阅读说明：本技术 一种电动汽车、电机控制器及其热保护方法 (Electric automobile, motor controller and thermal protection method thereof ) 是由 杜恩利 常伟 张剑 于 2021-02-25 设计创作，主要内容包括：本申请公开了一种电动汽车、电机控制器及其热保护方法,以避免电机控制器内功率半导体器件出现热损伤。该方法包括：在电机控制器正常工作过程中,采样电机控制器内预设采样点的温度；判断电机控制器当前所处的工作模式,其中电机控制器有稳态模式、峰值模式和堵转模式三种工作模式；若所述采样点的温度超过电机控制器在当前工作模式下的过温阈值,控制电机控制器停止输出；其中电机控制器在不同工作模式下的过温阈值不同。(The application discloses an electric automobile, a motor controller and a thermal protection method thereof, which are used for avoiding thermal damage of a power semiconductor device in the motor controller. The method comprises the following steps: sampling the temperature of a preset sampling point in the motor controller in the normal working process of the motor controller; judging the current working mode of the motor controller, wherein the motor controller has three working modes, namely a steady-state mode, a peak mode and a locked rotor mode; if the temperature of the sampling point exceeds the over-temperature threshold value of the motor controller in the current working mode, controlling the motor controller to stop outputting; wherein the motor controller has different over-temperature thresholds in different operating modes.)

1. A method of thermal protection of a motor controller, comprising:

sampling the temperature of a preset sampling point in the motor controller in the normal working process of the motor controller;

judging the current working mode of the motor controller, wherein the motor controller has three working modes, namely a steady-state mode, a peak mode and a locked rotor mode;

if the temperature of the sampling point exceeds the over-temperature threshold value of the motor controller in the current working mode, controlling the motor controller to stop outputting; wherein the motor controller has different over-temperature thresholds in different operating modes.

2. The method of claim 1, wherein the determining the current operating mode of the motor controller comprises:

when the rotating speed of the motor is smaller than a rotating speed threshold value and the output current of the motor controller is larger than the locked-rotor current, judging that the motor controller enters a locked-rotor mode;

when the rotating speed of the motor is greater than or equal to the rotating speed threshold value and the output current of the motor controller is less than or equal to the rated current, or when the rotating speed of the motor is less than the rotating speed threshold value and the output current of the motor controller is less than or equal to the locked-rotor current, the motor controller is judged to enter a steady-state mode;

and when the rotating speed of the motor is greater than or equal to the rotating speed threshold value, the peak current is greater than or equal to the output current of the motor controller, and the output current of the motor controller is greater than the rated current, the motor controller is judged to enter a peak mode.

3. The method of claim 1, wherein the temperature at the sampling point is a cold plate temperature of the motor controller or a substrate temperature of a power semiconductor device in the motor controller.

4. The motor controller thermal protection method according to claim 1, wherein when the motor controller is currently in a steady-state mode, if the temperature of the sampling point is greater than a derating threshold and less than or equal to an over-temperature threshold of the motor controller in the steady-state mode, controlling the derating output of the motor controller.

5. The motor controller thermal protection method according to any one of claims 1 to 4, wherein when the motor controller is currently in a peak mode, if the temperature of the sampling point is greater than a derating threshold and less than or equal to an over-temperature threshold of the motor controller in the peak mode, controlling a derating output of the motor controller.

6. A motor controller, comprising: a temperature sensor and a central processing unit;

the central processing unit is used for controlling the temperature sensor to sample the temperature of a preset sampling point in the motor controller in the normal working process of the motor controller; judging the current working mode of the motor controller, wherein the motor controller has three working modes, namely a steady-state mode, a peak mode and a locked rotor mode; if the temperature of the sampling point exceeds the over-temperature threshold value of the motor controller in the current working mode, controlling the motor controller to stop outputting; wherein the motor controller has different over-temperature thresholds in different operating modes.

7. The motor controller of claim 6, wherein the central processor determines the current operating mode of the motor controller by:

when the rotating speed of the motor is smaller than a rotating speed threshold value and the output current of the motor controller is larger than the locked-rotor current, judging that the motor controller enters a locked-rotor mode;

when the rotating speed of the motor is greater than or equal to the rotating speed threshold value and the output current of the motor controller is less than or equal to the rated current, or when the rotating speed of the motor is less than the rotating speed threshold value and the output current of the motor controller is less than or equal to the locked-rotor current, the motor controller is judged to enter a steady-state mode;

and when the rotating speed of the motor is greater than or equal to the rotating speed threshold value, the peak current is greater than or equal to the output current of the motor controller, and the output current of the motor controller is greater than the rated current, the motor controller is judged to enter a peak mode.

8. The motor controller of claim 6, wherein the temperature sensor is mounted on a cold plate of the motor controller or on a substrate of a power semiconductor device in the motor controller for collecting a temperature of the cold plate of the motor controller or a temperature of the substrate of the power semiconductor device in the motor controller.

9. The motor controller of claim 6 wherein when the motor controller is currently in the steady state mode, the CPU is further configured to control the motor controller derate output when the temperature at the sampling point is greater than the derate threshold and less than or equal to the over-temperature threshold of the motor controller in the steady state mode.

10. The motor controller according to any one of claims 6 to 9, wherein when the motor controller is currently in the peak mode, the cpu is further configured to control the motor controller to derate the output when the temperature at the sampling point is greater than the derating threshold and equal to or less than the over-temperature threshold of the motor controller in the peak mode.

11. An electric vehicle comprising a motor controller according to any one of claims 6 to 10.

Technical Field

The invention relates to the technical field of thermal protection, in particular to an electric automobile, a motor controller and a thermal protection method thereof.

Background

The motor controller is one of the core components of an electric vehicle. The vehicle control system obtains the vehicle requirement from a vehicle control unit, obtains electric energy from a power battery pack, obtains current and voltage required by a control motor through modulation of an inverter of the vehicle control system, and provides the current and the voltage for the motor, so that the rotating speed and the torque of the motor meet the vehicle requirement.

The motor controller has various working modes, and the power semiconductor devices (such as IGBT) in the motor controller are easily thermally damaged in long-time working or large-current working conditions, so that the thermal protection of the power semiconductor devices in the motor controller is very necessary.

Disclosure of Invention

In view of the above, the present invention provides an electric vehicle, a motor controller and a thermal protection method thereof, so as to prevent a power semiconductor device in the motor controller from being thermally damaged.

A motor controller thermal protection method comprising:

sampling the temperature of a preset sampling point in the motor controller in the normal working process of the motor controller;

judging the current working mode of the motor controller, wherein the motor controller has three working modes, namely a steady-state mode, a peak mode and a locked rotor mode;

if the temperature of the sampling point exceeds the over-temperature threshold value of the motor controller in the current working mode, controlling the motor controller to stop outputting; wherein the motor controller has different over-temperature thresholds in different operating modes.

Optionally, the determining a current working mode of the motor controller includes:

when the rotating speed of the motor is smaller than a rotating speed threshold value and the output current of the motor controller is larger than the locked-rotor current, judging that the motor controller enters a locked-rotor mode;

when the rotating speed of the motor is greater than or equal to the rotating speed threshold value and the output current of the motor controller is less than or equal to the rated current, or when the rotating speed of the motor is less than the rotating speed threshold value and the output current of the motor controller is less than or equal to the locked-rotor current, the motor controller is judged to enter a steady-state mode;

and when the rotating speed of the motor is greater than or equal to the rotating speed threshold value, the peak current is greater than or equal to the output current of the motor controller, and the output current of the motor controller is greater than the rated current, the motor controller is judged to enter a peak mode.

Optionally, the temperature of the sampling point is a temperature of a cold plate of the motor controller or a temperature of a substrate of a power semiconductor device in the motor controller.

Optionally, when the motor controller is currently in the steady-state mode, if the temperature of the sampling point is greater than the derating threshold and is less than or equal to the over-temperature threshold of the motor controller in the steady-state mode, controlling derating output of the motor controller.

Optionally, when the motor controller is currently in the peak mode, if the temperature of the sampling point is greater than the derating threshold and is less than or equal to the over-temperature threshold of the motor controller in the peak mode, controlling derating output of the motor controller.

A motor controller comprising: a temperature sensor and a central processing unit;

the central processing unit is used for controlling the temperature sensor to sample the temperature of a preset sampling point in the motor controller in the normal working process of the motor controller; judging the current working mode of the motor controller, wherein the motor controller has three working modes, namely a steady-state mode, a peak mode and a locked rotor mode; if the temperature of the sampling point exceeds the over-temperature threshold value of the motor controller in the current working mode, controlling the motor controller to stop outputting; wherein the motor controller has different over-temperature thresholds in different operating modes.

Optionally, the central processor specifically determines the current working mode of the motor controller by using the following method:

when the rotating speed of the motor is smaller than a rotating speed threshold value and the output current of the motor controller is larger than the locked-rotor current, judging that the motor controller enters a locked-rotor mode;

when the rotating speed of the motor is greater than or equal to the rotating speed threshold value and the output current of the motor controller is less than or equal to the rated current, or when the rotating speed of the motor is less than the rotating speed threshold value and the output current of the motor controller is less than or equal to the locked-rotor current, the motor controller is judged to enter a steady-state mode;

and when the rotating speed of the motor is greater than or equal to the rotating speed threshold value, the peak current is greater than or equal to the output current of the motor controller, and the output current of the motor controller is greater than the rated current, the motor controller is judged to enter a peak mode.

Optionally, the temperature sensor is mounted on a cold plate of the motor controller or a substrate of a power semiconductor device in the motor controller, and is configured to collect a temperature of the cold plate of the motor controller or a temperature of the substrate of the power semiconductor device in the motor controller.

Optionally, when the motor controller is currently in the steady-state mode, the central processing unit is further configured to control derating output of the motor controller when the temperature of the sampling point is greater than the derating threshold and is less than or equal to the over-temperature threshold of the motor controller in the steady-state mode.

Optionally, when the motor controller is currently in the peak mode, the central processing unit is further configured to control derating output of the motor controller when the temperature of the sampling point is greater than the derating threshold and is less than or equal to the over-temperature threshold of the motor controller in the peak mode.

An electric vehicle comprising a motor controller as disclosed in any of the above.

According to the technical scheme, when the motor controller is in different working modes, the heat transferred from the power semiconductor device wafer to the temperature sampling point is different in the same time, so that the power semiconductor device is subjected to thermal protection by adopting different over-temperature thresholds in different working modes, and the thermal protection of the power semiconductor device and the performance of the power semiconductor device are taken into consideration.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a flowchart of a method for thermal protection of a motor controller according to an embodiment of the present invention;

fig. 2 is a flowchart illustrating a method for determining a current working mode of a motor controller according to an embodiment of the present invention;

FIG. 3 is a flow chart of another method for thermal protection of a motor controller according to an embodiment of the present invention;

fig. 4 is a schematic structural diagram of a motor controller according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1, an embodiment of the present invention discloses a method for protecting a motor controller from heat, including:

step S01: and in the normal working process of the motor controller, sampling the temperature T1 of a preset sampling point in the motor controller. Thereafter, the process proceeds to step S02.

Step S02: judging the current working mode of the motor controller, wherein the motor controller has three working modes, namely a steady-state mode, a peak mode and a locked rotor mode; if the motor controller is currently in the steady-state mode, entering step S03; if the motor controller is currently in the peak mode, the step S04 is entered; if the motor controller is currently in the locked rotor mode, the process proceeds to step S05.

Step S03: and judging whether the temperature T1 of the sampling point exceeds an over-temperature threshold T1_ threshold of the motor controller in a steady-state mode, if so, entering a step S06, otherwise, returning to the step S01.

Step S04: and judging whether the temperature T1 of the sampling point exceeds an over-temperature threshold T2_ threshold of the motor controller in the peak mode, if so, entering a step S06, otherwise, returning to the step S01.

Step S05: and judging whether the temperature T1 of the sampling point exceeds an over-temperature threshold T3_ threshold of the motor controller in the locked rotor mode, if so, entering the step S06, otherwise, returning to the step S01. T1_ threshold, T2_ threshold, and T3_ threshold are of different sizes. Generally, the size relationship between T1_ threshold < T2_ threshold, and T3_ threshold compared to T1_ threshold, T2_ threshold, needs to be calibrated by testing.

Step S06: and controlling the motor controller to stop outputting, thereby realizing thermal protection, and ending the control of the current round.

Specifically, the operating modes of the motor controller are divided into a steady-state mode, a peak-value mode and a locked-rotor mode, and the currents output in the three operating modes are respectively called steady-state current, peak-value current and locked-rotor current. Generally, steady state current < peak current < locked rotor current, so the three operating modes require different operating times for the motor controller, for example: in the steady state mode, the motor controller is required to be able to operate continuously; in the peak mode, the motor controller is required to continuously work for 60 seconds or 30 seconds according to the requirements of a passenger vehicle or a commercial vehicle; in the locked rotor mode, the motor controller is generally required to operate for only a few seconds.

It is very necessary to perform thermal protection on the power semiconductor device in the motor controller, but the junction temperature of the power semiconductor device in the motor controller cannot be directly sampled, and generally, the junction temperature of the power semiconductor device is indirectly calculated after the temperature of a cold plate of the motor controller (or the temperature of a substrate of the power semiconductor device in the motor controller) is sampled. Under the traditional thinking mode, the temperature of a cold plate of the motor controller (or the temperature of a substrate of a power semiconductor device in the motor controller) is sampled, the temperature of a sampling point is compared with a fixed threshold, and when the temperature of the sampling point exceeds the fixed threshold, the motor controller stops outputting, so that the thermal protection of the power semiconductor device in the motor controller can be realized.

However, when the motor controller is in different operation modes, the time for the motor controller to continuously operate, the operating current, and the operating dissipation power are different, and there are thermal resistances and thermal capacitances in the thermal network model from the power semiconductor device wafer to the sampling point, which will cause that in different operation modes, the difference between the temperature of the sampling point and the junction temperature of the power semiconductor device in the motor controller is not equal in the same time (i.e. in different operation modes, the heat transferred from the power semiconductor device wafer to the temperature sampling point is different in the same time). Therefore, if a single fixed threshold is adopted for thermal protection of the power semiconductor device all the time, the fixed threshold is inevitably too low in some operation modes, so that the performance of the power semiconductor device cannot be fully exerted, and the fixed threshold is too high in some operation modes, so that the power semiconductor device has a risk of thermal damage.

In contrast, in the embodiment of the invention, the thermal protection of the power semiconductor device is performed by adopting different over-temperature thresholds in different working modes, so that the thermal protection of the power semiconductor device is considered and the performance of the power semiconductor device is fully exerted.

It should be noted that, in the embodiment of the present invention, the Temperature of the sampling point is acquired by a Temperature sensor arranged in the motor controller, and the Temperature sensor may be, for example, a PT100 Temperature sensor or an NTC (Negative Temperature Coefficient) Temperature sensor, which is not limited. The control algorithm of the embodiment of the present invention is executed by a Central Processing Unit (CPU) in the motor controller.

It should be noted that, in the above steps S01 to S02, the temperature T1 of the preset sampling point in the motor controller is firstly sampled, and then the current working mode of the motor controller is determined, but actually, the execution sequence between the two actions is not limited, and the execution sequence may be changed to the operation mode in which the motor controller is firstly determined, and then the temperature T1 of the preset sampling point in the motor controller is sampled, where fig. 1 is only one example and is not limited.

Optionally, which working mode the motor controller is currently in may be determined according to the motor speed and the output current of the motor controller, as shown in fig. 2, specifically:

step S021: acquiring the rotating speed of the motor and the output current of the motor controller, and then entering a step S022;

step S022: judging whether the rotating speed of the motor is less than a rotating speed threshold (the rotating speed threshold is close to zero) or not, if so, entering a step S023; otherwise, go to step S026;

step S023: judging whether the output current of the motor controller is larger than the locked-rotor current or not, if so, entering a step S024, and otherwise, entering a step S025;

step S024: and judging that the motor controller enters a locked rotor mode, and ending the current round of judgment process.

Step S025: and judging that the motor controller enters a steady-state mode, and ending the current judgment process.

Step S026: comparing the output current of the motor controller with the peak current and the rated current, if the output current of the motor controller is less than or equal to the rated current, entering a step S025, and if the output current of the motor controller is greater than the rated current, entering a step S027;

step S027: and judging that the motor controller enters a peak mode, and ending the current judgment process.

It should be noted that, in fig. 2, the motor speed is compared with the threshold first, and then the output current of the motor controller is compared with the threshold, but actually, the execution sequence between the two actions is not limited, and the output current of the motor controller may be compared with the threshold first, and then the motor speed is compared with the threshold, and fig. 2 is only one example and is not limited.

Optionally, based on any of the embodiments disclosed above, the embodiment of the present invention may further set a derating threshold in a steady-state mode and/or a peak mode, and when the temperature of the sampling point is greater than the derating threshold in the current operating mode and is less than or equal to the over-temperature threshold of the motor controller in the current operating mode, control the motor controller to derate and output; when the derating threshold is set in the steady-state mode and the peak mode at the same time, the derating threshold may be equal or unequal (because the continuous working time in the locked-rotor mode is very short, generally only a few seconds, in order to ensure the safety, the derating output is not considered in the locked-rotor mode). The derated output is to limit the output power of the motor controller. Controlling motor controller derated output or/stopping output is typically limiting/directly stopping motor controller power output by pulse width modulating (e.g., SVPWM modulating) the motor controller's own inverter.

Taking the example of setting derating thresholds in the steady-state mode and the peak mode at the same time, and the derating thresholds being equal, the corresponding thermal protection method of the motor controller is shown in fig. 3, and includes:

step S11: sampling the temperature T1 of a preset sampling point in the motor controller in the normal working process of the motor controller;

step S12: judging the current working mode of the motor controller, wherein the motor controller has three working modes, namely a steady-state mode, a peak mode and a locked rotor mode; if the motor controller is currently in the steady-state mode, entering step S13; if the motor controller is currently in the peak mode, the step S14 is entered; if the motor controller is currently in the locked rotor mode, the process proceeds to step S15.

Step S13: and (3) judging the temperature T1 of the sampling point to be compared with a Derating threshold T1_ rating and an over-temperature threshold T1_ threshold of the motor controller in a steady-state mode, if T1 is more than T1_ threshold, entering step S16, if T1_ rating is less than T1 and less than or equal to T1_ threshold, entering step S17, and if T1 is less than or equal to T1_ rating, returning to step S11.

Step S14: and judging the temperature T1 of the sampling point to be compared with a Derating threshold T1_ rating and an over-temperature threshold T2_ threshold of the motor controller in a peak mode, if T1 is larger than T2_ threshold, entering step S16, if T1_ rating is smaller than T1 and smaller than T2_ threshold, entering step S17, and if T1 is smaller than or equal to T1_ rating, returning to step S11.

Step S15: and judging whether the temperature T1 of the sampling point exceeds an over-temperature threshold T3_ threshold of the motor controller in the locked rotor mode, if so, entering the step S16, otherwise, returning to the step S11. T1_ threshold, T2_ threshold, and T3_ threshold are of different sizes.

Step S16: and controlling the motor controller to stop outputting, thereby realizing thermal protection, and ending the control of the current round.

Step S17: the motor controller is controlled to derate the output to avoid shutdown and achieve thermal protection in the event of a slight over-temperature condition, and then returns to step S11.

It should be noted that, in the above steps S11 to S12, the temperature T1 of the preset sampling point in the motor controller is firstly sampled, and then the current working mode of the motor controller is determined, but actually, the execution sequence between the two actions is not limited, and may be changed to the step of determining the current working mode of the motor controller firstly and then sampling the temperature T1 of the preset sampling point in the motor controller, where fig. 3 is only one example and is not limited.

Corresponding to the above method embodiment, the embodiment of the present invention further discloses a motor controller, as shown in fig. 4, including: a temperature sensor and a CPU;

the CPU is used for controlling the temperature sensor to sample the temperature of a preset sampling point in the motor controller in the normal working process of the motor controller; judging the current working mode of the motor controller, wherein the motor controller has three working modes, namely a steady-state mode, a peak mode and a locked rotor mode; if the temperature of the sampling point exceeds the over-temperature threshold value of the motor controller in the current working mode, controlling the motor controller to stop outputting; wherein the motor controller has different over-temperature thresholds in different operating modes.

Optionally, the temperature sensor is located on a cold plate of the motor controller or a substrate of the power semiconductor device in the motor controller, and is configured to collect a temperature of the cold plate of the motor controller or a temperature of the substrate of the power semiconductor device in the motor controller.

Optionally, in any of the motor controllers disclosed above, when the motor controller is currently in the steady-state mode, the CPU is further configured to control derating output of the motor controller when the temperature of the sampling point is greater than the derating threshold and is less than or equal to the over-temperature threshold of the motor controller in the steady-state mode.

Optionally, in any of the motor controllers disclosed above, when the motor controller is currently in the peak mode, the CPU is further configured to control the motor controller to derate the output when the temperature of the sampling point is greater than the derating threshold and is less than or equal to the over-temperature threshold of the motor controller in the peak mode.

Optionally, in any of the motor controllers disclosed above, the CPU specifically determines the current operating mode of the motor controller by using the following method:

when the rotating speed of the motor is less than a rotating speed threshold value (the rotating speed threshold value is close to zero) and the output current of the motor controller is greater than the locked-rotor current, judging that the motor controller enters a locked-rotor mode;

when the rotating speed of the motor is larger than or equal to the rotating speed threshold value and the output current of the motor controller is smaller than or equal to the rated current, or when the rotating speed of the motor is smaller than the rotating speed threshold value and the output current of the motor controller is smaller than or equal to the locked-rotor current, the motor controller is judged to enter a steady-state mode;

and when the rotating speed of the motor is more than or equal to the rotating speed threshold value and the peak current is more than or equal to the output current of the motor controller and the rated current, judging that the motor controller enters a peak mode.

Alternatively, in any of the motor controllers disclosed above, the temperature sensor may be, for example, a PT100 temperature sensor or an NTC temperature sensor, but is not limited thereto.

In addition, the embodiment of the invention also discloses an electric automobile which comprises any one of the motor controllers disclosed above.

In summary, when the motor controller is in different operating modes, the heat transferred from the power semiconductor device wafer to the temperature sampling point is different in the same time, so that the invention adopts different over-temperature thresholds to perform thermal protection on the power semiconductor device in different operating modes, thereby giving consideration to both the thermal protection on the power semiconductor device and the performance of the power semiconductor device.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the motor controller disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points can be referred to the description of the method part.

The terms "first," "second," and the like in the description and in the claims, and in the drawings, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, the use of the verb "comprise a" to define an element does not exclude the presence of another, identical element in a process, method, article, or apparatus that comprises the element.

Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the embodiments. Thus, the present embodiments are not intended to be limited to the embodiments shown herein but are to be accorded the widest scope consistent with the principles and novel features disclosed herein.