JP2011200030A - Controller of production apparatus and stop control method of motor for production apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a controller of a production apparatus, which can quickly stop a motor with a simple structure even if a fault occurs in a position detector.SOLUTION: The controller operates a dynamic brake (S5) at first if abnormality of the position detector is determined (S1:YES), and estimates a present electric angle θof a servo motor from values of the respective phase currents of the servo motor, which are detected during a braking period, concretely, from a ratio of respective phase currents Iu, Iv and Iw (S6 to S9). When the dynamic brake is canceled, counter torque braking is performed in accordance with the estimated electric angle θ(S12).

Description

  The present invention relates to a control device that controls a motor used in production equipment such as a robot, and a stop control method for a production equipment motor.

Robot systems are designed and produced with sufficient considerations to minimize the occurrence of failures. However, it may be unavoidable that some parts may fail as a result of aged deterioration or a load exceeding the design assumption. As one of such failures, for example, a position detector such as a rotary encoder or resolver arranged in the servo motor of each axis of the robot body fails, or between these position detectors and the robot controller. It is assumed that the communication line connecting is disconnected.
When such a failure occurs, it becomes impossible to accurately control the servo motor, and it is necessary to urgently stop the operation of the robot. Conventionally, in order to stop the operation of the robot urgently, dynamic braking (power generation braking, short-circuit braking) using the back electromotive force of the servo motor (see, for example, Patent Document 1), or the arm posture of the robot body originally resists the weight. It is common to actuate a mechanical brake that is used to hold it.

However, the dynamic brake does not always provide a sufficient braking force, and it takes a long time to completely stop the operation of the robot body. Further, in the mechanical brake, compared with a normal use state, a load is excessively applied, so that deterioration is accelerated, and there is a possibility that a braking force is insufficient at the time of original use. Although it is conceivable to provide a separate mechanical brake for emergency stop, it requires an extra space for the robot and is directly connected to cost increase, so it cannot be easily adopted.
For example, Patent Document 2 discloses a technology that appropriately performs cooperation with synchronous operation control so that the motor can be stopped at the target position even when the motor performing position sensorless control steps out. It is disclosed.

JP 2001-204184 A International Publication WO00 / 004632

  That is, if the electrical angle of the rotor cannot be obtained due to a failure or the like of the position detector, the electrical angle can be estimated by performing position sensorless control as in Patent Document 2. However, it is still a development that adopts a configuration that allows position sensorless control only to cope with an emergency in spite of the configuration that is supposed to control the motor using a position detector. Extra costs are required.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control device for production equipment capable of quickly stopping a motor with a simple configuration even when a failure occurs in a position detector, and production. An object of the present invention is to provide a device motor stop control method.

  According to the control device for a production device of the first aspect, the stop control means performs the stop control of the motor as follows when the abnormality determination means determines the abnormality of the position detector. First, dynamic braking is started, and the current electrical angle of the motor is estimated from the ratio of each phase current of the motor detected during the braking period. Then, reverse torque braking is performed according to the electrical angle estimated to cancel the power generation braking. In other words, even if it becomes impossible to obtain the electrical angle of the motor due to a failure or the like in the position detector, the current electrical angle can be calculated by referring to the motor phase current ratio detected during dynamic braking. Can be estimated. And it becomes possible to make reverse torque braking act on a motor based on the estimated electrical angle.

  In this stop control, reverse torque braking with a high braking force can be applied with simple control without separately providing an emergency stop brake mechanism or the like and without performing complicated calculation as in the position sensorless control. Therefore, it is possible to stop the operation of the production equipment by quickly stopping each axis motor when an abnormality occurs in the position detector without requiring extra space for the production equipment or increasing the development cost of the control device. Can do.

  According to the control apparatus for production equipment according to claim 2, the stop control means is a coefficient determined according to a sum of squares of each phase current of the motor detected during an operation period of the dynamic braking, a constant of the motor, and a rotation speed. When the rotational speed is estimated from the relationship, the number of rotations and the electrical angle after a predetermined period of time are predicted from the estimated electrical angle and rotational speed during the period of reverse torque braking. Here, the amount of rotation of the permanent magnet motor with respect to a certain point in time is referred to as “rotational position”, and the number of rotations and the electrical angle predicted after the predetermined time has elapsed are referred to as “next predicted rotational position”.

  When power generation braking is performed again after the predetermined time has elapsed, a plurality of predicted rotation position candidates are set according to the electrical angle estimated during the power generation braking period, and the next predicted rotation among the plurality of predicted rotation position candidates is set. The value closest to the position is determined as the predicted rotation position. That is, since the change of the rotational position cannot be accurately grasped during the period of reverse torque braking, the number of rotations and the electrical angle corresponding to the passage of time from the estimated electrical angle and rotational speed at the time of starting reverse torque braking; Predict the rotational position. In addition, the electrical angle estimated during the period in which power generation braking is performed again after the lapse of a predetermined time may include an error of one electrical angle period or more.

  Therefore, if a plurality of predicted position candidates are set according to the estimated electrical angle, and a value closest to the next predicted rotation position among the plurality of predicted position candidates is determined as the predicted rotation position, the rotation position is determined appropriately. it can. By determining the rotational position in this way, it is possible to predict the final stop position of the production equipment driven by the motor, so that, for example, the tip of the robot arm moves on a straight line while correcting the rotational positional relationship between the axes. It is possible to stop as if moving.

  According to the control device for production equipment according to claim 3, since the stop control means repeatedly executes power generation braking and reverse torque braking alternately until the motor stops, the reverse torque braking is repeatedly applied to stop the motor. Can be accelerated.

  According to the production device control device of the fourth aspect, the stop control means reverses based on the position detection signal obtained immediately before the abnormality determination means determines abnormality before starting the first dynamic braking. Torque braking is performed for a certain time. Then, the number of rotations and the electrical angle after a lapse of a certain time are predicted during the period of reverse torque braking (initial predicted rotational position), and when the first dynamic braking is started, the electrical angle estimated in the dynamic braking period is determined. A plurality of predicted rotational position candidates are set, and among those predicted rotational position candidates, a value closest to the initial predicted rotational position is determined as the predicted rotational position.

  In other words, the position detection signal obtained immediately before the time when the abnormality is determined can be regarded as a reasonable value having continuity with the control performed so far, so before starting dynamic braking By performing reverse torque braking, the motor can be stopped more quickly. Similarly to the third aspect, during the period of reverse torque braking, the rotational position after the elapse of a fixed time can be predicted, and the rotational position when the first dynamic braking is started can be determined appropriately.

  According to the control device for a production device according to claim 5, the stop control means has an error amount Er (n) between the electrical angle predicted during the reverse torque braking period and the electrical angle estimated during the power generation braking period. When the error amount Er (n) decreases, the predetermined time (reverse torque braking operation time) is lengthened, and when the error amount increases, the predetermined time is shortened. Here, n indicates a period with an error amount periodically obtained (... n-1, n, n + 1, ...). That is, the braking force of reverse torque braking is determined according to the phase difference of the energization current with respect to the electrical angle of the motor. Therefore, if the error amount Er (n) becomes large and the phase difference of the energization current cannot be appropriately applied, the braking force is increased. descend. Therefore, when the error amount Er (n) increases, the operation time of reverse torque braking is shortened to improve the estimation accuracy of the electrical angle. In this case, the number of times reverse torque braking is applied may increase, but it is possible to reliably apply the braking force and stop the motor in a short time.

According to the control device for a production device according to claim 6, the stop control means sets _TRB (n) as the predetermined time determined this time, _TRB (n-1) as the predetermined time determined last time, and a predetermined electrical angle. When the estimated accuracy of Pc is Pc, the predetermined time T _RB (n) is set to T _RB (n) = T _RB (n−1) × Pc / Er (n)
To decide. If determined in this manner, the reverse torque braking operation time T _RB (n) is determined according to the ratio between the electrical angle estimation accuracy Pc and the error amount Er (n), if Pc <Er (n). The time T _RB (n−1) is shorter than the previous time T _RB (n−1), and if Pc> Er (n), it is determined to be longer than the previous time T _RB (n−1). Therefore, the action time T _RB (n) can be appropriately determined according to the estimation accuracy required in the system.

  According to the control device for a production device according to claim 7, the stop control means prohibits the subsequent reverse torque braking when the ratio that the error amount Er exceeds the estimated accuracy Pc becomes a predetermined value or more within a predetermined monitoring time. Thus, only dynamic braking is performed. That is, when the electrical angle estimation accuracy is not improved due to the influence of disturbance or the like, the error amount Er does not fall below the estimation accuracy Pc. Therefore, when the ratio that the error amount Er exceeds the required estimation accuracy Pc within a monitoring time exceeds a predetermined value, only dynamic braking is performed thereafter. If comprised in this way, a motor can be stopped reliably also in the condition where reverse torque braking cannot be made to act appropriately.

The flowchart which is the 1st example and shows the contents of braking processing Diagram showing motor three-phase current waveform according to electrical angle Diagram showing the phase relationship of each phase current on the unit circle The figure which shows the relationship between the rotation speed of a motor and braking torque The figure which shows the state from which the rotational force which generate | occur | produces in a servomotor according to the phase difference of an electrical angle and a drive current, and the attraction / repulsion force which acts between a stator and a rotor change. Timing chart corresponding to the process of FIG. Diagram for explaining the determination of the rotational position R _P performed in the period B in FIG. 6 Block diagram showing servo motor drive system and control system Diagram showing the configuration of the robot system FIG. 1 equivalent view showing the second embodiment Partial equivalent diagram of FIG. 10 showing the third embodiment

(First embodiment)
The first embodiment will be described below with reference to FIGS. FIG. 9 shows the configuration of the robot system. This robot body (industrial equipment) 1 has a 6-axis arm on a base (rotating shaft) 2 in this case, and a tool such as a hand (not shown) is attached to the tip of the arm. A first arm 3 is rotatably connected to the base 2 via a first joint J1. A lower end portion of a second arm 4 extending upward via the second joint J2 is rotatably connected to the first arm 3, and a third portion is connected to a tip portion of the second arm 4. The third arm 5 is rotatably connected via the joint J3.

  A fourth arm 6 is rotatably connected to the tip of the third arm 5 via a fourth joint J4, and a fifth arm is connected to the tip of the fourth arm 6 via a fifth joint J5. 7 is rotatably connected, and the sixth arm 8 is rotatably connected to the fifth arm 7 via a sixth joint J6. In addition, in each joint J1-J6, each arm 3-8 is rotationally driven by the servomotor 9 (1-6) (refer FIG. 7).

  The control device (stop control means) 11 incorporates independent driver units (inverters 16 shown in FIG. 8) corresponding to the servo motors 9 (1 to 6) of the respective axes, and these driver units are control circuits. 13 (see FIG. 8). The main body of the robot 1 and the control device 11 are connected by a motor line 14 and an encoder line 15. The motor line 14 is a wiring that connects between each phase output terminal of the inverter (drive circuit, see FIG. 8) 16 and the stator winding of the servo motor 9.

  The encoder line 15 connects the position detectors 17 (1 to 6) (see FIG. 8) disposed in the servo motors 9 (1 to 6) and the control device 11 for each axis of the robot body 1. Wiring. The position detector 17 is composed of, for example, a rotary encoder or the like, detects the absolute position of the rotor of the servo motor 9 by, for example, an optical method, and transmits position data to the control device 11 by communication.

  FIG. 8 is a block diagram showing a drive system and a control system of the servo motor 9. The inverter 16 is configured by connecting six switching elements such as power transistors in a three-phase bridge. The power supply circuit 18 includes a rectifier circuit 19 configured by connecting six diodes in a three-phase bridge and a smoothing capacitor 20, and rectifies and smoothes a three-phase AC power supply 21 to supply a DC power supply to the inverter 16. .

Further, FIG. 8 shows each function realized by software by the control circuit 13 configured by a microcomputer, for example. The subtractor 22 is given a position command value and a rotational position (number of rotations + electrical angle = rotation amount) R _P detected by the position detector 17, and the difference (position deviation) between the two is output to the multiplier 23. The The multiplier 23 multiplies the difference by a position loop proportional gain Kpp, and outputs the multiplication result to the subtractor 24 as a speed command value. A speed obtained by differentiating the rotational position R _P with the differentiator 25 is given to the subtractor 24 as a subtraction value.

The subtraction result (speed deviation) in the subtractor 24 is given to the multiplier 26 and multiplied by the speed loop proportional gain Kvp, and then outputted to the adder 27, and also given to the integrator 28 for integration. The integration result obtained by the integrator 28 is supplied to the multiplier 29 and is output to the adder 27 when multiplied by the speed loop integration gain Kvi. The addition result in the adder 27 becomes a torque command value and is given to the input terminal of the torque limiter (limiter) 32. The torque limiter 32 limits the torque command value output from the adder 27 at the upper limit and the lower limit, and outputs it to the coordinate conversion units 33U and 33V. The coordinate conversion units 33U and 33V store waveform data for applying a sinusoidal current to the servo motor 9, and are given the mechanical angle θ _M (position detection signal) detected by the position detector 17.

The coordinate conversion unit 33 reads and outputs sinusoidal current waveform data according to the electrical angle θ _E obtained from the mechanical angle θ _M (position detection signal) detected by the position detector 17. The torque command value given through the torque limiter 32 is multiplied by the current waveform data to set an amplitude value. The waveform data output from the coordinate conversion units 33U and 33V is given a phase difference of 120 °.

  The waveform data output from the coordinate conversion units 33U and 33V is given to the subtracters 36U and 36V, respectively, and is detected by the current detectors 37U and 37V arranged at the U and V phase output terminals of the inverter 16, respectively. The difference between the phase current and the V phase current is taken. The current detectors 37U and 37V are configured by, for example, a current transformer (CT). The subtraction results output from the subtractors 36U and 36V are multiplied by the current loop proportional gain Kcp by the multipliers 38U and 38V and output to the PWM generator / predriver 39.

  That is, only the U and V phase PWM command values are given to the PWM generator / predriver 39, and the PWM generator / predriver 39 internally generates the W phase PWM command value based on the PWM command value. To do. The PWM generator / predriver 39 outputs a three-phase PWM signal to the control terminal (base or gate) of each switching element (for example, power transistor, power MOSFET, IGBT, etc.) constituting the inverter 16.

  Next, the operation of the present embodiment will be described with reference to FIGS. As shown in FIG. 9, the robot body 1 and the control device 11 are connected by the motor wire 14 and the encoder wire 15. However, the encoder wire 15 is dropped and the position detection signal is sent to the control device 11 side. The case where it stops outputting is assumed. When the position detector 17 has an abnormality detection function, the result of detecting an abnormality on the position detector 17 side is added to the position detection data as error information and transmitted to the control device 11 side. ing. In this embodiment, when such a state occurs, braking is performed so that the rotation of the servo motor 9 is stopped in a shorter time.

FIG. 1 is a flowchart showing the contents of the braking process by the control device 11. This process is shown for any one of the six axes, and the same process is performed for all six axes. The control device 11 refers to the output signal of the position detector 17 and determines whether or not an abnormality has occurred in the position detector 17 (step S1). Here, as described above, it is determined that the output signal is not input due to the encoder line 15 being dropped, or the error information included in the output signal is acquired as “abnormal”. If no abnormality is detected in the position detector 17 (NO), the rotational position and rotational speed R _V of the servo motor 9 are detected from the output signal of the position detector 17 (step S2), and the servo motor 9 is controlled based on them. (Step S3).

The position detector 17 is arranged to output also the rotation number R _N of the servomotor 9 relative to the given time. Thus, "rotational position" is obtained in step S2, obtained from mechanical angle theta _M at that time the number of rotations R _N, is a relative rotational position of the rotor from the previous acquisition point R _P (amount of rotation) .

If an abnormality of the position detector 17 is detected during the normal control of the servo motor 9 as described above (step S1: YES), the position detector 17 relates to the rotational position _RP and the rotational speed R _V. Information cannot be obtained. Therefore, the control device 11 performs reverse torque braking for a predetermined time preset in the servo motor 9 based on the rotational position R _P and the rotational speed R _V obtained in step S2 immediately before the abnormality detection (step S2). S4). In this case, the phase difference between the rotational current (in this case, the electrical angle θ _E ) and the energized current phase is such that the reverse torque acting on the current rotational direction of the servo motor 9 is maximized. Is granted. As shown in FIG. 5, for example, if the energizing current phase difference is −90 ° when the servo motor 9 is rotating clockwise, the reverse torque braking force in the counterclockwise direction acts maximum.

  When the reverse torque braking operation time elapses, a dynamic brake (power generation braking) is applied to the servo motor 9 in the subsequent step S5. The dynamic brake is performed by, for example, turning off all the upper arm side switching elements of the inverter 16 and turning on all the lower arm side switching elements, and forming a loop for passing a short-circuit current to each phase winding of the servo motor 9. If necessary, a series circuit of a switch and a regenerative resistance element may be provided between the DC buses of the inverter 16, and the current may be consumed by the regenerative resistance element by closing the switch.

Then, when the phase currents Iu, Iv, Iw of the servo motor 9 are obtained during the period in which the dynamic brake is applied (step S6), the rotational speed R _V is calculated from these currents and estimated (step S7). Therefore, it is desirable that the time during which the dynamic brake is applied in step S5 is a time sufficient for the respective phase currents Iu, Iv, Iw to stabilize from the time when the brake is started. The time is determined according to the winding impedance of the motor or the like, and is about several milliseconds, for example.

  Here, the relationship between the dynamic brake and the phase currents Iu, Iv, Iw will be described. Assuming that the inductance of the motor winding is L and the phase current is I, the back electromotive force generated in accordance with the change in the current passed through the winding is (−L × dI / dt), especially during dynamic braking. Since the phase current I is reduced by the inductance L in the region where the rotational speed of the motor is high, the braking torque becomes small. In the region where the rotational speed of the motor is low, the influence of the inductance L is small, but the electromotive force is also small, so that the braking torque is also small.

That is, the dynamic brake has a high braking force in a limited rotational speed region, but has a smaller braking force than the reverse torque braking in a low speed and high speed region. FIG. 4 shows an example of the relationship between the rotational speed [rpm] of the motor and the braking torque [N · m], and the braking torque acting near 900 rpm has a peak. Each phase current Iu, Iv, Iw obtained during the period in which the dynamic brake is applied is expressed by the following equation.
Iu = {Vu− (N × dφu / dt + L × dIu / dt)} / R (1.1)
Iv = {Vv− (N × dφv / dt + L × dIv / dt)} / R (1.2)
Iu = {Vw− (N × dφw / dt + L × dIw / dt)} / R (1.3)
Where Vu, Vv, and Vw are applied voltages to the respective phase windings (0 during dynamic braking), φu, φv, and φw are field magnetic fluxes linked to the respective phase windings, and N is a winding of the windings. Here, the number of times R is a resistance of the winding and an external resistance such as other wiring.

Each phase current Iu, Iv, Iw during dynamic braking can also be expressed by the following equation.
Iu = k × sin (θ _E + σθ _E ) (2.1)
Iv = k × sin (θ _E + σθ _E + 2π / 3) (2.2)
Iw = k × sin (θ _E + σθ _E + 4π / 3) (2.3)
Note that σθ _E is a current phase shift generated by the winding inductance L, but can be obtained in advance because it is a function of the rotational speed. FIG. 2 shows the relationship between the electrical angle θ _E and each phase current Iu, Iv, Iw (provided that σθ _E = 0), and FIG. 3 shows the phase relationship of each phase current on a unit circle. It is a thing.

From the equations (2.1) to (2.3), the relationship of equation (3) can be derived,
Iu ² + Iv ² + Iw ² = 1.5 × k ² (3)
The coefficient k can be obtained from the equation (3). Coefficient k is a value determined by the characteristics of the rotating speed and the motor and the inverter, advance coefficient k and the rotational speed by previously obtained relation between [rpm] (becomes linear in general) rpm; rotation speed R _V Accurate estimation. Therefore, in step S7, the rotation speed R _V is calculated based on the equation (3). For example, if R _V = α · k (α is a proportional coefficient), the rotational speed R _V is R _V = √ {(Iu ² + Iv ² + Iw ² ) /1.5} / α (4)
Is required. Where √ {} is the square root in parentheses.
In the subsequent step S8, (θ _E + σθ _E ) is obtained from the equations (2.1) to (2.3) using an inverse trigonometric function. That is, as shown in FIG. 2, the phase (θ _E + σθ _E ) that satisfies the ratio of the amplitudes of the three-phase currents can be uniquely determined. Further, in the subsequent step S9, the current phase shift θ _E is obtained from the function of the rotational speed R _V calculated in step S7, and finally the electrical angle θ _E is obtained.

As described above, the rotational speed R _V, when estimating the electrical angle theta _E, based on them to confirm and predict the rotational position R _P of the servo motor 9 when allowed to act reverse torque braking (step S10 If the servo motor 9 is not stopped at that time (step S11: NO), reverse torque braking is applied (step S12). Then, the process returns to step S5, and thereafter, the dynamic brake and the reverse torque braking are alternately applied until the servo motor 9 stops (step S11: YES).

The reverse torque braking performed in step S12 is performed while tracing a stop trajectory at the time of occurrence of an abnormality that can be determined in advance. That is, based on the rotational speed R _V and the electrical angle θ _E estimated in steps S7 to S9, reverse torque braking is applied while performing position feedback control and speed feedback control in the control system shown in FIG. . From the change history of the estimated rotational speed R _V , the degree of deceleration due to the result of braking is also known. The electrical angle θ _E after a short time has elapsed can be estimated from the rotational speed R _V and the degree of deceleration. For example, the electrical angle θ _E (t + Δt) at the time when the minute time Δt has elapsed from time t is equal to the electrical angle θ _E (t) estimated at time t.
θ _E (t + Δt) ≈θ _E (t) + R _V × Δt (5)
It can be approximated by the above equation (5). In this way, the phase current control is continued while using the estimated electrical angle θ _E corresponding to the passage of time.

FIG. 6 shows a timing chart corresponding to the processing of FIG. 1, where the horizontal axis represents time T and the vertical axis represents the rotational position R _P (= number of rotations R _N + mechanical angle θ _M ) of the servo motor 9. The change in the vertical axis, regardless of the increase / decrease of the rotational position R _P, the rotational position R _P indicates a state go changed toward the final stopping position to be predicted. When an abnormality of the position detector 17 is detected (S1: YES), the first reverse torque braking is performed (S4, period A). Since accurate position information cannot be obtained during this period, reverse torque braking is not always performed with an appropriate energization phase difference. Further, as a result of applying reverse torque braking, a deviation also occurs in the predicted rotational position R _P.

When the period A ends, it becomes the period B in which the dynamic brake is applied (S5 to S10). Here, the rotational speed R _V and the electrical angle θ _E are estimated from the acquired phase currents Iu, Iv, Iw. FIG. 7 illustrates the determination of the rotational position R _P performed in the period B. The “predicted position” shown in FIG. 7 is a rotational position R _P (predicted rotational position) that is predicted to have reached this determination time point from a change in the rotational speed R _V. The electrical angle θ _E estimated by the equation (5) is determined between 0 DEG and 360 DEG, but the actual rotational position R _P of the servo motor 9 depends on how many servo motors 9 rotate during the period A. It depends on it.

Accordingly, a plurality of “position candidates (predicted position candidates)” shown in FIG. 7 are rotation position candidates in units of mechanical angles corresponding to electrical angles of 0 to 360 degrees in consideration of the number of rotations described above. Then, the “position candidate” closest to the “predicted position” is determined as the rotational position R _P predicted at this time (determined as the predicted rotational position), thereby correcting the error. The reverse torque braking in the next step S12 (period A) starts control based on the rotational position R _P predicted in period B. Thereafter, the rotation of the servo motor 9 is stopped while alternately repeating the dynamic brake and the reverse torque braking. Here, the rotational position R _P predicted in the period B after execution of step S4 corresponds to the “first predicted rotational position”, and the rotational position R _P predicted in the period B after execution of step S12 is “the next predicted rotational position”. ".

In the above process, even if the position information from the position detector 17 is not obtained, the rotation is stopped while the rotation position R _P of the servo motor 9 is appropriately estimated. It can be predicted in advance. And if it is a 6-axis robot as shown in FIG. 9, the same control is performed about the servomotor 6 (1-6) of each axis, and the stop position of each servomotor 6 (1-6) is each estimated. it can. Therefore, by controlling them comprehensively, it is possible to control them in conjunction with each other so that the hand of the arm reaches the target stop position without stopping each axis apart.

Here, the estimation accuracy of the electrical angle θ _E is examined.
(1) Conditions for applying reverse torque braking When the error of the electrical angle θ _E exceeds ± 90 DEG, reverse torque braking does not work, and acceleration force may be applied. The error needs to be less than ± 90 DEG.
(2) Conditions under which reverse torque braking can provide a braking force greater than that of dynamic braking As shown in FIG. 4, reverse torque braking generally provides a braking force that is about three times the rated torque. On the other hand, the braking force obtained by the dynamic brake is at most about twice the rated torque, and becomes smaller in the high speed region. Therefore, if it is about 2/3 of the maximum braking force in reverse torque braking, a braking force larger than that of the dynamic brake can be obtained. In this case, the required phase accuracy is ± 42 DEG or less.
(3) Accuracy Necessary for Estimating Rotation Position R _P As for this, as shown in FIG. 7, it is sufficient if the predicted position is close enough to any position candidate, so it is ± 180 DEG or less. . Considering the above three conditions, as a result, the required estimation accuracy is ± 42 DEG or less.

As described above, according to the present embodiment, when the controller 11 determines that the position detector 17 is abnormal, first, the dynamic brake is applied, and each phase current of the servo motor 9 detected during the braking period is detected. Specifically, the current electrical angle θ _E of the servo motor 9 is estimated from the ratio of the phase currents Iu, Iv, and Iw. When the dynamic brake is released, reverse torque braking is performed according to the estimated electrical angle θ _E. In other words, even if the position detector 17 fails and the electrical angle θ _E cannot be obtained, the current electrical angle θ _E can be estimated from the current values of the phases detected during the operation of the dynamic brake. The reverse torque braking can be applied to the servo motor 9 according to the electrical angle θ _E.

  The position estimation stop control described above applies reverse torque braking with high braking force with simple control without providing a separate brake mechanism for emergency stop and without performing complicated calculations like position sensorless control. Can be. Accordingly, the servo motor 9 of each axis is quickly stopped when an abnormality occurs in the position detector 17 without requiring extra space for the robot system or increasing the development cost of the control device 11. The operation of 1 can be stopped.

Further, the control unit 11, the individual phase currents Iu, Iv, when estimating the rotational speed R _V from the relation between the coefficient k determined according to the constant and the rotational speed R _V of the sum of squares and the servo motor 9 of Iw, reverse torque During the period of braking, the rotational position after the elapse of a predetermined time is predicted from the estimated electrical angle θ _E and rotational speed R _V. Then, when dynamic braking is performed again after a predetermined time has elapsed, a plurality of predicted position candidates are set according to the electrical angle estimated during the dynamic brake action period, and the predicted rotational position among the plurality of predicted position candidates is set. The value closest to is determined as the predicted rotation position R _P. Therefore, it is possible to reasonably determine the rotational position R _P, it is possible to predict the final stopping position for the hand of the robot body 1 which is driven by a servo motor 9. For example, the hand can be stopped so as to move on a straight line while correcting the rotational positional relationship between the axes.

Further, since the control device 11 repeatedly executes dynamic braking and reverse torque braking alternately until the servo motor 9 stops, it is possible to make the servo motor 9 stop earlier by repeatedly applying reverse torque braking. Further, before starting the first dynamic brake, the control device 11 performs reverse torque braking for a predetermined time based on the electrical angle θ _E obtained immediately before determining the abnormality of the position detector 17, and the reverse torque Also for the braking period, the predicted rotational position R _P is determined in the same manner as described above.

That is, the electrical angle θ _E obtained from the position detector 17 immediately before the time point when the abnormality is determined can be regarded as a reasonable value having continuity with the control performed up to that time point. By performing reverse torque braking before starting braking, the servo motor 9 can be stopped more quickly. The period in which performs inverse torque braking is predicted, determining the rotational position R _P after the lapse of a certain time, it can reasonably determine the rotational position R _P in the case of starting the first dynamic brake. Further, during reverse torque braking, braking is applied while always obtaining the electrical angle θ _E of the servo motor 9 at the elapsed time from the estimated electrical angle θ _E and rotational speed R _V.

(Second embodiment)
FIG. 10 shows a second embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. Hereinafter, different parts will be described. The configuration of the second embodiment is the same as that of the first embodiment, and the control content performed by the control device 11 is slightly different. That is, if “NO” is determined in the step S11, the steps S13 to S16 are executed.

In step S13, an error Er between the electrical angle θ _EB calculated in step S8 and the electrical angle θ _EA estimated in step S4 or the period of time in which reverse torque braking was applied in step S16 executed previously (in place of step S12). (N) is calculated. That is,
Er (n) = θ _EB (B) −θ _EA (6)
And Then, based on the error, the time (predetermined time) during which reverse torque braking is applied in step S15 is calculated (step S14). The calculation of the action time T _RB here is performed as follows, for example. Assuming that the working time obtained this time is T _RB (n), the previous working time is T _RB (n−1), and the required estimation accuracy of the electrical angle θ _E examined in the first embodiment is Pc,
T _RB (n) = T _RB (n−1) × Pc / {Er (n) + β} (7)
To obtain the action time T _RB (n) (corresponding to the length of the period A). Β is a margin and is determined in advance according to the actual control / drive system. An initial value is also set for the previous action time T _RB (n−1). When the action time T _RB (n) is obtained, the time T _RB (n) is stored as the previous value time T _RB (n−1) for the next calculation (step S15).

In addition, here, n is used to indicate a period with an error amount Er and an action time T _RB that are periodically obtained (..., N−1, n, n + 1,...). That is, if (n) is a value obtained in the current control cycle (or calculation cycle), (n-1) represents a value obtained in the previous control cycle.

According to the equation (7), the reverse torque braking operation time T _RB (n) depends on the ratio between the estimated accuracy Pc and the error amount Er (n) plus the margin β, Pc <{Er (N) + β} is shorter than the previous time T _RB (n−1), and Pc> {Er (n) + β} is longer than the previous time T _RB (n−1). It is determined. Thereby, the estimation accuracy of the electrical angle θ _E is improved. In this case, the number of times reverse torque braking is applied increases, but the braking force can be reliably applied to stop the servo motor 9 in a short time. That is, the above action realizes a learning function for obtaining the optimum value of the action time T _RB (n).

As described above, according to the second embodiment, the control device 11 determines the error amount Er (n) between the electrical angle θ _EA predicted in the reverse torque braking period A and the electrical angle θ _EB estimated in the dynamic brake period B. When the error amount Er decreases, the action time T _RB (n) is lengthened, and when the error amount Er (n) increases, the action time T _RB (n) is shortened. Specifically, the action time T _RB (n) is determined by the equation (7). Therefore, the operating time T _RB (n) can be adjusted according to the increase / decrease of the error amount Er (n) based on the estimated accuracy Pc required in the system, and the braking force can be reliably applied to the servo motor 9. .

(Third embodiment)
FIG. 11 shows the third embodiment, and the differences from the second embodiment will be described. In the third embodiment, when the learning function of the action time T _RB (n) is realized as in the second embodiment, when it is estimated that the estimation accuracy of the electrical angle θ _E is not improved, Control to stop torque braking. FIG. 11 is a partial equivalent diagram of FIG. 10. If “NO” is determined in the step S11, it is determined whether or not an RB stop flag set in a step S27 described later is set (step S21). Since the RB stop flag is cleared in the initial state (for example, at the time of step S1: YES), the process proceeds to the next step S22 (NO).

In step S22, it is determined whether or not the error amount Er exceeds the estimated accuracy Pc. If Er> Pc is not satisfied (NO), the process proceeds to step S23. If Er> Pc is satisfied (YES), the process proceeds to step S24. . In step S23, the Er counter is decremented (however, when the counter value is zero, zero is maintained), and in step S24, the Er counter is incremented. After execution of step S23 or S24, the process proceeds to step S25.
In step S25, for example, it is determined whether or not the monitoring timer that has started the timing operation after execution of step S4 has counted up a time corresponding to a predetermined monitoring time, and if not counted up (NO), step S14. If the count is incremented (YES), the process proceeds to step S26. In step S26, it is determined whether or not the value of the Er counter is equal to or greater than a predetermined value.

That is, the determination in step S26 corresponds to determining whether or not the ratio that the error amount Er exceeds the estimated accuracy Pc is equal to or greater than a predetermined value within the monitoring time during the loop of steps S5 to S16. When the ratio of the error amount Er obtained in step S13 to be equal to or less than the estimated accuracy Pc is high, the Er counter value becomes zero or a value near zero, and sufficient braking force for reverse torque braking applied in step S16 is obtained. It is judged that it is possible. Therefore, if it is determined “NO”, the Er counter is cleared (step S28).

  On the other hand, for example, when the ratio of the error amount Er exceeding the estimated accuracy Pc is high due to the influence of disturbance or the like, the Er counter value shows a larger value, and a sufficient braking force for reverse torque braking can be obtained. It is estimated that it is in a state in which Therefore, if “YES” is determined in step S26, the RB stop flag is set (step S27), and the process proceeds to step S5. If the RB stop flag is set, “YES” is determined in the step S21, and the process proceeds to the step S5. Thus, the reverse torque braking is not applied thereafter, and only the dynamic brake is performed until the rotation of the servo motor 9 is stopped (step S11: YES).

  As described above, according to the third embodiment, the control device 11 prohibits subsequent reverse torque braking when the ratio at which the error amount Er exceeds the estimated accuracy Pc becomes equal to or greater than a predetermined value within a predetermined monitoring time. Do only dynamic braking. Therefore, the motor can be surely stopped even in a situation where reverse torque braking cannot be appropriately applied.

The present invention is not limited to the embodiments described above or shown in the drawings, and the following modifications or expansions are possible.
Step S4 may be deleted and the dynamic brake may be applied first.
Further, dynamic braking and reverse torque braking may be performed once each.
The acting force of reverse torque braking may be adjusted according to the estimated rotation speed of the servo motor 9. For example, the braking force may be maximized if the rotational speed is equal to or higher than the threshold value, but may be weakened according to the rotational speed if the rotational speed is less than the threshold value.
The required estimation accuracy of the electrical angle θ _E may be set to a value smaller than ± 42 DEG.
In the second and third embodiments, the margin β in the equation (7) may be set as necessary.

The adjustment of the action time T _RB (n) is not limited to that based on the equation (7). For example, the action time T _RB (n) is increased or decreased by adding or subtracting a constant value to the previous value T _RB (n) or multiplying by a constant ratio coefficient. May be.
As the position detector, one that outputs information on the absolute number of rotations or one that outputs only the two-phase pulses of the A and B phases without outputting the information on the number of rotations may be used. In the latter case, the relative number of rotations may be obtained by integrating the output pulses.
In addition, for example, a resolver or the like may be used as the position detector.
In the third embodiment, the time point at which the monitoring timer starts timing is not limited to after execution of step S4. For example, the timing may be started from the time when “NO” is first determined in step S11 or S21.
Industrial equipment is not limited to robots, but can be applied to other machine tools.

  In the drawings, 1 denotes a robot body (industrial equipment), 9 denotes a servo motor (permanent magnet type synchronous motor), 11 denotes a control device (stop control means), and 17 denotes a position detector (position detection means).

Claims (14)

In a control device that controls a motor used in production equipment,
Current detection means for detecting a current passed through the motor winding;
An abnormality determination means for determining an abnormality of the position detector from a position detection signal output from a position detector arranged in the motor or from an output state of the position detection signal;
When the abnormality determination means determines the abnormality, it comprises a stop control means for performing stop control of the motor,
The stop control means includes
When the dynamic braking is started, the current electrical angle of the motor is estimated from the ratio of each phase current of the motor detected during the braking period,
When the power generation braking is released, reverse torque braking for generating torque in a direction opposite to the rotation direction of the motor is performed according to the estimated electrical angle. The stop control means includes
When the dynamic braking is started, the rotational speed of the motor is estimated from the relationship between the sum of squares of each phase current and a coefficient determined according to the constant and rotational speed of the motor,
Predicting the number of rotations and electrical angle after a predetermined time has elapsed from the estimated electrical angle and the estimated rotational speed during the period of reverse torque braking (referred to as the next predicted rotational position),
When power generation braking is performed again after the predetermined time has elapsed, a plurality of predicted position candidates are set according to the electrical angle estimated during the power generation braking period, and among the plurality of predicted position candidates, Confirm the closest value as the predicted rotation position,
The production apparatus control device according to claim 1, wherein reverse torque braking is performed again when the power generation braking is released.   The production device control device according to claim 2, wherein the stop control unit repeatedly performs power generation braking and reverse torque braking alternately until the motor stops. The stop control means includes
Before starting the first dynamic braking, immediately before the abnormality determination means determines the abnormality, reverse torque braking is performed for a certain period of time based on the position detection signal obtained from the position detector,
During the period of reverse torque braking, the number of rotations and electrical angle after the lapse of the predetermined time are predicted (referred to as initial predicted rotation position),
When the first power generation braking is started, a plurality of predicted position candidates are set according to the electrical angle estimated during the power generation braking period, and a value closest to the initial predicted rotation position among the plurality of predicted position candidates 4. The production apparatus control device according to claim 2, wherein the estimated rotational position is determined.   The stop control means obtains an error amount Er (n) between the electrical angle predicted during the reverse torque braking period and the electrical angle estimated during the power generation braking period, and when the error amount Er (n) decreases, the predetermined amount is determined. 5. The control device for a production device according to claim 2, wherein the predetermined time is shortened when the time is lengthened and the error amount Er (n) increases. When the predetermined time determined this time is T _RB (n), the predetermined time determined last time is T _RB (n−1), and the estimation accuracy of the predetermined electrical angle is Pc, the stop control means determines the predetermined time T _RB ( n) T _RB (n) = T _RB (n−1) × Pc / Er (n)
6. The production apparatus control device according to claim 5, wherein   The stop control means prohibits subsequent reverse torque braking and performs only dynamic braking when the ratio at which the error amount Er exceeds the estimated accuracy Pc exceeds a predetermined value within a predetermined monitoring time. The control apparatus for production equipment according to claim 6. In a method for stopping and controlling a motor used in production equipment,
Detecting the current flowing through the motor winding,
When determining the abnormality of the position detector from the position detection signal output from the position detector arranged in the motor or from the output state of the position detection signal,
Starting the power generation braking of the motor, estimating the current electrical angle of the motor from the ratio of each phase current of the motor detected during the braking period;
When the power generation braking is released, reverse torque braking is performed in which torque is generated in a direction opposite to the rotation direction of the motor according to the estimated electrical angle. When the dynamic braking is started, the rotational speed of the motor is estimated from the relationship between the sum of squares of each phase current and a coefficient determined according to the constant and rotational speed of the motor,
Predicting the number of rotations and electrical angle after a predetermined time has elapsed from the estimated electrical angle and the estimated rotational speed during the period of reverse torque braking (referred to as the next predicted rotational position),
When power generation braking is performed again after the predetermined time has elapsed, a plurality of predicted position candidates are set according to the electrical angle estimated during the power generation braking period, and among the plurality of predicted position candidates, Confirm the closest value as the predicted rotation position,
9. The production machine motor stop control method according to claim 8, wherein reverse torque braking is performed again when the power generation braking is released.   10. The production machine motor stop control method according to claim 9, wherein power generation braking and reverse torque braking are alternately and repeatedly executed until the motor stops. Before starting the first dynamic braking, immediately before determining the abnormality, reverse torque braking is performed for a certain period of time based on the position detection signal obtained from the position detector,
During the period of reverse torque braking, the number of rotations and electrical angle after the lapse of the predetermined time are predicted (referred to as initial predicted rotation position),
When the first power generation braking is started, a plurality of predicted position candidates are set according to the electrical angle estimated during the power generation braking period, and a value closest to the initial predicted rotation position among the plurality of predicted position candidates 11. The method for stopping control of a motor for production equipment according to claim 9 or 10, characterized in that is determined as a predicted rotational position.   An error amount Er (n) between the electrical angle predicted during the reverse torque braking period and the electrical angle estimated during the power generation braking period is obtained. When the error amount Er (n) decreases, the predetermined time is lengthened, 12. The production machine motor stop control method according to claim 9, wherein when the error amount Er (n) increases, the predetermined time is shortened. Assuming that the predetermined time determined this time is T _RB (n), the predetermined time previously determined is T _RB (n−1), and the predetermined electrical angle estimation accuracy is Pc, the predetermined time T _RB (n) is set to T _RB ( n) = T _RB (n−1) × Pc / Er (n)
The stop control method for a motor for production equipment according to claim 12, wherein   14. The method according to claim 13, wherein if the ratio of the error amount Er exceeding the estimated accuracy Pc is equal to or greater than a predetermined value within a predetermined monitoring time, the reverse torque braking is prohibited and only the dynamic braking is performed. Stop control method for motors for production equipment.

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