JP2009028851A - Robot control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent extension of operation time by setting external force or torque applied to an attachment within an allowable range. <P>SOLUTION: This robot control device 2 includes: speed curve calculation means 21 which calculates a speed curve from the start of the operation of each joint to the termination of the operation thereof based on the position of each joint 12 when starting the operation, the position of each joint after the termination of the operation, the previously specified operation speed of each joint, and allowable torque or allowable acceleration in each joint; load calculation means 23 which calculates external force or torque applied to the attachment 18 (15, 16, 17) attached to an arm based on the speed curve calculated by the speed curve calculation means; ratio calculation means 24 which calculates the ratio of the external force or torque applied to the attachment calculated by the load calculation means with respect to the allowable external force of the attachment or the allowable torque thereof; and correction means 25 which corrects the speed curve by multiplying operation speed and operation acceleration used for calculating the speed curve by the inverse of the ratio when the calculated ratio exceeds 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a robot control apparatus that controls driving of a robot having a plurality of joints.

Industrial robots mainly consist of arm structures, and vertical articulated robots are typical structures. A servo motor is attached to each joint of such a robot, and each axis operates at an appropriate speed and acceleration / deceleration through a speed reducer (see, for example, Patent Document 1). When determining this acceleration / deceleration, it is often determined to satisfy the torque and acceleration / deceleration that the motor can output and the allowable torque and allowable acceleration / deceleration that the speed reducer attached to each shaft does not break. The robot is designed so that the robot body does not break down when it operates to satisfy the allowable torque or allowable acceleration / deceleration of the motor or reduction gear.
JP 11-33954 A

However, when a tool that can be attached to the robot body or a base that secures the signal cable attached to the tool is attached to the robot body, the tool or the base is also sufficient to prevent failure or damage due to the force or torque applied by the operation. Must be designed with sufficient rigidity.
Therefore, it is necessary to design the rigidity by estimating the worst values of acceleration and speed at which the robot operates. As a result, the rigidity becomes more than necessary in the operation other than the operation at the worst value. In addition, the torque applied to the motor and reducer increases due to the increased weight caused by increased rigidity, so the operating speed and acceleration / deceleration must be constantly reduced, and the work time is extended more than necessary. There is.

In order to deal with such a problem, in Patent Document 1 described above, when the robot is gripping a workpiece, it is proposed that the robot is operated by changing the allowable acceleration of each axis. There is no substitute for constantly decreasing the acceleration, and extension of the operating time is inevitable.
Therefore, it is necessary to keep the force and torque applied to the load attached to the tool or robot body within the allowable value, but the torque of the motor and reducer can be controlled directly by acceleration / deceleration of each joint. The external force and torque applied to the joint could not be controlled by the acceleration / deceleration of each joint.

  For example, when the tool posture is changed without changing the tool tip position very much, a force is hardly applied because the linear motion of the tool does not occur. Therefore, it is not limited by the allowable external force or allowable torque of the tool, and the robot may be operated with the allowable external force or allowable torque of each axis. However, there is a problem that the operation time is extended because the acceleration is reduced while the tool is held as in the conventional method, for example, in the case of Patent Document 1.

  Therefore, the present invention has been made to solve the above-described problem, and prevents the external force or torque applied to the tool or the like from exceeding the allowable value and prevents the operation time from being extended. An object is to provide an apparatus.

The invention according to claim 1 is a robot control apparatus for controlling driving of a robot in which a plurality of arms are rotatably connected by joints.
From the start of movement of each joint based on the position of each joint at the start of movement, the position of each joint after the movement, the movement speed of each joint specified in advance, and the allowable torque or allowable acceleration at each joint Speed curve calculation means for calculating the speed curve until the end of the operation,
Load calculating means for calculating an external force or torque applied to an attachment attached to the arm based on the speed curve calculated by the speed curve calculating means;
A ratio calculating means for calculating a ratio of an external force or torque applied to the wearing object calculated by the load calculating means with respect to an allowable external force or an allowable torque of the wearing object;
When the ratio calculated by the ratio calculation unit exceeds 1, a correction unit that corrects the speed curve by multiplying an operation speed and an operation acceleration used for calculation of the speed curve by an inverse number of the ratio;
It is characterized by providing.

The invention according to claim 2 is the robot control apparatus according to claim 1,
After calculating the velocity curve of each joint, the acceleration time and deceleration time in the velocity curve of the other joint are adjusted to the velocity curve of the one joint in accordance with the velocity curve of the one joint having the longest operation time from the operation start to the operation end. A speed curve recalculation unit is provided that recalculates the speed curve of each joint so as to coincide with the acceleration time and the deceleration time in the curve.

According to the first aspect of the present invention, the velocity curve calculating means includes the position of each joint at the start of the operation, the position of each joint after the operation, the operation speed of each joint specified in advance, and each joint. Based on the allowable torque or the allowable acceleration at, a speed curve from the start of operation to the end of operation of each joint is calculated.
Next, the load calculating means calculates an external force or torque applied to the attachment attached to the arm based on the speed curve calculated by the speed curve calculating means.
Next, the ratio calculation means calculates the ratio of the external force or torque applied to the attachment calculated by the load calculation means with respect to the allowable external force or allowable torque of the attachment.
Then, when the ratio calculated by the ratio calculation unit exceeds 1, the correction unit corrects the speed curve by multiplying the motion speed and motion acceleration used for calculation of the speed curve by the reciprocal of the ratio.
As a result, the part that reduces the operating speed and acceleration / deceleration is only when the ratio exceeds 1. Therefore, it is not necessary to constantly decrease the operating speed and acceleration / deceleration, and the work time may be extended more than necessary. Absent.
Moreover, not only can the torque of the motor and the speed reducer be controlled, but also the external force or torque applied to the attachment can be controlled.
Therefore, it is possible to prevent the external force or torque applied to the attachment from exceeding the allowable value and to prevent the operation time from being extended.

According to the second aspect of the present invention, the speed curve recalculation means calculates the speed curve of each joint after the calculation of the speed curve of each joint, according to the speed curve of the one joint having the longest motion time from the motion start to the motion end. The velocity curves of the respective joints are recalculated so that the acceleration time and deceleration time in the velocity curve of the joint coincide with the acceleration time and deceleration time in the velocity curve of one joint.
As a result, the speed curve can be recalculated according to the speed curve with the smallest acceleration / deceleration, so that the external force or torque applied to the arm or joint can be suppressed within an allowable range.

The best mode of a robot control apparatus according to the present invention will be described below in detail with reference to the drawings.
<Robot>
First, a robot whose drive is controlled by the robot control device will be described.
As shown in FIG. 1, the robot 1 is used in a spot welding line such as a body frame of an automobile, for example. The robot 1 includes a base 11 serving as a base, a plurality of arms 13 connected by joints 12, and a servo motor 14 provided at each joint 12 and connected to the joints via a speed reducer.
A spot welding gun 15 which is a tool as an attachment is provided at the distal end of the arm 13 located at the most distal end among the connected arms 13.
At least a part of the arms 13 is provided with a fixing base 17 as an attachment for fixing a signal cable 16 as an attachment connected to the servo motor 14 or the like.
Each joint 12 includes either a swing joint that supports one end of the arm 13 so that the other end can swing and a rotary joint that supports the arm 13 so that the arm 13 can rotate about its longitudinal direction. Composed. That is, the robot 1 corresponds to a so-called articulated robot.

<Robot control device>
As shown in FIGS. 1 and 2, the robot control device 2 outputs a control signal related to drive stop to the servo motor 14 in accordance with the teaching operation data of the robot 1 set by teaching or programming.
As shown in FIG. 1, the robot control device 2 includes a speed curve calculation unit 21, a speed curve recalculation unit 22, a load calculation unit 23, a ratio calculation unit 24, a correction unit 25, and a command value calculation unit 26. And a servo amplifier 27.

  The speed curve calculation unit 21 includes the position of each joint 12 at the start of the operation, the position of each joint 12 after the operation, the operation speed of each joint 12 specified in advance, and the allowable torque or allowable acceleration at each joint 12. Based on the above, a speed curve from the start of motion of each joint 12 to the end of motion is calculated. That is, the speed curve calculation unit 21 functions as a speed curve calculation unit.

For example, in the case of a 6-axis robot, the positions of the joints 12 at the start of operation are θ01, θ02,..., Θ06, and the positions of the joints 12 at the end of the operation are θ11, θ12,. Let the allowable acceleration / deceleration of the joint 12 be α1,..., Α6, and the maximum speed be v1,. It is assumed that the operation speed becomes zero at the start and end of the operation.
When the speed curve calculation unit 21 calculates the speed curve of each joint 12 based on these conditions, first, the motion amount θ1i−θ0i (i = 1,..., 6) of each joint 12 is calculated for each joint 12. Thus, a trapezoidal velocity curve as shown in FIG. 3 is created. At the time of creating the speed curve, the operation distance is obtained from the position of each joint 12 at the start of the operation and the position of each joint 12 after the operation is completed, and the operation time and the operation are determined from this operation distance and a predetermined operation speed. Calculate acceleration. The acceleration time, the constant speed time, and the deceleration time are determined so that the motion acceleration at this time is within the allowable acceleration range of each joint 12 and the arm 13 connected to the joint 12, and a speed curve as shown in FIG. Is created for each joint 12.

  The speed curve recalculation unit 22 calculates the acceleration in the speed curve of the other joint 12 in accordance with the speed curve of the joint 12 having the longest operation time from the start of the operation to the end of the operation after calculating the speed curve of each joint 12. Each speed curve is recalculated so that the time, constant speed time, and deceleration time coincide with the acceleration time, constant speed time, and deceleration time in the speed curve of one joint 12. That is, the speed curve recalculation unit 22 functions as a speed curve recalculation unit.

The speed curve shown in FIG. 3 will be described as an example. If the speed curves of the six joints 12 are 12a, 12b, 12c, 12d, 12e, and 12f, respectively, the speed curve of the joint 12 with the longest operating time is 12b. It is. Therefore, the speed curve recalculation unit 22 calculates the operation time (acceleration time, constant speed time, deceleration time) of the speed curve 12b with the operation time of the speed curves 12a, 12c, 12d, 12e, and 12f of the other joints 12 being one. The other speed curves 12a, 12c, 12d, 12e, and 12f are recalculated so as to be equal.
Thereby, a speed curve in which the acceleration time, the deceleration time, and the constant speed time of all the joints 12 as shown in FIG. 4 coincide is obtained. This speed curve satisfies the allowable acceleration and the maximum speed of all the joints 12 and operates so that each joint 12 starts to move at the same time and arrives at the same time.

  Based on the speed curve calculated by the speed curve calculation unit 21, the load calculation unit 23 applies an external force applied to the spot welding gun 15, the signal cable 16, and the fixed base 17 (hereinafter referred to as an attachment 18) attached to the arm 13. Calculate the torque. That is, the load calculation unit 23 functions as a load calculation unit. In the present embodiment, the load calculation unit 23 calculates an external force or torque based on the speed curve recalculated by the speed curve recalculation unit 22 after the speed curve calculation unit 21 calculates the speed curve.

Specifically, as shown in FIG. 4, in the speed curve of each joint 12, the attachment of the robot 1 at the speed at the start of acceleration, at the end of acceleration, at the middle of the constant speed time, at the start of deceleration, and at the end of deceleration. 18 motion speed v, motion acceleration a, motion angular velocity ω, motion angular acceleration dω are calculated. These values are calculated by the well-known Newton Euler method.
At this time, if the weight m of the attachment 18 and the inertia moment matrix are I, the force vector F and the torque vector N applied to them are
F = m · a (1)
N = I · dω + ω × I · ω (2)
Is calculated by Here, · represents multiplication, and × represents the outer product of vectors.

  The ratio calculation unit 24 calculates the ratio of the external force or torque applied to the attachment 18 calculated by the load calculation unit 23 with respect to the allowable external force or allowable torque of the attachment 18. That is, the ratio calculation unit 24 functions as a ratio calculation unit.

  Specifically, when the allowable external force of the attachment 18 is Fa and the allowable torque is Na, the ratio γ = | F | / Fa and γ = | N | / Na can be calculated. Here, | F | represents the magnitude of the force vector, and | N | represents the magnitude of the torque vector.

  When the ratio calculated by the ratio calculation unit 24 exceeds 1, the correction unit 25 corrects the speed curve by multiplying the motion speed and motion acceleration used for calculation of the speed curve by the reciprocal of the ratio. That is, the correction unit 25 functions as a correction unit.

  Specifically, when | F |> Fa or | N |> Na, γ> 1, so in this case, as the allowable external force or the allowable torque over, the reciprocal of the ratio γ / γ = Fa / | F |, 1 / γ = Na / | N | is multiplied by the operation speed so as to reduce the speed. Thereby, the external force or torque concerning the attachment 18 can be suppressed.

  The command value calculation unit 26 calculates a command value to be transmitted to the servo motor 14 based on the speed curve corrected by the correction unit 25. That is, the command value calculation unit 26 functions as command value calculation means.

  The servo amplifier 27 controls the driving of the servo motor 14 based on the command value calculated by the command value calculation unit 26.

FIG. 2 is a block diagram illustrating a configuration of the robot control device 2.
The robot control apparatus 2 includes a CPU 31 that performs each process, and a memory 32 that is executed by the CPU 31 and that stores programs for performing the above-described functions and serves as a work area for the CPU 31.
The memory 32 stores a speed curve calculation program 32a, a speed curve recalculation program 32b, a load calculation program 32c, a ratio calculation program 32d, a correction program 32e, and a command value calculation program 32f.

When the CPU 31 executes the speed curve recalculation program 32b, the robot control device 2 functions as a speed curve recalculation unit.
When the CPU 31 executes the load calculation program 32c, the robot control device 2 functions as a load calculation unit.
When the CPU 31 executes the ratio calculation program 32d, the robot control device 2 functions as a ratio calculation unit.
When the CPU 31 executes the correction program 32e, the robot control device 2 functions as a correction unit.
When the CPU 31 executes the command value calculation program 32f, the robot control device 2 functions as command value calculation means.
Further, the CPU 31 is connected to a servo amplifier 27.
In addition, each said program may be comprised separately, and may be comprised as one program.

<Processing of robot controller>
Next, the flow of control of driving of the robot 1 by the robot controller 2 will be described with reference to the flowchart of FIG.
As shown in FIG. 5, the speed curve calculation unit 21 includes the position of each joint 12 at the start of motion, the position of each joint 12 after the motion, the motion speed of each joint 12 specified in advance, and each joint. 12 is calculated based on the allowable torque or the allowable acceleration at 12 (step S1).

  Next, the speed curve recalculator 22 calculates the speed curve 12a of the other joints in accordance with the speed curve 12b of the one joint having the longest operation time from the start of the operation to the end of the operation after calculating the speed curve of each joint 12. , 12c, 12d, 12e, 12f, the speed curves 12a, 12c of the respective joints so that the acceleration time, constant speed time, and deceleration time of the joints coincide with the acceleration time, constant speed time, and deceleration time of one joint speed curve 12b. , 12d, 12e, 12f are recalculated (step S2).

  Next, the load calculation unit 23 calculates a load (external force or torque) applied to the attachment 18 attached to the arm 13 based on the speed curve calculated by the speed curve recalculation unit 22 (step S3).

  Next, the ratio calculation unit 24 is calculated by the load calculation unit 23 for the allowable external force or the allowable torque of the attachment 18 at the time of acceleration start, acceleration end, constant speed, deceleration start, or deceleration end in the speed curve. A ratio γ of external force or torque applied to the attached object 18 is calculated (step S4).

Next, the robot controller 2 determines whether or not the ratio γ calculated by the ratio calculator 24 exceeds 1 (step S5).
Here, when the robot controller 2 determines that the ratio γ exceeds 1 (step S5: YES), the correction unit 25 adds the reciprocal 1 / of the ratio to the motion speed and motion acceleration used for the calculation of the speed curve. Multiply γ to correct the speed curve (step S6).

  After the process of step S6 or when the robot control device 2 determines in step S5 that the ratio γ does not exceed 1 (step S5: NO), the robot control device 2 is an operation to calculate the ratio γ. It is determined whether the ratio γ has been calculated for all of the speed and the motion acceleration (step S7). As described above, the operation speed and the operation acceleration at which the ratio γ is calculated are the operation speed and the operation acceleration at the start of acceleration, at the end of acceleration, at the middle of the constant speed time, at the start of deceleration, and at the end of deceleration.

In step S7, when it is determined that the robot control apparatus 2 has calculated the ratio γ for all the operation speeds for which the ratio γ should be calculated (step S7: YES), the command value calculation unit 26 drives the servo motor 14. A command value, which is a control signal, is calculated based on the speed curve (step S8). Then, the command value calculated by the command value calculation unit 26 is transmitted to the servo amplifier 27, and the servo amplifier 27 controls the drive of the servo motor 14 based on the received command value (step S9).
On the other hand, when it is determined in step S7 that the robot control apparatus 2 has not calculated the ratio γ for all the operation speeds for which the ratio γ should be calculated (step S7: NO), the process returns to step S4 to return to the ratio calculation unit. 24 calculates the ratio γ of the part that has not been calculated yet.

<Effect>
As described above, according to the robot control device 2, the speed curve calculation unit 21 determines the position of each joint 12 at the start of the operation, the position of each joint 12 after the operation ends, and each joint 12 specified in advance. A speed curve from the start of operation to the end of operation of each joint 12 is calculated based on the operation speed and the allowable torque or allowable acceleration at each joint 12.
Next, the speed curve recalculator 22 calculates the speed curve 12a of the other joints in accordance with the speed curve 12b of the one joint having the longest operation time from the start of the operation to the end of the operation after calculating the speed curve of each joint 12. , 12c, 12d, 12e, and 12f so that the acceleration time, constant speed time, and deceleration time in one joint coincide with the acceleration time, constant speed time, and deceleration time in one joint speed curve 12b. , 12c, 12d, 12e, and 12f are recalculated.
Next, the load calculation unit 23 calculates an external force or torque applied to the attachment 18 attached to the arm 13 based on the speed curve calculated by the speed curve calculation unit 21 and the speed curve recalculation unit 22.
Next, the ratio calculation unit 24 calculates the ratio of the external force or torque applied to the attachment 18 calculated by the load calculation unit 23 with respect to the allowable external force or allowable torque of the attachment 18.
Then, when the ratio γ calculated by the ratio calculation unit 24 exceeds 1, the correction unit 25 corrects the speed curve by multiplying the motion speed and motion acceleration used for the speed curve calculation by the reciprocal of the ratio γ. To do.

As a result, the speed and acceleration / deceleration are reduced only when the ratio γ exceeds 1. Therefore, the operation speed and acceleration / deceleration need not be constantly reduced, and the work time may be extended more than necessary. There is no.
Further, not only the torque of the motor and the speed reducer can be controlled, but also the external force or torque applied to the attachment 18 can be controlled.
Therefore, it is possible to prevent the external force or torque applied to the attachment 18 from exceeding the allowable value and to prevent the operation time from being extended.
Further, since the speed curve recalculation unit 22 can recalculate the speed curve in accordance with the speed curve with the smallest acceleration / deceleration, the external force or torque applied to the arm 13 and the joint 12 can be suppressed within an allowable range. .

<Others>
The present invention is not limited to the above embodiment. For example, the speed curve is not always created in a trapezoidal shape, but is created in a triangular shape having no constant speed section as shown in FIG. 6 if the operating distance is small.
Even in this case, the speed curve recalculation unit 22 calculates the speed curve of each joint 12 and then adjusts the speed curve 12q of the other joint in accordance with the speed curve 12q of the one joint having the longest operation time from the operation start to the operation end. The speed curves 12p, 12r, 12s, 12t, and 12t, 12t, 12t, and 12t, 12t, 12t, 12t, 12t, 12t, 12t, 12t, 12t, 12t, 12t, 12t, 12t, 12t, 12t, 12t 12u may be recalculated.
Further, the ratio calculation unit 24 applies the load 18 calculated by the load calculation unit 23 for the allowable external force or the allowable torque of the attachment 18 at the start of acceleration, at the end of acceleration (at the start of deceleration), and at the end of deceleration in the speed curve. The external force or torque ratio γ may be calculated.
Therefore, even when there is no constant speed operation, the driving of the robot 1 can be controlled by the same control method.

The figure which shows the outline of a robot and a robot control apparatus. The block diagram which shows the structure of a robot control apparatus. The figure which shows the velocity curve of each joint. The figure which shows the speed curve after recalculation. The flowchart of the drive control of the robot by a robot control apparatus. The figure which shows the speed curve in case there are few movement amounts of a joint.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Robot 2 Robot control apparatus 12 Joint 13 Arm 15 Spot welding gun (attachment)
16 Signal cable (attachment)
17 Fixed base (attachment)
18 Wear 21 Speed curve calculation unit (speed curve calculation means)
22 Speed curve recalculation unit (speed curve recalculation means)
23. Load calculation unit (load calculation means)
24 Ratio calculation part (ratio calculation means)
25 Correction part (correction means)

Claims (2)

In a robot control apparatus for controlling the driving of a robot in which a plurality of arms are rotatably connected by joints,
From the start of movement of each joint based on the position of each joint at the start of movement, the position of each joint after the movement, the movement speed of each joint specified in advance, and the allowable torque or allowable acceleration at each joint A speed curve calculating means for calculating a speed curve until the end of the operation;
Load calculating means for calculating an external force or torque applied to an attachment attached to the arm based on the speed curve calculated by the speed curve calculating means;
A ratio calculating means for calculating a ratio of an external force or torque applied to the wearing object calculated by the load calculating means with respect to an allowable external force or an allowable torque of the wearing object;
When the ratio calculated by the ratio calculation unit exceeds 1, a correction unit that corrects the speed curve by multiplying an operation speed and an operation acceleration used for calculation of the speed curve by an inverse number of the ratio;
A robot control device comprising:   After calculating the velocity curve of each joint, the acceleration time and deceleration time in the velocity curve of the other joint are adjusted to the velocity curve of the one joint in accordance with the velocity curve of the one joint having the longest operation time from the operation start to the operation end. The robot control apparatus according to claim 1, further comprising a speed curve recalculation unit that recalculates a speed curve of each joint so as to coincide with an acceleration time and a deceleration time in the curve.

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