Electronic device and method of controlling same

An electronic device includes a main body, a drive mechanism configured to move the main body, a detector having a plurality of sensors mounted in the main body for detecting distances to an object which is present in a space around the main body, a calculator configured to calculate a direction of the object relative to the main body based on the detected distances, and a controller configured to control the drive mechanism to change an orientation of the main body dependent on the calculated direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Japanese Patent Application No. JP 2005-326527 filed on Nov. 10, 2005, the disclosure of which is hereby incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electronic device and a method of controlling an electronic device, and more particularly to an electronic device which is used in a predetermined direction and a method of controlling such an electronic device.

2. Description of the Related Art

Many electronic devices such as audio devices and input devices that have been in widespread use in recent years are premised on use in a predetermined direction. Specifically, an audio device is premised on such use that its speakers have sound radiating surfaces directed toward the user, and an input device is premised on such use that its operating face with operating buttons is directed toward the user.

Stated otherwise, if an electronic device in the past is used in a direction which is not the predetermined direction in which it is supposed to be used, then the user finds it awkward to use the electronic device because, for example, the user cannot hear good stereophonic sounds from the electronic device or is unable to operate the electronic device smoothly. When the electronic device in the past is oriented in the undesirable direction, the user needs to move relatively to the electronic device or to turn the electronic device so that the electronic device will be oriented in the predetermined direction with respect to the user.

If the electronic device can detect the direction in which the user is present and orient itself into the predetermined direction with respect to the user, then the user will find it much easier to use the electronic device.

One electronic device in the past has a sensor for detecting the distance up to the user who is present in a predetermined direction. However, the electronic device in the past is unable to detect the direction in which the user is present as the sensor can detect only the distance up to the user. For details, reference should be made to Japanese patent laid-open No. 2004-130428.

As described above, though some electronic devices in the past are premised on use in a predetermined direction with respect to the user, since they are unable to detect the direction in which the user is present, the user needs to move relatively to the electronic device or to turn the electronic device with respect to the user. Consequently, those electronic devices in the past have been awkward to use.

It is an object of the present invention to provide an electronic device which can be used with more ease than heretofore and a method of controlling such an electronic device.

SUMMARY OF THE INVENTION

To achieve the above object, there is provided in accordance with the present invention an electronic device including a main body, a drive mechanism for moving the main body, a detector having a plurality of sensors mounted in the main body for detecting distances to an object which is present in a space around the main body, a calculator for calculating a direction of the object relative to the main body based on the detected distances, and a controller for controlling the drive mechanism to change an orientation of the main body dependent on the calculated direction.

The direction in which the object, e.g., the user, is present is recognized, and the orientation of the main body is changed into alignment with the recognized direction in which the user is present. The electronic device can thus be used in the direction in which the user is present, i.e., in the direction in which the electronic device is supposed to be used, without the need for the user to move or to change the orientation of the main body.

The electronic device thus arranged is much easier to use than heretofore. According to the present invention, there is also provided a method of controlling the electronic device to allow the electronic robot device to be used much easier than heretofore.

DETAILED DESCRIPTION

(1) Overview of an Electronic Device

First, an electronic device according to an embodiment of the present invention will briefly be described below with reference toFIGS. 1 and 2. As shown inFIGS. 1 and 2, an electronic device1has a main body2, a drive mechanism3for changing the orientation of the main body2, a detector4disposed in the main body2and having a plurality of distance sensors S1, S2and S3for detecting the distance up to an object (not shown) that is present in a space around the main body2, a calculator5for calculating the direction of the object with respect to the electronic device1based on the distance detected by the detector4, and a controller6for controlling the drive mechanism3to change the orientation of the main body2.

In operation, based on the distance detected by the detector4which has the distance sensors S1, S2and S3, the electric device1calculates the direction in which the object, e.g., the user, is present, and changes the orientation of the main body2into alignment with the calculated direction. Therefore, the electronic device1can be used in the orientation depending on the direction in which the user is present, i.e., in the direction in which the electronic device1is supposed to be used, without the need for the user to move with respect to the electronic device1or to change the orientation of the main body2with respect to the user.

Each of the distance sensors S1, S2and S3of the detector4includes a quasi-electrostatic field sensor. The quasi-electrostatic field sensor will be described in detail below.

(2-1) Properties of a Quasi-Electrostatic Field

First, a quasi-electrostatic field which forms a basis for a quasi-electrostatic field sensor will be described below. An electric field is generated as a combination of a radiative electric field which is in inverse proportion to the distance from an electric field source, an inductive electromagnetic field which is in inverse proportion to the square of the distance from the electric field source, and a quasi-electrostatic field which is in inverse proportion to the cube of the distance from the electric field source.

Relative intensities of the radiative electric field, the inductive electromagnetic field, and the quasi-electrostatic field are related to the distance as shown in a graph ofFIG. 3. InFIG. 3, the relationship between the relative intensities of the electric fields at 1 [MHz] and the distance is indicated on a logarithmic scale.

As can be seen fromFIG. 3, there is a distance wherein the relative intensities of the radiative electric field, the inductive electromagnetic field, and the quasi-electrostatic field are equal to each other. Such a distance will hereinafter be referred to as “intensity boundary point”. At distances farther than the intensity boundary point, the radiative electric field is dominant, i.e., it is greater than the inductive electromagnetic field and the quasi-electrostatic field. At distances closer than the intensity boundary point, the quasi-electrostatic field is dominant, i.e., it is greater than the radiative electric field is dominant and the inductive electromagnetic field.

Each of the intensity Eθ, radiationof the radiative electric field, the intensity Eθ, inductionof the inductive electromagnetic field, and the intensity Eθ, quasi-electrostaticof the quasi-electrostatic field at a position that is spaced a distance r [m] from a dipole (electric field source) is expressed by the following equation:

r=1k(1)
In the equation (1), the electric charge on the dipole is represented by q [c], the length of the dipole by 1 [m], the wave number by k [1/m], and the imaginary unit by j.

Since the intensities of the radiative electric field, the inductive electromagnetic field, and the quasi-electrostatic field are equal to each other at the intensity boundary point, the distance r satisfies the following equation:

k=2⁢⁢π⁢⁢fc(2)
The distance r from the electric field source to the intensity boundary point is expressed by:

If the velocity of light in vacuum is indicated by c [m/s] (c=3×108) and the frequency by f [Hz], then the wave number k [1/m] in the equation (3) is expressed by:

E(r)=A(r)r3(4)
Therefore, the intensity boundary point is expressed by the following equation, which is produced by substituting the equation (3) in the equation (4):

As can be seen from the equation (5), the frequency is closely related if the space of the quasi-electrostatic field whose intensity is greater than the radiative electric field and the inductive electromagnetic field is greater. As the frequency is lower, the space of the quasi-electrostatic field whose intensity is greater than the radiative electric field and the inductive electromagnetic field is greater. Specifically, the distance up to the intensity boundary point shown inFIG. 3is greater as the frequency is lower, i.e., is shifted to the right as the frequency is lower. Conversely, as the frequency is higher, the space of the quasi-electrostatic field whose intensity is greater than the radiative electric field and the inductive electromagnetic field is smaller. Specifically, the distance up to the intensity boundary point shown inFIG. 3is smaller as the frequency is higher, i.e., is shifted to the left as the frequency is higher.

If the frequency of 1 [MHz], for example, is selected, then according to the above equation (5), as can be understood fromFIG. 4which shows the distance in an antilogarithmic scale, the intensity of the quasi-electrostatic field in a space up to a position that is 2 [m] spaced from the electric field source is about 13 [dB] greater than the inductive electromagnetic field. In this space, therefore, the quasi-electrostatic field can be detected without being essentially subject to the inductive electromagnetic field and the radiative electric field.

(2-2) Measurement of a Distance Using the Quasi-Electrostatic Field

Based on the above properties of the quasi-electrostatic field, as shown inFIG. 5, the distance sensor S1which includes the quasi-electrostatic field sensor generates a plurality of quasi-electrostatic fields corresponding to respective frequencies f1through fn. The frequency f1of 1 [MHz] is associated as a reference frequency to a range of 0.01 [m] from the distance sensor S1, i.e., a distance of 0.01 [m] from the distance sensor S1. The frequencies f2through fn are progressively lower in the order named, and are associated to respective ranges which are progressively greater by 0.01 [m]. The distance sensor S1detects variations of the quasi-electrostatic fields (potential changes) which are caused when the user enters the quasi-electrostatic fields, and identifies a frequency corresponding to the quasi-electrostatic field whose variation has exceeded a predetermined threshold value. The distance sensor S1then detects the distance corresponding to the identified frequency as the distance from the distance sensor S1to the user.

The distance sensor S1which includes the quasi-electrostatic field sensor is thus arranged to detect the distance up to the user who is present in the space around the distance sensor S1, using the quasi-electrostatic field. For details of the quasi-electrostatic field sensor, reference should be made to Japanese patent application No. 2003-160816 which was filed by the present applicant and has already been published.

(3) Structural Details of a Music Playback Robot Device

A music playback robot device10shown inFIGS. 6A,6B, and7as a specific example of the electronic device with the quasi-electrostatic field sensors will be described below.

The music playback robot device10has a substantially ellipsoidal casing11. The music playback robot device10also has identically shaped annular left and right wheels12,13mounted on and projecting outwardly from the outer circumferential surface of the ellipsoidal casing11. The left and right wheels12,13are positioned in respective left and right vertical planes SA, SB spaced equal distances from a central point P1of the ellipsoidal casing11and extending perpendicularly to a horizontal axis L1of the casing ellipsoidal11. The horizontal axis L1extends as a straight line passing through the central point P1and crest points P2, P3of the ellipsoidal casing11which are spaced the greatest distance from each other on the outer circumferential surface of the ellipsoidal casing11.

The annular left and right wheels12,13have respective outside diameters which are greater than the maximum outside diameter of the ellipsoidal casing11around the horizontal axis L1. The annular left and right wheels12,13are mounted on the ellipsoidal casing11for angular movement in a direction D1around the horizontal axis L1and an opposite direction D2around the horizontal axis L1. When the music playback robot device10is placed on a horizontal surface, for example, only the left and right wheels12,13are held in contact with the horizontal surface and support the ellipsoidal casing11horizontally off the horizontal surface. When the left and right wheels12,13are controlled to turn independently of each other, the ellipsoidal casing11is angularly moved clockwise or counterclockwise as shown inFIG. 8or moved forward, obliquely forward to the left, obliquely forward to the right, backward, obliquely backward to the left, or obliquely backward to the right.

The ellipsoidal casing11includes a central casing14positioned between the left and right wheels12,13, a substantially conical left casing15positioned leftward of the central casing14and tapered leftward from the central casing14toward the horizontal axis L1, and a substantially conical right casing16positioned rightward of the central casing14and tapered rightward from the central casing14toward the horizontal axis L1.

The central casing14houses a weight17such as a battery or the like at a central lower position therein. The weight17places the center of gravity of the central casing14vertically below the central point P1. With the center of gravity being thus positioned, even though the music playback robot device10is held in contact with the horizontal surface through two points, i.e., the left wheel12and the right wheel13, the central casing14is prevented from being continuously rotated about the horizontal axis L1in the direction D1and the direction D2and has its posture held stably when the music playback robot device10is moving on the horizontal surface.

The left casing15includes a left rotor18rotatably mounted on the central casing14for angular movement about the horizontal axis L1in the direction D1and the direction D2(seeFIGS. 6A,6B), and a left openable and closable body20attached to a left side of the left rotor18by a hinge19so that the left openable and closable body20can be opened outwardly and closed inwardly on the left of the left rotor18. The left rotor18supports on its outer surface a left light emitter21such as a light-emitting diode or the like. The left openable and closable body20houses a speaker22disposed therein. When the left openable and closable body20is opened outwardly to the left about the hinge19, the front surface of the vibrating plate of the speaker22is exposed outwardly, as shown inFIG. 6B.

Similarly, the right casing16includes a right rotor23rotatably mounted on the central casing14for angular movement about the horizontal axis L1in the direction D1and the direction D2(seeFIGS. 6A,6B), and a right openable and closable body25attached to a right side of the right rotor23by a hinge24so that the right openable and closable body25can be opened outwardly and closed inwardly on the right of the right rotor23. The right rotor23supports on its outer surface a left light emitter26such as a light-emitting diode or the like. The right openable and closable body25houses a speaker27disposed therein. When the right openable and closable body25is opened outwardly to the right about the hinge24, the front surface of the vibrating plate of the speaker27is exposed outwardly, as shown inFIG. 6B.

As shown inFIG. 7, the surface of the ellipsoidal casing11which is viewed when the left casing15is positioned on the left and the right casing16on the right serves as a front surface of the ellipsoidal casing11. When the front surface of the ellipsoidal casing11faces the user, the user enters commands into the music playback robot device10for playing back music. Therefore, the music playback robot device10is premised on such usage that the user enters commands into the music playback robot device10while the front surface of the ellipsoidal casing11is facing the user.

The music playback robot device10has a front distance sensor28disposed in the central casing14at an upper front position therein, a left distance sensor29disposed in the left casing15at an upper position therein, and a right distance sensor30disposed in the right casing16at an upper position therein. Each of the front distance sensor28, the left distance sensor29, and the right distance sensor30includes a quasi-electrostatic field sensor as described above for detecting the distance up to the user using a quasi-electrostatic field. Based on detected results from the front distance sensor28, the left distance sensor29, and the right distance sensor30which are located at different positions in the ellipsoidal casing11, the music playback robot device10recognizes the distance up to the user which is present near the ellipsoidal casing11, and the direction of the user, i.e., the position of the user, as viewed from the front side of the ellipsoidal casing11.

(4) Music Data Transfer System

A music data transfer system40for transferring music data to the music playback robot device10will be described below with reference toFIG. 9. As shown inFIG. 9, the music data transfer system40has a data transfer device41in the form of a personal computer. The data transfer device41acquires music data through a network43from a music data providing server42which provides music data, or acquires music data from a recording medium44such as a CD (Compact Disc) which stores recorded music data.

The data transfer device41performs a frequency analyzing process on music data to be transferred to the music playback robot device10for analyzing music elements based on the music data. The data transfer device41obtains analyzed music information INF1representative of analyzed frequencies of the music data along a playback time axis AX1of the music data to be transferred, as shown inFIG. 10.

Based on the analyzed music information INF1, the data transfer device41generates drive information INF2including, along the playback time axis AX1, a left wheel command value and a right wheel command value for commanding rotating directions, angular displacements, and rotational speeds of the left wheel12and the right wheel13, a left rotor command value and a right rotor command value for commanding rotating directions, rotational speeds, and rotational angles of the left rotor18and the right rotor23, a left openable and closably body command value and a right openable and closably body command value for commanding opening and closing angles and opening and closing speeds of the left openable and closably body20and the right openable and closably body25, and a left light emitter command value and a right light emitter command value for commanding light-emitting states (e.g., colors and brightnesses) of the left light emitter21and the right light emitter26.

The data transfer device41thus produces drive information INF2for driving various components of the ellipsoidal casing11, i.e., the left wheel12, the right wheel13, the left rotor18, the right rotor23, the left openable and closably body20, the right openable and closably body25, the left light emitter21, and the right light emitter26, to the music elements based on the music data. The drive information INF2shown inFIG. 10represents the left openable and closably body command value and the right openable and closably body command value for the left openable and closably body20and the right openable and closably body25, respectively.

When the user instructs the data transfer device41to transfer data, the data transfer device41transfers the music data and the drive information INF2corresponding to the music data to the music playback robot device10successively through a cable45and a cradle46on which the music playback robot device10is placed.

(5) Circuit Arrangement of the Music Playback Robot Device

Various circuits of the music playback robot device10will be described below with reference toFIG. 11. As shown inFIG. 11, the circuits of the music playback robot device10are controlled by a controller50which is also a circuit of the music playback robot device10. The controller50executes various processing operations according to a program stored in a memory51. Specifically, the controller50writes the music data transferred from the external data transfer device41successively through the cable45and the cradle46and the drive information INF2corresponding to the music data into the memory51.

When the controller50recognizes removal of the music playback robot device10from the cradle46, the controller50acquires distance information DI representing the distance up to the user detected by the front distance sensor28, the distance up to the user detected by the left distance sensor29, and the distance up to the user detected by the right distance sensor30, from a detector52which includes the front distance sensor28, the left distance sensor29, and the right distance sensor30.

From the distance information DI, the controller50recognizes the distance up to the user detected by the front distance sensor28, the distance up to the user detected by the left distance sensor29, and the distance up to the user detected by the right distance sensor30. Based on the recognized distances, the controller50calculates the distance from the ellipsoidal casing11to the user and the direction of the user as viewed from the front side of the ellipsoidal casing11. Actually, as shown inFIG. 12, the controller50calculates a point of intersection of a sphere having the front distance sensor28at its center and a radius represented by the distance up to the user detected by the front distance sensor28, a sphere having the left distance sensor29at its center and a radius represented by the distance up to the user detected by the left distance sensor29, and a sphere having the left distance sensor30at its center and a radius represented by the distance up to the user detected by the left distance sensor30, thereby specifying the distance from the ellipsoidal casing11to the user and the direction of the user as viewed from the front side of the ellipsoidal casing11.

After having specified the distance up to the user and the direction of the user as viewed from the front side, the controller50controls a wheel driver53depending on the direction of the user as viewed from the front side to rotate the left wheel12and the right wheel13in opposite directions, respectively, to change the orientation of the ellipsoidal casing11so that the front side thereof faces the user. The controller50then controls the wheel driver53depending on the distance up to the user to rotate the left wheel12and the right wheel13in the same direction to move the ellipsoidal casing11forward until the distance up to the user will be within a predetermined range.

As described above, the based on the distance information DI acquired from the detector52, the controller50orients the front side of the ellipsoidal casing11to the user and moves the ellipsoidal casing11toward the user. This mode of operation for moving the ellipsoidal casing11toward the user is referred to as a user tracking mode of the controller50.

When the distance between the user and the ellipsoidal casing11falls within the predetermined range, e.g., 30 cm, the controller50controls the wheel driver53to stop rotating the left wheel12and the right wheel13, and then switches from the user tracking mode to a command entry mode for accepting a command entered by the user. Therefore, when the user is present within the predetermined range from the ellipsoidal casing11, the controller50enters the command entry mode. The predetermined range will hereafter be referred to as a command entry range.

A command entry process of the music playback robot device10will be described in detail below. The music playback robot device10calculates movement of a hand of the user which is moved in a space around the ellipsoidal casing11based on the detected results from the front distance sensor28, the left distance sensor29, and the right distance sensor30, and accepts a command entered depending on the movement of the hand in a non-contact fashion.

Actually, the controller50acquires the distance information DI at given time intervals from the detector52. As shown inFIG. 13A, when the controller50recognizes that, within the command entry range (e.g., 30 cm), the user's hand approaching the ellipsoidal casing11from the right as viewed from the front side of the ellipsoidal casing11, i.e., the user's hand approaching the left casing15, comes to a position in which the distance up to the user's hand detected by the left distance sensor29is equal to or smaller than a predetermined threshold value (e.g., 10 cm), the controller50determines that the user's hand is positioned near the left casing15, and stores, into the memory51, for example, the positional data at this time of the user's hand as coordinate data in a three-dimensional space represented by a three-dimensional coordinate system having three orthogonal axes, i.e., X-, Y-, Z-axes and an origin located at the central point P1of the ellipsoidal casing11, as shown inFIG. 13B.

If the sign of the X-axis coordinate data of the user's hand is positive, then the user's hand is positioned leftward of the origin as viewed from the front side of the ellipsoidal casing11. If the sign of the X-axis coordinate data of the user's hand is negative, then the user's hand is positioned rightward of the origin as viewed from the front side of the ellipsoidal casing11. If the sign of the Y-axis coordinate data of the user's hand is positive, then the user's hand is positioned upward of the origin, and if the sign of the Y-axis coordinate data of the user's hand is negative, then the user's hand is positioned downward of the origin. If the sign of the Z-axis coordinate data of the user's hand is positive, then the user's hand is positioned forward of the origin, and if the sign of the Z-axis coordinate data of the user's hand is negative, then the user's hand is positioned rearward of the origin.

Thereafter, as shown inFIG. 14A, when the controller50recognizes that the user's hand moving in a direction from the left casing15to the central casing14and approaching the central casing14comes to a position in which the distance up to the user's hand detected by the front distance sensor28is equal to or smaller than a predetermined threshold value (e.g., 10 cm), the controller50determines that the user's hand is positioned near the central casing14, and stores the positional data at this time of the user's hand as coordinate data in the three-dimensional space into the memory51, as shown inFIG. 14B.

Subsequently, as shown inFIG. 15A, when the controller50recognizes that the user's hand moving in a direction from the central casing14to the right casing16and approaching the right casing16comes to a position in which the distance up to the user's hand detected by the right distance sensor30is equal to or smaller than a predetermined threshold value (e.g., 10 cm), the controller50determines that the user's hand is positioned near the right casing16, and stores the positional data at this time of the user's hand as coordinate data in the three-dimensional space into the memory51, as shown inFIG. 15B.

Each time the controller50stores coordinate data into the memory51, the controller50calculates a path from the preceding coordinate data to the present coordinate data, and stores path data representing the calculated path into the memory51. The controller50thus calculates a path followed by the user's hand when the user's hand is moved from the right to the left as viewed from the front side of the ellipsoidal casing11, for example. The controller50then compares the calculated path data with patterns of path data stored in advance in the memory51in association with commands. If the calculated path data agrees with a pattern of path data which may be associated with a music playback command, for example, then the controller50determines that the movement of the user's hand represents a command for music playback, and enters the command for music playback, whereupon the controller50enters a music playback mode for playing back music.

In the music playback mode, the controller50reads music data stored in the memory51(FIG. 11). A music processor54processes the music data read by the controller50, e.g., converts the music data from digital data into analog data, and amplifies the music data, to produce a music signal. Then, speakers22,27output music sounds based on the music signal from the music processor54.

At this time, the controller50drives the various components of the ellipsoidal casing11, i.e., the left wheel12, the right wheel13, the left rotor18, the right rotor23, the left openable and closably body20, the right openable and closably body25, the left light emitter21, and the right light emitter26, in synchronism with the music elements (tempo, musical pitches, etc.) based on the music data being played back.

Specifically, the controller50reads the drive information INF2corresponding to the music data being played back from the memory51, and controls the wheel driver53, a rotor driver55, an openable/closable body driver56, left light emitter21, and the right light emitter26based on the read drive information INF2.

As a result, the wheel driver53rotates the left wheel12and the right wheel13in synchronism with the music elements based on the music data being played back. The controller50can thus move the ellipsoidal casing11in synchronism with the music elements of the music that is being output from the speakers22,27.

Under the control of the controller50, the rotor driver55rotates the left rotor18and the right rotor23in synchronism with the music elements based on the music data being played back. The controller50can thus rotate the left rotor18and the right rotor23with respect to the central casing14in synchronism with the music elements of the music that is being output from the speakers22,27.

Under the control of the controller50, the openable/closable body driver56opens and closes the left openable and closable body20and the right openable and closable body25in synchronism with the music elements based on the music data being played back. The controller50can thus open and close the left openable and closable body20and the right openable and closable body25in synchronism with the music elements of the music that is being output from the speakers22,27.

Under the control of the controller50, the left light emitter21, and the right light emitter26emit in various emitting states in synchronism with the music elements based on the music data being played back. The controller50can thus emit in synchronism with the music elements of the music that is being output from the speakers22,27.

Therefore, the music playback robot device10can move around as if dancing to the music that is being output from the speakers22,27in the music playback mode.

(6) Operating Sequence

An operating sequence of the music playback robot device10from the user tracking mode to the music playback mode will be described below with reference toFIG. 16. The operating sequence is carried out by the controller50according to the program installed in the memory51.

As shown inFIG. 16, when the ellipsoidal casing11is removed from the cradle46, the controller50starts an operating sequence RT1, whereupon control goes to step SP1. In step SP1, the controller50enters the user tracking mode and acquires distance information DI from the detector52. Then, control goes to step SP2.

In step SP2, the controller50calculates the distance from the ellipsoidal casing11to the user and the direction in which the user is present as viewed from the front side of the ellipsoidal casing11, based on the distance information DI. Then, control goes to step SP3. In step SP3, the controller50controls the wheel driver53to change the orientation of the ellipsoidal casing11so that its front surface faces the user, based on the direction in which the user is present as viewed from the front side of the ellipsoidal casing11. Then, control goes to step SP4.

In step SP4, the controller determines the position of the user is in the command entry range or not based on the distance up to the user. If the position of the user is not in the command entry range, then control goes from step SP4(NO in step SP4) to step SP5. In step SP5, the controller50controls the wheel driver53to move the ellipsoidal casing11forward, i.e., in the direction in which the user is present. After elapse of a predetermined time of 0.5 second, for example, control goes back to step SP1for the controller50to acquire the distance information DI.

Until the position of the user is brought into the command entry range, the controller50acquires the distance information DI at predetermined time intervals, and controls the wheel driver53in a feedback loop based on the distance information DI thereby to move the ellipsoidal casing11closely to the user so as to follow the user. Even if the user is moving, therefore, the music playback robot device10can recognize the user as it is moving and move closely to the user so as to follow the user.

If the ellipsoidal casing11has approached the user until the position of the user is in the command entry range, then control goes from step SP4(YES in step SP4) to step SP6. In step SP6, the controller50controls the wheel driver53to stop rotating the left wheel12and the right wheel13, and then switches from the user tracking mode to the command entry mode. Then, control goes to step SP7. If the position of the user is initially in the command entry range, then the controller50only changes the orientation of the ellipsoidal casing11, but not moves the ellipsoidal casing11. Thereafter, control goes from step SP4(YES in step SP4) to step SP6and then to step SP7.

In step SP7, the controller50acquires again the distance information DI from the detector52. Then, control goes to step SP8. In step SP8, the controller50calculates a path of movement of the user, i.e., the user's hand, based on the distance information DI, thereby obtaining calculated path data. Then, control goes to step SP9. In step SP9, the controller50determines whether the calculated path data is in agreement with any of the patterns of path data stored in advance in the memory51in association with commands or not.

If the calculated path data is not in agreement with any of the stored patterns of path data (NO in step SP9), then control goes back to step SP7for the controller50to acquire again the distance information DI. If the calculated path data is in agreement with one of the stored patterns of path data (YES in step SP9), then the controller50recognizes that the movement of the user's hand represents a command for music playback, for example. Control then goes to step SP10.

In step SP10, the controller50determines that the command corresponding to the movement of the user's hand is a command for music playback, for example. Then, control goes to step SP11. In step SP11, the controller50switches from the command entry mode to the music playback mode, and plays back the music data based on the music playback command and drives various components to the music data being played back. Thereafter, control goes to step SP12in which the operating sequence RT1is put to an end.

According to the operating sequence RT1, as described above, the controller50switches from the user tracking mode to the command entry mode to the music playback mode, and operates the various components and circuits of the music playback robot device10.

(7) Operation and Advantages

The controller50acquires, from the detector52, distance information DI representative of the distances up to the user which are detected respectively by the front distance sensor28disposed in the central casing14at the upper front position therein, the left distance sensor29disposed in the left casing15at the upper position therein, and the right distance sensor30disposed in the right casing16at the upper position therein.

In the present embodiment, each of the front distance sensor28, the left distance sensor29, and the right distance sensor30includes a quasi-electrostatic field sensor. As shown inFIG. 5, since the quasi-electrostatic field sensor is a nondirectional distance sensor, the distance up to the user which is present in the space around the distance sensor can be detected no matter which direction the user is in as viewed from the distanced sensor. Inasmuch as the front distance sensor28, the left distance sensor29, and the right distance sensor30, each including a nondirectional distance sensor, are located in different positions in the ellipsoidal casing11, it is possible to specify the position of the user, i.e., the distance up to the user and the direction in which the user is present, from the point of intersection of three spheres which represents the distances up to the user that are detected respectively by the front distance sensor28, the left distance sensor29, and the right distance sensor30.

Therefore, when the controller50calculates the distance from the ellipsoidal casing11up to the user and the direction of the user as viewed from the front side of the ellipsoidal casing11, based on the distance information DI acquired from the detector52, the controller50can recognize the distance from the ellipsoidal casing11up to the user, and also the direction of the user as viewed from the front side of the ellipsoidal casing11.

The quasi-electrostatic field sensor operates based on the properties of a quasi-electrostatic field that a potential change caused by an object differs depending on the specific inductive capacity of the object. Therefore, based on the potential change, a human being, i.e., the user, which is present among objects around the distance sensor, can be specified. The quasi-electrostatic field sensor according to an embodiment of the present invention is thus effective to prevent objects other than a human being from being detected in error and to detect the distance up to a human being reliably.

Depending on the recognized direction of the user, the controller50controls the wheel driver53to change the orientation of the ellipsoidal casing11so that the front side thereof faces the user. Therefore, the music playback robot device10can be used by the user in an orientation which is supposed to be kept in use, i.e., the orientation in which the front surface of the ellipsoidal casing11faces the user, without the need for the user to move to the front side of the ellipsoidal casing11or to change the orientation of the ellipsoidal casing11.

After having directed the front surface of the ellipsoidal casing11toward the user, the controller50controls the wheel driver53depending on the recognized distance up to the user to move the ellipsoidal casing11toward the user until the position of the user falls in the command entry range. When the position of the user is in the command entry range, the controller50stops moving the ellipsoidal casing11and waits for a command to be entered by the user. Therefore, the user does not have to move toward the music playback robot device10for entering a command, but the music playback robot device10automatically moves into the command entry range for the user to enter a command.

While waiting for a command to be entered by the user, the controller50acquires the distance information DI at given time intervals from the detector52, and calculates a path of the user's hand moved around the ellipsoidal casing11based on the successively acquired distance information DI. Then, the controller50compares the calculated path data with patterns of path data stored in advance in the memory51in association with commands. If the calculated path data agrees with a pattern of path data which may be associated with a music playback command, for example, then the controller50determines that the movement of the user's hand represents a command for music playback, and enters the command for music playback. The music playback robot device10is thus capable of entering a plurality of commands depending on the movement of the user's hand in a non-contact fashion simply by presetting as many patterns of path data as the number of commands, without the need for contact-type input elements such as operation buttons on the ellipsoidal casing11.

As the front surface of the ellipsoidal casing11is oriented at all times toward the user, the orientation of the ellipsoidal casing11as viewed from the user remains the same at all times. As a result, the movement of the user's hand as viewed from the user and the entry of a command are associated with each other identically at all times, allowing the user to enter a command with ease. Therefore, the music playback robot device10allows the user to enter a command in an orientation which is supposed to be held when a command is entered.

With the above arrangement, the music playback robot device10calculates a direction in which the user is present as an object, based on the distances up to the user which are detected respectively by the front distance sensor28, the left distance sensor29, and the right distance sensor30which are located in different positions in the ellipsoidal casing11, and changes the orientation of the ellipsoidal casing11into alignment with the calculated direction. Therefore, the music playback robot device10can be used by the user in the orientation depending on the direction in which the user is present, i.e., in the direction in which the playback robot device10is supposed to be used, without the need for the user to move with respect to the playback robot device10or to change the orientation of the ellipsoidal casing11with respect to the user. Consequently, the music playback robot device10as the electronic device according to the present invention is much easier to use than heretofore, and a method of controlling the music playback robot device10according to the present invention allows the music playback robot device10to be used much easier than heretofore.

(8) Other Embodiments

According to the above embodiment, when the music playback robot device10recognizes the direction of the user as viewed from the front side of the ellipsoidal casing11, the music playback robot device10changes the orientation of the ellipsoidal casing11on site to direct the front surface of the ellipsoidal casing11toward the user and thereafter moves the ellipsoidal casing11toward the user until the distance up to the user will be in the command entry range. However, as shown inFIG. 17, if the user is present obliquely forward to the right as viewed from the front side of the ellipsoidal casing11, the orientation of the ellipsoidal casing11may not be changed on site, but the ellipsoidal casing11may be turned while moving obliquely forward to the right, so that front surface of the ellipsoidal casing11will face the user and the ellipsoidal casing11will approaches the user. According to the embodiment shown inFIG. 17, even a music playback robot device which has a four-wheel drive mechanism and which cannot be turned on site offers the same advantages as the above two-wheeled music playback robot device10. Stated otherwise, the music playback robot device10may have a drive mechanism other than the two-wheel drive mechanism. The drive mechanism includes, for example, the left wheel12, the right wheel13, and the wheel driver53of the music playback robot device10.

According to the above embodiment, in the music playback mode, music sounds are output from the speakers22,27as a music output unit, and the left wheel12, the right wheel13, the left rotor18, the right rotor23, the left openable and closably body20, the right openable and closably body25, the left light emitter21, and the right light emitter26are driven to move around to the music being played back. However, in the music playback mode, the left wheel12and the right wheel13may be stopped to keep the music playback robot device10at rest, and the left rotor18and the right rotor23may be rotated and the left openable and closably body20and the right openable and closably body25may be opened and closed for bringing the front surfaces of the vibrating plates of the speakers22,27into facing relationship to the user which is positioned in front of the ellipsoidal casing11. According to this modification, since music sounds are output from the speakers22,27while the front surfaces of the vibrating plates of the speakers22,27are facing the user, the user is allowed to listen to the music being played back at all times in a good listening position without the need for the user to move or to change the orientation of the ellipsoidal casing11.

In the above embodiment, the present invention is applied to the self-propelled music playback robot device10. However, the present invention is also applicable to various electronic devices including a self-propelled image playback robot device having a display unit as an image output unit including a liquid crystal display, on the front surface of the ellipsoidal casing11; a stationary display device with a swiveling display surface; a stationary speaker device with a swiveling speaker front surface; etc. If the present invention is applied to a stationary display device with a swiveling display surface, then though the stationary display device is unable to move toward the user, the stationary display device is capable of recognizing the direction of the user and turning the display surface so as to faced the user, so that the user can see displayed images at all times from a good viewing position.

In the above embodiment, the present invention is applied to the music playback robot device10which is capable of entering commands in a non-contact fashion. However, the present invention is applicable to a remote controller which is capable of entering commands in a non-contact fashion. According to this modification, the music playback robot device10has a communication unit controlled by the controller50for communicating with an external device. When the position of the user is brought into the command entry range, the controller50stops moving the ellipsoidal casing11, and sends a signal to turning on the power supply of the external device through the communication unit to the external device. The controller50then waits for a command to be entered by the user for the external device. The controller50sends a signal depending on the entered command through the communication unit to the external device. In this manner, the music playback robot device10functions as a remote controller. The remote controller can automatically move into the command entry range to allow the user to enter a command in a non-contact fashion without the need for the user to approach the remote controller for entering a command or to lift the remote controller in a predetermined orientation. The communication unit may employ an infrared communication process such as IrDA (registered trademark) or a wireless communication process such as Bluetooth (registered trademark) or HomeRF (registered trademark).

According to the above embodiment, when the user's hand is moved in the direction from the left casing15to the right casing16of the ellipsoidal casing11, i.e., from the left to the right as viewed from the user, in the space near the ellipsoidal casing11, a music playback command, for example, as a command corresponding to the movement of the user's hand is entered into the music playback robot device10. However, a pattern of path data representing the movement of the user's hand from the right to the left, a pattern of path data representing the movement of the user's hand from a front position to a rear position, a pattern of path data representing the movement of the user's hand from a rear position to a front position, a pattern of path data representing the movement of the user's hand from a lower position to an upper position, etc. may be stored in advance in the memory51, and these patterns of path data may be associated respectively with a fast-forward command, a rewind command, a volume up command, and a volume down command for the music data. Any of these commands can be entered when the user's hand makes a corresponding movement.

According to the above embodiment, the front distance sensor28is disposed in the central casing14of the ellipsoidal casing11at the upper front position therein, the left distance sensor29is disposed in the left casing15of the ellipsoidal casing11at the upper position therein, and the right distance sensor30of the ellipsoidal casing11is disposed in the right casing16at the upper position therein. However, distance sensors may be disposed respectively in the central casing14at a central rear position therein, in the left casing15at a central position therein, and in the right casing16at a central position therein. According to the present invention, the distance sensors may be positioned in other positions than the illustrated positions insofar as the position of the user can be calculated from the distances detected by the distance sensors.

According to the above embodiment, each of the front distance sensor28, the left distance sensor29, and the right distance sensor30includes a quasi-electrostatic field sensor. However, a distance sensor such as a PSD (Position Sensing Device) or an ultrasonic sensor may be used instead of a quasi-electrostatic field sensor, or various these distance sensors may be used in combination. In addition, a distance sensor such as an infrared sensor, for example, for detecting the distance up to the user which is present in a predetermined direction may be employed. In such a case, a plurality of (e.g., several tens to several hundreds) distance sensors for detecting the distances up to users which are present in different directions may be mounted on substantially the entire surface of the ellipsoidal casing11for specifying the positions of the users which are present in the space around the ellipsoidal casing11.

In the above embodiment, the three distance sensors are disposed at different positions in the ellipsoidal casing11. However, more than three distance sensors may be employed. Actually, an increased number of distance sensors allow the movement of the user's hand for entering a command to be recognized with a greater resolution, so that smaller patterns of the movement of the user's hand may be associated with commands.

In the above embodiment, the substantially ellipsoidal casing11is employed. However, any of casings having various other shapes may be used.

In the above embodiment, the music playback robot device10is made up of the controller50, the memory51, the detector52, the wheel driver53, the music processor54, the rotor driver55, the openable/closable body driver56, the speakers22,27, and the light emitters21,26. However, the music playback robot device10may have any of other configurations insofar as they have the same functions as described above.

The electronic device1shown inFIGS. 1 and 2corresponds to the music playback robot device10shown inFIGS. 6,7, and11. The main body2(seeFIG. 1) of the electronic device1corresponds to the ellipsoidal casing11(seeFIG. 6) of the music playback robot device10. The distance sensors S1, S2, S3(seeFIG. 1) correspond to the front distance sensor28, the left distance sensor29, and the right distance sensor30(seeFIG. 6), respectively. The drive mechanism3(seeFIG. 2) corresponds to the left wheel12, the right wheel13(seeFIG. 6), and the wheel driver53(seeFIG. 11). The detector4(seeFIG. 2) corresponds to the detector52(seeFIG. 11). The calculator5and the controller6(seeFIG. 2) correspond to the controller50(seeFIG. 11).

In the above embodiment, the controller50software-implements the above operating sequence according to the program installed in the music playback robot device10. However, the music playback robot device10may have a dedicated circuit for performing the operating sequence, and the operating sequence may be hardware-implemented by the dedicated circuit. The program for performing the operating sequence may be recorded in a recording medium such as a CD or the like.