JPH0318961Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to a speed control type servo control device, and in particular to a speed control type servo control device for a multi-jointed robot in which each arm is drive-controlled by a speed control method. Regarding.

[Conventional technology]

For example, as shown in Fig. 1, a robot has a plurality of arms 1a, 1b, 1c, etc., with the tip 2a of arm 1a attached to the axis 3b of arm 1b, and the tip 2b of arm 1b attached to the axis 3c of arm 1c. It is rotatably attached to form joints 4ab and 4bc. Servo motors (not shown) are attached to each of the axes 3a, 3b, and 3c, and commands are given to each servo motor from an arithmetic processing device such as a computer to control the robot to perform desired movements.

There are two control methods for controlling the movement of this robot: one is a control method in which the rotation angle of the servo motor installed on each axis, that is, the movement position of each link, is given as a command, and sequential positioning is performed according to this command; There is a speed control type control system in which a provided servo motor is driven according to a speed commanded by an arithmetic processing device such as a computer, that is, a joint angular velocity. The speed control type control system has become widely used because the robot can move at a higher speed and more smoothly than the sequential positioning type control system.

[Problem that the invention attempts to solve]

However, if the arithmetic processing unit stops its operation for some reason, in the case of a sequential positioning control type robot, even if the arithmetic processing unit instructs the next position to be positioned and stops, the robot Since the motor stops at that position, problems such as runaway do not occur. However, in the case of a robot with a speed control type control system, if the processing unit suddenly stops executing the next speed instruction after instructing a certain speed, the robot will not stop its motion immediately, but will A dangerous situation arises in which the robot faithfully executes its movement according to the speed command of the robot, but loses its control function and goes out of control to the limit point of movement.

If the processing unit is operating normally, the processing unit monitors the position of the robot, that is, the angle of each joint, and based on this, it sequentially commands acceleration or deceleration, so such runaways will not occur. However, unless there are zero accidents that cause the arithmetic processing unit to stop execution, safety cannot be guaranteed.

In contrast, in the past, a timer was installed to stop the operation if the controlled object did not reach the target value within a predetermined period of time, but the timer's time limit was determined by the movement from the current value to the target value. The timer is determined by time, and even if an accident occurs, the timer continues to operate for the set time, so overruns are likely to occur. In order to prevent this, if the movement time is set short and position control is performed frequently, operation and stopping will be repeated frequently, which will slow down the movement speed and make high-speed control difficult. Ta.

There are various causes for a processing unit to stop execution, but some special ones include, for example, during the development of a program to teach a robot a task, execution may be interrupted due to a mistake in the program, or a loop may occur. There are many cases where the speed command cannot be output because the speed command is not output. For specialized machines that perform only a specific task, this kind of problem rarely occurs because the program is developed only once, but robots are highly versatile, so they have to be programmed multiple times each time the task changes. The problem is important because rework may occur, and it is common for this to be done by the user rather than the robot manufacturer. Moreover, in recent years, robots have been put into practical use by adding sensory functions, especially important visual and tactile functions, in order to improve their working capabilities.
Since the system is extremely complex, it is expected that there will be many runaway accidents due to program errors, and safety measures against such accidents are becoming an important issue.

[Means for solving problems]

For this purpose, in the speed control type servo control device of the present invention, in the speed control type servo control device equipped with a servo motor that is driven according to speed instruction data sequentially commanded by the calculation processing device, A register that holds speed instruction data sent out in synchronization with the strobe pulse, gate means for gating the speed instruction data held in this register, and analog gate means for gating the speed instruction data transmitted from the gate means. digital/analog conversion means for converting into speed instruction data and outputting zero when digital speed instruction data is not transmitted, and a time limit means operated by the strobe pulse;
The speed instruction data held in the register is sent to the servo motor side via the gate means, and the time limit means operates in response to the strobe pulse and turns off the gate after a predetermined time when the strobe pulse is not transmitted. The feature is that the drive of the servo motor is stopped by doing this.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3.

FIG. 2 shows the configuration of an embodiment of the present invention, and FIG. 3 explains its operation.

In Fig. 2, 5 is an arithmetic processing unit, and 6 is a servo mechanism for the axes (3b, 3c in Fig. 1) of each joint (4ab, 4bc in Fig. 1) of the robot, and there are as many joints as there are degrees of freedom. However, one of them is shown in FIG. The servo mechanisms for the other axes also have the same configuration as the servo mechanism 6.

The servo mechanism 6 includes a resistor 7, a gate 8, a retrigger monostable multivibrator 9, and a digital/
It has an analog converter (hereinafter referred to as a D/A converter) 10, a subtracter 11, an amplifier 12, a servo motor 13, a speed detector 14 including a tachometer generator, and a position detector 15 including a rotary encoder. Of the servo mechanism 6, a servo motor 13 is connected to the shaft of each joint of the robot.

Next, the operation shown in FIG. 2 will be explained with reference to FIG. 3.

In order to move each arm of the robot to a predetermined position or perform work, the arithmetic processing unit 5 applies a strobe pulse _S1 of a constant period T to the servo mechanism 6 of each axis, and this strobe pulse S. ₁
Speed instruction data _S2 for commanding the angular velocity of the servo motor 13 is transmitted as a digital signal in synchronization with the servo motor 13.
The speed instruction data _S2 transmitted to the servomechanism 6 is latched into the register 7 at the timing of the strobe pulse _S1 . The register 7 holds this speed instruction data _S2 and transmits it to the D/A converter 10 if the gate 8 is open at that time. gate 8
The retrigger monostable multivibrator 9 is a characteristic feature of the present invention, but will be explained after explaining the operation after the D/A converter 10 to facilitate understanding.

Note that the period T of the strobe pulse _S1 is the period T
The shorter the time, the smoother and finer the robot's movement will be, but the processing unit 5 will be required to have a higher processing capacity, and the servo mechanism 6 will be required to have faster response characteristics. become. On the other hand, if the period T is long, the arithmetic processing unit 5 only needs to have a low-speed processing ability, and the response characteristics of the servo mechanism 6 can also be made slow, but the robot will not be able to operate smoothly and finely. Therefore, the period T of the strobe pulse _S1 is determined based on the operation required of the robot and the performance of the device.

The D/A converter 10 converts the digital speed instruction data S ₂ into analog speed instruction data S ₃ and supplies it to the subtracter 11 . The D/A converter 10 is configured such that when the input is zero, that is, when the speed instruction data _S2 is not applied, the output is zero.

On the other hand, the speed detector 14 detects the rotational speed of the servo motor 13 and supplies the angular velocity signal S ₄ to the subtracter 11 . The amplifier 12 receives _{the difference S 5 ( S 5}
= _S3 - _S4 ) to control the servo motor 13. Therefore, when the actual angular velocity signal S ₄ of the servo motor 13 is smaller than the speed instruction data S ₃ , the output of the amplifier 12 is increased to increase the speed of the servo motor 13 and controlled so that they match. vice versa
In the case of S ₃ <S ₄ , the output of the amplifier 12 is decreased and controlled so that the two match. In this way, the robot moves or performs tasks as instructed by the arithmetic processing unit 5.

The position detector 15 receives the position signal of the servo motor 13.
_S6 , that is, the rotation angle is detected and fed back to the arithmetic processing unit 5. The processing unit 5 calculates the position of each arm of the robot from the position signal _S6 of the servo motor 13, calculates the speed of the servo motor of each arm necessary to perform the desired movement or work,
It will be transmitted to the servo mechanism 6 together with the strobe pulse _S1 as new speed instruction data _S2 .

When a robot moves on a certain trajectory, for example, when moving in a straight line at a constant velocity between two points in three-dimensional space, the angular velocity of each joint of the robot is generally not constant, but changes from moment to moment. It is necessary to calculate the angular velocity that the servo motor should take one by one and issue a command to each servo mechanism.

However, if some abnormality occurs in the arithmetic processing unit 5 and the strobe pulse _S1 and speed instruction data _S2 are no longer transmitted to the servo mechanism 6 at time _t3 in FIG. The speed instruction data S ₂ ((t ₂ )) output in _{step 2} is held, and the speed instruction data S ₂ (t ₂ ) will continue to be sent to the servo motor 13. Therefore, the servo motor 13 of each axis will continue to move at the speed S ₂ (t ₂ ) forever, and if this continues, it will become uncontrollable and the robot will run out of control.

However, as shown in FIG. 2, a gate 8 and a retrigger monostable multivibrator 9 are provided to prevent such runaway.

That is, when the strobe pulse _S1 is applied, the retrigger monostable multivibrator 9 outputs a gate pulse with a constant width TW, as shown as _S7 in FIG. and this gate pulse
The pulse width TW of S ₇ is chosen to be longer than the period T of the strobe pulse S ₁ as shown. and retrigger monostable multivibrator 9
As is well known, the gate pulse S ₇ is triggered
(Logic “1”), the pulse width TW
If it is retriggered within a time period of , the gate pulse S ₇ continues for a period of TW starting from the time of this retriggering.
operate to occur. Therefore, when the arithmetic processing unit 5 operates normally and the strobe pulse _S1 is reliably generated every period T and is applied to the retrigger monostable multivibrator 9, the retrigger monostable multivibrator 9 is gated. pulse s ₇
(logic "1") is generated continuously to turn on the gate 8.

When the arithmetic processing unit 5 is operating normally, the strobe pulse _S1 is reliably generated every period T, the gate 8 is always on, and the speed instruction data _S2 of the register 7 is D. The signal is sent to the /A converter 10, and the speed of the aforementioned servo motor 13 is controlled.

Next, the arithmetic processing unit 5, which had been operating normally until time t2 in FIG. ₃ and was generating the strobe pulse _S1 and speed instruction data _S2 , became abnormal for some reason, and the processing unit 5 in FIG. Even at t ₃ , the strobe
If the pulse S ₁ is not transmitted, the retrigger monostable multivibrator 9 returns to a low level (logic "0") after a time TW starting at time t ₂ and turns off the gate 8 . As a result, the speed instruction data S ₂ (t ₂ ) held in the register 7 is not transmitted to the D/A converter 10. Therefore, as mentioned above,
Since the output _S3 of the D/A converter 10 is configured to be zero, the servo motor 13 is controlled so that its speed becomes zero and stops immediately, thereby preventing runaway. be able to.

[Effect of idea]

As explained above, according to the present invention, when an abnormality occurs in the arithmetic processing unit and the strobe pulse _S1 is no longer transmitted, the gate closes and the speed instruction data _S2
to prevent the transmission of This immediately stops the rotation of the servo motor, making it possible to perform high-speed control and prevent the robot from running out of control due to loss of control.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the configuration of a robot arm, FIG. 2 is a configuration of an embodiment of the present invention, and FIG. 3 is a timing chart illustrating its operation. In the figure, 1a, 1b, 1c are arms, 2
a and 2b are the tips of the arms, 3b and 3c are axes, 4ab and 4bc are joints, 5 is an arithmetic processing unit, 6 is a servo mechanism, 7 is a register,
8 is a gate, 9 is a retrigger monostable multivibrator, 10 is a D/A converter, 11 is a subtracter, 12
13 is an amplifier, 13 is a servo motor, 14 is a speed detector, and 15 is a position detector.

Claims (1)

[Scope of utility model registration request] In a speed control type servo control device equipped with a servo motor that is driven according to speed instruction data that is sequentially commanded by a processing unit, it holds the speed instruction data that is sent out from the processing unit in synchronization with strobe pulses. a register 7 for gating the speed instruction data held in the register 7, a gate means 8 for gating the speed instruction data held in the register 7, and a gate means 8 for converting the digital speed instruction data transmitted from the gate means 8 into analog speed instruction data and converting the digital speed instruction providing digital/analog conversion means 10 for outputting zero when no data is transmitted, and time limit means 9 activated by said strobe pulse;
The speed instruction data held in the register 7 is sent to the servo motor side via the gate means 8, and the time limit means 9 is activated in response to the strobe pulse, and is activated after a predetermined time when no strobe pulse is transmitted. A speed control type servo control device characterized in that driving of the servo motor is stopped by turning off the gate means 8.