Abstract:
Disclosed is a vibration generating method includes providing a vibration generating device which receives a driving power and generates a vibration, and controlling vibration of a vibrator of the vibration generating device, wherein the vibration of the vibrator is controlled by systematizing an inertia matrix and a stiffness matrix of the vibrator, and wherein the inertia matrix and the stiffness matrix simultaneously satisfy diagonalization. A vibration generating device using this method is also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Korean Patent Application No. 10-2013-0080361, filed on Jul. 9, 2013, and all the benefits accruing therefrom under 35 U.S.C. §119, the contents of which in its entirety are herein incorporated by reference. 
     BACKGROUND 
     1. Field 
     The present disclosure relates to a multidirectional vibration generator using a single vibrator and its vibration generating method, and more particularly, to a single vibrator multidirectional vibration haptic feedback device giving a vibration effect with multidirectional frequencies according to a frequency of a driving source and a method for giving a haptic effect using a single vibrator. 
     2. Description of the Related Art 
     Generally, haptic feedback allows a user to feel sense of touch, force, motion or the like by means of a keyboard, a mouse, a joystick, a touch screen or the like. In particular, the technique in relation to touch feedback using the sense of touch on the skin may be relatively easily implemented, and this is widely applied to touch control interfaces of portable devices such as cellular phones, PDA or the like. In addition, the touch feedback improves the feeling of manipulation to a device and also gives the sense of reality and immersion to a user, and thus various techniques capable of implementing various kinds of touches are being developed. 
     In this tendency, many attempts are being made to diversify vibration effects of a vibration generating device, and particularly it is needed to develop a multi-mode vibration generating device capable of giving vibrations having a plurality of frequencies to a vibration generating device. 
       FIG. 9  shows an example of a general haptic feedback device. The general haptic feedback device depicted in  FIG. 9  uses four vibrators  201 ,  202 ,  203 ,  204 . If a specific point  200  is touched by a user, a width  211 ,  212  and a height  213 ,  214  are measured and calculated based on the touched specific point  200 , so that the vibrators  201 ,  202 ,  203 ,  204  have different values depending on a touched location. 
     However, this device uses a plurality of vibrators  201 ,  202 ,  203 ,  204 , and thus it is difficult to design the entire device or system in a small size. 
     In addition,  FIG. 10  shows another example of a general haptic feedback device. The haptic feedback device depicted in  FIG. 10  includes an input unit  301 , a control unit  304 , a vibrator driving unit  305 , a first vibrator  302 , and a second vibrator  303 . The first vibrator  302  and the second vibrator  303  may vibrate to generate a vibration stimulus when a driving signal of the vibrator driving unit  305  varies. 
     Moreover, in this device, vibration stimuli generated at specific frequencies of first and second vibrators are synthetically exhibited as shown in  FIG. 11 . In other words, the synthetic vibration of the first vibrator  302  and the second vibrator  303  are shown as the sum of vibrations of a vibration frequency having an absolute value (|f1-f2|) which is a difference between a first vibration frequency (f 1 ) and a second vibration frequency (f 2 ) and vibrations of a frequency having a mean value ((f1+f2)/2) of the first vibration frequency (f 1 ) and the second vibration frequency (f 2 ). 
     However, as shown in  FIG. 11 , in this device, a vibration desired by a user may not be easily generated other than the vibrations of a vibration frequency having an absolute value (|f1-f2|) which is a difference between the first vibration frequency (f 1 ) and the second vibration frequency (f 2 ) and the vibrations of a frequency having a mean value ((f1+f2)/2) of the first vibration frequency (f 1 ) and the second vibration frequency (f 2 ), and even though vibrations are generated, their magnitudes are very small. 
     In addition, since two vibrators are used as described above, it is still difficult to design the entire device or system in a small size. 
     Next,  FIG. 12  shows another example of a general haptic feedback device, which particularly includes a single vibration driving unit. In other words, this device includes an electromagnetic circuit  404  for receiving a driving power and generating an electromagnetic force, a driving unit  403  disposed at an upper portion of the electromagnetic circuit to vibrate in a plurality of vibration frequencies according to the frequency of the driving power, and a case unit  400  surrounding the electromagnetic circuit and the driving unit. 
     However, this device also includes two vibration modes (for example, an x-axis mode and a y-axis mode) having different inherent vibration frequencies f 1  and f 2  as shown in  FIG. 13  so that a vibration effect is implemented with a waveform where f 1  and f 2  are synthesized. In addition, a vibration desired by a user may not be easily generated other than the inherent vibration frequencies, and even though vibrations are generated, their magnitudes are very small. 
     RELATED LITERATURES 
     Patent Literature 
     
         
         1. Korean Unexamined Patent Publication No. 10-2010-0104975 
         2. Korean Patent Registration No. 10-1097782 
         3. Korean Unexamined Patent Publication No. 10-2013-0010591 
       
    
     SUMMARY 
     The present disclosure is directed to providing a multidirectional vibration generator using a single vibrator and its vibration generating method, which allows a small design and may generate a vibratory motion in a desired direction just by changing a frequency using the single vibrator. 
     The present disclosure is also directed to providing a multidirectional vibration generator using a single vibrator and its vibration generating method, which may generate a vibratory motion in a desired form not only at resonance points but also in a frequency band therebetween by directly designing a system having a desired resonance frequency and locating two or more resonance frequencies at desired locations, and also may generate a uniform amplitude even in a driving frequency band. 
     In one aspect, there is provided a vibration generating method, which includes: providing a vibration generating device which receives a driving power and generates a vibration; and controlling vibration of a vibrator of the vibration generating device, wherein the vibration of the vibrator is controlled by systematizing an inertia matrix and a stiffness matrix of the vibrator, and wherein the inertia matrix and the stiffness matrix simultaneously satisfy diagonalization. 
     In addition, the vibration generating device may be a 4-bar mechanism spring damper systems disposed at both sides of the vibrator in parallel in a vertical direction, vertical distances from a center of the vibrator to the upper spring damper system and the lower spring damper system may be identical, and a spring constant (k 1 ) of the upper spring damper system may be identical to a spring constant (k 2 ) of the lower spring damper system. 
     In addition, a vibration frequency (ω) of the vibrator may be determined, and a motion of the vibrator may be determined by designing spring constants and vertical distances of the upper and lower spring damper systems. 
     In addition, the vibrator of the vibration generating device may be a single vibrator. 
     In addition, a vertical spring damper system may be added to a lower portion of the center of the vibrator, and the 4-bar mechanism may be replaced with an eccentric motor or a piezoelectric vibration body. 
     In another aspect, there is provided a vibration generating device for receiving a driving power and generating a vibration by means of an electromagnetic force, which includes: a motor for generating a power with the received driving power; a vibrator connected to a vibration frame connected to the motor to vibrate according to a frequency of the motor; and a plurality of spring damper systems disposed at both sides of the vibrator, wherein the vibration generating device uses the vibration generating method defined in the claim  1 . 
     In the present disclosure, a vibration device or system capable of generating a vibratory motion in a desired direction just by changing a frequency using the single vibrator may be designed in a small size. 
     In addition, since the present disclosure is based on the analytical designing technique and does not use a resonance frequency obtained through interpretation, a system having a desired resonance frequency may be directly designed. 
     In addition, in the present disclosure, two or more resonance frequencies may be located at desired locations, so that a vibratory motion in a desired form may be generated not only at resonance points but also in a frequency band therebetween, and a uniform amplitude may be generated in a driving frequency band. 
     In addition, since the vibration generating device of the present disclosure may widen an available frequency band by obtaining a vibratory motion in a desired form with an uniform amplitude even in a frequency band between resonance points, linearity of the change of a motion direction according to the change of frequency greatly increases, easier control is ensured, and the performance of the vibration generating device may be improved. 
     In addition, since the vibration generating device of the present disclosure implements multidirectional vibrations by driving a single vibrator and just needs a simple speed control system, the present disclosure may be a great help in reducing a size of a haptic device of mobile terminals or game consoles which require the transfer of various touches. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view schematically showing a vibration generating device according to an embodiment of the present disclosure. 
         FIG. 2  is a systemically modeled diagram schematically showing the vibration generating device depicted in  FIG. 1 . 
         FIG. 3  is a diagram schematically showing a vibration direction according to each vibration frequency of the vibration generating device depicted in  FIGS. 1 and 2 . 
         FIG. 4  is a diagram schematically showing a concept of the vibration generating device depicted in  FIGS. 1 and 2 . 
         FIG. 5  is a graph showing a displacement motion according to the change of frequency of a vibrator in the vibration generating device depicted in  FIGS. 1 and 2 . 
         FIG. 6  is a graph showing the change of a vibration center point according to the increase of a driving frequency of the vibration generating device depicted in  FIGS. 1 and 2 . 
         FIG. 7  is a diagram schematically showing a vibration generating device according to another embodiment of the present disclosure. 
         FIG. 8  is a graph showing the change of a vibration center point according to the increase of a driving frequency of a vibrator in the vibration generating device another embodiment of the present disclosure depicted in  FIG. 7 . 
         FIG. 9  is a diagram schematically showing an example of a general haptic feedback device. 
         FIG. 10  is a diagram schematically showing another example of a general haptic feedback device. 
         FIG. 11  is a graph showing that vibration stimuli of vibrators of the general haptic feedback device depicted in  FIG. 10  are synthesized. 
         FIG. 12  is a perspective view showing a haptic feedback device including a single vibration driving unit according to another example of a general haptic feedback device. 
         FIG. 13  is a graph showing that a vibration stimulus according to each vibration frequency of the general haptic feedback device depicted in  FIG. 12 . 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, a multidirectional vibration generator using a single vibrator and its vibration generating method according to an embodiment of the present disclosure will be described through preferred embodiments. 
     Prior to description, in various embodiments, components having the same configuration is endowed with the same reference sign and representatively explained in one embodiment, and other components will be described in other embodiments. 
       FIG. 1  is a perspective view schematically showing a vibration generating device  1  according to an embodiment of the present disclosure. As shown in  FIG. 1 , it may be understood that the vibration generating device  1  of the present disclosure receives a driving force of a motor  18  so that a vibrator  12  vibrates, and the vibration is output through an output unit  13 . 
     In more detail, a frequency in a desired vibration direction is determined by a controller (not shown), and a control signal is sent to the motor  18  through an amplifier (not shown). As shown in  FIG. 1 , in the motor  18 , a crank  17 , a coupler  16 , and a rocker  19  are mechanically connected in order. If the motor  18  is driven through the control signal, the vibration of the motor vibrates the crank  17 , the coupler  16 , and the rocker  19  in order. 
     In addition, the rocker  19  is mechanically connected to a vibration frame  11  through a rocker fixing unit  191 , and as a result, the vibration initiated from the motor  18  vibrates the vibration frame  11 . 
     A vibrator  12  is disposed at a center of the vibration frame  11 , and the vibrator  12  is mechanically connected to the vibration frame  11  through a spring  14  and a damper  15  mechanically connected to both side ends of the vibrator. In an embodiment of the present disclosure, the spring and damper  14 ,  15  use two springs and dampers at one side, respectively for upper and lower portions, namely four springs and dampers  14 ,  15  in total. In addition, even though an embodiment of the present disclosure employs the motor  18  and the vibrator  12  connected to four springs and dampers  14 ,  15 , a person skilled in the art may also use other kinds of vibration generating mechanisms, for example an eccentric motor or a piezoelectric vibrator. 
     As described above, the vibration of the vibration frame  11  is transferred to the vibrator  12  through the spring  14  and the damper  15 . Here, the spring  14  and the damper  15  may be made of elastic material capable of transferring the vibration of the vibration frame  11  to the vibrator  12 , without being limited thereto. 
     At this time, the vibration of the vibrator  12  is made by means of an external force transferred through the spring  14  and the damper  15 , and the vibration of the vibrator  12  is generated according to a frequency response characteristic with respect to a force component. 
     In addition, the vibration of the vibrator  12  is transferred to the output unit  13  through an output connection unit  131 , and a user finally feels the vibration through the output unit  13 . 
       FIG. 2  is a systemically modeled diagram schematically showing the vibration generating device depicted in  FIG. 1 , and as essential components of the vibration generating device  1  of the present disclosure, only the vibration frame  11 , the vibrator  12 , the output unit  13 , the spring and damper  14 ,  15 , and the motor  18  are depicted schematically. 
     In addition,  FIG. 3  is a diagram schematically showing a vibration direction or the like according to each vibration frequency of the vibration generating device depicted in  FIGS. 1 and 2 . As shown in  FIG. 3 , in the vibration generating device according to an embodiment of the present disclosure, different vibration directions of the output unit  13  were observed when the frequency of the motor  18  was changed to 3.98 Hz, 4.93 Hz, 5.41 Hz, and 7.00 Hz, respectively. 
       FIG. 4  is a diagram schematically showing a mathematical concept of the vibration generating device depicted in  FIGS. 1 and 2 . For easier explanation, among the entire components of the vibration generating device  1 , the motor  18 , the vibration frame  11 , and the vibrator  12  are depicted, and the spring and damper  14 ,  15  are depicted as physical symbols used in the art. 
     Here, the vibration frequency of the motor  18  is marked as “ω”, elastic modulus of the upper and lower springs and dampers  14 ,  15  are marked as “k 1 ”, “k 2 ”, respectively, and the mass and the moment of inertia of the vibrator  12  are marked as “m” and “j”, respectively. In addition, a vertical distance from the center of the vibrator  12  to the upper spring and damper is marked as “h 1 ”, and a vertical distance to the lower spring and damper is marked as “h 2 ”. 
     The inertia matrix and the stiffness matrix through this system may be expressed as follows. 
     
       
         
           
             
               
                 
                   
                     M 
                     = 
                     
                       [ 
                       
                         
                           
                             m 
                           
                           
                             0 
                           
                           
                             0 
                           
                         
                         
                           
                             0 
                           
                           
                             m 
                           
                           
                             0 
                           
                         
                         
                           
                             0 
                           
                           
                             0 
                           
                           
                             j 
                           
                         
                       
                       ] 
                     
                   
                   , 
                   
                     
 
                   
                   ⁢ 
                   
                     K 
                     = 
                     
                       [ 
                       
                         
                           
                             
                               
                                 k 
                                 1 
                               
                               + 
                               
                                 k 
                                 2 
                               
                             
                           
                           
                             0 
                           
                           
                             
                               
                                 
                                   h 
                                   1 
                                 
                                 ⁢ 
                                 
                                   k 
                                   1 
                                 
                               
                               + 
                               
                                 
                                   h 
                                   2 
                                 
                                 ⁢ 
                                 
                                   k 
                                   2 
                                 
                               
                             
                           
                         
                         
                           
                             0 
                           
                           
                             0 
                           
                           
                             0 
                           
                         
                         
                           
                             
                               
                                 
                                   h 
                                   1 
                                 
                                 ⁢ 
                                 
                                   k 
                                   1 
                                 
                               
                               + 
                               
                                 
                                   h 
                                   2 
                                 
                                 ⁢ 
                                 
                                   k 
                                   2 
                                 
                               
                             
                           
                           
                             0 
                           
                           
                             
                               
                                 
                                   h 
                                   1 
                                   2 
                                 
                                 ⁢ 
                                 
                                   k 
                                   1 
                                 
                               
                               + 
                               
                                 
                                   h 
                                   2 
                                   2 
                                 
                                 ⁢ 
                                 
                                   k 
                                   2 
                                 
                               
                             
                           
                         
                       
                       ] 
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     1 
                   
                   ] 
                 
               
             
           
         
       
     
     Here, assuming that “k 1 =k 2 ”, “h 2 =−h 1 ”, an inherent vibration frequency and a mode vector of this system may be obtained as follows. 
     
       
         
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                   
                 Inherent frequency 
                 Mode vector 
               
               
                   
               
             
             
               
                 Mode 1 
                 
                   
                     
                       
                         
                           ω 
                           1 
                           2 
                         
                         = 
                         
                           
                             2 
                             ⁢ 
                             
                               kh 
                               2 
                             
                           
                           j 
                         
                       
                     
                   
                 
                 {circumflex over (x)} 1  = [0 0 1] T   
               
               
                   
               
               
                 Mode 2 
                 
                   
                     
                       
                         
                           ω 
                           2 
                           2 
                         
                         = 
                         
                           
                             2 
                             ⁢ 
                             k 
                           
                           m 
                         
                       
                     
                   
                 
                 {circumflex over (x)} 2  = [1 0 0] T   
               
               
                   
               
             
          
         
       
     
     In addition, in [Table 1], the stiffness and installation locations of the spring and damper  14 ,  15  may be determined by setting desired “1” and “2” and deciding “k” and “h” satisfying them. 
     The system designed in this way may be calculated using [Equation 2] below as the vibration frequency of the vibrator  12  varies. 
     
       
         
           
             
               
                 
                   
                     
                       
                         
                           δ 
                           ⁢ 
                           
                             X 
                             ^ 
                           
                         
                         = 
                           
                         ⁢ 
                         
                           
                             ∑ 
                             
                               y 
                               = 
                               1 
                             
                             2 
                           
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           
                             
                               
                                 
                                   
                                     X 
                                     ^ 
                                   
                                   y 
                                   T 
                                 
                                 ⁢ 
                                 δ 
                                 ⁢ 
                                 
                                   
                                     ω 
                                     ^ 
                                   
                                   ext 
                                 
                               
                               
                                 
                                   ( 
                                   
                                     
                                       
                                         k 
                                         ~ 
                                       
                                       y 
                                     
                                     - 
                                     
                                       
                                         
                                           m 
                                           ~ 
                                         
                                         y 
                                       
                                       ⁢ 
                                       
                                         Ω 
                                         2 
                                       
                                     
                                   
                                   ) 
                                 
                                 + 
                                 
                                   ⅈ 
                                   ⁡ 
                                   
                                     ( 
                                     
                                       
                                         
                                           c 
                                           ~ 
                                         
                                         y 
                                       
                                       ⁢ 
                                       Ω 
                                     
                                     ) 
                                   
                                 
                               
                             
                             ⁢ 
                             
                               
                                 X 
                                 ^ 
                               
                               y 
                             
                           
                         
                       
                     
                   
                   
                     
                       
                         = 
                           
                         ⁢ 
                         
                           [ 
                           
                             
                               
                                 
                                   
                                     2 
                                     ⁢ 
                                     kp 
                                   
                                   
                                     
                                       ( 
                                       
                                         
                                           2 
                                           ⁢ 
                                           k 
                                         
                                         - 
                                         
                                           m 
                                           ⁢ 
                                           
                                               
                                           
                                           ⁢ 
                                           
                                             Ω 
                                             2 
                                           
                                         
                                       
                                       ) 
                                     
                                     + 
                                     
                                       ⅈ 
                                       ⁡ 
                                       
                                         ( 
                                         
                                           2 
                                           ⁢ 
                                           c 
                                           ⁢ 
                                           
                                               
                                           
                                           ⁢ 
                                           Ω 
                                         
                                         ) 
                                       
                                     
                                   
                                 
                               
                             
                             
                               
                                 
                                   
                                     2 
                                     ⁢ 
                                     
                                       kh 
                                       2 
                                     
                                   
                                   
                                     
                                       ( 
                                       
                                         
                                           2 
                                           ⁢ 
                                           
                                             kh 
                                             2 
                                           
                                         
                                         - 
                                         
                                           j 
                                           ⁢ 
                                           
                                               
                                           
                                           ⁢ 
                                           
                                             Ω 
                                             2 
                                           
                                         
                                       
                                       ) 
                                     
                                     + 
                                     
                                       ⅈ 
                                       ⁡ 
                                       
                                         ( 
                                         
                                           2 
                                           ⁢ 
                                           
                                               
                                           
                                           ⁢ 
                                           
                                             ch 
                                             2 
                                           
                                           ⁢ 
                                           Ω 
                                         
                                         ) 
                                       
                                     
                                   
                                 
                               
                             
                           
                           ] 
                         
                       
                     
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                   ] 
                 
               
             
           
         
       
     
     Here, “p” means a y coordinate of the rocker fixing unit  191 . 
     In addition,  FIG. 5  is a graph showing a displacement motion according to the change of frequency of a vibrator through [Equation 1], [Equation 2] and [Table 1] in the vibration generating device depicted in  FIGS. 1 and 2 . As shown in  FIG. 5 , a displacement “dx” along an x-axis and a displacement “dy” along a y-axis are synthesized to exhibit an entire displacement “d”. In addition, as shown in  FIG. 5 , it may be found that a vibratory motion is exhibited not only at resonance points but also in a frequency band between them, and it may also be found that a uniform amplitude is observed in the entire driving frequency band. 
     Therefore, it may be understood that a band width of the vibration generating device according to an embodiment of the present disclosure is greatly improved. 
     In addition,  FIG. 6  is a graph showing the change of a vibration center point according to the increase of a driving frequency of the vibration generating device depicted in  FIGS. 1 and 2 . As shown in  FIG. 6 , it may be found that as the driving frequency of the vibration generating device increases, a vibration center moves along a y-axis where x=0 in an up-down-up pattern. 
       FIG. 7  is a diagram schematically showing a vibration generating device according to another embodiment of the present disclosure. As shown in  FIG. 7 , in another embodiment of the present disclosure, a spring is added to a lower portion of the vibrator  12  along a y-axis. 
     In addition, the stiffness “k 3 ” of the added spring may be determined to satisfy the following equation in consideration of a third frequency “ω 3 ” to be designed. 
     
       
         
           
             
               
                 
                   
                     ω 
                     3 
                     2 
                   
                   = 
                   
                     
                       2 
                       ⁢ 
                       k 
                     
                     m 
                   
                 
               
               
                 
                   [ 
                   
                     Equation 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     3 
                   
                   ] 
                 
               
             
           
         
       
     
     The change of a vibration center point according to another embodiment of the present disclosure is depicted in  FIG. 8 . As shown in  FIG. 8 , it may be understood that three vibration modes are used in another embodiment of the present disclosure, and more various vibration patterns are available with respect to a wide frequency band. 
     As described above, it will be understood by those skilled in the art that the present disclosure may be modified in various ways without changing its technical aspect or essential features. 
     Therefore, it should be understood that all the above embodiments are just for illustration only, not intended to limit the present disclosure, and the scope of the present disclosure is defined by the appended claims rather than the above detailed description. In addition, all changes or modifications derived from the meaning and range of the claims and their equivalents should be interpreted as falling within the scope of the present disclosure. 
     REFERENCE SIGNS 
     
         
           1  vibration generating device 
           11  vibration frame 
           12  vibrator 
           13  output unit 
           131  output connection unit 
           14  spring 
           15  damper 
           16  coupler 
           17  crank 
           18  motor 
           19  rocker 
           191  rocker fixing unit