JPS5843237B2 - Robot control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a robot control system, and more particularly to a robot control system that can detect the state of a workpiece being pressed against a chuck, correct its position, and realize an optimal pressing state.

BACKGROUND OF THE INVENTION Industrial robots have been put into practical use to meet the demands for labor saving and rationalization of work in response to rising labor costs, and are proving to be very effective.

Particularly in machine factories where a large number of machine tools are installed, having industrial robots perform simple services such as replacing workpieces and tools for each machine tool has achieved remarkable effects, and the demand for this is increasing rapidly. It is increasing.

FIG. 1 shows an example of such an industrial robot, with FIG. 1A being a plan view and FIG. 1A being a side view.

Throughout the process, 1 is a mechanical hand that grips the workpieces when exchanging them, 2 is a wrist that can rotate (α axis) and swing up and down (β axis), 3 is an arm that can be extended and contracted (Tsuma axis), and 4 is a shaft. A casing that can be moved up and down (Z axis) and rotated (θ axis) relative to the PL, 5 is a frame, 6 is a teaching operation panel for teaching robot movements, 7 is an operation panel for operator operation, 8 is a teaching operation panel 6 The mechanical hand 1 sequentially memorizes teaching contents such as operation position (point), operation speed, type of service, etc. according to instructions from the mechanical hand 1.
, a control unit that controls the movements of the wrist 2, arm 3, and casing 4.

In such a playback type industrial robot, a service operation is taught in advance from the teaching operation panel 6, and the teaching contents (hereinafter referred to as robot command data) are stored in the memory in the control unit 8, and the machine side Each time a service request is made, a series of robot command data is sequentially read out and the machine is repeatedly serviced.

This robot command data consists of point information to be serviced, operation speed, service code instructing hand control at the point, signal exchange with the machine tool side, etc.

In addition, the above teaching generally includes (1) setting of a memory address where robot command data is to be stored, (2) jog feed (
(3) Setting the point position information and speed command value, (4) Setting the robot service code. By repeating the sequence of (1) to (4) above, the work is completed. A series of robot movements are taught to the machine.

Therefore, unless there is any failure in the control system or mechanism of the robot, the robot will correctly replace the workpiece, remove chips, or Performs services such as tool exchange and hand control one after another.

By the way, when attaching a workpiece to the chuck of a lathe, make sure that the end face of the workpiece and the chuck surface are parallel to each other.
And align the center line of the chuck with the center line of the workpiece (
alignment) is necessary.

This is because if alignment and centering are not done properly, the chuck will grip the workpiece in an inclined position, which will cause machining errors, resulting in defective products and breakage of the cutting tool.

Conventionally, robots have been equipped with a workpiece pressing buffer mechanism, but this has not always made it possible to chuck the workpiece accurately.

For this reason, machining is sometimes performed while the workpiece is tilted and chucked, resulting in defective products and breakage of the cutting tool as described above.

Therefore, an object of the present invention is to provide a robot control system that can detect poor pressing of a workpiece with a simple mechanism and can realize an optimal pressing state.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is an explanatory diagram showing the pressed state of the workpiece, and
1 shows a case where the pressed state is not normal, and 1 shows a case where the pressed state is normal.

In the figure, CHK1 and CHK2 are chuck claws (chuck claws), and together with another chuck claw (not shown), they constitute a three-jaw chuck.

RHL is a robot wrist, WPM is a pressing mechanism, GU is a gripping unit, and WK is a workpiece.

Now, in Fig. 2a, the chuck surface C8 and the work surface W
S is not parallel, surface matching is incomplete and workpiece WK
is leaning.

On the other hand, in Fig. 2, the chuck surface C8 and the work surface W
S is parallel, and both surface alignment and alignment are normal.

Therefore, each chuck jaw CHK1. Even if CHK2... is closed inward (in the direction of the arrow), in the case of Figure 2 a, the workpiece WK
I end up holding it at an angle.

Incidentally, in the case shown in Fig. 2, the grip can be correctly held.

Figure 3 is a state diagram when the alignment and alignment are incomplete.
In Figure a, the chuck surface C8 and the work surface WS do not coincide, and in Figure 3, the work center line WCL and the chuck center line CCL do not coincide.

FIG. 4 is a diagram showing an example of mounting a detection sensor for detecting whether the pressed state is normal.

CHK in the figure. The chuck jaw, SH, is a hole bored perpendicularly to the chuck surface C8, and WDS is a workpiece detection sensor attached to the hole SH, such as a pressure sensitive element or a limit switch.

Note that the signal line of the sensor is led out to the rear through the hole SH.

Now, in a three-jaw chuck, each chuck jaw CHK1~
A workpiece detection sensor WDS shown in FIG. 4 is attached to each CHK3 (CHK3 is not shown).

Therefore, if chucking is performed at an angle as shown in FIG. 2a, there will be a sensor that does not detect the workpiece, and abnormal chucking and how the workpiece WK is inclined will be detected.

FIG. 5 is an explanatory diagram for explaining another method of detecting whether the pressed state is normal, and the same parts as in FIG. 2 are given the same reference numerals.

In the figure, AEH, AEH2 are air injection holes hollowed out perpendicularly to the chuck surface C8, and chuck holes Ca, , CH
On the back side of K, there are air outlet holes AEHI and AEH2 at one end.
A tube TB, the other end of which is connected to a pump (not shown).

TB2 is installed.

PD, PD2 are pressure detectors for detecting back pressure, and detect the back pressure that changes when the corresponding air outlet is completely or partially blocked by a workpiece, and detects when the air outlet is blocked by the workpiece. The degree of peeling, in other words, the inclination and center deviation of the workpiece is detected.

According to this detection method, each chuck claw CHK1 to CHK
The pressure detector PD measures the degree to which the air ejection holes AEH1 to AEH3 formed in 3 are blocked by the workpiece.

~PD3 can be used to detect the pressing state of the workpiece against the chuck, for example, how it is tilted and how far the center line has deviated.

Then, by correcting the position of the gripping unit (hand) of the robot with respect to the chuck using this detection signal, an optimal pressing state can be achieved.

FIG. 6 is a block diagram of the present invention using a pressure detector having the configuration shown in FIG. 5 as a pressing state detector.

In the figure, RBC is a robot control device of Maiko 4,
It has a data memory for storing teaching data, a processing section, and a memory for storing a movement amount, a program, etc. for how to correct the robot's hand position based on the detection signal.

MAC is a machine tool, for example a lathe, and pressure detectors PD, -PD3 are attached to each chuck jaw.

RBT is a robot, HD is a hand, and AD-AD3 is an AD converter that performs AD conversion of the pressure detected by pressure detection images PD to PD3.

Now, the built-in memory of the robot controller RBC has a correspondence table (detection signal value A correspondence table of the movement amount and the movement amount is stored.

Therefore, when a detection signal value is input from the AD converters AD, to AD3 when pressing the workpiece, the robot control device first moves the hand backward by a predetermined amount and rotates or moves the hand based on the movement amount read from the corresponding table. and correct its position.

Then, by moving the workpiece forward again by the predetermined amount and pressing the workpiece against the chuck, the optimal pressing state can be changed.

Incidentally, if the optimum pressing condition cannot be obtained, the above process is repeated again.

As described above, according to the present invention, even if there is an error in teaching data or a positioning error, the pressed state of the workpiece can be detected with a simple configuration.
Moreover, since the workpiece position can be corrected to obtain the optimum pressing condition, processing defects and breakage of the cutting tool can be eliminated, and processing efficiency can be improved.

[Brief explanation of the drawing]

Figure 1 is a plan view and side view of the industrial robot, Figure 2 is an explanatory diagram of the workpiece pressing state, Figure 3 is a diagram of the state when face matching and alignment are incomplete, Figures 4 and 5 are An explanatory diagram of a configuration for detecting a pressed state, FIG. 6 is a system configuration diagram of the present invention. CHK,, CHK2... Chuck jaw, RHL.
...Robot wrist, WK...Work, G
U...Gripping unit, WPM...Pushing mechanism, WDS...Work detection sensor, PD, ~
PD3...Pressure detector, AEH, ~AEH2・
...Air outlet, RBC...Tabot control device, MAC...Machine tool, RBT...
・Robot, PA1-PA3...DA converter.

Claims (1)

[Claims] 1. In a robot control method in which a robot executes a predetermined operation based on teaching data taught in advance, a detector is provided on each chuck jaw to detect the state of pressing a workpiece to a chuck, and each chuck jaw A robot control method characterized by correcting the position of a workpiece relative to a chuck based on a signal from a detector installed in the robot. 2. The first aspect of the present invention is characterized in that each chuck jaw is provided with an air jet hole and a detector is provided to detect the degree to which the air jet hole is blocked by the workpiece.
Robot control method described in section.