Abstract:
A robot apparatus generating behavior or performing actions. The robot apparatus comprises a parameter generator for generating one or more parameters of an emotion model defining a predetermined emotion and one or more parameters of an instinct model defining a predetermined instinct. An input signal representative of an external stimulus and an input signal representative of an internal stimulus are provided to the robot apparatus. One or more semantic contents are determined in accordance with the detected input signals, and at least one of the emotion model parameters and the instinct model parameters are changed based upon the semantic content. A behavior model is then generated to generate behavior or actions in accordance with the emotion parameters of the emotion model and the instinct parameters of the instinct model.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation-In-Part of application Ser. No. 09/457,318 filed Dec. 8, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a robot apparatus, and more particularly it is suitably applied to a pet robot constructed as, for example, a four-footed animal performing autonomous, life-like actions. 
     2. Description of the Related Art 
     Heretofore, a four-footed walking pet robot has been proposed and developed which performs actions in predetermined ways in response to commands from a user or depending upon local environmental conditions. Such a pet robot resembles a four-footed animal often kept in the house, such as a dog or cat. A dog-like pet robot, for example, is designed to always lie down upon receiving a command “lie down” from the user, or to always give a “hand” (front paw ) when the user stretches his or her hand to just under the robot&#39;s nose. 
     However, such a conventional pet robot performs actions only in predetermined ways in accordance with commands from the user or local environmental conditions. Thus, the conventional pet robot does not act as an autonomous robot capable of determining, and acting upon an action by itself. In other words, the conventional pet robot does not behave as a genuine pet, and therefore has a difficulty in fully satisfying a user&#39;s demand of obtaining a pet robot that functions as closely as possible to a genuine pet. 
     OBJECTS OF THE INVENTION 
     Accordingly, it is an object of the invention to provide a robot apparatus capable of autonomously behaving in natural ways. 
     It is another object of the invention to provide a robot apparatus capable of learning various behaviors in response to both external and internal environmental conditions. 
     It is a further object of the invention to provide a robot apparatus in which the behavior of the robot apparatus is determined in accordance with an emotion model and an instinct model. 
     An additional object of the invention is to provide a pet robot apparatus that behaves in a manner most similar to the behavior of an actual pet. 
     Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification and drawings. 
     SUMMARY OF THE INVENTION 
     To achieve the above objects of the invention, a robot apparatus is provided. The robot apparatus behaves in accordance with input information supplied to the robot apparatus. The robot apparatus includes an emotion model and an instinct model, these models changing in accordance with various stimuli. A next action to be performed by the robot apparatus is determined by changing the emotion model and the instinct model based upon the input information, and the interpretation of this input information. Because the robot apparatus constructed in accordance with the invention includes the motion and instinct models linked to its actions, and because the robot apparatus decides the next action to be taken thereby by changing the emotion and instinct models based upon the input information, the robot apparatus can autonomously behave in accordance with the present emotional and instinctive states created thereby in accordance with the historical actions thereof. 
     Also in accordance with the invention, a robot apparatus behaving in accordance with input information supplied to the robot apparatus is provided. The robot apparatus includes an operating state deciding unit for deciding a next operating state to be changed to from a current operating state based upon the current operating state, a history of various input information having been previously supplied in succession to the robot apparatus immediately prior to the current input information, and the current input information. Therefore, the robot apparatus in accordance with the invention can autonomously behave in accordance with the emotional and instinctive states it created in accordance with the historical actions thereof. 
     Further, in accordance with the invention, a robot apparatus is provided that determines a next posture to be taken based upon the current physical configuration, possible future configurations, and the input information. The robot apparatus includes a posture transition unit for transitioning the current posture of the robot apparatus to a next posture in accordance with the input information via a predetermined route of steps of the mechanisms of the robot apparatus. Because the current posture of the robot apparatus is transitioned to the next posture in accordance with the input information via a predetermined route, the robot apparatus can avoid being forced to take an impossible or otherwise undesirable posture, or from falling down during the transition. 
     The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the apparatus embodying features of construction, combinations of elements and arrangement of parts that are adapted to effect such steps, all as exemplified in the following detailed disclosure, and the scope of the invention will be indicated in the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the invention, reference is made to the following description and accompanying drawings, in which: 
     FIG. 1 is a schematic view depicting a first embodiment of a pet robot constructed in accordance with the invention; 
     FIG. 2 is a block diagram depicting a circuit configuration of the pet robot of FIG. 1; 
     FIG. 3 is a block diagram depicting the flow of data processing in a controller of FIG. 2; 
     FIG. 4 is a diagram depicting the flow of data processing executed by an emotion model unit and an instinct model unit, and the flow of information therebetween; 
     FIG. 5 is a diagram showing data processing executed by the emotion model unit of FIG. 4; 
     FIG. 6 is a diagram showing data processing executed by the emotion model unit of FIG. 5 in accordance with an alternative embodiment of the invention; 
     FIG. 7A is a state transition diagram depicting the transition of the robot apparatus from state to state in a behavior deciding mechanism; 
     FIG. 7B is a portion of the state transition diagram of FIG. 7A depicting the weighting of transition arcs; 
     FIG. 8 is a posture transition diagram for determining a posture deciding mechanism; 
     FIG. 9 is an additional posture transition diagram depicting a neutral and a fall down state; and 
     FIG. 10 depicts the movement of the pet robot in accordance with a single set of instructions governing all parts of the pet robot, or in accordance with a plurality of sets of instructions, one for each part of the pet robot. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring first to FIG. 1, a first, preferred embodiment of the invention will be described. 
     Construction of a Pet Robot 
     In FIG. 1, a pet robot  1  comprises a head portion  2 , a body portion  3 , leg portions  4 A- 4 D, and a tail portion  5 . These components are appropriately coupled into the form of a pet as desired. Head portion  2 , leg portions  4 A- 4 D and tail portion  5  are moved relative to body portion  3  so that the pet robot behaves like a genuine four-footed animal. While FIG. 1 depicts a particular structure of a pet robot, other configurations, including both minor and major modifications, may be employed. 
     Head portion  2  includes an image detecting unit  10 , corresponding to eyes of a live pet, and comprising, e.g., a CCD (Charge Coupled Device) camera for detecting an image. A microphone  11 , corresponding to an ear of a live pet, receives and hears various sounds, such as a voice. A speaker  12 , corresponding to a mouth of a live pet, generates a voice. Each of these components is attached to head portion  2  at respective predetermined positions. Head portion  2  further includes a remote controller command receiver  13  for receiving commands transmitted from a user via a remote controller (not shown). A touch sensor  14  is also provided for detecting the contact of, for example, a user&#39;s hand upon head portion  2 . 
     In a preferred embodiment, pet robot  1  is provided with an image display unit  15  including both red and green LEDs, indicative of anger and pleasure, respectively. Body portion  3  includes a battery  21  attached to a position corresponding to the belly of a live pet. An electronic circuit (not shown) is installed within body portion  3  for controlling the operation of pet robot  1 . 
     Actuators  23 A- 23 N are provided respectively at the articulation joints of legs  4 A- 4 D, at joints between legs  4 A- 4 D and body portion  3 , at a joint between body portion  3  and head portion  2 , at a joint between body portion  3  and tail portion  5 , etc. Actuators  23 A- 23 N are driven under the control of the electronic circuit installed within body portion  3 . Pet robot  1  is able to move as a genuine four-footed animal by driving actuators  23 A- 23 N in such a manner that head portion  2  swings vertically or horizontally, tail portion  5  wags, and legs  4 A-D move to make the pet robot walk or run, as desired. 
     The circuit configuration depicting the electrical structure and make-up of pet robot  1  will now be described, making reference to FIG.  2 . Head portion  2  includes a command receiving unit  30 , which is made up of microphone  11  and remote-controller command receiver  13 ; an external sensor  31 , which is made up of image detecting unit  10 , touch sensor  14  and a position sensing device  310 ; speaker  12 ; and image display unit  15  including the LEDs as noted above. Body portion  3  includes battery  21  attached to its lower surface, and also includes therein a controller  32  for controlling the operation of the pet robot  1 . An internal sensor  35  is also provided in body portion  3 . Internal sensor  35  is made up of a battery sensor  33  for detecting the remaining charge of battery  21  and a heat sensor  34  for detecting the head generated inside pet robot  1 . Further, the actuators  23 A- 23 N are provided in the noted predetermined positions of pet robot  1 , and are controlled by controller  32  as necessary. 
     During use, command receiving unit  30  receives commands, such as “walk”, “lie down”, etc., given from the user to pet robot  1 . Command receiving unit  30  is made up of remote-controller command receiver  13  and microphone  11 , and therefore can receive a command from a user via remote control, or via sound or voice. When a desired command is input to the remote controller (not shown) by manipulation of the user, the remote controller transmits an infrared ray in accordance with the input command to remote-controller command receiver  13 . Upon receiving the infrared ray, remote-controller command receiver  13  produces a reception signal S 1 A and forwards this signal to controller  32 . When the user utters a desired vocal command, microphone  11  receives the uttered vocal command from the user, produces a voice signal S 1 B, and then forwards this signal to controller  32 . Thus, command receiving unit  30  produces command signals S 1  (reception signal S 1 A and voice signal S 1 B) in accordance with commands given to pet robot  1  from the user. The command signals S 1  are then forwarded to controller  32 . 
     Touch sensor  14  of external sensor  31  detects actions applied to pet robot  1  from the user such as “stroking” and “striking”. When the user performs a desired action by touching touch sensor  14 , touch sensor  14  produces a contact detection signal S 2 A depending on the applied action, and forwards this signal to the controller  32 . 
     Image detecting unit  10  of external sensor  31  queries the external environment of pet robot  1  and detects information indicative thereof, such as “dark” and “there is a favorite toy”, or motions of other pet robots such as “another pet robot is running”. To this end, image detecting unit  10  detects images in the surroundings of pet robot  1  and transmits a resulting image signal S 2 B to controller  32 . 
     Position sensing device similarly detects the current position of the pet robot, and generates sensing signal S 2 C, depending on the position. Thus, external sensor  31  produces external information signals S 2  (contact detection signal S 2 A, the image signal S 2 B and position sensing signal S 2 C) in accordance with external information collected from the exterior of pet robot  1 . External information signals S 2  are then forwarded to the controller  32 . 
     Internal sensor  35  detects the inner status of pet robot  1  itself, such as “hungry” meaning that the battery charge is low, and “hot” meaning that it is too hot inside the robot. Internal sensor  35  is therefore made up of battery sensor  33  and heat sensor  34 . Battery sensor  33  detects the remaining charge of battery  21 , used for supplying power to various circuits in the pet robot  1 , and transmits a resulting battery-charge detection signal S 3 A to controller  32 . Heat sensor  34  detects the head generated inside pet robot  1 , and transmits a resulting heat detection signal S 3 B to controller  32 . Internal sensor  35  therefore produces internal information signals S 3  (battery-charge detection signal S 3 A and heat detection signal S 3 B) in accordance with detected information describing internal conditions of pet robot  1 . These internal information signals S 3  are then supplied to controller  32 . 
     Controller  32  produces control signals S 5 A-S 5 N for driving actuators  23 A- 23 N based upon command signals S 1  supplied from command receiving unit  30 , external information signals S 2  supplied from external sensor  31 , and internal information signals S 3  supplied from internal sensor  35 . Control signals S 5 A-S 5 N are transmitted respectively to actuators  23 A- 23 N for driving them, whereupon the pet robot  1  operates in an autonomous manner. 
     Controller  32  also produces, as required, a voice signal S 10  and an image signal S 11  which are output to the exterior of pet robot  1 . The voice signal S 10  is output to the exterior via speaker  12 , and the image signal S 11  is transmitted to LED unit  15  to display necessary information to the user. 
     Data Processing in Controller 
     Data processing in controller  32  will now be described. Controller  32  executes software data processing of the command signals S 1  supplied from command receiving unit  30 , the external information signals S 2  supplied from external sensor  31 , and the internal information signals S 3  supplied from internal sensor  35  in accordance with a program previously stored in a predetermined memory area. Resulting control signals S 5  are supplied to actuators  23 A- 23 N. 
     As shown in FIG. 3, details of data processing in controller  32  are functionally divided into a model unit  40  that includes processing based upon an instinct model and an emotion model and means for changing each of these emotion or instinct models; a behavior deciding mechanism  41  as a means for determining a next operating state; a posture transition mechanism  42  as a posture transition means and including a speaker  42   a  and an LED unit  42   b ; and a control mechanism  43  for controlling the movement and action of pet robot  1 . The command signals S 1  supplied from exterior sensors, such as remote control command receiver  13  and microphone  11 , the external information signals S 2  supplied from external sensors, such as touch sensor  14 , position sensing device  310  and image recognizing unit  10  of the external sensor, and the internal information signals S 3  supplied from battery sensor  33  and heat sensor  34  are applied to both emotion and instinct model units  40 , and behavior deciding mechanism  41 . 
     As shown in FIG. 4, the emotion and instinct model units  40  include emotion model  50  and an instinct model  51 . Emotion model  50  has a group of basic emotions comprising emotion units  50 A- 50 F that act as a plurality of mutually interdependent emotion models. Instinct model  51  has a group of basic desires comprising desire units  51 A- 51 D that act as a plurality of mutually interdependent instinct models. Of the group of basic emotions, emotion unit  50 A represents “joy”, emotion unit  50 B represents “sadness”, emotion unit  50 C represents “anger”, emotion unit  50 D represents “surprise”, emotion unit  50 E represents “fear”, and emotion unit  50 F represents “discontent”. Each of the emotion units  50 A- 50 F indicates a degree of the particular emotion with intensity varying on a scale from 0 to 100 levels in a preferred embodiment. 
     As is shown in FIG. 4, information signals S 1 , S 2  and S 3  are forwarded to emotion model unit  50 , and more specifically to each emotion unit  50 A- 50 F (arrows to each individual emotion unit not being shown for clarity). Based upon these input values, a relative level of each emotion is determined. In addition to taking into account the input signals, each emotion unit also considers the levels of other emotion units. For example, some of the emotions have a positive correlation with other of the emotions, while some of the emotions have a negative condition with other of the emotions. Thus, for example, if discontent level  50 F is determined to be high, anger level  50 C will also be high, while joy level  50 A will be low. 
     Furthermore, each input signal S 1 , S 2 , S 3  is considered differently by each emotion unit. Thus, the internal sensor values S 3  might be considered more importantly by discontent unit  50 F than surprise unit  50 D. Thus, each emotion unit considers the supplied input signals, the levels of the other emotion units, its prior output level value, as well as the levels of the various instinct units (as will be explained below) to determine a current value, and each of these values are combined and output to form a signal S 10 . The values and intensities of these emotions change from moment to moment in accordance with command signals S 1 , external information signals S 2 , and internal information signals S 3  supplied to them, and other noted values. Thus, emotion model unit  50  represents time-dependent changes of the emotions in a modeling manner; namely, it expresses an emotional state of the pet robot  1  by combining the momentarily varying intensities of outputs from the emotion units  50 A- 50 F with each other to form part of signal S 10 . 
     Instinct model  51  has a group of basic instincts comprising instinct units  51 A- 51 D which act as a plurality of mutually interdependent instinct models of the group of basic instincts. Instinct unit  51  A represents “love”, instinct unit  51 B represents “search”, instinct unit  51 C represents a “desire for movement or exercise” and instinct unit  51 D represents appetite, or a desire for “recharge”. As with emotion units  50 A- 50 F, each of the instinct units  51 A- 51 D indicates a degree of the desire with intensity varying from 0 to 100 levels in a preferred embodiment. 
     As is further shown in FIG. 4, information signals S 1 , S 2  and S 3  are forwarded to instinct model unit  51 , and more specifically to each instinct unit  51 A- 51 D (arrows to each individual instinct unit not being shown for clarity). Based upon these input values, a relative level for each instinct is determined. In addition to taking into account the input signals, the instinct units also consider the levels of the other instincts. For example, some of the instinct have a positive correlation with other of the instincts, while some of the instincts have a negative correlation with other o the instincts. Thus, for example, if recharge level  51 D is high, search level  51 B may also be high, while love level  51 A may be low, and move/exercise level  51 C might also be low. 
     Furthermore, each input signal S 1 , S 2 , S 3  is considered differently by each instinct unit. Thus, the internal sensor values S 3  might be considered more importantly by recharge instinct unit  51 D than love instinct unit  51 A. Each instinct unit therefore considers input signals, the levels of the other instinct units, its prior level, as well as the levels of the various emotion levels to determine a current value. 
     Thus, as is further shown at FIG. 4, each of the instinct units considers the level of the emotion units, and vice versa. For example, a high recharge level  51 D will also likely result in high anger level  50 C and discontent level  50 F, and a low joy level  50 A. More than one emotion or instinct may therefore be present, but in different levels. Furthermore, by each instinct or emotion unit considering its prior level, erratic behavior can be avoided. 
     Therefore, changes in the intensity of instinct take place from moment to moment in accordance with command signals S 1 , external information signals S 2  and internal information signals S 3  supplied to them. Instinct model unit  51  represents time-dependent changes of the instinct desires in a modeling manner; namely, it expresses an instinctive state of the pet robot  1  by combining the momentarily varying intensities of outputs from instinct units  51 A- 51 D with each other. 
     In general, the emotion model unit is more concerned with external stimuli, and the instinct model unit is more concerned with internal stimuli. Thus, while the emotion model will pay most attention to S 1 , moderate attention to S 2 , and less attention to S 3 , the instinct will pay greater attention to S 3 , moderate attention to S 2  and less attention to S 1 . However, all of the inputs and other factors noted above are considered for each emotion or instinct unit. 
     After a consideration of all relevant factors, the emotion and instinct model units  50  and  51  change the intensities of respective outputs from the individual emotion model units  50 A- 50 F and the individual instinct model units  51 A- 51 D. Then, emotion and instinct model unit  40  combines the varying intensities of outputs from the emotion units  50 A- 50 F from the instinct units  51 A- 51 C to decide the next emotional and instinctive state of the pet robot. The decided emotional and instinctive state is transmitted as state information S 10  to behavior deciding mechanism  41 . 
     Further, in one embodiment of the invention, in addition to considering all of the inputs noted above to determine an instinct or emotion unit level value, the emotion and instinct model units  40  couple desired ones of the emotion model units  50 A- 50 F in a mutually inhibiting or stimulating manner. Thus, when the intensity of output from one of the coupled emotion units is changed, the intensity of output from the other emotion unit is also changed correspondingly. This contributes to realizing the pet robot  1  expressing natural emotions. This procedure may also be followed concerning the instinct model units. 
     More specifically, as shown in FIG. 5, the emotion model unit  50  couples the “joy” emotion unit  50 A and the “sadness” emotion unit  50 B in a mutually inhibiting manner such that when the pet robot is praised by the user, the intensity of output from the “joy” emotion unit  50 A is increased and the intensity of output from the “sadness” emotion unit  50 B is reduced correspondingly which cause the intensity level output from the “joy” emotion unit  50 A to increase and the intensity level output from the “sadness” emotion unit  50 B to be changed to reduce at the same time. Also, with the emotion model unit  50  coupling both emotion model units  50 A and  50 B, when the intensity level output from the “sadness” emotion unit  50 B is increased, the intensity level output from the “joy” emotion unit  50 A is reduced correspondingly with an increase in the intensity level output from the “sadness” emotion unit  50 B. 
     While only a small number of correlations are shown in FIG. 5, indeed each emotion (or instinct) unit can include one or more of such correlations. The use of such correlations, in addition to the considerations noted above for determining unit output levels, can further insure natural actions by the pet robot. 
     Returning to FIG. 3, the emotion and instinct model units  40  are supplied with historical behavior information S  12  indicating the nature of current or past action of pet robot  1  itself, such as “it has been walking for a long time”, from behavior deciding mechanism  41 . Thus, in addition to considering the past intensities of the emotion or instinct model units, the current behavior of the pet robot is considered when deciding the next behavior to be invoked. Depending on e action of pet robot  1  indicated by this historical behavior information S 12 , therefore, the emotion and instinct model unit  40  may produce different state information S 10  even if input information S 1 -S 3  does not change, and also aids in guarding against erratic or unexpected behavior. 
     As is shown in FIG. 6, in an alternative embodiment, rather than having each emotion or instinct unit perform multiple calculations, emotion model unit  50  includes intensity increasing/reducing (+/−) units  55 A- 55 F which are disposed upstream of emotion model units  50 A- 50 F, respectively. (Instinct model unit  51  would include similar structure, but is not shown). These intensity (+/−) units perform the function of increasing and reducing the intensities of the output values from emotion model units  50 A- 50 F based on the historical behavior information S 12  indicating the current and past action of pet robot  1 , and input information signals S 1 -S 3  provided to each intensity (+/−) unit. The intensities of the output values from emotion units  50 A- 50 F are increased or reduced in accordance with intensity information S 14 A-S 14 F output from intensity increasing/reducing units  55 A- 55 F, respectively. 
     For example, when the pet robot  1  greets the user and the user strokes the head of the pet robot  1 , i.e., when the historical behavior information S 12  indicates “pet robot  1  greets the user” and the input information S 1 -S 3  indicates “user strokes the head of pet robot  1 ”, this information is applied to the intensity increasing/reducing unit  55 A and the emotion model unit  50  increases the intensity of the value output from the “joy” emotion model unit  50 A. However, for example, when the user strokes the head of pet robot  1  while pet robot  1  is doing some work or task, i.e., when the historical behavior information S 12  indicates “pet robot  1  is doing some work” and the input information S 1 -S 3  indicates “user strokes the head of pet robot  1 ”, this information is applied to the intensity (+/−) function  55 A, the emotion model unit  50  may not change the intensity of output from the “delight” emotion unit  50 A. 
     Thus, the emotion model unit  50  decides the intensities of respective outputs from emotion model units  50 A- 50 F while referring to not only the input information S 1 -S 3  but also the historical behavior information S 12  indicating the current or past action of pet robot  1 . Accordingly, for example, when the user strokes the head of the pet robot  1  while pet robot  1  is doing some task, it is possible to prevent an increase in the intensity of the output value from the “joy” emotion unit  50 A and to avoid pet robot  1  from expressing an unnatural emotion of delight. Similarly, for the instinct units  51 A- 51 D, instinct model unit  51  also increases and reduces the intensities of respective outputs from the instinct units  51 A-S 1 D in accordance not only with input information S 1 -S 3 , but also historical behavior information S 12  supplied thereto. 
     As described above, upon receiving input information S 1 -S 3  and historical behavior information S 12 , intensity increasing/reducing functions  55 A- 55 F produce an output value intensity information S 14 A-S 14 F depending on a plurality of preset parameters that may be learned with use, or may have a preset value. By presetting the parameters to different values from one pet robot to another, or by allowing the pet robot to “learn”, i.e. allowing the parameters to be modified based upon human responses to various actions taken by the pet robot, each pet robot can be given individual characteristics, e.g., one pet robot being irritable and another pet robot being cheerful. This learning feature is also applicable to the prior embodiment in which the emotion and instinct model units change without additional modification units. 
     Returning once again to FIG. 3, behavior deciding mechanism  41  decides a next action to be taken by the pet robot based on input information S 14 , including command signals S 1 , external information signals S 2 , internal information signals S 3 , emotion and instinct state information S 10 , and historical behavior information S 12 . Once the next action to be performed has been decided, behavior deciding mechanism  41  transmits the contents of the decided action, as action command information S 16 , to posture transition mechanism  42 , speaker  42   a  and LED  42   b.    
     More specifically, as shown in FIG. 7A, behavior deciding mechanism  41  employs an algorithm called a finite automation  57  having a finite number of states. Each of these states represents a possible behavior by the pet robot. While a number of states are shown in FIG. 7A, these are only by way of example. Any desired number of states could exist in such a finite automation in the pet robot. The pet robot moves from the current state to the next state based on both the currently supplied input information S 14  and the current state, thereby deciding the next action. Thus, behavior deciding mechanism  41  transitions from one state to either the same, or another state each time input information S 14  is supplied. The next action of the pet robot is thus determined depending on the transitioned to behavior state. The next action of the pet robot is determined by referring to not only the current input information S 14  and the past input information S 12 , but also utilizing a state transition table such as the (simplified) table of FIG.  7 A. 
     As is shown in FIG. 7A, a plurality of possible states are shown. These include state ST 0 , where the pet robot is dancing. State ST 1 , where the pet robot is running after a ball, state ST 2 , where the robot is sleeping, state ST 3 , where the pet robot is sitting, state ST 4 , where the pet robot is standing, and state ST 5 , where the pet robot is also standing, but in a manner different from that of step ST 4 . As is further shown in FIG. 7A, each possible state includes a number of arcs leading to and from that state. For example, ST 0  includes a first arc P 00 , from and to ST 0  (forming a loop), a second arc P 01  from ST 0  to ST 1 , a third arc P 10  from St 1  to ST 0 , and a fourth arc P 02  from ST 0  to ST 2 . The number of arcs shown is for example only. Any number of arcs may be present to or from any particular state. Each state includes similar arcs, as shown. No state comprises a dead-end, each having at least one arc from it to another state. 
     Each arc represents a possible state transition for the pet robot. Thus, a dancing pet robot has three possible transitions (in the example of FIG.  7 A). A first transition along arc P 00  is to continue dancing. A second possible transition along arc P 01  is to begin running after a ball. A third possible transition along arc P 02  is for the pet robot to begin sleeping. Each of the states also includes similar possible transition arcs, none of the arcs forming a dead end. The pet robot is able to transition from state to state along any of the indicated arcs. However, while the pet robot may transition along any of the indicated arcs, the likelihood, or probability of the pet transitioning to one arc, as opposed to a different arc may not be the same. Thus, in FIG. 7A, when dancing, the pet robot might be most likely to continue dancing (arc P 00 ), moderately likely to transition to running after the ball (arc P 01 ), and is least likely to go to sleep (arc P 02 ). 
     Referring to FIG. 7B, a probability weighting transition diagram for transitioning from state ST 0  is shown. In FIG. 7B, each possible transition arc P 00 , P 01 , P 02  includes a respective probability weighting value W 00 , W 01 , W 02 . It is these weighting values that indicate the likelihood of a particular transition will be made along a particular arc. As noted above, if arc P 00  is to be most likely, arc P 01  is to be moderately likely and arc P 02  is to be least likely, a possible weighting scheme might include W 00 =0.70; W 01 =0.25; W 02 =0.05. Because the pet robot must make some transition, the weighting values leaving any node must sum to 1. Because the possible transitions are determined based upon probabilities, a more realistic acting pet robot can be provided where the sequence of states or actions is not always the same. 
     In addition to providing weighted probabilities of transition, in accordance with the invention, it is possible to change the weighting factors based upon any desired factors. For example, if the previously noted weighting factors are used, and the pet robot is dancing for a long time, the weighting factor for transitioning to sleeping (arc P 02 , W 02 ) may be raised to indicate that the pet robot is tired, and the weightings for W 00  and W 01  could be reduced. It is therefore possible to alter the likelihood of possible future actions. It is this weighting system that allows for the pet robot to learn. For example, if upon retrieving a ball the robot receives praise from a user, the pet robot will increase the weighting value of any arc leading to the “running after ball” state. Thus, when the pet robot receives an input signal that a ball is present, the pet robot will be more likely to chase the ball to receive the expected praise. This process can be performed for any action, and can also be performed with scolding to reduce the likelihood of a particular action. 
     In accordance with the invention, it is the output value of the emotion and instinct model units that dictate the weighting values for each of the arcs. Therefore, if the joy output value is increased, all arcs leading to the dancing state of the pet robot might have their weightings increased, therefore increasing the chances that the pet robot will next dance. In accordance with the current determined emotional and instinctual state, the weighting probabilities for moving among the available states can be set. The pet robot will therefore act more naturally, and in accordance with both internal and external stimuli. 
     Upon detecting a predetermined trigger, behavior deciding mechanism  41  effects transition from a current state to a next state. Concretely, a trigger is provided by, for example, the fact that a period of time during which the action in the current state continues has reached a certain value, a particular input information S 14  is applied, or the intensity of an output value from one or more of emotion units  50 A- 50 F or instinct units  51 A- 51 D has exceeded a predetermined threshold. 
     Based on the intensity of the output values from the emotion units  50 A- 50 F and instinct units  51 A- 51 C, the arc probability weightings are set. Thereafter, in accordance with this generated probability state transition model, behavior deciding mechanism  41  determines the state to be transitioned to next. In other words, even with the same command signals S 1 , S 2 , S 3  applied to the pet robot, for example, behavior deciding mechanism  41  effects transition to the different states depending additionally upon the intensities of output values from emotion units  50 A- 50 F and instinct units  51 A- 51 D, and with some amount of pseudo-randomness for selecting the transition arc to follow after the probability weightings are adjusted. 
     Accordingly, for example, upon detecting that the user&#39;s hand is stretched to just under the pet robot&#39;s nose, based upon external information signals  52 , and if it is determined that the intensity of the output value from “anger” emotion model unit  50 C is output value of low and that the intensity of recharge instinct model unit  50 D is low (the pet robot is not hungry), indicating that the battery voltage is not lower than a predetermined threshold, behavior deciding mechanism  41  adjusts the weighting of the various arcs so that the pet robot is more likely to “give the hand” in response to the user&#39;s hand being stretched to just under the pet robot&#39;s nose. While the chance of this response is increased, the pet robot might still perform a different action. Once the action has actually been selected, it is then transmitted to posture transition mechanism  42 . 
     Also, for example, upon detecting that the user&#39;s hand is stretched to just under the pet robot&#39;s noise, based upon external information signals S 2 , that the intensity of the output value from “anger” emotion model unit  50 C is low and that the intensity of the output value of recharge instinct model unit  50 D is high (the pet robot is hungry), indicating that the battery voltage is lower than the predetermined threshold, behavior deciding mechanism  41  adjusts the weighting of the various transition arcs so that the pet robot is more likely to “lick the user&#39;s hand”. Of course, as noted above, the pet robot can still follow another course of action in accordance with one of the other transition arcs. Once an action has been actually selected, it is transmitted to posture transition mechanism  42 . 
     Moreover, in accordance with the intensity of the output values from one or more of emotion units  50 A- 50 F or instinct units  51 A- 51 C, behavior deciding mechanism  41  additionally determines the magnitude of one or more parameters for the action performed in the transitioned state, e.g., the speed of walking, the stroke and speed of motions of the hand and legs, and the pitch and loudness of sounds uttered. Action command information S 16  is then produced depending on the determined parameters for the action, and is transmitted to posture transition mechanism  42 . 
     Returning once again to FIG. 3, posture transition mechanism  42  produces posture transition signal S 18  for indicating a desired transition from a current posture to a next posture. This posture transition information is generated based on behavior command information S 16  supplied from behavior deciding mechanism  41 . This posture transition information S 18  is then forwarded to control mechanism  43 . The next posture to be transitioned to from the current state is therefore decided. The actual movements to be made from the current state to the next state are then determined depending on physical features of pet robot  1  such as the shapes and weights of the body, hands and legs, including possible joint movements between them, and also based on the mechanism of actuators  24 A- 23 N such as the directions and angles in and over which the joints can be bent. 
     The available postures are grouped into postures capable of being directly transitioned to from the current state and postures incapable of being directly transitioned to from the current state. For example, as is shown in FIG. 8, pet robot  1  can directly transition from a posture node ND 1  in which the pet robot is lying sprawled out to a posture node ND 2  in which the pet robot is lying down, but cannot directly transition from posture node ND 1  in which the pet robot is lying sprawled to a posture node ND 3  in which the pet robot is standing up. The latter transition from posture node ND 1  to posture node ND 3  requires a two-step motion. A first step of transitioning from node ND 1  to ND 2  by drawing the hands and legs near the body to take the posture at node ND 2  of lying down is implemented. A second step of transitioning from node ND 2  to ND 3  by standing up from the lying down posture is then implemented. Because the transition between posture nodes must follow predetermined steps, the taking of postures which the pet robot cannot safely take can be avoided. For example, pet robot  1  turns over easily when attempting to raise both the hands for cheering from the stand-up posture Therefore, this posture transition would not be an available transition. 
     In view of the above, the postures capable of being directly transitioned to and from are registered beforehand in posture transition mechanism  42 , and form a node posture state diagram such as that shown in FIG. 8 (the actual state diagram for use in pet robot  1  would be far more complicated). Each node in FIG. 8 includes adjacent states into which it can transition and from which it can transition. When behavior command information S 16  supplied from behavior deciding mechanism  41  indicates that the next posture to be transitioned to is a posture capable of being directly transitioned to from the current posture, posture transition mechanism  42  transmits that action command information S 16  to control mechanism  43 . On the other hand, when behavior command information S 16  supplied from behavior deciding mechanism  42  produces posture transition information S 18  for effecting transition to the desired target posture after transition through one or more intermediate postures, there might first be a transition from the current posture to another intermediate posture capable of being directly transitioned to from the current posture, and thereafter a second transition from the intermediate posture to the final desired posture that can be transitioned to from the intermediate posture. This generated posture transition information S 18  is then forwarded to control mechanism  43 . By employing such two-step motions, pet robot  1  can avoid taking postures that are unsafe, and can thus avoid moving through an unsafe posture, or from turning over inadvertently because of moving through a posture transition beyond its ability. 
     Therefore, as shown in FIG. 8, in posture transition mechanism  42 , the postures capable of being taken by pet robot  1  are registered beforehand, and the relation between every two postures capable of being transitioned from one to the other are recorded. For example, in FIG. 8 posture transition mechanism  42  employs an algorithm called a directional graph  60  in which the postures capable of being taken by pet robot  1  are represented by nodes ND 1 -ND 5 , as noted above, and every pair of postures capable of being transitioned between nodes ND 1 -ND 5  are coupled by directional arcs a 1 -a 10 . 
     When behavior command information S 16  is supplied from behavior deciding mechanism  41 , posture transition  42  plans such a posture transition schedule that the node ND corresponding to the current posture is coupled to the node ND which is represented by behavior command information S 16  and corresponds to the posture to be taken next by the pet robot. This posture transition schedule may include a route leading from the current node ND to a one or more next nodes ND following the direction indicated by each directional arc “a”, in order to reach the final destination node ND. By recording the nodes ND positioned on a determined best route in order from the current node ND to the desired final node, the pet robot can follow this route quickly and easily. As a result, pet robot  1  can perform the action transition instructed by behavior deciding mechanism  41  while avoiding a dangerous state, or from turning over because of an unsafe temporary posture taken during transition from a current posture to a desired posture. 
     As is further shown in FIG. 8, assuming for example that the current posture corresponds to node ND  2  indicating that the pet robot is in the “lying down” posture, when behavior command information S 16  indicating “sit” is supplied, posture transition mechanism  42  supplies the posture transition information S 18  indicating “sit” to the control mechanism  43 . This is done after a determination by posture transition mechanism  42  that pet robot  1  it is allowed to directly transition from node ND 2  indicating the “lying-down” posture to node ND 5  indicating the “sitting” posture. On the other hand, when behavior command information S 16  indicating “walk” is supplied when the pet robot is currently in the “lying-down” posture, transition mechanism  42  plans a posture transition schedule by determining a route leading from node ND 2  indicating the “lying-down” posture to node ND 4  indicating the “walking” posture. This route results in a path through node ND 3  indicating the “standing” posture. Posture transition mechanism  42  then produces posture transition information S 18  first moving from the “lying-down” posture to the “stand-up” posture, and thereafter from the “stand-up” posture to the “walk” posture. This posture transition information is then followed by the transmission of the produced posture transition information S 18  to control mechanism  43 . 
     While FIG. 8 represents a relatively simple posture transition state diagram, more complicated posture transition state diagrams may be used. A portion of such a diagram is shown in FIG.  9 . This diagram includes a number of posture nodes similar to those of FIG. 8, including sitting, and standing, and also includes additional nodes for sleeping and, a neutral node that will be further described below. The first important difference is that not all of the transition paths include arcs that are two way. Thus, while a pet robot acting according to FIG. 9 can move directly from a standing posture to directly a sleeping posture, the pet robot cannot move from a sleeping posture directly to a standing posture, but rather must move through a sitting posture. This is to avoid undesirable positions during transition, as in FIG. 8, but also employs a realization that certain transitions only generate an undesirable position when moving in a particular direction in the chart. 
     Next, it should be noted that the posture transition arcs of FIG. 9 all refer to and thus describe an action. This action is what is necessary to move from a current posture node to a next posture node. However, while this movement is similar in that which would be required in FIG. 8, movement between two posture nodes is not the only type of possible action. Specifically, self-referential actions are possible when a beginning node and next node are the same. If a posture transition arc only defined transition between posture nodes, such a self-referential arc would act as a timing delay. However, because these arcs can define actions, the self-referential arcs of FIG. 9 define actions such as “begging” while sitting, “snoring” (from the speaker) while sleeping and “dancing” or “kicking” while standing. The availability of these self-referential actions enhance the realism of the behavior of the pet robot. Use of these self-referential arcs can be dictated by the behavior and posture determination sequences noted above. 
     An additional important new feature of the embodiment of the existence of a special “neutral” posture node. All of the prior discussion has assumed that the pet robot will always reside in one of a plurality of predefined states. However, it is possible that the pet robot might be moved while it is not operating, or a particular joint could move in an unexpected manner. Either of these situations might result in the pet robot not being aware of its current posture (i.e., the pet robot is not in one of the predefined states and is also not transitioning between two predefined states). In this case, it is not possible to determine any movement that should be taken to arrive at a next desired posture. Additionally, any unknown movements might result in an unsafe posture, possibly damaging the pet robot. 
     In order to account for this possibility, a “neutral” state is provided in accordance with the invention. This “neutral” state is entered into from any other posture, predefined or not by slowly and carefully relaxing and opening all joints of the pet robot, for example. Therefore, dotted lines in FIG. 9 indicate this transition to the neutral state. These dotted lines would emanate from any node, any point on any action or transition, or even from any posture not normally allowed by the pet robot, and therefore are not represented on the chart. Once the pet robot has reached this neutral position, it has reached a defined node on the chart of FIG. 9, and transition from this neutral node to other desired nodes in a safe manner, as described above can be performed. 
     Finally, an additional feature shown in the embodiment of FIG. 9 includes a “fall down” node. If knocked over, or even if proceeding along proper action and transition arcs, the pet robot falls over, it is necessary for the pet robot to determine that it has fallen, and to then get up. To determine it has fallen, a sensor “S” functions as an acceleration sensor, and registers that the pet robot has fallen over by a measured acceleration. If the appropriate sensor reading is reversed, the pet robot will assume that it is currently at the “fall down” node. While the falling transition arc is shown emanating from the sleeping node, like the neutral state transition arcs, arcs leading to the “fall down” state can come from anywhere on the diagram. 
     After determining it has fallen, the pet robot must then determine how to get up. Upon entering the “fall down” node, the pet robot performs a “determine side position” action depicted in FIG. 9 as a self-referential action arc. This arc employs a predetermined sequence of actions to determine the actual position and orientation of the pet robot. In the preferred embodiment of a pet robot dog, as shown in FIG. 1, the dog will either be on its right side or left side. Therefore, turning the head of the pet robot dog in both directions to determine which direction encounters an obstruction (the ground) will allow a determination of on which side the pet robot dog is lying. If another pet robot structure were used, an alternative test sequence would be employed to determine orientation and position. 
     After determining that it has fallen, and its orientation, the pet robot is considered existing at a particular node “fall down”. From this node, a predetermined action sequence “struggle” is performed to transition the pet robot to the neutral node discussed above. Another sequence of postures could also be defined. Rather than advancing to “neutral”, advancing to “lying-down”, or “standing”, could be possible, for example, based upon the posture of the pet robot before falling and confirmation that this movement will not damage the pet robot. In this manner, a pet robot that has fallen over can determine that it has fallen, and safely get up. 
     Referring once again to FIG. 3, when posture transition mechanism  42  receives behavior command information S 16  from behavior deciding mechanism, the next behavior to be implemented has been determined. In addition to sending this information to the posture control mechanism, it is also forwarded to speaker  42   a  and LED  42   b . Because upon generation of behavior command information S 16  all action to be taken are determined, and posture transition only implements these determined behaviors, sound and light from the LED and speaker can also be instructed in accordance with behavior control information S 16 . 
     Each behavior dictated by behavior deciding mechanism  41  requires movement of a predetermined number of parts of the pet robot of the invention. Thus, in a preferred embodiment, if the pet robot includes a body, head, legs and a tail, while standing up from a sitting position might require all of these parts, other actions, such as sitting from a standing position, or walking might require less than all of these parts. In order to accomplish these movements most efficiently and naturally, two control modes are available to be invoked in behavior control information S 16 . 
     The first mode is an “entire” body mode. This mode is used when all parts of the body are required to follow a predetermined sequence of movements for the pet robot to transition from a current state to a next state. No substantial variation by any part of the pet robot is permitted. All parts are instructed in accordance with a single set of commands. 
     The second mode is a “component” mode in which individual parts of the pet robot are controlled through individual sets of commands. Therefore, if a pet robot is walking, for example, a single set of commands exists for movement of the legs. The walking posture specifies a particular sequence of movements of the legs for walking. However, neither the head nor the tail are required for walking. Therefore, in accordance with the invention these currently unnecessary parts are controlled to move independently, in accordance with the various input data to behavior deciding mechanism. For example, if the decision is made for the pet robot to walk, the movement of the legs is determined as required for walking. However, the tail wagging and head positions can be independently determined based on the emotional or instinctual state. If the pet robot is happy, the tail can wag more, the head can be held raised up, and the pet robot will appear joyful. If sad, the movement of the tail and head can be adjusted accordingly. 
     As is shown in FIG. 10, a block diagram of a pet robot  1050  constructed in accordance with the invention is shown. Pet robot  1050  includes a main body portion  1051 , a head  1052 , legs  1053  and a tail  1054 . Transition from a current position to a next position is achieved through the movement of one or more of the body portions through a predetermined number of movements. Plane  1010  represents the possible movements from a starting mode  1012  to other posture modes  1014  or  1016 . Plane  1010  employs the “entire” mode, and therefor the transition arcs included movement for each part of pet robot. 
     Plane  1020  represents possible posture modes and transitions for the head only of the pet robot  1050 , plane  1030  represents the same for the legs and plane  1040  represents the same for the tail. These independent planes are employed when less than all of the parts of pet robot  1050  are required to perform the transition to the next posture as dictated by the behavior information. The parts not specifically required therefore follow an independent transition path. For example, to walk plane  1030  will require that legs  1053  follow a predetermined transition path to accomplish this walking. However, plane  1020  for the head and plane  1040  for the tail can move in any allowable transition path. As is shown, in each of these individual planes, the transition paths lead back to a central, starting posture mode. This is to insure that each body part returns to a known position that will not affect the other movements of the pet robot. The selection of these paths is preferably determined based upon various sensor information and the determined emotional and instinctual values determined above. These paths could also be determined in any other numbers of ways. By determining these non-essential transition paths independently from the essential transition paths, a wider range of motions, and therefore a more realistic acting pet robot can be provided. 
     Finally, referring back to FIG. 3, control mechanism  43  produces control signal S 5  for driving actuators  23  based on posture transition information S 18 . These produced control signals S 5  are then transmitted to actuators  23 . Actuators  23  are thereby driven to operate pet robot  1  in the desired manner. 
     In accordance with the above construction of the invention, the emotion and instinct model units  40  in controller  32  change the emotional and instinctive states of pet robot  1  based on the input information S 1 -S 3  supplied thereto. Such changes of the emotional and instinctive states are thereby reflected upon the action of pet robot  1 . This enables the pet robot to autonomously behave in accordance with emotional and instinctive states created by the robot in response to both internal and external stimuli. 
     Behavior deciding mechanism  41  in controller  32  determines the next state subsequent to the current state to be transitioned to based upon both the current state depending on a history of the input information S 14  having been previously supplied to the pet robot, and the currently supplied input information S 14 . This also contributes to enabling the pet robot to autonomously behave in accordance with created emotional and instinctive states. 
     Posture transition mechanism  42  in controller  32  changes the current posture of pet robot  1  for transition from a current posture to a next posture corresponding to behavior command information S 16  via a predetermined route. Pet robot  1  can therefor avoid taking an unsafe posture, or from turning over. 
     The emotional and instinctive states of pet robot  1  are changed based at least in part on input information S 1 -S 3  supplied to controller  32 . Thereafter, the action of pet robot  1  is determined in accordance with such changes of the emotional and instinctive states. The next posture to be transitioned to is selected depending on the decided behavior to be next implemented by pet robot  1  so that is able to autonomously behave in accordance with the emotional and instinctive states. As a result, pet robot  1  behaves very much like a genuine pet. 
     While the above embodiment has been described in connection with receiving the user&#39;s commands transmitted from the remote controller in the form of infrared rays, the present invention is not limited to this case. For example, the user&#39;s commands may be transmitted in the form of electrical waves or sound waves, including spoken language, musical notes or other audible indicators. 
     Also, while the above embodiment has been described in connection with receiving the user&#39;s commands via command receiving unit  30  made up of remote controller command receiver  13  and microphone  11 , the present invention is not limited to this case. For example, a computer or other appropriate device may be connected to pet robot  1 , and the user&#39;s commands may be received via the connected computer or device. 
     Furthermore, while the above embodiment has been described deciding the emotional and instinctive states employing emotion units  50 A- 50 F indicating six kinds of emotions, and instinct units  51 A- 51 D indicating four kinds of instincts, the present invention is not limited to this case. For example, other emotion or instinct units may be added. Stated otherwise, the emotional and instinctive states may be decided by a combination including other various kinds of emotion units and instinct units in any other suitable number than described above. 
     While the above embodiment has been described using the behavior deciding mechanism  41  to determine the next action based on command signals S 1 , external information signals S 2 , internal information signals S 3 , emotion and instinct state information S 10 , and behavior information S 12 , the present invention is not limited to this case. The next action may be determined based on less than all of command signals S 1 , external information signals S 2 , internal information signals S 3 , emotion and instinct state information S 10 , and behavior information S 12 . 
     Additionally, while the above embodiment has been described in applying the present invention to pet robot  1 , the present invention is not limited to this case. For example, the present invention may also be applicable to other various robot apparatuses such as those robot apparatuses which are employed in the fields of games and exhibitions for the purpose of entertainment. 
     According to the present invention, as described above, because a robot apparatus includes emotion and instinct models linked to an action, and decides the next action to be taken by changing the emotion and instinct models based on the input information, the robot apparatus can autonomously behave in accordance with the newly created emotional and instinctive states. As a result, a robot apparatus autonomously behaving in a natural way can be realized. 
     Because the next operating state to be transitioned to subsequent to the current operating state is decided in accordance with both the current operating state depending on the input information having been previously supplied to the robot apparatus, and the currently supplied input information, the robot apparatus can autonomously behave in accordance with the created emotional and instinctive states. As a result, a robot apparatus autonomously behaving in a natural way can be realized. 
     Because the current posture of the robot apparatus is changed by transitioning from the current posture to a next posture corresponding to the input information via a predetermined route, the robot apparatus can avoid from taking an unsafe or an impossible posture, for from turning over. As a result, a robot apparatus autonomously behaving in a natural way can be realized. 
     It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained and, because certain changes may be made in carrying out the above method and in the constructions set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.