阅读说明：本技术 一种转向架失稳检测方法及系统 (Bogie instability detection method and system ) 是由 林建辉 陈春俊 杨岗 赵海波 石海峰 吴洪霞 于 2021-02-07 设计创作，主要内容包括：本发明涉及轨道交通安全检测技术领域,其目的在于提供一种转向架失稳检测方法及系统。本发明中的转向架失稳检测方法包括以下步骤：获取转向架的横向加速度信号；获取轮对和轨道之间的横移距离信号；判断当前横向加速度信号是否大于横向加速度阈值,若是,则判定转向架处于失稳状态；若否,则判断当前横移距离信号是否大于横移距离阈值,若是,则判定转向架处于失稳状态,若否,则重新获取转向架的横向加速度信号和轮对和轨道之间的横移距离信号。本发明中的转向架失稳检测系统包括检测模块、信号处理模块、横向位移计算模块和报警评估模块。本发明中的转向架失稳检测方法和系统适用于超零界工况,对转向架失稳检测的检测精度高。(The invention relates to the technical field of rail transit safety detection, and aims to provide a bogie instability detection method and system. The bogie instability detection method comprises the following steps: acquiring a transverse acceleration signal of a bogie; acquiring a transverse moving distance signal between a wheel pair and a track; judging whether the current transverse acceleration signal is greater than a transverse acceleration threshold value or not, and if so, judging that the bogie is in a destabilization state; if not, judging whether the current traversing distance signal is larger than the traversing distance threshold value, if so, judging that the bogie is in a destabilization state, and if not, acquiring the transverse acceleration signal of the bogie and the traversing distance signal between the wheel pair and the track again. The bogie instability detection system comprises a detection module, a signal processing module, a transverse displacement calculation module and an alarm evaluation module. The bogie instability detection method and system are suitable for the ultra-zero boundary working condition, and the detection precision of bogie instability detection is high.)

1. A bogie instability detection method is characterized in that: the method comprises the following steps:

acquiring a transverse acceleration signal of a bogie;

acquiring a transverse moving distance signal between a wheel pair and a track;

judging whether the current transverse acceleration signal is greater than a transverse acceleration threshold value, if so, judging that the bogie is in a destabilization state, and if not, entering the next step;

and judging whether the current traversing distance signal is larger than a traversing distance threshold value, if so, judging that the bogie is in a destabilization state, and if not, acquiring a transverse acceleration signal of the bogie and a traversing distance signal between the wheel pair and the track again.

2. The bogie instability detection method according to claim 1, characterized in that: when a transverse moving distance signal between a wheel pair and a track is acquired, the method specifically comprises the following steps:

acquiring the position information of a designated point when the bogie is in a normal state;

acquiring a transverse offset inclination angle signal between a wheel pair and a track;

and obtaining a transverse moving distance signal of the wheel pair according to the transverse offset inclination angle signal between the wheel pair and the track and the position information of the current designated point.

3. The bogie instability detection method according to claim 1, characterized in that: after the lateral acceleration signal of the bogie is obtained, the method further comprises the following steps:

and performing down-sampling processing on the transverse acceleration signal of the bogie to obtain a processed transverse acceleration signal.

4. The bogie instability detection method according to claim 1, characterized in that: when the horizontal acceleration signal of the bogie is subjected to down-sampling processing, the method specifically comprises the following steps:

sampling the transverse acceleration signal of the bogie to obtain a sampled transverse acceleration signal;

and filtering the sampled transverse acceleration signal to obtain a processed transverse acceleration signal.

5. The bogie instability detection method according to claim 1, characterized in that: after the bogie is judged to be in the instability state, the method further comprises the following steps:

and (6) performing instability alarm.

6. A bogie unstability detecting system which characterized in that: the method comprises the following steps:

the detection module is used for acquiring and outputting a transverse acceleration signal of the bogie and a transverse offset inclination angle signal between the wheel pair and the track;

the signal processing module is used for acquiring the position information of the appointed point when the bogie is in a normal state; the system is also used for sampling a transverse acceleration signal of the bogie and a transverse offset inclination angle signal between the wheel set and the track, converting the transverse acceleration signal of the bogie and the transverse offset inclination angle signal between the wheel set and the track into digital signals, and outputting the position information of the current designated point, the converted transverse acceleration signal of the bogie and the transverse offset inclination angle signal between the wheel set and the track;

the transverse displacement calculation module is used for receiving the position information of the current designated point and the converted transverse offset inclination angle signal between the wheel pair and the track, then obtaining a transverse moving distance signal of the wheel pair according to the converted transverse offset inclination angle signal between the wheel pair and the track and the position information of the current designated point, and then outputting the transverse moving distance signal of the current wheel pair;

the alarm evaluation module is used for receiving the converted transverse acceleration signal of the bogie and the transverse moving distance signal of the current wheel pair, then judging whether the current transverse acceleration signal is greater than a transverse acceleration threshold value or not, and if so, judging that the bogie is in a destabilization state; if not, judging whether the current traversing distance signal is larger than the traversing distance threshold value, if so, judging that the bogie is in a destabilization state, and if not, acquiring the transverse acceleration signal of the bogie and the traversing distance signal between the wheel pair and the track again.

7. The bogie instability detection system according to claim 6, wherein: the detection module comprises:

the acceleration sensor is used for acquiring and outputting a transverse acceleration signal of the bogie;

and the laser displacement sensor is used for acquiring and outputting a transverse offset inclination angle signal between the wheel pair and the track.

8. The bogie instability detection system according to claim 6, wherein: the bogie instability detection system further comprises:

and the down-sampling module is used for performing down-sampling processing on the transverse acceleration signal of the bogie to obtain a processed transverse acceleration signal.

9. The bogie instability detection system according to claim 8, wherein: the down-sampling module comprises:

the sampling processing module is used for sampling the transverse acceleration signal of the bogie to obtain a sampled transverse acceleration signal and then outputting the sampled transverse acceleration signal;

and the filtering module is used for receiving the sampled transverse acceleration signal and filtering the sampled transverse acceleration signal to obtain a processed transverse acceleration signal.

10. The bogie instability detection system according to claim 6, wherein: and the alarm evaluation module is also used for giving out instability alarm after the bogie is judged to be in the instability state.

Technical Field

The invention relates to the technical field of rail transit safety detection, in particular to a bogie instability detection method and system.

Background

In recent years, the virtual rail train in China is developed at a high speed, the speed of the train is further improved, but the safety performance of the train is always the focus of attention. The hunting of the train is one of the inherent characteristics of the railway vehicle and is primarily caused by the fact that the train wheel set tread has a taper, and the hunting of the railway vehicle cannot be fundamentally eliminated because the taper of the wheel set tread is a necessary condition for the railway vehicle to pass a curve. However, when the running speed of the train exceeds the critical speed, the stable hunting motion may progress to hunting instability, which brings a great safety risk.

With the 6-time operation speed increase from 1997, the problem of hunting has more and more affected the operation of railway vehicles. From a safety point of view, too severe snaking can lead to increased dynamic loads between vehicle components. For example, the SS8 type quasi-high speed passenger transport electric locomotive has the defects that axle box bearings are damaged due to the hunting instability of a running part in the early running process, and the risk is brought to the safe running of the locomotive; in addition, the large snaking motion can increase the acting force between wheel tracks, thereby causing the damage of the tracks and even the derailment of the wheel sets, for example, 86606 times of freight train accidents in 2008, and the snaking instability in the running of the vehicle is caused by the over-limit abrasion of the center plate and the side frame guide frame of 41 cars behind the machine, thereby causing the derailment accidents of 6 cars of 41-46 cars. From a comfort point of view, the snaking motion causes a decrease in comfort. As for the current situation of China, the frequency of one-time snaking of a motor train unit is generally in the range of 0-2Hz, and a human body is extremely sensitive to 0.1-0.5Hz ultralow frequency vibration and 0.5-2Hz low frequency vibration, usually the ultralow frequency vibration can cause reactions of the human body such as dizziness, nausea and the like, and the low frequency vibration can cause problems of unstable standing and the like. Thus, primary hunting instability, while not causing safety concerns, should also be limited.

Therefore, monitoring the hunting and unstable state of the train is a necessary condition for safe operation of the train. Real-time monitoring of vehicle hunting is typically accomplished through on-board monitoring systems. For a motor train unit train, in the prior art, a real-time snake instability monitoring device is mainly constructed according to standards such as EN4363 and UIC518, so that the vehicle-mounted snake instability monitoring device takes a framework transverse acceleration signal as an input parameter, and final snake instability judgment is carried out through threshold comparison. However, in the practical application process, the inventor finds that at least the following problems exist in the prior art:

a. because of the dependence on threshold determination, the existing methods can only identify when the frame vibrates violently due to hunting instability, which directly results in severe deterioration of the running state of the bogie when hunting instability of the bogie is detected according to the existing methods;

b. for the supercritical condition, if the speed of the train is just between the nonlinear critical speed and the linear critical speed, the bogie may present a small oscillation state, and the vibration acceleration is not enough to reach the alarm threshold. However, running in this state for a long time is obviously disadvantageous to the safety of the train.

Disclosure of Invention

The invention aims to solve the technical problems at least to a certain extent, and provides a bogie instability detection method and a bogie instability detection system.

The technical scheme adopted by the invention is as follows:

the invention discloses a bogie instability detection method, which comprises the following steps:

acquiring a transverse acceleration signal of a bogie;

acquiring a transverse moving distance signal between a wheel pair and a track;

judging whether the current transverse acceleration signal is greater than a transverse acceleration threshold value, if so, judging that the bogie is in a destabilization state, and if not, entering the next step;

and judging whether the current traversing distance signal is larger than a traversing distance threshold value, if so, judging that the bogie is in a destabilization state, and if not, acquiring a transverse acceleration signal of the bogie and a traversing distance signal between the wheel pair and the track again.

Optionally, when the traverse distance signal between the wheel pair and the rail is acquired, the specific steps are as follows:

acquiring the position information of a designated point when the bogie is in a normal state;

acquiring a transverse offset inclination angle signal between a wheel pair and a track;

and obtaining a transverse moving distance signal of the wheel pair according to the transverse offset inclination angle signal between the wheel pair and the track and the position information of the current designated point.

Optionally, after acquiring the lateral acceleration signal of the bogie, the method further comprises the following steps:

and performing down-sampling processing on the transverse acceleration signal of the bogie to obtain a processed transverse acceleration signal.

Optionally, when the down-sampling processing is performed on the lateral acceleration signal of the bogie, the specific steps are as follows:

sampling the transverse acceleration signal of the bogie to obtain a sampled transverse acceleration signal;

and filtering the sampled transverse acceleration signal to obtain a processed transverse acceleration signal.

Optionally, after determining that the bogie is in the instability state, the method further comprises the following steps:

and (6) performing instability alarm.

The invention also discloses a bogie instability detection system, which comprises:

the detection module is used for acquiring and outputting a transverse acceleration signal of the bogie and a transverse offset inclination angle signal between the wheel pair and the track;

the signal processing module is used for acquiring the position information of the appointed point when the bogie is in a normal state; the system is also used for sampling a transverse acceleration signal of the bogie and a transverse offset inclination angle signal between the wheel set and the track, converting the transverse acceleration signal of the bogie and the transverse offset inclination angle signal between the wheel set and the track into digital signals, and outputting the position information of the current designated point, the converted transverse acceleration signal of the bogie and the transverse offset inclination angle signal between the wheel set and the track;

the transverse displacement calculation module is used for receiving the position information of the current designated point and the converted transverse offset inclination angle signal between the wheel pair and the track, then obtaining a transverse moving distance signal of the wheel pair according to the converted transverse offset inclination angle signal between the wheel pair and the track and the position information of the current designated point, and then outputting the transverse moving distance signal of the current wheel pair;

the alarm evaluation module is used for receiving the converted transverse acceleration signal of the bogie and the transverse moving distance signal of the current wheel pair, then judging whether the current transverse acceleration signal is greater than a transverse acceleration threshold value or not, and if so, judging that the bogie is in a destabilization state; if not, judging whether the current traversing distance signal is larger than the traversing distance threshold value, if so, judging that the bogie is in a destabilization state, and if not, acquiring the transverse acceleration signal of the bogie and the traversing distance signal between the wheel pair and the track again.

Optionally, the detection module includes:

the acceleration sensor is used for acquiring and outputting a transverse acceleration signal of the bogie;

and the laser displacement sensor is used for acquiring and outputting a transverse offset inclination angle signal between the wheel pair and the track.

Optionally, the bogie instability detection system further comprises:

and the down-sampling module is used for performing down-sampling processing on the transverse acceleration signal of the bogie to obtain a processed transverse acceleration signal.

Further, the down-sampling module comprises:

the sampling processing module is used for sampling the transverse acceleration signal of the bogie to obtain a sampled transverse acceleration signal and then outputting the sampled transverse acceleration signal;

and the filtering module is used for receiving the sampled transverse acceleration signal and filtering the sampled transverse acceleration signal to obtain a processed transverse acceleration signal.

Optionally, the alarm evaluation module is further configured to perform a destabilization alarm after determining that the bogie is in the destabilization state.

The invention has the beneficial effects that: the method is suitable for the working condition of the ultra-zero boundary, and the detection precision of the instability detection of the bogie is high. Specifically, the bogie instability detection method and system provided by the invention can further perform instability detection by adopting the traversing distance between the wheel set and the track on the basis of judging whether the bogie is unstable or not by using a bogie transverse acceleration signal, can effectively solve the problem that the existing bogie transverse acceleration-based algorithm does not have detection capability on small-amplitude snaking motion under a supercritical working condition, perfects the framework instability detection system and improves the running safety of a train.

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 flow chart of a method of bogie instability detection in accordance with the present invention;

FIG. 2 is a detailed flow chart of a bogie instability detection method of the present invention;

FIG. 3 is a schematic illustration of the vehicle in a normal condition and when leaning right;

fig. 4 is a schematic structural view of the wheel set in a normal state and when right-hand lateral movement occurs.

Detailed Description

The invention is further described with reference to the following figures and specific embodiments. It should be noted that the description of the embodiments is provided to help understanding of the present invention, but the present invention is not limited thereto. Specific structural and functional details disclosed herein are merely illustrative of example embodiments of the invention. This invention may, however, be embodied in many alternate forms and should not be construed as limited to the embodiments set forth herein.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises," "comprising," "includes" and/or "including," when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, numbers, steps, operations, elements, components, and/or groups thereof.

It should also be noted that, in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may, in fact, be executed substantially concurrently, or the figures may sometimes be executed in the reverse order, depending upon the functionality/acts involved.

It should be understood that specific details are provided in the following description to facilitate a thorough understanding of example embodiments. However, it will be understood by those of ordinary skill in the art that the example embodiments may be practiced without these specific details. For example, systems may be shown in block diagrams in order not to obscure the examples in unnecessary detail. In other instances, well-known processes, structures and techniques may be shown without unnecessary detail in order to avoid obscuring example embodiments.

It should be understood that the bogie is one of the most important parts in the construction of a railway vehicle, and includes wheel sets, side frames, brake devices, and bolster structures, and the wheel set hereinafter is one of the main parts of the bogie.

Example 1:

the embodiment provides a method for detecting instability of a bogie, as shown in fig. 1, which includes the following steps:

acquiring a transverse acceleration signal of a bogie;

acquiring a transverse moving distance signal between a wheel pair and a track;

judging whether the current transverse acceleration signal is greater than a transverse acceleration threshold value, if so, judging that the bogie is in a destabilization state, and if not, entering the next step;

and judging whether the current traversing distance signal is larger than a traversing distance threshold value, if so, judging that the bogie is in a destabilization state, and if not, acquiring a transverse acceleration signal of the bogie and a traversing distance signal between the wheel pair and the track again.

The embodiment is suitable for the working condition of the ultra-zero boundary, and the detection precision of the instability detection of the bogie is high. Specifically, the embodiment can further perform instability detection by adopting the traversing distance between the wheel set and the track on the basis of judging whether the bogie is unstable by the bogie transverse acceleration signal, can effectively solve the problem that the existing bogie transverse acceleration-based algorithm does not have detection capability on small snaking motion under the supercritical working condition, perfects a framework instability detection system and improves the running safety of a train.

Example 2:

the embodiment provides a method for detecting instability of a bogie, as shown in fig. 2, which includes the following steps:

s1, acquiring a transverse acceleration signal of a bogie;

after step S1, the method further includes the following steps:

A. sampling the transverse acceleration signal of the bogie to obtain a sampled transverse acceleration signal;

B. and filtering the sampled transverse acceleration signal by using a low-pass filter to eliminate frequency aliasing and obtain a processed transverse acceleration signal.

The steps A and B realize the down-sampling processing of the transverse acceleration signal of the bogie, so that the transverse acceleration signal of the bogie can obtain higher frequency resolution.

S2, acquiring a transverse moving distance signal between the wheel pair and the track; the method comprises the following specific steps:

s201, acquiring position information of a designated point when the bogie is in a normal state; it will be understood that the normal condition refers to a condition in which the bogie is not in a hunting condition in which the bogie is not laterally offset relative to the track, as is conventionally the case when the bogie is travelling in a direction in which the central axis of the track is parallel and the vertical centre line of the bogie is parallel to the centre line of the track line.

S202, acquiring a transverse offset inclination angle signal between a wheel pair and a track;

s203, obtaining a transverse moving distance signal of the wheel set according to the transverse offset inclination angle signal between the wheel set and the track and the position information of the current designated point.

Specifically, assuming that the lateral offset inclination angle between the wheel set and the rail is α, as shown in fig. 3, the schematic diagram when the vehicle is in a normal state is shown as a solid line, and the schematic diagram when the vehicle is tilted right is shown as a dashed line; as shown in fig. 4, the schematic diagram of the wheel set in the normal state is shown by a solid line, and the schematic diagram of the wheel set when the right traverse occurs is shown by a broken line; in this embodiment, a spatial rectangular coordinate system O-xyz is established with the intersection point between the middle axle of the wheel set when the bogie is in the normal state and the middle axle of the wheel set when the bogie is in the normal state as the origin O, the middle axle of the wheel set when the bogie is in the normal state as the z-axis, the axial direction of the axle of the wheel set as the y-axis, and the moving direction of the bogie as the x-axis. When the bogie is in a normal state, the position information of the appointed point when the bogie is in the normal state is set as follows: a coordinate Q (y, z) on a plane rectangular coordinate system yOz; when the bogie is deflected, i.e. the lateral offset between the wheel set and the track is at an inclination angle alpha, the coordinates of the designated point on a plane rectangular coordinate system yOz are Q ' (y ', z '), and the traversing distance between the wheel set and the track is Deltay, wherein,

y′＝z sinα+y cosα，

z′＝z cosα-y sinα，

Δy＝y′-y。

s3, judging whether the current transverse acceleration signal is larger than a transverse acceleration threshold value or not, if so, judging that the bogie is in a destabilization state, and then entering a step S5; if not, go to step S4;

s4, judging whether the current traversing distance signal is larger than a traversing distance threshold value or not, if so, judging that the bogie is in a destabilization state, and then entering the step S5; if not, the transverse acceleration signal of the bogie and the transverse moving distance signal between the wheel set and the track are obtained again.

And S5, performing instability alarm. Therefore, managers can conveniently know whether the train is in a snake-running instability state or not in time, and the avoidance control can be conveniently carried out on the train in time.

The embodiment is suitable for the working condition of the ultra-zero boundary, and the detection precision of the instability detection of the bogie is high.

Example 3:

the present embodiment provides a bogie instability detection system for implementing the bogie instability detection method in embodiment 1 or 2, where the bogie instability detection system includes:

the detection module is used for acquiring and outputting a transverse acceleration signal of the bogie and a transverse offset inclination angle signal between the wheel pair and the track;

the signal processing module is used for acquiring the position information of the appointed point when the bogie is in a normal state; the device is also used for sampling a transverse acceleration signal of the bogie and a transverse offset inclination angle signal between the wheel set and the track, converting analog signals such as the transverse acceleration signal of the bogie and the transverse offset inclination angle signal between the wheel set and the track into digital signals, and outputting the position information of the current designated point, the converted transverse acceleration signal of the bogie and the transverse offset inclination angle signal between the wheel set and the track;

the transverse displacement calculation module is used for receiving the position information of the current designated point and the converted transverse offset inclination angle signal between the wheel pair and the track, then obtaining a transverse moving distance signal of the wheel pair according to the converted transverse offset inclination angle signal between the wheel pair and the track and the position information of the current designated point, and then outputting the transverse moving distance signal of the current wheel pair;

the alarm evaluation module is used for receiving the converted transverse acceleration signal of the bogie and the transverse moving distance signal of the current wheel pair, then judging whether the current transverse acceleration signal is greater than a transverse acceleration threshold value or not, and if so, judging that the bogie is in a destabilization state; if not, judging whether the current traversing distance signal is larger than the traversing distance threshold value, if so, judging that the bogie is in a destabilization state, and if not, acquiring the transverse acceleration signal of the bogie and the traversing distance signal between the wheel pair and the track again.

In this embodiment, the detection module includes:

the acceleration sensor is used for acquiring and outputting a transverse acceleration signal of the bogie; in the embodiment, the acceleration sensor is realized by adopting a piezoelectric acceleration sensor, has the characteristics of large dynamic range, wide frequency range, firmness, durability, small external interference, no need of any external power supply for self-generation of charge signals due to stress of the piezoelectric material and the like, is widely applied and is suitable for severe working conditions.

And the laser displacement sensor is used for acquiring and outputting a transverse offset inclination angle signal between the wheel pair and the track.

It should be noted that non-contact measurement has become a hot spot in the measurement field due to its good accuracy and real-time performance. The laser displacement sensor is a main method for non-contact measurement, and is widely applied to rapid measurement and reverse engineering of complex three-dimensional curved surfaces due to the high speed of data point acquisition and the reduction of measurement time and cost.

In this embodiment, the laser displacement sensor may use, but is not limited to, a direct-injection triangulation principle to obtain a lateral offset tilt angle signal between the wheel pair and the rail.

In this embodiment, the bogie instability detection system further includes:

and the down-sampling module is used for performing down-sampling processing on the transverse acceleration signal of the bogie to obtain a processed transverse acceleration signal.

Specifically, the down-sampling module includes:

the sampling processing module is used for sampling the transverse acceleration signal of the bogie to obtain a sampled transverse acceleration signal and then outputting the sampled transverse acceleration signal;

and the filtering module is used for receiving the sampled transverse acceleration signal and filtering the sampled transverse acceleration signal so as to eliminate frequency aliasing and obtain a processed transverse acceleration signal.

It should be noted that the filtering module can be implemented by a low-pass filter, and has the characteristics of low loss, high rejection, accurate division point, double copper tube protection, good frequency shielding, strong waterproof function and the like.

In this embodiment, the alarm evaluation module is further configured to perform destabilization alarm after determining that the bogie is in the destabilization state, so that a manager can know whether the train is in the snake destabilization state in time, and thus can perform avoidance control on the train in time.

It will be apparent to those skilled in the art that the modules or steps of the present invention described above may be implemented by a general purpose computing device, they may be centralized on a single computing device or distributed across a network of multiple computing devices, and they may alternatively be implemented by program code executable by a computing device, such that they may be stored in a storage device and executed by a computing device, or fabricated separately as individual integrated circuit modules, or fabricated as a single integrated circuit module from multiple modules or steps. Thus, the present invention is not limited to any specific combination of hardware and software.

The various embodiments described above are merely illustrative, and may or may not be physically separate, as they relate to elements illustrated as separate components; if reference is made to a component displayed as a unit, it may or may not be a physical unit, and may be located in one place or distributed over a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: modifications of the technical solutions described in the embodiments or equivalent replacements of some technical features may still be made. And such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Finally, it should be noted that the present invention is not limited to the above alternative embodiments, and that various other forms of products can be obtained by anyone in light of the present invention. The above detailed description should not be taken as limiting the scope of the invention, which is defined in the claims, and which the description is intended to be interpreted accordingly.