Patent Publication Number: US-11045960-B2

Title: Life evaluating device and robot system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of and priority to Japanese Patent Application No. 2018-131070, filed on Jul. 10, 2018, the entire content of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present invention relates to a life evaluating device and a robot system. 
     BACKGROUND OF THE INVENTION 
     There has been known a life evaluating device that identifies a coefficient of friction of a transmission mechanism from a motor current and motor speed, estimates temperature of grease from a relation between a coefficient of friction and temperature of the grease determined in advance, corrects input speed of the transmission mechanism taking into account the estimated temperature of the grease, and evaluates a life of the grease from the corrected input speed (see, for example, Japanese Patent No. 4021354). 
     SUMMARY OF THE INVENTION 
     An aspect of the present invention is directed to a life evaluating device that evaluates a life of a lubricant in a machine including at least one motor and at least one transmission mechanism that is lubricated by the lubricant and transmits power of the at least one motor to a movable unit. The life evaluating device includes: a motor-heat-value calculating unit that calculates a motor heat value on the basis of a current value of the at least motor; a frictional-heat-value calculating unit that calculates a frictional heat value in the at least one transmission mechanism on the basis of rotating speed of the at least one motor and a coefficient of friction of the at least one transmission mechanism; a lubricant-temperature estimating unit that estimates temperature of the lubricant on the basis of the frictional heat value calculated by the frictional-heat-value calculating unit and the motor heat value calculated by the motor-heat-value calculating unit; and a life estimating unit that estimates the life of the lubricant on the basis of the temperature of the lubricant estimated by the lubricant-temperature estimating unit and information concerning impurities included in the lubricant. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an overall configuration diagram showing a robot system according to an embodiment of the present invention. 
         FIG. 2  is a partial longitudinal sectional view showing an example of a joint portion of a robot included in the robot system shown in  FIG. 1 . 
         FIG. 3  is a block diagram showing a life evaluating device according to the embodiment of the invention included in the robot system shown in  FIG. 1 . 
         FIG. 4  is a graph showing a relation between temperature of grease and a life of the grease in the case in which the temperature is maintained. 
         FIG. 5  is a block diagram showing a modification of the life evaluating device shown in  FIG. 3 . 
         FIG. 6  is a graph for explaining a calculation method for a replacement date by a replacement-date calculating unit for the grease in the modification of the life evaluating device shown in  FIG. 3 . 
         FIG. 7  is a diagram showing a display example of an estimated replacement date and a residual life output by the life evaluating device shown in  FIG. 6 . 
     
    
    
     DESCRIPTION OF EMBODIMENT(S) OF THE INVENTION 
     A life evaluating device  12  and a robot system  1  according to an embodiment of the present invention are explained below with reference to the drawings. 
     The robot system  1  according to this embodiment includes, as shown in  FIG. 1 , a robot  2 , a control device  3  that controls the robot  2 , and a display unit  4  connected to the control device  3 . 
     The robot  2  is a robot including one or more links (movable units)  5  and one or more joints. In an example shown in  FIG. 1 , a six-axis articulated robot can be illustrated as the robot  2 . 
     An example of a joint portion  6  of the robot  2  is shown in  FIG. 2 . The joint portion  6  includes a base  7 , a link  5  supported to be capable of swinging around an axis with respect to the base  7 , a reducer (a transmission mechanism)  8  disposed between the link  5  and the base  7 , and a motor  9  that generates power input to the reducer  8 . 
     Grease (a lubricant)  10  is filled inside the reducer  8  to lubricate gears and bearings configuring the reducer  8 . 
     When the motor  9  is actuated, rotation of the motor  9  is reduced by the reducer  8 . The link  5  is rotated with respect to the base  7 . 
     In a state shown in  FIG. 2 , a sensor (a detecting unit)  21  that measures concentration of iron powder, which is impurities included in the grease  10 , is inserted into a grease supply port for filling the grease inside the reducer  8 . The iron powder concentration measured by the sensor  21  is used for calculating life of the grease  10 . Note that, in this embodiment, the sensor  21  detects the concentration of the impurities included in the grease  10 . However, in another embodiment, the concentration of the impurities included in the grease  10  may be calculated according to the torque of the motor  9 , the rotating speed of the motor  9 , or the like. The control device  3  includes a robot control unit (a control device)  11  that controls the robot  2  and the life evaluating device  12  according to this embodiment that evaluates the life of the grease  10 . 
     The life evaluating device  12  includes, as shown in  FIG. 3 , a room-temperature input unit  13  to which a room temperature is input, a motor-heat-value calculating unit  14  that calculates a motor heat value, a frictional-heat-value calculating unit  15  that calculates a frictional heat value in the reducer  8 , an air-cooling-heat-dissipation-amount calculating unit  16 , a lubricant-temperature estimating unit  17  that estimates temperature of the grease  10  on the basis of heat quantities calculated by the calculating units  14 ,  15 , and  16 , a concentration input unit  22  to which the iron powder concentration measured by the sensor  21  is input, and a life calculating unit (a life estimating unit)  18  that calculates life of the grease  10  on the basis of the input iron powder concentration and the temperature estimated by the lubricant-temperature estimating unit  17 . All said units, or some of them, can also advantageously be integrated into the life evaluating device, which comprises a processor or plurality of processors. 
     The room temperature may be manually input to the room-temperature input unit  13  by an operator or may be detected by a temperature sensor. 
     In this embodiment, the iron powder concentration measured by the sensor  21  is input by the operator. However, in another embodiment, measurement information of the sensor  21  disposed inside the reducer  8  may be automatically transmitted to the life calculating unit  18 . 
     The motor-heat-value calculating unit  14  is configured to calculate a motor heat value according to Equation (1) on the basis of a motor state amount input from the robot control unit  11 , that is, a current value of the motor  9  (a motor current value) and rotating speed of the motor  9  (motor rotating speed).
 
 W   1   =A   1   ×I   M   2 +( A   2   ×S   M   +A   3   ×S   M   2 )  (1)
 
     Where, W 1  represents a motor heat value, A 1 , A 2 , and A 3  represent coefficients, I M  represents a motor current value, and S M  represents motor rotating speed. 
     In Equation (1), a first term of a right side indicates a copper loss in the motor  9  and a second term indicates an iron loss. 
     The frictional-heat-value calculating unit  15  is configured to calculate a frictional heat value according to Equation (2) on the basis of motor state amounts input from the robot control unit  11 , that is, frictional torque and motor rotating speed. 
     
       
         
           
             
               
                 
                   
                     W 
                     2 
                   
                   = 
                   
                     
                       T 
                       × 
                       
                         S 
                         M 
                       
                     
                     = 
                     
                       
                         ( 
                         
                           
                             B 
                             1 
                           
                           + 
                           
                             
                               B 
                               2 
                             
                             × 
                             
                               T 
                               M 
                             
                           
                           + 
                           
                             
                               B 
                               3 
                             
                             × 
                             
                               S 
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                         ) 
                       
                       × 
                       
                         S 
                         M 
                       
                     
                   
                 
               
               
                 
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                   2 
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     Where, W 2  represents a frictional heat value, T represents frictional torque, B 1 , B 2 , and B 3  represent coefficients of friction identified in advance, and T M  represents torque necessary when driving the link  5  of the robot  2  when friction is absent. 
     The torque T M  is calculated by, in general, a publicly-known calculation method such as a Lagrangian method or a Newton-Euler method using the position, the acceleration, mass information, and the like of the link  5 . 
     The air-cooling-heat-dissipation-amount calculating unit  16  calculates an air cooling heat dissipation amount generated because relative speed is generated between the reducer  8  and the ambient air when the reducer  8  itself moves in the air according to driving of the robot  2 . The air-cooling-heat-dissipation-amount calculating unit  16  is configured to calculate moving speed of the robot  2  in the position of the reducer on the basis of the rotating speed of the motor  9  input from the robot control unit  11  and calculate an air cooling heat dissipation amount according to Equation (3) on the basis of the calculated moving speed.
 
 W   3   =C   1   ×S   R   (3)
 
     Where, W 3  represents an air cooling heat dissipation amount, C1 represents a value calculated by a sum of the motor heat value W 1  and the frictional heat value W 2 , and S R  represents moving speed of the robot  2  in the position of the reducer  8 . 
     The lubricant-temperature estimating unit  17  is configured to estimate temperature of the grease  10  according to Equation (4).
 
 T=T   0   +D   1 ×(Σ E   i   ×W   1i ) D     5     +D   2 ×(Σ F   i   ×W   2i ) D     6     +D   3   ×W   3   +D   4   ×W   4   (4)
 
     Where, T represents an estimated temperature of the grease  10 , T 0  represents a room temperature, i represents an axis affecting a target axis lubricant temperature including a target axis, D 1 , D 2 , D 3 , D 4 , D 5 , and D 6  represent coefficients identified by executing operations in various patterns in experiments in advance and acquiring data of grease temperatures, room temperatures, heat values, moving speeds of the reducer  8 , and heat values of another heat generation source in the respective patterns, W 4  represents a heat value of the other heat generation source, E i  represents a coefficient of a motor heat value W 1i  identified by executing operations in various patterns in experiments in advance and acquiring data of temperatures of the lubricant, room temperatures, heat values, moving speeds of the reducer  8 , and heat values of the other heat generation source in the respective patterns, and F i  represents a coefficient of a frictional heat value W 2i  identified by executing operations in various patterns in experiments in advance and acquiring data of temperatures of the lubricant, room temperatures, heat values, moving speeds of the reducer  8 , and heat values of the other heat generation source in the respective patterns. 
     As the other heat generation source, another joint or device near the grease  10  can be illustrated. 
     In addition to Equation (4), heat radiation may be taken into account. 
     In this embodiment, the estimated temperature T of the grease  10  is calculated by Equation (4) during the operation of the robot  2  and is set the same as the room temperature when the robot  2  is stopped. 
     As an example, when axes of the robot  2 , which is a six-axis articulated robot, are represented as a J1 axis, a J2 axis, a J3 axis, a J4 axis, a J5 axis, and a J6 axis, if the motors  9  and the reducers  8  of the J4 axis, the J5 axis, and the J6 axis are densely packed and affect one another, the estimated temperature T of the grease  10  targeting the J6 axis is estimated by Equation (5).
 
 T=T   0   +D   1 ×( E   4   ×W   14   +E   5   ×W   15   +E   6   ×W   16 ) D     5     +D   2 ×( F   4   ×W   24   +F   5   ×W   25   +F   6   ×W   26 ) D     6     +D   3   ×W   3   +D   4   ×W   4   (5)
 
     E 4  is a coefficient of a motor heat value W 14  of the J4 axis, E 5  is a coefficient of a motor heat value W 15  of the J5 axis, E 6  is a coefficient of a motor heat value W 16  of the J6 axis, F 4  is a coefficient of a frictional heat value W 24  of the J4 axis, F 5  is a coefficient of a frictional heat value W 25  of the J5 axis, and F 6  is a coefficient of a frictional heat value W 26  of the J6 axis. 
     In Equation (5), a case is illustrated in which the J1 axis, the J2 axis, and the J3 axis do not affect the J6 axis and the J4 axis and the J5 axis affect the J6 axis. However, when the J1 axis, the J2 axis, and the J3 axis also affect the J6 axis, W 11 , W 12 , W 13 , W 21 , W 22 , W 23 , E 1 , E 2 , E 3 , F 1 , F 2 , and F 3  are additionally written. 
     In Equation (5), the case is illustrated in which the J4 axis and the J5 axis affect the J6 axis. However, when the J4 axis and the J5 axis do not affect the J6 axis like the J1 axis, the J2 axis, and the J3 axis, W 14 , W 15 , W 24 , and W 25  (or E 4 , E 5 , F 4 , and F 5 ) are 0. 
     The temperature and the life of the grease  10  have a relation shown in  FIG. 4 . That is, when the temperature of the grease  10  is T0 or less, the life of the grease  10  is a fixed rated life Sg0. On the other hand, when the temperature is higher than T0, the life of the grease  10  exponentially decreases. Therefore, it is possible to calculate a life use amount using Equation (6) according to an estimated temperature and an estimated time.
 
 Sg=m∫A   k   dt   (6)
 
     Where, Sg represents a life use amount of the grease  10 , A represents a constant, k is (T−T0)/Δ when T&gt;T0 and is 0 when T≤T0, Δ represents a difference from temperature T0 at which the life use amount is A times, and m represents a constant that is 1 when iron powder concentration is equal to or smaller than a threshold and is larger than 1 when the iron powder concentration exceeds the threshold. 
     In Equation (6), both of a time during the operation of the robot  2  and a time during the stop of the robot  2  are calculated and totaled. 
     The life calculating unit  18  is configured to calculate a life use amount of the grease  10  from the estimated temperature of the grease  10  and the measured iron powder concentration using Equation (6). When focusing on the iron powder concentration and comparing life use amounts in the case in which only the iron powder concentration is different, for example, a life use amount Sg 1  in the case in which the iron powder concentration is P 1  (ppm) exceeding the threshold is m times as large as a life use amount Sg 0  in the case in which the iron powder concentration is P 0  (ppm) equal to or smaller than the threshold. In this way, from Equation (6), when the iron powder concentration rises and exceeds the threshold, the life use amount increases. 
     In this embodiment, as shown in  FIG. 3 , the life evaluating device  12  includes a residual-life calculating unit  19 . 
     The residual-life calculating unit  19  is configured to calculate a residual life using Equation (7).
 
Residual life=(1− Sg/Sg 0)×100%  (7)
 
     The display unit  4  may display the residual life itself calculated by the residual-life calculating unit  19  or may display a warning when the calculated residual life is smaller than a preset threshold. 
     With the life evaluating device  12  according to this embodiment configured as explained above and the robot system  1  including the life evaluating device  12 , the temperature of the grease  10 , which lubricates the reducer  8 , is estimated on the basis of not only the coefficient of friction in the reducer  8  but also the motor heat value. Therefore, there is an advantage that the temperature of the grease  10  is accurately estimated and it is possible to accurately evaluate the life of the grease  10  according to the estimated temperature of the grease  10  and the measured iron powder concentration in the grease  10 . 
     The motor heat value is calculated on the basis of the motor current and the motor rotating speed. Therefore, there is an advantage that, when heat generation by the motor rotating speed is large, it is possible to accurately calculate the motor heat value and it is possible to accurately evaluate the life of the grease  10 . When the heat value by the rotating speed of the motor  9  is small, the iron loss of the second term of the right side in Equation (1) may be omitted. 
     According to this embodiment, the temperature of the grease  10  is estimated also taking into account the air cooling heat dissipation value with which the reducer  8  disposed in the link  5  and moved is cooled by the movement. Consequently, it is possible to more accurately estimate temperature of the grease  10  and it is possible to accurately evaluate the life of the grease  10 . 
     According to this embodiment, the calculated life use amount is not displayed but the residual life is calculated and displayed. Therefore, there is an advantage that the operator can confirm a replacement time in advance. 
     Note that, in this embodiment, the residual life of the grease  10  is calculated and displayed. However, instead of this or in addition to this, as shown in  FIG. 5 , the life evaluating device  12  may include a replacement-date calculating unit  20  that calculates a replacement date of the grease  10 . 
     As shown in  FIG. 6 , the replacement-date calculating unit  20  calculates, using data of a life use amount of the grease  10  in the closest several days, an increase ratio of an integrated value of the life use amount using a method of least squares according to Equation (8) and predicts, using the calculated increase ratio, a time when the integrated value of the life use amount reaches a rated life. As an example, a calculation formula for calculating a recommended replacement date (an estimated replacement date) using a life use amount integrated value in the closest twenty days is indicated by Equation (8) below. 
     
       
         
           
             
               
                 
                   
                     Recommended 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     replacement 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     date 
                   
                   = 
                   
                     d 
                     + 
                     
                       
                         ( 
                         
                           2000 
                           - 
                           
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                             d 
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                             20 
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     Where, d represents a date when the latest Sg is calculated. 
     That is, when a use state of the robot  2  in the closest several days is continued as it is, a date when the life of the grease  10  is exhausted is predicted. The date is displayed on the display unit  4  for each of joints as shown in  FIG. 7 . 
     Since the estimated replacement date calculated by the replacement-date calculating unit  20  is displayed on the display unit  4  in this way, there is an advantage that it is possible to more clearly recognize a replacement time. In Equation (8), the method of least squares is illustrated. However, a calculation method is not limited to this. Any other approximation calculation method may be adopted. 
     The lubricant-temperature estimating unit  17  may generate a learned model for estimating temperature of the grease  10  according to machine learning using a frictional heat value calculated by the frictional-heat-value calculating unit  15  and a motor heat value calculated by the motor-heat-value calculating unit  14 . The generated learned model may be stored in the storing unit  23  shown in  FIG. 5 . 
     The lubricant-temperature estimating unit  17  may perform supervised learning based on the frictional heat value, the motor heat value, and an air cooling heat dissipation amount calculated by the air-cooling-heat-dissipation-amount calculating unit  16 , and actual temperature of the grease  10  and generate a learned model used for estimation of temperature of the grease  10 . The lubricant-temperature estimating unit  17  performs, for example, a regression analysis using a multiple regression equation of Equation (4) described above as a learning model and estimates all or a part of the coefficients D 1  to D 6 , E i  and F i  used in Equation (4) described above to create a learned model. 
     The learning by the lubricant-temperature estimating unit  17  is performed when the life evaluating device  12  is functioning in a learning mode. At this time, the lubricant-temperature estimating unit  17  creates teacher data in which the frictional heat value, the motor heat value, and the air cooling heat dissipation amount are set as input data and temperature serving as a measured value of the grease  10  is set as a label (output data) and performs supervised learning using the created teacher data. As the temperature of the grease  10  serving as the label, for example, the operator may manually set measured temperature of the grease  10  via the lubricant-temperature input unit  24  shown in  FIG. 5  or temperature detected by a not-shown temperature sensor attached on the inside or in the vicinity of the reducer  8  may be automatically acquired. The lubricant-temperature estimating unit  17  causes the storing unit  23  to store the generated learned model and uses the learned model in estimating temperature of the grease  10 . 
     Note that, in this embodiment, the grease  10  is illustrated as the lubricant that lubricates the reducer  8 . However, the life evaluating device  12  may be applied to any lubricant such as oil. An axis configuration of the robot  2  is not limited to the vertical articulated type shown in  FIG. 1 . The life evaluating device  12  may be applied to the robot system  1  including the robot  2  having any other axis configuration. 
     In the embodiment explained above, the iron powder is cited as an example of the impurities included in the grease  10  and the life use amount calculated using the iron powder concentration is explained. However, in another form, the life use amount may be calculated using information concerning impurities other than the iron powder. For example, the concentration of a resin material included in the grease  10  may be used. 
     From the above-described embodiment, the following invention is derived. 
     An aspect of the present invention is directed to a life evaluating device that evaluates a life of a lubricant in a machine including at least one motor and at least one transmission mechanism that is lubricated by the lubricant and transmits power of the at least one motor to a movable unit. The life evaluating device includes: a motor-heat-value calculating unit that calculates a motor heat value on the basis of a current value of the at least motor; a frictional-heat-value calculating unit that calculates a frictional heat value in the at least one transmission mechanism on the basis of rotating speed of the at least one motor and a coefficient of friction of the at least one transmission mechanism; a lubricant-temperature estimating unit that estimates temperature of the lubricant on the basis of the frictional heat value calculated by the frictional-heat-value calculating unit and the motor heat value calculated by the motor-heat-value calculating unit; and a life estimating unit that estimates the life of the lubricant on the basis of the temperature of the lubricant estimated by the lubricant-temperature estimating unit and information concerning impurities included in the lubricant. 
     According to the aspect, the motor heat value is calculated by the motor-heat-value calculating unit on the basis of the current value of the motor. The frictional heat value in the transmission mechanism is calculated by the frictional-heat-value calculating unit on the basis of the coefficient of friction of the transmission mechanism and the rotating speed of the motor. The temperature of the lubricant is estimated by the lubricant-temperature estimating unit on the basis of the calculated motor heat value and the calculated frictional heat value. The life of the lubricant is estimated by the life estimating unit on the basis of the information concerning the impurities included in the lubricant and the temperature of the lubricant estimated by the lubricant-temperature estimating unit. 
     Compared with the conventional life evaluating device that estimates temperature of the lubricant on the basis of only the coefficient of friction, since the heat value of the motor greatly contributing to a temperature rise of the lubricant and the information concerning the impurities contributing to the life of the lubricant are taken into account, it is possible to accurately evaluate the life of the lubricant. 
     In the aspect, the motor-heat-value calculating unit may calculate the motor heat value on the basis of the current value of the at least one motor and the rotating speed of the at least one motor. 
     Consequently, compared with when the motor heat value is calculated on the basis of only the current value of the motor, when heat generation by the rotating speed of the motor is large, it is possible to accurately calculate the motor heat value. 
     In the aspect, the life evaluating device may include an air-cooling-heat-dissipation-amount calculating unit that calculates an air cooling heat dissipation amount on the basis of moving speed of the at least one transmission mechanism. The lubricant-temperature estimating unit may estimate the temperature of the lubricant on the basis of the air cooling heat dissipation amount calculated by the air-cooling-heat-dissipation-amount calculating unit. 
     In this way, when the transmission mechanism is disposed in the movable unit and moved, forced air cooling is carried out by the movement. Therefore, the air cooling heat dissipation amount is calculated by the air-cooling-heat-dissipation-amount calculating unit on the basis of the moving speed of the transmission mechanism, and the temperature of the lubricant is estimated by the lubricant-temperature estimating unit on the basis of the air cooling heat dissipation amount. Consequently, it is possible to estimate temperature of the lubricant more conforming to a real machine. It is possible to accurately evaluate the life of the lubricant. 
     In the aspect, the life evaluating device may include a residual-life calculating unit that calculates a residual life on the basis of the life estimated by the life estimating unit. 
     In this way, the residual life is calculated by the residual-life calculating unit. Therefore, it is possible to confirm a replacement time in advance. 
     In the aspect, the life evaluating device may include a replacement-date calculating unit that calculates an estimated replacement date on the basis of the life estimated by the life estimating unit. 
     In this way, it is possible to more clearly recognize the replacement time according to the estimated replacement date calculated by the replacement-date calculating unit. 
     In the aspect, the lubricant-temperature estimating unit may estimate the temperature of the lubricant according to an equation described below.
 
 T=T   0   +D   1 ×(Σ E   i   ×W   1i ) D     5     +D   2 ×(Σ F   i   ×W   2i ) D     6     +D   3   ×W   3   +D   4   ×W   4  
 
     Where, T represents an estimated temperature of the lubricant, T 0  represents a room temperature, i represents an axis affecting a target axis lubricant temperature including a target axis, D 1 , D 2 , D 3 , D 4 , D 5 , and D 6  represent coefficients identified by executing operations in various patterns in experiments in advance and acquiring data of temperatures of the lubricant, room temperatures, heat values, moving speeds of a reducer, and heat values of another heat generation source in the respective patterns, W 3  represents an air cooling heat dissipation amount, W 4  represents a heat value of the other heat generation source, E i  represents a coefficient of the motor heat value W 1i , and F i  represents a coefficient of the frictional heat value W 2i . Each of E i  and F i  represents a constant identified by executing operations in various patterns in experiments in advance and acquiring data of temperatures of the lubricant, room temperatures, heat values, moving speeds of the reducer, and heat values of the other heat generation source in the respective patterns or is a constant set in advance. 
     In the aspect, the life estimating unit may estimate a life amount of the lubricant according to the following equation.
 
 Sg=m∫A   k   dt  
 
     Where, Sg represents a life use amount of the lubricant, A represents a constant set in advance, k is (T−T0)/Δ when an estimated temperature T of the lubricant &gt;T0 and is 0 when the estimated temperature T≤T0, Δ represents a difference from the temperature T0 at which the life use amount Sg is A times, and m represents a coefficient set according to an amount of the impurities included in the lubricant. 
     In the aspect, the lubricant-temperature estimating unit may generate, according to machine learning using the frictional heat value and the motor heat value, a learned model for estimating temperature of the lubricant from the frictional heat value and the motor heat value. 
     Consequently, it is possible to highly accurately estimate the temperature of the lubricant using the learned model based on data of the frictional heat values and the motor heat values in the various patterns. 
     In the aspect, the life evaluating device may include a storing unit that stores a learned model generated by machine learning using the frictional heat value and the motor heat value. The lubricant-temperature estimating unit may estimate the temperature of the lubricant using the learned model on the basis of the frictional heat value and the motor heat value. 
     Consequently, the estimation of the temperature of the lubricant using the learned model stored in the storing unit is performed. Therefore, it is possible to highly accurately estimate the temperature of the lubricant even if a learned model is not generated from the beginning. 
     In the aspect, the machine learning may be supervised learning using teacher data in which the frictional heat value and the motor heat value are set as input data and a measured value of the temperature of the lubricant is set as a label and the input data and the label are associated with each other. 
     Consequently, it is possible to highly accurately estimate temperature of the lubricant corresponding to the input data by using the measured value of the temperature of the lubricant as a correct answer. 
     Another aspect of the present invention provides a robot system including: a robot including the at least one motor including one or more motors, one or more movable units, and the at least one transmission mechanism including one or more transmission mechanisms that are lubricated by the lubricant and transmit power of the motors to the movable units; a control device that controls the motors of the robot; and any one of the life evaluating devices described above.