Patent Application
20070244609
The above and other objects, features and advantages of the present invention will become more apparent from the following description of preferred embodiments in connection with the accompanying drawings, wherein:
The embodiments of the present invention are described below, in detail, with reference to the accompanying drawings. In the drawings, the same or similar components are denoted by common reference numerals.
Referring to the drawings,
The control device 10 includes an operation monitoring section 14 for monitoring the operating state of the electric motor 12, and an operation control section 16 for controlling the operation of the electric motor 12 in accordance with a monitored result of the operation monitoring section 14. The operation monitoring section 14 includes a data obtaining section 18 for obtaining operational data D of the electric motor 12; a threshold determining section 20 for selecting and determining an applicable threshold TA actually comparable with the operational data D, from among mutually different first and second thresholds T1 and T2 provided for comparison with the operational data D, in a manner so as to comply with a given condition C in connection with a temperature of the electric motor 12; and an abnormal-operation judging section 22 for comparing the operational data D obtained in the data obtaining section !R with the applicable threshold TA determined in the threshold determining section 20, and judging whether an abnormality arises in the operation of the electric motor 12. The operation control section 16 is configured to control the operation of the electric motor 12 in accordance with a judged result of the abnormal-operation judging section 22.
According to the control device 10 configured as described above, when an abnormal load is applied to the electric motor 12, in a movable structure such as a robot, machine tool or the like (not shown) using the electric motor 12 as the driving source for the moving part, as the result of a collision of the moving part (i.e., the driven object of the electric motor 12) such as the robot arm, the tool or the like, with an obstacle (not shown) or the failure of a reduction gear mechanism (not shown) of the electric motor 12, the abnormal-operation judging section 22 of the operation monitoring section 14 compares the real-time operational data D of the electric motor 12 with the applicable threshold TA and determines whether there is an abnormality in the operation of the electric motor 12, so as to immediately detect or determine the cause of the abnormal operation, such as a collision of the moving part, failure of the reduction gear mechanism, etc. Then, in accordance with the judged result of the abnormal-operation judging section 22, the operation control section 16 can allow, when the cause of the abnormal operation is detected, the electric motor 12 to immediately perform an operation as a measure to cope with the situation, such as halting or reversing the operation of the electric motor 12. As a result, it is possible to prevent mechanical components of the movable structure from breaking, along with the electric motor 12 and the obstacle, as well as to prevent the other secondary accidents.
In particular, in the control device 10, the threshold determining section 20 is configured to select and determine the applicable threshold TA from among the first and second thresholds T1 and T2 (for example, T1<T2) in a manner complying with the condition C in connection with the temperature of the electric motor 12, so that it is possible to take the fact that the viscosity of a lubricating oil changes due to the influence of the temperature of the electric motor 12 into consideration during the operation of the electric motor 12, and thus to selectively use either one of the thresholds to suit the temperature of the electric motor 12, in such a manner that, for example the first threshold T1 is used as the applicable threshold TA for the abnormal operation judgment if the temperature-related condition C is not satisfied, while the second threshold T2 is used as the applicable threshold TA for the abnormal operation judgment if the temperature-related condition C is satisfied. In this connection, it should be noted that the condition C in connection with the temperature of the electric motor 12 involves ambient temperature, taking into consideration the fact that the temperature of the electric motor 12 is affected by ambient temperature.
Therefore, for example, with regard to the lubricating oil supplied to the movable areas of the electric motor 12 and the driven object, if the viscosity of the lubricating oil deteriorates under a relatively high temperature environment, a threshold having a lower value (e.g., T1) can be used and an abnormal-operation judgment criteria can thus be made to be more strict, and if the viscosity of the lubricating oil increases under a relatively low temperature environment, a threshold having a higher value (e.g., T2) can be used and an abnormal-operation judgment criteria can thus be made to be less strict. As a result, according to the control device 10, it is possible to quickly and accurately detect the abnormal operation of the electric motor 12 as a result of a collision of the driven object, the failure of the reduction gear mechanism or the like, without being affected by ambient temperature or the temperature of the electric motor (in particular, without causing a false detection due to the increased viscosity of the lubricating oil), and to allow certain measures to cope with the situation, such as halting or reversing the electric motor 12, taken immediately, so as to ensure safety in an automatic control system.
In the configuration described above, the first and second thresholds T1 and T2 may be provided by, e.g., manually inputting them into the control device 10 by an operator, or storing them in a storage medium so as to be readable by the control device 10. Also, the temperature-related condition C may be given to the control device 10 by inputting by an operator or a reading from a storage medium in a way similar to the above. In these circumstances, the control device 10 may include an input section and a storage section (not shown) for the thresholds T1, T2 and the condition C.
Further, in the configuration described above, the threshold determining section 20 may be configured to select and determine the applicable threshold TA from among three or more mutually different thresholds provided for comparison with the operational data D, in a manner so as to comply with the condition C. In this case, several kinds or levels of temperature-related conditions C are set (e.g., the temperature-related conditions C are respectively set for the different temperatures of the electric motor 12) so as to suitably and selectively use the three or more thresholds. According to this configuration, several divided or different situations of the operation of the electric motor 12 can be prepared, and several applicable thresholds TA optimal for the divided situations can be determined, so that it is possible to accurately detect the abnormal operation of the electric motor 12. In this connection, any of the three or more thresholds correspond to the first and second thresholds T1 and T2, and therefore, the configuration of the control device 10 described above (and the embodiments described later) can be applied to the configuration in which three or more thresholds are provided.
Still further, in the configuration described above, the operational data D obtained in the data obtaining section 18 may be any one, or desired combination, of position deviation data in a feedback control, velocity deviation data in a feedback control, actually measured driving-current data, and estimated disturbance torque, obtained during the operation of the electric motor 12. In this connection, the position deviation data, the velocity deviation data and the driving current data are obtainable as data commonly used in the feedback control of the electric motor 12 On the other hand, as described in JP-B-2665984 and JP-B-2749724, the estimated disturbance torque may be one which is estimated from a torque command value and an actually measured velocity value of the electric motor 12, and a disturbance estimating observer for performing such estimation may be incorporated into the data obtaining section 18. In this connection, the position and velocity deviation data may be obtained on the basis of not only a feedback variable from an output element (such as a shaft) of the electric motor 12, but also a feedback variable from a position/velocity detector additionally provided for a driven object (such as a robot arm) of the electric motor 12. Thus, when the control device 10 is configured to obtain data generally used in a common automatic control system as the operational data D, it is possible to simplify the configuration of the control device 10.
The control method according to the present invention has a configuration for monitoring the operating state of the electric motor 12, and controlling the operation of the electric motor 12 in accordance with the monitored operating state. In the first step U1, the operational data D of the electric motor 12 is obtained. In the next step U2, the first and second thresholds T1 and T2 differing from each other are provided for comparison with the operational data D. In the next step U3, the condition C in connection with the temperature of the electric motor 12 is set to be used for selecting the applicable threshold TR actually comparable with the operational data P from among the first and second thresholds T1 and T2. In the next step U4, the applicable threshold TA is selected and determined from among the first and second thresholds T1 and T2 in a manner as to comply with the condition C. In the next step US, the operational data D is compared with the applicable threshold TA to judge whether an abnormality arises in the operation of the electric motor 12. In the next step U6, the operation of the electric motor 12 is controlled in accordance with the judged result in step U5, relating to the abnormal operation of the electric motor 12.
The control method configured as described above can also cause the characteristic effects similar to those of the control device 10 described above. Also, in the above configuration, three or more thresholds, differing from each other, may be provided for comparison with the operational data D, so as to allow several applicable thresholds TA to be selected and determined from among three or more thresholds, in a manner so as to comply with several kinds or levels of conditions C.
In the control device 30, the operation monitoring section 14 further includes a temperature detecting section 32 for detecting the actual temperature PA of the electric motor 12. The threshold determining section 20 is configured to compare the actual temperature PA detected by the temperature detecting section 32 with a reference temperature P0 of the electric motor 12, which is given as the temperature-related condition C to the threshold determining section 20. The threshold determining section 20 thus determines a lower one of the first and second thresholds T1 and T2 (e.g., T1) as the applicable threshold TA in a case where the actual temperature PA is higher than the reference temperature P0, and determines a higher one of the first and second thresholds T1 and T2 (e.g., T2) as the applicable threshold TA in a case where the actual temperature PA is lower than the reference temperature P0.
In the control device 30 configured as described above, it is possible to selectively use either one of the first and second thresholds T1 and T2 (erg., T1<T2), taking into consideration the situation of the actual temperature PA of the electric motor 12 detected by the temperature detecting section 32 when it is compared with the reference temperature P0 of the electric motor 12 given as the condition C. More specifically, if the electric motor 12 is being warmed up due to continuous operation (i.e., the viscosity of the lubricating oil deteriorates), a threshold having a lower value (e.g., T1) can be used and an abnormal-operation judgment criteria can thus be made to be more strict, and if the electric motor 12 is halted and cooled down (i.e., the viscosity of the lubricating oil increases), a threshold having a higher value (e.g., T2) can be used and an abnormal-operation judgment criteria can thus be made to be less strict. As a result, according to the control device 30, it is possible to predict the change in the viscosity of the lubricating oil supplied to the movable areas of the electric motor 12 and the driven object, directly based on the actual temperature PA of the electric motor 12, and thus use the optimal applicable threshold TA for the abnormal operation judgment, so as to further improve the detection accuracy of the abnormal operation of the electric motor 12.
In the configuration described above, the reference temperature P0 of the electric motor 12, given as the condition C, may be set at a suitable value on the basis of the experiment and experience, taking into consideration an attribute such as the material of the lubricating oil actually supplied to the movable areas of the electric motor 12 and the driven object.
In the control method shown in
In the next step V8, the operational data D is compared with the applicable threshold TA determined in steps V6 and V7. If the operational data D is higher than (and equal to, in the drawing) the applicable threshold TA, it is determined that there is an abnormality in the operation of the electric motor 12, and in step V9, the operation of the electric motor 12 is stopped. On the other hand, if the operational data D is lower than the applicable threshold TA, it is determined that the operation of the-electric motor 12 is normal, and in step V10, the electric motor 12 is kept continuous. The control method configured as described above can also cause characteristic effects similar to those of the control device 30 described above.
In the control device 40, the operation monitoring section 14 further comprises a time registering section 42 for measuring the actual resting time RA of the electric motor 12. The threshold determining section 20 is configured to compare the actual resting time RA last measured in the time registering section 42 with a reference resting time R0 of the electric motor 12 given as the temperature-related condition C to the threshold determining section 20. The threshold determining section 20 thus determines a lower one of the first and second thresholds T1 and T2 (e.g., T1) as the applicable threshold TA in a case where the actual resting time RA is shorter than the reference resting time R0.
In this configuration, it is possible to selectively use either one of the first and second thresholds T1 and T2 (e.g., T1<T2), taking into consideration the situation of the actual resting time RA of the electric motor 12 last measured by the time registering section 42 (i.e., in a period just before or nearest to a measuring time point) when compared with the reference resting time R0 of the electric motor 12 given as the condition C. More specifically, if the last-measured resting time RA of the electric motor 12 is shorter than the reference resting time R0, it is assumed that the electric motor 12 is in a warmed-up state and keeping residual heat resulting from operation before the present resting time (i.e., the viscosity of the lubricating oil deteriorates), a threshold having a lower value (e.g., T1) can be used and an abnormal-operation judgment criteria can thus be made to be more strict. On the other hand, if the last-measured resting time RA of the electric motor 12 is longer than the reference resting time R0, it is assumed that the electric motor 12 is not affected by residual heat resulting from operation before the present resting time. However, a next operation may have started before the time of measuring, and therefore, it is advantageous to determine the threshold while considering the latest situation of the operation.
Thus, in the control device 40, the time registering section 42 is configured to further measure an actual operating time QA of the electric motor 12. In this configuration, if the actual resting time RA is longer than the reference resting time R0 as a result of comparing the last-measured actual resting time RA with the reference resting time R0, the threshold determining section 20 compares the actual operating time QA last measured in the time registering section 42 with a reference operating time Q0 of the electric motor 12 given as the temperature-related condition C. The threshold determining section 20 thus determines a lower one of the first and second thresholds T1 and T2 (e.g., T1) as the applicable threshold TA in a case where the actual operating time QA is longer than the reference operating time Q0, and determines a higher one of the first and second thresholds T1 and T2 (e.g., T2) as the applicable threshold TA in a case where the actual operating time QA is shorter than the reference operating time Q0.
In the above configuration, in the case where the last-measured actual resting time RA of the electric motor 12 is longer than the reference resting time R0, it is possible to selectively use either one of the first and second thresholds T1 and T2 (e,g., T1<T2), taking into consideration the situation of the actual operating time QA of the electric motor 12 last measured by the time registering section 42 (i.e., in a current period including a measuring time point) when compared with the reference operating time Q0 of the electric motor 12 given as the condition C. More specifically, if the last-measured actual operating time QA of the electric motor 12 is longer than the reference operating time Q0, it is assumed that the electric motor 12 is in a sufficiently warmed-up state (i.e., the viscosity of the lubricating oil deteriorates), a threshold having a lower value (e.g., T1) can be used and an abnormal-operation judgment criteria can thus be made to be more strict on the other hand, if the last-measured actual operating time QA of the electric motor 12 is shorter than the reference operating time Q0, it is assumed that the electric motor 12 remains in a cooled-down state (i.e., the viscosity of the lubricating oil increases), a threshold having a higher value (e.g., T2) can be used and an abnormal-operation judgment criteria can thus be made to be less strict.
Thus, according to the control device 40, it is possible to predict the change in the viscosity of the lubricating oil supplied to the movable areas of the electric motor 12 and the driven object, indirectly based on the actual resting time RA and the actual operating time QA of the electric motor 12, and thus to use the optimal applicable threshold TA for the abnormal operation judgment, so as to further improve the detection accuracy of the abnormal operation of the electric motor 12. In this regard, the control device 40 may have somewhat less reliable than the above-described control device 30 in which the change in the viscosity of the lubricating oil is directly predicted based on the actual temperature PA of the electric motor 12. However, the control device 40 has an advantage that it does not need to provide an additional component such as a temperature sensor as the temperature detecting section 32, but can use a clock typically provided in a control device as the time registering section 42, and thus can be manufactured at a lower cost than the control device 30.
In the configuration described above, each of the reference resting time R0 and the reference operating time Q0 of the electric motor 12, given as the condition C, may also be set at a suitable time on the basis of the experiment and experience, taking into consideration an attribute such as the material of the lubricating oil supplied to the movable areas of the electric motor 12 and the driven object.
In the control method shown in
In the next step W7, the last-measured actual resting time RA is compared with the reference resting time R0. If the last-measured actual resting time RA is shorter than the reference resting time R0, the first threshold T1 having the lower value is determined, in step W8, as the applicable threshold TA. On the other hand, if the last-measured actual resting time RA is longer than (and equal to, in the drawing) the reference resting time R0, the last-measured actual operating time QA is compared, in step W9, with the reference operating time Q0. Then, if the last-measured actual operating time QA is longer than (and equal to, in the drawing) the reference operating time Q0, the first threshold T1 having the lower value is determined, in step W8, as the applicable threshold TA. On the other hand, if the last-measured actual operating time QA is shorter than the reference operating time Q0, the second threshold T2 having the higher value is determined, in step W10, as the applicable threshold TA.
In the next step W11, the operational data D is compared with the applicable threshold TA-determined in steps W8 and W10. If the operational data D is higher than (and equal to, in the drawing) the applicable threshold TA, it is determined that there is an abnormality in the operation of the electric motor 12, and in step W12, the operation of the electric motor 12 is stopped. On the other hand, if the operational data D is lower than the applicable threshold TA, it is determined that the operation of the electric motor 12 is normal, and in step W13, the electric motor 12 is kept continuous. The control method configured as described above can also cause the characteristic effects similar to those of the control device 40 described above.
While the invention has been described with reference to specific preferred embodiments, it will be understood, by those skilled in the art, that various changes and modifications may be made thereto without departing from the scope of the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-113728 | Apr 2006 | JP | national |
