JP2012250304A - Method for controlling robot, and robot - Google Patents

Abstract

Provided is a robot control method capable of retreating using a gyro sensor when an encoder fails.
A robot control method includes a motor, an angle sensor for detecting a rotation angle of the motor, an arm connected to the motor, and an inertial sensor attached to the arm. Detecting the abnormality of the angle sensor during the operation of the robot; determining that the angle sensor has failed when the abnormality of the angle sensor is detected; and determining a retreat movement path of the arm And a calculation step of calculating an angular velocity and an angle of the angle sensor that has failed using the inertial sensor, and a step of performing a retreat movement operation according to the retraction movement path based on the calculation result obtained in the calculation step. .
[Selection] Figure 3

Description

  The present invention relates to a robot control method and a robot driven using the robot control method.

  A robot having a multi-joint structure used in operations such as workpiece transfer and assembly is employed in many fields. Recently, these robots have been required to move the arm more quickly and accurately. Therefore, when working with a plurality of robots, if it is determined that one robot fails and the work time is delayed, the operation of the target robot is stopped and the work that can be continued in the other robot is executed. A robot control method has been proposed (see, for example, Patent Document 1).

JP 2000-194212 A

  In Patent Document 1, when a failure of one robot is detected, it is necessary to immediately stop the operation in order to ensure safety. However, if the failure target robot is stopped in a shared work area with the other robot, the work efficiency of the other robot is remarkably lowered because the work of the other robot cannot be performed in that area. In such a case, a method of retracting and stopping the arm of the failure target robot at a position away from the shared area is conceivable.

In such a method, an angle sensor for detecting the rotation angle of the motor is used to regulate the amount of movement of the arm. However, if the angle sensor fails, it cannot be retreated by a predetermined retraction movement path. . As a result, if there is an obstacle in the retreat movement route, it may interfere with the obstacle and stop at that position or cause further failure.
In addition, when the worker's work area is included as an obstacle, the worker's safety may be threatened.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

Application Example 1 A robot control method according to this application example includes a motor, an angle sensor that detects a rotation angle of the motor, an arm connected to the motor, and an inertial sensor attached to the arm. A robot control method, comprising: detecting an abnormality of the angle sensor during a work operation of the robot; determining that the angle sensor has failed when detecting an abnormality of the angle sensor; A step of determining a movement route, a calculation step of calculating an angular velocity and an angle of the angle sensor that has failed using the inertial sensor, and a retraction movement operation according to the retraction movement route based on a calculation result obtained in the calculation step. And performing the process.
Here, for example, an encoder can be used as the angle sensor, and a gyro sensor can be used as the inertial sensor.

The robot according to this application example includes an angle sensor that detects the rotation angle of the motor and an inertial sensor that detects the inertia amount of the arm tip. The inertial sensor detects the vibration at the tip of the arm and is provided mainly for the purpose of suppressing the vibration. However, when an abnormality in the angle sensor (abnormality that is determined to be a failure) is detected, The retracting movement of the arm is controlled and stopped via a predetermined retracting movement path. Therefore, the arm can be retracted to a predetermined position along a predetermined retraction movement path without providing a plurality of angle sensors in consideration of retraction movement after failure.
In addition, it is possible to prevent a reduction in work efficiency and a reduction in maintenance workability caused by stopping at the abnormality detection position as in the prior art.

  Application Example 2 In the robot control method according to the application example described above, the retract movement path is a range that interferes with an object that obstructs the movement of the arm within a movable range of the arm, or a work range of an operator. It is preferable that a movement route that avoids the above is selected.

In this way, the arm retreat movement path is a path that avoids objects that obstruct the movement of the workpiece, jig, etc., so that the arm interferes with the work, jig, etc. and stops at that position. And can prevent further breakdown.
In addition, when the worker's work area exists in the arm movable range, it is possible to prevent the worker's safety from being threatened by using a retreat movement route that avoids the work area.

  Application Example 3 In the robot control method according to the application example described above, it is preferable that the retreat movement speed after detecting the abnormality of the angle sensor is slower than the operation speed at the time of detecting the abnormality.

  The retreat movement by the inertial sensor is controlled using the angular velocity and angle calculation result of the broken angle sensor calculated from the detection value of the inertial sensor. In this case, the accuracy of the signal is generally lower when the calculation result is used than when the angle sensor is used. Therefore, safety can be improved by slowing down the operation speed.

  Application Example 4 In the robot control method according to the application example described above, the robot includes two arm units each having the motor and the arm, and the two arm units can operate independently. The two arm units are provided with the angle sensor and the inertial sensor, and when the angle sensor of one arm unit detects an abnormality, the arm unit in which the abnormality is detected moves in the retreat movement. It is preferable that the operation is performed and the other arm unit is continuously driven based on the movement path of the normal work.

  The robot having such a configuration is called a double-armed robot because two sets of arm units can be driven independently. When an abnormality is detected in the angle sensor of one arm unit, the arm unit in which the abnormality is detected is retracted using an inertial sensor, and the other arm unit is used for normal work set in advance using an angle sensor. It can be performed. At this time, the retreating movement path is set so as to avoid the shared work area with the other arm unit that is not in failure, so that the operation of the other arm unit is not hindered.

  Application Example 5 A robot according to this application example includes a motor, an arm connected to and driven by the motor, an angle sensor that detects a rotation angle of the motor, an inertial sensor attached to the arm, An angular velocity and angle calculation unit that calculates an angular velocity or an angle from a detection value of the angle sensor, an abnormality detection unit that detects abnormality of the angle sensor, a movement path generation unit that generates a movement path of the arm, and the abnormality detection When the unit detects an abnormality of the angle sensor, the motor is driven and controlled to move the arm to a predetermined position based on the retreat movement path of the movement path using the detection information of the inertia sensor. And a control unit.

According to this application example, when an abnormality of the angle sensor (an abnormality that is determined to be a failure) is detected, the inertial sensor is used to control the retracting movement of the arm and pass through a predetermined retracting movement path. Stop. Therefore, the arm can be retracted to a predetermined position along a predetermined retraction movement path without providing a plurality of angle sensors in consideration of retraction movement after failure.
In addition, it is possible to prevent a reduction in work efficiency and a reduction in maintenance workability caused by stopping at the abnormality detection position as in the prior art.

  Application Example 6 In the robot according to the application example, two sets of arm units including the motor and the arm are provided, and the two sets of arm units can operate independently, and the two sets of arms The unit is preferably provided with the angle sensor and the inertial sensor.

  A robot having such a configuration is generally called a double-armed robot. When a failure of the angle sensor of one arm unit of the two arms is detected, the arm unit in which the abnormality is detected is retreated, and the other arm unit performs normal work set by the normal angle sensor. It can be carried out. At this time, the retreating movement path is set so as to avoid the shared work area with the other arm unit that is not in failure, so that the operation of the other arm unit is not hindered.

FIG. 2 is a configuration explanatory diagram illustrating a schematic configuration of the robot according to the first embodiment. FIG. 2 is a configuration explanatory diagram illustrating a main configuration of a control device according to the first embodiment. Flow explanatory drawing which shows the main processes of the robot control method.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)

First, the configuration of the robot 10 will be described.
FIG. 1 is an explanatory diagram illustrating a schematic configuration of the robot according to the first embodiment. Note that FIG. 1 is a schematic diagram in which the vertical and horizontal scales of each member or part are different from actual ones in order to make each member recognizable. In FIG. 1, the robot 10 is configured by connecting a plurality of motors and arms based on a flat base 38. On the base 38, a support base 39 having a space is disposed. This space is divided vertically by the support plate portion 40.

  A motor 41 is disposed in a lower space of the support plate portion 40, and a first encoder 42 as an angle sensor is disposed at an axial end portion of the motor 41. The first encoder 42 detects the rotation angle of the motor 41.

  A first speed reducer 43 is disposed in a space above the support plate portion 40, and a rotation shaft 41 a of the motor 41 passes through the support plate portion 40 and is connected to the first speed reducer 43. An output shaft 43a is provided on the upper side of the first speed reducer 43, and the output shaft 43a rotates at a rotational speed obtained by reducing the rotational speed of the motor 41 with a predetermined reduction ratio. The first reduction gear 43 can employ various reduction mechanisms, but in this embodiment, a harmonic drive (registered trademark) is adopted. The output shaft 43 a protrudes above the support base 39 through the hole 39 a of the support base 39.

  One end of an arm 44 is connected to the projecting output shaft 43a, and the arm 44 rotates in the XY plane with the output shaft 43a as a rotation axis. A second speed reducer 46 and a motor 47 are overlapped and connected to the other end of the arm 44, and a second encoder 48 as an angle sensor is disposed at the end of the motor 47 in the rotation axis direction. The second encoder 48 detects the rotation angle of the motor 47. The output shaft 46 a of the second reduction gear 46 projects from the arm 44 through the hole 44 a of the arm 44. The output shaft 46a of the second speed reducer 46 rotates at a rotational speed obtained by reducing the rotational speed of the motor 47 with a predetermined reduction ratio.

  As the motor 41 and the motor 47, various motors can be used as long as the rotation direction can be controlled by an electric signal. In the present embodiment, for example, a DC motor is employed. Since the first encoder 42 only needs to be able to detect the rotation angle of the motor 41 and the second encoder 48 only needs to be able to detect the rotation angle of the motor 47, various rotary encoders can be used. In the present embodiment, for example, an optical rotary encoder is employed. One end of an arm 49 is connected to the output shaft 46a and rotates in the XY plane with the output shaft 46a as a rotation axis.

  A gyro sensor 50 serving as an inertia sensor is disposed at the other end of the arm 49. The type of the gyro sensor 50 is not particularly limited, but in the present embodiment, a vibration type gyro sensor is employed. The gyro sensor 50 employs a gyro sensor that can detect at least in the Z-axis direction.

  A motor 51 is disposed on the side of the gyro sensor 50 of the arm 49, and a rotating shaft 51 a of the motor 51 projects through the hole 49 a of the arm 49 and protrudes toward the base 38. A lifting device 52 is connected to the rotating shaft 51a, and the rotating shaft 51a can be rotated by the rotating shaft 51a.

  A hand portion 53 is disposed at the lower end portion of the lifting device 52. The lifting device 52 has a linear motion mechanism that moves up and down (in the Z-axis direction), and can lift and lower the hand portion 53. The hand portion 53 includes a plurality of finger portions 53a and a linear motion mechanism (not shown), and the linear motion mechanism can change the interval between the plurality of finger portions 53a. The hand 53 can hold a work target work (not shown) between the finger parts 53a.

  The robot 10 includes a control device 34 that controls the drive system described above. The control device 34 controls the driving of the motors 41, 47, 51, the angle sensors 42, 48, the detection interface of the gyro sensor 50, and the movement of the arms 44, 49 based on the detection values of the angle sensors 42, 48, and the gyro sensor 50. An arithmetic unit for calculating a route is included.

Next, the configuration and function of the control device 34 will be described.
FIG. 2 is a configuration explanatory diagram illustrating a main configuration of the control device according to the present embodiment. The control device 34 obtains the rotation angle detection value of the motor 41 by the first encoder 42, the rotation angle detection value of the motor 47 by the second encoder 48, and the detection value of the gyro sensor 50, and determines the angular velocity and angle of the failed encoder. An angular velocity / angle calculator 60, an abnormality detector 61 for detecting an abnormality in the first encoder 42 or the second encoder 48, a movement path generator 62 for generating movement paths of the arms 44 and 49, and a movement path A control unit 63 that controls the rotation angle and the rotation direction of the motors 41 and 47 to move the arms 44 and 49 using the path instructed by the generation unit 62 is configured.

Note that the control unit 63 uses the angular velocity and angle of the failed encoder calculated using the detection information of the gyro sensor 50 when the abnormality detection unit 61 detects the abnormality of the first encoder 42 or the second encoder 48. The motors 41 and 47 are driven and controlled so that the arms 44 and 49 are moved to predetermined positions based on the retreat movement path among the movement paths described above.
(Robot control method)

Next, a method for controlling the robot 10 described above will be described with reference to FIGS. Here, a method of retracting control of the arms 44 and 49 when either the first encoder 42 or the second encoder 48 is detected as abnormal (that is, determined as a failure) will be described.
FIG. 3 is an explanatory flow diagram illustrating the main steps of the robot control method. First, the operation of the robot 10 is started, and the movement paths of the arms 44 and 49 generated by the movement path generation unit 62 are determined (S1). The movement path includes a work movement path for performing actual work and a retreat movement path when an abnormality of the first encoder 42 or the second encoder 48 is detected.

  The work movement path is a movement path for actual work based on a work program taught in advance, and the robot 10 is controlled based on the detection signal of the first encoder 42 or the second encoder 48 so as to follow this movement path. The The retract drive path is a path that moves from a position where an abnormality is detected to a predetermined position, and selects a path that is as short as possible.

  Subsequently, it is determined whether there is an abnormality detected in the first encoder 42 or the second encoder 48 (S2). Abnormality is detected when the detection value of the first encoder 42 or the second encoder 48 is a value that is not normally possible or when a value deviating from the determined movement path is detected (that is, a failure has occurred). Is determined. The detection timing is sequentially performed in accordance with the detection resolution of the first encoder 42 and the second encoder 48 during the operation of the robot 10.

  If no abnormality is detected (NO), the instructed work operation is continued (S3). Then, it is determined whether the predetermined movement has been completed according to the movement route defined in the work program (S4). If it is determined that the predetermined movement has been completed (YES), the process proceeds to the next operation. If it is determined that the movement does not end (NO), steps S1 to S4 until the end are repeated.

  When an abnormality is detected in the abnormality detection step (S2) (YES), a retreat movement route is determined (S10). The retreat movement route determines a route from the position where the abnormality is detected to a predetermined retraction position, and it is desirable to select a route that is shortened as much as possible. The retreat movement path is a movement path in which the arm 44 and the arm 49 (including the hand portion 53) avoid an object that obstructs movement of a work, a jig, or the like within the movable range of the arms 44 and 49. Select. In addition, when there is a worker's work area within the movable range of the arms 44 and 49, and there is a shared work area with the robot 10 along with other robots, this shared work area also becomes an obstacle. Therefore, a retreat movement route that avoids these work areas is selected. In addition, when another attached robot uses a camera, an area that does not block the visual field of the camera is set as a retreat movement path.

  Next, when it is determined that one of the first encoder 42 or the second encoder 48 has failed, the angular velocity and angle of the failed encoder are calculated using the gyro sensor 50 and the non-failed encoder in order to retreat. (S11). This calculation is performed by a method of calculating the rotation angle of the motor 41 or the motor 47 during the retraction movement by integrating the angular velocities detected using the gyro sensor 50.

The parameters for performing this calculation process are shown below.
θ _m1 : the angular velocity of the motor 41 calculated from the angle detected by the first encoder 42.
θ _m2 : Angular velocity of the motor 47 calculated from the angle detected by the second encoder 48.
ω _m1 : An angular velocity of the motor 41 calculated by approximating the angle detected by the first encoder 42.
ω _m2 : Angular velocity of the motor 47 calculated by approximating the angle detected by the second encoder 48.
N ₁ : Reduction ratio of the first reduction gear 43.
N ₂ : Reduction ratio of the second reduction gear 46.
ω _g : Angular velocity of the gyro sensor 50.
And

First, the angular velocity ω _m1 ′ and the rotation angle θ _m1 ′ of the motor 41 when the first encoder 42 fails are expressed by the following equations.

なお、θ_m1cは、第１エンコーダー４２が故障する直前に検出したモーター４１の回転角度として算出したものである。

Θ _m1c is calculated as the rotation angle of the motor 41 detected immediately before the first encoder 42 fails.

Further, the angular velocity ω _m2 ′ and the rotation angle θ _m2 ′ of the motor 47 when the second encoder 48 fails are expressed by the following equations.

なお、θ_m2cは、第２エンコーダー４８が故障する直前に検出したモーター４７の回転角度として算出したものである。

Θ _m2c is calculated as the rotation angle of the motor 47 detected immediately before the second encoder 48 fails.

The rotation of the motor 41 is controlled using the angular velocity ω _m1 ′ or the rotation angle θ _m1 ′ calculated using the above formula, and the rotation of the motor 47 is controlled using the angular velocity ω _m2 ′ or the rotation angle θ _m2 ′. Then, the arms 44 and 49 are retracted along the retracting movement path (S12).

  Then, it is determined whether or not the retreat operation to the predetermined retreat position has been completed (S13). If the completion of the retreat operation is confirmed (YES), it is stopped at that position. If the evacuation operation is not completed (NO), the evacuation movement is continued from the calculation step (S11) until the evacuation operation is completed. Further, it is more preferable to set the position at which the retreat operation is completed to a position that does not hinder the designated work and a position where maintenance is easy.

  It should be noted that the retreating movement speed of the arms 44 and 49 is preferably set to be slower than the operation speed at the time when the abnormality is detected. The retraction movement using the gyro sensor 50 is performed by calculating the angular velocity and angle of the failed encoder calculated using the detection value of the gyro sensor 50 with reference to the angular velocity and angle of the first encoder 42 or the second encoder 48 that has failed. And to control.

Since the angular velocity ω _g detected by the gyro sensor 50 may include an error, the position accuracy deteriorates if the integration is continued for a long time. However, if the time is only a retreating movement, there is no problem. Accuracy can be maintained. For example, when the gyro sensor has an offset error of 0.5 [deg / s] and is moved for 6 minutes, the calculated angle becomes an error of 180 [deg] or more in terms of the rotation angle of the arm. However, the angle error of the arms 44 and 49 is 2.5 to 5 [deg] because the retraction movement can be performed in about 5 to 10 seconds. Therefore, if the evacuation site has a margin corresponding to 2.5 to 5 [deg], it can be sufficiently put into practical use.

  According to the robot control method of the present embodiment and the robot 10 using this robot control method, when an abnormality (abnormality determined to be a failure) of the first encoder 42 or the second encoder 48 is detected, the gyro sensor 50 is used to control the retreat movement of the arms 44 and 49, and is stopped via a predetermined retraction movement path. Therefore, the arms 44 and 49 can be retracted to a predetermined position by using the gyro sensor 50 provided for vibration suppression without providing two encoders so as to complement each other for one motor.

Further, by making the retreat movement path of the arms 44 and 49 a path that avoids the obstacle (work target work, jig), the arms 44 and 49 interfere with the obstacle and stop at that position. , Can prevent further failure.
In addition, when an operator's work area | region is included as an obstruction, there exists an effect that it can prevent that a worker's safety is threatened. The worker's work area is, for example, a work area specified by a safety device such as a photoelectric device.

  In addition, as an obstacle, when another robot is provided side by side and there is a shared work area with the robot 10, the operation of the other robot is not hindered by avoiding the shared work area as an obstacle. When the other robots installed are using the camera, the work efficiency of the other robots is not lowered by using the retreat movement path that does not block the visual field of the camera.

  Further, the retreating movement using the gyro sensor 50 controls the rotation of the motor 41 or the motor 47 using the angular velocity and angle of the failed first encoder 42 or the second encoder 48 and the detected value of the gyro sensor 50. Therefore, by operating at the moving speed including this calculation time, the arms 44 and 49 can be accurately moved along a predetermined moving path.

From the above, it is possible to prevent a decrease in work efficiency and a decrease in maintenance workability caused by stopping at the abnormality detection position as in the prior art.
(Embodiment 2)

  Next, Embodiment 2 will be described. In the second embodiment, the technical idea of the first embodiment described above is applied to a double-arm robot. Although not shown, the description will be given with reference to FIG. The dual-arm robot has a second arm unit that can operate independently of the first arm unit when the motors 41 and 47 and the arms 44 and 49 shown in FIG. 1 are configured as the first arm unit. . The arm 44 is a common arm for the first arm unit and the second arm unit, and is swung by the motor 41. The second arm unit has an arm (corresponding to the arm 49) that is rotated by a motor disposed at the tip of the arm 44.

Each of the two sets of arm units includes an encoder as an angle sensor and a gyro sensor as an inertial sensor. As shown in FIG. 1, the first arm unit is provided with a first encoder 42, a second encoder 48, and a gyro sensor 50. The second arm unit is also provided with an encoder and a gyro sensor corresponding to those used in the first arm unit. In addition, the 1st encoder 42 used for a 1st arm unit is common use.
And it controls using the robot control method (refer FIG. 3) mentioned above. For example, when the second encoder 48 of the first arm unit breaks down, the angular velocity ω _m2 ′ and the rotation angle θ _m2 ′ of the motor 47 calculated from the detection value of the gyro sensor 50 are used as Equations 3 and 4. And the retreat movement is performed using the gyro sensor 50.

  At this time, since the second arm unit is in a state in which normal operation can be performed, the second arm unit can continue to be driven according to the designated normal work movement path. The retraction movement path of the first arm unit is selected as a path that avoids the shared work area with the second arm unit, thereby preventing the operation of the second arm unit from being hindered and preventing the work efficiency of the robot from being lowered. be able to. Even when the encoder of the second arm unit breaks down, the second arm unit can be retreated with the same concept.

  When the first encoder 42 fails, the retraction movement paths of the first arm unit and the second arm unit are determined, moved to a predetermined retraction position, and stopped.

  Note that it is desirable to select the retracting movement path of the arm to be retracted so that the center of gravity position of the target arm is as close as possible to the center of gravity of the robot. This is because the double-armed robot balances the weight when the first arm unit and the second arm unit are driven.

  DESCRIPTION OF SYMBOLS 10 ... Robot, 41, 47 ... Motor, 42 ... 1st encoder (angle sensor), 44, 49 ... Arm, 48 ... 2nd encoder (angle sensor), 50 ... Gyro sensor (inertial sensor), 60 ... Fault encoder Angular velocity / angle calculation unit, 61 ... abnormality detection unit, 62 ... movement path generation unit, 63 ... control unit.

Claims (6)

A robot control method comprising: a motor; an angle sensor for detecting a rotation angle of the motor; an arm connected to the motor; and an inertial sensor attached to the arm;
Detecting the abnormality of the angle sensor during the operation of the robot;
Determining that the angle sensor has failed when detecting an abnormality of the angle sensor, and determining a retreat movement path of the arm;
A calculation step of calculating an angular velocity and an angle of the angle sensor that has failed using the inertial sensor;
A step of performing a retreat movement operation according to the retreat movement route based on the calculation result obtained in the calculation step;
A robot control method comprising: The retraction movement path is selected within a movable range of the arm, a range that interferes with an object that obstructs movement of the arm, or a movement path that avoids a work range of an operator,
The robot control method according to claim 1. The retreat movement speed after detecting the abnormality of the angle sensor is slower than the operation speed at the time of detecting the abnormality,
The robot control method according to claim 1, wherein: The robot includes two sets of arm units each having the motor and the arm, and the two sets of arm units can operate independently,
Two sets of arm units are provided with the angle sensor and the inertial sensor,
When the abnormality of the angle sensor of one arm unit is detected, the arm unit in which the abnormality is detected performs a retreat movement operation,
The robot control method according to claim 1, wherein the other arm unit continues to be driven based on a movement path of normal work. A motor and an arm coupled to and driven by the motor;
An angle sensor for detecting the rotation angle of the motor;
An inertial sensor attached to the arm;
An angular velocity and an angle calculation unit for calculating an angular velocity or an angle from a detection value of the angle sensor;
An abnormality detection unit for detecting an abnormality of the angle sensor;
A movement path generator for generating a movement path of the arm;
When the abnormality detection unit detects an abnormality of the angle sensor, the motor is used to move the arm to a predetermined position based on the retreat movement path of the movement path using the detection information of the inertia sensor. A control unit for driving control;
A robot characterized by comprising Two sets of arm units having the motor and the arm are provided, and the two sets of arm units can operate independently,
The two sets of arm units are provided with the angle sensor and the inertial sensor;
The robot according to claim 5.

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