JP2019018327A - Origin alignment method and robot system - Google Patents

Abstract

To provide an origin alignment method that enables execution of origin alignment without causing deformation of an arm and a stopper and damage to them, and a robot system.SOLUTION: An average value of a value of an angle detector in the state of pressing an arm against a stopper provided on the side of one end in a movable range by moving the arm by speed control and a value of the angle detector in the state of pressing the arm against a stopper provided on the side of the other end in the movable range is obtained for estimation of a central position between the stoppers. Thus, origin alignment for the arm is performed.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an origin adjustment method and a robot system for performing origin adjustment of a robot arm.

  In general, the robot is provided with an angle detector such as an optical encoder for the purpose of obtaining the rotation angle of the arm. At this time, if a deviation occurs between the value of the angle detector 8 and the actual rotation angle of the arm, it directly leads to a decrease in position accuracy during the robot operation. For this reason, after assembling the robot, the arm is pressed against a stopper that mechanically defines the movable range of the arm, and origin matching is performed by setting the average of the values of the angle detector 8 acquired at both ends of the movable range as the origin. (For example, see Patent Document 1).

Japanese Patent Laid-Open No. 62-103705

By the way, when performing the origin adjustment by the technique as in Patent Document 1, it is natural that the arm needs to be rotated and pressed against the stopper.
However, since the origin has not yet been determined at the time when the origin is aligned, the position of the arm has not yet been determined. In that case, the arm cannot be rotated by angle control based on the rotation angle of the arm as in normal operation. If the arm is rotated in a state in which angle control is difficult, the rotational speed and torque become excessive, and there is a high possibility that the arm and the stopper may be deformed or damaged.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an origin adjustment method and a robot system that can perform origin adjustment without causing deformation or damage of an arm or a stopper.

  According to the first aspect of the present invention, there is provided a robot having an arm driven by a motor and an angle detector for detecting a rotation angle of the motor, wherein a movable range of the arm is mechanically defined by a stopper. This is a method for adjusting the origin of the robot to perform the origin adjustment.

  In the case of such a configuration that mechanically defines the movable range of the arm, the value of the angle detector in a state where the arm is pressed against a stopper provided at one end of the movable range, and the arm in the movable range. It is considered that the origin can be adjusted using the value of the angle detector in a state of being pressed against the stopper provided on the other end side.

  Specifically, the value of the angle detector when the arm is pressed against the stopper is acquired at both ends of the movable range, and the average of the acquired values is set, for example, the midpoint of the movable range is set as the origin Can do. When setting the position of one stopper instead of the midpoint of the movable range as the origin, it is also possible to add the half as an offset value after specifying the midpoint.

  On the other hand, since the origin is not specified at the stage before the origin alignment, the current position of the arm is not determined. In other words, at the time when the origin is to be adjusted, it is unclear at which angle the arm is currently located, so that it is not possible to perform angle control such as moving to the angle immediately before contacting the stopper, for example. .

  In this case, it is considered that the arm can be brought into contact with the stopper regardless of the initial position of the arm within the movable range by sufficiently increasing the motor output. However, if the motor output is too large, the rotational speed and torque become excessive, and there is a high risk of causing deformation or damage to the arm or stopper. Depending on the rotation direction of the arm, even if the motor output is the same due to the weight of the tool, the speed of the arm increases, and the arm may collide with the stopper with excessive torque. The same applies to the method of gradually increasing the motor output.

  On the other hand, even if the minimum motor output is set at the time of shipment, etc. in order to perform the origin adjustment, if the tool is installed on the user side after shipment, the motor output is insufficient and the arm May not be able to be moved to the stopper.

  Thus, it is difficult to set in advance the motor output when the arm is pressed against the stopper in order to perform the origin adjustment. In other words, when the origin is adjusted by pressing the arm against the stopper, there is a problem to be considered and taken into account in the preparation stage before acquiring the value of the angle detector 8.

  Therefore, when the arm is pressed against the stopper, the arm is moved by speed control. In this case, even if the position of the arm is undetermined, the speed of the arm, more precisely, the angular speed of the arm can be obtained based on the time change of the value of the angle detector. That is, in the stage until the origin is adjusted, angle control is not possible, but speed control is possible.

  In this case, by setting the target speed at the time of speed control in advance so as not to cause the deformation or damage of the arm or stopper, the deformation or damage of the arm or stopper can be prevented. By controlling the arm at a constant target speed instead of a constant motor output, the arm can be moved even when a tool or the like is attached on the user side after shipment. That is, the arm can be moved to the stopper regardless of the position of the arm when the origin is aligned.

  Furthermore, if the target speed is constant, it is considered that the arm contacts the stopper in an equivalent state, that is, in an equivalent pressing state, at both ends of the movable range. If the pressing force is equal, even if a structure such as a speed reducer interposed between the arm and the motor is elastically deformed, the elastic deformation is equal in magnitude and reverse in direction. Conceivable.

  Thereby, as described above, the midpoint of the movable range can be correctly specified by taking the average value of the values of the angle detectors acquired at both ends of the movable range. By setting the midpoint as the origin, the origin can be adjusted without causing deformation or damage of the arm or the stopper.

In addition, since the origin can be adjusted with a single robot system without using a jig, the origin can be easily and efficiently adjusted not only during work before shipment but also during maintenance after shipment. it can. In addition, since the origin can be automatically adjusted, it does not depend on the skill level of the operator.
Further, according to the invention of the robot system described in claim 8, the same effect as that of the invention according to claim 1 can be obtained, and the origin can be adjusted without causing deformation or damage of the arm or the stopper. Can do.

  According to the second aspect of the present invention, the arm is pressed against the stopper with a pressing force determined by speed control. As described above, when speed control is performed at a constant target speed, it is considered that the arm contacts the stopper in an equivalent pressing state. At this time, the motor output is determined by the difference between the target speed and the actual speed, and since the actual speed is 0 in the pressed state, the pressing force is determined by the set target speed.

  Therefore, when the arm is pressed against the stopper at both ends of the movable range, the same force is applied to each stopper, and the amount of elastic deformation becomes equal. When the elastic deformation amounts at both ends of the movable range are equal, the average value can be handled as the midpoint as it is, and the origin can be adjusted.

In the invention described in claim 3, after the arm is pressed against the stopper by speed control, the value of the angle detector is acquired in a state where the arm is pressed at the same motor output at both ends of the movable range.
As described above, by moving the arm by speed control, the arm can be moved to the stopper no matter where the arm is in the movable range.

  However, depending on the movable range of the arm, in other words, depending on the position where the stopper is provided, it may be difficult to achieve an equivalent pressing state at both ends of the movable range. This corresponds to the case where the weight of the arm or tool affects the pressed state.

  When the arm is in contact with the stopper, the arm and the stopper are balanced in a stationary state. Therefore, a torque corresponding to the motor output acts on a structure such as a speed reducer regardless of the posture of the robot. This torque causes elastic deformation of the structure.

  At this time, it is considered that the motor output when the arm is moved by speed control against gravity is larger than the motor output when the arm is moved by speed control along gravity. For this reason, when the stopper is provided in a positional relationship where the influence of gravity is different, even if the arm is brought into contact with the stopper by speed control, the motor output is different, so the elastic deformation at both ends of the movable range is reduced. There will be a difference.

If there is a difference in the amount of elastic deformation at both ends of the movable range, a difference also occurs at the midpoint of the acquired value of the angle detector, and the origin cannot be specified correctly.
Therefore, after the arm is pressed against the stopper by speed control, the value of the angle detector is acquired in a state where the arm is pressed with the same motor output at both ends of the movable range.

  That is, the motor output that causes elastic deformation is adjusted to be equal at both ends of the movable range. As a result, the elastic deformation caused by the motor output becomes equal at both ends of the movable range, and the average of the obtained values of the angle detectors correctly becomes the midpoint of the movable range, so that the origin can be aligned correctly.

  The invention described in claim 4 realizes a state in which the arm is pressed with the same motor output at both ends of the movable range by using the motor output when it is determined that the arm is moved by speed control and reaches the stopper. As described above, since the same pressing state can be realized by moving the arm at the same speed, the process of adjusting the motor output is performed by pressing using the motor output when it is determined that the stopper has been reached. The origin can be easily adjusted by omitting.

  The invention described in claim 5 increases the motor output by at least the amount exceeding the static friction force on the side where the influence of gravity is applied when the arm is pressed. Accordingly, it is possible to reduce the possibility of erroneous determination that the state that is not actually elastically deformed is elastically deformed, and it is possible to improve the accuracy of estimating the midpoint.

  According to the sixth aspect of the present invention, when the arm is pressed against the stopper, the motor output becomes relatively small after being pressed against the stopper on the side where the motor output becomes relatively large due to the influence of gravity. Press against the stopper. In this case, if they are pressed in the reverse order, there is a risk that the motor output will be insufficient by the amount of gravitational torque when pressed against the other end with the same force. is there. On the other hand, if the pressing is performed in the order of the present invention, since the motor output at the time of pressing first is relatively large, the pressing again becomes unnecessary and the origin can be adjusted efficiently. .

  According to the seventh aspect of the present invention, the motor output and the angle detector values obtained when the arm is pressed against the stopper a plurality of times with different motor outputs on one end side of the movable range, and the pressing is performed a plurality of times. Based on the above, the elastic deformation characteristic of the stopper on one end side showing the change in the value of the angle detector accompanying the change in motor output is obtained, and the same as the motor output when the arm is pressed against the stopper on the other end side A value of the angle detector on one end side obtained when it is assumed that the motor output is pressed against one end side is estimated based on elastic deformation characteristics.

  The stopper provided on one end side of the movable range of the arm is provided at a position where it comes into contact with the arm from below and the weight of the arm is applied in the contacted state, and is provided on the other end side of the movable range of the arm. The stopper is in contact with the arm from above, and when the stopper is provided in a positional relationship where the influence of gravity is different, such as when the weight of the arm is not applied in the contacted state. It is considered that there are items to be considered when pressing the arm against each stopper.

  Specifically, when the arm is pressed against the stopper on one end side, the influence of gravity is added, and a pressing force exceeding the motor output will work accordingly, while the arm on the stopper on the other end side When the is pressed, the pressing force obtained by subtracting the weight of the arm from the motor output is applied. In this case, since the motor output on the other end side needs to move the arm against gravity, the motor output is expected to be relatively larger than that on the one end side.

  Therefore, if you try to press against one end with the same motor output as when pressing against the other end side, in addition to the relatively large motor output and the influence of gravity, the structure of the stopper or arm And excessive force may be applied. On the other hand, if you try to press against the other end with a motor output that has a pressing force that does not interfere with the structure when pressing against one end, you cannot move the arm against gravity, There is also a possibility that it cannot be pressed against the end stopper.

In addition, considering that the influence of gravity is thought to change depending on the robot's posture and that the position of the stopper may be changed by the user, the motor output that is in the same pressing state at both ends is set in advance. It is difficult to keep.
As described above, when the stoppers are provided in a positional relationship in which the influence of gravity is different, it is expected that it is difficult to realize an equivalent pressing state at both ends of the movable range. If the pressing state at both ends is different, the amount of elastic deformation is different at both ends, so that the origin cannot be correctly aligned.

  As described above, elastic deformation is caused by applying a torque corresponding to a motor output to a structure such as a speed reducer regardless of the posture of the robot. However, it is considered that the rigidity of the arm, the stopper, and the structure itself does not change depending on the position of the stopper.

  Therefore, even if it is pressed with different motor outputs at both ends of the movable range, if the characteristics of the change in the amount of elastic deformation of the stopper accompanying the change in the motor output can be grasped, the elastic deformation when pressed with the same motor output It is considered that the value of the angle detector can be estimated in the case of the same pressing state. In other words, if the characteristics of the change in the amount of elastic deformation of the stopper can be grasped, it is considered that the origin can be aligned even when the motor is pressed with different motor outputs at both ends of the movable range.

  Therefore, paying attention to the fact that the rigidity of the arm, stopper and structure itself does not change depending on the position of the stopper, at one end where the influence of gravity is added, it is pressed multiple times with a motor output that does not affect the structure. After determining the elastic deformation characteristics of the stopper on one end side based on the acquired motor output and the value of the angle detector, and pressing the arm against the stopper on the other end side, the motor on the other end side The value of the angle detector at one end obtained when it is assumed that the motor output is the same as the output and pressed against one end is estimated based on the elastic deformation characteristics.

  This makes it possible to average the estimated value of the angle detector at one end and the measured value of the angle detector at the other end, that is, by reproducing the same pressing state at both ends of the movable range. The middle point of the range can be specified, and the origin can be adjusted. Since the stopper is pressed against the stopper on one end with a motor output that does not affect the structure, the origin can be aligned without causing deformation or damage to the arm or stopper.

The figure which shows the structure of the robot system by 1st Embodiment typically. The figure which shows the outline of the joint part of a robot typically A diagram schematically showing another configuration of the robot The figure which shows the flow of processing which acquires the value of an angle detector The figure which shows typically direction of each moment by 2nd Embodiment The figure which shows the flow which acquires the value of the angle detector The figure which shows the flow which acquires the value of the angle detector by 3rd Embodiment. Diagram showing the relationship between motor output and angle detector value The figure which shows the relationship between the difference of a motor output, and the difference of elastic deformation amount The figure which shows typically the aspect which estimates the value of an angle detector from the motor output of the other end side.

Hereinafter, a plurality of embodiments will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected and demonstrated to the site | part substantially common in each embodiment.
(First embodiment)
The first embodiment will be described below with reference to FIGS.

  As shown in FIG. 1, the robot system 1 of this embodiment includes a so-called vertical articulated robot 2 and a controller 3 that controls the robot 2. In the robot 2, a shoulder 2b connected to a base 2a via a rotation axis set in a vertical direction is coupled so as to be rotatable in a horizontal direction.

One end of the first arm 2c is coupled to the shoulder 2b so as to be rotatable in the vertical direction via a rotation shaft set in the horizontal direction. On the other hand, one end of the second arm 2d is connected to the other end side of the first arm 2c via a rotating shaft set in the horizontal direction so as to be rotatable in the vertical direction. The tool 2e is rotatably connected to the other end of the second arm 2d.
In addition, the robot 2 is provided with a stopper 4 that mechanically defines a movable range when the first arm 2c rotates vertically, for example. This stopper 4 may be called a mechanical end.

  Hereinafter, the clockwise direction shown in FIG. 1 is referred to as the forward rotation direction of the arm, the counterclockwise direction shown in the drawing is referred to as the reverse rotation direction of the arm, and the position corresponding to the stopper 4 when the arm rotates backward is defined as the lower limit of the movable range. The position corresponding to the stopper 4 when the arm rotates forward will be referred to as the upper limit of the movable range. Further, the lower limit and the upper limit of the movable range are collectively referred to as both ends of the movable range.

  The robot 2 of the present embodiment is configured to be able to attach a lower limit stopper 4a that defines the lower limit of the movable range and an upper limit stopper 4b or an upper limit stopper 4c that defines the upper limit of the movable range when forwardly rotated.

  The lower limit stopper 4a is attached to the lower end side of the shoulder 2b. The upper limit stopper 4b can be attached on the upper end side of the shoulder 2b at a position closer to the lower limit stopper 4a side than the center line when the first arm 2c is extended vertically upward. For this reason, when the movable range of the first arm 2c is defined by the lower limit stopper 4a and the upper limit stopper 4b, the movable range of the first arm 2c becomes a predetermined angle (Δ1).

  On the other hand, the upper limit stopper 4c is attachable to the lower limit stopper 4a and a position that is a line target with respect to a virtual line that extends in the vertical direction in the drawing through the rotation center of the first arm 2c on the lower end side of the shoulder 2b. . That is, the lower limit stopper 4a and the upper limit stopper 4c can be attached to the same position in the height direction of the robot 2. For this reason, when the movable range of the first arm 2c is defined by the lower limit stopper 4a and the upper limit stopper 4c, the movable range of the first arm 2c becomes a predetermined angle (Δ2). In the present embodiment, Δ2 is 180 °.

  In this case, as shown in FIG. 1, it is possible to attach a plurality of stoppers 4, but it is possible to attach only the lower limit stopper 4a and the upper limit stopper 4b, or the lower limit stopper 4a and the upper limit stopper 4c. It can also be set as the structure which can attach only. At this time, if the configuration is such that a plurality of stoppers 4 can be attached, for example, when the upper limit of the movable range is defined by the upper limit stopper 4c, the upper limit stopper 4b positioned in the middle of the movable range may be removed. Moreover, although illustration is abbreviate | omitted, it can also be set as the structure which provides the stopper 4 for prescribing | regulating the movable range of the shoulder 2b or the 2nd arm 2d.

  As shown in FIG. 2, the robot 2 includes a motor 6 that drives an arm to each rotation axis, that is, each joint portion 5, a speed reducer 7 that transmits the rotation of the motor 6 to the arm, and a rotation angle of the motor 6. An angle detector 8 or the like is provided. In the present embodiment, the angle detector 8 is constituted by an optical encoder, and outputs a value corresponding to the detected rotation angle of the motor 6, that is, the rotation angle of the arm.

  The controller 3 has a control unit configured by a microcomputer (not shown) and controls the posture and operation of the robot 2. Specifically, the controller 3 controls the rotation angle, that is, the posture and the operation of each arm by driving the motor 6 of each joint portion 5 of the robot 2. The controller 3 detects the motor output based on the motor output command value and the motor current. However, the motor output can also be detected using, for example, a torque sensor or push-pull.

  Further, as will be described later, the controller 3 drives the arm in the opposite direction by moving the arm and pressing it against the stopper 4 on one end side of the movable range, and driving the arm in the opposite direction. An average with the value of the angle detector 8 in a state of pressing against the stopper 4 is taken, and the average is set as an origin when the arm is driven.

  In addition to the robot 2 shown in FIG. 1, the robot system 1 is composed of a so-called 6-axis robot of vertical articulated type or a so-called 4-axis robot of horizontal articulated type like the robot 20 shown in FIG. You can also

  In the robot 20 shown in FIG. 3, one end of a first arm 20b is connected to a base 20a via a rotation axis (J10) set in the vertical direction so as to be rotatable in the horizontal direction. On the other hand, one end of the second arm 20c is coupled to the other end of the first arm 20b via a rotation axis (J11) set in the vertical direction so as to be rotatable in the horizontal direction. A shaft 20d that is movable in the vertical direction is connected to the other end of the second arm 20c.

  The robot 20 has a lower limit stopper that defines a movable range when the second arm 20c rotates horizontally, for example, when the clockwise rotation in the plan view is the forward rotation and the counterclockwise rotation is the reverse rotation. 4a and an upper limit stopper 4b are provided. FIG. 3 shows a state where the lower limit stopper 4a and the upper limit stopper 4b are overlapped in a side view.

  Further, the robot 20 is provided with a lower limit stopper 4a that defines the lower limit of the movable range when the shaft 20d moves in the vertical direction and an upper limit stopper 4b that defines the upper limit of the movable range. The configuration of the robot 20 illustrated in FIG. 3 is an example. Hereinafter, in the present embodiment, for the robot 2, for example, the lower limit stopper 4a and the upper limit stopper 4c are provided to perform the origin adjustment of the first arm 2c, and for the robot 20, the origin adjustment of the second arm 20c is performed, for example. An origin matching method suitable for the case will be described mainly with reference to the robot 2.

  Now, since the operation of the robot 2 is controlled based on the value of the angle detector 8, that is, the rotation angle of the arm, if there is a deviation between the value of the angle detector 8 and the actual rotation angle of the arm, The position accuracy at the time will be lowered. Therefore, in general, after assembling the robot 2, the arm is pressed against the stopper 4 at both ends of the movable range, and the origin of each joint portion 5 is adjusted based on the value of the angle detector 8 acquired in that state. It has been broken.

  At this time, in order to perform the origin adjustment, it is necessary to press the arm against the stopper 4 as a matter of course. However, since the origin has not yet been determined at the time when the origin is aligned, the position of the arm has not yet been determined. Therefore, it is difficult to perform angle control based on the rotation angle of the arm as in normal operation.

If the arm is rotated in a state where it is difficult to perform the angle control, the rotational speed and torque become excessive, and the arm and the stopper 4 may be deformed or damaged.
In addition, for example, when the origin is adjusted for maintenance at the site, it is assumed that there is no load in advance due to the influence of the weight of the tool 2e attached to the robot 2 or restrictions on the movable range allowed for the arm. There is a possibility that the arm does not move due to insufficient torque at the set motor output.

  As described above, when the origin is aligned in such a manner that the arm is pressed against the stopper 4, first, at the preparation stage before reading the value of the angle detector 8, that is, the arm is moved, for example, rotated to rotate the stopper 4. There are problems that need to be fully considered and addressed in the stage up to the point of pressing.

  Furthermore, not only in the preparation stage, but also in the stage of reading the value of the angle detector 8, there are problems that need to be fully considered and taken into account. When the arm is pressed against the stopper 4 with a constant motor output (torque), the arm is stationary with respect to the stopper 4, that is, the force is balanced. Regardless of the posture of the robot 2, only the output torque of the motor 6 acts on the structure such as the speed reducer 7 interposed therebetween.

  In this case, even if the position of the arm itself is defined by the stopper 4, as shown in FIG. 2, the value of the angle detector 8 is proportional to the backlash (D1) of the speed reducer 7 and the output torque of the motor 6. Only the elastic deformation (D2) of the structure such as the speed reducer 7 outputs a value (D3, hereinafter referred to as overshoot amount) that has passed the position where the arm stopped. In FIG. 2, the backlash portion (D1) and the elastic deformation portion (D2) are exaggerated for explanation. The backlash (D1), the elastic deformation (D2), and the overshoot amount (D3) are assumed to be positive in the forward rotation direction and negative in the reverse rotation direction.

  At this time, the backlash portion (D1) is such that the arm rotation direction, that is, the arm pressing direction is opposite in the state where the arm is pressed against the stopper 4 at the upper limit and the lower limit of the movable range, respectively. Therefore, it is considered that they are offset each other.

  On the other hand, since the elastic deformation (D2) changes according to the motor output, there is a possibility that a difference occurs in the respective elastic deformation (D2) when the arm is simply pressed against the stopper 4. There is. When a difference occurs in the elastic deformation (D2), the overshoot amount (D3) is different between the upper limit and the lower limit of the movable range, so that the position of the midpoint is shifted. That is, the origin cannot be accurately adjusted. This is because when the value of the angle detector 8 is pressed in the same direction, a difference occurs in elastic deformation in proportion to the difference in motor output (see FIG. 8 described later).

  In addition, it is also conceivable that the arm and the stopper 4 are brought into contact with each other so as not to cause elastic deformation (D2). In this case, for example, a jig such as a push-pull gauge is used to fix the stopper 4 to the stopper 4. It is necessary to detect that no force is applied, and it is difficult to carry out by the robot system 1 alone.

  Therefore, in the robot system 1, by performing the processing shown in FIG. 4, the origin is aligned without causing deformation or damage of the arm or the stopper 4 or using a jig or the like. FIG. 4 shows the flow of processing when performing origin matching. Although this process is performed by the controller 3, the robot system 1 will be mainly described for the sake of simplicity.

  When performing the origin adjustment, the robot system 1 first sets the rotation direction of the arm, that is, the pressing direction (S1). In this case, the initially set pressing direction may be either the normal rotation direction or the reverse rotation direction. Here, it is assumed that the reverse rotation direction is set. When the pressing direction is set, the robot system 1 starts speed control at the target speed (vc) (S2). That is, since the robot system 1 cannot perform the angle control as described above at the stage where the origin is adjusted, the arm is rotated by the speed control and pressed against the stopper 4.

Here, vc is a speed set when the arm is rotated. The target speed (vc) is set to a speed that does not cause damage even if it contacts the stopper 4. It should be noted that the target speed (vc) can be set by the user at the time of origin adjustment work.
In step S2, the robot system 1 waits until the arm reaches the target speed or near the target speed after starting the speed control. This is because immediately after the speed control is started, the speed of the arm is small, so that it cannot be used for the determination in step S3 described later.

  When the speed of the arm reaches the target speed or near the target speed after the speed control is started, the robot system 1 determines based on the arm operating speed (v. Angular speed) obtained from the amount of change in the value of the angle detector 8. The absolute value (| v |) of the operating speed is less than the speed decrease determination threshold (e1), or the absolute value (| vc−v |) of the difference from the target speed is greater than the speed deviation excess determination threshold (e2). Is also determined (S3).

  Here, the speed reduction determination threshold (e1) and the speed deviation excess determination threshold (e2) are thresholds for determining whether or not the arm rotating at the target speed (vc) has come into contact with the stopper 4. Further, the determination with the two types of threshold values is to enable determination according to the target speed (vc). These threshold values can be appropriately set according to the rated torque of the motor 6, the strength of the structure, the target detection time, and the like.

  For example, when the target speed (vc) is set to a relatively low speed, even if the arm contacts the stopper 4, so much force is not applied, so the speed is reduced using the speed reduction judgment threshold (e1). Is detected, it can be determined that the arm has come into contact with the stopper 4.

  On the other hand, when it is necessary to rotate the arm relatively large, it is assumed that the target speed (vc) is set at a relatively high speed. In this case, there is a possibility that the arm may collide with the stopper 4 and cause damage. However, when the operating speed (v) greatly changes from the target speed (vc) using the excessive speed deviation determination threshold (e2), the motor output is increased. It is considered that it is possible to determine that the arm contacts the stopper 4 without causing damage to the arm or the stopper 4 by releasing the speed control while fixing the value at that time.

  As described above, when the arm rotates and comes into contact with the stopper 4, the rotation of the arm stops at that time. Therefore, the robot system 1 has the operation speed (v) smaller than the speed decrease determination threshold (e1). Whether or not the arm has contacted the stopper 4 is determined on the basis of whether or not there is a deceleration exceeding the speed deviation excess determination threshold (e2).

  If the robot system 1 determines that the arm is not in contact with the stopper 4 (S3: NO), the speed control is continued. On the other hand, when the robot system 1 determines that the arm has come into contact with the stopper 4 (S3: YES), the motor output is fixed to the value at that time and the speed control is canceled (S4). In this case, the value (θa) in the state of being in contact with the lower limit stopper 4a is acquired.

  When the value of the angle detector 8 is acquired, the robot system 1 sets the pressing direction in the reverse direction, in this case, the forward rotation direction (S6), and starts speed control at the same target speed (vc) (S7). The absolute value (| v |) of the operation speed (v) is less than the speed decrease determination threshold value (e1), or the absolute value (| vc−v |) of the difference from the target speed is the excessive speed deviation determination threshold value. It is determined whether it has become larger than (e2) (S8).

  If any one of the determination conditions is satisfied, the robot system 1 fixes the motor output to the current value and cancels the speed control (S9), and contacts the value of the angle detector 8, in this case, the upper limit stopper 4c. The value (θc) in the state obtained is acquired (S10). That is, the arm is pressed by the motor output when it is determined that the arm is moved by speed control and reaches the stopper 4.

  At this time, the arm is speed controlled to the same target speed (vc) in both reverse rotation and forward rotation, and contact with the stopper 4 is determined under the same determination conditions. Therefore, the state when the arm contacts the lower limit stopper 4a is the same as the state when the arm contacts the upper limit stopper 4c. More simply, the arm whose speed is controlled comes into contact with the lower limit stopper 4a and the upper limit stopper 4c with a constant motor output, that is, with the same force applied.

  For this reason, elastic deformation by the same force occurs between the lower limit and the upper limit of the movable range, and the elastic deformation (D2) becomes the same. If the elastic deformation (D2) is the same, the angle detector 8 outputs a value obtained by adding the same overshoot amount (D3) in the opposite direction.

  If the same elastic deformation occurs at the upper limit and the lower limit of the angle range, the lower limit stopper 4a and the upper limit stopper can be accurately obtained by averaging the values (θa, θc) of the two obtained angle detectors 8. The midpoint with 4c is specified.

Therefore, the robot system 1 calculates the average of the obtained values (θa, θc) of the two angle detectors 8 as the origin (S11). Accordingly, theoretically, the origin of the angle detector 8 with respect to the arm can be accurately adjusted within the range of the dimensional tolerance of the stopper 4 and the arm, the resolution of the angle detector 8 and the variation of the motor output.
As described above, the robot system 1 according to the present embodiment performs the origin adjustment by driving the arm by the angular velocity control, more specifically by the velocity control.

According to the configuration described above, the following effects can be obtained.
The robot system 1 rotates the arm while controlling the speed and presses the arm against the stopper 4. Specifically, the amount of change in the value of the angle detector 8 when the arm is rotating, that is, the operating speed of the arm is monitored, and when the operating speed no longer changes or when the operating speed is greatly reduced. Assuming that the end of the movable range has been reached, the values of the angle detector 8 are respectively acquired from the upper limit and the lower limit of the movable range, and the average is set as the origin to perform the origin matching.

  In this case, for example, when the output of the motor 6 becomes insufficient due to the influence of the weight of the arm when the arm is rotated, the operation speed (v) gradually decreases, so that the output of the motor 6 increases to approach the target speed (vc). Therefore, if the weight of the tool 2e is equal to or less than the transportable weight, the tool 2e does not stop before reaching the end of the movable range.

  If it is determined that the stopper 4 has been reached when there is no change in the operating speed or when the operating speed has greatly decreased, the arm is pressed against the stopper 4 with a weak force regardless of the weight of the tool 2e. be able to. Then, by using the motor output when it is determined that the arm has been moved by speed control and reached the stopper 4, it is possible to realize a state in which the arm is pressed with the same motor output at both ends of the movable range.

  As a result, the value of the angle detector 8 in a state in which both ends of the movable range of the arm are pressed with the same force, that is, the angle detector 8 in the state in which the stopper 4 is excessively moved in the opposite direction by the same overshoot amount (D3). If the value can be acquired and the average value of the two values is obtained, the origin can be adjusted with the middle point of the stopper 4 at both ends of the movable range as the origin. If the origin can be aligned, the offset value of the angle detector 8 can be acquired.

Therefore, the origin can be adjusted without causing deformation or damage of the arm or the stopper 4.
In this case, the origin is not an average of the values of the angle detector 8, and an arbitrary offset value can be added so as to be convenient for the control of the robot 2, such as being set at the position of any stopper 4.

  Further, since the robot system 1 can be automatically and independently adjusted without using a jig or the like, the usability can be improved, and work at the site where the robot 2 is installed and a certain period of time have elapsed. In the subsequent maintenance, etc., the origin can be easily adjusted. In addition, since the origin can be automatically adjusted, it does not depend on the skill level of the operator.

  In addition, as in this embodiment, this method is similar to the case of the robot 2 in which the lower limit stopper 4a and the upper limit stopper 4c are provided. In the configuration in which the pressing state is the same, or in the case of the robot 20, for example, the rotation direction is limited to the horizontal direction as in the second arm 20c, that is, the gravity applied to the arm at both ends of the movable range. This is particularly significant because the origin can be adjusted without any problem when acting similarly on the torque of the motor 6.

  In addition, the robot system 1 including the controller 3 having a control unit capable of performing the origin matching process shown in FIG. 4 can perform the origin matching without causing deformation or damage of the arm or the stopper 4. The same effect as described above can be obtained.

In addition to the controller 3 exemplified in the embodiment, the controller may be configured to use a teaching pendant although not shown.
In addition, if the relationship between the motor output and the moment actually exerted on the arm is known, the rigidity of the structure such as the speed reducer 7 can be obtained. Therefore, it can be used for angle control that corrects the deflection due to its own weight. it can.

(Second Embodiment)
Hereinafter, the second embodiment will be described with reference to FIGS. 5 and 6. In the second embodiment, a method for aligning the origin when the arm rotates or moves in the vertical direction will be described. The configuration of the robot system 1 is the same as that of the first embodiment, and will be described with reference to FIGS.

  When the arm is pressed against the stopper 4 with the same motor output at both ends of the movable range, the structure such as the speed reducer 7 existing between the stopper 4 and the motor 6 balances the force in a stationary state. Regardless of the posture of the robot 2, only the output torque of the motor 6 acts. In this case, the angle detector 8 responds to the backlash (D1) of the speed reducer 7 and the elastic deformation (D2) of the structure proportional to the output torque of the motor 6, as shown in FIG. A value that passes the position of the stopper 4, that is, a value that includes the overshoot amount (D 3) is output.

  Therefore, if the same motor output is pressed at both ends of the movable range of the arm, the same amount and the overshoot amount (D3) is generated in the opposite direction. Therefore, if the average value of the angle detector 8 at both ends is obtained, The origin can be adjusted by setting the middle point of the stoppers 4 at both ends as the origin. Therefore, if the arm is pressed against the stopper 4 with the same motor output, the angle detector 8 with respect to the arm is theoretically within the range of the tolerance of the stopper 4 and the arm, the resolution of the angle detector 8 and the variation of the motor output. The origin can be adjusted accurately.

However, depending on the position of the stopper 4, it may be difficult to align the origin by pressing with the same motor output.
First, the first major reason why it is difficult to perform origin adjustment depending on the position of the stopper 4 is that it is difficult to set the motor output value to a constant value in advance.

  In order to be able to press the arm against the stopper 4 from any position within the movable range, it is necessary to set the motor output value large enough to swing out the weight of the arm. is there. However, in that case, if the stopper 4 is provided in a position other than the position where the weight of the arm becomes the maximum, the moving speed of the arm is increased by the amount that the motor output required to support the weight is reduced.

  As a result, the arm is strongly pressed by the stopper 4 and the arm and the stopper 4 may be damaged. Further, when the arm is pressed in the same direction as the weight of the arm, the arm is further strongly pressed against the stopper 4. The same applies to the method of gradually increasing the motor output.

  Specifically, for example, as shown in FIG. 5, the movable range of the first arm 2c is defined by the lower limit stopper 4a and the upper limit stopper 4b in the robot 2, or the movable range of the shaft 20d in the robot 20 shown in FIG. This corresponds to the case where the lower limit stopper 4a and the upper limit stopper 4b are used. Hereinafter, the first arm 2c and the shaft 20d will be collectively referred to as an arm for convenience.

  In the case of the robot 2 shown in FIG. 5, when the arm is moved toward the upper limit stopper 4b, the moment (M1) due to the motor output and the moment (M2) due to the weight of the arm are opposite to each other. Therefore, it is necessary to output a motor that can move the arm, more precisely, a motor output that is larger than the motor output in a posture where the weight of the arm is maximum.

  On the other hand, if the motor output is the same when the arm is moved toward the upper limit of the movable range and when the arm is moved toward the lower limit, the moment (M1) due to the motor output is generated when moving toward the lower limit stopper 4a. ) And the moment (M2) due to the arm's own weight are in the same direction, the motor output acts in the same direction as the arm's own weight, the arm moving speed becomes relatively faster and the arm's own weight is added. It will be pressed against the stopper 4a with an excessive force. In other words, the reaction force (F1) from the lower limit stopper 4a is larger than that of the upper limit stopper 4b.

  In this way, when gravity influences when moving the arm, if the same motor output is used for pressing, the motor output that can move the arm against gravity is required. Excessive force will be applied if it presses against the stopper 4 on the side where the motor output acts in the same direction as the weight of the arm.

  In order to deal with excessive force and prevent the arm and the stopper 4 from being damaged, for example, a strong structure is required. Further, if the force applied to the stopper 4 is different, the elastic deformation (D2) is different at both ends, so that an accurate origin cannot be specified.

Next, the second major reason why it is difficult to perform origin adjustment is that it is difficult to preset a relatively small value in the motor output that does not cause damage or the like.
For example, the robot 2 after shipment may be subjected to origin adjustment on site for maintenance or the like. In this case, since the tool 2e and the like are attached to the robot 2, in order to be able to move against the gravity as described above, at least the tool 2e is output compared to the origin adjustment performed at the time of shipment. Need to be larger.

  Also, depending on the relationship between the peripheral equipment and the robot 2, it is assumed that the origin cannot be adjusted in the same posture as at the time of shipment, for example, because the arm interferes, and the influence of the weight of the arm is different. Is done.

  At this time, if the motor output used for the origin adjustment at the time of shipment is insufficient or the weight of the arm and the motor output are balanced, the value of the angle detector 8 does not change before reaching the upper limit stopper 4b. There is a possibility that the wrong origin is calculated by acquiring the value of the angle detector 8 in a state where it is erroneously determined that the upper limit of the movable range has been reached.

  Therefore, in the present embodiment, by performing the processing shown in FIG. 6, it is possible to accurately perform the origin adjustment even when the weight of the arm is affected. In the process shown in FIG. 6, processes that are the same as those described in the first embodiment are given the same step numbers, and detailed descriptions thereof are omitted.

  In the process shown in FIG. 6, the robot system 1 sets the pressing direction (S1), and starts speed control at the target speed (vc) (S2). When the speed control is started and the arm speed reaches the target speed or near the target speed, the robot system 1 determines the operation speed based on the arm operation speed (v) obtained from the amount of change in the value of the angle detector 8. Either the absolute value (| v |) is less than the speed decrease determination threshold (e1) or the absolute value of the difference from the target speed (| vc−v |) is greater than the excessive speed deviation determination threshold (e2). (S3). That is, the robot system 1 moves the arm by speed control as in the first embodiment.

  If the robot system 1 determines that the arm is not in contact with the stopper 4 (S3: NO), the speed control is continued. On the other hand, if the robot system 1 determines that the arm has come into contact with the stopper 4 (S3: YES), the motor output is fixed to the value at that time, the speed control is canceled (S4), and the motor output (Pa) is acquired. After (S20), the value (θa) of the angle detector 8 is acquired (S5). That is, the robot system 1 acquires the motor output (Pa) and the value (θa) of the angle detector 8 when the arm is pressed against the stopper 4.

  Subsequently, the robot system 1 sets the pressing direction in the reverse direction (S6), starts speed control at the same target speed (vc) (S7), and the absolute value (| v |) of the operating speed (v) Is less than the speed decrease determination threshold (e1), or whether the absolute value (| vc−v |) of the difference from the target speed is larger than the speed deviation excess determination threshold (e2) (S8). .

  The robot system 1 continues the speed control when any of the determination conditions is not satisfied (S8: NO), while when any of the determination conditions is satisfied (S8: YES), the speed is increased. After canceling the control (S9), the motor output (Pb) is adjusted (S21).

  In step S21, the robot system 1 adjusts the motor output (Pb) so as to match the motor output (Pa) acquired in step S20. That is, the robot system 1 adjusts the pressing force when the arm is pressed against the stopper 4 after contacting the stopper 4 so as to be the same at both ends of the movable range.

  When the motor output is adjusted, the robot system 1 acquires the value (θb) of the angle detector 8 (S10). In this case, since the force pressing the arm against the stopper 4 is the same, the elastic deformation (D2) of the stopper 4 has the same magnitude as when the value (θa) of the angle detector 8 is acquired. Is reversed.

  Then, the robot system 1 calculates the average of the obtained values (θa, θb) of the two angle detectors 8 as the origin (S11). Accordingly, theoretically, the origin of the angle detector 8 with respect to the arm can be accurately adjusted within the range of the dimensional tolerance of the stopper 4 and the arm, the resolution of the angle detector 8 and the variation of the motor output. Note that the origin is not the average of the values of the angle detector 8, but an arbitrary offset value can be added so as to be convenient for the control of the robot 2, such as being set at the position of one of the stoppers 4.

According to the configuration described above, the following effects can be obtained.
The robot system 1 of the present embodiment acquires the value of the angle detector 8 in a state where the arm is driven by speed control and pressed against the stopper 4 and then pressed with the same motor output at both ends of the movable range.

  As a result, the arm can be pressed against the stopper 4 with a weak force without stopping before reaching the end of the movable range, and the origin can be adjusted without causing deformation or damage to the arm or the stopper 4. Thus, the same effects as in the first embodiment can be obtained.

  Moreover, since the force which presses the arm against the stopper 4 is the same on both ends of the movable range, the magnitude of each overshoot amount (D3) is the same on the lower limit side and the upper limit side, and the directions are reversed. Therefore, the origin can be specified accurately by taking, for example, the average of the values of the angle detector 8 acquired on the lower limit side and the upper limit side.

  In the embodiment, it is assumed that the motor output (Pa) is larger. In step S21, the flow of adjusting the motor output to Pa is shown. For example, a target motor output (Pc) is set in advance. In steps S20 and S21, the flow may be adjusted so that the motor output (Pc) is obtained.

  Also, once pressing the both ends of the movable range is performed, the side where the motor output is large is specified in advance, the processing of steps S1 to S5 is performed on the side where the motor output is large, and the side where the motor output is small On the other hand, it can also be set as the flow which performs the process of step S6-S10. Further, as in the third embodiment described later, in order to match the backlash at both ends of the movable range, whether the direction of the motor output (P) coincides with the pressing direction at the subsequent stage of step S6 and step S8. It is also possible to use a flow including a process for determining whether (S30, see FIG. 7).

In addition, if the relationship between the motor output and the moment actually exerted on the arm is known, the rigidity of the structure such as the speed reducer 7 can be obtained. Therefore, it can be used for angle control that corrects the deflection due to its own weight. it can.
Further, when the arm is rotated toward the upper limit stopper 4b, it is necessary to counter gravity, and therefore, it is assumed that the motor output becomes larger than that when the arm is rotated toward the lower limit stopper 4a. For this reason, the order of pressing against the upper limit stopper 4b and then pressing against the lower limit stopper 4a can reduce the possibility that the output required by the motor 6 will be insufficient, and avoid the state where remeasurement is required. .

  If a sufficient motor output is set in advance, the order of pressing against the stopper 4 can be the order of pressing against the upper limit stopper 4b and then against the lower limit stopper 4a. The order of pressing against the upper limit stopper 4b after pressing against 4a can also be adopted.

(Third embodiment)
Hereinafter, the third embodiment will be described with reference to FIGS. In the third embodiment, a method different from that of the second embodiment will be described as a method of aligning the origin when the arm rotates or moves in the vertical direction. Since the configuration of the robot system 1 is the same as that of the first embodiment, the description will be made with reference to FIGS. 1 to 3 as well, and the problems and background at the time of origin matching are the same as those of the second embodiment, so that FIG. While explaining.

  First, as described in the second embodiment, for example, as shown in FIG. 5, in the robot 2, the movable range of the first arm 2c is defined by the lower limit stopper 4a and the upper limit stopper 4b, or as shown in FIG. Assume that the robot 20 defines the movable range of the shaft 20d by the lower limit stopper 4a and the upper limit stopper 4b.

  That is, in this embodiment, the stopper 4a provided on one end side of the movable range of the arm is provided at a position where the arm comes into contact with the arm from below and the weight of the arm is applied in the contacted state. The stopper 4b provided on the other end side of the range is a state in which the arm is in contact with the arm from above, and is provided at a position where the weight of the arm is not applied in the contacted state.

  Thus, when the stopper 4 is provided in a positional relationship in which the influence of gravity is different, it is considered that there are items to be considered when pressing the arm against each stopper 4. Specifically, when the arm is pressed against the stopper 4a on the one end side, the influence of gravity is added, and a pressing force greater than the motor output acts accordingly. On the other hand, when the arm is pressed against the stopper 4b on the other end side, a pressing force obtained by subtracting the weight of the arm from the motor output is applied. In this case, since the motor output on the other end side needs to move the arm against gravity, the motor output is expected to be relatively larger than that on the one end side.

  For this reason, if the same motor output as that applied to the other end is pressed against one end, the motor output is relatively large and the influence of gravity is added. On the other hand, excessive force may be applied. On the other hand, if you try to press against the other end with a motor output that has a pressing force that does not interfere with the structure when pressing against one end, you cannot move the arm against gravity, There is also a possibility that it cannot be pressed against the end stopper. In this case, considering that the influence of gravity is considered to change depending on the posture of the robot 2 and that there is a possibility that the position of the stopper 4 may be changed by the user, the motor output that is in the same pressing state at both ends is obtained. It is considered difficult to set in advance.

  As described above, when the stoppers are provided in a positional relationship in which the influence of gravity is different, it is expected that it is difficult to realize an equivalent pressing state at both ends of the movable range. If the pressing state at both ends is different, the amount of elastic deformation is different at both ends, so that the origin cannot be correctly aligned.

  Therefore, in the present embodiment, focusing on the fact that the rigidity of the arm, the stopper 4 and other structures does not change depending on the position of the stopper 4, the origin adjustment is performed by executing the processing shown in FIG. In the process shown in FIG. 7, processes that are the same as those described in the first embodiment are given the same step numbers, and detailed descriptions thereof are omitted.

  In the process shown in FIG. 7, the robot system 1 sets the pressing direction (S1), and starts speed control at the target speed (vc) (S2). When the speed control is started and the arm speed reaches the target speed or near the target speed, the robot system 1 determines the operation speed based on the arm operation speed (v) obtained from the amount of change in the value of the angle detector 8. Either the absolute value (| v |) is less than the speed decrease determination threshold (e1) or the absolute value of the difference from the target speed (| vc−v |) is greater than the excessive speed deviation determination threshold (e2). (S3). That is, the robot system 1 moves the arm by speed control as in the first embodiment.

  If the robot system 1 determines that the arm is not in contact with the stopper 4 (S3: NO), the speed control is continued. On the other hand, when the robot system 1 determines that the arm has contacted the stopper 4 (S3: YES), it determines whether or not the direction of the motor output (P) matches the pressing direction (S30).

  When the arm is moved in the same direction as the direction in which the weight of the arm is applied, the arm angle precedes the rotation angle of the motor 6 by the backlash of the speed reducer 7 due to the weight of the arm. Therefore, immediately after the arm comes into contact with the stopper 4, the backlash does not match the state pressed against the opposite side of the movable range, so the backlash needs to be matched.

  Therefore, if the robot system 1 determines that the direction of the motor output (P) does not coincide with the pressing direction (S30: NO), the robot system 1 increases the motor output by continuing the speed control, The drive directions of the motor 6 are made to coincide.

  When the direction of the motor output (P) coincides with the pressing direction (S30: YES), the robot system 1 fixes the motor output to the current value and cancels the speed control (S4). The value (θ1) of the angle detector 8 at the motor output (P) is acquired (S31).

  Subsequently, the robot system 1 increases the current motor output (P) by α to drive the arm with the motor output (P + α) (S32), and the value (θ2) of the angle detector 8 at that time Is acquired (S33). However, the increase amount (α) of the motor output is a value sufficiently larger than the static frictional force of the joint portion 5. Accordingly, it is possible to reduce the possibility of erroneous determination that the state that is not actually elastically deformed is elastically deformed, and it is possible to improve the accuracy of estimating the midpoint.

As described above, the robot system 1 acquires the values of the angle detector 8 when they are pressed with two different pressing forces. At this time, it is assumed that the relationship between the acquired values of the two angle detectors 8 and the motor output is as shown in FIG.
Now, when pressing in the same direction, if there is no difference in motor output, it is considered that there is no difference in elastic deformation. Therefore, the relationship between the motor output and the value of the angle detector 8 shown in FIG. 8 is replaced with the relationship between the difference in motor output and the difference in elastic deformation (the amount of change in the value of the angle detector 8).

  In this case, as shown in FIG. 9, the relationship between the motor output difference and the elastic deformation difference is a proportional straight line (K) that passes through the coordinate origin and the point (α, Dα) and has an inclination of (Dα) / α. ). However, Dα = θ2−θ1. The proportional straight line (K) indicates a change in the value of the angle detector 8 with a change in the motor output, and corresponds to the elastic deformation characteristic of the stopper 4a on one end side in the present embodiment. In FIG. 9, for the sake of simplification of the description, the positive and negative states are shown. However, if the pressing direction is reversed, the sign of the difference in elastic deformation is also reversed.

  When the robot system 1 specifies the relationship between the motor output and the value of the angle detector 8, the robot system 1 sets the pressing direction to the reverse direction (S6), and starts speed control to the same target speed (vc) (S7). It is determined whether or not the stopper 4 has been touched (S8). If the robot system 1 determines that it has touched the stopper 4 (S8: YES), it continues speed control until the direction of the motor output (P) coincides with the pressing direction (S34: YES), and then the motor output is Then, the speed control is canceled (S9), and the value (θ3) of the angle detector 8 is acquired (S10). The motor output at this time is P3.

When the values of the angle detector 8 are acquired at both ends of the movable range, the robot system 1 calculates the origin (S11).
Now, the value (θ1) of the angle detector 8 acquired in step S31 which is one end side of the movable range, that is, the side where the two-stage pressing is performed, and the angle detector 8 acquired in step 10 which is the other end side. Each value (θ3) includes an elastic deformation in the opposite direction.
In this case, if the motor output is the same, there is no difference in the amount of elastic deformation as described above, so that the origin can be adjusted with the midpoint as the origin by taking the average of θ1 and θ3. .

On the other hand, when the motor output (P3) is larger than, for example, the motor output (P1), it is considered that θ3 includes an elastic deformation larger than θ1, and therefore when the average value is simply taken. In this case, the center point is shifted to the other end side, and correct origin adjustment cannot be performed.
Therefore, the robot system 1 estimates the value of the angle detector 8 on one end side obtained when it is assumed that the pressing state is the same as that on the other end side, using the relationship shown in FIG.

  Specifically, as shown in FIG. 10, the robot system 1 detects the angle detected from the relationship between the motor output on one end side and the value of the angle detector 8 when the motor output is P3. The value (θα) of the device 8 is acquired. More specifically, based on the value on the imaginary line (K2) obtained by extending the elastic deformation characteristic (K) in the motor output (P3) when pressed against the other end side, the motor output ( The value (θα) of the angle detector 8 on one end side when the arm is pressed in P3) is estimated.

  As a result, the angle detector 8 (θα, θ3) when the same pressing state is assumed at both ends of the movable range is obtained, and the same pressing state is obtained at both ends of the movable range by taking an average thereof. Find the midpoint of the case. Then, by setting the determined midpoint as the origin, the origin can be correctly aligned.

According to the configuration described above, the following effects can be obtained.
On the one end side, the robot system 1 presses the arm against the stopper 4 a plurality of times with different motor outputs, and based on the respective motor outputs and the value of the angle detector 8 acquired when the arm is pressed a plurality of times. The elastic deformation characteristic of the stopper 4a on one end side showing the change in the value of the angle detector 8 accompanying the change in motor output is obtained, and the same motor output as the motor output when the arm is pressed against the stopper 4b on the other end side. Then, the value of the angle detector 8 at one end obtained when it is assumed to be pressed against the one end is estimated based on the elastic deformation characteristics.

The robot system 1 takes the average of the estimated value of the angle detector 8 on one end side and the value of the angle detector 8 measured on the other end side, that is, the same pressing state at both ends of the movable range. By reproducing, the middle point of the movable range is specified and the origin is adjusted.
In this case, since the motor is pressed against the stopper on one end side with a motor output that does not affect the structure, the origin can be aligned without causing deformation or damage of the arm or stopper, etc. Similar effects can be obtained.

Even when the arm is affected by gravity, the value of the angle detector 8 when the same pressing state is obtained at both ends of the movable range can be obtained, so that it does not depend on the weight of the arm. In addition, the origin can be correctly aligned regardless of the position of the stopper 4.
In addition, if the relationship between the motor output and the moment actually exerted on the arm is known, the rigidity of the structure such as the speed reducer 7 can be obtained. Therefore, it can be used for angle control that corrects the deflection due to its own weight. it can.

  In this case, both the dead weight of the arm and the motor output act on the lower limit stopper 4a to which gravity is applied, but the output required for the motor 6 becomes larger in the upper limit stopper 4b that presses against gravity. Therefore, by pressing the lower limit stopper 4a once and then pressing the upper limit stopper 4b in two stages, the force applied to the structure can be reduced and damage can be further suppressed.

In addition, in the embodiment, an example in which two-stage pressing is performed has been described, but three or more levels of pressing can also be performed.
Moreover, it can also be set as the structure which estimates the value of the angle detector 8 based on the difference of the motor output changed from the state which the arm and the stopper 4 contacted.

In addition, in the embodiment, the example in which the multi-stage pressing on one end side and the estimation on the other end side are performed once is shown, but the multi-stage pressing and the estimation on the other end side can be performed multiple times. it can. Thereby, estimation can be performed from a plurality of data, and more accurate origin matching can be performed.
Moreover, it can also be set as the structure which estimates the value of the angle detector 8 based on the difference of the motor output changed from the state which the arm and the stopper 4 contacted.

Further, when the arm is rotated to the stopper 4b on the other end side after being pressed against the stopper 4a on the one end side, the time required for the rotation of the arm can be reduced by rotating the arm to the vicinity of the stopper 4 by angle control. It is also possible to shorten the work time for aligning the origin.
Further, it is possible to approximate the elastic deformation characteristic not by a straight line but by a curved line or a polynomial by pressing against one end side three times or more.

(Other embodiments)
The present invention is not limited to the configuration exemplified in each of the above-described embodiments, and various modifications, expansions, and combinations can be made without departing from the scope of the invention.
In each embodiment, the example in which the speed control is canceled when the arm contacts the stopper 4 has been described. However, the speed control can be continued even after the arm contacts the stopper. That is, the arm can be pressed against the stopper 4 with a pressing force determined by speed control. A specific processing flow in this case is a flow in which step S9 in FIGS. 4, 6, and 7 is omitted, for example.

  When the arm speed is controlled, the pressing force against the stopper 4 is determined by the arm speed. Therefore, if the arm is rotated at the same speed during forward rotation and reverse rotation, the same pressing force is applied. Thus, it is pressed against the stopper 4. And if it is the same pressing force, the amount of elastic deformation of the stopper 4 will also become the same, Therefore The center position between the stoppers 4 can be estimated, and origin adjustment can be performed.

  Further, the method of continuing the speed control even after the arm contacts the stopper is particularly useful when the situation when the arm is pressed against the stopper 4 is considered to be substantially equal. For example, as in the case of the stopper 4a and the stopper 4c shown in FIG. 1, the stopper 4 is provided symmetrically with respect to a virtual vertical line passing through the rotation center of the arm on the forward rotation side and the reverse rotation side. For example, it is considered that the arm is mechanically pressed against the stopper in substantially the same situation, and the influence of gravity is considered to be almost the same, so that the arm is pressed against the stopper 4 with the same pressing force.

  Further, when the arm is pressed against the stopper 4, after pressing against the stopper 4 on the side where the motor output is relatively increased due to the influence of gravity, the arm is applied to the stopper 4 on the side where the motor output becomes relatively small. Pushing can be performed. For example, when the movable range is defined by the stopper 4a and the stopper 4b shown in FIG. 1, the value of the angle detector 8 is acquired by pressing against the stopper 4b, and the angle detector 8 is pressed against the stopper 4a. Perform origin matching in the order of obtaining the values of.

  In this case, if they are pressed in the reverse order, there is a risk that the motor output will be insufficient by the amount of gravitational torque when pressed against the other end with the same force. is there. On the other hand, if it is first pressed against the stopper on the side where the motor output becomes relatively large due to the influence of gravity, the motor output becomes relatively large, so the motor output itself is insufficient. This can be avoided and it is not necessary to press again, so that the origin can be adjusted efficiently.

  In the third embodiment, the case where the position of the stopper 4 is greatly influenced by the gravity is illustrated. However, when the influence of the gravity is expected to be approximately the same at the stoppers 4 at both ends, the elasticity of the stopper 4 at the one end is used. It can also be set as the structure which acquires a deformation | transformation characteristic and estimates the value of the angle detector 8 of the other end side. That is, when the stoppers 4 provided at both ends of the movable range of the arm are provided at a position where the arm comes into contact with the arm from below and the weight of the arm is applied in the contacted state, the motor is different on one end side. By pressing against the stopper multiple times with the output, the elastic deformation characteristics on one end side are obtained, and from the motor output and elastic deformation characteristics when pressed against the other end side, the same pressing state as the one end side The value of the angle detector on the other end side can be estimated.

  In the drawings, 1 is a robot system, 2 is a robot, 2c is a first arm (arm), 2d is a second arm (arm), 3 is a controller (control unit), 4 is a stopper, 4a is a lower limit stopper (stopper), 4b is an upper limit stopper (stopper), 4c is an upper limit stopper (stopper), 6 is a motor, 8 is an angle detector, 20 is a robot, 20b is a first arm (arm), 20c is a second arm (arm), and 20d is A shaft (arm) is shown.

Claims (8)

In a robot having an arm driven by a motor and an angle detector for detecting a rotation angle of the motor, the movable range of the arm is mechanically defined by a stopper, for performing origin adjustment of the arm A method for aligning the origin,
The value of the angle detector in a state where the arm is moved by speed control and the arm is pressed against the stopper provided at one end of the movable range, and the arm is provided at the other end of the movable range. An origin adjustment method characterized in that the origin of the arm is adjusted by obtaining an average value with the value of the angle detector in a state of being pressed against the stopper and estimating a midpoint between the stoppers .   The origin adjustment method according to claim 1, wherein the arm is pressed against the stopper with a pressing force determined by speed control.   3. The origin according to claim 1, wherein the value of the angle detector is acquired in a state in which the arm is pressed against the stopper by speed control and is pressed with the same motor output at both ends of the movable range. How to match.   4. The state of pressing with the same motor output at both ends of the movable range is realized by using the motor output when it is determined that the arm has been moved by speed control and reached the stopper. The origin adjustment method described.   5. The origin adjustment method according to claim 3, wherein the motor output is increased by at least the amount exceeding the static friction force on the side to which the influence of gravity is applied when the arm is pressed.   When pressing the arm against the stopper, after pressing against the stopper on the side where the motor output becomes relatively large due to the influence of gravity, the pushing against the stopper on the side where the motor output becomes relatively small 6. A method for aligning the origin according to claim 1, wherein a contact is performed. In a robot having an arm driven by a motor and an angle detector for detecting a rotation angle of the motor, the movable range of the arm is mechanically defined by a stopper, for performing origin adjustment of the arm A method for aligning the origin,
The stopper provided on one end side of the movable range of the arm is provided at a position where the arm comes into contact with the arm from below and the weight of the arm is applied in the contacted state.
The stopper provided on the other end side of the movable range of the arm is in contact with the arm from above, and is provided at a position where the weight of the arm is not added in the contacted state.
On one end side, the arm is pressed against the stopper multiple times with different motor outputs,
Elastic deformation characteristics of the stopper on one end side showing a change in the value of the angle detector accompanying a change in the motor output based on each motor output and the value of the angle detector acquired when pressed multiple times Seeking
The value of the angle detector on one end side obtained when it is assumed that the arm is pressed against one end with the same motor output as when the arm is pressed against the stopper on the other end side, the elastic deformation An origin matching method characterized by estimating based on characteristics. A robot having an arm driven by a motor;
A stopper that mechanically defines the movable range of the arm;
An angle detector for detecting a rotation angle of the motor;
The value of the angle detector in a state where the arm is moved by speed control and the arm is pressed against the stopper provided at one end of the movable range, and the arm is provided at the other end of the movable range. A control unit that adjusts the origin of the arm by estimating an average value between the value of the angle detector in a state of being pressed against the stopper and estimating a center position between the stoppers;
A robot system comprising:

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