JPH0820893B2 - Optimal movement control method for industrial articulated robot - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a movement control system for controlling the operation of an industrial articulated robot according to a program, and in particular, it relates to a plurality of movement control systems each of which operates by receiving an output torque of a drive motor. The robot tip that holds the load work in a multi-joint robot having a robot movable part (robot axis, robot arm, robot wrist, robot hand) moves from one position to another position The output torque of each drive motor is adjusted to the optimum output torque state within the theoretical output torque determined according to the rated performance and speed conditions of each drive motor, while considering the torque interference between the drive motors that occurs due to mutual operation. , An optimal movement control method for moving and displacing the robot tip between respective positions at an ideal high speed About.

[Prior art]

An industrial articulated robot has a plurality of robot movable parts, and has a structure in which these robot movable parts are jointly coupled, and each robot movable part uses an electric motor such as a DC servo motor as a drive source to drive the robot appropriately. The drive torque is received via the transmission mechanism, the robot makes a turning motion around each joint axis, and as a result of the overall motion of each robot movable part, the robot tip,
That is, the robot hand or other tip working tool such as a welding tool is moved, displaced, or positioned between various positions in the robot operation area. At this time, for example, the first arm of the robot is pivotally attached to the upper end of the upright axis of the robot, and the second arm is pivotally attached to the tip of the first arm. When receiving the torque of the drive motor and turning around the joint axis,
In the acceleration / deceleration region of the operation process, the second arm also receives the acceleration around the joint axis to perform the turning motion. Therefore, when the turning motion is unnecessary, the reverse torque for canceling is applied. The drive motor of the second arm needs to output. In other words, the drive motor for the second arm must output an extra torque for maintaining the posture and positional relationship of the second arm as the first arm moves. This torque is generally called an interference torque. In addition, in the joint structure described above, the second arm also has the first arm in synchronization with the turning process of the first arm.
When the robot operation mode in which the second arm is swung in the direction opposite to that of the first arm is adopted, the drive motor of the second arm causes the second arm to swivel in the opposite direction together with the reverse torque accompanying the operation of the first arm. Output torque must be generated, and as a result, the drive motor of the second arm needs to generate a very large output torque. That is, also at this time, the motion of the first arm exerts an influence of torque interference on the second arm.

The existence of such torque interference has been well known in the past. On the other hand, in a conventional articulated robot, the drive motor of each robot movable part predicts the maximum value of the load applied to the movable part to predict the motor output performance. Was designed and selected. Moreover, in the robot operation program, the speed condition and time constant of each robot moving part are executed so that the taught operation program is executed in anticipation of the limit condition in which the load torque becomes approximately the maximum value in consideration of torque interference. (Time value until the speed condition is reached) is set to a constant value in the robot controller so that an alarm state does not appear due to an overload acting on each drive motor under any operating condition. Therefore, the above constant value is set to a relatively low speed value under the speed condition, and the time constant is set to a large time value.

[Problems to be solved]

However, in the above-described conventional robot movement control method, in actual robot operation, each driving part does not always operate under the above-mentioned limit conditions, and each drive motor is actually operated even if torque interference is taken into consideration. In many cases, the torque value that needs to be generated is smaller than the maximum load torque and is under a non-limit condition that is good. Here, as a general characteristic of the drive motor, the relationship between the output torque and the speed is determined by some linear equations, and when the speed value increases beyond a certain value, the output torque value tends to decrease. Are known. Therefore, under the non-limit conditions as described above, each drive motor can sufficiently perform a predetermined robot operation by generating an output torque smaller than the maximum load torque under the limit conditions. May be set to a larger value and may be performed at high speed. Nevertheless, as a result of being constrained by a constant velocity condition and a time constant, there are many cases in which the robot does not sufficiently exhibit its performance.

Accordingly, the present invention seeks to solve such problems.

[Solution means and action]

That is, the present invention is a program control method for robot operation in an industrial articulated robot in which torque interference is unavoidable, and the speed condition and time constant in the operation of each robot movable part can be changed without being restricted to a constant value. Then, the optimum speed condition and the time constant are calculated, and an operation command is issued to each drive motor system of each robot movable part based on the calculated values. That is, according to the present invention, a plurality of robot movable parts are jointly coupled to each other and a plurality of drive motors are provided, and each drive motor is provided so as to operate each corresponding movable part. In the movement control method of the industrial articulated robot that moves the robot tip to the next target position based on the motion, the load work condition and the position of each of the movable parts that are loaded on the robot tip in the memory of the robot controller in advance. Four conditions including a displacement condition, a theoretical velocity condition, and a theoretical time constant are set, and each time the robot tip is moved from one position to another position of the robot operation range according to the operation of each part of the plurality of robot movable parts. The load torque including the interference torque between the motors applied to the drive motors of the plurality of robot movable parts in the operation is set in the storage part.
The maximum torque that can be output by each drive motor is calculated by the arithmetic control means of the robot control device as a predetermined function of the theoretical speed condition of each of the movable parts. The absolute value ratio of the latter maximum torque to the load torque is obtained, and the drive motors of the plurality of robot movable units are so arranged that the absolute value ratio does not exceed 1 as much as possible and is close to 1. Optimum speed condition of each drive motor by repeating calculation from the theoretical speed condition and the theoretical time constant while changing the speed condition and the time constant respectively according to the speed condition and the variable condition of the time constant stored in advance in the storage unit. And the optimum time constant, the drive motor is operated based on the adjusted optimum speed condition and time constant, and each operation of the robot moving part is An optimum movement control method for an industrial articulated robot, characterized in that the tip of the robot is moved to a sequential position at high speed so that the maximum torque output of a corresponding drive motor is performed. is there. Hereinafter, the present invention will be described in more detail based on the embodiments shown in the accompanying drawings.

〔Example〕

FIG. 1 is a schematic mechanism diagram showing an example of an industrial articulated robot to which the optimum movement control method according to the present invention is applied and the overall configuration of its operation control mechanism, and FIG. FIG. 4 is a block diagram showing the calculation process of the load torque applied to the drive motors and the maximum torque that can be output by each drive motor. FIG. 3 is a flow chart for explaining the speed condition and time constant determination calculation process. FIG. 6 is a diagram showing a parameter table stored as a variable condition for variably controlling a speed condition and a time constant.

Referring now to FIG. 1, an articulated robot having two robot arms and a robot wrist is shown as an example of an industrial articulated robot.
The robot vertical axis 14 that is erected on the robot 12, the robot first arm 16 that is pivotally connected to the tip of the robot vertical axis 14 and is capable of turning in the depression direction shown by arrow Θ ₁ , and the robot first arm 16 tip swivel operable pivotally coupled by the arrow theta ₂ direction robot second arm 18, and a pivoting movement about robot wrist 20 is pivotally secured coupled to arrow theta ₃ direction to the tip of the robot second arm 18 It is provided as a movable part, and a robot hand 22 shown in the figure and other various working tools are replaceably attached to the tip of the robot wrist 20. The turning motion of the robot first arm 16 is generated by using the drive motor M1 as a drive source, and its position information is detected by the detector E1. Similarly, the robot second arm 18 uses the drive motor M2 as a drive source to make a rotation in the above-mentioned θ ₂ direction around the joint axis, and the position information of the robot second arm 18 is obtained from the detector E2. There is. Further, the robot wrist 20 operates using the drive motor M3 as a drive source.

The tip of the robot 10 described above, that is, the robot wrist 20.
When, for example, the robot hand attached to is moved and displaced from a certain position to another position within the operation area of the robot 10, it is achieved by the overall operation of the respective robot movable parts described above, The robot vertical axis 14 is also configured to revolve around the vertical axis with respect to the base 12 as necessary to expand the operation area. The movement displacement of the robot 10 is caused by the control command of the robot controller 30 shown in FIG. 1 being applied via the servo device 50, and as shown in the figure, the drive motors M1 ... Servo mechanisms S1, S2, S3 coupled to each of M3 are provided.

The robot controller 30 includes an arithmetic processing unit 32 and a storage unit 34.
And the program and various setting data stored in the storage device 34 of the latter is read by the arithmetic processing device 32 of the former, and a robot operation command is created based on them to the servo device 50 described above. It is configured to send out.
Teaching setting means 52 as means for teaching and setting a robot operation program or the like in the storage device 34 of the robot controller 30.
Is provided, and the control data can be input from a peripheral auxiliary storage means (not shown). Now, in the storage device 34, a program of robot operation which is taught and input by the teaching setting means 52, mainly a first memory means 36 for storing target position data for moving and displacing, and by being held at the tip of the robot Write the variable conditions such as the weight of the load work W to be processed, the distance between the center of the weight of the load work W and the output axis of the drive motor M3 of the robot wrist 20 (offset distance), and the angle deviation (offset angle). Speed conditions and time constants for actuating respective robot moving parts such as the second memory means 38, which is stored in a replaceable manner, the first and second robot arms 16, 18 and the robot wrist 20, by the corresponding drive motors M1 to M3. And the theoretical parameter of, that is,
For each robot moving part, the load torque acting on it is calculated and determined simply from the design performance conditions of the corresponding drive motor M1, M2, or M3 without considering the torque interference due to the operation of other robot moving parts. Third memory means for storing in advance the speed condition and time constant value as theoretical parameters
40, at least four storage means of a fourth memory means 42 for storing the optimum speed condition in consideration of torque interference and variable conditions for creating a time constant in a table by changing the theoretical parameters variously. Is configured.

Next, it is applied to an industrial articulated robot having the above-mentioned configuration, and each drive motor is operated efficiently in consideration of mutual torque interference between a plurality of robot moving parts, and the robot tip is operated at high speed and with high accuracy. The optimum movement control method of the present invention for moving between various positions under the position will be described.

Now, in the optimum movement control method according to the present invention, each time the tip of the robot 10 moves from one position to another, each robot movable part performs its respective movement in order to achieve that movement. A control action for adjusting and selecting the optimum speed condition and time constant of is performed.

In carrying out the control action of selecting and adjusting the optimum velocity condition and time constant, first, the load condition applied to the robot tip at the time of the moving operation, the information of the target position for moving and displacing from the current position, the theoretical speed condition, Based on a program or a set value stored in advance in the storage device 34 of the robot control device 30 such as a theoretical time constant, the movement of the movement of each of the first robot arm 16, the second robot arm 18, and the robot wrist 20 of the robot 10 is confirmed. The actual load torque applied during the execution is known Lagrangian (for example, the second memory means 38 of the storage device 34).
Is stored in ), The maximum output torque value that can be generated by the corresponding drive motors M1 to M3 when each of the robot moving parts performs the operation according to the program value and the set value. Is also calculated by the arithmetic processing unit 32 based on an equation stored in the storage device 34 as a well-known motor torque determination equation. Then, a ratio value between the absolute value of the former actual load torque value for each robot movable part and the maximum torque that can be generated by each corresponding drive motor M1, M2, M3 is calculated. That is, the former is used as the numerator and the latter is used as the denominator. When the calculation result of the ratio value exceeds the value 1, it means that the load torque exceeds the maximum torque that can be generated by the drive motor. Therefore, the speed condition and the time constant are changed to The calculation process is repeated to finally determine the optimum speed condition and time constant such that the ratio value does not exceed 1 and is as close to 1 as possible. The block diagram shown in FIG. 2 shows a process of calculating the actual load torque of each robot movable part and the maximum output torque of each drive motor described above.

The flowchart of FIG. 3 shows a process of determining the optimum speed condition and time constant based on the ratio value calculated through the calculation process shown in FIG. The determination process is also performed by the arithmetic processing unit 32 of the robot controller 30.
Needless to say, the optimum speed condition and the time constant are determined while the determination process is being performed.

Here, the flowchart of FIG. 3 will be described. In this determination and determination, according to the ratio values relating to the respective robot movable parts calculated in the calculation process of FIG.
The calculation process of sequentially determining the optimum speed condition and time constant is repeated. In the process (1) of FIG. 3, the speed condition and the time constant are set so that the ratio value does not exceed 1 and is as close to 1 as possible for the operation of the first robot arm 16. The process of adjusting and determining is shown. At this time, it is natural that the initial velocity condition and the time constant start the calculation with the theoretical velocity and the theoretical time constant described above as initial values.
Then, if the ratio value of the load torque and the maximum output torque of the drive motor is a value close to 1 or 1 under the initial value, the first robot arm 16 is set to the theoretical speed condition and the theoretical value set to the initial value. It will be operated based on the time constant. On the other hand, when the ratio value exceeds 1, the variable value, for example, the condition (A) in the parameter table of FIG. 4 which has been experimentally determined in advance is selected and the ratio value is calculated again. , The value 1 is judged, and the first
The optimum speed condition and time constant for the robot arm 16 to operate with the corresponding drive motor M1 are determined. Of course, even in the condition (A), when the ratio value exceeds 1, the condition is changed to the condition (B) or another condition, and the determination is sequentially repeated. The time constant t1 of the condition (A) means that the time constant t1 is relaxed from the theoretical time constant to a large value, and the speed condition is relaxed to 0.5 times the theoretical speed value. , Time constants (t2 to t4, 0) and speed conditions (x0.5, x0.6, x0.8, etc.) under other conditions (B) to (G)
Has the same meaning.

After the determination of the optimum speed condition and the time constant for the first robot arm 16, the optimum speed condition for the second robot arm 18 and its corresponding drive motor M2 is set in the same manner as the first robot arm 16 described above. The process of adjusting and selecting the time constant is performed as shown in processes (2) and (3) of FIG. Then, when the adjustment and selection of the optimum speed condition and time constant for the second robot arm 18 are completed, the steps (4) to (7) are similarly performed for the robot wrist 20 and the corresponding drive motor M3.
Adjustment and selection of the optimum speed condition and the time constant are carried out as shown in FIG. Since the robot wrist 20 receives torque interference from the movements of the first and second robot arms 16 and 18, there are many steps (4) to () for adjusting and selecting the optimum speed condition and time constant. FIG. 3 shows that 7) is required.
In the same sense, the process of adjusting and selecting the second robot arm 18 is
It is expected that there will be more than the adjustment and selection process of the first robot arm 16. As described above, the robot 10
When each of the robot movable parts of the robot is subject to torque interference due to the operation of other robot movable parts, it is selected and optimized after adjusting and determining the optimum speed conditions and time constants described above. Depending on the speed condition and the optimum time constant,
The drive motors M1 to M3 are driven to send a command to move each robot movable part to the servo device 50 shown in FIG. Note that, for example, even if the robot wrist 20 has a structure that is movable up and down by a drive motor, the vertical drive motor does not receive direct torque interference due to the pivoting operation of the other robot movable parts. With regard to the vertical movement of the wrist by such a drive motor, the application of the optimum movement control method according to the present invention is unnecessary.

〔The invention's effect〕

As can be understood from the above description, according to the present invention,
When a plurality of robot movable parts of an industrial articulated robot are driven by a drive motor to move, the optimum speed condition and time constant are adjusted and selected for each operation prior to the execution of that operation. Since the drive motor generates the approximately maximum output torque to drive the corresponding robot drive part, each robot movable part always receives the approximately maximum output torque of the drive motor to operate. Therefore, even if a torque interference is received, the moving operation can be achieved most efficiently under the condition of the torque interference, so that the high speed operation can be ensured, and ultimately, the robot work can be speeded up. Can be obtained. The fact that the robot moving part operates at the maximum output torque that can be exhibited by the drive motor under each operating condition means that the robot moves at an ideal operating speed. There is an advantage that the accuracy of the movement displacement of can be maintained at a high level.

[Brief description of drawings]

FIG. 1 is a schematic mechanism diagram showing an example of an industrial articulated robot to which the optimum movement control method according to the present invention is applied and the overall configuration of its operation control mechanism, and FIG. FIG. 4 is a block diagram showing the calculation process of the load torque applied to the drive motors and the maximum torque that can be output by each drive motor. FIG. 3 is a flow chart for explaining the speed condition and time constant determination calculation process. FIG. 6 is a diagram showing a parameter table stored as a variable condition for variably controlling the speed condition and the time constant. 10 ... Robot, 16 ... First robot arm, 18 ... Second robot arm, 20 ... Robot wrist, 30 ... Robot control unit, 32 ... Arithmetic processing unit, 34 ... Storage device, 36 , 38, 40, 42 ... First to fourth memory means, M1 to M3 ... Drive motors.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuhiro Yasumura 3-5-5 Asahigaoka, Hino City, Tokyo FANUC CORPORATION Product Development Laboratory (56) Reference JP-A-61-114317 (JP, A) JP Sho 62-80706 (JP, A) JP-A 61-159391 (JP, A)

Claims (2)

[Claims] 1. A plurality of robot movable parts are articulated to each other and are provided with a plurality of drive motors, each drive motor is provided so as to operate each corresponding movable part, and based on the overall operation of each movable part. In the movement control method of the industrial articulated robot that moves the robot tip to the next target position one by one, the load work condition preloaded on the robot tip in the storage unit of the robot controller and the position displacement condition of each of the movable parts, Four conditions including a theoretical speed condition and a theoretical time constant are set, and each time the robot tip is moved from one position to another position of the robot operation range according to the operation of each part of the plurality of robot movable parts, The load torque including the interference torque between the motors applied to the drive motors of the plurality of robot movable units is set in the storage unit.
The maximum torque that can be output by each drive motor is calculated by the arithmetic control means of the robot control device as a predetermined function of the theoretical speed condition of each of the movable parts. The absolute value ratio of the latter maximum torque to the load torque is obtained, and the drive motors of the plurality of robot movable units are so arranged that the absolute value ratio does not exceed 1 as much as possible and is close to 1. Optimum speed condition of each drive motor by repeating calculation from the theoretical speed condition and the theoretical time constant while changing the speed condition and the time constant respectively according to the speed condition and the variable condition of the time constant stored in advance in the storage unit. And the optimum time constant, the drive motor is operated based on the adjusted optimum speed condition and time constant, and each operation of the robot moving part is An optimum movement control method for an industrial articulated robot, characterized in that the tip of the robot is moved to sequential positions at high speed so that the maximum torque output of a corresponding drive motor is performed. 2. The speed condition and the variable condition of the time constant stored in the storage unit in advance are a ratio value with the theoretical speed condition being 1, and a time increment value with respect to the theoretical time constant, which is stored in advance in the storage unit. The optimum movement control method for an industrial articulated robot according to claim 1, wherein the optimum movement control method is stored in a table and read out.