Patent Description:
Abnormality detection devices for articulated industrial robots are known, as disclosed in Patent Literature <NUM> or <NUM>. The device disclosed in Patent Literature <NUM> detects a moving position of each joint shaft of the robot and disturbance torque applied to the joint shaft at predetermined intervals when the robot is in operation, and calculates an average value of the disturbance torque detected at each moving position. The device then compares the calculated average value with a predetermined threshold, and determines that the robot has an abnormality when the average value exceeds the threshold.

Patent Literature <NUM>: <CIT>; Patent Literature <NUM>: Patent document <CIT>.

The movement of the respective joint shafts is sometimes small depending on the routine operations of the robot, and the small movement decreases the influence on the disturbance torque, which may impede the detection of a change in the disturbance torque necessary for the abnormality detection. The device disclosed in Patent Literature <NUM> may fail to detect an occurrence of an abnormality and thus has a problem of the accuracy of the abnormality detection if the change in the disturbance torque is small, since the device simply compares the disturbance torque with the constant threshold without taking account of the contents of the operations of the robot.

In view of the foregoing problem, the present invention provides an abnormality detection device, according to claim <NUM> and an abnormality detection method, according to claim <NUM>, capable of detecting an abnormality of a movable apparatus with a high accuracy regardless of whether the movement of the movable apparatus is small.

An abnormality detection device and an abnormality detection method according to the invention are defined by the appended independent claims. Specific embodiments are defined by the dependent claims. Such a device includes, inter alia, a control unit including a signal input unit to which a detection signal is input, the detection signal being obtained when a state of a movable apparatus is detected by a sensor, so that the control unit detects an abnormality of the movable apparatus in accordance with the detection signal. The control unit outputs a control signal to the movable apparatus so as to execute an integrated action in which a necessary action is added to a predetermined action in which no operation is executed on a target object. The control unit detects an abnormality of the movable apparatus in accordance with the detection signal detected when the integrated action is executed.

The aspect of the present invention can detect an abnormality of the movable apparatus with a high accuracy regardless of whether the movement of the movable apparatus is small.

<FIG> is a block diagram illustrating a configuration of an abnormality detection device and peripheral apparatuses according to an embodiment of the present invention. As illustrated in <FIG>, the abnormality detection device <NUM> according to the present embodiment is connected to a robot <NUM> (a movable apparatus) and a user interface <NUM> (indicated by reference sign "UI" in <FIG>), and detects an abnormality of the robot <NUM>. As used herein, the phrase "detecting an abnormality" encompasses a concept of not only detecting an abnormality currently caused but also predicting an abnormality which can be caused later.

The robot <NUM> is a teaching-playback multi-axis robot, for example. The term "teaching-playback" is indicative of a function of actually operating a robot to make action by a user using a teaching pendant belonging to the robot, and storing and reproducing the action so as to cause the robot to perform the action. While the present embodiment is illustrated with the teaching-playback robot, the present invention is not limited to this case.

The robot <NUM> includes a plurality of speed reducers <NUM>, a sensor <NUM>, an action control unit <NUM>, a disturbance torque calculation unit <NUM>, and a communication unit <NUM>.

Each speed reducer <NUM> includes a servo motor (simply referred to below as a "motor") for operating each joint shaft of a robot arm, and is operated in accordance with the control by the action control unit <NUM>. The operation of the respective speed reducers <NUM> causes a welding electrode (a welding part) mounted at the tip of the robot arm, for example, to come into contact with a necessary part of a target object to be processed (for example, a metal blank material) so as to execute the welding operation. The robot <NUM> can further execute various kinds of operations such as pressing, coating, resin molding, and assembling of a target object, in addition to the welding operation.

The sensor <NUM> includes a pulse generator or an encoder, for example, and detects various kinds of physical amounts such as a position and an angle of the robot arm operated by the respective speed reducers <NUM>, a rotation angle, a rotation speed, power consumption, and a current of each motor, and a rotation angle of the respective speed reducers <NUM>. The sensor <NUM> also detects a value of torque caused in each motor. The sensor <NUM> detects the respective physical amounts described above when the robot <NUM> executes an operation (such as welding) on the target object, and when the robot <NUM> executes a routine operation (a predetermined action) which is an action not performed on the target object. A detection signal detected by the sensor <NUM> (a detection signal obtained when the state of the movable apparatus is detected) is sent to the abnormality detection device <NUM> through the communication unit <NUM>.

The action control unit <NUM> causes the respective speed reducers <NUM> to operate according to an action program set by the teaching described above, and controls the respective robot arms and the joint shafts mounted on the robot <NUM> to perform necessary actions. When receiving, from the abnormality detection device <NUM>, a control signal which directs an integrated action to be executed for detecting an abnormality caused in the corresponding speed reducer <NUM>, as described below, the action control unit <NUM> controls the corresponding speed reducer <NUM> to execute the integrated action.

The disturbance torque calculation unit <NUM> calculates disturbance torque caused in each motor mounted in the respective speed reducers <NUM>. The term "disturbance torque" refers to a difference between a torque instruction value when controlling each motor and a torque detection value detected by the sensor <NUM>. The difference between the torque instruction value and the torque detection value is substantially constant when the speed reducer <NUM> is in a normal state and the motor operates stably, and the disturbance torque thus shows a stable numerical value. When an abnormality is caused in the speed reducer <NUM>, the operation of the motor is not stable, and a great change occurs in the disturbance torque applied to the motor.

The communication unit <NUM> sends work data of the robot <NUM> and various kinds of data such as the disturbance torque to the abnormality detection device <NUM>. When the control signal for directing the execution of the integrated action described below is sent from the abnormality detection device <NUM>, the communication unit <NUM> receives and outputs the control signal to the action control unit <NUM>.

The respective functions that the robot <NUM> has can be implemented in single or plural processing circuits. The respective processing circuits include a programmed processing device, such as a processing device including an electric circuit. The processing device includes an application-specific integrated circuit (ASIC) configured to execute the functions that the robot <NUM> has or conventional circuit components.

Next, the configuration of the abnormality detection device <NUM> is described below. The abnormality detection device <NUM> includes a communication unit <NUM>, a control unit <NUM>, and various kinds of databases (DBs). The control unit <NUM> includes a routine operation extraction unit <NUM>, a necessary action decision unit <NUM>, a necessary action setting unit <NUM>, and an abnormality determination unit <NUM>. The databases include a sensor DB <NUM>, a work history DB <NUM>, and a maintenance DB <NUM>.

The sensor DB <NUM> stores various kinds of detection signals detected by the sensor <NUM>. The detection signals to be stored include various detection signals detected by the sensor <NUM> when the robot <NUM> is executing a routine operation such as a chip dressing action. The detection signals detected by the sensor <NUM> include the position and the angle of the respective robot arms, the rotation angle and the rotation speed of the respective motors, and the rotation angle of the respective speed reducers <NUM>, as described above. The sensor DB <NUM> also stores the disturbance torque calculated by the disturbance torque calculation unit <NUM>. The sensor DB <NUM> thus serves as a storage unit configured to store the detection signals detected by the sensor <NUM> when the routine operation is executed by the robot <NUM>.

The work history DB <NUM> stores work data of the robot <NUM>. The work data includes various kinds of data regarding the work of the robot <NUM>, such as a work date, a work-started time, a work-stopped time, a continuous work time, and a continuous suspension time. The work data also includes a drive mode of the respective speed reducers <NUM>. The drive mode includes a normal drive mode, a maintenance mode, and a stop mode.

The maintenance DB <NUM> stores maintenance data acquired when an abnormality is caused or the occurrence of an abnormality is predicted in the respective speed reducers <NUM>, and maintenance is then made for the robot <NUM>. The maintenance data can be input by the operator through the user interface <NUM>. Alternatively, the maintenance may be determined to be made when the robot <NUM> is operated in the maintenance mode described above, so as to automatically create and store the maintenance data. The maintenance data includes an ID number of the corresponding speed reducer <NUM> to be maintained, the date and time of the maintenance executed, and the contents of the maintenance (such as a replacement, a repair, and a change of grease).

The communication unit <NUM> communicates with the communication unit <NUM> included in the robot <NUM>. The communication unit <NUM> outputs, to the work history DB <NUM>, the work data of the robot <NUM> sent from the robot <NUM>. The communication unit <NUM> also receives the detection signals detected by the sensor <NUM> and sent from the robot <NUM> to output the detection signals to the sensor DB <NUM>. The communication unit <NUM> thus serves as a signal input unit to which the detection signals obtained when the state of the robot <NUM> (the movable apparatus) is detected by the sensor <NUM> are input.

The abnormality determination unit <NUM> acquires, from the sensor DB <NUM>, the disturbance torque of the motor mounted in each speed reducer <NUM> of the robot <NUM>, and determines whether an abnormality is caused in the speed reducer <NUM> operated by the corresponding motor in accordance with the acquired disturbance torque. For example, the abnormality detection unit <NUM> calculates an abnormality level described below.

The abnormality level a(x'), where x' is the disturbance torque, is given by the following formula (<NUM>):
<MAT> where m is a sample average of the disturbance torque, and s is a standard deviation of the disturbance torque.

The abnormality determination unit <NUM> determines that the corresponding speed reducer <NUM> has an abnormality when the abnormality level a(x') exceeds a predetermined threshold. Instead of the above method, the abnormality determination unit <NUM> may calculate the abnormality level by use of a probability distribution such as kernel density estimation and density ratio estimation.

Still another method for the abnormality determination is to obtain a difference between the disturbance torque and a predetermined reference value through a mathematical operation, and further calculate a rate of change of the difference with the passage of time. The corresponding speed reducer <NUM> can be determined to have an abnormality when the rate of change exceeds a predetermined threshold. The predetermined reference value may be an average of the disturbance torque acquired in the same month one year ago.

The routine operation extraction unit <NUM> extracts the work data during the period of time in which the robot <NUM> is executing the routine operation (the predetermined action), in accordance with the work data of the robot <NUM> stored in the work history DB <NUM>. The routine operation as used herein refers to an action not executed on the processing target object by the robot <NUM> (the movable apparatus). For example, the routine operation is an action (a tip dressing action) of removing dust adhering to the surface of the welding electrode performed after the robot <NUM> executes the welding on the target object to be processed such as a blank material.

Instead of the method of using the work data stored in the work history DB <NUM>, a time table set in a production management device in a factory in which the operations are performed on the target object may be referred to when the robot <NUM> is connected to the production management device via a communication line, so as to acquire the work data of the robot <NUM>.

The necessary action decision unit <NUM> determines whether a necessary action necessary for detecting an abnormality of the corresponding speed reducer <NUM> is included in the action of the routine operation, in accordance with the work data of the routine operation extracted by the routine operation extraction unit <NUM>. The rotation angle of the motor in routine operation, namely, the rotation angle of the speed reducer <NUM> operated by the corresponding motor needs to be large to some extent in order that the abnormality determination unit <NUM> determines whether the speed reducer <NUM> has an abnormality as described above. For example, the speed reducer <NUM> needs to be operated by the rotation angle of <NUM> degrees or greater. The necessary action decision unit <NUM> determines whether such a necessary action is included in the routine operation. Alternatively, the amount of shift in the position of the robot arm may be used, instead of the use of the rotation angle of the speed reducer <NUM>.

The necessary action setting unit <NUM> sets the necessary action used in the necessary action decision unit <NUM>. The necessary action is independently allotted to each of the speed reducers <NUM>. For example, the necessary action setting unit <NUM> stores a map in which the respective speed reducers <NUM> are matched with the corresponding necessary actions, such that a speed reducer A is set to the rotation angle of <NUM> degrees, and a speed reducer B is set to the rotation angle of <NUM> degrees, for example. The necessary action setting unit <NUM> refers to this map so as to set the respective necessary actions.

The second embodiment described below adds the processing of weighting independently set for each of the speed reducers <NUM> (for example, multiplies a coefficient of weighting) while the necessary actions of the respective speed reducers <NUM> are set to a common action, so as to calculate the necessary actions for the respective speed reducers <NUM> by a mathematical operation. The third embodiment described below sets the respective necessary actions in accordance with the data of the disturbance torque having been acquired when the abnormality was caused in the respective speed reducers <NUM>.

The necessary action may be either an action attendant on the routine operation or a dummy action irrelative to the routine operation. Since the necessary action is added to the routine operation (the predetermined action), such as a chip dressing action, not executed on the target object (for example, welding), the necessary action does not have an influence on the operation executed on the target object.

The necessary action setting unit <NUM> sets the integrated action in which the necessary action is added to the predetermined action such as a chip dressing action, and sends the integrated action to the robot <NUM>.

The abnormality detection device <NUM> may be implemented by a computer including a central processing unit (CPU) <NUM>, a memory <NUM>, and the various databases (the sensor DB <NUM>, the work history DB <NUM>, and the maintenance DB <NUM>), as illustrated in <FIG>. A computer program (an abnormality detection program) is installed on the computer and executed so as to function as the abnormality detection device <NUM>. The CPU <NUM> thus functions as a plurality of information processing circuits included in the abnormality detection device <NUM>, namely, functions as the routine operation extraction unit <NUM>, the necessary action decision unit <NUM>, the necessary action setting unit <NUM>, and the abnormality determination unit <NUM>.

The respective functions included in the abnormality detection device <NUM> described above can be implemented in single or plural processing circuits. The respective processing circuits include a programmed processing device, such as a processing device including an electric circuit. The processing device includes an application-specific integrated circuit (ASIC) configured to execute the functions included in the abnormality detection device <NUM> or conventional circuit components.

Next, the processing process of the abnormality detection device <NUM> according to the first embodiment is described below with reference to the flowchart shown in <FIG>.

First, in step S11, the routine operation extraction unit <NUM> acquires the work data when the robot <NUM> is executing the routine operation, from the work data stored in the work history DB <NUM>. As described above, the routine operation extraction unit <NUM> may acquire the work data of the robot <NUM> while referring to the time table set in the production management device when the abnormality detection device <NUM> is connected to the production management device via the communication line.

In step S12, the necessary action setting unit <NUM> sets the necessary action necessary for detecting an abnormality of the corresponding speed reducer <NUM>. As described above, the necessary action setting unit <NUM> stores the map in which the respective speed reducers <NUM> are matched with the necessary actions, and refers to the map so as to set the respective necessary actions. For example, when the rotation angle necessary for detecting an abnormality of the speed reducer <NUM> is set to <NUM> degrees, the necessary action setting unit <NUM> sets the rotation angle of <NUM> degrees as the necessary action.

In step S13, the necessary action decision unit <NUM> determines whether the above necessary action is included in the routine operation in accordance with the work data acquired in the processing in step S11. In particular, the necessary action decision unit <NUM> determines whether the action in which the rotation angle of the corresponding speed reducer <NUM> is set to <NUM> degrees or greater is included in the routine operation.

When the necessary action is included in the routine operation, the necessary action setting unit <NUM> determines that the addition of the necessary action is not needed ("Unnecessary" in step S14), and the process proceeds to step S16.

When the necessary action is not included ("Necessary" in step S14), the process proceeds to step S15.

In step S15, the necessary action setting unit <NUM> sets the integrated action in which the necessary action is added to the predetermined action to be executed by the corresponding speed reducer <NUM>, and outputs the control signal so as to execute the integrated action. The control signal is sent from the communication unit <NUM> to the communication unit <NUM> of the robot <NUM>, and is further output to the action control unit <NUM>.

The action control unit <NUM> controls to execute the action (the integrated action) of rotating the speed reducer <NUM> by <NUM> degrees in accordance with the control signal. Alternatively, when the action of rotating the speed reducer <NUM> by <NUM> degrees is present in the routine operation, for example, the action control unit <NUM> changes this action to the action (the integrated action) of rotating the speed reducer <NUM> by <NUM> degrees. This enables the necessary action to be included in the routine operation.

In step S16, the abnormality determination unit <NUM> acquires the disturbance torque when the integrated action including the above necessary action is being executed.

In step S17, the abnormality determination unit <NUM> determines whether the corresponding speed reducer <NUM> has an abnormality by use of the above method in accordance with the acquired disturbance torque. For example, the abnormality determination unit <NUM> calculates the abnormality level according to the formula (<NUM>) described above, and determines that the corresponding speed reducer <NUM> has an abnormality when the calculated abnormality level exceeds a threshold.

The abnormality determination unit <NUM>, when determining that the corresponding speed reducer <NUM> has an abnormality (YES in step S17), notifies the operator of the occurrence of the abnormality in the speed reducer <NUM> in step S18. For example, the abnormality determination unit <NUM> causes a display (not illustrated) provided in the user interface <NUM> to display an image indicating the occurrence of the abnormality of the speed reducer <NUM>. The process thus can detect the abnormality of the target speed reducer <NUM> mounted on the robot <NUM>, namely, can detect the abnormality of the robot <NUM>.

As described above, the abnormality detection device <NUM> according to the first embodiment can achieve the following effects.

A second embodiment of the present invention is described below. The device configuration is the same as that shown in <FIG> described in the first embodiment, and overlapping explanations are not repeated below. The second embodiment differs from the first embodiment in adding weighting processing to the necessary action for each speed reducer <NUM> mounted on the robot <NUM> when the necessary action is added to the routine operation. The processing process of the abnormality detection device according to the second embodiment is described below with reference to the flowchart shown in <FIG>.

The flowchart shown in <FIG> differs from the flowchart shown in <FIG> described above in further including the processing in step S14a. The processing in step S14a is described below.

When the necessary action decision unit <NUM> determines that the addition of the necessary action is needed in the processing in step S14, the necessary action setting unit <NUM> executes the weighting processing which varies depending on the speed reducers <NUM> in step S14a.

For example, since the speed reducer <NUM> connected with a large load leads to large disturbance torque caused in the motor even if the rotation angle of the speed reducer <NUM> is small, the detection of an abnormality is possible. The rotation angle of the speed reducer <NUM> thus can be small, and is set to <NUM> degrees, for example.

The speed reducer <NUM> connected with a load smaller than the above load does not lead to a great change in the disturbance torque caused in the motor when the rotation angle of the speed reducer <NUM> is small, which hinders the detection of an abnormality. The rotation angle of the speed reducer <NUM> thus needs to be increased, and is set to <NUM> degrees, for example. This is the weighting processing executed for the necessary action depending on the load size connected to the respective speed reducers <NUM>. The load size connected to the respective speed reducers <NUM> includes torque driving the load, power consumption of the motor connected to the speed reducer <NUM>, and a flowing current, for example.

In step S15, the necessary action setting unit <NUM> then sets the integrated action in which the necessary action is added to the predetermined action executed by the corresponding speed reducer <NUM>, and outputs the control signal so as to execute the integrated action, in the same manner as in the first embodiment described above. The subsequent processing after step S15 is the same as that in the first embodiment shown in <FIG>, and overlapping explanations are not repeated below.

As described above, the abnormality detection device according to the second embodiment executes the weighting processing for the action (the necessary action) to be added so as to detect an abnormality, depending on the load size connected to the target speed reducer <NUM> of which an abnormality is to be detected. The abnormality detection device thus can obtain the minimum action necessary for detecting an abnormality, so as to avoid an unnecessary increase in the degree of the necessary action. The abnormality detection device thus can detect an abnormality of the speed reducer <NUM>, namely, can detect an abnormality of the robot <NUM> while minimizing the integrated action.

A third embodiment of the present invention is described below. The device configuration is the same as that shown in <FIG> described in the first embodiment, and overlapping explanations are not repeated below. The third embodiment differs from the first embodiment in setting the necessary action in accordance with a waveform of disturbance torque detected during the routine operation such as chip dressing having been executed before. The processing process of the abnormality detection device according to the third embodiment is described below with reference to the flowchart shown in <FIG>.

First, in step S31, the routine operation extraction unit <NUM> acquires the disturbance torque data when the target speed reducer <NUM> of which an abnormality is to be determined is executing the routine operation, from the past disturbance torque data stored in the sensor DB <NUM>. The routine operation extraction unit <NUM> also acquires the maintenance data when the speed reducer <NUM> had an abnormality and the maintenance was then made, from the maintenance data stored in the maintenance DB <NUM>.

In step S32, the routine operation extraction unit <NUM> detects a change in the disturbance torque when the speed reducer <NUM> has an abnormality, and obtains the necessary action of the corresponding speed reducer <NUM> (the rotation angle of the corresponding speed reducer <NUM> in this example) necessary for the abnormality decision. In particular, when the data is stored in the sensor DB <NUM>, indicating that the change in the disturbance torque was small when the rotation angle of the speed reducer <NUM> was smaller than <NUM> degrees, and the change in the disturbance torque was large when the rotation angle was greater than <NUM> degrees in the past case in which the abnormality was caused in the speed reducer <NUM>, the routine operation extraction unit <NUM> determines that the rotation angle of the speed reducer <NUM> necessary for the abnormality decision is <NUM> degrees.

In step S33, the necessary action setting unit <NUM> sets the necessary action. For example, the necessary action setting unit <NUM> sets the rotation angle of the speed reducer <NUM> to <NUM> degrees as the necessary action. The processing in step S34 to step S39 is then executed so as to determine an abnormality of the speed reducer <NUM>.

The processing in step S34 to step S39 is the same as the processing in step S13 to step S18 shown in <FIG>, and overlapping explanations are not repeated below.

As described above, the abnormality detection device according to the third embodiment causes the necessary action setting unit <NUM> to obtain the necessary action in accordance with the past disturbance torque caused in the motor of the corresponding speed reducer <NUM>, so as to avoid an unnecessary increase in the degree of the necessary action. The abnormality detection device thus can detect an abnormality of the target speed reducer <NUM>, namely, can detect an abnormality of the robot <NUM> while minimizing the integrated action.

The movable apparatus as an abnormality detection target is not limited to the robot <NUM>. Any robot including a rotating mechanism and a transmitting mechanism thereof can be a target to be detected.

The abnormality detection device <NUM> may be installed in a remote place to receive/send necessary signals or data via a communication line so as to detect an abnormality of the robot <NUM> (the movable apparatus). The abnormality detection of a plurality of robots may be executed by the single abnormality detection device <NUM>. The plural robots may be installed at different locations.

Claim 1:
An abnormality detection device of detecting an abnormality in a robot (<NUM>) including a speed reducer (<NUM>) for operating a joint shaft of the robot (<NUM>), the speed reducer (<NUM>) being driven by a motor, the robot (<NUM>) executing an operation on a target object, the device comprising a control unit (<NUM>) including a signal input unit to which a detection signal is input, the detection signal comprising a torque detection value of a torque caused in the motor and detected by a sensor (<NUM>),
characterized in that the control unit (<NUM>) is configured to:
output a control signal to the robot (<NUM>) so as to execute a routine operation and a necessary action introduced into the routine operation, wherein the routine operation is an operation not executed on the target object comprising an action of rotating the speed reducer (<NUM>), and wherein the necessary action is the action of rotating the speed reducer (<NUM>) with a rotation angle greater than or equal to a predetermined angle;
calculate a disturbance torque caused in the motor based on a difference between a torque instruction value when controlling the motor and the torque detection value detected by the sensor (<NUM>) when the necessary action is executed; and
detect the abnormality of the speed reducer (<NUM>) based on the disturbance torque and a predetermined threshold.