System, machinery brake and method for controlling the machinery brake

Abstract

The system for controlling the opening and/or closing of a normally-closed machinery brake opening by means of at least one magnetizing coil and closing by means of at least one closing spring comprises: at least one estimation and control loop according to the invention and at least one measuring and control circuit according to the invention, which are connected or can be connected to each other, and of which a) the estimation and control loop is configured to use an input (I(t)) produced by the measuring and control circuit, and b) the measuring and control circuit is configured to use the modulation reference (U.sub.GE) produced by the estimation and control loop for connecting the voltage (U.sub.9) to be connected over the magnetizing coil.

Claims

1. A system for controlling an opening of a normally-closed machinery brake based on control of a magnetizing coil, the system comprising: at least one estimation and control loop configured to control the opening of the machinery brake, the at least one estimation and control loop including at least one calculation element, the at least one calculation element configured to record a target air gap value of an air gap defined by a spacing between a frame part and a bearer of the machinery brake, at least one air gap estimator, the at least one air gap estimator configured to determine an estimated air gap value of the air gap of the machinery brake based on an input received at the at least one air gap estimator, the input indicating a measured current of the magnetizing coil, the estimated air gap value determined based on determining an inductance of the magnetizing coil, the inductance determined based on a determined difference between a peak value and a minimum value of the measured current of the magnetizing coil, an air gap regulator, the air gap regulator configured to determine a target value of the current of the magnetizing coil based on the target air gap value of the machinery brake and the estimated air gap value of the machinery brake, and a current regulator, the current regulator configured to generate a modulation reference signal based on the target value of the current of the magnetizing coil and the input indicating the measured current of the magnetizing coil; and at least one measuring and control circuit, the at least one measuring and control circuit configured to control the opening of the machinery brake, the at least one measuring and control circuit including the magnetizing coil; an amplifier circuit, the amplifier circuit configured to produce a control voltage based on the modulation reference signal; a power output stage configured to connect a particular voltage over the magnetizing coil based on the control voltage, the power output stage configured to connect the particular voltage over the magnetizing coil at a particular frequency, the particular frequency greater than a frequency cut-off, the frequency cut-off based on a time constant of the magnetizing coil; an ammeter configured to generate an input indicating a measurement of a current of the magnetizing coil, the current of the magnetizing coil based on the particular voltage that is connected over the magnetizing coil; wherein the input generated by the measuring and control circuit is the input received at the at least one air gap estimator, wherein the system is configured to adjust the particular voltage that is connected over the magnetizing coil based on a change in the inductance of the magnetizing coil.

2. The system according to claim 1, wherein a time derivative or a temporal speed variation of the target air gap value of the air gap of the machinery brake decreases based on the target air gap value of the air gap of the machinery brake approaching a maximum value or a minimum value.

3. The system according to claim 1, wherein the target air gap values of the air gap of the machinery brake includes a plurality of experimentally determined target air gap values of the air gap of the machinery brake, and the air gap regulator is configured to ramp between the experimentally determined target air gap values of the air gap of the machinery brake.

4. The system according to claim 1, the amplifier circuit including an optoisolator.

5. The system according to claim 1, the amplifier circuit including at least one element of a digital isolator and an insulated-gate bipolar transistor (IGBT) driver.

6. A normally-closed machinery brake configured to be controlled by at least one magnetizing coil, wherein the machinery brake includes the system according to claim 1, and the power output stage of the system is configured to connect the particular voltage over the magnetizing coil based on the target air gap value of the air gap of the machinery brake in response to the input generated by the at least one measuring and control circuit.

7. The machinery brake according to claim 6, wherein the machinery brake is a machinery brake of an elevator, and the particular voltage that is connected with the control voltage is taken from an intermediate circuit of a frequency converter.

8. A method for controlling a normally-closed machinery brake based on a magnetizing coil, the method comprising: operating at least one estimation and control loop to control an opening of the machinery brake, the operating the at least one estimation and control loop including operating at least one calculation element to record a target air gap value of an air gap defined by a spacing between a frame part and a bearer of the machinery brake, operating at least one air gap estimator to determine an estimated air gap value of the air gap of the machinery brake based on an input received at the at least one air gap estimator, the input indicating a measured current of the magnetizing coil, the estimated air gap value determined based on determining an inductance of the magnetizing coil, the inductance determined based on a determined difference between a peak value and a minimum value of the measured current of the magnetizing coil, operating an air gap regulator to determine a target value of the current of the magnetizing coil based on the target air gap value of the machinery brake and the estimated air gap value of the machinery brake, and operating a current regulator to generate a modulation reference signal based on the target value of the current of the magnetizing coil and the input indicating the measured current of the magnetizing coil; and operating at least one measuring and control circuit to control the opening of the machinery brake, the operating the at least one measuring and control circuit including operating an amplifier circuit to produce a control voltage based on the modulation reference signal; operating a power output stage to connect a particular voltage at a particular frequency over the magnetizing coil based on the control voltage, the particular frequency greater than a frequency cut-off, the frequency cut-off based on a time constant of the magnetizing coil; and operating an ammeter to generate an input indicating a measurement of a current of the magnetizing coil, the current of the magnetizing coil based on the particular voltage that is connected over the magnetizing coil; wherein the input generated by the measuring and control circuit is the input received at the at least one air gap estimator, wherein the method further includes adjusting the particular voltage that is connected over the magnetizing coil based on a change in the inductance of the magnetizing coil.

9. The method of claim 8, wherein the power output stage is configured to connect the particular voltage over the magnetizing coil based on the target air gap value of the air gap of the machinery brake in response to the input generated based on the control voltage.

10. The method according to claim 8, wherein the target air gap values of the air gap of the machinery brake is optimized to dampen at least one noise of an opening noises of the machinery brake and a closing noises of the machinery brake.

Description

LIST OF DRAWINGS

(1) In the following the operational brake of an elevator and the elevator will be presented in more detail by the aid of the exemplary embodiments presented in the drawings FIGS. 1-8. Of the drawings:

(2) FIG. 1 is a simplified diagram of the main components of a machinery brake;

(3) FIG. 2 presents the shaft of an elevator motor, around which are three machinery brakes;

(4) FIG. 3 describes the speed profile desired from a machinery brake in a normal operating situation (BS);

(5) FIG. 4 describes the time profile of the target air gap for the air gap of a machinery brake;

(6) FIG. 5 describes the current flowing through the magnetizing coil of a machinery brake as a function of the magnitude of the air gap;

(7) FIG. 6 presents a system configured for controlling a normally-closed machinery brake opening by means of at least one magnetizing coil and closing by means of at least one closing spring, the system comprising an estimation and control loop connected to a measuring and control circuit;

(8) FIG. 7 describes the interdependency of the magnetization of the magnetizing coil and the magnetic field; and

(9) FIG. 8 illustrates the dependency of current ripple, i.e. peak value I.sub.max and minimum value 0, on the pulse-width voltage.

(10) The same reference numbers refer to the same technical parts in all the FIGs.

DETAILED DESCRIPTION

(11) FIG. 1 is a simplified diagram of the main components of a normally-closed machinery brake 1. The machinery brake 1 comprises a frame part 2, inside which is at least one magnetizing coil 9. The machinery brake 1 also comprises a bearer 4 that is movable with respect to the frame part 2, which bearer, depending on the model implemented, can be a disc 4. The movement of the bearer 4 moves the brake shoe 5. The to-and-fro movement of the bearer 4 occurs most preferably limited by a guide 8 (e.g. a guide bolt or guide rod).

(12) The machinery brake 1 is a normally-closed machinery brake. When the magnetizing coil 9 is not energized, the closing spring 3 (e.g. a cup spring and/or spring set) pushes the bearer 4 farther from the frame part 2. In this case an air gap 7 remains between the frame part 2 and the bearer 4, the magnitude d of which air gap 7 is negatively proportional with respect to the brake shoe 5 and the brake drum 6 on the surface of the rotating part 13 being braked. In other words, when d=0, the distance of the brake shoe 5 from the brake drum 6 is at its maximum (machinery brake fully open) and when d=d.sub.max, the brake shoe 5 is pressed tight against the brake drum 6 (the machinery brake 1 is in this case closed).

(13) The magnetizing coil 9 is presented in drawing FIG. 1, in the state in which it is not energized: The measuring and control circuit 30 has not in this case connected voltage U.sub.9 over the magnetizing coil 9. The weakening force brought about by the magnetic field produced in the frame part 2 of the magnetizing coil 9 and over the air gap 7 and also in the bearer 4 after the voltage U.sub.9 has been disconnected is in this case no longer able to resist the closing force produced by the closing spring 3, after which the machinery brake 1 has closed.

(14) FIG. 2 presents the shaft 13 of an elevator motor M, around which are three machinery brakes 1 that form the operational brake, or a part thereof, of the elevator. Instead of three separate machinery brakes 1, some other number (2, 3, 4, 5, 6, . . .) enabling redundancy can be selected. Marked in FIG. 2 is the magnitude d of the air gaps, i.e. each machinery brake 1 has its own air gap 7.

(15) Instead of separate machinery brakes 1, a machinery brake 1 provided with bearers/discs, each of which moving a brake shoe 5, that are provided with a redundancy-enabling number (2, 3, 4, 5, 6, . . .) of dedicated closing springs 3 is conceivable.

(16) The closing spring 3 of the machinery brake 1 keeps the operational brake 1 closed, i.e. it presses the brake shoe 5 and the disc 4 against the brake drum 6 when the magnetizing coil 9 of the electromagnet is not energized.

(17) When the magnetizing coil 9 of the electromagnet is energized, the attraction force of the electromagnet exceeds the thrusting force of the closing spring 3, in which case the brake shoe 5 and the disc 4 move closer to the frame part 2, in which case the machinery brake 1 opens.

(18) From the viewpoint of the operation of the electromagnet, it is essential that the frame part 2 is of a magnetically conductive (ferromagnetic) material and that the bearer 4 and possibly also the disc 4 is/are of a magnetically conductive material. An air gap 7 must remain between the frame part 2 and the bearer 4.

(19) FIG. 3 describes the speed profile desired from a machinery brake in a normal operating situation (BS). When starting the opening of the machinery brake 1 (from point d.sub.max when shifting to the left) the bearer 4, disc 4 and brake shoe 5 accelerate from the idle state to their maximum speed. When the machinery brake is fully open (to point 0 when shifting from the left) the machinery brake 1 should not make a sudden stop but instead should decelerate during the deceleration distance. Marked in FIG. 3 are the acceleration area C, moving area B and deceleration area A of the opening of the machinery brake 1. Correspondingly, when closing the machinery brake 1 A would be the acceleration area, B the moving area and C the deceleration area.

(20) FIG. 4 describes the time profile of the targeted air gap s*(t) for the machinery brake 1 in the case of the speed profile according to FIG. 3. When shifting from left to right in area A at the moment in time t.sub.1 the speed v.sub.1 increases by the moment t.sub.2 to the speed v.sub.2 and further by the moment t.sub.3 to the speed v.sub.3. When shifting from right to left the speed decreases correspondingly, i.e. v.sub.3->v.sub.2->v.sub.1.

(21) When shifting from left to right in area C at the moment in time t.sub.4 the speed v.sub.4 decreases by the moment t.sub.5 to the speed v.sub.5 and further by the moment t.sub.6 to the speed v.sub.6. When shifting from right to left the speed increases correspondingly, i.e. v.sub.6->v.sub.5->v.sub.4.

(22) Between the moments t.sub.A and t.sub.B, i.e. in the movement area B, the speed of change in the targeted air gap, i.e. the speed of movement of the bearer 4, disc 4 and brake shoe 5, remains roughly constant. Instead of constant speed, any other speed profile whatsoever can, of course, be defined for the movement area B.

(23) FIG. 5 describes the current I flowing through the magnetizing coil of a machinery brake as a function of the magnitude of the target air gap value s*(t). When the target air gap value s*(t) decreases (describing a smaller air gap 7), the machinery brake stays open with a smaller current I.

(24) FIG. 6 presents a system configured for controlling a normally-closed machinery brake 1 opening by means of at least one magnetizing coil 9 and closing by means of at least one closing spring 3, the system comprising a estimation and control loop 20 connected to a measuring and control circuit 30.

(25) The calculation element forms the target air gap value s*(t), i.e. the reference value for the air gap.

(26) The air gap regulator 24 compares the target air gap value s*(t) to the estimated air gap value s^(t), i.e. to the air gap estimate, calculated by the air gap estimator 26, and on the basis of the comparison calculates the target value I*(t) for the magnetizing coil current, i.e. calculates the reference value for the current I of the magnetizing coil 9 of the electromagnet.

(27) The reference value for current, i.e. the target value I*(t) for the current of the magnetizing coil, is supplied to the current regulator 25, which compares the target value I*(t) of the current of the magnetizing coil to the input, i.e. to the measured current I(t) of the magnetizing coil 9, and forms a modulation reference PW* for the pulse-width generator 21 (which can be a pulse width modulator).

(28) The pulse ratio of the pulse width modulation (PWM) of the pulse width generator 21 to the control signal, i.e. the modulation index, is calculated on the basis of the aforementioned modulation reference PW*.

(29) In other words, the modulation reference PW* (e.g. pulse-width reference) is determined on the basis of the target value I*(t) for the current of the magnetizing coil in the current regulator 25 and on the basis of the input I(t). On the basis of the modulation reference PW*, the pulse-width generator 21 makes pulse-width voltage U.sub.PW. The pulse-width voltage U.sub.PW is supplied to an amplifier circuit such as one or more optoisolators 27, which form(s) a modulation reference U.sub.GE on the basis of it.

(30) With the modulation reference U.sub.GE a controllable power output stage is controlled. The controllable power output stage can be realized e.g. as a bridge made by means of two or more IGBTs 31, 34 and possible rectifiers (e.g. diodes 32, 34). By means of the controllable power output stage, suitable voltage U.sub.9 is connected over the magnetizing coil 9. Instead of, or in addition to, the IGBTs 31, 34, e.g. MOSFETs can be used in the controllable power output stage.

(31) At the point of the magnetizing coil 9 the current l(t) is measured with an ammeter 12. The measurement result of the current I(t) is then supplied in the manner described above not only to the air gap estimator 26 but also to the current regulator 25.

(32) FIG. 7 describes the density B of the magnetic flux as a function of the magnetic field strength H. The magnetomotive force =N I (N=number of turns in the coil, I is the current flowing through the conductor of the magnetizing coil) traveling through the magnetizing coil 9 produces a magnetic field having a strength of H=/l.sub.m, where l.sub.m is the mean length of the field line.

(33) FIG. 8 illustrates the principle of the dependency of the peak value I.sub.max and minimum value 0 of the current ripple on the pulse-width voltage U.sub.PW.

(34) The inventors have observed that the magnitude of the air gap 7 of a machinery brake 1 affects the inductance of the magnetizing coil 9 and consequently the speed of change of the current. By ascertaining this dependency, e.g. with calibration runs, it is possible to utilize the information for formulating the description I(t)->s^ (t) of the air gap estimator 26.

(35) In other words, the control current of an electromagnetically controllable normally-closed machinery brake 1 can be adjusted for damping the noise of the machinery brake 1. Since the position feedback of the bearer 4, disc 4 and brake shoe 5 are realized by measuring the inductance and/or change in inductance of the electromagnet of the machinery brake 1 from the current I of the magnetizing coil 9 of the electromagnet of the machinery brake, it is possible by controlling the voltage U.sub.9 being connected over the magnetizing coil 9 to adjust the opening and/or closing of the machinery brake 1. The control voltage U.sub.9 of the magnetizing coil 9 is preferably greater than is known in the art compared to the inductance of the machinery brake 1, so that good dynamics is achieved for adjusting the current I of the machinery brake 1 by means of the voltage U.sub.9. This can be achieved e.g. by taking the voltage U.sub.9 to be connected with the control voltage U.sub.PW from the intermediate circuit of a frequency converter, the voltage of which is approx. 540-600 V or even higher.

(36) For example, a pulse width reference PW* with a frequency of 10 kHz and correspondingly a modulation reference U.sub.GE can be supplied to the control and adjustment circuit 30 in such a way that the force produced by the DC level of the current I exceeds the force of the closing spring 3 (i.e. the machinery brake 1 opens) and on the other hand the change in the switching frequency (e.g. 10 kHz) of the current is as linear as possible.

(37) In the test performed the current was measured from the peak and from the minimum of the saw-tooth current I, in which case with the average of the foregoing the DC level is obtained and with the difference the amplitude of ripple is obtained. The amplitude of the ripple depends mainly on the inductance of the load because when supplying e.g. 0 V and 560 V voltages the resistive effect of the load starts to limit the rate of rise of the current in a manner determined by the time constant L/R of the magnetizing coil 9 of the machinery brake only when the current has been able to make a step response that is significantly longer than the cycle time (e.g. 1/10 kHz) of the switching frequency.

(38) The inductance measured from the current ripple is then dependent on the inductance of the magnetizing coil 9 and on the air gap 7 of the magnetic circuit. In other words an estimate for the air gap 7 can be calculated from the inductance.

(39) If/when a good enough estimate is obtained for the air gap 7, the position of the disc 4 can be controlled with a simple cascade control in which the outer control loop is the air gap regulator 24 and the inner loop is the current regulator 25.

(40) The learning and/or calibration run of the disc 4 can be performed e.g. in such a way that the disc 4 is opened without feedback and it is seen from the air gap estimate what is the largest figure that the air gap 7 does not exceed. After this the maximum value for the air gap regulator 24 is set to the measured figure and the reference is always ramped only up to it. In other words, the reference is driven between closed/open, in which case the reference is made to be individual for each machinery brake 1.

(41) The invention must not be regarded as being limited only to the claims below but instead should be understood to include all legal equivalents of said claims and combinations of the embodiments presented.

LIST OF REFERENCE NUMBERS USED

(42) d magnitude of air gap M motor magnetic field 1 machinery brake 2 frame part 3 closing spring 4 bearer 4 disc 5 brake shoe 6 brake drum 7 air gap 8 guide 9 magnetizing coil 12 ammeter 13 braking rotating part 20 estimation and control loop 21 pulse width generator 23 calculation element 24 air gap adjuster 25 current regulator 26 air gap estimator 27 amplifier circuit (e.g. optoisolator) 30 measurement and control circuit 31 IGBT (power output stage part) 32 diode (power output stage part) 33 diode (power output stage part) 34 IGBT (power output stage part)