Abstract:
The present invention provides a displacement monitoring system for a tower, the displacement monitoring system includes a tower displacement monitoring terminal and an underground displacement monitoring terminal electrically connected to the tower displacement monitoring terminal, the tower displacement monitoring terminal is arranged on the tower and includes a main control module, an overground tower displacement sensor, a power supply module and a communication module, wherein the overground tower displacement sensor, the power supply module and the communication module are electrically connected to the main control module respectively, the underground displacement monitoring terminal is arranged on an underground bedrock and includes a controlling module and an underground displacement sensor electrically connected to the controlling module. According the technical solution, displacement sensors are used to monitor the displacement values of the tower and the bedrock respectively, then the displacement value of the tower relative to the bedrock is computed based on the displacement values of the tower and the bedrock, this technical solution overcomes the one-sidedness of only monitoring the incline angle of the tower, and is a more comprehensive monitoring solution. Thus the displacement value of the tower can be accurately monitored on line, the actual state of the tower can be monitored, and therefore it is beneficial for further plan and build of national grid.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present invention relates to an online monitoring technology for monitoring states of power transmission equipment, and more particularly, to a displacement monitoring system for a tower and monitoring method thereof. 
         [0003]    2. Description of Related Art 
         [0004]    Due to effects of natural conditions and geological disasters, kinds of accidents of towers for high-voltage power transmission lines occur, for example, to incline towers, move towers, severely, break towers or collapse towers. Once those accidents occur, major and extraordinarily big accidents of a power grid will occur, which causes great economic loss for a country. Therefore, it is important and necessary to quickly determine whether the towers incline or move and give a warning. 
         [0005]    At present, kinds of technologies, such as a laser, a far infrared or dual-axis incline angle transducer, are used to measure an incline angle of the tower, thus an incline state of the tower can be monitored in real time. However, the above monitoring technologies only can be used for measuring the incline angle of the tower when the tower has inclined, a horizontal or vertical displacement of the tower occurred during an earthquake or landslide can&#39;t be monitored. Thus the prior monitoring method only can be used to measure the incline angle, but it can&#39;t be used to measure the horizontal or vertical displacement, therefore the real state of the tower can&#39;t be monitored by the prior online monitoring method at the beginning of changes of geological environment in the area in which the tower is located. 
       Technical Problem 
       [0006]    A technical problem to be solved by the present invention is to overcome that the horizontal or vertical displacement can&#39;t be monitored and provide a displacement monitoring system for a tower, used to monitor the horizontal or vertical displacement of the tower. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    The present invention provides a displacement monitoring system for a tower, wherein the displacement monitoring system includes a tower displacement monitoring terminal and an underground displacement monitoring terminal electrically connected to the tower displacement monitoring terminal; 
         [0008]    the tower displacement monitoring terminal is arranged on the tower, comprising a main control module, an overground tower displacement sensor, a power supply module and a communication module, wherein the overground tower displacement sensor, the power supply module and the communication module are electrically connected to the main control module; 
         [0009]    the underground displacement monitoring terminal is arranged on an underground bedrock, including a controlling module and an underground displacement sensor electrically connected to the controlling module; 
         [0010]    the underground displacement sensor is configured to monitor a motion acceleration of the bedrock within a predetermined time t; 
         [0011]    the controlling module is configured to compute a displacement value of the bedrock within the predetermined time t based on the motion acceleration of the bedrock and transfer the displacement value to the main control module; 
         [0012]    the overground tower displacement sensor is configured to monitor a motion acceleration of the tower within the predetermined time t; 
         [0013]    the main control module is configured to compute a displacement value of the tower within the predetermined time t based on the motion acceleration of the tower and compute a displacement value of the tower relative to the bedrock based on the displacement value of the bedrock; 
         [0014]    the power supply module is configured to power the tower displacement monitoring terminal and the underground displacement monitoring terminal; and 
         [0015]    the communication module is configured to send displacement values received and computed by the main control module to a remote monitoring terminal under control of the main control module. 
         [0016]    Preferably, the overground tower displacement sensor and the underground tower displacement sensor are a tri-axial acceleration sensor, respectively. 
         [0017]    Preferably, the power supply module comprises: 
         [0018]    a wind power generation module, configured to generate electricity by wind; 
         [0019]    a solar power generation module, configured to generate electricity by the sun; 
         [0020]    an accumulator; and 
         [0021]    a charging management module; 
         [0022]    wherein the wind power generation module, the solar power generation module and the accumulator are respectively connected to the charging management module. 
         [0023]    Preferably, the tower displacement monitoring terminal further comprises a storage module, a display module, a reset module and a clock module, wherein the storage module, the display module, the reset module and the clock module are electrically connected to the main control module; 
         [0024]    the storage module is configured to store data computed by the main control module; 
         [0025]    the display module is configured to locally display the date; 
         [0026]    the reset module is configured to perform a reset operation to the tower displacement monitoring terminal; and 
         [0027]    the clock module is configured to provide a unified work clock for the tower displacement monitoring terminal and synchronize the clock. 
         [0028]    Preferably, the underground displacement monitoring terminal further comprises a memorizer, a reset and clock module, wherein the memorizer, the reset and clock module are electrically connected to the main control module; 
         [0029]    the memorizer is configured to store data computed by the controlling module; 
         [0030]    the reset and clock module is configured to perform a reset operation to the underground displacement monitoring terminal, and provide a unified work clock for the underground displacement monitoring terminal and synchronize the clock. 
         [0031]    Preferably, the main control module is communicated with the controlling module by RS485 bus. 
         [0032]    The present invention further provides a monitoring method of a displacement monitoring system for a tower, wherein the monitoring method includes: 
         [0033]    Monitoring and computing a displacement value of the tower; 
         [0034]    Monitoring and computing a displacement value of an underground reference point; 
         [0035]    Computing a displacement value of the tower relative to the reference point based on the displacement value of the tower and the displacement value of the underground reference point; 
         [0036]    Sending the displacement value of the tower, the displacement value of the underground reference point and the displacement value of the tower relative to the underground reference point to a remote monitoring terminal; 
         [0037]    Wherein the underground reference point is a position of an underground displacement sensor arranged on an underground bedrock. 
         [0038]    Preferably, the step of monitoring and computing a displacement value of the tower comprises: 
         [0039]    Monitoring motion accelerations a x , a y  and a z  respectively along three axes within a predetermined time t, and computing displacement values D x , D y  and D z  along the three axes within the predetermined time t, wherein a x , a y  and a z  are motion accelerations respectively along X axis, Y axis and Z axis, D x , D y  and D Z  are displacement values respectively along X axis, Y axis and Z axis; 
         [0040]    wherein the X axis and Y axis are two coordinate axes perpendicular to each other in a horizontal direction, the Z axis is a coordinate axis across an intersection of the X axis and the Y axis in a vertical direction. 
         [0041]    Preferably, the step of monitoring and computing a displacement value of an underground reference point comprises: 
         [0042]    Monitoring motion accelerations b x , b y  and b z  of the underground reference point respectively along the X axis, Y axis and Z axis within the predetermined time t, and computing displacement values T x , T y  and T z  of the underground reference point along the X axis, Y axis and Z axis within the predetermined time t. 
         [0043]    Preferably, the step of computing a displacement value of the tower relative to the reference point based on the displacement value of the tower and the displacement value of the underground reference point comprises: 
         [0044]    Computing a displacement value of the tower relative to the reference point along the X axis by expression L x =D x −T x ; 
         [0045]    Computing a displacement value of the tower relative to the reference point along the Y axis by expression L y =D y −T y ; and 
         [0046]    Computing a displacement value of the tower relative to the reference point along the Z axis by expression L z =D z −T z . 
         [0047]    Preferably, the step of computing displacement values D x , D y  and D z  along the X axis, Y axis and Z axis within the predetermined time t comprises: 
         [0048]    Computing the displacement value of the tower along the X axis by expression 
         [0000]    
       
         
           
             
               
                 D 
                 x 
               
               = 
               
                 
                   
                     V 
                     x 
                   
                    
                   t 
                 
                 + 
                 
                   
                     1 
                     2 
                   
                    
                   
                     a 
                     x 
                   
                    
                   
                     t 
                     2 
                   
                 
               
             
             , 
           
         
       
     
         [0000]    wherein when the displacement value of the tower along the X axis is computed at the first time, the value of V x  is zero, and in following computation of the displacement value of the tower along the X axis the value of V x  is a speed of the tower at the end of previous computation of the displacement value of the tower along the X axis and is computed by expression V x =V′ x +a′ x t, wherein V′ x  is an initial value in the previous computation of the displacement value of the tower along the X axis, a′ x  is a motion acceleration of the tower along the X axis obtained from the previous computation of the displacement value of the tower along the X axis; 
         [0049]    Computing the displacement value of the tower along the Y axis by expression 
         [0000]    
       
         
           
             
               
                 D 
                 y 
               
               = 
               
                 
                   
                     V 
                     y 
                   
                    
                   t 
                 
                 + 
                 
                   
                     1 
                     2 
                   
                    
                   
                     a 
                     y 
                   
                    
                   
                     t 
                     2 
                   
                 
               
             
             , 
           
         
       
     
         [0000]    wherein when the displacement value of the tower along the Y axis is computed at the first time, the value of V y  is zero, and in following computation of the displacement value of the tower along the Y axis the value of V y  is a speed of the tower at the end of previous computation of the displacement value of the tower along the Y axis and is computed by expression V y =V′ y +a′ y t, wherein V′ y  is an initial value in the previous computation of the displacement value of the tower along the Y axis, a′ y  is a motion acceleration of the tower along the Y axis obtained from the previous computation of the displacement value of the tower along the Y axis; and 
         [0050]    Computing the displacement value of the tower along the Z axis by expression 
         [0000]    
       
         
           
             
               
                 D 
                 z 
               
               = 
               
                 
                   
                     V 
                     z 
                   
                    
                   t 
                 
                 + 
                 
                   
                     1 
                     2 
                   
                    
                   
                     a 
                     z 
                   
                    
                   
                     t 
                     2 
                   
                 
               
             
             , 
           
         
       
     
         [0000]    wherein when the displacement value of the tower along the Z axis is computed at the first time, the value of V z  is zero, and in following computation of the displacement value of the tower along the Z axis the value of V z  is a speed of the tower at the end of previous computation of the displacement value of the tower along the Z axis and is computed by expression V z =V′ z +a′ z t, wherein V′ z  is an initial value in the previous computation of the displacement value of the tower along the Z axis, a′ z  is a motion acceleration of the tower along the Z axis obtained from the previous computation of the displacement value of the tower along the Z axis. 
         [0051]    Preferably, the step of computing displacement values T x , T y  and T z  of the underground reference point along the X axis, Y axis and Z axis within the predetermined time t comprises: 
         [0052]    Computing the displacement value of the underground reference point along the X axis by expression 
         [0000]    
       
         
           
             
               
                 T 
                 x 
               
               = 
               
                 
                   
                     U 
                     x 
                   
                    
                   t 
                 
                 + 
                 
                   
                     1 
                     2 
                   
                    
                   
                     b 
                     x 
                   
                    
                   
                     t 
                     2 
                   
                 
               
             
             , 
           
         
       
     
         [0000]    wherein when the displacement value of the underground reference point along the X axis is computed at the first time, the value of U x  is zero, and in following computation of the displacement value of the tower along the X axis the value of U x  is a speed of the underground reference point at the end of previous computation of the displacement value of the underground reference point along the X axis and is computed by expression T x =U′ x +b′ x t, wherein U′ x  is an initial value in the previous computation of the displacement value of the underground reference point along the X axis, b′ x  is a motion acceleration of the underground reference point along the X axis obtained from the previous computation of the displacement value of the underground reference point along the X axis; 
         [0053]    Computing the displacement value of the underground reference point along the Y axis by expression 
         [0000]    
       
         
           
             
               
                 T 
                 y 
               
               = 
               
                 
                   
                     U 
                     y 
                   
                    
                   t 
                 
                 + 
                 
                   
                     1 
                     2 
                   
                    
                   
                     b 
                     y 
                   
                    
                   
                     t 
                     2 
                   
                 
               
             
             , 
           
         
       
     
         [0000]    wherein when the displacement value of the underground reference point along the Y axis is computed at the first time, the value of U y  is zero, and in following computation of the displacement value of the tower along the Y axis the value of U y  is a speed of the underground reference point at the end of previous computation of the displacement value of the underground reference point along the Y axis and is computed by expression T y =U′ y +b y t, wherein U′ y  is an initial value in the previous computation of the displacement value of the underground reference point along the Y axis, b′ y  is a motion acceleration of the underground reference point along the Y axis obtained from the previous computation of the displacement value of the underground reference point along the Y axis; and 
         [0054]    Computing the displacement value of the underground reference point along the Z axis by expression 
         [0000]    
       
         
           
             
               
                 T 
                 z 
               
               = 
               
                 
                   
                     U 
                     z 
                   
                    
                   t 
                 
                 + 
                 
                   
                     1 
                     2 
                   
                    
                   
                     b 
                     z 
                   
                    
                   
                     t 
                     2 
                   
                 
               
             
             , 
           
         
       
     
         [0000]    wherein when the displacement value of the underground reference point along the Z axis is computed at the first time, a value of U z  is zero, and in following computation of the displacement value of the tower along the Z axis the value of U z  is a speed of the underground reference point at the end of previous computation of the displacement value of the underground reference point along the Z axis and is computed by expression T z =U′ z +b′ z t, wherein U′ z  is an initial value in the previous computation of the displacement value of the underground reference point along the Z axis, b′ z  is a motion acceleration of the underground reference point along the Z axis obtained from the previous computation of the displacement value of the underground reference point along the Z axis. 
         [0055]    Preferably, the method further comprises: 
         [0056]    Computing an actual displacement value S of the tower relative to the reference point in the horizontal direction by expression S=√{square root over (L x   2 +L y   2 )}based on the displacement value of the tower relative to the reference point along the X axis L x =D x −T x  and the displacement value of the tower relative to the reference point along the Y axis L y =D y −T y , and computing a deviation angle of the tower relative to the X axis by expression 
         [0000]    
       
         
           
             θ 
             = 
             
               
                 arcsin 
                 ( 
                 
                   
                     L 
                     y 
                   
                   
                     
                       
                         L 
                         x 
                         2 
                       
                       + 
                       
                         L 
                         y 
                         2 
                       
                     
                   
                 
                 ) 
               
               . 
             
           
         
       
     
         [0057]    The present invention has the following benefits: according the technical solution of the present invention, displacement sensors are used to monitor the displacement values of the tower and the bedrock respectively, then the displacement value of the tower relative to the bedrock is computed based on the displacement values of the tower and the bedrock, this technical solution overcomes the one-sidedness of only monitoring the incline angle of the tower, and is a more comprehensive monitoring solution. Thus the displacement value of the tower can be accurately monitored on line, the actual state of the tower can be monitored, and therefore it is beneficial for further plan and build of national grid. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0058]      FIG. 1  is a structure diagram of a first embodiment of a displacement monitoring system for a tower according to the present invention; 
           [0059]      FIG. 2  is a structure diagram of a second embodiment of a dis placement monitoring system for a tower according to the present invention; 
           [0060]      FIG. 3  is a structure diagram of a third embodiment of a displacement monitoring system for a tower according to the present invention; 
           [0061]      FIG. 4  is a schematic view of a position relation between a tower and an underground reference point of a displacement monitoring system for a tower according to an embodiment of the present invention; and 
           [0062]      FIG. 5  is a schematic view of a displacement relation of a displacement monitoring system for a tower in an horizontal coordinate axis according to the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0063]    In order to make clearer the objects, technical solutions and advantages of the invention, the present invention will be explained below in detail with reference to the accompanying drawings and embodiments. It is to be understood that the following description of the embodiments is merely to explain the present invention and is no way intended to limit the invention. 
         [0064]    Referring to  FIGS. 1 ,  2  and  3 , a displacement monitoring system for a tower in the present invention includes a tower displacement monitoring terminal  100  and an underground displacement monitoring terminal  200 , the tower displacement monitoring terminal  100  is electrically connected to the underground displacement monitoring terminal  200  and communicates with each other, the tower displacement monitoring terminal  100  is configured to monitor a displacement value of the tower, and the underground displacement monitoring terminal  200  is configured to monitor a displacement value of an underground bedrock  2 . 
         [0065]    Furthermore, combining with  FIG. 4 , the tower displacement monitoring terminal  100  is arranged on the tower  1  and can be placed on any position of the tower, for example, the tower displacement monitoring terminal  100  can be arranged on point A of the tower  1  shown in  FIG. 4 . In order to reduce monitoring errors of the tower displacement caused by influences of wind on the tower, the tower displacement monitoring terminal  100  should be arranged on a middle and lower position of the tower  1  as far as possible, the tower displacement monitoring terminal  100  includes a main control module  101 , an overground tower displacement sensor  102 , a power supply module  110  and a communication module  103 , wherein the overground tower displacement sensor  102  and the power supply module  110  and the communication module  103  are electrically connected to the main control module  101 , respectively. 
         [0066]    The underground displacement monitoring terminal  200  is arranged on an underground bedrock  2  and includes a controlling module  201  and an underground displacement sensor  202  electrically connected to the controlling module  201 . In order to reduce the length of a connecting wire between the tower displacement monitoring terminal  100  and the underground displacement monitoring terminal  200  as much as possible, the underground displacement monitoring terminal  200  can be arranged on a bedrock around the tower, for example, the underground displacement monitoring terminal  200  can be placed on point B of the underground bedrock  2  shown in  FIG. 4 , point B can be used as an underground reference point, that is, it is the position on which the underground displacement sensor  202  is placed. 
         [0067]    The underground displacement sensor  202  is configured to monitor a motion acceleration of the bedrock within a predetermined time t. 
         [0068]    The controlling module  201  is configured to compute a displacement value of the bedrock within the predetermined time t based on the motion acceleration of the bedrock  2  and transfer the displacement value to the main control module  101 . 
         [0069]    The overground tower displacement sensor  102  is configured to monitor a motion acceleration of the tower  1  within the predetermined time t. 
         [0070]    The main control module  101  is configured to compute a displacement value of the tower  1  within the predetermined time t based on the motion acceleration of the tower  1  and compute a displacement value of the tower  1  relative to the bedrock  2  based on the displacement value of the bedrock  2 . 
         [0071]    The power supply module  110  is configured to power the tower displacement monitoring terminal  100  and the underground displacement monitoring terminal  200 . 
         [0072]    The communication module  103  is configured to send displacement values received and computed by the main control module  101  to a remote monitoring terminal (not shown in figures) under the control of the main control module  101 . 
         [0073]    Preferably, the overground tower displacement sensor  102  and the underground tower displacement sensor  202  are a tri-axial acceleration sensor respectively, namely, the overground tower displacement sensor  102  can be used to monitor motion accelerations of the tower along three axes, the three axes are X coordinate axis, Y coordinate axis and Z coordinate axis, the X coordinate axis and Y coordinate axis are two coordinate axes perpendicular to each other in a horizontal direction, for example, if the X coordinate axis is an axis along east-west direction, the Y axis is an axis along north-south direction, the Z axis is a coordinate axis across an intersection of the X axis and the Y axis in a vertical direction, the Z axis are perpendicular to the X axis and the Y axis respectively. Similarly, the underground tower displacement sensor  202  can be configured to monitor motion accelerations of the bedrock  2  along the X coordinate axis, Y coordinate axis and Z coordinate axis. 
         [0074]    The controlling module  201  can respectively compute displacement values T x , T y  and T z  of the bedrock along the X axis, Y axis and Z axis based on motion accelerations b x , b y  and b z  along the X axis, Y axis and Z axis monitored by the underground tower displacement sensor  202  and send the computed displacement values of the bedrock  2  to the main control module  101 . Preferably, the main control module  101  is communicated with the controlling module  201  by RS485 bus. Both the main control module  101  and the controlling module  201  can be a single chip microcomputer system. 
         [0075]    The main control module  101  can respectively compute displacement values D x , D y  and D z  of the tower  1  along the X axis, Y axis and Z axis based on motion accelerations a x , a y  and a z  respectively along the X axis, Y axis and Z axis monitored by the overground tower displacement sensor  102 . 
         [0076]    Furthermore, the main control module  101  also can respectively compute displacement values of the tower  1  along the X axis, Y axis and Z axis relative to the underground reference point based on displacement values D x , D y  and D z  of the tower  1  along the X axis, Y axis and Z axis and the displacement values T x , T y  and T z  of the bedrock  2  along the X axis, Y axis and Z axis, and obtain an actual displacement value of the tower relative to the underground reference point. 
         [0077]    As shown in  FIG. 3 , as another embodiment of the present invention, the tower displacement monitoring terminal  100  further includes a storage module  107 , a display module  106 , a reset module  105  and a clock module  104 , the storage module  107 , the display module  106 , the reset module  105  and the clock module  104  are electrically connected to the main control module  101  respectively, the storage module  107  is configured to store data computed by the main control module  101 , the data includes displacement values of the tower, displacement values of the bedrock and so on, the display module  106  is configured to locally display the date, for example, to locally display displacement values of the tower  1  relative to the bedrock  2 , the reset module  105  is configured to perform a reset operation to the tower displacement monitoring terminal, and the clock module  104  is configured to provide a unified work clock for the tower displacement monitoring terminal and synchronize the clock. 
         [0078]    Furthermore, preferably, the power supply module  110  includes a wind power generation module  114  configured to generate electricity, or a solar power generation module  113  configured to generate electricity, an accumulator  112  and a charging management module  111 . The power supply module  110  can be a wind driven generator for converting wind energy to electrical energy, and the solar power generation module  113  can be solar panels for converting solar energy to electrical energy. 
         [0079]    The wind power generation module  114 , the solar power generation module  113  and the accumulator  112  are respectively connected to the charging management module  111 . The charging management module  111  can store the electrical energy converted by the wind power generation module  114  and the solar power generation module  113  to the accumulator  112 , the solar power generation module  113  and the accumulator  112  are connected to the charging management module  111  respectively. The charging management module  111  also can supply the electrical energy converted by the wind power generation module  114  and the solar power generation module  113  to the tower displacement monitoring terminal  100  and the underground displacement monitoring terminal  200 . At the same time, the charging management module  111  also can control the accumulator  112  to power the tower displacement monitoring terminal  100  and the underground displacement monitoring terminal  200 . 
         [0080]    Preferably, the underground displacement monitoring terminal  200  further includes a memorizer  203 , a reset and clock module  204 , the memorizer  203  and the reset and clock module  204  are electrically connected to the controlling module  201 , the memorizer  203  is configured to store data computed by the controlling module, the reset and clock module  204  is configured to perform a reset operation to the underground displacement monitoring terminal, and provide a unified work clock for the underground displacement monitoring terminal and synchronize the clock. 
         [0081]    The present invention further provides a monitoring method used for the above-mentioned displacement monitoring system for the tower, the monitoring method includes: 
         [0082]    monitoring and computing a displacement value of the tower; 
         [0083]    monitoring and computing a displacement value of an underground reference point; 
         [0084]    computing a displacement value of the tower relative to the underground reference point based on the displacement value of the tower and the displacement value of the underground reference point; 
         [0085]    sending the displacement value of the tower, the displacement value of the underground reference point and the displacement value of the tower relative to the underground reference point to a remote monitoring terminal; 
         [0086]    wherein the underground reference point is a position of an underground displacement sensor arranged on an underground bedrock. 
         [0087]    Preferably, the step of monitoring and computing a displacement value of the tower includes: 
         [0088]    monitoring motion accelerations a x , a y  and a z  respectively along three axes within a predetermined time t, and computing displacement values D x , D y  and D z  of the tower along the three axes within the predetermined time t, wherein a x , a y  and a z  are motion accelerations respectively along X axis, Y axis and Z axis, D x , D y  and D z  are displacement values respectively along X axis, Y axis and Z axis; 
         [0089]    wherein the X axis and Y axis are two coordinate axes perpendicular to each other in a horizontal direction, the Z axis is a coordinate axis across an intersection of the X axis and the Y axis in a vertical direction. The motion accelerations a x , a y  and a z  respectively along the X axis, Y axis and Z axis are measured by the overground tower displacement sensor  102 . 
         [0090]    Furthermore, the step of computing displacement values D x , D y  and D Z  of the tower along the X axis, Y axis and Z axis within the predetermined time t includes: Computing the displacement value of the tower along the X axis by expression 
         [0000]    
       
         
           
             
               
                 D 
                 x 
               
               = 
               
                 
                   
                     V 
                     x 
                   
                    
                   t 
                 
                 + 
                 
                   
                     1 
                     2 
                   
                    
                   
                     a 
                     x 
                   
                    
                   
                     t 
                     2 
                   
                 
               
             
             , 
           
         
       
     
         [0000]    wherein when the displacement value of the tower along the X axis is computed at the first time, the value of V x  is zero, and in following computation of the displacement value of the tower along the X axis the value of V x  is a speed of the tower at the end of previous computation of the displacement value of the tower along the X axis and is computed by expression V x =V′ x +a′ x t, wherein V′ x  is an initial value in the previous computation of the displacement value of the tower along the X axis, a′ x  is a motion acceleration of the tower along the X axis obtained from the previous computation of the displacement value of the tower along the X axis. For example, when the displacement value of the tower along the X axis is computed at the first time, the value of V x  is zero, after the displacement value of the tower along the X axis is computed at the first time, namely, after the time t the speed of the tower changes to a*t, wherein a is an acceleration measured during the computation of the displacement value of the tower along the X axis at the first time, therefore, when the displacement value of the tower along the X axis is computed at the second time, the value of V x  is a*t, after this computation, the speed of the tower changes to at+a′t, a′ is an acceleration measured during the computation of the displacement value of the tower along the X axis at the second time, by analogy, when the displacement value of the tower along the X axis is computed at every time, the value of V x  can be obtained. 
         [0091]    Computing the displacement value of the tower along the Y axis by expression 
         [0000]    
       
         
           
             
               
                 D 
                 y 
               
               = 
               
                 
                   
                     V 
                     y 
                   
                    
                   t 
                 
                 + 
                 
                   
                     1 
                     2 
                   
                    
                   
                     a 
                     y 
                   
                    
                   
                     t 
                     2 
                   
                 
               
             
             , 
           
         
       
     
         [0000]    wherein when the displacement value of the tower along the Y axis is computed at the first time, the value of V y  is zero, and in following computation of the displacement value of the tower along the Y axis the value of V y  is a speed of the tower at the end of previous computation of the displacement value of the tower along the Y axis and is computed by expression V y =V′ y +a′ y t, wherein V′ y  is an initial value in the previous computation of the displacement value of the tower along the Y axis, a′ y  is a motion acceleration of the tower along the Y axis obtained from the previous computation of the displacement value of the tower along the Y axis. 
         [0092]    Computing the displacement value of the tower along the Z axis by expression 
         [0000]    
       
         
           
             
               
                 D 
                 z 
               
               = 
               
                 
                   
                     V 
                     z 
                   
                    
                   t 
                 
                 + 
                 
                   
                     1 
                     2 
                   
                    
                   
                     a 
                     z 
                   
                    
                   
                     t 
                     2 
                   
                 
               
             
             , 
           
         
       
     
         [0000]    wherein when the displacement value of the tower along the Z axis is computed at the first time, the value of V z  is zero, and in following computation of the displacement value of the tower along the Z axis the value of V z  is a speed of the tower at the end of previous computation of the displacement value of the tower along the Z axis and is computed by expression V z =V′ z +a′ z t, wherein V′ z  is an initial value in the previous computation of the displacement value of the tower along the Z axis, a′ z  is a motion acceleration of the tower along the Z axis obtained from the previous computation of the displacement value of the tower along the Z axis. 
         [0093]    Preferably, the step of monitoring and computing a displacement value of an underground reference point comprises: 
         [0094]    Monitoring motion accelerations b x , b y  and b z  of the underground reference point respectively along the X axis, Y axis and Z axis within the predetermined time t, and computing displacement values T x , T y  and T z  of the underground reference point along the X axis, Y axis and Z axis within the predetermined time t. The motion accelerations b x , b y  and b z  of the underground reference point respectively along the X axis, Y axis and Z axis can be measured by the underground displacement sensor  202 . 
         [0095]    Furthermore, according to the principle of the computation of the displacement value of the tower, the step of computing displacement values T x , T y  and T z  of the underground reference point along the X axis, Y axis and Z axis within the predetermined time t comprises: 
         [0096]    Computing the displacement value of the underground reference point along P the X axis by expression 
         [0000]    
       
         
           
             
               
                 T 
                 x 
               
               = 
               
                 
                   
                     U 
                     x 
                   
                    
                   t 
                 
                 + 
                 
                   
                     1 
                     2 
                   
                    
                   
                     b 
                     x 
                   
                    
                   
                     t 
                     2 
                   
                 
               
             
             , 
           
         
       
     
         [0000]    wherein when the displacement value of the underground reference point along the X axis is computed at the first time, the value of U x  is zero, and in following computation of the displacement value of the tower along the X axis the value of U x  is a speed of the underground reference point at the end of previous computation of the displacement value of the underground reference point along the X axis and is computed by expression T x =U′ x +b′ x t, wherein U′ x  is an initial value in the previous computation of the displacement value of the underground reference point along the X axis, b′ x  is a motion acceleration of the underground reference point along the X axis obtained from the previous computation of the displacement value of the underground reference point along the X axis; 
         [0097]    Computing the displacement value of the underground reference point along the Y axis by expression 
         [0000]    
       
         
           
             
               
                 T 
                 y 
               
               = 
               
                 
                   
                     U 
                     y 
                   
                    
                   t 
                 
                 + 
                 
                   
                     1 
                     2 
                   
                    
                   
                     b 
                     y 
                   
                    
                   
                     t 
                     2 
                   
                 
               
             
             , 
           
         
       
     
         [0000]    wherein when the displacement value of the underground reference point along the Y axis is computed at the first time, the value of U y  is zero, and in following computation of the displacement value of the tower along the Y axis the value of U y  is a speed of the underground reference point at the end of previous computation of the displacement value of the underground reference point along the Y axis and is computed by expression T y =U′ y +b′ y t, wherein Y′ y  is an initial value in the previous computation of the displacement value of the underground reference point along the Y axis, b′ y  is a motion acceleration of the underground reference point along the Y axis obtained from the previous computation of the displacement value of the underground reference point along the Y axis; and 
         [0098]    Computing the displacement value of the underground reference point along the Z axis by expression 
         [0000]    
       
         
           
             
               
                 T 
                 z 
               
               = 
               
                 
                   
                     U 
                     z 
                   
                    
                   t 
                 
                 + 
                 
                   
                     1 
                     2 
                   
                    
                   
                     b 
                     z 
                   
                    
                   
                     t 
                     2 
                   
                 
               
             
             , 
           
         
       
     
         [0000]    wherein when the displacement value of the underground reference point along the Z axis is computed at the first time, a value of U z  is zero, and in following computation of the displacement value of the tower along the Z axis the value of U z  is a speed of the underground reference point at the end of previous computation of the displacement value of the underground reference point along the Z axis and is computed by expression T z =U′ z +b′ z t, wherein U′ z  is an initial value in the previous computation of the displacement value of the underground reference point along the Z axis, b′ z  is a motion acceleration of the underground reference point along the Z axis obtained from the previous computation of the displacement value of the underground reference point along the Z axis. 
         [0099]    Finally, the step of computing a displacement value of the tower relative to the reference point based on the displacement value of the tower and the displacement value of the underground reference point comprises: 
         [0100]    computing a displacement value of the tower relative to the reference point along the X axis by expression L x =D x −T x ; 
         [0101]    computing a displacement value of the tower relative to the reference point along the Y axis by expression L y =D y −T y ; and 
         [0102]    computing a displacement value of the tower relative to the reference point along the Z axis by expression L z =D z −T z . 
         [0103]    When an earthquake or other geological disasters occur, the ground will move, that is, a bedrock will move, therefore, it is desired to obtain the displacement value of the tower relative to the underground reference point. In the above-mentioned technical solution, according to objective attributes of geological disasters and the law of motion of objects, a monitoring period and the predetermined time t should be kept at millisecond level, the particular value ranges can be determined based on monitoring precision and the frequency of local geological disasters. 
         [0104]    By using the above-mentioned monitoring method, displacement values of the tower relative to the reference point along the X axis, Y axis, Z axis can be intuitively obtained, the main control module will send the displacement values of the tower along the X axis, Y axis, Z axis, the displacement values of the underground reference point along the X axis, Y axis, Z axis and the displacement values of the tower relative to the reference point along the X axis, Y axis, Z axis to a remote monitoring terminal by the communication module  103 , or display those information by the display module  106  included by the tower displacement monitoring terminal. 
         [0105]    Referring to  FIG. 5 , it is assumed that the positive direction of the X axis is east and the positive direction of the Y axis is north, an actual displacement value S of the tower relative to the reference point in the horizontal direction based on the displacement value of the tower relative to the reference point along the X axis and the displacement value of the tower relative to the reference point along the Y axis. For example, if the displacement value of the tower relative to the reference point along the X axis is L x  and the displacement value of the tower relative to the reference point along the Y axis is L y , the actual displacement value S of the tower relative to the reference point can be obtained by expression S=√{square root over (L x   2 +L y   2 )}, and a deviation angle of the tower relative to the X axis can be obtained by expression 
         [0000]    
       
         
           
             
               θ 
               = 
               
                 arcsin 
                 ( 
                 
                   
                     L 
                     y 
                   
                   
                     
                       
                         L 
                         x 
                         2 
                       
                       + 
                       
                         L 
                         y 
                         2 
                       
                     
                   
                 
                 ) 
               
             
             , 
           
         
       
     
         [0000]    that is, the tower deviates by the angle θ from east to north relative to the underground reference point. 
         [0106]    The present invention has been further detailed in the above descriptions with reference to the preferred embodiments; however, it shall not be construed that implementations of the present invention are only limited to these descriptions. Many simple deductions or replacements may further be made by those of ordinary skill in the art without departing from the conception of the present invention, and all of the deductions or replacements shall be considered to be covered within the protection scope of the present invention.