Patent Publication Number: US-2016241691-A1

Title: Portable device and position control method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation based on PCT Application No. PCT/JP2014/078469 filed on Oct. 27, 2014, which claims the benefit of Japanese Application No. 2013-223675 filed on Oct. 28, 2013. PCT Application No. PCT/JP2014/078469 is entitled “Portable Device And Posture Control Method”, and Japanese Application No. 2013-223675 is entitled “Portable Device and Position Control Method and Program”. The contents of which are incorporated by reference herein in their entirety. 
    
    
     FIELD 
     The present disclosure relates to a portable device such as a portable telephone, a personal digital assistant (PDA), a tablet PC, an electronic book terminal, a portable music player, a portable television, and a portable navigation system. In addition, the present disclosure relates to a position control method which can be applied to such a portable device. 
     BACKGROUND 
     A portable telephone having a display located on a front surface side of a housing has conventionally been known. In such a portable telephone, a substantially rectangular display slightly smaller in size than the housing is located, for example, on the front surface side of the housing having a substantially rectangular contour. 
     An object of the present disclosure is to suppress breakage of a portable device resulting from drop onto the ground. 
     SUMMARY 
     A first embodiment relates to a portable device. The portable device according to the first embodiment includes a housing, a display located on a front surface side of the housing, and a position change unit located in the housing and configured to change a position of the portable device which is falling. The position change unit includes a movable unit and a drive unit configured to drive the movable unit so as to carry out reciprocating motion in a direction in parallel to a front surface of the housing. A portable telephone includes at least one processor configured to control the drive unit. With reciprocating motion of the movable unit in which an acceleration in movement in one direction is higher than an acceleration in movement in the other direction, a moment which rotates the portable device in a first direction of rotation is generated around an axis in parallel to the front surface of the housing and perpendicular to a direction of the reciprocating motion. 
     Effects and significance of the present disclosure will become more apparent from the following description of an embodiment shown below. An embodiment below, however, is merely by way of example and the present disclosure is not restricted to the description of an embodiment below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a front view showing a configuration of a portable telephone according to an embodiment. 
         FIG. 1B  is a rear view showing the configuration of the portable telephone according to an embodiment. 
         FIG. 1C  is a right side view showing the configuration of the portable telephone according to an embodiment. 
         FIG. 2A  is a front view showing a configuration of a vibrator according to an embodiment. 
         FIGS. 2B and 2C  are diagrams showing reciprocating motion of a movable weight. 
         FIG. 3  is a block diagram showing an overall configuration of the portable telephone according to an embodiment. 
         FIGS. 4A and 4B  are diagrams for illustrating control of drive of the vibrator for rotating the portable telephone according to an embodiment. 
         FIG. 5  is a flowchart showing position control processing according to an embodiment. 
         FIG. 6A  is a diagram showing drop of the portable telephone when the portable telephone takes a position with a front surface of a cabinet facing upward at the time of start of drop, according to an embodiment. 
         FIG. 6B  is a diagram showing drop of the portable telephone when the portable telephone takes a position with the front surface of the cabinet facing downward at the time of start of drop. 
         FIG. 7A  is a flowchart showing position control processing according to a first modification. 
         FIG. 7B  is a diagram showing drop of the portable telephone when a position of the portable telephone is controlled such that a side surface of the cabinet will hit the ground in the first modification. 
         FIG. 8A  is a front view showing a configuration of the portable telephone according to a second modification. 
         FIG. 8B  is a rear view showing the configuration of the portable telephone according to the second modification. 
         FIG. 8C  is a right side view showing the configuration of the portable telephone according to the second modification. 
         FIG. 9A  is a flowchart showing position control processing according to the second modification. 
         FIG. 9B  is a diagram showing that a display is broken by a foreign matter on the ground when the portable telephone has fallen in a position with the front surface of the cabinet facing downward and extending horizontally, according to the second modification. 
         FIG. 9C  is a diagram showing that direct hitting of the front surface of the cabinet against the foreign matter is avoided even though the foreign matter is present at a point of drop of the portable telephone. 
         FIG. 10A  is a diagram showing that the vibrator is located in the cabinet such that the movable weight carries out reciprocating motion in an up-down direction of the cabinet, according to another modification. 
         FIG. 10B  is a diagram showing locations of one vibrator and another vibrator according to another modification. 
         FIG. 11A  is a front perspective view showing a configuration of a vibrator according to another modification. 
         FIG. 11B  is a front view of a portable telephone  1  having a vibrator located. 
         FIG. 12A  is a front perspective view showing a configuration of a vibrator according to another modification. 
         FIG. 12B  is a side perspective view showing a configuration of the vibrator according to another modification. 
         FIG. 12C  is a front view of a portable telephone having a vibrator located. 
         FIG. 13A  is a diagram showing rotation of the movable weight according to another modification. 
         FIG. 13B  is a diagram showing reciprocating motion of the movable weight. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment will be described below with reference to the drawings. 
     In general, a portable telephone suffers from the following problems. A user may inadvertently drop on the ground, a portable telephone which he/she has been holding in his/her hand. The portable telephone structurally has a portion resistant to shock and a portion not resistant to shock. For example, a front surface of a housing where a display is located is not resistant to shock. When the front surface of the housing collides against the ground, the display tends to be broken. Upper, lower, left, and right side surfaces or corner portions of the housing are relatively resistant to shock, and when such a site collides against the ground, the portable telephone is relatively less likely to be broken. 
     An object of an embodiment below is to suppress breakage of a portable device resulting from such drop onto the ground. 
     &lt;Configuration of Portable Telephone&gt; 
       FIGS. 1A, 1B, and 1C  are a front view, a rear view, and a right side view showing a configuration of a portable telephone  1 , respectively. For the sake of convenience of description, as shown in  FIGS. 1A to 1C , a longitudinal direction of a cabinet  2  is defined as an up-down direction and a direction of a short side of cabinet  2  is defined as a left-right direction. A direction perpendicular to the up-down direction and the left-right direction is defined as a front-rear direction. 
     As shown in  FIGS. 1A to 1C , portable telephone  1  includes cabinet  2 , a display  3 , a touch panel  4 , a microphone  5 , an ear speaker  6 , an external speaker  7 , a camera  8 , and a vibrator  9 . 
     Cabinet  2  can be formed of a resin material and can have a substantially rectangular contour when viewed from the front. Display  3  can be located on a front surface side of cabinet  2 . Display  3  can display various images (screens). Display  3  is implemented, for example, by a liquid crystal display. Display  3  may be implemented by other types of display such as an organic EL display. Touch panel  4  can be located to cover display  3 . Touch panel  4  can be formed like a transparent sheet. Various types of touch panel such as a capacitance type, an ultrasonic type, a pressure sensitive type, a resistance film type, and an optical sensing type can be employed as touch panel  4 . The front surface of cabinet  2  can be covered with a transparent cover  2   a  composed of glass. 
     In cabinet  2 , microphone  5  can be located at a lower end portion. In cabinet  2 , ear speaker  6  can be located at an upper end portion. Microphone  5  can accept voice and sound which has passed through a microphone hole  5   a  formed in a front surface of cabinet  2 . Microphone  5  can generate an electric signal in accordance with input sound. Ear speaker  6  can output sound. Output sound can be emitted out of cabinet  2  through an output hole  6   a  formed in the front surface of cabinet  2 . During a telephone call, voice and sound received from a device of a communication counterpart (such as a portable telephone) can be output from ear speaker  6  and voice uttered by a user can be input to microphone  5 . Sound includes various types of sound such as voice and notification sound. 
     In cabinet  2 , external speaker  7  can be located. In a rear surface of cabinet  2 , an output hole  7   a  can be formed in a region facing external speaker  7 . Sound output from external speaker  7  can be emitted out of cabinet  2  through output hole  7   a.    
     In an upper portion of cabinet  2 , camera  8  can be located on a rear surface side. Camera  8  includes an image pick-up element such as a CCD or a CMOS sensor and can shoot a subject. 
     In cabinet  2 , vibrator  9  can be located. Vibrator  9  can be located at a position in the vicinity of a center of gravity G of portable telephone  1 . As shown in  FIGS. 1A and 1B , vibrator  9  can be located at a position substantially the same as center of gravity G of portable telephone  1 , in the up-down direction and the left-right direction of cabinet  2 . As shown in  FIG. 1C , vibrator  9  can be located at a position slightly in the rear of center of gravity G of portable telephone  1  in the front-rear direction of cabinet  2 . 
       FIGS. 2A to 2C  are diagrams for illustrating vibrator  9 .  FIG. 2A  is a front perspective view showing a configuration of vibrator  9 .  FIGS. 2B and 2C  are diagrams showing reciprocating motion of a movable weight  120 . 
     Vibrator  9  can be what is called a linear vibrator (a linear oscillatory actuator). Vibrator  9  includes a case  110 , movable weight  120 , and a drive element  130 . Case  110  can accommodate movable weight  120  and drive element  130 . 
     Movable weight  120  includes a weight main body  121  made of a material relatively great in specific gravity, such as iron or lead, and a magnet  122  attached to weight main body  121 . Magnet  122  has an N-magnetized region facing drive element  130 . Movable weight  120  can be held to be movable in the left-right direction by means of a guide (not shown) located in case  110 . 
     Drive element  130  can be located in case  110  such that a longitudinal direction thereof extends in the left-right direction. Drive element  130  can include a yoke  131  in a rod shape and a coil  132  wound around yoke  131 . 
     As shown in  FIG. 2A , when a current is fed to coil  132  such that the N pole is formed at the left end of drive element  130  and the S pole is formed at the right end thereof as shown in  FIG. 2B  while movable weight  120  is located at a left end in case  110 , movable weight  120  can move to the right and reach the right end in case  110  owing to repulsive force generated on the N pole side and attractive force generated on the S pole side. When a current is fed to coil  132  such that the S pole is formed at the left end of drive element  130  and the N pole is formed at the right end as shown in  FIG. 2C  after movable weight  120  is located at the right end in case  110 , movable weight  120  can move to the left and reach the left end in case  110  owing to repulsive force generated on the N pole side and attractive force generated on the S pole side. As a direction of a current fed to coil  132  is periodically switched, movable weight  120  can carry out reciprocating motion in the left-right direction. As a current fed to coil  132  is higher, repulsive force and attractive force applied by drive element  130  are stronger and hence an acceleration in movement of movable weight  120  can be higher. 
     As shown in  FIG. 1A , vibrator  9  can be located in cabinet  2  such that movable weight  120  carries out reciprocating motion in the left-right direction of cabinet  2  (portable telephone  1 ). 
       FIG. 3  is a block diagram showing an overall configuration of portable telephone  1 . 
     As shown in  FIG. 3 , portable telephone  1  includes a control unit  11 , a storage unit  12 , an image output unit  13 , a touch detector  14 , an audio input unit  15 , an audio output unit  16 , an audio processing unit  17 , a key input unit  18 , a communication unit  19 , a shooting unit  20 , an acceleration detector  21 , and a vibration generator  22 . 
     Storage unit  12  includes a ROM, a RAM, and an external memory. Storage unit  12  stores various programs. A program stored in storage unit  12  includes not only a control program for controlling each unit of portable telephone  1  but also various application programs (hereinafter simply referred to as an “application”) such as applications for telephone calls, messages, a web browser, maps, games, and schedule management. The program stored in storage unit  12  further includes a program for performing position control processing which will be described later. The program is stored in storage unit  12  at the time of manufacturing of portable telephone  1  by a manufacturer and stored in storage unit  12  through a communication network or through a storage medium such as a memory card or a CD-ROM. 
     Storage unit  12  includes also a work area which stores data temporarily used or generated during execution of a program. 
     Control unit  11  includes a central processing unit (CPU). Control unit  11  can control each unit (storage unit  12 , image output unit  13 , touch detector  14 , audio input unit  15 , audio output unit  16 , audio processing unit  17 , key input unit  18 , communication unit  19 , shooting unit  20 , acceleration detector  21 , and vibration generator  22 ) implementing portable telephone  1 , in accordance with a program stored in storage unit  12 . 
     Image output unit  13  includes display  3  shown in  FIG. 1A . Image output unit  13  can display an image (a screen) on display  3  based on a control signal and an image signal from control unit  11 . Image output unit  13  can have display  3  turned on and off and have brightness of display  3  adjusted in response to a control signal from control unit  11 . 
     Touch detector  14  includes touch panel  4  shown in  FIG. 1A  and can detect a touch operation onto touch panel  4 . More specifically, touch detector  14  can detect a position of contact (hereinafter referred to as a “touch position”) onto touch panel  4  by a contact object such as a user&#39;s finger. Touch detector  14  can output a position signal generated based on a detected touch position to control unit  11 . A touch operation onto touch panel  4  is performed onto a screen or an object displayed on display  3  and can also be referred to as a touch operation onto display  3 . 
     Touch detector  14  may be configured to detect as a touch position, a position to which a user&#39;s finger is proximate when the finger is proximate to touch panel  4 . For example, when touch panel  4  of touch detector  14  is of a capacitance type, sensitivity thereof can be adjusted such that variation in capacitance exceeds a detection threshold value at the time when a finger is proximate to touch panel  4 . 
     When the front surface of cabinet  2  is covered with cover  2   a  as in this embodiment, a finger does not come in direct contact with touch panel  4  but the finger is in indirect contact with touch panel  4  with cover  2   a  being interposed. Touch panel  4  can detect a touch position when a finger is in contact with cover  2   a  or is proximate to cover  2   a.    
     With touch panel  4  being located, a user can perform various touch operations onto display  3  by touching touch panel  4  (cover  2   a ) with his/her finger or by bringing his/her finger in proximity to touch panel  4  (cover  2   a ). The touch operation includes, for example, a tap operation, a flick operation, and a slide operation. The tap operation refers to an operation to bring a user&#39;s finger in contact with or in proximity to touch panel  4  and thereafter move his/her finger away from touch panel  4  in a short period of time. The flick operation refers to an operation to bring a user&#39;s finger in contact with or in proximity to touch panel  4  and thereafter flip or sweep touch panel  4  with his/her finger in any direction. The slide operation refers to an operation to move a user&#39;s finger in any direction while a user keeps his/her finger in contact with or in proximity to touch panel  4 . 
     For example, when touch detector  14  detects a touch position and then the touch position is no longer detected within a first predetermined period of time since detection of the touch position, control unit  11  can determine such a touch operation as the tap operation. When a touch position has moved by a first predetermined distance or more within a second predetermined period of time since detection of the touch position and the touch position is no longer detected, control unit  11  can determine such a touch operation as the flick operation. When a touch position has moved by a second predetermined distance or more after detection of the touch position, control unit  11  can determine such a touch operation as the slide operation. 
     Audio input unit  15  includes microphone  5 . Audio input unit  15  can output an electric signal from microphone  5  to audio processing unit  17 . 
     Audio output unit  16  includes ear speaker  6  and external speaker  7 . Audio output unit  16  can receive input of an electric signal from audio processing unit  17 . Audio output unit  16  can have ear speaker  6  or external speaker  7  output sound. 
     Audio processing unit  17  can subject an electric signal from audio input unit  15  to A/D conversion and can output a resultant digital audio signal to control unit  11 . Audio processing unit  17  can subject a digital audio signal from control unit  11  to decoding processing and D/A conversion, and can output the resultant electric signal to audio output unit  16 . 
     Key input unit  18  can include at least one hard key. For example, key input unit  18  can include a power key for turning on power of portable telephone  1 . Key input unit  18  can output a signal corresponding to a pressed hard key to control unit  11 . 
     Communication unit  19  includes a circuit for converting a signal for a telephone call or communication and an antenna which transmits and receives radio waves. Communication unit  19  can convert a signal for a telephone call or communication input from control unit  11  into a radio signal and transmit the resultant radio signal to a communication destination such as a base station or other communication devices through the antenna. Furthermore, communication unit  19  can convert a radio signal received through the antenna into a signal in a format which can be used by control unit  11  and output the resultant signal to control unit  11 . 
     Shooting unit  20  includes camera  8  shown in  FIG. 1B . Shooting unit  20  can perform various types of image processing on data of images shot by camera  8  and output resultant image data to control unit  11 . 
     Acceleration detector  21  can include a three-axis acceleration sensor. The three-axis acceleration sensor can detect an acceleration generated in three directions of the front-rear direction, the up-down direction, and the left-right direction of portable telephone  1 . Acceleration detector  21  can output an acceleration signal in accordance with an acceleration detected by the three-axis acceleration sensor to control unit  11 . The three-axis acceleration sensor can be located in cabinet  2  such that an acceleration applied in the front direction (a direction of the front surface), the right direction, and the upward direction is expressed with a positive value and an acceleration applied in the rear direction (a direction of the rear surface), the left direction, and the downward direction is expressed with a negative value. 
     Vibration generator  22  can include vibrator  9  shown in  FIG. 1A  and a supply circuit supplying a current to drive element  130  of vibrator  9 . The supply circuit can supply a current to drive element  130  in response to a control signal from control unit  11 . 
     &lt;Control of Position of Portable Telephone&gt; 
     A user may inadvertently drop portable telephone  1  which he/she has been holding with his/her hand onto the ground. Portable telephone  1  structurally has a portion resistant to shock and a portion not resistant to shock. For example, the front surface of cabinet  2  having display  3  located is not resistant to shock. When the front surface of cabinet  2  collides against the ground, display  3  tends to be broken. 
     In portable telephone  1  in an embodiment, vibrator  9  can be used to control a position of portable telephone  1  while it falls, and position control processing for suppressing breakage of portable telephone  1  can be performed by control unit  11 . 
     Control unit  11  can include a drop determination unit  31 , a position determination unit  32 , and a position control unit  33 . Drop determination unit  31 , position determination unit  32 , and position control unit  33  are implemented as a function of a program executed by control unit  11 . 
     Drop determination unit  31  can determine whether or not portable telephone  1  has fallen, based on an acceleration applied to portable telephone  1 . A drop threshold value for determining drop is set in advance based on an acceleration actually applied at the time when portable telephone  1  falls, and stored in storage unit  12 . Drop determination unit  31  can determine that portable telephone  1  has fallen when a value for an acceleration applied to portable telephone  1 , that is, an absolute value of an acceleration vector which is a result of synthesis of acceleration vectors in three directions of the front-rear, left-right, and up-down directions detected by the three-axis acceleration sensor of acceleration detector  21 , exceeds the drop threshold value. 
     Position determination unit  32  can determine a position of portable telephone  1  while it falls. An acceleration applied during drop is distributed in acceleration components in three directions of the front-rear, left-right, and up-down directions in accordance with a position of portable telephone  1  while it falls. Position determination unit  32  can determine a position of portable telephone  1  based on a ratio among accelerations in the front-rear, left-right, and up-down directions detected by the three-axis acceleration sensor while the portable telephone falls. 
     Position control unit  33  can control drive element  130  of vibrator  9  to rotate portable telephone  1  such that portable telephone  1  takes a prescribed position for suppressing breakage of display  3  while the portable telephone falls. 
       FIGS. 4A and 4B  are diagrams for illustrating control for driving vibrator  9  for rotating portable telephone  1 . 
     As shown in  FIG. 4A , position control unit  33  can control drive element  130  such that an acceleration of movable weight  120  in movement in one direction is higher than an acceleration of movable weight  120  in movement in the other direction. When movable weight  120  carries out reciprocating motion high in acceleration in one direction and low in acceleration in the other direction, inertia force F in one direction is generated in portable telephone  1  as shown in  FIG. 4B . Since vibrator  9  is located at a position displaced from center of gravity G in the front-rear direction of portable telephone  1 , a deviation S is caused between a position where inertia force F is applied and the position of center of gravity G in the front-rear direction of portable telephone  1 . A moment M (rotational force) around center of gravity G is thus generated in portable telephone  1 . As moment M is applied, portable telephone  1  rotates around an axis of rotation R 1  in the up-down direction which passes through center of gravity G shown in  FIG. 1A . When position control unit  33  controls drive element  130  such that an acceleration of movable weight  120  in movement in the other direction is higher than an acceleration of movable weight  120  in movement in one direction, moment M in a direction reverse to the direction shown in  FIG. 4B  is generated and portable telephone  1  rotates in the reverse direction. 
       FIG. 5  is a flowchart showing position control processing.  FIG. 6A  is a diagram showing drop of portable telephone  1  when portable telephone  1  takes a position with the front surface of cabinet  2  facing upward at the time of start of drop.  FIG. 6B  is a diagram showing drop of portable telephone  1  when portable telephone  1  takes a position with the front surface of cabinet  2  facing downward at the time of start of drop. 
     Position control processing can repeatedly be performed while portable telephone  1  operates. In an embodiment, as a result of the position control processing in  FIG. 5 , when portable telephone  1  takes a position with the front surface of cabinet  2  facing downward while it falls, portable telephone  1  can be rotated such that the position of portable telephone  1  is changed to a position with the front surface of cabinet  2  facing upward. 
     If a user inadvertently drops portable telephone  1 , control unit  11  (drop determination unit  31 ) can determine that portable telephone  1  has fallen (S 101 : YES). Control unit  11  (position determination unit  32 ) can determine whether or not portable telephone  1  takes a position with the front surface of cabinet  2  facing downward (S 102 ). When portable telephone  1  takes a position with the front surface of cabinet  2  facing downward, an acceleration in the front-rear direction detected by acceleration detector  21  exhibits a positive value. When portable telephone  1  takes a position with the front surface of cabinet  2  facing upward, an acceleration in the front-rear direction exhibits a negative value. 
     When the front surface of cabinet  2  faces downward, the front surface of cabinet  2  will hit the ground. Display  3 , touch panel  4 , and cover  2   a  located on the front surface side of cabinet  2  are not resistant to shock and are likely to break. When the front surface of cabinet  2  faces upward, the rear surface of cabinet  2  will hit the ground. Since cabinet  2  is formed of a resin material and there is no display  3  on the rear surface side, the rear surface itself or display  3  is less likely to break. 
     When portable telephone  1  takes a position with the front surface of cabinet  2  facing upward (S 102 : NO), control unit  11  can quit the position control processing. As shown in  FIG. 6A , portable telephone  1  hits the ground from the rear surface side of cabinet  2  as it is without change in position. The position control processing which has once ended is immediately resumed. 
     When portable telephone  1  takes a position with the front surface of cabinet  2  facing downward (S 102 : YES), control unit  11  can determine to which of left and right an amount of rotation (an angle of rotation) of portable telephone  1  is smaller at the time when portable telephone  1  is changed in position such that the front surface of cabinet  2  faces upward (S 103 ). For example, with portable telephone  1  taking a position inclined to the right as in  FIG. 6B , an amount of rotation will be smaller when portable telephone  1  is rotated clockwise. With portable telephone  1  taking a position inclined to the left, an amount of rotation will be smaller when portable telephone  1  is rotated counterclockwise. 
     When a direction of rotation smaller in amount of rotation is right (S 103 : right), control unit  11  (position control unit  33 ) can drive vibrator  9  such that clockwise moment M is generated (S 104 ). Thus, portable telephone  1  rotates clockwise around axis of rotation R 1 . When a direction of rotation smaller in amount of rotation is left (S 103 : left); control unit  11  (position control unit  33 ) can drive vibrator  9  such that counterclockwise moment M is generated (S 105 ). Thus, portable telephone  1  rotates counterclockwise around axis of rotation R 1 . When an amount of rotation is the same between a clockwise direction and a counterclockwise direction, control unit  11  (position control unit  33 ) can drive vibrator  9  such that moment M in a predetermined direction of rotation (for example, clockwise) is generated. 
     Control unit  11  (position determination unit  32 ) can determine whether or not portable telephone  1  is in a position with the front surface of cabinet  2  facing upward (S 106 ). When portable telephone  1  is in the position with the front surface of cabinet  2  facing upward (S 106 : YES), control unit  11  (position control unit  33 ) can turn off vibrator  9  (S 107 ). The position control processing once ends and can subsequently be resumed. 
     As shown in  FIG. 6B , when portable telephone  1  takes a position with the front surface of cabinet  2  facing downward at the time of start of drop, portable telephone  1  can rotate and can change the position such that the front surface of cabinet  2  faces upward. Portable telephone  1  will hit the ground from the rear surface side of cabinet  2 . 
     In consideration of strength of display  3 , touch panel  4 , and cover  2   a , a lower limit height (for example, 1 m) from the ground at which portable telephone  1  may be broken when it falls on the ground is grasped through experiments. Portable telephone  1  requires such a speed of rotation as allowing rotation of portable telephone  1  to a position with the front surface of cabinet  2  facing upward within a time period of drop until portable telephone  1  hits the ground from the lower limit height under a condition requiring the greatest amount of rotation. Performance of vibrator  9  such as a weight and a movable stroke of movable weight  120  and driving force of drive element  130  is determined such that moment M allowing obtainment of such a speed of rotation is generated. 
     Portable telephone  1  in an embodiment has a normal mode in which a user is notified of incoming of a telephone call or a mail by notification sound and a manner mode in which a user is notified of an incoming call by vibration. When an incoming call is received while the manner mode has been set, control unit  11  can drive drive element  130  so as to vibrate vibrator  9  such that movable weight  120  carries out reciprocating motion at the same acceleration in both of movement in one direction (a right direction) and movement in the other direction (a left direction). 
     &lt;Function and Effect&gt; 
     According to an embodiment above, a position of portable telephone  1  can be changed such that a position allowing suppression of breakage of display  3 , specifically, a position with the front surface of cabinet  2  facing upward, is taken while portable telephone  1  falls. Breakage of portable telephone  1  resulting from drop onto the ground can be suppressed. 
     Furthermore, according to an embodiment, portable telephone  1  can rotate in a direction of rotation in which an amount of rotation for change to a position with the front surface of cabinet  2  facing upward is smaller. A speed of rotation required for completion of change in position during drop can thus be suppressed and required performance of vibrator  9  can be suppressed. 
     In addition, according to an embodiment, vibrator  9  can also function as notification means for notification by vibration. 
     Though an embodiment has been described above, the present disclosure is not restricted by such an embodiment and an embodiment is also susceptible to various modifications other than the above. 
     &lt;First Modification&gt; 
       FIGS. 7A and 7B  are diagrams for illustrating control of a position of portable telephone  1  while it falls according to a first modification.  FIG. 7A  is a flowchart showing position control processing.  FIG. 7B  is a diagram showing drop of portable telephone  1  when a position of portable telephone  1  is controlled such that a side surface of cabinet  2  will hit the ground. 
     The upper, lower, left, and right side surfaces of portable telephone  1  are normally higher in strength than the front surface and the rear surface of cabinet  2 . In the present modification, while portable telephone  1  falls, portable telephone  1  can be rotated such that a position thereof is changed to such a position that a side surface of cabinet  2  will hit the ground, as a result of position control processing in  FIG. 7A . 
     Referring to  FIG. 7A , when portable telephone  1  falls (S 201 : YES), control unit  11  (position determination unit  32 ) can determine whether or not portable telephone  1  takes such a position that any of upper, lower, left, and right side surfaces of cabinet  2  will hit the ground (S 202 ). When any side surface of cabinet  2  is in a horizontal state in the left-right direction or when an inclination of any side surface from the horizontal state is within a small angle (for example, an angle approximately from 5° to 10°), position determination unit  32  can determine that portable telephone  1  takes such a position that any side surface of cabinet  2  will hit the ground. When a side surface of cabinet  2  is in the horizontal state or an inclination of any side surface from the horizontal state is within a small angle, an acceleration in the front-rear direction detected by acceleration detector  21  exhibits zero or a value close to zero. 
     When portable telephone  1  does not take such a position that any side surface of cabinet  2  will hit the ground (S 202 : NO), control unit  11  can determine to which of left and right an amount of rotation of portable telephone  1  is smaller when a position of portable telephone  1  is changed such that a side surface thereof will hit the ground (S 203 ). 
     When a direction of rotation smaller in amount of rotation is right (S 203 : right), control unit  11  (position control unit  33 ) can drive vibrator  9  such that clockwise moment M is generated (S 204 ). Thus, portable telephone  1  can rotate clockwise around axis of rotation R 1 . When a direction of rotation smaller in amount of rotation is left (S 203 : left), control unit  11  (position control unit  33 ) can drive vibrator  9  such that counterclockwise moment M is generated (S 205 ). Thus, portable telephone  1  can rotate counterclockwise around axis of rotation R 1 . 
     Control unit  11  (position determination unit  32 ) can determine whether or not portable telephone  1  has taken such a position that any side surface of cabinet  2  will hit the ground (S 206 ). When portable telephone  1  takes such a position that any side surface of cabinet  2  will hit the ground (S 206 : YES), control unit  11  (position control unit  33 ) can turn off vibrator  9  (S 207 ). 
     As shown in  FIG. 7B , when portable telephone  1  does not take such a position that a side surface of cabinet  2  will hit the ground at the time of start of drop, portable telephone  1  is rotated while it falls and a position of portable telephone  1  is changed such that the portable telephone takes such a position that a side surface of cabinet  2  will hit the ground. Portable telephone  1  hits the ground from a side surface of cabinet  2 . 
     When a side surface of cabinet  2  is in the horizontal state in the left-right direction and when cabinet  2  is in the horizontal state also in the up-down direction, the entire side surface will hit the ground. When cabinet  2  is inclined in the up-down direction, however, a part of a side surface rather than the entire side surface will hit the ground. Such a position that a part of a side surface of cabinet  2  will hit the ground is also included in a position that a side surface of cabinet  2  will hit the ground. 
     Portable telephone  1  requires such a speed of rotation as allowing rotation of portable telephone  1  to such a position that a side surface of cabinet  2  will hit the ground within a time period of drop until portable telephone  1  falls onto the ground from the lower limit height under a condition requiring the greatest amount of rotation. Performance of vibrator  9  such as a weight and a movable stroke of movable weight  120  and driving force of drive element  130  is determined such that moment M allowing obtainment of such a speed of rotation is generated. 
     According to the configuration in the first modification, a function and effect the same as in an embodiment above can be achieved. 
     &lt;Second Modification&gt; 
       FIGS. 8A, 8B, and 8C  are a front view, a rear view, and a right side view showing a configuration of portable telephone  1  according to a second modification, respectively. 
     Portable telephone  1  according to the second modification includes a protection case  50  accommodating cabinet  2 . Protection case  50  covers the rear surface and the upper, lower, left, and right side surfaces of portable telephone  1  by accommodating portable telephone  1  in an accommodation portion  50   a . Protection case  50  is formed of an elastic material such as rubber or a reinforced resin material such as FRP. A depth dimension D 1  of accommodation portion  50   a  of protection case  50  is greater than a dimension D 2  from the front to the rear of cabinet  2 , and a front edge of protection case  50   a  protrudes forward from the front surface of cabinet  2  while cabinet  2  is accommodated in protection case  50 . In the rear surface of protection case  50 , a first opening portion  51  and a second opening portion  52  can be formed at a position facing camera  8  and a position facing external speaker  7 , respectively. 
       FIGS. 9A to 9C  are diagrams for illustrating control of a position of portable telephone  1  while it falls according to the second modification.  FIG. 9A  is a flowchart showing position control processing.  FIG. 9B  is a diagram showing that display  3  is broken by a foreign matter on the ground when portable telephone  1  has fallen in a position with the front surface of cabinet  2  facing downward and extending horizontally.  FIG. 9B  is a diagram showing that breakage of display  3  by the foreign matter on the ground is avoided by position control processing in  FIG. 9A  when portable telephone  1  falls in a position with the front surface of cabinet  2  facing downward and extending horizontally. 
     In portable telephone  1  in the second modification, since the rear surface and the upper, lower, left, and right side surfaces are protected by protection case  50 , breakage of portable telephone  1  is prevented even though portable telephone  1  falls and hits the ground from such a surface. Even though portable telephone  1  falls on the ground with the front surface of cabinet  2  facing downward and extending horizontally, the front edge of protection case  50  normally hits the ground before the front surface of cabinet  2 , and hence breakage of display  3  is prevented. When a hard foreign matter is present on the ground as in  FIG. 9B , however, the front surface of cabinet  2  may hit the foreign matter and display  3  may be broken before the front edge of protection case  50  hits the ground. 
     In the second modification, when portable telephone  1  takes a position with the front surface of cabinet  2  facing downward and extending horizontally (in the horizontal state and in a state close to horizontal) while it falls, portable telephone  1  can be rotated such that it takes a position deviating from that position, that is, a position with the front surface of cabinet  2  being inclined with respect to a horizontal plane by a prescribed angle, as a result of position control processing in  FIG. 9A . 
     Referring to  FIG. 9A , when portable telephone  1  falls (S 301 : YES), control unit  11  (position determination unit  32 ) can determine whether or not portable telephone  1  takes a position with the front surface of cabinet  2  facing downward and extending substantially horizontally (S 302 ). In the second modification, determination as to whether or not the front surface of cabinet  2  extends substantially horizontally can be made by determining whether or not the front surface of cabinet  2  is inclined with respect to the horizontal plane by a prescribed angle (for example, 10°) or smaller in the left-right direction and the up-down direction. 
     When portable telephone  1  takes a position with the front surface of cabinet  2  facing downward and extending substantially horizontally (S 302 : YES), control unit  11  can determine to which of left and right an amount of rotation of portable telephone  1  is smaller when a position is changed such that the front surface of cabinet  2  is inclined by a prescribed angle with respect to the horizontal plane (S 303 ). 
     When a direction of rotation smaller in amount of rotation is right (S 303 : right), control unit  11  (position control unit  33 ) can drive vibrator  9  such that clockwise moment M is generated (S 304 ). Thus, portable telephone  1  can rotate clockwise around axis of rotation R 1 . When a direction of rotation smaller in amount of rotation is left (S 303 : left), control unit  11  (position control unit  33 ) can drive vibrator  9  such that counterclockwise moment M is generated (S 305 ). Thus, portable telephone  1  can rotate counterclockwise around axis of rotation R 1 . 
     Control unit  11  (position determination unit  32 ) can determine whether or not the front surface of cabinet  2  has been inclined with respect to the horizontal plane by a prescribed angle (for example, an angle approximately from 10° to 15°) in the left-right direction (S 306 ). 
     When the front surface of cabinet  2  is inclined with respect to the horizontal plane by a prescribed angle in the left-right direction (S 306 : YES), control unit  11  (position control unit  33 ) can turn off vibrator  9  (S 307 ). 
     Thus, in the second modification, when such a position is taken that front surface of cabinet  2  faces downward and extends substantially horizontally at the time of start of drop, portable telephone  1  rotates while it falls and the front surface of cabinet  2  is inclined with respect to the horizontal plane such that the front surface of cabinet  2  no longer extends substantially horizontally. Thus, as shown in  FIG. 9C , even when a foreign matter is present at a point of drop of portable telephone  1 , direct hitting of the front surface of cabinet  2  against the foreign matter can be avoided. According to the second modification, breakage of portable telephone  1  resulting from drop onto the ground can be suppressed. 
     Portable telephone  1  requires such a speed of rotation as allowing rotation of portable telephone  1  until the front surface of cabinet  2  is inclined by a prescribed angle with respect to the horizontal plane within a time period of drop until portable telephone  1  falls onto the ground from the lower limit height under a condition requiring the greatest amount of rotation. Performance of vibrator  9  such as a weight and a movable stroke of movable weight  120  and driving force of drive element  130  is determined such that moment M allowing obtainment of such a speed of rotation is generated. In the second modification, cabinet  2  should only be inclined to such an extent as allowing avoidance of a foreign matter, and an amount of rotation of portable telephone  1  while it falls can be small. Therefore, performance of vibrator  9  can be kept lower than in an embodiment above and the first modification. 
     &lt;Other Modifications&gt; 
     Though vibrator  9  is located in the vicinity of center of gravity G of portable telephone  1  in an embodiment above, the first modification, and the second modification, it may be located at other positions. 
     In an embodiment above, the first modification, and the second modification, vibrator  9  is located in cabinet  2  such that movable weight  120  carries out reciprocating motion in the left-right direction of cabinet  2 . As shown in  FIG. 10A , however, vibrator  9  may be located in cabinet  2  such that movable weight  120  carries out reciprocating motion in the up-down direction of cabinet  2 . In this case, portable telephone  1  rotates around an axis of rotation R 2  extending in the left-right direction which passes through center of gravity G. 
     In an embodiment above, the first modification, and the second modification, a single vibrator  9  is located in cabinet  2 , however, a plurality of vibrators  9  may be located. For example, vibrators  9  may be located in the same orientations in respective corner portions of cabinet  2 . 
     As shown in  FIG. 10B , in cabinet  2 , one vibrator  9  may be located such that movable weight  120  carries out reciprocating motion in the left-right direction of cabinet  2  and another vibrator  9  may be located such that movable weight  120  carries out reciprocating motion in the up-down direction of cabinet  2 . As portable telephone  1  can thus be rotated in four directions of the up, down, left, and right directions, a position of portable telephone  1  can finely be controlled such that a more limited site such as a specific side surface or a specific corner portion will hit the ground. Movable weight  120  and drive element  130  of one vibrator  9  correspond to the first movable unit and the first drive unit, respectively, and movable weight  120  and drive element  130  of another vibrator  9  correspond to the second movable unit and the second drive unit, respectively. 
     Instead of the two vibrators shown in  FIG. 10B , a vibrator  9 A shown in  FIG. 11A  or a vibrator  9 B shown in  FIGS. 12A and 12B  may be employed. 
       FIG. 11A  is a front perspective view showing a configuration of vibrator  9 A.  FIG. 11B  is a front view of portable telephone  1  having vibrator  9 A located. An instance including vibrator  9 A will be described with reference to  FIGS. 11A and 11B . 
     Vibrator  9 A includes a case  110   a , a movable weight  120   a , a first drive element  130   a , and a second drive element  130   b . Case  110   a  accommodates movable weight  120   a , first drive element  130   a , and second drive element  130   b.    
     Movable weight  120  includes a weight main body  121   a  made of a material relatively large in specific gravity, such as iron or lead, and a first magnet  122   a  and a second magnet  122   b  attached to weight main body  121   a . First magnet  122   a  can have an N-magnetized region facing first drive element  130   a  and second magnet  122   b  can have an N-magnetized region facing second drive element  130   b . Movable weight  120   a  is held to be movable in the left-right direction and the up-down direction by means of a guide (not shown) located in case  110   a.    
     First drive element  130   a  can be located in case  110  such that the longitudinal direction thereof extends in the left-right direction. Second drive element  130   b  can be located in case  110  such that the longitudinal direction thereof extends in the up-down direction. First drive element  130   a  and second drive element  130   b  are the same in configuration as drive element  130  of vibrator  9 . 
     When a current is fed to first drive element  130   a  such that polarities of respective end portions of first drive element  130   a  are alternately switched, movable weight  120   a  can carry out reciprocating motion in the left-right direction as shown with a solid arrow in  FIG. 11A . When a current is fed to second drive element  130   b  such that polarities of respective end portions of second drive element  130   b  are alternately switched, movable weight  120   a  can carry out reciprocating motion in the up-down direction as shown with a dashed arrow in  FIG. 11A . 
     As shown in  FIG. 11B , vibrator  9 A can be located in the vicinity of center of gravity G in cabinet  2  such that movable weight  120   a  carries out reciprocating motion in the left-right direction and in the up-down direction of cabinet  2 . Portable telephone  1  can rotate in the left-right direction around axis of rotation R 1 , with moment M generated by reciprocating motion of movable weight  120   a  in the left-right direction, which has a difference in acceleration. Furthermore, portable telephone  1  can rotate in the up-down direction around axis of rotation R 2 , with moment M generated by reciprocating motion of movable weight  120   a  in the up-down direction, which has a difference in acceleration. 
       FIGS. 12A and 12B  are a front perspective view and a side perspective view showing a configuration of vibrator  9 B, respectively.  FIG. 12C  is a front view of portable telephone  1  having vibrator  9 B disposed.  FIG. 13A  is a diagram showing rotation of a movable weight  160  and  FIG. 13B  is a diagram showing reciprocating motion of movable weight  160 . An instance including vibrator  9 B will be described with reference to  FIGS. 12A to 12C  and  FIGS. 13A and 13B . 
     Vibrator  9 B includes a case  150 , movable weight  160 , six first electromagnets  170 , and six second electromagnets  180 . Case  150  accommodates movable weight  160 , six first electromagnets  170 , and six second electromagnets  180 . 
     Movable weight  160  is implemented by a permanent magnet having a cylindrical shape, and has an N magnetic pole region and an S magnetic pole region formed as being separated in a radial direction. Movable weight  160  can be held to be rotatable and movable in the left-right direction by means of a guide shaft  151  located in case  150 . 
     Six first electromagnets  170  can be located to surround movable weight  160  on the left side in case  150 . Each of first electromagnets  170  includes a core  171  and a coil  172  wound around core  171 . By switching a direction of a current which flows through coil  172 , a polarity of an end portion of core  171  which faces movable weight  160  can be switched. Six second electromagnets  180  can be located to surround movable weight  160  on the right side in case  150 . Each of second electromagnets  180  includes a core  181  and a coil  182  wound around core  181 . By switching a direction of a current which flows through coil  182 , a polarity of an end portion of core  181  which faces movable weight  160  can be switched. 
     As shown in  FIG. 13A , by successively switching a polarity of each of first electromagnets  170  and each of second electromagnets  180  in a circumferential direction, movable weight  160  can carry out rotational motion. As shown in  FIG. 13B , by alternately switching between the N pole and the S pole such that a set of three first electromagnets  170  and a set of three second electromagnets  180  are reverse in polarity to each other, movable weight  160  can carry out reciprocating motion. 
     As shown in  FIG. 12C , vibrator  9 B can be located in the vicinity of center of gravity G in cabinet  2  such that movable weight  160  carries out reciprocating motion in the left-right direction of cabinet  2  and carries out rotational motion in the up-down direction. Portable telephone  1  can rotate in the left-right direction around axis of rotation R 1 , with moment M generated by reciprocating motion of movable weight  160  in the left-right direction, which has a difference in acceleration. Portable telephone  1  can rotate in the up-down direction around guide shaft  151 , with moment M generated by rotational motion of movable weight  160 . 
     A distance sensor may be located in portable telephone  1  in an embodiment above, the first modification, and the second modification. In this case, when control unit  11  determines that portable telephone  1  has fallen, a distance from the ground is measured with the distance sensor. When the distance is smaller than the lower limit height, control unit  11  does not control a position of portable telephone  1  with vibrator  9 . 
     In position control processing in the first modification, when a position is such that a side surface of cabinet  2  will hit the ground, vibrator  9  is turned off so as to stop rotation of portable telephone  1 . Depending on an impetus of rotation of portable telephone  1 , however, a position may go beyond such a position that a side surface of cabinet  2  will hit the ground. In order to address this, such a configuration may be adopted that a position of portable telephone  1  is determined again after vibrator  9  is turned off and control unit  11  rotates portable telephone  1  in a reverse direction if portable telephone  1  has rotated to go beyond such a position that a side surface of cabinet  2  will hit the ground. 
     In an embodiment above, the first modification, and the second modification, when acceleration detector  21  detects an acceleration exceeding a drop threshold value, drop determination unit  31  determines that portable telephone  1  has fallen. Such a configuration may be adopted that a proximity sensor is used to detect whether or not a user holds portable telephone  1 , and so long as portable telephone  1  is held, drop determination unit  31  determines that portable telephone  1  has not fallen in spite of detection of an acceleration exceeding the drop threshold value. Alternatively, such a configuration may be adopted that camera  8  is activated and when an acceleration exceeding the drop threshold value is detected and camera  8  shoots moving images impossible in normal use of portable telephone  1 , drop determination unit  31  determines that portable telephone  1  has fallen. Further alternatively, such a configuration may be adopted that when an acceleration exceeding the drop threshold value is detected and change in position impossible in normal use (for example, rotation of portable telephone  1 ) is detected in portable telephone  1  by acceleration detector  21  or a geomagnetism sensor, drop determination unit  31  determines that portable telephone  1  has fallen. 
     Though an embodiment is applied to a portable telephone of a smartphone type, limitation thereto is not intended, and an embodiment may be applied to a portable telephone of other types such as a straight type, a foldable type, and a slidable type. 
     An embodiment is not limited to a portable telephone, but is applicable to various portable devices such as a personal digital assistant (PDA), a tablet PC, an electronic book terminal, a portable music player, a portable television, and a portable navigation system. 
     In addition, an embodiment is susceptible to various modifications as appropriate within the scope of technical concepts shown in the claims.