited to cost, strength, durability, life cycle cost, marketability, appearance, packaging, size, serviceability, weight, manufacturability, ease of assembly, etc. As such, embodiments described as less desirable than other embodiments or prior art implementations with respect to one or more characteristics are not outside the scope of the disclosure and may be desirable for particular applications.