JPH04353906A - Movement controller for mobile object - Google Patents

Abstract

PURPOSE:To shorten the moving route of a mobile object and to shorten moving time without changing the form of a moving command from a conventional form. CONSTITUTION:A moving command prereading/analyzing part 22 prereads and analyzes the moving command buffered with a moving command buffer 21. A moving command resolution part 23 resolves the moving command instructing the movement from the present point of the mobile object to a midway passing point and the moving command instructing the movement of the moving body from the midway passing point to a target point. An automatic radius adjusting part 24 adjusts the radius of a circular part when the moving route is an acute angle. A circular interpolation command generating part 26 generates the command of a straight line part for execution and the circular part when circular interpolation is available. A moving command executing part 28 executes the moving command for execution which a command buffer 27 buffers, and driving-controls a three-dimensional measurement machine.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to a movement control device for a moving body such as a measuring head of a coordinate measuring machine or a robot arm. The present invention relates to a movement control device that controls a moving object.

0002

2. Description of the Related Art In a three-dimensional measurement system, the movement of a probe is controlled by, for example, a part program of a host computer. The movement command data given from the host computer is usually data indicating the three-dimensional coordinate values of the target point to be moved and the intermediate passing points. Data on intermediate passing points is given to prevent interference between the workpiece and the probe. Controller for CNC three-dimensional measuring machine (CMMC)
ring Machine Controller) is
When movement commands are sent successively from the host computer, the movement of the probe is controlled by positioning each command.

0003

[Problem to be Solved by the Invention] However, with such a control method, since the moving direction of the probe changes after passing the halfway point, the probe must be decelerated to zero speed before and after passing the halfway point. The process of accelerating again is always performed. Therefore, there is a problem that a time loss occurs due to acceleration/deceleration processing, and the measurement time becomes longer. Such problems occur not only in CNC coordinate measuring machines but also in CNC machine tools and robots.

SUMMARY OF THE INVENTION An object of the present invention is to provide a movement control device for a moving object that can shorten the moving route and travel time of the moving object without changing the form of the movement command from the conventional one. .

[0005]

[Means for Solving the Problems] A movement control device for a moving object according to the present invention provides a movement command interpretation that interprets a movement command including coordinate values of a target point and coordinate values of passing points on the way to the target point. and movement command decomposition means for decomposing movement commands specifying a route from the current point of the moving body to an intermediate passing point and a route from the intermediate passing point to a target point, respectively, based on the interpretation result of the movement command; An arc-shaped path interpolation command that smoothly connects a movement command specifying a route including the intermediate passing point among the movement commands decomposed by this means to a path continuing from the current point and a path continuing to the target point in an arc shape. The present invention is characterized by comprising an arcuate route interpolation command generating means for replacing the arcuate path interpolation command.

[0006]

[Operation] According to the present invention, when a movement command is given, the movement command interpretation means reads it in advance and interprets it, and the movement command decomposition means determines the route from the current point to the intermediate point designated by the movement command. Each route from the intermediate passing point to the target point is decomposed. Then, the arcuate route interpolation command generation means generates an arcuate route interpolation command that allows the moving object to move smoothly along both routes in an arc shape (for example, a two-dimensional or three-dimensional arc or a parabolic shape).

Therefore, according to the present invention, in addition to shortening the moving distance of the moving object, it is also possible to suppress the acceleration and deceleration of the moving object, so that the moving time to the target position can be significantly reduced compared to the conventional method. It is possible to reduce the working time. Moreover, according to the present invention, there is no need to change the movement command itself given from the host computer compared to the conventional one, so there is no need to change the control program on the host side.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing the configuration of a three-dimensional measurement system according to an embodiment of the present invention. This system includes a host computer 1, a controller 2 and a CN
C three-dimensional measuring machine 3. The host computer 1 outputs a probe movement command according to a part program, for example. The controller 2 interprets and executes movement commands given from the host computer 1, and drives and controls the X-axis motor 17, Y-axis motor 18, and Z-axis motor 19 that drive the probe of the coordinate measuring machine 3. control processing unit 11, system management unit 12,
It is composed of a movement preprocessing section 13, a movement interpolation processing section 14, and a digital servo processing section 15.

FIG. 2 is a block diagram showing the functions of the controller 2. As shown in FIG. The movement command buffer 21 is a buffer that receives movement commands supplied from the host computer 1, and the communication control processing section 11 in FIG. 1 controls this function.

The movement command prereading/interpretation unit 22 prereads and interprets the movement commands buffered in the movement command buffer 21, and supplies only movement commands that meet various conditions such as movement distance to the movement command decomposition unit 23. The movement command decomposition unit 23 decomposes the movement command,
If the next movement command can be read in advance, this is communicated to the automatic radius adjustment unit 24, and if the movement command cannot be read in advance, this is communicated to the movement command generation unit 25 as circular interpolation is not possible. When circular interpolation is not possible, the movement command generation unit 25 generates an execution command by performing processing similar to the conventional one. The automatic radius adjustment unit 24 automatically adjusts the radius of the arc portion when the movement path is at an acute angle or the movement distance is small even if circular interpolation is possible. The circular interpolation command generation unit 26 generates movement commands for the straight line portion and the circular arc portion for execution when circular interpolation is possible. These units 22 to 26 are executed by the system management unit 12 and movement preprocessing unit 13 in FIG.

The execution movement command buffer 27 is shown in FIG.
This is a function realized by the movement interpolation processing unit 14 in which the movement commands for execution generated by the movement command generation unit 25 and the circular interpolation command generation unit 26 are buffered. The movement command execution section 28 is a section that executes the execution movement commands buffered in the command buffer 27 to drive and control the coordinate measuring machine 3, and the digital servo processing section 15 in FIG. 1 is in charge of this processing.

Next, the operation of this controller 2 will be explained. FIG. 3 is a flowchart showing the operation of the controller 2, and FIGS. 4 and 5 are diagrams for explaining a specific example of circular interpolation processing. Note that in this system, there are two cases in which the host computer 1 sequentially outputs movement commands, and
Although it is possible to deal with any case where commands are output all at once, here, as an example, a case where commands are given sequentially will be explained.

The initial value of the radius R of the arcuate trajectory may be appropriately determined based on the radius of the probe tip ball 31, the distance between the probe tip ball 31 and the workpiece 32, etc., as shown in FIG. 4, for example. For example, if the radius of the probe tip ball 31 is 1 mm and the distance between the probe 31 and the workpiece 32 is 2mm, the radius R to prevent the probe tip ball 31 and the workpiece 32 from coming into contact may be set to about 3 mm. can.

The movement commands sequentially output from the host computer 1 are sequentially stored in the movement command buffer 21, and preread and interpreted by the movement command prereading/interpretation unit 22 (S1). Now, as shown in FIG. 5, the current point of the probe tip sphere 31 is P0, and the movement command C1
Assuming that an intermediate passing point P1 is given, first, the distance L between P0 and P1 is calculated, and if this L is smaller than R, circular interpolation with radius R is impossible, so R= Set L/2 and continue processing (S2, S
3).

Next, it is determined whether the distance L specified by the movement command C1 is a distance that allows automatic circular interpolation processing to be performed sufficiently (S4). That is, probe radius 1m
m is the minimum radius value Rmin possible during circular interpolation, V is the commanded maximum movement speed at that point, and after the controller 2 receives the movement command from the host computer 1,
Assuming that the time required to interpret the command and output the automatic circular interpolation control command is t, and the safety factor is α (α≧1), the following equation 1 may be performed here.

[0016]

[Math. 1] L≧Rmin +R+V (t×α)

0017
] Note that it is difficult to specify the value of t exactly in an actual system, so the safety factor α is set to a value with some margin. If the distance L does not meet the condition of Equation 1, there is no time for circular interpolation processing, so circular interpolation processing is not performed, and movement command generation processing using the conventional positioning factor (positioning width) is executed. (S10). If the distance L satisfies the condition of Equation 1, the movement command C1
Move command C11 (P0 to P1) (P0 to P1)
A), C12 (PA ~ P1) (S5)
. PA is located in front of P1. That is, since the position of P2 is still unknown at the time when the movement command C1 is issued, the process proceeds assuming that the movement command C2 is a command for moving C1 at right angles. Only when the next command C2 (P1 to P2) is received from the host computer 1 before the current moving position enters the range of V (t+α) in front of PA, the arc command C1' (PA to PB) and A straight line command C21 (PB to PC) is generated and automatic circular interpolation is performed (S9). If there is a delay in receiving the next movement command from the host computer 1, or if the movement command instructs movement on the same straight line, circular interpolation is not performed and the probe sphere 31 moves to P1 (
S6, S10).

Even if circular interpolation is possible, for example, P in FIG.
When the movement path is at an acute angle, as in the case of point 2,
If the moving distance is short, automatic radius adjustment is performed to prevent interference with the workpiece (S7). As a result of the radius adjustment, if the radius R' becomes smaller than the probe radius of 1 mm, circular interpolation is not performed and conventional movement command generation processing is executed (S8, S10). If not, circular interpolation processing is executed (S9). By repeating the above process, it is possible to shorten the moving time of the probe by shortening the moving path of the probe and suppressing acceleration/deceleration.

According to this system, as shown in FIG.
Assuming that P0 is the current point, P1 is a passing point, and P2 is a target point, and P0 ~ P1 and P1 ~ P2 are orthogonal, the arc trajectory PA ~ PB is a straight trajectory (P
Since it is 0.785 times A ~ P1 + P1 ~ PB ), the moving distance in this part is 0.215 (PA ~
P1 + P1 ~PB).

FIG. 7 is a diagram showing a comparison of speed patterns in the case (a) when circular interpolation is not performed and the speed pattern (b) in the case (b) in the movement process shown in FIG. That is, in the conventional method shown in (a) in the figure, the speed is temporarily reduced to 0 at the intermediate passing point P1 while reaching the target point P2 from the current point P0 via the intermediate passing point P1.
It is necessary to Therefore, it takes time to accelerate and decelerate when moving the probe. On the other hand, in this method, the straight line portions P0 to PA,
It is only necessary to reduce the speed slightly more than PB ~ P2,
Since there is no need to stop the probe, the moving time of the probe can be reduced accordingly.

It should be noted that the present invention is not limited to the above embodiments. For example, positioning control may be performed using a positioning factor based on control response characteristics at the joints between a straight line and a circular arc, and between a circular arc and a straight line. If an error occurs due to the probe touching the workpiece at an arc section due to an inappropriate arc radius, etc., the system automatically switches to coordinate value control for that section and continues the movement process. good. Further, although it is known that radial deviation (shrinkage) occurs during movement on a circular arc trajectory, it is also possible to control the circular arc command by adding a correction amount in advance. In addition, since the moving speed that can be achieved in a circular arc section is different from that of a straight section in terms of the machine's acceleration resistance, acceleration/deceleration processing that is appropriate for the machine to be controlled is performed from a straight section to an arc section, and from an arc section to a straight section. This is desirable.

It goes without saying that the present invention is particularly applicable not only to the measuring head of a three-dimensional measuring machine, but also to the movement control of a robot arm and the like.

[0023]

[Effects of the Invention] As described above, according to the present invention, in addition to shortening the moving distance of a moving object, it is also possible to suppress the acceleration and deceleration of the moving object, so it takes less time to reach the target position. can be significantly shortened compared to the conventional method, and the working time can be shortened. Moreover, according to the present invention,
Since the movement command itself given from the host computer side does not need to be changed in any way from the conventional one, there is no need to change the control program on the host side.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a CNC three-dimensional measurement system according to an embodiment of the present invention.

FIG. 2 is a functional block diagram of a controller in the same system.

FIG. 3 is a flowchart showing the operation of the controller.

FIG. 4 is a diagram showing the relationship between the radius of the circular arc trajectory, the probe sphere, and the workpiece.

FIG. 5 is a diagram showing an example of a moving path of a probe.

FIG. 6 is a diagram for explaining the amount of reduction in the moving distance of the probe.

FIG. 7 is a diagram showing the relationship between the moving time and moving speed of the probe in the same system in comparison with a conventional example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Host computer, 2... Controller, 3... Three-dimensional measuring machine, 11... Communication control processing section, 12... System management section, 13... Movement pre-processing section, 14... Movement interpolation processing section, 15
...Digital servo processing section, 21...Movement command buffer, 22...Movement command prereading/interpretation section, 23...Movement command decomposition section, 24...Automatic radius adjustment section, 25...Movement command generation section, 26...Circular interpolation command generation section, 27...Movement command buffer for execution, 28...Movement command execution unit.

Claims (4)

[Claims] 1. Movement command interpretation means for interpreting a movement command including coordinate values of a target point and coordinate values of passing points on the way to the target point; movement command disassembly means for decomposing movement commands specifying a route from a point to an intermediate passing point and a route from said intermediate passing point to a target point; and said intermediate passing point among said movement commands decomposed by said means. and arcuate route interpolation command generation means for replacing a movement command specifying a route including the current point with an arcuate route interpolation command that smoothly connects the route continuing from the current point and the route continuing to the target point in an arc shape. A movement control device for moving objects. 2. The movement control of a moving object according to claim 1, wherein the movement command interpretation means is a movement command prereading/interpretation means for prereading and interpreting the movement commands sequentially transmitted from a host computer. Device. 3. The arcuate route interpolation command generation means is characterized in that it does not generate the arcuate route interpolation command when the moving distance from the current point to the intermediate passing point is shorter than a predetermined distance. A movement control device for a moving body according to claim 1 or 2. 4. The arcuate route interpolation command generation means adjusts the radius of curvature of the arcuate route in accordance with the angle formed by the travel route from the current point to the target point via intermediate passing points. A movement control device for a moving body according to any one of claims 1 to 3.