JPH081566A - Robot control device - Google Patents

Abstract

PURPOSE:To detect an execution load applied on a drive motor, and adjust an acceleration/deceleration rate at a proper value based on the execution load. CONSTITUTION:A position control part forms a speed command signal S based on a current rotation quantity and a desired rotation quantity of a drive motor 1, and a speed control part 3 forms a torque command signal T based on the speed command signal S and a current rotation speed of the drive motor 1. A power control means 4 then controls a power quantity to be supplied to the drive motor 1 based on the torque command signal T. In this constitution, a current detector 1c to detect a current through the drive motor 1 is provided, and a load operation part 8 operates an execution load rate (=execution load quantity/rated current capacity) of the drive motor 1 based on detection result of the current detector 1c to be displayed in a display means 9. thereby a worker only needs to adjust an acceleration/deceleration rate based on display on the display means 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a robot controller for performing assembly work, work transfer, box packing work (so-called palletizing work), and more particularly to controlling a drive motor for driving an arm. The present invention relates to a robot controller.

[0002]

2. Description of the Related Art For example, a control device for an industrial robot has the following structure. That is, when the rotation position detector detects the current rotation amount of the drive motor, the position control unit compares the current rotation amount with the target rotation amount and creates a speed command signal according to the difference. Next, the speed control unit compares the current rotation speed of the drive motor detected by the rotation speed detector with the speed command signal, and creates a torque command signal according to the difference. Then, the power control means supplies a current corresponding to the torque command signal to the drive motor.
As a result, the drive motor rotates by the target rotation amount at the speed corresponding to the speed command signal, and the arm moves to the target position.

Therefore, in this structure, when a disturbance such as load fluctuation occurs and the rotation amount of the drive motor decreases, the detection signal of the rotation speed detector decreases, and as a result, the torque command signal increases, The drive motor accelerates and returns to the original speed. Conversely, when the rotation speed of the drive motor increases, the detection signal of the rotation speed detector increases, and as a result, the torque command signal decreases, and the drive motor decelerates and returns to the original speed.

By the way, when actually performing an assembling work or a palletizing work using the robot having the above-described structure, there is a possibility that an excessive load may be applied to the arm due to the following reasons (1) to (3). (1) When the weight of the work to be worked is close to the payload of the robot (2) When the moment of inertia is large due to the shape of the work (3) The center of gravity of the hand or tool attached to the arm is the point of action of the arm If there is a deviation (if there is an offset)

If the load acting on these drive motors exceeds the rated capacity for a predetermined time, there is a risk of accidents such as overheating or burning of the drive motors.
When an error such as an overload error or an overheat error is detected, the power supply to the drive motor is stopped, the servo control system is cut off, and the work is interrupted.
However, in order to prevent work interruption due to error detection and further improve the safety of the device, the acceleration / deceleration rate of the drive motor must be adjusted so that the load acting on the drive motor is below the rated capacity. Is preferred. Therefore, in the conventional robot control device, the acceleration / deceleration rate is adjusted based on parameters such as the weight of the work, the moment of inertia, and the offset amount of the center of gravity position.

[0006]

However, the load acting on the drive motor depends on the rotational speed pattern given to the drive motor, the weight of the work, the shape of the work, the position where the robot grips the work, the posture of the arm, and the like. It depends on the contents of the work actually performed by the robot, and there are some parts that cannot be predicted with the above parameters alone. Therefore, in the above-mentioned conventional, the acceleration / deceleration rate tends to be lowered more than necessary so that the load acting on the drive motor does not exceed the rated capacity of the drive motor for any posture of the robot.
As a result, the working time of the robot is relatively long.

The present invention has been made in view of the above circumstances, and an object thereof is to adjust the acceleration / deceleration rate to an appropriate value according to the actual load and to shorten the working time. To provide.

[0008]

According to a first aspect of the present invention, there is provided a robot control device for producing a speed command signal for producing a speed command signal based on a current rotation amount and a target rotation amount of a drive motor for driving a robot arm. Means, torque command signal creating means for creating a torque command signal based on the speed command signal and the current rotation speed of the drive motor, and an amount of electric power supplied to the drive motor based on the torque command signal. Power control means for controlling, current detection means for detecting current flowing in the drive motor, and execution load calculation means for calculating the execution load of the drive motor based on the detection result of the current detection means. It has a unique feature.

According to a second aspect of the present invention, there is provided a robot control device, wherein a speed command signal generating means for generating a speed command signal based on a current rotation amount and a target rotation amount of a drive motor for driving a robot arm, and the speed command. Torque command signal creating means for creating a torque command signal based on a signal and the current rotation speed of the drive motor, and power control means for controlling the amount of power supplied to the drive motor based on the torque command signal. And an execution load calculating means for calculating an execution load of the drive motor based on the torque command signal.

In this case, a display means for displaying the calculation result of the execution load calculation means is provided (claim 3), a calculation start command for causing the execution load calculation means to start calculation, and a calculation end for ending the calculation. Arithmetic instruction setting means for setting an instruction before and after an arbitrary work sequence data area may be provided (claim 4).

[0011]

According to the means of claim 1, the execution load of the drive motor is calculated based on the current flowing in the drive motor, and according to the means of claim 2, the load is supplied to the drive motor. The execution load is calculated based on the torque command signal. Therefore, in any of the first and second means, it is sufficient to adjust the acceleration / deceleration rate of the drive motor based on the execution load. Therefore, the acceleration / deceleration rate is set to an appropriate value according to the actual load. Therefore, the work time of the robot can be shortened.

According to the means described in claim 3, since the calculation result of the execution load calculating means is displayed on the display means, the acceleration / deceleration rate can be adjusted based on this display. According to the means described in claim 4, when the operation start instruction and the operation end instruction are set before and after the arbitrary work sequence data area, the execution load operation means starts the operation upon detection of the operation start instruction and ends the operation. The operation is terminated when the instruction is detected. Therefore, the execution load can be calculated for any work desired by the worker.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will now be described with reference to FIGS.
It will be described based on. First, in FIG. 1 schematically showing the overall configuration, a drive motor 1 is for driving an arm of a robot. The drive motor 1 includes a rotational position detector 1a and a rotational speed detector 1b. And current detector 1
and c are connected. The rotational position detector 1 a detects the amount of rotation of the drive motor 1, and the detection result of the rotational position detector 1 a is output to the position controller 2. The rotation speed detector 1b detects the rotation speed of the drive motor 1, and the detection result of the rotation speed detector 1b is output to the speed control unit 3. The current detector 1c corresponds to the current detecting means according to claim 1, detects the current flowing through the drive motor 1, and outputs the detection result I to the current controller 4a.

The storage unit 5 stores teaching position data and work order data, and the arithmetic unit 6 is
The teaching position data and the work sequence data are read, and the target movement amount for each arm is calculated based on the both data. Then, the target movement amount calculated by the calculation unit 6 is output to the position control unit 2, and the position control unit 2 compares the detection result of the rotational position detector 1a with the target movement amount, and the position that is the difference between the two. The speed command signal S is created based on the deviation. That is, the position control unit 2 corresponds to the speed command signal generating means in claim 1. The speed command signal S created by the position control unit 2 is output to the speed control unit 3. Then, the speed control unit 3 compares the detection result of the rotation speed detector 1b with the speed command signal S, and creates the torque command signal T proportional to the difference between the two. That is, the speed control unit 3 corresponds to the torque command signal generating means in claim 1.

The torque command signal T generated by the speed control section 3 is output to the electric power control means 4. The power control means 4 is composed of a current control section 4a and a power amplification section 4b, and the current control section 4a is based on the detection result of the current detector 1c and the torque command signal T. A current command signal indicating the current value to be supplied to 1 is created and output to the power amplification unit 4b. Then, the power amplifier 4b
By supplying a current proportional to the current command signal to the drive motor 1, the drive motor 1 is rotated by the target rotation amount at the speed corresponding to the speed command signal S, and the arm is moved to the target movement position. The current command signal is limited so as not to exceed the maximum allowable current value of the drive motor 1.

The detection result I of the current detector 1c is output to the A / D converter 7, converted into a digital signal by the A / D converter 7, and then output to the load calculator 8. The load calculation unit 8 calculates an execution load ratio (= rated current value of the driving motor 1 / execution load amount of the motor 1) corresponding to the execution load according to claim 1 based on the detected current I. Corresponds to the execution load calculation means according to claim 1. Moreover, the execution load factor calculated by the load calculation unit 8 is output to the display unit 9 such as a display, and the display unit 9 is displayed.
Displayed by. Further, the arithmetic instruction setting means 10 is connected to the storage unit 6. This arithmetic command setting means 10
Is an instruction word (for example, robot language) that represents an operation start instruction and an operation end instruction before and after an arbitrary work sequence data area.
As will be described later, the load calculation unit 8 starts the calculation of the execution load factor upon detecting the calculation start command set by the calculation command setting means 10, and then ends the calculation. The calculation is ended upon detection of.

Next, the processing contents of the load calculator 8 will be described with reference to FIG. A series of work of the robot is
The teaching position data and the work sequence data are set in the work program. However, when a timer interrupt occurs at a constant sampling time t during such a series of work, the load calculation unit 8 , Step S
It shifts to 1 and determines whether or not to start the calculation. This step S1 is for detecting the command word set by the calculation command setting means 10, and the load calculation unit 8
If the command word "load calculation start" is not detected,
The determination is "NO" and the process proceeds to step S2. This step S2 is for detecting "load calculation in progress". Since the load calculation is not started here and is not "load calculation in progress", it is judged "NO" and the next timer interrupt Will be waiting for.

Thereafter, when the load computing unit 8 detects the command word "load computing start" in step S1,
It judges "YES" and moves to step S3. Then, N is initialized (N = 0), and in step S4,
Initialize ISUM (ISUM = 0). Here, N is the number of samplings of the calculation, and ISUM is the current detector 1c.
Is the square I ² of the detected value I. The load calculation unit 8
When the SUM is initialized, the process proceeds to step S5, the detected value I of the current detector 1c is taken in, and in step S6,
Calculate “ISUM ← ISUM + I ² ”. here,
It becomes "ISUM ← 0 + I ² ". Then, step S7
, And calculate “N ← N + 1”. Here, "N
← 0 + 1 ”. After calculating “N ← N + 1”, the load calculation unit 8 proceeds to step S8. This step S
Reference numeral 8 is for detecting an instruction word representing "computation end" set by the operation instruction setting means 10, and when the work based on the work sequence data is being executed, the command word is detected. Instead, the load calculation unit 8 determines “NO”, and the load calculation work ends for one control cycle.

After that, when a timer interrupt occurs, the load computing section 8 returns to step S1 again. Here, since the work based on the work order data is being executed,
The command word indicating "start of calculation" is not detected, and "NO" is determined and the process proceeds to step S2. In this case, since the load is being calculated, it is determined to be "YES" and the process proceeds to step S5. Then, the detected value I of the current detector 1c is taken in, and in step S6, "ISUM ← ISUM + I ² " is set, and in step S7, "N ← N + 1" is set, and then
In step S8, it is determined to be "NO", and the calculation work ends for two control cycles.

While the above operation is repeated, when the predetermined work sequence data area ends and the command word indicating "completion of operation" is detected, the load operation unit 8 determines "YES" in step S8. , And proceeds to step S9. Then, first, "ISUM ^(1/2) " is calculated and divided by the operation execution time (t × N) obtained by multiplying the sampling time (timer interrupt time) t by the sampling number N, The root mean square value “ISUM ^(1/2) / (N × t)” of the current value I flowing through the drive motor 1 (that is, the execution load amount) is obtained. Next, in step S10, the execution load factor α is calculated by dividing the execution load amount by the rated current value Io of the drive motor 1, and the execution load factor α is displayed on the display means 9. Generally, the load acting on the motor can be expressed by multiplying the equivalent DC machine resistance of the motor by the square of the current value flowing in the motor. Therefore, the time average value of the current value I ² flowing in the motor is calculated, and the time It can be obtained by calculating the ratio of the average value to the rated capacity Io, that is, the execution load factor.

According to the above embodiment, the execution load factor α (execution load amount / rated capacity) of the drive motor 1 is calculated based on the detection result of the current detector 1c, and the calculation result is displayed on the display means 9. Since it is displayed, if the acceleration / deceleration rate is adjusted based on this display, the acceleration / deceleration rate is set to an appropriate value according to the actual load, and as a result, the working time is shortened. Moreover, since the arithmetic instruction setting means 10 for setting the arithmetic start instruction and the arithmetic end instruction before and after the arbitrary work sequence data area is provided, the execution load factor α can be calculated for an arbitrary work desired by the worker. , The usability is improved.

Various algorithms are conceivable for adjusting the acceleration / deceleration rate, and an example thereof will be described below.
First, the following three items are listed as prerequisites prior to adjustment. a) The maximum value of the acceleration / deceleration rate is 100%. b) The execution load factor α is approximately proportional to the acceleration / deceleration rate. c) Exclude workpieces that have less than the rated load capacity and no offset specified in the robot specifications (that is, if the load is less than the rated load capacity and have no offset, there is a problem even if the acceleration / deceleration rate is 100%). Absent). The above precondition is based on the following equation. T = J × β W = (T ² ) ^(1/2) where T is the torque of the drive motor 1, J is the moment of inertia, β is the angular acceleration, and W is the actual load amount.

Therefore, the execution load factor α is detected for the work having the offset larger than the rated load capacity, and the calculation result is displayed on the display means 9. For example, when the acceleration / deceleration rate is 50% and the display on the display unit 9 is 80%, there is a margin in the execution load rate, so the acceleration / deceleration rate is increased to about 60% and the execution load rate is detected again. Then, the adjustment work of the acceleration / deceleration rate is repeated until the execution load rate falls within the range of 90 to 100%, and the acceleration / deceleration rate is set to an appropriate value according to the actual load.

Next, a second embodiment of the present invention will be described with reference to FIGS. 3 and 4. The same members as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.
Only different members will be described. In this case, as shown in FIG. 3, the load calculation unit 8 ′ is provided in the speed control unit 3 and is configured to calculate the execution load factor based on the torque command signal T generated by the speed control unit 3. ing. That is, the load calculation unit 8'corresponds to the execution load calculation unit according to the second aspect.

According to this configuration, as shown in FIG. 4, when a timer interrupt occurs at a constant sampling time t,
The load calculation unit 8 ′ detects an instruction word indicating “load calculation start” (step Q1) and initializes N (step Q1).
3), TSUM is initialized (step Q4). Here, “TSUM = torque command signal T ² ”. next,
The load calculation unit 8 ′ reads the torque command signal T (step Q5), and “TSUM ← TSUM + T ² ” (step Q5
6) and "N ← N + 1" (step Q7). After that, when an instruction word indicating “load calculation end” is detected, the process proceeds from step Q8 to Q9, the square root of TSUM is calculated, and then the square root is divided by the calculation execution time (N × t) to execute. Obtain the load amount, and step Q10
In, the execution load factor α is calculated by dividing the execution load amount by the rated current value Io and displayed on the display means 9.

The current control of the drive motor 1 is performed according to the torque command signal T, as described in the first embodiment. Therefore, as in the first embodiment, the actual load factor α can be calculated based on the torque command signal T without actually measuring the value of the current flowing through the drive motor 1. The present embodiment is based on such an idea, and since the worker can adjust the acceleration / deceleration rate based on the execution load factor α, as in the first embodiment, the acceleration / deceleration rate can be adjusted. Becomes an appropriate value according to the execution load, and as a result, the work time is shortened.

In the first and second embodiments, the operator adjusts the acceleration / deceleration rate based on the execution load rate α, but the acceleration / deceleration rate is automatically adjusted based on the execution load rate α. It may be configured to. In this case, the acceleration / deceleration rate adjusting means for automatically adjusting the acceleration / deceleration rate based on the execution load factor α is configured by software, and the work performed by the worker in the first and second embodiments is performed by the acceleration / deceleration rate adjusting means. To act on your behalf.

Further, the worker may adjust the acceleration / deceleration rate based on the execution load amount. In this case, the operator calculates the execution load factor α based on the execution load amount and the rated current capacity, and thereafter performs the adjustment work in the same procedure as in the first and second embodiments. Therefore, as the software configuration of the load calculation units 8 and 8 ', step S10
And Q10 (execution load factor calculation step) are abolished, and the execution load amount calculated in steps S9 and Q9 corresponds to the execution load in the claims. Further, the acceleration / deceleration rate may be automatically adjusted based on the execution load factor calculated by the worker. In this case, the operator calculates the execution load factor based on the execution load amount and the rated current capacity, and inputs the execution load factor into the acceleration / deceleration rate adjusting means, thereby performing the adjustment work in the acceleration / deceleration rate adjusting means. Let it be done.

[0029]

As is apparent from the above description, the robot controller of the present invention has the following excellent effects. According to the means described in claims 1 and 2, since the execution load of the drive motor can be detected, the acceleration / deceleration rate of the drive motor can be adjusted based on the execution load. As a result, the acceleration / deceleration rate can be set to an appropriate value according to the actual load, and the work time can be shortened.

According to the third aspect, the calculation result of the execution load calculating means can be displayed on the display means, so that the acceleration / deceleration rate can be adjusted based on this display. According to the means described in claim 4, since the calculation start instruction and the calculation end instruction can be set before and after the arbitrary work sequence data area, the execution load can be calculated for the arbitrary work desired by the worker. And the usability is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a flowchart showing the control contents of the load calculation unit.

FIG. 3 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 4 is a view corresponding to FIG.

[Explanation of symbols]

1 is a drive motor, 1c is a current detector (current detecting means), 2 is a position control section (speed command signal creating means), 3 is a speed control section (torque command signal creating means), 4 is power control means, 8 Is a load calculation unit (execution load calculation unit), 8'is a load calculation unit (execution load calculation unit), 9 is a display unit, and 10 is a calculation instruction setting unit.

Claims (4)

[Claims] 1. A speed command signal generating means for generating a speed command signal based on a current rotation speed and a target rotation speed of a drive motor for driving a robot arm, the speed command signal and a current speed of the drive motor. A torque command signal creating unit that creates a torque command signal based on the rotation speed, a power control unit that controls the amount of power supplied to the drive motor based on the torque command signal, and a current flowing through the drive motor. A robot control device comprising: a current detection unit that detects the current; and an execution load calculation unit that calculates the execution load of the drive motor based on the detection result of the current detection unit. 2. A speed command signal generating means for generating a speed command signal based on a current rotation speed and a target rotation speed of a drive motor for driving a robot arm, the speed command signal and a current speed of the drive motor. Torque command signal creating means for creating a torque command signal based on the rotation speed, power control means for controlling the amount of power supplied to the drive motor based on the torque command signal, and based on the torque command signal A robot controller, comprising: an execution load calculation means for calculating an execution load of the drive motor. 3. The robot controller according to claim 1, further comprising display means for displaying a calculation result of the execution load calculation means. 4. An arithmetic instruction setting means for setting an arithmetic start instruction for causing the execution load arithmetic means to start an arithmetic operation and an arithmetic end instruction for ending the arithmetic operation before and after an arbitrary work sequence data area. The robot controller according to claim 1, wherein the robot controller is a robot controller.