JPH0230487A - Control device for industrial robot - Google Patents

Abstract

PURPOSE:To prevent the breakdown of a robot arm and speed reducer by providing an estimator estimating the acceleration and loading torque of a robot arm and providing a comparator comparating each acceleration estimation value and load torque estimation value, generating a motor free control signal based on the result thereof and giving it to a breaker. CONSTITUTION:The acceleration of a robot arm 5 is estimated by an acceleration estimator 9 and also a load torque applied on the robot arm 5 is estimated by a load torque estimator 8. These estimation values are then compared by a comparator 10 and in case of an abnormality being generated on the robot arm 5 a motor free control signal is transmitted to a breaker 2 from the comparator 10 by detecting this abnormality immediately. The input voltage to a servo motor 3 is cut off by the breaker 2 based on this signal, the servo motor 3 is made in a free state and the breakdown of the robot arm 5 and a speed reducer 4 is prevented.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an industrial robot, and particularly to a control device for an industrial robot that is equipped with a robot SI protection function when an abnormal load is applied to the robot arm. It is.

[Traditional techniques]

FIG. 5 is a block diagram of a conventional industrial robot control device for controlling a robot arm. In Fig. 5, 1' is the servo motor 3 that controls speed and current.
Servo amplifier 2 controls servo motor 3 in case of abnormality.
4 is a speed reducer, 5 is a robot arm, 6 is a current detector, and 7 is a speed detector.

In this industrial robot control device, a current detector 6 detects the armature current flowing through the servo motor 3 and outputs one detected current value, and a speed detector 7 detects the rotation speed of the servo motor 3. and outputs the detected speed value ω.

Also, the servo amplifier 1' outputs the speed command value ωraf and the detected current value 1. Based on the detected speed value ω1, the servo motor 3
control the rotation speed and armature current.

Furthermore, this servo amplifier 1' has the following functions in addition to the above-mentioned control functions. That is, the current detection value 3 (corresponding to the armature current of the servo motor 3) output from the current detector 6 is constantly monitored, and the current set value (necessary to keep the robot arm 5 stationary) set in advance is monitored. breaker 2 only if the current exceeds the current value (slightly larger than the
The abnormality detection process is performed by sending a motor-free control signal to the motor. When the motor free control signal is applied to the circuit breaker 2, the circuit breaker 2 interrupts the current supply path from the servo amplifier 1 to the servo motor 3, and puts the servo motor 3 into a free state.

In the case of conventional industrial robot control devices, the robot becomes motor-free in this way.

When an abnormal load is applied to the robot arm 5 (for example, when the robot arm 5 collides with an obstacle, or when an abnormality occurs in the mechanical system and an excessive load is applied to the servo motor 3, etc.). As described above, one current detection value exceeds the current setting value, and the motor becomes free.

[Problem to be solved by the invention]

However, in the case of conventional abnormality detection processing methods,
An excessive load is applied to the robot arm 5 and the reduction gear 4 from the time the abnormality is detected until the servo motor 3 becomes free, and in some cases, they may be damaged. This is because the above-mentioned current setting value is determined from the current value required when accelerating and decelerating the robot arm 5, and is not a value that takes into account damage to the robot arm 5 or reducer 4. It is from. therefore,
When an abnormal load is applied to the robot arm 5, it is necessary to perform control to detect the abnormality before the robot arm 5 or reducer 4 is damaged, and immediately bring the servo motor 3 into a free state. .

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a control device for an industrial robot that can quickly bring a servo motor into a free state when an abnormality occurs in which an excessive 1-lux is applied to the robot/toam.

[Means to solve the problem]

The industrial robot control device of the present invention includes an acceleration estimator that estimates the acceleration of the robot arm from the speed command value given to the robot amplifier, a current detection value output from the current detector, and an output from the speed detector. A load torque estimator is provided that estimates the load torque applied to the robot/nodarm using the detected speed value and the detected speed value. A comparator is provided that constantly compares the motor free control signal with the motor free control signal and generates a motor free control signal based on the comparison result, and provides this motor free control signal to the circuit breaker.

[For production]

According to the configuration of the present invention, the acceleration of the robot arm is estimated by the acceleration estimator, and the load torque applied to the robot arm is estimated by the load torque estimator.
determined. The comparator constantly compares the estimated acceleration value and the estimated load torque value, thereby constantly monitoring the state of the load torque applied to the robot arm. As a result, when an abnormality occurs in the robot arm, the abnormality is immediately detected and a motor free control signal is sent from the comparator to the circuit breaker, which shuts off the circuit breaker and puts the servo motor into a free state.

〔Example〕

An embodiment of the present invention will be described based on FIGS. 1 to 4. In this embodiment, an example in which the present invention is applied to a digital servo amplifier in which speed control and current control are digitally controlled by a high-speed CPU will be described. In addition, in the calculations of the acceleration estimator and load torque estimator used in this invention, the Saho motor, robot, 7-torque arm, etc. are represented by a mathematical model, and calculations are performed based on that, so the servo amplifier is digital. An amplifier is suitable.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

In the same figure, ■ controls the speed and current of the servo motor 3.
2 is a circuit breaker that interrupts the input voltage to the servo motor 3 in the event of an abnormality, 4 is a speed reducer, 5 is a robot arm, 6 is a current detector consisting of a shunt I and a resistor. , 7 is a speed detector consisting of a rotary encoder. 8 is a load torque estimator for estimating the load torque Tt applied to the robot arm 5. 9 is a speed command value Q.
r.

Force 11 estimates the acceleration of the robot arm 5 from a speed estimator, 10 compares the load torque estimated value T outputted from the load torque estimator 8 with the acceleration estimated value T A CC outputted from the acceleration estimator. When the absolute value TERR of the difference between the load 1-lux estimated value TL and the force 11 speed estimated value TACC is larger than the predetermined value KERR, an abnormality occurs and the motor is Gives free control signal.

The basic operation of this industrial robot control device is the same as in the conventional example, in which the current detector 6 detects the armature current flowing through the servo motor 3 and outputs the detected current value Ia.
The speed detector 7 detects the rotational speed of the servo modulator 30 and outputs a detected speed value ω.

Further, the servo amplifier 1 controls the rotational speed of the servo motor 3 and the armature current based on the speed command value ωr□, the detected current value ■□, and the detected speed value ω.

Here, the configuration and operation of the load torque tIL determiner 8, acceleration estimator 9, and comparator]0 in the control device for this industrial robot will be described in detail.

First, the structure of the load l/lux estimator 8 will be explained.

This load torque estimator 8 is described in the literature of the Institute of Electrical Engineers of Japan; ``A control method for a passive DC machine using a state observer'' on page 49 of the Transactions of the Institute of Electrical Engineers of Japan (1984, Vol. 104-B, No. 6). It is well known as shown in . Since the load torque estimator 8 is one of the constituent elements of the present invention, the main points will be described here to explain that the present invention can be concretely realized. The load torque Tt applied to the robot arm 5 can be estimated using a state observation device by expressing it as a step-like function as in the equation 0 shown below. This is because it can be used as a state variable. If the zumbling time of this state view/Jlll device is made sufficiently short, it will follow the original function one after another in a stepwise manner.
A good estimate can be made.

(T1.)=0...■tHere, based on the above-mentioned literature, the state observation device for estimating the load 1/luk TL is expressed mathematically as the following 0 equation, and this mathematical expression The calculation can be realized with the configuration shown in the block diagram of FIG.

S → -a...■ The constants in ■2 above are the parameters of the servo motor 3, the parameters of the robot arm model, and the estimated time constant τ
It is uniquely determined by , and is expressed by the formula 0 to 0.

TL −・TL ・・・・・・■τS +
1 ・・・・・・■ KT ・・・・・・■ d−□ ・・・・
・■However, J is the total moment of inertia seen from the motor shaft,
KT is the torque constant of the servo motor 3, T8 is the current detection value that is the output of the current detector 6 that detects the armature current of the servo motor 3, and ω is the current detection value that is the output of the current detector 6 that detects the armature current of the servo motor 3. The speed detection value that is the output, D represents viscous resistance, and S represents the Laplace operator.

Further, in FIG. 2, 11 is an integral element, 12 to 14 are coefficient elements, 15 is an addition element, and 16 is a subtraction element.

Next, the configuration of the acceleration estimator 9 for determining the acceleration of the Roposo I arm 5 by H1 will be explained based on FIG. The speed command value ωcat is calculated from the standard model P□ (S) in which the servo motor 3 and the robot arm 5 are expressed mathematically, that is, the speed command value ω1 of the robot arm 5 obtained from the element 15 by applying manual input to the element 17 in FIG. , it is converted into acceleration by differential element 18 to obtain acceleration) II fixed T A (c. However, the standard model P of element 17, (S) is expressed as a model with a first-order lag element, such as the equation 0. .

PII (S)-・・・■ T, S+, K, and To are respectively expressed by 0 and 0 formulas, where K is the electromotive force constant and R is the armature resistance. .

ni, I-...■ K.

K7・K.

Next, the comparator 10 will be explained. Gono Hikiki lO
are the load l/lux estimated value T estimated by the load torque estimator 8 and the acceleration estimated value TAC estimated by the acceleration estimator 9.
The absolute value TIR is determined by taking the difference from C, and when this becomes larger than the experimentally determined predetermined value KERR, a motor free control signal is output to the circuit breaker 2. be. Expressed mathematically, the comparator 10 is 0
If the formula holds, it is assumed that an abnormality has occurred and circuit breaker 2
A motor free control signal is output to the motor.

TERR= l Tt. TACCl > KERR・
...■ Here, the overall flow of control can be summarized as shown in Figure 4. First, the current detection value I3 output from the current detector 6 and the speed detection value ω1 output from the speed detector 7
From the load torque estimator 8, the load torque estimated value T
Calculate L (21).

Next, the acceleration estimator 9 calculates the estimated acceleration TAC6 from the speed command value ωr□22), and the comparator 10 calculates the estimated load torque T t and the estimated acceleration T A
Calculate the absolute value T, □ of the difference from CC23), compare this absolute value TERR with the predetermined value Kl:lIR24),
As a result of the comparison, if TFRR>K□8, a motor free control signal is given to the circuit breaker 2.

Note that if T, □≦, or □, the process returns to the beginning.

The industrial robot control device of this embodiment includes a load torque estimator 8, an acceleration estimator 9, and a comparator 10, and the acceleration estimator 9 gives a speed command value ωr to the servo 7.
The acceleration of the robot arm 5 is estimated from the current detection value I output from the current detector 6 using the load torque estimator 8.
8 and the detected speed value ω outputted from the speed detector 7, the load I·Lux T1- applied to the robot arm 5 is estimated, and the comparator 10 calculates the estimated acceleration value TACC outputted from the acceleration estimator 9. (!: Constantly compares the load I and torque estimated values T t output from the load torque estimator 8, and generates a motor free control signal when the absolute value T□8 of the difference between them is larger than a predetermined value K ERR. Since the circuit breaker 2 is cut off by this motor-free control signal, the following effects are achieved.

■ Before an excessive load that would damage the robot arm 5 or reducer 4 is applied, abnormality detection processing can be performed immediately and the servo motor 3 can be put into a free state, and the robot arm 5 or reducer 4 can be Damage can be prevented.

■ Even if an abnormality occurs in the current detector 6 or speed detector 7, the effect will appear on the absolute value TERR, so the servo motor 3 can be immediately set to a free state, and in this case, the robot arm 5 and deceleration Damage to the machine 4 can be prevented.

〔Effect of the invention〕

According to the industrial robot control device of the present invention, a load torque estimator, an acceleration estimator, and a comparator are provided,
・The acceleration and load torque of the arm are estimated, and a motor-free control signal is generated and applied to the circuit breaker based on the comparison result of each acceleration estimate and load torque estimate, so the robot arm and reducer It is possible to detect an abnormality and set the servo motor to a free state before an excessive load that could cause damage is applied, thereby preventing damage to the robot arm or reducer.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIG. 2 is a block diagram showing the configuration of a load torque estimator for estimating the negative CjI · torque applied to the four-bottom arm, and FIG.
Figure 4 shows the configuration of an acceleration estimator that fixes the acceleration of the robot arm by 1 (1). 1. Zarpo amplifier, 2. Circuit breaker, 3. Zarpo motor, 4. Reducer, 5. Roposo I-arm, 6.
Current detector, 7...Speed detector, 8...Load L/L 11 (regulator, 9...Acceleration estimator,] Old...Comparator patent applicant Matsushita Electric Industrial Co., Ltd. Embedded) Patent attorney Akio Miyai〈H

Claims (1)

[Claims] A servo motor connected to the robot arm via a reducer, a servo amplifier that controls the speed and current of the servo motor, a speed detector that detects the speed of the servo motor, and a current that detects the servo motor. an acceleration estimator that estimates the acceleration of the robot arm from a speed command value input to the servo amplifier, a current detection value output from the current detector, and a speed output from the speed detector. a load torque estimator that estimates a load torque applied to the robot arm using the detected value;
a comparator that compares the estimated acceleration value output from the acceleration estimator and the estimated load torque value output from the load torque estimator and generates a motor-free control signal based on the comparison result; and the comparator A control device for an industrial robot, comprising: a circuit breaker that cuts off input voltage to the servo motor in response to a motor free control signal output from the servo motor.