阅读说明：本技术 一种无人机群定位系统和定位方法 (Unmanned aerial vehicle group positioning system and positioning method ) 是由 江玲 袁火平 于兴旺 于 2020-06-22 设计创作，主要内容包括：本发明公开了提供一种无人机群定位系统和定位方法,能够在隧道或者洞穴中等卫星信号很差的地方进行定位导航。在隧道或者洞穴中等卫星信号很差的地方,有多个无人机在里面飞行,构成一个无人机群。无人机群中在定位导航中有一个无人机作为领队,可向其他无人机发射信号告知其行走方向,以控制对队形,指定定位无人机和辅助定位无人机。其中,每个无人机上均携带有无信息的标签,无人机在飞行过程中在相应位置贴上标签,贴标签的同时赋予标签位置信息并将此处标签的位置信息返回给系统以便于后续定位导航。本发明的优点在于：可以隧道或者洞穴中等卫星信号很差的地方实现自动定位导航,保障了人身安全,实现了精准导航。(The invention discloses a positioning system and a positioning method for an unmanned aerial vehicle cluster, which can perform positioning navigation in places with poor satellite signals, such as tunnels or caves. In the places with poor satellite signals, such as tunnels or caves, a plurality of unmanned aerial vehicles fly in the places to form an unmanned aerial vehicle cluster. An unmanned aerial vehicle is used as a leader in positioning navigation in the unmanned aerial vehicle cluster, and can transmit signals to other unmanned aerial vehicles to inform the walking direction of the unmanned aerial vehicles so as to control the formation, appoint to position the unmanned aerial vehicle and assist in positioning the unmanned aerial vehicle. Wherein, all carry the label of no information on every unmanned aerial vehicle, unmanned aerial vehicle pastes the label at relevant position in flight process, gives label positional information and returns the positional information of here label for the system so that follow-up location navigation when labelling. The invention has the advantages that: the method can realize automatic positioning navigation in places with poor satellite signals, such as tunnels or caves, ensures personal safety and realizes accurate navigation.)

1. A unmanned aerial vehicle group positioning system comprises an unmanned aerial vehicle group, and is characterized in that a piloting unmanned aerial vehicle is arranged in the unmanned aerial vehicle group in positioning navigation and is responsible for transmitting signals to other unmanned aerial vehicles to inform the walking direction and formation of the piloting unmanned aerial vehicle, and meanwhile, the positioning unmanned aerial vehicle and an auxiliary positioning unmanned aerial vehicle are required to be appointed; each unmanned aerial vehicle comprises a module with a flight function, a radio frequency reading and writing module, an edge calculation module, a database, a satellite positioning module, a communication module, an obstacle avoidance module, an image identification module and an automatic electronic tag pasting module;

the automatic electronic tag pasting module can carry and install an electronic tag and can carry and install the electronic tag;

the electronic tag carries unique identification information;

the radio frequency read-write module is used for receiving verification information transmitted by the electronic tag based on UWB technology and transmitting the information to the edge calculation module;

the communication module is responsible for communication among the unmanned aerial vehicles;

the database is used for storing coordinate position information corresponding to the electronic tags;

the edge calculation module is used for searching the position coordinate information of the corresponding electronic tag in the database and calculating the real-time position of the unmanned aerial vehicle;

the satellite positioning module is used for positioning the initial position of the unmanned aerial vehicle and positioning the coordinate position of the electronic tag at the initial moment;

the obstacle avoidance module and the image identification module are used for planning the flight path of the unmanned aerial vehicle and selecting the position of an electronic tag to be installed.

2. The positioning system of claim 1, wherein the positioning drone is capable of performing self-positioning calculation and deducing positioning of other drones and sharing the positioning to databases of all drones in real time, so that at least three signal ranges of the electronic tag and the auxiliary positioning drone can cover the real-time coordinate position of the positioning drone at any moment, and the number of the electronic tags is greater than or equal to one; the auxiliary positioning unmanned aerial vehicle is an unmanned aerial vehicle for assisting positioning unmanned aerial vehicle positioning to perform hovering control.

3. The method for drone swarm localization according to any of the preceding claims, comprising the steps of:

(1) by utilizing a satellite positioning technology, acquiring initial coordinate positions of all unmanned aerial vehicles through an electronic tag which is manually or fixedly installed in advance and has known position coordinates by the unmanned aerial vehicles;

(2) after all the unmanned aerial vehicles fly into the signal range of the electronic tag, the magnetic field in the identification area of the radio frequency read-write module enables the electronic tag to generate induction current, and the chip of the electronic tag transmits signals to the radio frequency read-write module;

(3) the piloting unmanned aerial vehicle acquires information of other unmanned aerial vehicles for receiving the electronic tag signals through communication at regular intervals, designates the unmanned aerial vehicle with the strongest electronic tag signal received by the unmanned aerial vehicle population as a positioning unmanned aerial vehicle, and designates a certain number of unmanned aerial vehicles to hover in the air as auxiliary positioning unmanned aerial vehicles according to the requirements of positioning precision, communication and formation requirements and according to a strategy of being far away from the positioning unmanned aerial vehicle and being close to the positioning unmanned aerial vehicle;

(4) after a radio frequency read-write module or a communication module of the positioning unmanned aerial vehicle receives three or more electronic tag signals and auxiliary positioning unmanned aerial vehicle signals, the signal intensity, the absolute time difference of signal receiving and sending and the corresponding electronic tag information are input to an edge calculation module;

(5) the edge calculation module accesses a database to obtain coordinate position information of a corresponding electronic tag;

(6) after receiving the electronic tag coordinate position information of the database, the edge calculation module obtains the coordinate position of the positioning unmanned aerial vehicle by using a TDOA (time difference of arrival) positioning and field intensity method, and further calculates the coordinate positions of other unmanned aerial vehicles by using the field intensity method;

(7) when the signal intensity of the electronic tag of any unmanned aerial vehicle in the unmanned aerial vehicle cluster is attenuated to a threshold value, the unmanned aerial vehicle selects a proper position by using the obstacle avoidance module and the image identification module and flies, and simultaneously informs the piloting unmanned aerial vehicle to control other unmanned aerial vehicles to hover and wait for the unmanned aerial vehicle to return, a new electronic tag is installed at the new position, and the identity identification information and the coordinate position information of the electronic tag are recorded in the database.

4. The drone swarm positioning method according to claim 3, wherein the positioning method is determined according to the number of the electronic tags, and when the number of the electronic tags is greater than or equal to two, the TDOA positioning method is used to calculate the locations of the electronic tags; when the number of the electronic tags is less than two or the positioning between the unmanned aerial vehicles is carried out, a field intensity method is adopted; and then, solving an equation set by adopting least square fitting, and selecting a solution closest to the last moment position of the unmanned aerial vehicle as the current moment coordinate position of the unmanned aerial vehicle.

5. The method according to claim 3, wherein the TDOA positioning method is performed by calculating an absolute time difference distance between each two electronic tags and the rf read/write module, and the calculation method is as follows:

wherein i and j are the serial numbers of the electronic tags and i is not equal to j, t_iThe time difference from the sending of a signal to the receiving of the ith electronic tag signal is given to the radio frequency read-write module, and c is the speed of light; (x)_i，y_i，z_i) The coordinate position of the ith electronic tag is shown;

the field intensity method is that the radio frequency read-write module or the communication module respectively receives the signal intensity of a single electronic tag or an unmanned aerial vehicle to calculate the linear distance, and the calculation method comprises the following steps:

R_i＝-A_i+10·n_i·lg(d_i) (2)

R_ifor the signal strength value received by the ith unmanned aerial vehicle, A_iAnd n_iIs a signal propagation parameter; d_iThe distance between the ith unmanned aerial vehicle and the tag; (x)_i，y_i，z_i) And (4) positioning the coordinate position of the unmanned aerial vehicle for the ith electronic tag or the auxiliary positioning.

Technical Field

The invention relates to a positioning system and a positioning method for an unmanned aerial vehicle group, belonging to the technical field of unmanned aerial vehicles.

Background

At present, most of home and abroad positioning systems are based on satellite navigation systems, such as a common GPS system, and the adopted positioning technology is usually time difference of arrival (TDOA) positioning technology, which can effectively reduce the influence of obstacles on positioning accuracy. However, in places with poor satellite signals such as tunnels or caves, the navigation system is not accurately positioned, so several technologies such as manual detection and positioning, semi-automatic instrument detection and positioning and the like are often adopted in these special environments, wherein the manual detection only has two to three hours of detection time due to the daily operation of the tunnels, which results in short manual detection lines; semi-automatization's instrument detects because just need to arrange in advance when tunnel production and detect the sensor, erects special communications facilities simultaneously and just can go on when tunnel operation, and the sensor survival rate of arranging in advance is not very high, and some places are unsafe when installing the sensor moreover, may hurt the people.

A label is adopted by a common single unmanned aerial vehicle positioning system for auxiliary positioning, if a patent CN106197422B is based on a pasted auxiliary two-dimensional label, a camera is adopted to perform image processing on the label to realize unmanned aerial vehicle positioning, the method is high in cost, the two-dimensional label needs to be pasted in advance, manpower, material resources and financial resources are wasted, and manual labeling in places with poor satellite signals such as tunnels or caves is unsafe. Patent CN110632937A is to locate the drone by placing detection tags equidistantly on the oil pipeline. Patent CN110446159A realizes positioning of the drone by combining a label pasted in advance with an auxiliary vision system. The same situation requiring the presetting of 8 anchor points also exists in patent CN108445914, which uses TDOA location technology to locate the drone swarm. At present, no system for assisting self positioning by automatically labeling while flying by an unmanned aerial vehicle group exists, and autonomous positioning flying of the unmanned aerial vehicle group in a complex environment is realized in a real sense.

Disclosure of Invention

Therefore, an object of the present invention is to overcome the above-mentioned drawbacks of the prior art, and to provide a system and a method for positioning a drone swarm, which can perform positioning and navigation in places with poor satellite signals, such as tunnels or caves. In the poor place of satellite signal such as tunnel or cave, there are a plurality of unmanned aerial vehicles to fly inside, constitute a unmanned aerial vehicle crowd, wherein, all carry the label of no information on every unmanned aerial vehicle, unmanned aerial vehicle pastes the label in the corresponding position in-process of flying, gives label positional information and feeds back the positional information of here label to the system so that follow-up location navigation is given to the while of labeling.

The unmanned aerial vehicle group positioning system comprises an unmanned aerial vehicle group, wherein a piloting unmanned aerial vehicle is arranged in the unmanned aerial vehicle group in positioning navigation and is responsible for transmitting signals to other unmanned aerial vehicles to inform the other unmanned aerial vehicles of the walking direction and the formation, and meanwhile, the unmanned aerial vehicle needs to be appointed and positioned and the unmanned aerial vehicle needs to be assisted.

Each unmanned aerial vehicle comprises a module with a flight function, a radio frequency reading and writing module, an edge calculation module, a database, a satellite positioning module, a communication module, an obstacle avoidance module, an image identification module and an automatic electronic tag pasting module;

the automatic electronic tag pasting module can carry and install an electronic tag and can carry and install the electronic tag;

the electronic tag carries unique identification information;

the radio frequency read-write module is used for receiving verification information transmitted by the electronic tag based on UWB technology and transmitting the information to the edge calculation module;

the communication module is responsible for communication among the unmanned aerial vehicles;

the database is used for storing coordinate position information corresponding to the electronic tags;

the edge calculation module is used for searching the position coordinate information of the corresponding electronic tag in the database and calculating the real-time position of the unmanned aerial vehicle;

the satellite positioning module is used for positioning the initial position of the unmanned aerial vehicle and positioning the coordinate position of the electronic tag at the initial moment;

the obstacle avoidance module and the image identification module are used for planning the flight path of the unmanned aerial vehicle and selecting the position of an electronic tag to be installed.

The positioning unmanned aerial vehicle can perform self-positioning calculation, deduce the positioning of other unmanned aerial vehicles and share the positioning of other unmanned aerial vehicles to a database of all unmanned aerial vehicles in real time, and the requirement that at any moment, at least three signal ranges of an electronic tag and an auxiliary positioning unmanned aerial vehicle cover the real-time coordinate position of the positioning unmanned aerial vehicle is met, wherein the number of the electronic tags is more than or equal to one; the auxiliary positioning unmanned aerial vehicle is an unmanned aerial vehicle for assisting positioning unmanned aerial vehicle positioning to perform hovering control.

The unmanned aerial vehicle group positioning method comprises the following steps:

(1) by utilizing a satellite positioning technology, acquiring initial coordinate positions of all unmanned aerial vehicles through an electronic tag which is manually or fixedly installed in advance and has known position coordinates by the unmanned aerial vehicles;

(2) after all the unmanned aerial vehicles fly into the signal range of the electronic tag, the magnetic field in the identification area of the radio frequency read-write module enables the electronic tag to generate induction current, and the chip of the electronic tag transmits signals to the radio frequency read-write module;

(3) the piloting unmanned aerial vehicle acquires information of other unmanned aerial vehicles for receiving the electronic tag signals through communication at regular intervals, designates the unmanned aerial vehicle with the strongest electronic tag signal received by the unmanned aerial vehicle population as a positioning unmanned aerial vehicle, and designates a certain number of unmanned aerial vehicles to hover in the air as auxiliary positioning unmanned aerial vehicles according to the requirements of positioning precision, communication and formation requirements and according to a strategy of being far away from the positioning unmanned aerial vehicle and being close to the positioning unmanned aerial vehicle;

(4) after a radio frequency read-write module or a communication module of the positioning unmanned aerial vehicle receives three or more electronic tag signals and auxiliary positioning unmanned aerial vehicle signals, the signal intensity, the absolute time difference of signal receiving and sending and the corresponding electronic tag information are input to an edge calculation module;

(5) the edge calculation module accesses a database to obtain coordinate position information of a corresponding electronic tag;

(6) after receiving the electronic tag coordinate position information of the database, the edge calculation module obtains the coordinate position of the positioning unmanned aerial vehicle by using a TDOA (time difference of arrival) positioning and field intensity method, and further calculates the coordinate positions of other unmanned aerial vehicles by using the field intensity method;

(7) judging whether the signal intensity of an electronic tag of any unmanned aerial vehicle in the unmanned aerial vehicle cluster is attenuated to a threshold value, if so, selecting a proper position by the corresponding unmanned aerial vehicle by using an obstacle avoidance module and an image identification module and flying to the proper position, simultaneously informing a piloting unmanned aerial vehicle to control other unmanned aerial vehicles to hover and wait for the unmanned aerial vehicle to return, installing a new electronic tag at the new position, and recording the identity identification information and the coordinate position information of the electronic tag to a database; if not, returning to the step (2) until the unmanned aerial vehicle group arrives at the designated area or completes the flight task.

The positioning method is determined according to the number of the electronic tags, and when the number of the electronic tags is more than or equal to two, the position of the electronic tags is calculated by adopting a TDOA positioning method; when the number of the electronic tags is less than two or the positioning between the unmanned aerial vehicles is carried out, a field intensity method is adopted; and then, solving an equation set by adopting least square fitting, and selecting a solution closest to the last moment position of the unmanned aerial vehicle as the current moment coordinate position of the unmanned aerial vehicle.

The TDOA positioning method is that the absolute time difference distance from the radio frequency read-write module to every two electronic tags is calculated, and the calculation method is as follows;

wherein i and j are the serial numbers of the electronic tags and i is not equal to j, t_iThe time difference from the sending of a signal to the receiving of the ith electronic tag signal is given to the radio frequency read-write module, and c is the speed of light; (x)_i，y_i，z_i) Is the coordinate position of the ith electronic tag.

The field intensity method is that the radio frequency read-write module or the communication module respectively receives the signal intensity of a single electronic tag or an unmanned aerial vehicle to calculate the linear distance, and the calculation method comprises the following steps:

R_i＝-A_i+10·n_i·lg(d_i) (2)

R_ifor the signal strength value received by the ith unmanned aerial vehicle, A_iAnd n_iIs a signal propagation parameter; d_iThe distance between the ith unmanned aerial vehicle and the tag; (x)_i，y_i，z_i) Is composed ofThe ith electronic tag or the coordinate position of the auxiliary positioning unmanned aerial vehicle.

Has the beneficial effects that;

the invention reduces the positioning precision error and the quantity and the cost of the electronic tags by the positioning unmanned aerial vehicle and the auxiliary positioning unmanned aerial vehicle, simultaneously can select a proper position to be additionally provided with the positioning electronic tag according to the positioning precision requirement and the planning of the flight path, improves the positioning precision of the unmanned aerial vehicle cluster, can realize the automatic positioning navigation of the unmanned aerial vehicle cluster in places with poor satellite signals, such as tunnels or caves, ensures the personal safety and realizes the precise navigation.

Drawings

FIG. 1 is a schematic diagram of a positioning system according to the present invention; wherein, 1 is the electronic tags who has installed, 2 is location unmanned aerial vehicle, 3 are assistance-localization real-time unmanned aerial vehicle, 4 are the electronic tags position that need newly to install, and the ring is electronic tags signal coverage.

Fig. 2 is a flowchart of a positioning method according to an embodiment of the present invention.

Detailed Description

The technical solution in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without inventive effort based on the embodiments of the present invention, are within the scope of the present invention. The specific technical scheme is as follows:

the invention discloses a positioning system and a positioning method for an unmanned aerial vehicle cluster, which can perform positioning navigation in places with poor satellite signals, such as tunnels or caves. In the places with poor satellite signals such as tunnels or caves, a plurality of unmanned aerial vehicles fly in the unmanned aerial vehicles to form an unmanned aerial vehicle cluster, wherein each unmanned aerial vehicle carries a label without information, the unmanned aerial vehicles stick the labels at corresponding positions in the flying process, the labels are endowed with position information of the labels while the labels are pasted, and the position information of the labels is returned to the system so as to facilitate subsequent positioning and navigation.

The unmanned aerial vehicle group positioning system comprises an unmanned aerial vehicle group, wherein a piloting unmanned aerial vehicle is arranged in the unmanned aerial vehicle group in positioning navigation and is responsible for transmitting signals to other unmanned aerial vehicles to inform the other unmanned aerial vehicles of the walking direction and the formation, and meanwhile, the unmanned aerial vehicle needs to be appointed and positioned and the unmanned aerial vehicle needs to be assisted.

Each unmanned aerial vehicle comprises a module with a flight function, a radio frequency reading and writing module, an edge calculation module, a database, a satellite positioning module, a communication module, an obstacle avoidance module, an image identification module and an automatic electronic tag pasting module.

The automatic electronic tag pasting module can carry and install an electronic tag and can carry and install the electronic tag;

the electronic tag carries unique identification information;

the radio frequency read-write module is used for receiving verification information transmitted by the electronic tag based on UWB technology and transmitting the information to the edge calculation module;

the communication module is responsible for communication among the unmanned aerial vehicles;

the database is used for storing coordinate position information corresponding to the electronic tags;

the edge calculation module is used for searching the position coordinate information of the corresponding electronic tag in the database and calculating the real-time position of the unmanned aerial vehicle;

the satellite positioning module is used for positioning the initial position of the unmanned aerial vehicle and positioning the coordinate position of the electronic tag at the initial moment;

the obstacle avoidance module and the image identification module are used for planning the flight path of the unmanned aerial vehicle and selecting the position of an electronic tag to be installed.

The unmanned aerial vehicle group positioning method comprises the following steps:

(1) at the initial moment, one or more electronic tags with known position coordinates are fixedly installed in advance in a place near a tunnel or a cave where the attenuation of GPS signals is close to a threshold value in a manual mode by utilizing a satellite positioning technology, the electronic tag information is stored in an unmanned aerial vehicle database, and the unmanned aerial vehicle cluster positions the initial coordinate position of each unmanned aerial vehicle through respective GPS;

(2) taking off the unmanned aerial vehicle, and utilizing the obstacle avoidance module and the image identification module and according to a path planning program, leading the unmanned aerial vehicle to start to lead the unmanned aerial vehicle group to fly towards a target position according to a formation shape to enter a tunnel or a cave;

(3) after the unmanned aerial vehicles enter the cave or the tunnel, judging whether the GPS signal intensity of each unmanned aerial vehicle is attenuated to a threshold value, and if one unmanned aerial vehicle is attenuated to the threshold value, performing the step (4); if not, returning to the step (2) until the flight reaches the designated position or the flight task is completed;

(4) all the unmanned aerial vehicle radio frequency read-write modules transmit UWB signals at regular intervals according to the communication instruction of the piloting unmanned aerial vehicle, after the UWB signals fly into the signal range of the electronic tag, the radio frequency read-write modules identify the magnetic field in the area to enable the electronic tag to generate induction current, and the signals are transmitted to the corresponding radio frequency read-write modules through chips of the electronic tag;

(5) the piloting unmanned aerial vehicle acquires information of other unmanned aerial vehicles receiving the electronic tag signals through communication, designates the unmanned aerial vehicle with the strongest electronic tag signal received by the unmanned aerial vehicle population as a positioning unmanned aerial vehicle, and designates a certain number of unmanned aerial vehicles to hover in the air as auxiliary positioning unmanned aerial vehicles according to the requirements of positioning precision, communication and formation requirements and a strategy of being far away from the positioning unmanned aerial vehicle;

(6) after a radio frequency read-write module or a communication module of the positioning unmanned aerial vehicle receives three or more electronic tag signals and auxiliary positioning unmanned aerial vehicle signals, the signal intensity, the absolute time difference of signal receiving and sending and the corresponding electronic tag information are input to an edge calculation module;

(7) the positioning unmanned aerial vehicle edge calculation module accesses a database to obtain coordinate position information of a corresponding electronic tag;

(8) after receiving the electronic tag coordinate position information of the database, the edge calculation module of the positioning unmanned aerial vehicle rejects unreasonable data, retains at least three coordinate position information, obtains the coordinate position of the positioning unmanned aerial vehicle by using a TDOA (time difference of arrival) positioning and field intensity method, and further calculates the coordinate positions of other unmanned aerial vehicles by using the field intensity method;

(9) judging whether the signal intensity of an electronic tag of any unmanned aerial vehicle in the unmanned aerial vehicle cluster is attenuated to a threshold value, if so, selecting a proper position by the corresponding unmanned aerial vehicle by using an obstacle avoidance module and an image identification module and flying to the proper position, simultaneously informing a piloting unmanned aerial vehicle to control other unmanned aerial vehicles to hover and wait for the unmanned aerial vehicle to return, installing a new electronic tag at the new position, and recording the identity identification information and the coordinate position information of the electronic tag to a database; if not, returning to the step (2) until the unmanned aerial vehicle group arrives at the designated area or completes the flight task.

The positioning method is determined according to the number of the electronic tags, and when the number of the electronic tags is more than or equal to two, the position of the electronic tags is calculated by adopting a TDOA positioning method; when the number of the electronic tags is less than two or the positioning between the unmanned aerial vehicles is carried out, a field intensity method is adopted; and then, solving an equation set by adopting least square fitting, and selecting a solution closest to the last moment position of the unmanned aerial vehicle as the current moment coordinate position of the unmanned aerial vehicle.

The TDOA positioning method is that the absolute time difference distance from a radio frequency read-write module to every two electronic tags is calculated, and the calculation method is as follows:

wherein i and j are the serial numbers of the electronic tags and i is not equal to j, t_iThe time difference from the sending of a signal to the receiving of the ith electronic tag signal is given to the radio frequency read-write module, and c is the speed of light; (x)_i，y_i，z_i) Is the coordinate position of the ith electronic tag.

The field intensity method is that the radio frequency read-write module or the communication module respectively receives the signal intensity of a single electronic tag or an unmanned aerial vehicle to calculate the linear distance, and the calculation method comprises the following steps:

R_i＝-A_i+10·n_i·lg(d_i) (2)

R_ifor the signal strength value received by the ith unmanned aerial vehicle, A_iAnd n_iIs a letterA number propagation parameter; d_iThe distance between the ith unmanned aerial vehicle and the tag; (x)_i，y_i，z_i) And (4) positioning the coordinate position of the unmanned aerial vehicle for the ith electronic tag or the auxiliary positioning.

According to the unmanned aerial vehicle, the unmanned aerial vehicle can label in the flying process, automatic positioning and navigation can be realized in places with poor satellite signals, such as tunnels or caves, personal safety is guaranteed, and efficiency is improved. Particularly, the electronic tags can effectively reduce position fluctuation errors occurring in the hovering process of the auxiliary positioning unmanned aerial vehicle, and the electronic tags are used in a large amount in the application with higher positioning accuracy requirements; meanwhile, under the condition of the same quantity of the electronic tags, the more the unmanned aerial vehicle group is, the higher the positioning precision is.

The present invention is not limited to the embodiments described above, and it will be apparent to a person skilled in the art that any modifications or variations to the embodiments of the present invention described above are possible without departing from the scope of protection of the embodiments of the present invention and the appended claims, which are given by way of illustration only and are not intended to limit the invention in any way.