Abstract:
The robot ball comprises an encapsulating shell, a drive system and a steering system. The shell has an axis of rotation and an outer annular tread surface centered on the axis of rotation. The drive system is encapsulated in the shell and comprises a first motorized mechanism and a counterweight. The first motorized mechanism has a stator portion and a rotor portion centered on the axis of rotation and connected to the shell. The counterweight is connected to the stator portion and is spaced apart from the axis of rotation whereby, due to inertia of the counterweight, rotation of this rotor portion rotates the shell to roll the tread surface on the ground. The steering system comprises a second motorized mechanism through which the counterweight is connected to the stator portion. This second motorized mechanism includes a pivot assembly having a pivot axis transversal to the axis of rotation. Therefore, activation of the second motorized mechanism rotates the counterweight about the pivot axis, tilts the axis of rotation, displaces the center of gravity of the robot ball, and thereby changes the trajectory of the robot ball. An inclinometer is mounted on the stator portion to measure an inclination of the stator portion about the axis of rotation, and a controller regulates the speed of rotation of the rotor portion in relation to the measured inclination. The robot ball further includes a second inclinometer so mounted on the platform as to measure an inclination about the pivot axis. The controller then controls the electric servomotor in relation to the measured platform inclination about the pivot axis.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an autonomous robot ball capable of displacing in various environments, including indoors as well as outdoors. 
     2. Brief Description of the Prior Art 
     Upon designing a robot, the main difficulty is to make it sufficiently robust to sustain all environmental and operating conditions: shocks, stairs, carpets, various obstacles, manipulations by the children in the case of a toy, etc. 
     Prior art wheeled robot can turn upside down and, then, be incapable of relieving this deadlock. 
     A prior art solution to this problem is to use wheels bigger than the body of the robot. However, this does not prevent the robot from blocking in elevated position onto an object. 
     Another solution to this problem is described in the following prior art patents: 
     U.S. 3,798,835 (McKeehan) Mar. 26, 1974 
     U.S. 5,533,920 (Arad et al.) Jul. 9, 1996 
     U.S. 5,947,793 (Yamakawa) Sep. 7, 1999 
     CA 2 091 218 (Christen) Jul. 5, 1994 
     This solution consists of building a robot around a spherical shell enclosing a drive system. This drive system comprises an electric drive motor for rotating the spherical shell about an axis of rotation and thereby propelling the robot. The counter-rotating force on the electric drive motor is produced by a counterweight spaced apart from the axis of rotation. A drawback of such prior art robot balls is that steering thereof is not provided for. 
     OBJECTS OF THE INVENTION 
     An object of the present invention is therefore to provide a robot ball having steering capabilities. 
     Another object of the present invention is to provide a robot ball comprising an inclinometer to control the speed of rotation of the electric drive motor in relation to the angular position of the counterweight about the axis of rotation. 
     SUMMARY OF THE INVENTION 
     More specifically, in accordance with the present invention, there is provided a robot ball comprising an encapsulating shell, a drive system encapsulated in the shell and comprising a first motorized mechanism and a counterweight, and a steering system comprising a second motorized, counterweight displacing mechanism. The encapsulating shell has an axis of rotation and an outer annular tread surface centered on this axis of rotation. The first motorized mechanism has a stator portion and a rotor portion centered on the axis of rotation and connected to the shell. The counterweight is connected to the stator portion and spaced apart from the axis of rotation whereby, due to inertia of the counterweight, rotation of the rotor portion rotates the shell to roll the tread surface on the ground. The second motorized mechanism connects the counterweight to the stator portion, and defines a course of displacement of the counterweight which extends along the axis of rotation. 
     In operation, activation of the second motorized mechanism displaces the counterweight along the axis of rotation, tilts this axis of rotation, displaces the center of gravity of the robot ball, and thereby changes the trajectory of the robot ball. This provides for steering of the robot ball. 
     According to a preferred embodiment, the second motorized mechanism includes a pivot assembly having a pivot axis transversal to the axis of rotation whereby, in operation, activation of the second motorized mechanism rotates the counterweight about the pivot axis, tilts the axis of rotation, displaces the center of gravity of the robot ball, and thereby changes the trajectory of the robot ball. 
     In accordance with other preferred embodiments of the robot ball: 
     the encapsulating shell comprises a generally spherical outer face; 
     the annular tread surface is generally elliptical in a cross sectional plane in which the axis of rotation is lying; 
     the pivot axis is substantially perpendicular to the axis of rotation; 
     the stator portion comprises a platform; 
     the first motorized mechanism comprises at least one electric drive motor having a stator and a rotor, the stator of the electric motor is secured to the platform, the rotor of the electric motor is centered on the axis of rotation and is connected the shell; 
     the first motorized mechanism comprises first and second electric drive motors each having a stator and a rotor, the stator of the first electric drive motor is secured to the platform, the stator of the second electric drive motor is secured to the platform, the rotor of the first electric drive motor is centered on the axis of rotation and is connected a first point of the shell, and the rotor of the second electric drive motor is centered on the axis of rotation and is connected to a second point of the shell diametrically opposite to the first point of this shell; 
     the platform comprises an underside, the second motorized mechanism comprises an electric servomotor having a stator and a rotor, the stator of the electric servomotor is secured to the underside of the platform, and the rotor of the electric servomotor is centered on the pivot axis and is connected to the counterweight; 
     the counterweight comprises an electric battery; 
     the counterweight comprises an electric battery and a bracket to mechanically connect the battery to the rotor of the servomotor; 
     the robot ball further comprises an inclinometer so mounted on the platform as to measure an inclination of this platform about the pivot axis, and a controller of the electric servomotor in relation to the measured platform inclination about the pivot axis; and 
     the robot ball further comprises at least one external sensors and a robot ball controller responsive to these sensors, these external sensors comprise a robot ball spin sensor unit detecting spinning of the robot ball, a voice instructions recognising system, and/or a tactile system, and the robot ball further comprises a voice message generating system controlled by the robot ball controller; 
     the robot ball further comprises an obstacle detector and a controller of the second motorized mechanism in response to an obstacle detected by the obstacle detector. 
     Also in accordance with the present invention, there is provided a robot ball comprising an encapsulating shell, a drive system encapsulated in the shell and comprising a motorized mechanism and a counterweight, an inclinometer and a controller. The encapsulating shell has an axis of rotation and an outer annular tread surface centered on the axis of rotation. The motorized mechanism has a stator portion and a rotor portion centered on the axis of rotation and connected to the shell. The counterweight is connected to the stator portion and spaced apart from the axis of rotation whereby, due to inertia of the counterweight, rotation of the rotor portion rotates the shell to roll the tread surface on the ground. The inclinometer is so mounted on the stator portion as to measure an inclination of this stator portion about the axis of rotation, and the controller regulates the speed of rotation of the rotor portion in relation to the measured inclination. 
     In this manner, the inclinometer allows the robot ball to control the angular position of the motorized mechanism about the axis of rotation. 
     Preferably, the stator portion comprises a platform and the inclinometer is mounted on the platform. 
     According to a preferred embodiment, the motorized mechanism comprises at least one electric drive motor having a stator and a rotor, the stator of the electric drive motor is secured to the platform, the rotor of the electric drive motor is centered on the axis of rotation and is connected the shell, the inclinometer is mounted on the platform to measure an inclination of this platform about the axis of rotation, and the controller is a controller of the speed of rotation of the electric drive motor in relation to the measured platform inclination. 
     Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of a preferred embodiment thereof, given by way of example only with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the appended drawings: 
     FIG. 1 is a side, perspective view of the preferred embodiment of the robot ball according to the present invention; 
     FIG. 2 is a side elevational view of the robot ball of FIG. 1; 
     FIG. 3 is a rear, perspective view of the robot ball of FIG. 1; 
     FIG. 4 is a side, elevational view of the drive and steering systems of the robot ball of FIG. 1; 
     FIG. 5 is a side, elevational view of the drive and steering systems of the robot ball of FIG. 1; 
     FIG. 6 is another side, elevational view of the drive and steering systems of the robot ball of FIG. 1; 
     FIG. 7 is a rear, elevational view of the drive and steering systems of the robot ball of FIG. 1; 
     FIG. 8 is another rear, elevational view of the drive and steering systems of the robot ball of FIG. 1; 
     FIG. 9 is a top plan view of an obstacle detector of the robot ball of FIG. 1; 
     FIG. 10 is a schematic block diagram of an electronic controller of the robot ball of FIG. 1; and 
     FIG. 11 is a schematic block diagram showing different states of the robot ball. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A preferred embodiment of the robot ball according to the present invention will now be described. In the appended drawings, the robot ball is generally identified by the reference  1 . Also, identical elements are identified by the same references in the different figures of the drawings. 
     Encapsulating Shell  2   
     As illustrated in FIGS. 1-3, the robot ball  1  is encapsulated in a shell  2 . As will be seen in the following description, the shell  2  is rotated about an axis of rotation  3  to propel the robot ball  1 . For that purpose, the shell  2  will be preferably spherical to provide for a uniform tread  4  semicircular in the cross section defined by a plane in which the axis of rotation  3  is lying. 
     In the present specification and the appended claims, the term “ground” is intended to designate interior ground surfaces as well as exterior ground surfaces. This will include the floor of a house, concrete floors, lawn, pavement, etc. 
     However, this is within the scope of the present invention to provide a shell  2  which is oval-shaped in the same cross section, defined by a plane in which the axis of rotation  3  is lying. In such a case, the tread  4  will be broadly elliptical in cross section. This is even within the scope of the present invention to provide a shell  2  having a tread  4  broadly elliptical in cross section in the above defined plane in which the axis  3  is lying, with two parallel, flat opposite sides. 
     Generally speaking, the shell  2  will present a shape susceptible to facilitate displacement of the robot ball  1 . To that effect, the shell  2  will be spherical or oval-shaped as described above. The shell  2  can also be hexagonal, spherical with cylindrical extensions centered on the axis of rotation  3 , etc. The shell  2  may further comprise paddles to displace the robot ball  1  on a surface of water. 
     Also, the surface of the tread  4  can be formed with corrugations such as  5  to better grip the surface of the ground. 
     Of course, the shell  2  can be reinforced as required for example by means of inner ribs. The shell  2  can further be made of transparent plastic material to enable any detection, for example to enable machine vision and obstacle detection, from inside the shell  2 . 
     Finally, the shell  2  can be made of two hemispheric parts or more than two parts which can be dismantled to enable opening of the shell  2  and therefore maintenance or repair of the robot ball  1 . An alternative is to provide the shell  2  with an access door. 
     Drive System 
     The robot ball  1  also comprises a drive system to roll the tread  4  of the shell  2  on the ground and therefore propel the robot ball  1 . The drive system generally comprises a platform  6 , a pair of reversible electric drive motors  7  and  8 , and a counterweight  9 . 
     Platform  6   
     As it will be described hereinafter, the platform  6  supports most of the internal components of the robot ball  1 , including the counterweight  9 . As illustrated in FIG. 1, the platform  6  is generally flat. Also, since the illustrated shell  2  is generally spherical, the platform  6  is shown generally circular, although a generally hexagonal or other suitable shapes can be contemplated. In the case of an oval-shaped shell  2 , the platform  6  could present a corresponding oval shape. 
     Drive Motors  7  and  8   
     Referring to FIG. 3, electric drive motor  7  comprises a housing  10  (stator) fixedly secured to the platform  6 . Electric drive motor  7  also comprises a rotative shaft  11  (rotor) connected to a first point of the shell  2  along the axis of rotation  3 . Just a word to mention that the shaft  11  is connected to the shell  2  to rotate said shell  2  therewith about axis  3 . For that purpose, the shaft  11  is centered on the axis of rotation  3  as illustrated in FIG.  3 . 
     In the same manner, electric drive motor  8  comprises a housing  12  (stator) fixedly secured to the platform  6 . Electric drive motor  8  also comprises a rotative shaft  13  (rotor) connected to a second point of the shell  2  diametrically opposite to the above mentioned first point. Just a word to indicate that the shaft  13  is connected to the shell  2  to rotate said shell  2  therewith about axis  3 . For that purpose, the shaft  13  is centered on the axis of rotation  3  as illustrated in FIG.  3 . 
     Accordingly, rotation of the shafts  11  and  13  of the electric drive motors  7  and  8  in one angular direction will rotate the shell  2  therewith in the same direction about the axis of rotation  3 . While rotation of the shafts  11  and  13  will tend to rotate the platform  6  about the axis of rotation  3 , the inertia of the counterweight  9  will provide the necessary counter-rotating force on the drive motors  7  and  8  to maintain the platform  6  in a substantially horizontal position as shown in FIG.  2 . Those of ordinary skill in the art will appreciate that rotation of the shafts  11  and  13 , in combination with the inertia of the counterweight  9  will cause rolling of the tread  4  on the ground to propel the robot ball  1 . 
     In the absence of obstacles along the trajectory of the robot ball  1 , speed regulation of the electric motors  7  and  8  will keep the platform  6  substantially horizontal over the duration of the displacement. 
     Since the electric drive motors  7  and  8  are reversible, the direction of movement of the robot ball  1  can be reversed by reversing the direction of rotation of these electric drive motors  7  and  8 . 
     Also, just a word to mention that the two drive motors  7  and  8  could be replaced by a single motor, if desired. 
     It should also be mentioned that the drive motors  7  and  8  can be equipped with single encoders or, alternatively, encoders in quadrature to enable a better regulation of the speed of rotation of the drive motors  7  and  8  and therefore the speed and trajectory of the robot ball  1 . 
     Counterweight  9   
     The counterweight  9  comprises a battery  14  presenting, in the illustrated example, the general configuration of an elongated parallelepiped. The battery  14  is supported from the underside of the platform  6  by a pair of end brackets  15  and  16 . 
     The battery  14  is preferably a rechargeable battery; charge connectors (not shown) for charging the battery  14  can be provided on the outer face of the shell  2  in the proximity of the axis  3  of this shell  2 . 
     As described hereinabove, the shell  2  can be opened for maintenance and repair purposes. Therefore, if non rechargeable batteries are used, the shell  2  can be opened when required to change the batteries. 
     Referring to FIGS. 2 and 3, the counterweight  9  can be pivoted about a pivot axis  17  perpendicular to the axis  3  but parallel to the plane of the platform  6 . 
     For that purpose, a bracket  18  is secured to the underside of the platform  6  and the upper portion of the bracket  15  is connected to the underside bracket  18  through a pivot  19  centered on the pivot axis  17 . 
     For the same purpose, the upper portion of the bracket  16  is connected to the underside of the platform  6  through a reversible electric servomotor  20 . Servomotor  20  comprises a housing  21  (stator) fixedly secured to the underside of the platform  6 . Servomotor  20  also comprises a rotative shaft  22  (rotor) centered on the pivot axis  17 . Just a word to mention that the rotative shaft  22  is connected to the upper portion of the bracket  16  in such a manner that the bracket  16  will be set into rotation about the pivot axis  17  by rotation of the shaft  22 . 
     In operation, activation of the servomotor  20  will rotate the counterweight  9  about the axis  17  to displace this counterweight along the axis of rotation  8  and change the center of gravity of the robot ball  1 . Due to the force of gravity and the inertia of the counterweight  9 , this will cause tilting of the platform  6  and axis of rotation  3  about the pivot axis  17  (see FIG. 3) by providing the necessary counter-rotating force on the drive motors  7  and  8 . Those of ordinary skill in the art will appreciate that, in the position of FIG. 3, rotation of the shafts  11  and  13  of the electric drive motors  7  and  8  will still roll the shell  2  on the ground  23 . However, since the circular portion of the tread  4  contacting the ground is still centered on the axis of rotation  3  but is offset laterally from the central plane of symmetry of the shell  2  perpendicular to this axis  3 , the trajectory of the robot ball  1  will then be semicircular. Therefore, appropriate operation of the servomotor  20  to rotate the shaft  22  and counterweight  9  in either direction will control the direction of movement of the robot ball on the ground  23 . This will enable steering of the robot ball  1 . 
     Just a word to mention that it is within the scope of the present invention to implement other structures of counterweight. 
     Of course, the battery  14  constitutes the source of energy of the robot ball  1 , in particular but not exclusively to supply the motors  7 ,  8  and  20 . However, just a word to point out that use of motors other than electric motors can be contemplated. 
     Inclinometers 
     The robot ball further comprises a pair of inclinometers to detect angular positions of the platform  6  with respect to the horizontal, and more specifically about axes  3  and  17 , respectively. 
     Referring to FIG. 4, the first inclinometer  24  detects tilt of the platform  6  about the axis of rotation  3 . Inclinometer  24  is formed of four mercury switches  241 ,  242 ,  243  and  244  respectively positioned at angles of 15°, 75°, 105° and 165° with respect to the plane of the platform  6 . This arrangement of four mercury switches  241 - 244  will enable detection of eight (8) angular positions of the platform  6  about the axis of rotation  3 : 
     horizontal (all the mercury switches  241 - 244  are closed as shown in FIG.  4 ); 
     tilted upwardly (switches  241 - 243  closed and switch  244  open as shown in FIG.  5 ); 
     face upward (switches  241 - 242  closed and switches  243 - 244  open as shown in FIG. 6) 
     reversed upwardly (switch  241  closed and switches  242 - 244  open); 
     reversed (all the mercury switches  241 - 244  open); 
     reversed downwardly (switch  244  closed and switches  241 - 243  open); 
     face downward (switches  243 - 244  closed and switches  241 - 242  open); 
     tilted downwardly (switches  242 - 244  closed and switch  241  open). 
     Also, the mercury switches  241 - 244  will detect an impact between the robot ball  1  and an obstacle since, in such a case, the platform  6  and counterweight  9  will complete a turn about the axis  3 . 
     Reading of the inclinometer  24  will enable the robot ball  1  to break intricate deadlocks unbreakable by conventional wheeled robots. 
     Referring to FIG. 7, the second inclinometer  25  detects tilt of the platform  6  about the pivot axis  17 . Inclinometer  25  is formed of two (2) mercury switches  251  and  252  respectively slightly tilted toward each other. Mercury switches  251  and  252  will detect tilt of the platform  6  and shell  2  toward the left or the right, respectively. The arrangement of two (2) mercury switches  251 - 252  will enable detection of three (3) angular positions of the platform  6  about the pivot axis  17 : 
     horizontal (the mercury switches  251  and  252  are closed as shown in FIG.  7 ); 
     tilted toward the left (switch  252  closed and switch  251  open); and 
     tilted toward the right (switch  251  closed and switch  252  open as shown in FIG.  8 ). 
     The position and inclination of the mercury switch  251  and  252  will also enable detection of spinning of the robot ball  1  about a vertical axis; in this case the two (2) switches will be opened by the produced centrifugal force. 
     Of course, it is within the scope of the present invention to use other types of switches and/or inclinometers, as well as other types of tilt sensors. 
     Obstacle Detector 
     Referring to FIGS. 1 and 9, the top, front portion of the platform  6  is equipped with an obstacle detector  26  designed to detect obstacles such as  27  (FIG.  9 ). 
     The obstacle detector  26  comprises a pair of infrared light-emitting diodes  261  and  262  and an infrared detector  263  such as a phototransistor. 
     In operation, the diodes  261  and  262  will emit infrared light beams such as  28  (FIG.  9 ). Light beam such as  28  will reflect on an obstacle such as  27 , and the reflected light beam such as  29  will reach the infrared detector  263  to thereby detect of the obstacle  27 . Obviously, operation of the obstacle detector  26  requires adequate transparency of the shell  2  which, for example, can be made of transparent plastic material. 
     Of course, the use of other types of obstacle detector could be contemplated without departing from the spirit of the present invention. 
     Controller 
     As illustrated in FIG. 9, the robot ball  1  is further provided with an electronic controller  30 . Of course, the controller  30  is supplied with electric energy from the battery  14 . 
     The architecture of the electronic controller  30  is illustrated, by way of a schematic block diagram, in FIG.  10 . In the following example, an application of the robot ball  1  as a toy will be considered although many other applications of the robot ball  1  could be contemplated. 
     As illustrated in FIG. 10, the controller  30  comprises behaviour modules  101 - 105  responsive to the signals from the inclinometers  24  and  25  and the obstacle detector  26  to control the above defined driving system to: 
     move forward or backward the robot ball  1  (module  101 ), while controlling the speed of rotation of the drive motors  7  and  8  in response to signals from the inclinometer  24  to keep the platform  6  as horizontal as possible; 
     direct the robot ball  1  along a straight line by keeping the platform  6  as horizontal as possible through the servomotor  20  and with the help of the inclinometer  25  (module  102 ); 
     turn left or right by tilting the platform  6  about pivot axis  17  in either direction through the servomotor  20  and in relation to the signal from the inclinometer  25  (module  103 ); 
     deactivate the drive motors  7  and  8  when the inclinometer  24  detects that the platform  6  is reversed in order to return this platform to its normal position (module  105 ); 
     avoid obstacles by turning, deactivating the drive motors  7  and  8 , or reversing the direction of rotation of these drive motors  7  and  8  in response to an obstacle-indicative signal from the obstacle detector  26  (module  104 ); 
     etc. 
     The controller  30  further comprises a behaviour module  106  to enable the robot ball  1  to play music and/or sing and a behaviour module  107  to enable the robot ball  1  to speak. 
     The behaviour modules  101 - 107  are shown in FIG. 10 according to an order of priority. More specifically, the degree of priority of the various modules  101 - 107  increases from bottom to top in the control of: 
     the speed of rotation of the drive motors  7  and  8 ; 
     the rotation of the counterweight  9  about pivot axis  17 ; 
     a buzzer  108  for producing the music, songs and/or sound effects; and 
     a speech synthesiser  109  for producing vocal messages; 
     taking into consideration whether the modules are activated and the associated detection conditions (inclinometers  24  and  25  and detector  26 ) are met. 
     Activation of the behaviour modules  101 - 107  is determined and controlled by the goal management module  110  through the links  111 . Also, activation of the parameters of configuration of the behaviour modules  106  and  107  is determined and controlled by an internal analyser module  112 . Activation of the behaviour modules  101 - 107  as well as the parameters of configuration of the behaviour modules  106  and  107  is carried out on the basis of internal variables called “motives” (see module  113 ). These motives are variables having a level of excitation varying between 0% and 100% and a level of activation of 0 or 1. The level of activation is determined by the level of excitation, and indicates whether the behaviour modules are activated or not. The level of excitation examines different factors such as sensors  24 - 26 , behaviour use and influence of the other motives, and add their respective influences in time. 
     For example, in the case of an application of the robot ball as a toy and when the robot ball frequently hits obstacles, the incentives can be AWAKENING, NEED BATTERY RECHARGE, and DISTRESS. 
     In the case of DISTRESS, goal management module  110  and the internal analyser module  112  controls the behaviour module  107  to generate a distress vocal message reproduced through the speech synthesiser  109 . The goal management module  110  also controls the behaviour modules  101 - 105  for example to modify the direction of rotation of the drive motors  7  and  8  and the angular position of the counterweight  9  about axis  17  in an attempt to break the deadlock. If the deadlock has not been broken after a certain period of time, all the behaviour modules are inhibited during a given period of time to allow the robot ball to stabilise before it attempts again to break the deadlock. 
     In the case of NEED BATTERY RECHARGE, goal management module  110  and the internal analyser module  112  controls the behaviour module  107  to generate a vocal message reproduced through the speech synthesiser  109  that the robot ball  1  needs battery recharge. The goal management module  110  also inhibits all the other behaviour modules  101 - 105 . 
     In the case of AWAKENING, goal management module  110  and the internal analyser module  112  controls the behaviour modules  101 - 107  for normal operation of the robot ball  1  as described hereinafter. 
     Obviously, it is within the scope of the present invention to use another architecture of controller capable of fulfilling the same, similar or other functions. 
     States of the Robot Ball 
     States of the robot ball  1  are shown, for the purpose of exemplification only, in FIG.  11 . 
     During AWAKENING (state  120 ), the goal management module  110  controls the behaviour modules  101 - 107  to periodically stop movement of the robot ball  1 . The goal management module  110  then asks for a period of rest (state  121 ) of the robot ball  1  through the internal analyser module  112 , the behaviour module  107  and the speech synthesiser  109 . 
     During the periods of rest of the robot ball  1 , the goal management module  110  asks the child to spin it (state  122 ), to shake it (state  123 ), or to push it (state  124 ) through the internal analyser module  112 , the behaviour module  107  and the speech synthesiser  109 . The goal management module  110  periodically repeats this request. 
     If the sensors  24 - 26  indicate that the child did comply with the request, the goal management module  110  thanks the child through the internal analyser module  112 , the behaviour module  107  and the speech synthesiser  109 . 
     If the sensors  24 - 26  indicate that the child did not correctly respond to the request, the goal management module  110  asks the child to stop through the internal analyser module  112 , the behaviour module  107  and the speech synthesiser  109 . 
     If the child does no comply with the request, the goal management module  110  then indicates through the internal analyser module  112 , the behaviour module  107  and the speech synthesiser  109 , that the robot ball  1  is bored. 
     In the case of a request to spin the robot-ball, the goal management module  110  generates messages related to the rotation of the robot ball through the internal analyser module  112 , the behaviour module  107  and the speech synthesiser  109 : 
     when spinning detected through the centrifugal force applied to the mercury switches  251  and  252  of the inclinometer  25  is fast, the goal management module  110  indicates that the robot ball  1  is dizzy; 
     otherwise, the goal management module  110  asks the child to spin the robot ball  1  again. 
     A given period of time after the robot ball  1  has been spun or shaken, the goal management module  110  reactivates the behaviour modules  101 - 107  and the robot ball  1  moves again until the AWAKENING cycle is completed. After the robot ball  1  has been pushed, the goal management module  110  reactivates the behaviour modules  101 - 107  and the robot ball  1  moves again until the AWAKENING cycle is completed. The goal management module  110  then deactivates the behaviour modules to inactivate the robot ball  1  during a certain period of time before it returns to the AWAKENING mode. 
     The periods of occurrence of the states of the robot ball  1  are determined by means of fixed increments or randomly generated levels so as to create no automatism. 
     Other messages can be generated by the goal management module  110  through the internal analyser module  112 , the behaviour module  107  and the speech synthesiser  109  in response to particular events detected by the modules  25 - 26 . Examples of such messages are given below: 
     
       
         
               
               
             
           
               
                   
               
               
                 Message 
                 Event 
               
               
                   
               
             
             
               
                 Oups! 
                 The platform 6 has reversed 
               
               
                 Help! 
                 The platform 6 often reverses 
               
               
                 Weeeeee! 
                 The robot ball is spun, upon request 
               
               
                 Thank you 
                 The robot ball 1 has been recharged or the child 
               
               
                   
                 has complied with one request 
               
               
                 Stop, please 
                 The robot ball 1 is displaced during a rest 
               
               
                   
                 period 
               
               
                 I&#39;m bored 
                 The child does not comply with the requests of 
               
               
                   
                 the robot ball 1 
               
               
                 Push me gently, please 
                 During a rest period, the robot ball 1 asks the 
               
               
                   
                 child to push it to move again 
               
               
                 Spin me, please 
                 During a rest period, the robot ball 1 asks the 
               
               
                   
                 child to spin it 
               
               
                 Shake me gently, 
                 During a rest period, the robot ball asks the 
               
               
                 please 
                 child to shake it gently 
               
               
                 I feel dizzy 
                 The child spun the robot ball 
               
               
                 Charge me, please 
                 The robot ball needs to be charged 
               
               
                 See you 
                 The AWAKENING cycle is over 
               
               
                 Hello, how are you 
                 The AWAKENING cycle begins 
               
               
                 (Name of the child) 
                 Name of the child used in certain messages in 
               
               
                   
                 order to personalize these messages 
               
               
                   
               
             
          
         
       
     
     Obviously, a system for recording the name of the child must be implemented if the last feature of the above table is to be used. 
     It is also within the scope of the present invention to implement a voice recognition system (block  125  of FIG. 10) to enable the robot ball  1  to respond to vocal instructions. It is further within the scope of the present invention to implement an inductive tactile system (block  125  of FIG. 10) to enable the robot ball  1  to respond to tactile stimuli. 
     Just a word to mention that it would be possible to implement a system enabling parents to modify or add certain messages to personalize the robot ball  1  by: 
     as mentioned earlier in the description, recording the name of the child; 
     store vocal messages that the robot ball  1  will periodically repeat to the child at various frequencies; 
     enabling the robot ball to recognize only vocal commands from a particular child; 
     etc. 
     These features are interesting since they will enable the use of the robot for educative and even therapeutic purposes, for example to help an autistic child to open himself to the exterior world. 
     Although an application of the robot ball  1  as a toy has been described as preferred embodiment in the foregoing description, it is also intended to develop other versions of the robot ball  1  using the same concept but adapted to other applications such as exploration, on-site measurements, inspection of conduits, landmine detection, over water, etc. 
     The robot ball  1  presents, amongst others, the following advantages: 
     different trajectories of movement can be implemented in relation to the program of the controller and detection through various sensors such as  24 - 26 ; 
     a robot ball  1  encapsulated into a shell  2  is capable of displacing naturally in its environment with lower risks to fall into a deadlock; 
     the shell  2  is impervious and protect the robot ball from dust and debris; 
     in the application as a toy, the shell  2  protects the robot ball from shocks and improper use by the children; 
     the shape of the shell  2  corresponds to the shape of a ball; 
     the trajectories of the robot ball  1  generated by the controller can be easily reconfigured through simple programming; 
     interactive use of the robot ball  1  is possible through vocal messages; 
     implementation of an inductive tactile system is possible; 
     etc. 
     Although the present invention has been described hereinabove by way of a preferred embodiment thereof, this embodiment can be modified at will, within the scope of the appended claims, without departing from the spirit and nature of the subject invention.