JPH086628A - Planning and generating method for movement command with limit of increased increased acceleration - Google Patents

Abstract

PURPOSE:To perform smooth operation without generating an unplesant shock sound and vibration at start time and stop time by determining the value of a time parameter within limits previously set as to increased increased acceleration, increased acceleration, and acceleration, and further integrating the increased increased acceleration in four or three stages and obtaining the movement command. CONSTITUTION:In the memory of a CNC 10, operation patterns are prepared as to the increased increased acceleration regarding axis movement so that the time parameter is included. Then the limit values are set for the increased increased acceleration, increased acceleration, and acceleration. The value of the time parameter is determined within one of the limit values and further the increased increased acceleration is integrated in four or three stages to obtain the movement command. A signal of this movement command is sent to a common RAM 11. The CPU of a digital servo circuit 12 which drives respective axis motors 13, on the other hand, reads the movement command out of the common memory 11 in specific cycles to generate position command signal for the respective axes. Therefore, the unpleasant shock noise and vibration can be suppressed even at the start time and stop time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for planning / creating a movement command in an automatic machine controlled by a numerical controller such as a machine tool or a robot, and more specifically, it has a speed limit. It relates to a method for planning and creating movement commands.

[0002]

2. Description of the Related Art In an automatic machine such as a machine tool or a robot, a flexure caused by a speed reducer or a low rigidity member is provided between an object to be controlled (table, arm, etc.) and an actually controlled object (motor). Intervenes. Normally, when there is no friction, the torque required for the motor is calculated by the load inertia and the acceleration, but when there is a deflection between the motor and the controlled object, the speed is further increased (second floor related to acceleration time). Differentiation) requires torque.

In particular, since the acceleration is small at the start of acceleration and the start of deceleration, the motion state of the controlled object such as the work table and the robot arm is governed by the torque due to the additional speed. Therefore, even if the acceleration and jerk (first differential with respect to time of acceleration) are limited when planning and creating movement commands in these automatic machines, it is sufficient to realize the intended smooth movement. Not necessarily.

That is, according to the conventional method, a variable θ1 representing the position of the object to be controlled (work table, arm tip, etc.).
, For the variable θm representing the motor position, assuming the relationship of the following expression (i) (there is no deflection between the motor position and the desired control object), the following equation (ii ), The torque that the motor can output is divided by the inertia to plan and create a movement command that limits the acceleration. In this case, the maximum speed to be controlled is naturally limited by the maximum speed of the motor. The symbols in the following formulas are used in the following meanings.

Θ1: Position of control target (workpiece, arm tip, etc.) [rad] θm: Motor position [rad] J1: Load inertia [Kg · cm / (rad / s ² )] Jm: Motor inertia [Kg・ Cm / (rad / s ² )] u: Torque input [Kg ・ cm]

[0006]

[Equation 1] However, as described above, in reality, since the flexure due to the speed reducer, the low rigidity member, etc. is interposed between the control target (table, robot arm, etc.) and the actually controlled motor, the above (i) The assumption of the formula does not hold, and the acceleration does not hold the simple proportional relationship like the formula (ii).

Now, a system including non-rigid elements such as a speed reducer, a table, and a robot arm is considered as a vibration system, and modeling is performed by a spring-damper system as shown in FIG. Here, the meanings of the symbols K and D are as follows. K: Spring constant [Kg · cm / rad] D: Viscosity coefficient [Kg · cm / rad] When the equation of motion is drawn focusing on the motor side, the following (1)
While the formula is obtained, focusing on the load side, the following formula (2) is obtained. Further, it is understood that the expression (3) is obtained from the expression (2), and the existence of the flexure generated between the motor position and the position of the control target object at the time of acceleration / deceleration is expressed. Also,
When the equation (3) is modified, the following equation (4) is obtained, while
Equation (1 ′) is obtained from equation (1). By substituting the equation (1 ′) into the equation (4), the equation (5) is obtained. And
Substituting the second-order derivative of equation (4) into equation (5) yields equation (6).

[0008]

[Equation 2] The underlined term on the right side of the equation (6) represents the contribution of the incremental velocity to the torque input. Normally, when the automatic machine is started and stopped, the acceleration becomes a value close to 0, so the torque due to this additional speed gives a shock to the machine,
Smooth start / stop will not be possible. That is, according to the conventional method, even if a movement command is planned / created with a strict limitation on acceleration, no additional condition is imposed to suppress the speed. It was difficult to avoid a phenomenon in which a torque command due to various speeds was suddenly generated in the servo control system, and the shock propagated to the entire automatic machine to cause unpleasant shock noise and vibration.

[0009]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an automatic machine such as a machine tool or a robot which operates in response to a movement command planned / created by a numerical control device even at the time of starting or stopping. Another object of the present invention is to provide a method of planning / creating a movement command that enables a smooth operation without an unpleasant impact sound or vibration.

[0010]

As a means for solving the above-mentioned problems of the prior art, the invention of the present application is to provide an operation pattern in the numerical control device regarding an additional speed relating to axis movement in a form including a time parameter. Prepared in advance, speed gradually,
A numerical value characterized in that a movement command is obtained by determining the value of the above-mentioned time parameter under preset limits for jerk and acceleration and further integrating the jerk by four or three orders. A method for planning / creating a movement command having a limit to the incremental velocity in an automatic machine controlled by a controller "(Claim 1; when limiting values for the incremental velocity and acceleration are provided) and" a form including a time parameter. In the numerical control device, an operation pattern for increasing speed related to axis movement is prepared in advance, and the value of the above-mentioned time parameter is set under the preset limit for increasing speed and acceleration, and further It is characterized in that the movement command is obtained by integrating the speeds into the fourth or third order.
Method of planning / creating movement command having limit to additional speed in automatic machine controlled by numerical control device "(Claim 2; Limit value is provided for acceleration but no limit value is provided for additional speed) (If provided).

[0011]

According to the invention of the present application, first, an operation pattern for an additional speed relating to axis movement is prepared in a memory of a numerical control device (CNC, robot controller, etc.) for controlling a machine tool or a robot including a time parameter. Then, a limit value is set in advance for the “increasing speed, the increasing speed and acceleration” or the “increasing speed and the acceleration”.

When planning / creating a movement command, the arithmetic unit (CPU) in the numerical control device determines the value of the time parameter under any one of the above-mentioned limiting conditions, and further increases the speed by fourth integration or A movement command is obtained by integrating the third order.

This movement command is "acceleration and acceleration".
Alternatively, not only the "acceleration" but also the incremental speed is planned and created so that it does not exceed a certain upper limit, so when the machine tool or robot is operated according to the movement command, the motor and work table, the robot Even if a non-rigid element such as a mechanical transmission system (speed reducer, ball screw, etc.), a work table, or the robot arm itself is interposed between the arm tip and the like, the torque component caused by the above-mentioned additional speed is not generated. Since it is suppressed, impact noise and vibration are less likely to occur in the machine at the time of starting or stopping.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 2 is a block diagram showing the basic construction of a machine tool control system which is normally used. Further, FIG. 3 is a block diagram briefly showing a control loop of each axis control executed by the system shown in FIG.

In FIG. 2, the CPU incorporated in the CNC designated by the reference numeral 10 sequentially reads the program data stored in the memory in the CNC 10 and reads each axis (for example, X
The same applies to axes, Y-axis, C-axis, etc. The necessary interpolation calculation is performed on the data of 1) and the movement command signal of each axis is sent to the shared RAM 11 every predetermined period.

On the other hand, the CPU of the digital servo circuit 12 that drives each axis motor 13 reads out this movement command from the shared memory 11 in a predetermined cycle and generates a position command signal for each axis. For each axis, the deviation between the position command value and the current position detected by the encoder 14 of each axis is used as the position loop input.

Position loop processing P based on such an input
With respect to the speed command signal Vc generated by L, the deviation from the current speed Vc corresponding to the differential value of the position detection output of the encoder 14 is calculated and is input to the speed loop processing VL.

In the speed loop processing VL, a torque command Tc is generated, a drive current corresponding to the torque command Tc is supplied to the motor M through the servo amplifier, the motor rotates, and a required portion 1 of the machine tool (for example, workpiece). The desired position control for the table) is achieved.

In the following, as one embodiment of the present invention, the required portion 1 of the machine tool in the above system is started from a first position θr1 on one axis (here, θr), and a second position θr2. Move to and stop (100%
A method of planning / creating a movement command in the case of performing (positioning) will be described.

First, in the form shown in FIG. 4A, an operation pattern for the incremental velocity with respect to θr (fourth derivative with respect to time t) is prepared in the memory of the CNC 10. If the integration is sequentially performed starting from this pattern, the jerk, the acceleration, the speed, and the position shown in FIGS.
It is possible to obtain an operation pattern such as FIG. 4 (A)
The values of the parameters t1 to t4 and the integration constants for each integration included in the pattern shown in (4) are determined so as to match the movement conditions desired to be realized.

In FIGS. 4 (B) to 4 (E), each movement pattern is drawn assuming that an integration constant is determined so that the following condition is satisfied at t = 0 (at the time of starting) as a moving condition to be realized. Has been. Position θr = θr1 Velocity θr ^(・) = Acceleration θr ^{(・ ・)} = jerk θr ^{(・ ・ ・)} = 0 where symbols ^(・) to ^{(・ ・ ・)} are first-order derivatives with respect to time to 3
It was used as a symbol to express the differential.

Further, parameters b (maximum jerk), c (maximum acceleration), d (command speed) and e (moving distance, here | θ) included in each pattern of FIGS. 4B to 4E.
r2- [theta] r1 |) is described as follows by the parameters t1 to t4 and a included in the pattern of FIG.

B = a * t1 c = b * (t1 + t2) = a * t1 ² + a * t1 * t2 d = c * (2 * t1 + t2 + t3) = 2 * a * t1 ³ + 2 * a * t1 ² * T2 + a * t1 ² * t2 + a * t1 * t2 ² + a * t1 ² * t3 + a * t1 * t2 * t3 = 2 * a * t1 ³ + 3 * a * t1 ² * t2 + a * t1 * t2 ² + a * t1 ² * t3 + a * t1 * t2 * t3 e = d * (4 * t1 + 2 * t2 + t3 * t4) = 8 * a * t1 ⁴ + 12 * a * t1 ³ * t2 + 4 * a * t1 ² * t2 ² + 4 * t1 ³ * t3 + 4 * a * t1 ² * t2 * t3 + 4 * a * t1 ³ * t2 + 6 * a * t1 ² * t2 ² + 2 * a * t1 * t2 ³ + 2 * a * t1 ² * t2 * t3 + 2 * a * t1 * t2 ² * t3 + 2 * a * t1 ³ * t3 + 3 * a * t1 ² * t2 * t3 + a * t1 * t2 ² * t3 + a * t1 ² * t3 ² + a * t1 * t2 * t3 ² + 2 * a * t1 ³ * t4 + 3 * a * t1 ² * t2 * t4 + a * t1 * t2 ² * t4 + a * t1 ² * t3 * t4 + a * t1 * t2 * t3 * t4 = 8 * a * t1 ⁴ + 16 * a * t1 ³ * t2 + 6 * a * t1 ³ * t3 + 2 * a * t1 ³ * t4 + 10 * a * t1 ² * t2 ² + a * t1 ² * t3 ² + 9 * a * t1 ² * t2 * t3 + 3 * a * t1 ² * t2 * T4 + a * t1 ² * t3 * t4 + 2 * a * t1 * t2 ³ + 3 * a * t1 * t2 ² * t3 + a * t1 * t2 * t3 ² + a * t1 * t2 ² * t4 + a * t1 * t2 * t3 * t4 Then, depending on various conditions imposed when planning / creating a movement command, the following 1. ~ 4. The values of t1 to t4 are determined as follows. 1. The maximum value of the incremental speed shall be given in advance (as will be described later, it can be adjusted if a good result is not obtained). That is, a = amax. 2. From the command speed d and the moving distance e, the moving time T1 is T
1 = e / d = t1 + t2 + t3 + t4. 3. It is assumed that the maximum value c of acceleration is set in advance, as is the case with the conventional method. Then, as the command speed d specified by the operation program, the acceleration time T
2 is defined by T2 = d / c = 2 * t1 + t2 + t3. 4. When setting a limit value for jerk, maximum acceleration c
From the maximum jerk limit value b, T3 = c / b = t1 +
It becomes t2. If no limit value is set for the jerk, t2 = 0 can be set. Then, the above equation c
= A * t1 ² + a * t1 * t2 t2 and t2 = 0, and t1 = | (c / a) ^1/2 | t2 = 0.

Therefore, the outline of the processing flow for planning / creating a movement command in the CNC 10 is as shown in FIG.

[1] When the jerk has a limit value b (Yes in step M1) First, in step S1, the parameter t1 is calculated from the maximum jerk amax and the maximum jerk b by the following equation. In t1 [sec] = b [rad / s 3] / amax [rad / s 4] the following step S2, the maximum acceleration c and maximum jerk b, calculates the parameters t2 by the following equation. t2 [sec] = (c [ rad / s 2] / b [rad / s 3]) - t1 Further, in step S3, the command speed d and the maximum acceleration c, calculates a t3 by the following equation. t3 [sec] = (d [ rad / s] / c [rad / s 2]) - 2 * t1 -t2 Then, the moving distance e (= at step S4 | θr2-θr1
|) And the commanded speed d, t4 is calculated by the following equation. t4 [sec] = (e [rad] / d [rad / s])-4 * t1 -2 * t2-t3 The above processing of steps S1 to S4 results in t1
When ~ t4 is obtained, the incremental velocity θr ^{(...) is set} to 4
The floor command is integrated to obtain the movement command θr (step S
5). When creating a movement command for each sample time, the third order integration is sufficient. Note that ^(...) Was used as a symbol representing the fourth derivative with respect to time.

At this time, the following equations (7) to (9) are calculated.

[0027]

(Equation 3) [2] When there is no limit value for jerk (No in step M1) Instead of step S1, t2 = 0 is set in step S1 ′, and the parameter t1 is calculated from the maximum acceleration c and the maximum jerk amax. Calculate by formula. t1 [sec] = | (c [rad / s 2] / amax [rad / s 4]) 1/2 | Then, in step S3 below, as in the case where the jerk of [1] is limited value The movement command θr
Or get θ r ^(·) . In addition, ^(•) is used as a symbol representing the first derivative with respect to time.

The process of planning / creating a movement command for the movement of one axis of the machine tool has been described above. However, when planning / creating a movement command for the movement of two or more axes of the machine tool or robot, The above-described method may be repeatedly applied to each interpolation section obtained by interpolating the movement route taught by the operation program.

Although it is practically difficult to know in advance the optimum set values of the maximum jerk amax, the maximum jerk b, and the maximum acceleration c, it is necessary to set appropriate values in view of experience. However, if you try to actually operate the machine tool or robot and you do not get a good result, adjust each setting value and set a setting value that creates a more preferable movement command. Can be done. Depending on the combination of these set values, there is a possibility that negative ones may be mixed in the time parameters t2 to t4 obtained from the above calculation results. As a method for dealing with such a situation, for example,
After the step S5 of the above flow chart, a step of checking that t2 to t4 are not negative is added, and these t
It is conceivable to generate an alarm signal to stop the machine and prompt the operator to reset the set value when a negative one is mixed in 2 to t4.

[0030]

According to the present invention, in an automatic machine such as a machine tool or a robot which operates in response to a movement command planned / created by a numerical controller, a motor and a position control target portion (moving table, It is possible to suppress an unpleasant impact sound or vibration caused by the presence of the non-rigid element between the arm tips and the like). In particular, smoothing of the operation at the time of starting and stopping can be easily achieved, which is a characteristic not seen in the conventional technique.

[Brief description of drawings]

FIG. 1 is a diagram showing a state in which a system including a motor and a non-rigid element such as a reducer, a table, and a robot arm is considered as a vibration system and is modeled by a spring-damper system.

FIG. 2 is a block diagram illustrating a basic configuration of a machine tool control system that is normally used.

FIG. 3 is a block diagram briefly showing a control loop of each axis control executed by the system shown in FIG.

FIG. 4 is a time chart explaining an operation model of a machine tool prepared in one embodiment of the present invention.

FIG. 5 is a flowchart showing an outline of a flow of a movement command planning / creating process in the embodiment.

[Explanation of symbols]

 10 CNC 11 Shared memory 12 Digital servo circuit 13 Each axis drive motor 14 Encoder

Claims (2)

[Claims] 1. A numerical control device is provided with an operation pattern for an incremental velocity related to axis movement in a form including a time parameter, and a preset limit for the incremental velocity, the incremental velocity and the acceleration is set. In the automatic machine controlled by the numerical controller, the movement command is obtained by determining the value of the above-mentioned time parameter and further integrating the speed by fourth or third order integration. A method for planning and creating movement commands with speed restrictions. 2. A numerical control device is provided with an operation pattern for an incremental velocity relating to axis movement in a form including a time parameter, and the above-mentioned pattern is provided under a preset limit for the incremental velocity and acceleration. Limiting the incremental speed in an automatic machine controlled by a numerical controller, characterized in that a movement command is obtained by defining a value of a time parameter and further integrating the incremental speed by fourth or third order integration. How to plan and create a move command you have.