JPH0248923B2 - DAIREKUTOTEIICHINGUGATAROBOTSUTONOSEIGYOSOCHI - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a direct teaching robot, and more particularly to a control device for a direct teaching robot that is designed to eliminate instability in control caused by a reduction gear or the like interposed in a drive system.

Generally, in the case of a direct teaching robot, the drive system between the power source and the robot element is interrupted by some means to stop the drive source in order to reduce the movement of the robot elements such as wrists and arms during teaching. The robot element must be able to be easily moved by the operator while remaining in place.

For example, when a robot arm 1 is rotated by a motor M as shown in FIG. 1, a clutch 2 is interposed between the arm 1 and the motor M, and when teaching, the arm 1 is
is separated from the resistance caused by the motor M and the speed reducer 3, which is a transmission device, and is made lighter. And conventionally arm 1
There is one position detector such as a pulse encoder for detecting the position of , and one position detector E1 performs position detection during teaching and position detection during playback.
Therefore, in order to detect the rotational position of the arm during teaching, the position detector E1 was generally provided on the arm 1 side, that is, between the clutch 2 and the arm 1.

However, in the conventional automatic control system shown in Fig. 1, when this is visualized as a block diagram, as shown in Fig. 2, the motor transfer function Gm and the mechanical The transfer functions GL of the system are connected in series, and the combined transfer function of the two is the product. If the mechanical system is soft and the natural frequency of the transfer function is low, an oscillation phenomenon will occur when the loop gain is increased, causing control to fail. Becomes unstable. The step response example of the control system shown in Figure 1 above is shown in Figure 3.
It is shown in FIG. FIG. 3 shows a case where the gain is low, and FIG. 4 shows a case where the gain is slightly increased. It can be seen that the vibration increases over time and becomes uncontrollable.

Therefore, in order to solve the above-mentioned problems with the conventional control system, the inventors of the present application have developed a system in which the delay in control in the conventional direct teaching robot allows position detection in both the teaching and reproducing modes to be performed at a single position. Focusing on the fact that the detector is also used as a detector, in addition to the first incremental detector that is provided between the robot element and the clutch mechanism and detects the rotational position of the robot element, A second incremental type detector connected to the drive source is provided to detect the rotational position of the drive source, and the first and second detectors are selectively connected to the drive source in the teaching mode and in the playback mode. We have created a robot control device equipped with switching means connected to the control means, and have already filed an application. According to this control device, during teaching, by disengaging the clutch, the first
Using the detector, teaching operation can be performed in a light movement state, and during playback, the rotation speed of the drive source can be feedback-controlled by the second detector installed on the drive source side. As shown in Figure 5, automatic control targeting only the motor transfer function Gm becomes possible, and it is not affected by the transfer function GL of the mechanical system consisting of transmission devices such as reducers, so the control during regeneration is stable. , there is no oscillation even when the loop gain is increased, and the impulse response is as shown in Figure 6. For the same gain as the response shown in Figure 4, the oscillations quickly attenuate, compared to the conventional one. Compared to the above, extremely good response was obtained.

The remaining problem with this improved robot control device is that since it is essential to use an incremental position detector, if the switching means is to be switched only once, the first detector on the robot element side and Even if there is a slight phase difference between the pulses generated by the second detector on the drive source side, almost no errors will occur, but as the number of switching increases, the errors will accumulate and become impossible to ignore, and the This means that solute type detectors cannot be used.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a control device for a direct teaching type robot which is capable of control with fewer errors and can also use an absolute type detector.

In order to achieve the above object, the control device for a direct teaching robot of the present invention includes a first detector provided on the output side of a transmission device including a clutch mechanism, which detects the rotational position of a robot element, and a first detector that detects the rotational position of a robot element. provided on the input side of the transmission device including,
In addition to a second detector for detecting the rotational position of the drive source and a switching means for switching and selectively deriving the first detector output and the second detector output, the first detector further includes a second detector for detecting the rotational position of the drive source; transfer means for transmitting the detector output to the second detector; and in the teaching mode, the switching means is switched to the first detector output side, and upon receiving the output, the taught position of the robot element is stored and reproduced. In the mode, the transfer means is energized to transfer the first detector output to the second detector as the initial value of the second detector, and the switching means is switched to the second detector.
control means for controlling switching to the detector output side of the detector and feeding back a signal corresponding to the second detector output and the stored first detector output at the time of teaching to the drive source. It is characterized by

Hereinafter, the present invention will be explained in more detail with reference to embodiments shown in the drawings.

FIG. 7 is a block diagram of a control device for a direct teaching robot showing an embodiment of the present invention. In the same figure, 1, 2, 3 and M are
The robot arm, clutch, reducer, and motor are similar to those shown in FIG. Directly attached to the robot arm 1, the robot arm 1
The output end of the first detector E1, which is an incremental pulse encoder for detecting the rotational position of the motor, is connected to the switching terminal a of the switching circuit 5 via a first pulse counter 4 such as an up-down counter. The output end of the detector E2 shown in FIG. 2, which is an incremental pulse encoder that detects the rotation angle and is attached to the motor M, is connected to the switching terminal b of the switching circuit 5 via a second pulse counter 6 such as an up-down counter. has been done. A common terminal c of the switching circuit 5 is connected to the control circuit 7 and to one end of the input of the comparator 8. The other end of the comparator 8 is connected to the control circuit 7, and receives the target signal θin of the arm 1 sent from the control circuit 7 and the motor M signal applied via the switching terminal b and common terminal c of the switching circuit 5. The rotational position signal θm is compared, and the difference is converted into an analog quantity by a D/A converter 9, and then amplified by an amplifier 12 and applied to the motor M. Note that T in the figure detects the speed with a tachometer generator and feeds it back to the amplifier 12.
The count value of the first pulse counter 4 is configured to be transferable to the second pulse counter 6 via the transfer circuit 10. Note that the switching operation of the switching circuit 5 and the transfer operation of the transfer circuit 10 are performed by a switching command CS and a transfer command TS from the control circuit 7. Further, the control circuit 7 is constituted by a microcomputer. The switching circuit 5, pulse counters 4 and 6, comparator 8, transfer circuit 10, and other circuits are configured externally to the control circuit 6, that is, the microcomputer, but the functions of these circuits are realized by internal processing of the microcomputer. You may.

The operation of the control device configured as described above will be explained in the teaching mode and the reproducing mode.

When the control circuit 7 is set to the teaching mode by operating a mode changeover switch (not shown), the common terminal c of the changeover circuit 5 is switched to the changeover terminal a by the changeover command signal CS (for example, signal "0") from the control circuit 7. Connected. Also, a command signal to turn clutch 2 off.
Rs is issued and clutch 2 is also released. In this state, the arm 1 can be manually rotated by the operator, and the amount of rotation is detected as a pulse signal by the incremental first pulse encoder E1. Such an incremental type pulse encoder is well known. For example, in the case of a photoelectric type, it has two rows of slits on a rotating disk at regular intervals and slits whose phase is shifted by 90 degrees with respect to the slits. A type that can discriminate the direction of rotation and outputs a 0 signal (hereinafter referred to as a Z signal) every rotation can be used. For example, an up-down counter used in the pulse counter 4 that receives pulse signals from the pulse encoder E1 for counting is well-known, and is equipped with an up-pulse input terminal, a down-pulse input terminal, and a clear input terminal for setting the count value to 0. ing. Therefore, when the origin detection limit switch LSO is turned on by the striker 1a of the arm 1 at a certain arm angle and the Z signal is emitted from the pulse encoder E1, a high level signal is input to the clear input terminal, If the position of the arm at that time is taken as the origin, then the output of the up-down counter 4, which integrates the up-direction or down-direction pulses sent from the first pulse encoder E1, indicates the absolute position of the arm 1. The relationship between the incremental pulse encoder E1 and the pulse counter 4 also applies to the pulse encoder E2 and the pulse counter 6 in exactly the same manner.

Now, as described above, the rotation angle of the arm 1 is measured by the pulse counter 4, and is taken in as position information to the control circuit 7 via the switching circuit 5.
Every time the arm 1 moves at regular intervals, its position information is stored in the memory m in the control circuit 7. Naturally, detectors similar to the position detector E1 are provided for all other degrees of freedom of the arm 1, and position information is stored in the memory m for each degree of freedom. In this way, teaching is completed in which all positional information necessary for teaching is stored in memory m.

When the teaching is completed and the reproducing operation is to be started, the mode changeover switch of the control circuit 7 is switched to the reproducing mode side. This switching causes the control circuit 7 to send a command signal RS to turn on the clutch 2.
"1" is output, and the clutch 2 is in the engaged state. Next, the control circuit 7 sends a transfer command signal TS.
is output, the transfer circuit 10 is energized, and the counter content of the first pulse counter 4, that is, the current position information of the arm 1, is transferred to the second pulse counter 6 via the transfer circuit 10, and is used as an initial value. The counter value of the second pulse counter 6 becomes exactly the same value as the count value of the first pulse counter 4. Next, the control circuit 7 receives a switching command signal CS
"1" is output, and the common terminal c of the switching circuit 5 is switched and connected to the switching terminal b. Due to this switching operation, the second pulse counter 6 is connected to the control circuit 7 via the switching circuit 5.

During reproduction, the position information of the arm 1 obtained by the teaching is sequentially read out from the memory m and outputted to the comparator 8 as the target position value θin. On the other hand, since the subsequent rotation of the motor M is detected by the second pulse encoder E2, the second pulse counter 6 to which the position signal of the first pulse counter is set as an initial value receives pulses corresponding to the increase or decrease. The output value θm is added to the comparator 8. The comparator 8 calculates the difference between the detected rotation angle θm of the motor and the target signal θin, and the motor M is rotated in a direction according to the difference, so that the rotational position of the arm 1 automatically matches the target angle θin. controlled to do so.

Note that in the transfer of the output value from the second pulse counter 6 to the first pulse counter 4 when switching from the reproduction mode to the teaching mode, the output of the first pulse counter 4 is not used even in the reproduction mode. However, since the counting operation continues, it is unnecessary.

Next, an example of the specific mounting positions of the two position detectors E1 and E2 used in the above embodiment device is shown in the eighth section.
This will be explained with reference to the figures.

As is clear from FIG. 8, the main body casing 15 to which the motor M is attached rotatably supports the shaft 18 by bearings 16 and 17, and the shaft 18 and the output shaft 19 of the motor M are connected to each other by the reducer 3. connected.
The shaft 18 has a coil C of the electromagnetic clutch 2 in its middle part.
The clutch plate 22, which integrally has a core 20 surrounding the core 20 and faces the core 20 with a slight gap 21 in between, is a rotating cylinder 24 rotatably supported on the shaft 18 via a bearing 23. spline 2
5 so as to be slidable in the axial direction. The rotating cylinder 24 has a large gear 26 on its outer periphery, and the large gear 26 meshes with a small gear 29 that is integrated with a shaft 28 that is rotatably attached to the main body casing 15 through a bearing 27. 28
A large gear 30 attached to the sensor meshes with a small gear 31 connected to the first detector E1, which is a pulse encoder. A second detector E2 is attached to the rear end of the output shaft 19 of the motor M. Further, the rotary wheel 24 has a mounting base 32 at its tip for mounting a robot element such as an arm. Therefore, when the motor M rotates, the rotation speed is detected by the second detector E2, and the rotation of the output shaft of the motor M is detected by the speed reducer 3.
is transmitted to the core 20 via the rotating cylinder 24 and the gear train 26, 29, 30, 31 when the clutch is in the ON state, that is, when the core 20 and the clutch disc 22 are in close contact due to the excitation of the coil C, to the first detector E1.
The rotation speed of the mounting base 32 of the clutch 3 is detected by the first detector E1. In this case, for example, the reduction ratio of reducer 2 is about 1/300,
If the speed increasing ratio of the gear train is 30 times, in order to make the pulses generated per rotation of the first detector E1 and the second detector E2 the same, the pulses generated per rotation of the first detector E1 are Multiply by 10 times. However, a frequency divider or the like may be used to match such pulses.

In addition, in the above-mentioned embodiment device, the first detector E1 and the second detector E2 have been explained using an incremental type as an example, but the first detector is as follows.
The present invention is not limited to this, and an absolute type position detector may be used. Examples of absolute type position detectors include resolvers and absolute pulse encoders. If the first detector is an absolute type, there is an advantage that the above-mentioned origin alignment operation is not necessary.

As described above, the control device for a direct teaching robot of the present invention includes a first detector provided on the output side of a transmission device including a clutch mechanism to detect the rotational position of a robot element, and a first detector provided on the input side of the transmission device. a second detector provided in the drive source for detecting the rotational position of the drive source;
a transfer means for selectively deriving the first detector output and the second detector output by switching between the first detector output and the second detector output; and a switching means for selectively deriving the first detector output and the second detector output; and stores the taught position of the robot element in response to the output thereof, and in the reproduction mode, energizes the transfer means to transfer the output of the first detector to the second detector. 2, the switching means is switched to the second detector output side, and the second detector output and the stored first detector output at the time of teaching are set to the initial value of the second detector. and a control means for feeding back a corresponding signal to the drive source, so that when the teaching mode is switched to the reproducing mode, the output of the second detector is made to match the output of the first detector and the output of the first detector is reproduced. Since a start can be made, when an incremental detector is used, accumulated errors due to repeated switching operations are eliminated, and more accurate and stable control can be performed. Additionally, there is generally a slight positional deviation between the input and output sides of a transmission device such as a speed reducer due to twisting of the transmission device, etc., and position detection during teaching is performed by a first position detector provided on the robot element side. An absolute type detector cannot be used in the so-called switching method in which position detection during playback is performed by a second position detector installed on the drive source side, but in the present invention, when switching to playback mode, always second
Since the output of the first detector is made to match the output of the first detector, there is no problem even if the above-mentioned positional deviation occurs, and therefore an absolute type detector can also be used in the above-mentioned switching system.

Note that the present invention is naturally applicable to robots using hydraulic cylinders, hydraulic motors, etc. as drive sources.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a conventional direct teaching robot control device, Fig. 2 is a block diagram showing a mathematical model of the same control device, and Figs. 3 and 4 show the step response of the same control device. 5 is a mathematically modeled block diagram of a control device that is an improved version of the same control device, FIG. 6 is a diagram showing the step response of the improved control device, and FIG. 7 is a diagram showing an embodiment of the present invention. Block diagram of the control device shown in FIG.
The figure is a side sectional view of the drive mechanism showing a specific example of the mounting positions of two detectors used in the control device. (Explanation of symbols), M...Motor (drive source), E
1, E2...first and second detectors, 1...arm (robot element), 2...clutch, 3...reducer, 4, 6...counter, 5...switching circuit, 7...
...Control circuit, 10...Transfer circuit.

Claims (1)

[Claims] 1 A transmission device including a clutch mechanism is interposed between a drive source and a robot element, and in a teaching mode, the clutch mechanism is turned off for teaching, and in a regeneration mode, the clutch mechanism is turned on and the transmission device is operated by the drive source. In a direct teaching type robot that drives the robot element through a first detector, the first detector is provided on the output side of the transmission device and detects the rotational position of the robot element, and the first detector is provided on the input side of the transmission device and detects the rotational position of the robot element. a second detector for detecting the rotational position of the source; transfer means for transferring the first detector output to the second detector; and a first detector output and a second detector output. a switching means for selectively deriving the information by switching the switching means; in the teaching mode, the switching means is switched to the first detector output side; upon receiving the output, the teaching position of the robot element is stored; and in the playback mode, the teaching position of the robot element is stored; energizing means to transfer the first detector output to the second detector as an initial value of the second detector;
The switching means is controlled to be switched to the second detector output side, and a signal corresponding to the second detector output and the stored first detector output at the time of teaching is returned to the drive source. A control device for a direct teaching robot, comprising a control means.