CA1096073A - Elevator control apparatus - Google Patents
Elevator control apparatusInfo
- Publication number
- CA1096073A CA1096073A CA295,504A CA295504A CA1096073A CA 1096073 A CA1096073 A CA 1096073A CA 295504 A CA295504 A CA 295504A CA 1096073 A CA1096073 A CA 1096073A
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- car
- deceleration
- circuit
- output
- control apparatus
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Abstract
ELEVATOR CONTROL APPARATUS
ABSTRACT OF THE DISCLOSURE
An elevator car control apparatus is disclosed in which a three-phase AC tachometer generator is coupled to a motor for driving an elevator car, and the AC output of the tachometer generator is full-wave rectified for use as a speed feedback voltage. A waveform-shaping circuit generates one pulse for each cycle of the output of the AC tachometer generator. A counter counts such pulses after the car has passed a deceleration-initiating point, thereby producing the number of counts proportional to a car running distance after the passage of the deceleration-initiating point. From this number of counts, a decelera-tion command voltage decreasing progressively in accordance with car positions is obtained by a decoder and a digital-analog converter. During deceleration, the car-drive motor is subjected to feedback control in accordance with the difference between the speed feedback voltage and the deceleration command voltage, thus effecting deceleration control of the elevator car.
ABSTRACT OF THE DISCLOSURE
An elevator car control apparatus is disclosed in which a three-phase AC tachometer generator is coupled to a motor for driving an elevator car, and the AC output of the tachometer generator is full-wave rectified for use as a speed feedback voltage. A waveform-shaping circuit generates one pulse for each cycle of the output of the AC tachometer generator. A counter counts such pulses after the car has passed a deceleration-initiating point, thereby producing the number of counts proportional to a car running distance after the passage of the deceleration-initiating point. From this number of counts, a decelera-tion command voltage decreasing progressively in accordance with car positions is obtained by a decoder and a digital-analog converter. During deceleration, the car-drive motor is subjected to feedback control in accordance with the difference between the speed feedback voltage and the deceleration command voltage, thus effecting deceleration control of the elevator car.
Description
~6~73 1 This irvention rc1ates to ~m elevator cont-rol apparatus effecting speed feedback control.
~ enera]ly, the control o an eleva-tor car is e-ffected by controlling the speed of a car-drive motor in accordance with a speed cornrnand signal and a speed -~eed-back signal. In order to assure the riding comfort and accurate floor landing, the speed con~nand signal is required to be e~actly matched ~ith a car position, especially during car deceleration. Thus, car speed control with high accuracy requires accurate detection of car positions and speeds. Conventionally, four Methods are considered for detecting car positions and speeds.
~ first method uses a floor selector and a 3C
tachometer generator. As well known, the floor selector incl~ldes a movable section adapted to move in a reduced scale in proportion to actual car motion, whereby the car position is detected indirectly. The car specd is detec-ted by an output voltage of the DC tachometer generator coupled to the car drive motor. This method, due to this high 20 accuracy and reliability in position and speed detection, ~-is now used most widely. The disadvantages are, however, -a very complicated configuration, a high cost and the necessi-ty of maintenance and lnspection of the floor selector and the ~C tachometer generator as o-ften as about once every montll.
~ second method uses a pulse generator and DC tachometer generator. ~he pulse generator is opera-ted in synchronism with car travel and the output pulses thereof are courîte(l, thereby detectin~;-the car position.
'I~ne car speed is detected in the same rnanner ~ in the 31~9i6~7i3 l first me-thod. Tlle method ~lder consideration, urlike the first one, eliminates the need of a floor selector and therefore is somewhat more econornical but s-till high in cost and requires substantially the same maintenance and inspec-tion as the fi-rs-t method.
A third method uses only a DC tachometer generat~
for detection purpose without using the floor selector or pulse generator, which is disclosed for example in Japanese Patent Publication I~o. ~0219/73. The DC tachometer lO generator is coupled to a car drive motor, the output ;
voltage of which is continuously integrated. The value of the integration is proportional to the car running distance. The integrated result is thus used -to detect -the car position, while the car speed is detected by the output voltage of the DC tachomet;er generator similarly to the preceding method. ~Iowever, it is impossible to accura-tely integrate -the output of the DC tacilorne-te-r generator over a long period of time, which results in a low position-detecting accuracy, and hence the method under consideration is not suitable for a practical applicatlon.
According to a fourth method, a multiplicity of proximity switches are used to directly detect the car position, while the car speed is detected by a ~C tacho-meter generator. The proxill1ity switches are mounted on the hoistway wall. The car position is detected by the proximity switches actua-ted by an object to be detected, which is mounted on the car body. A great nwnber of proxirnity switches are required to a-ttain high accuracy of car position de-tection. To overcome this shortcoming, in an alteilnative now widely usecl, objects to be detec-ted .. ~ . . .
1 are mounted on the hoistway wall at the deceleration-initiating points for respective floors ? and a p~urality of proximity swltches locatecl on the car detect with high accuracy the car posltion only after the car has passed the deceleration-initiating point. Such an alternative method is disclosed for example in U.~. Paten-t No.
3,876,918. This method is low in cost and practically usable as compared with the first and second methods.
However, since the pro~imity switches are mounted on the car, it is necessary to provide on the car a proximity-- switch-mounting bar having the same length as a required car deceleration distance. The length of the switch-mounting bar is structurally limited general]y to about one meter. This method, therefore, is applicable only to an elevator system wi-th the car deceleration distance of one meter or less, which generally involves a car speed of 60 m/min or lot~er. ~or the elavator sys-tems involving a car speed higher than tha-t, the use o~ the first or second method is unavoidable. ~urther, even in the alternative method, a great number of proximity switches are required if the car position after passing ;--the deceleration-initiating point is to be detected accurately. This results in a very high cost and a lower reliability, and also makes maintenance and inspection difficult.
An object of the present invention is -to provide a highly economic elevator control apparatus having a simple construction in which the car speed is controlled in accordance with a car speed feedback signal and a speed command signal corresponding to the car posit,on.
31L~396~3 1 ~ccording to the present inven-tion, there is provided an elevator control apparatus including a motor for driving a car running in an elevator hoistwa~, a device for generating a speed comrnand signal in accordance 5 wi-th the position of said car, and a device for controlling ~`
said motor in response to said speed command signal and a feedback signal of the speed of said motor; the elevator control apparatus further comprising an ~C tachometer generator driven by saicl car drive motor, a rectifier circuit Yor rectifying the output of the AC tachometer generator to deliver the speed feedback signal, and a counter for detecting a car position by counting the number proportional to the output frequency of said AC tachome-ter genera-tor.
~he other objects and features of the present inventlon will explained with rei`erence to the accompany-ing drawing~s i.n~which:
Fig. 1 is a block diagram showing the general construction of an elevator control apparatus according to ; : -the present invention;
Fig. 2 shows a specific structure of a three-phase full-wave rectifier circuit;
Fig. 3 shows voltage-waveforms for explaining the operation of the circuits of Figs. 2 and ~; -Fig. ~ is a diagram showing a specific structure of a waveform-shaping c:i.rcuit and a counter circuit;
Fig. 5 is a diagram for explaining the method for setting deceleration positions;
Fig. 6 is 9, diagram showing the construction of a CilCUit ~or producing a reference speed col~nand voltage;
.
1 Fig. 7 shows volt;age waveforllls for explaining the operation of the circuits of Figs. 6 and 8;
Fig. 8 shows the constructioll of a circuit for smoothing the reference speed con~and signal and detecting a speed difference.
A control apparatus for a three-phase induction rnotor is proposed in U.S. Patent No. 3,805,133. This apparatus is suitable in the case ~here an elevator car is controlled continuously from powering operation to deceleration operation. Embodiments of the present invention will be explained below ~7ith reference to the case where the present invention is ap~plied to an elevator control apparatus using the motor control apparatus disclosed in the U.S. Patent ~o. 3,~05,133. In order to improve the riding com~ort and f:Loor-landing accuracy of the car, de-tection of car position after initiation of deceleration is important. In -the embocliments Imder-mentioned, therefore, an explana-tion will be made in detail especially of a de~-ice most suitable for detecting the car position after initiation of ~eceleration and a device for generating a car deceleration command in accordance with the detec-ted car position.
A block diagram for explaining the general construction of the control apparatus according to the present invention is sho~m in ~ig. 1, each section of which will be described in detail later.
An elevator car 1 and a counter-weight 2 are hung on a sheave 4 by means of a rope 3. The sheave 4 ls connected through a reduction gear 5 to an elevator car-drive three-phase induction inotor 6 and an elect~orn~gnetic 316~3 1 brake 7. l`he induction motor 6 is ln turn coupled -to a three-phase AC tachometer genera-tor 8. Reference characters R, S and T show a three-phase AC power supply, characters Ul and U2 contactors adapted to close durlng upward travel of the car, characters ~1 and D2 contactors adapted to close during downward travel thereof. During the powering control of the car? con-tactors P1, P2 and P3 are closed and the contactors Ul and U2 or Dl and D2 are closed in accordance with the direction of car travel.
As a result, the DC output terminals of a mixed bridge circuit comprising thyristors SCRl and SCR2 and rectifiers SRl and SR2 are shorted by the contactor P3, so that the thyristors SCRl and SCR2 connec-ted in reverse parallel are inserted between the S phase of the power suppl~ and the terminal OI one of the primary windings of the induction motor 6.
~ he remaining two terminals of -the prirnary windings of the induction motor, on the other hand, are directly connected to the power suppl~ terminals R and ~
respectlvely, thus making up a circuit configuration for powering operation.
At the same time, a device described later causes a well-known eleva-tor car s-tart signal to be applied to a reference speed comlnand generator circuit 18, the output of which in turn is applied to an acceleration comrnand smoothing circuit 19. An acceleration co~mand signal and a speed :Eeedback signcll, i.e., an output si~lal at a terminal 13-1, which is the result of rectifying the output of the ~C tacho~lleter generator 8 coupled to the induction motor 6, by a rectifier circuit 13, are applied .
- :
. .
~L0~6~3 1 to a comparator circuit 21 for powering control. Since the contact of a switching circuit 23 is closed on side b, the difference between the acceleration col~nand signal and the speed feedback signal detected by the comparator circuit 21 is applied to a phase shifter circuit 2~. The output of the phase shifter circuit 24 is ampli:Eied to a predetermined magnitude by a pulse amplifier circui-t 25.
This signal is applied as a gate signal to the thyristors SCRl and SCR2 for firing control. Thus, the generated torque of the induction motor 6 is regulated continuously from -the single-phase torclue to the maxim~n torque by ~ control of the primary single-phase voltage of the induc-tiOIl motor 6, thereby effecting powering control.
When the car in the accelerated condition r~ms at -the rated speed and reaches a decelera-tion-initiating point, a deceleration-ini-tiating point de-tector 10 inoluding a proximity switcll mounted on the car, detec-ts the deceleration-initia~tin~; poin,-t in cooperation with a detector unit 9 arranged on the hoistway. The result:ing deceleration-initiating poin-t detection signal o~ens the contactors Pl, P2 and P3, and closes contactors ~1 and ~2~ The DC output terminals of the mixed bridge comprising the thyristors SCRl, SCR2 and the rectifiers SRl, SR2 are released from the shorted condition, and the AC terminals of the bridge are connected to S and T phases of the power supply, ~hile the DC terminals thereof are connected to the two terminals of the primary windings of the lnduction motor 6. This process makes up a DC brake circuit which is a main circui-t for deceleration control. At the same 30 time, the contact of the swi,tching circuit 23 is closed ~ ~-~9~ 3 1 on side c. ~-nder 'GhiS condi-tion, the output at a gi~en terminal (such as a terl~Ai.nal 13-2 in the embodiment of ~ig. 1) of the rectifier circuit 13 for rectifying the output of the AC tachometer generator 8 into a direct current is shaped into a pulse form by a waveform shaping circuit 14. The signal thus shaped is applied to a co~mter circuit 15, a decoder circuit 16 and a latch circuit 17, thereby detecting the car position. In other words, the sigr.al from the deceleration-initiating position detector 10 is applied to a reset signal generator circuit 12 for the latch circuit 17 and the co~mter circuit 15, ,~
and the output signals a-t. the terminals 12-1 and 12-2 are used to set the co~nter circuit 15 and the latch circuit 17. Output pulses of the wa~eform-shaping circuit 14 ]5 proportional to the number of revolutions of the induction motor are counted by -the colmter circuit 15, the output of which is applied -to the decoder circuit 16 and stored in the latch circuit 17 to detect the car position ~,fter initiation of decele-ration. The resulting position signal is applied to the reference speed co~mand generator circuit 1~ thereby to produce a signal stepwisely decreasing in accordance with the position of the car under deceleration.
This stepped signal is formed into a smoothly decreasing decelera-tion command signal by a deceleration command smoothing circuit 20.
The deceleratlon com.~and signal thus produced and the speed feedback signal are applied to a comparator circuit 22 for deceleration control, thereby detecting the difference between the speed feedback sig,nal and the deceleration co~ and sign21. This differellce is applied , 1~96~373 1 to the gates of the -thyristors ~CRl and SCR2 through the phase shifter circuit 24 and the pulse amplifier circuit 25, so that the firing phase of the thyristors is control-led, and thus the DC brake force of the induction motor 6 is controlled, whereby the deceleration control o-E the car is effected.
When the car decelerates and reaches a prede-termined point before a target landing floor, a decelera-tion end point detector 11 detects a deceleration end position, and the output si~lal of the detector 11 is used to cut off the power supply to the reference speed cornmand signal generator circuit 18, thereby reducing the decelera-tion com~land signal to zero. When a well-known device detects that the car speed has been reduced to zero, the ~
15 contactors Ul and U2 (or Dl and D2) and Bl and B2 are -opened by its output signal with the result that the electromagnetic brake 7 is actuated, thus stopping and holding the car stationary.
Upon stoppage of the car, a reset signal is applied from the reset si~lal generator circuit ]2 to the counter circuit 15 and the latch circuit 17, so that the counter circuit 15 and the latch circuit 17 are reset and -~
rendered ready for the next operation.
A concrete circuit diagram of the recti:Eier - -circuit 17 for detecting the speed feedback signal pro-portional to the number of revolutions of the induction motor 6 and the frequency thereof is shown in ~ig. 2.
Voltage waveforms -Eor exp]aining the operation of the circuit ]~ are shown in ~ig. ~.
~0 The outputs El, E2 and E~ of the three-phase AC
_ 9 _ ~L~396~)7:~
1 tachometer generator 8 are, as shown in (a) of Fig. 3, three-phase AC voltage components having a phase differ-ence of l/3-T with each other, where T represents period of El, E2 and E3. The magnitude and phase of the voltages El, E2 and E3 are varied in proportion to -the number of revolutions of the induction motor 6.
~ y applying these voltages to the input terminals 13-2, 13-3 and 13-4 of the three-phase full-wave rectifier circuit 13 comprised of six rectifiers 13-5 to 13-10, a DC output voltage E4 having a waveform as shown in (b) of Fig. 3 is produced. The magnitude of this DC voltage E4 is proportional to the car speed and it is used as a speed feedback signal. In this case, the smaller the ripple included in the speed feedback signal E4, -the better the elevator ca-r control charac-teristics. For this reason, the AC tachometer generator 8 is preferably of three-phase type with many poles.
The pulses proportional -to the number of revo:lu-tions of the induction motor 6 are detected in the manner mentione~ below.
A voltage E5 between earth E and a given AC
terminal, say, the terminal 13-2 of the three-phase full- ;
wave rectifier circuit 13 in Fig. 2 is taken out. The voltage E5 is positive only when the potential at the terminal 13-2 is higher than that at terminal 13-3 or 13-4. In the case where the potential at terminal 13--2 is lower than that at terminal 13-3 or 13-4 9 on -the other hand, the voltage E5 becomes negative with respect to the forward voltage drop at the rectifier 13-10. AccordiMgly, as shown in (c) of Fig. 3, an asymmetric AC voltage w:ith - 10 .-~96~373 1 2/3-~ and l/3-T on positive and negative sides respec1;ivel~
is obtained. Since a signal proportional to the number o~
revolutions of the induction motor 6 is taken out of one arm of the rectifier circuit 13 in this way, the need of 5 an additional circuit is eliminated.
The voltage E5 is applied between earth E and the input terminal 14-1 of the waveform-shaping circuit 14 sho~n in Fig. 4, and further to the base of a transistor 14-5 through a filter circuit including resistors 14-2 and 14-3 and a capacitor 14-4, so that a collector voltage E6 of the transistor 14-5 is produced as sho~n~ in (d) of Fig. 3. The voltage E6 is shaped by a Schmitt-type inverter 14-6 made up of integrated circuits. As output voltage E7 of the inverter 14-6, as shown in (e) of Fig.
15 3, assumes a rectangular form having a duration of 2/~-T
and an interval of l/3-T. Reference numerals 14-8 and 14-7 show a power supply terminal and a resistor.
The repetition frequency f (= l/T) of the output pulses E7 is proportional to the number of revolutions of the induction motor 6. By applying these pulses to the counter circuit 15 of Fig~. 4 ? the number of pulses of E
are counted.
The relation among the diameter D(m) of the elevator sheave 4, the reduction ratio i of the reduction 25 gear 5, the number of revolutions N (rpm) of the induction motor 6 and the car speed _ (m/s) is expressed below.
v _ ~D ~ 60 (m/s) ...-.-----. (l) The relation between the pole number P of the three-phase AC tachometer generator 8 and the frequency f (~Iz) of the - 11 ~ ~;
96~73 1 output voltage thereof is given as ~ = 120 (rpm) ---------,---- (2) From equations (1) an-l (2), the car running distance Sp for 1 Hz of the output voltage frequency f of the AC
tachometer generator 8 is Sp = vf = 2iD (m) .................... (3) ~his necessarily determines the deceleration rate as restricted by the riding comfort of the car and the deceleration distance required for reducing the rated speed of the car to its stoppage, which in turn determines the number of output pulses ol the AC tachometer generator 8 to be counted by the co~1ter circui-t 15. Assuming that the average deceleration rate of the elevator car with the rated speed of 60 m/min is desi.rably 0.5 m/s2 from the viewpo,int of riding comfort, the deceleration distance is 1 m. Also assuming that the AC tachome-ter generator 8 has 48 poles, that the sheave diameter is 0.5 ; -m, and that the reduction ratio i of the reduc-tion gear 5 is 25.5, the car running distance for each pulse of the 20 output of the AC tachometer generator 8 is 2.55 mm. ~s -`
a result, 400 pulses are counted during the deceleration distance of 1 m. ~urther, the car position after passing -the deceleration-initiating point is accurately detec-ted by multiplying 2.55 mm by _, where _ is the count value of 25 the counter 15. ~
~he embodiment under consideration is applied ~;
to the elevator system under the above-mentioned condi-tions.
; . : ' ~ . , .:: ......... . . . .
; : ~ ' ' ~' ''' ' ' :, :
~6C~73 l The counter circuit 1.5 tnus comprises three ~-bit binary counters 15-1, 15-2 and 15-3 in series, there-by making up a counter effecting count of from zero to 255. (The outputs QB3~ QC3 and QD3 of the counter 15-3 5 are not used.) In order for making the counting operation of the counters 15-1, 15-2 and 15-3 to be started or prohibited simultaneously, the reset terminals Ro(ll), RO(l2)' RO(21)' RO(22)~ Ro(3l) and Ro(32) are connec-ted collectively to the reset terminal 15-4 of the counter circuit 15. The reset terminal 15-4 is impressed with a signal from -the reset signal generator circuit 12 shown in Fig. l. A "O" signal, i.e., a count-start signal is genera-ted at the deceleration-initiating point thereby to count the output pulses of the AC tachometer generator ~, 15 while the counting is prohibited by generating a "l"
signal during car stoppage. In this manner, the countin~g operation is prohibited except during car decelera-tion, thus preventing the effect of noises generated during car stoppage or po~ering operation.
The counting value of the counter circuit 15 iS
proportional to the car position after passing the deceleration-initiating point. As seen from the ~oregoing description, the accura-te car position is detected con-tinuously by multiplication of the car runnin~g distance 5 per one pulse by the counting value.
p ts QA1 to QA3 of the counter circuit 15 are applied to the decoder circuit 16 thereb~ to decode the car position required for producin~g a decelera-tion command. In this case, the input-output relation of 0 the decoder circuit 16 is required to be set on the basls . - 13 ~
~.:
~9~ 3 1 of the relation hetween car speed and deceleration distance shown in Fi~. 5.
In order to attain the preferablc riding com-fort of the car, the car deceleration should desirably be controlled in such a manner as to be smoothly increased and decreased in the vicinity of the deceleration-lnitiat-ing point and the deceleration-end point respectively, while maintaining the deceleration rate substantially constant between the deceleration initiating and end points. One method for setting deceleration positions to attain a preferable riding comfort is shown in Fig. 5 where vO shows the rated speed of the car, and SO the deceleration distance with the car landing pOillt. bein~
zero.
In ~ig. 5, thc speed differences VO - Vl and V6 ~ O are made small in the ~icinity of the dece]eration--initiating and decelerati.on-end poin-ts, while maintaining substantially constant the intermediate speed differences V] V2, V2 V3, V3 - V4~ V4 - V5 and V5 - V6.
Corresponding differences i71 distance are SO - Sl, Sl -S2~ S3 S~ S4 - Ss~ Ss - S6 and S6 - O.
The nwnber of pulses corresponding to each of the deceleration positions Sl to S5 thus obtained is calculated by -the equation (3) thereby to set the nu~lber of pulses to be applied to the decoder. ~he position SO
is detected by the output signal of the deceleration-initiatin~ poin-t detec-tor in ~ig. 1, and the posit:ion S6 by the output slgnal of the deceleration end posi-tion detector.
~ ;. 6 shows a circuit diaram for tal~ing out 1 the deceleratlon positions Sl to S5 determined ill accord-ance wi-th ~ig. 5, from the decoder c;.rcuit 16, storing the output of the decoder circuit 16 in the latch Gircu:Lt 17, applying the output of -the la-tch circuit 17 to the deceleration reference speed command generator circuit 18 including inverters with an open collector and dividing resistors, and thus produclng a reference speed command voltage.
In Fig. 6, the decoder ci.rcuit 16 is made up of five three-input NAND elements 16-1 to 16-5. Assuming that the number of pulses associated with the position S
in ~ig. 5 is 112, the outputs QA2, QB2 and Q~2 of the coun-ter circui-t 15 in ~ig. 4. are applied to the NAND
element 16-1, which produces an output for 112 pulses (= 16 ~ 32 ~ 64), thereby detecting the posi-tion Sl.
In like manner, the nurnber of pulses associ.ated with each of S2, S3, S~ and S5 is set. In order to a-tl.ain -the number of pulses thus set, the outputs of the counter circuit in Fig. 4 are combined appropriately and applied to the NA~D elements 1~-2 to 16-5 for posi-tion detection.
In the embodi.ment under consideration, the deceleration posi.tions Sl to S5 are taken out separate]y by the N4ND elements 16-1 to 16-5 from the count made by the counter circuit 15.
An alternative method is such that the decelera-tio~ position Sl is detected by the NAND element 16-1, while the deceleration position S2 is detected by the N~ND element 16-2 on the basis of generation of the si~nal from the N~N~ elernent 16-1 and -the subsequent co~m-ting of pulses corresponding to S2 ml.nus Sl. Subsequent , ~g6073 1 deceleration positlons S3 to S5 are also detacted Oll the basis of generation of sig~nals by the preceding N~ND
elements 16-2 to 16-4. In this method, however, if a NAND element in the preceding stage fails to produce a signal due to a fault or other causes, subsequent decelera-tion positions cannot be detected. In the case of car control requiring a high reliability, therefore, the method sho~n in the draw:ing is more desirable.
~he outputs of the decoder circuit 16 are applied to the latch circuits 17-1 to 17-5 respectively made up of two NA~ elements 17-11 and 17-21 to 17-51 and 17-52, in which the output of the decoder circuit 16 is `
stored upon application of a "1" signal to the reset terminal 17-6 of the latch circuit 17 from the reset signal generator circuit 12 in Fig. 1 at the deceleration-initiatillg poin-t. -;
~he p~rocess of generating the reference speed command voltage at an outpu-t terminal 18-]7 in Fig. 6 will be explained below with reference to ~ig. 7. A
contact 18-15 shown in Fig. 6 is so constructed as to be kept closed during the period from car start to the deceleration end position as shown in (a) of Fig. 7, in response to the car start signal and the output signal of the deceleration end point detector 11 of Fig. 1.
Until the car reaches the deceleration-initiating point, the deceleration-initiating point detector 10 in ~ig. 1 is no-t actuated, and -therefore the outputs of the reset signal generator circuit 12 for the latch circuit and the counter circuit are such that, as shown in (h) and (c) OI Fig. 7, the reset signal for -the co~Lnter circuit 37~3 1 15 is "1" ((c) of Fig. 7) and the reset signal of the latch circuit 17 is "0" ((b) of ~ig. 7), thus holding the counter circuit ancl the latch circuit in reset condi-tions.
5- As a result, all the outputs of the counter circuit 15 are "0", all the outputs of the decoder circuit 16 are "1", all the outputs of the latch circuit 17 are "0", and all the outputs of the inverters with open col- ~ `
lectors 18-1 to 18-6 are "1", thereby maintaining a high impedance.
When the contact 18-5 is closed by a car start signal, the series circuit including resistors 18-7 to 18-14 is connected to a DC power supply +E through the terminal 18-16. The voltage at -the output terminal 18-17 accordingly takes the form of a s-teppèd voltage with the maximum value thereof at the rise portion in (~j) of Fig.
7 :in accordance wi-th voltage division by the resistors 18-7 to 18-13 and the resistor 18-1~. This stepped voltage is the reference speed command for acceleration. The command voltages for both acceleration and deceleration are thus taken out from the same part, so that the command voltage at the end of acceleration may be easily rendered ;
to coincide with that at the time of the start of decele-ration. Consequently, the powering operation is smoothly
~ enera]ly, the control o an eleva-tor car is e-ffected by controlling the speed of a car-drive motor in accordance with a speed cornrnand signal and a speed -~eed-back signal. In order to assure the riding comfort and accurate floor landing, the speed con~nand signal is required to be e~actly matched ~ith a car position, especially during car deceleration. Thus, car speed control with high accuracy requires accurate detection of car positions and speeds. Conventionally, four Methods are considered for detecting car positions and speeds.
~ first method uses a floor selector and a 3C
tachometer generator. As well known, the floor selector incl~ldes a movable section adapted to move in a reduced scale in proportion to actual car motion, whereby the car position is detected indirectly. The car specd is detec-ted by an output voltage of the DC tachometer generator coupled to the car drive motor. This method, due to this high 20 accuracy and reliability in position and speed detection, ~-is now used most widely. The disadvantages are, however, -a very complicated configuration, a high cost and the necessi-ty of maintenance and lnspection of the floor selector and the ~C tachometer generator as o-ften as about once every montll.
~ second method uses a pulse generator and DC tachometer generator. ~he pulse generator is opera-ted in synchronism with car travel and the output pulses thereof are courîte(l, thereby detectin~;-the car position.
'I~ne car speed is detected in the same rnanner ~ in the 31~9i6~7i3 l first me-thod. Tlle method ~lder consideration, urlike the first one, eliminates the need of a floor selector and therefore is somewhat more econornical but s-till high in cost and requires substantially the same maintenance and inspec-tion as the fi-rs-t method.
A third method uses only a DC tachometer generat~
for detection purpose without using the floor selector or pulse generator, which is disclosed for example in Japanese Patent Publication I~o. ~0219/73. The DC tachometer lO generator is coupled to a car drive motor, the output ;
voltage of which is continuously integrated. The value of the integration is proportional to the car running distance. The integrated result is thus used -to detect -the car position, while the car speed is detected by the output voltage of the DC tachomet;er generator similarly to the preceding method. ~Iowever, it is impossible to accura-tely integrate -the output of the DC tacilorne-te-r generator over a long period of time, which results in a low position-detecting accuracy, and hence the method under consideration is not suitable for a practical applicatlon.
According to a fourth method, a multiplicity of proximity switches are used to directly detect the car position, while the car speed is detected by a ~C tacho-meter generator. The proxill1ity switches are mounted on the hoistway wall. The car position is detected by the proximity switches actua-ted by an object to be detected, which is mounted on the car body. A great nwnber of proxirnity switches are required to a-ttain high accuracy of car position de-tection. To overcome this shortcoming, in an alteilnative now widely usecl, objects to be detec-ted .. ~ . . .
1 are mounted on the hoistway wall at the deceleration-initiating points for respective floors ? and a p~urality of proximity swltches locatecl on the car detect with high accuracy the car posltion only after the car has passed the deceleration-initiating point. Such an alternative method is disclosed for example in U.~. Paten-t No.
3,876,918. This method is low in cost and practically usable as compared with the first and second methods.
However, since the pro~imity switches are mounted on the car, it is necessary to provide on the car a proximity-- switch-mounting bar having the same length as a required car deceleration distance. The length of the switch-mounting bar is structurally limited general]y to about one meter. This method, therefore, is applicable only to an elevator system wi-th the car deceleration distance of one meter or less, which generally involves a car speed of 60 m/min or lot~er. ~or the elavator sys-tems involving a car speed higher than tha-t, the use o~ the first or second method is unavoidable. ~urther, even in the alternative method, a great number of proximity switches are required if the car position after passing ;--the deceleration-initiating point is to be detected accurately. This results in a very high cost and a lower reliability, and also makes maintenance and inspection difficult.
An object of the present invention is -to provide a highly economic elevator control apparatus having a simple construction in which the car speed is controlled in accordance with a car speed feedback signal and a speed command signal corresponding to the car posit,on.
31L~396~3 1 ~ccording to the present inven-tion, there is provided an elevator control apparatus including a motor for driving a car running in an elevator hoistwa~, a device for generating a speed comrnand signal in accordance 5 wi-th the position of said car, and a device for controlling ~`
said motor in response to said speed command signal and a feedback signal of the speed of said motor; the elevator control apparatus further comprising an ~C tachometer generator driven by saicl car drive motor, a rectifier circuit Yor rectifying the output of the AC tachometer generator to deliver the speed feedback signal, and a counter for detecting a car position by counting the number proportional to the output frequency of said AC tachome-ter genera-tor.
~he other objects and features of the present inventlon will explained with rei`erence to the accompany-ing drawing~s i.n~which:
Fig. 1 is a block diagram showing the general construction of an elevator control apparatus according to ; : -the present invention;
Fig. 2 shows a specific structure of a three-phase full-wave rectifier circuit;
Fig. 3 shows voltage-waveforms for explaining the operation of the circuits of Figs. 2 and ~; -Fig. ~ is a diagram showing a specific structure of a waveform-shaping c:i.rcuit and a counter circuit;
Fig. 5 is a diagram for explaining the method for setting deceleration positions;
Fig. 6 is 9, diagram showing the construction of a CilCUit ~or producing a reference speed col~nand voltage;
.
1 Fig. 7 shows volt;age waveforllls for explaining the operation of the circuits of Figs. 6 and 8;
Fig. 8 shows the constructioll of a circuit for smoothing the reference speed con~and signal and detecting a speed difference.
A control apparatus for a three-phase induction rnotor is proposed in U.S. Patent No. 3,805,133. This apparatus is suitable in the case ~here an elevator car is controlled continuously from powering operation to deceleration operation. Embodiments of the present invention will be explained below ~7ith reference to the case where the present invention is ap~plied to an elevator control apparatus using the motor control apparatus disclosed in the U.S. Patent ~o. 3,~05,133. In order to improve the riding com~ort and f:Loor-landing accuracy of the car, de-tection of car position after initiation of deceleration is important. In -the embocliments Imder-mentioned, therefore, an explana-tion will be made in detail especially of a de~-ice most suitable for detecting the car position after initiation of ~eceleration and a device for generating a car deceleration command in accordance with the detec-ted car position.
A block diagram for explaining the general construction of the control apparatus according to the present invention is sho~m in ~ig. 1, each section of which will be described in detail later.
An elevator car 1 and a counter-weight 2 are hung on a sheave 4 by means of a rope 3. The sheave 4 ls connected through a reduction gear 5 to an elevator car-drive three-phase induction inotor 6 and an elect~orn~gnetic 316~3 1 brake 7. l`he induction motor 6 is ln turn coupled -to a three-phase AC tachometer genera-tor 8. Reference characters R, S and T show a three-phase AC power supply, characters Ul and U2 contactors adapted to close durlng upward travel of the car, characters ~1 and D2 contactors adapted to close during downward travel thereof. During the powering control of the car? con-tactors P1, P2 and P3 are closed and the contactors Ul and U2 or Dl and D2 are closed in accordance with the direction of car travel.
As a result, the DC output terminals of a mixed bridge circuit comprising thyristors SCRl and SCR2 and rectifiers SRl and SR2 are shorted by the contactor P3, so that the thyristors SCRl and SCR2 connec-ted in reverse parallel are inserted between the S phase of the power suppl~ and the terminal OI one of the primary windings of the induction motor 6.
~ he remaining two terminals of -the prirnary windings of the induction motor, on the other hand, are directly connected to the power suppl~ terminals R and ~
respectlvely, thus making up a circuit configuration for powering operation.
At the same time, a device described later causes a well-known eleva-tor car s-tart signal to be applied to a reference speed comlnand generator circuit 18, the output of which in turn is applied to an acceleration comrnand smoothing circuit 19. An acceleration co~mand signal and a speed :Eeedback signcll, i.e., an output si~lal at a terminal 13-1, which is the result of rectifying the output of the ~C tacho~lleter generator 8 coupled to the induction motor 6, by a rectifier circuit 13, are applied .
- :
. .
~L0~6~3 1 to a comparator circuit 21 for powering control. Since the contact of a switching circuit 23 is closed on side b, the difference between the acceleration col~nand signal and the speed feedback signal detected by the comparator circuit 21 is applied to a phase shifter circuit 2~. The output of the phase shifter circuit 24 is ampli:Eied to a predetermined magnitude by a pulse amplifier circui-t 25.
This signal is applied as a gate signal to the thyristors SCRl and SCR2 for firing control. Thus, the generated torque of the induction motor 6 is regulated continuously from -the single-phase torclue to the maxim~n torque by ~ control of the primary single-phase voltage of the induc-tiOIl motor 6, thereby effecting powering control.
When the car in the accelerated condition r~ms at -the rated speed and reaches a decelera-tion-initiating point, a deceleration-ini-tiating point de-tector 10 inoluding a proximity switcll mounted on the car, detec-ts the deceleration-initia~tin~; poin,-t in cooperation with a detector unit 9 arranged on the hoistway. The result:ing deceleration-initiating poin-t detection signal o~ens the contactors Pl, P2 and P3, and closes contactors ~1 and ~2~ The DC output terminals of the mixed bridge comprising the thyristors SCRl, SCR2 and the rectifiers SRl, SR2 are released from the shorted condition, and the AC terminals of the bridge are connected to S and T phases of the power supply, ~hile the DC terminals thereof are connected to the two terminals of the primary windings of the lnduction motor 6. This process makes up a DC brake circuit which is a main circui-t for deceleration control. At the same 30 time, the contact of the swi,tching circuit 23 is closed ~ ~-~9~ 3 1 on side c. ~-nder 'GhiS condi-tion, the output at a gi~en terminal (such as a terl~Ai.nal 13-2 in the embodiment of ~ig. 1) of the rectifier circuit 13 for rectifying the output of the AC tachometer generator 8 into a direct current is shaped into a pulse form by a waveform shaping circuit 14. The signal thus shaped is applied to a co~mter circuit 15, a decoder circuit 16 and a latch circuit 17, thereby detecting the car position. In other words, the sigr.al from the deceleration-initiating position detector 10 is applied to a reset signal generator circuit 12 for the latch circuit 17 and the co~mter circuit 15, ,~
and the output signals a-t. the terminals 12-1 and 12-2 are used to set the co~nter circuit 15 and the latch circuit 17. Output pulses of the wa~eform-shaping circuit 14 ]5 proportional to the number of revolutions of the induction motor are counted by -the colmter circuit 15, the output of which is applied -to the decoder circuit 16 and stored in the latch circuit 17 to detect the car position ~,fter initiation of decele-ration. The resulting position signal is applied to the reference speed co~mand generator circuit 1~ thereby to produce a signal stepwisely decreasing in accordance with the position of the car under deceleration.
This stepped signal is formed into a smoothly decreasing decelera-tion command signal by a deceleration command smoothing circuit 20.
The deceleratlon com.~and signal thus produced and the speed feedback signal are applied to a comparator circuit 22 for deceleration control, thereby detecting the difference between the speed feedback sig,nal and the deceleration co~ and sign21. This differellce is applied , 1~96~373 1 to the gates of the -thyristors ~CRl and SCR2 through the phase shifter circuit 24 and the pulse amplifier circuit 25, so that the firing phase of the thyristors is control-led, and thus the DC brake force of the induction motor 6 is controlled, whereby the deceleration control o-E the car is effected.
When the car decelerates and reaches a prede-termined point before a target landing floor, a decelera-tion end point detector 11 detects a deceleration end position, and the output si~lal of the detector 11 is used to cut off the power supply to the reference speed cornmand signal generator circuit 18, thereby reducing the decelera-tion com~land signal to zero. When a well-known device detects that the car speed has been reduced to zero, the ~
15 contactors Ul and U2 (or Dl and D2) and Bl and B2 are -opened by its output signal with the result that the electromagnetic brake 7 is actuated, thus stopping and holding the car stationary.
Upon stoppage of the car, a reset signal is applied from the reset si~lal generator circuit ]2 to the counter circuit 15 and the latch circuit 17, so that the counter circuit 15 and the latch circuit 17 are reset and -~
rendered ready for the next operation.
A concrete circuit diagram of the recti:Eier - -circuit 17 for detecting the speed feedback signal pro-portional to the number of revolutions of the induction motor 6 and the frequency thereof is shown in ~ig. 2.
Voltage waveforms -Eor exp]aining the operation of the circuit ]~ are shown in ~ig. ~.
~0 The outputs El, E2 and E~ of the three-phase AC
_ 9 _ ~L~396~)7:~
1 tachometer generator 8 are, as shown in (a) of Fig. 3, three-phase AC voltage components having a phase differ-ence of l/3-T with each other, where T represents period of El, E2 and E3. The magnitude and phase of the voltages El, E2 and E3 are varied in proportion to -the number of revolutions of the induction motor 6.
~ y applying these voltages to the input terminals 13-2, 13-3 and 13-4 of the three-phase full-wave rectifier circuit 13 comprised of six rectifiers 13-5 to 13-10, a DC output voltage E4 having a waveform as shown in (b) of Fig. 3 is produced. The magnitude of this DC voltage E4 is proportional to the car speed and it is used as a speed feedback signal. In this case, the smaller the ripple included in the speed feedback signal E4, -the better the elevator ca-r control charac-teristics. For this reason, the AC tachometer generator 8 is preferably of three-phase type with many poles.
The pulses proportional -to the number of revo:lu-tions of the induction motor 6 are detected in the manner mentione~ below.
A voltage E5 between earth E and a given AC
terminal, say, the terminal 13-2 of the three-phase full- ;
wave rectifier circuit 13 in Fig. 2 is taken out. The voltage E5 is positive only when the potential at the terminal 13-2 is higher than that at terminal 13-3 or 13-4. In the case where the potential at terminal 13--2 is lower than that at terminal 13-3 or 13-4 9 on -the other hand, the voltage E5 becomes negative with respect to the forward voltage drop at the rectifier 13-10. AccordiMgly, as shown in (c) of Fig. 3, an asymmetric AC voltage w:ith - 10 .-~96~373 1 2/3-~ and l/3-T on positive and negative sides respec1;ivel~
is obtained. Since a signal proportional to the number o~
revolutions of the induction motor 6 is taken out of one arm of the rectifier circuit 13 in this way, the need of 5 an additional circuit is eliminated.
The voltage E5 is applied between earth E and the input terminal 14-1 of the waveform-shaping circuit 14 sho~n in Fig. 4, and further to the base of a transistor 14-5 through a filter circuit including resistors 14-2 and 14-3 and a capacitor 14-4, so that a collector voltage E6 of the transistor 14-5 is produced as sho~n~ in (d) of Fig. 3. The voltage E6 is shaped by a Schmitt-type inverter 14-6 made up of integrated circuits. As output voltage E7 of the inverter 14-6, as shown in (e) of Fig.
15 3, assumes a rectangular form having a duration of 2/~-T
and an interval of l/3-T. Reference numerals 14-8 and 14-7 show a power supply terminal and a resistor.
The repetition frequency f (= l/T) of the output pulses E7 is proportional to the number of revolutions of the induction motor 6. By applying these pulses to the counter circuit 15 of Fig~. 4 ? the number of pulses of E
are counted.
The relation among the diameter D(m) of the elevator sheave 4, the reduction ratio i of the reduction 25 gear 5, the number of revolutions N (rpm) of the induction motor 6 and the car speed _ (m/s) is expressed below.
v _ ~D ~ 60 (m/s) ...-.-----. (l) The relation between the pole number P of the three-phase AC tachometer generator 8 and the frequency f (~Iz) of the - 11 ~ ~;
96~73 1 output voltage thereof is given as ~ = 120 (rpm) ---------,---- (2) From equations (1) an-l (2), the car running distance Sp for 1 Hz of the output voltage frequency f of the AC
tachometer generator 8 is Sp = vf = 2iD (m) .................... (3) ~his necessarily determines the deceleration rate as restricted by the riding comfort of the car and the deceleration distance required for reducing the rated speed of the car to its stoppage, which in turn determines the number of output pulses ol the AC tachometer generator 8 to be counted by the co~1ter circui-t 15. Assuming that the average deceleration rate of the elevator car with the rated speed of 60 m/min is desi.rably 0.5 m/s2 from the viewpo,int of riding comfort, the deceleration distance is 1 m. Also assuming that the AC tachome-ter generator 8 has 48 poles, that the sheave diameter is 0.5 ; -m, and that the reduction ratio i of the reduc-tion gear 5 is 25.5, the car running distance for each pulse of the 20 output of the AC tachometer generator 8 is 2.55 mm. ~s -`
a result, 400 pulses are counted during the deceleration distance of 1 m. ~urther, the car position after passing -the deceleration-initiating point is accurately detec-ted by multiplying 2.55 mm by _, where _ is the count value of 25 the counter 15. ~
~he embodiment under consideration is applied ~;
to the elevator system under the above-mentioned condi-tions.
; . : ' ~ . , .:: ......... . . . .
; : ~ ' ' ~' ''' ' ' :, :
~6C~73 l The counter circuit 1.5 tnus comprises three ~-bit binary counters 15-1, 15-2 and 15-3 in series, there-by making up a counter effecting count of from zero to 255. (The outputs QB3~ QC3 and QD3 of the counter 15-3 5 are not used.) In order for making the counting operation of the counters 15-1, 15-2 and 15-3 to be started or prohibited simultaneously, the reset terminals Ro(ll), RO(l2)' RO(21)' RO(22)~ Ro(3l) and Ro(32) are connec-ted collectively to the reset terminal 15-4 of the counter circuit 15. The reset terminal 15-4 is impressed with a signal from -the reset signal generator circuit 12 shown in Fig. l. A "O" signal, i.e., a count-start signal is genera-ted at the deceleration-initiating point thereby to count the output pulses of the AC tachometer generator ~, 15 while the counting is prohibited by generating a "l"
signal during car stoppage. In this manner, the countin~g operation is prohibited except during car decelera-tion, thus preventing the effect of noises generated during car stoppage or po~ering operation.
The counting value of the counter circuit 15 iS
proportional to the car position after passing the deceleration-initiating point. As seen from the ~oregoing description, the accura-te car position is detected con-tinuously by multiplication of the car runnin~g distance 5 per one pulse by the counting value.
p ts QA1 to QA3 of the counter circuit 15 are applied to the decoder circuit 16 thereb~ to decode the car position required for producin~g a decelera-tion command. In this case, the input-output relation of 0 the decoder circuit 16 is required to be set on the basls . - 13 ~
~.:
~9~ 3 1 of the relation hetween car speed and deceleration distance shown in Fi~. 5.
In order to attain the preferablc riding com-fort of the car, the car deceleration should desirably be controlled in such a manner as to be smoothly increased and decreased in the vicinity of the deceleration-lnitiat-ing point and the deceleration-end point respectively, while maintaining the deceleration rate substantially constant between the deceleration initiating and end points. One method for setting deceleration positions to attain a preferable riding comfort is shown in Fig. 5 where vO shows the rated speed of the car, and SO the deceleration distance with the car landing pOillt. bein~
zero.
In ~ig. 5, thc speed differences VO - Vl and V6 ~ O are made small in the ~icinity of the dece]eration--initiating and decelerati.on-end poin-ts, while maintaining substantially constant the intermediate speed differences V] V2, V2 V3, V3 - V4~ V4 - V5 and V5 - V6.
Corresponding differences i71 distance are SO - Sl, Sl -S2~ S3 S~ S4 - Ss~ Ss - S6 and S6 - O.
The nwnber of pulses corresponding to each of the deceleration positions Sl to S5 thus obtained is calculated by -the equation (3) thereby to set the nu~lber of pulses to be applied to the decoder. ~he position SO
is detected by the output signal of the deceleration-initiatin~ poin-t detec-tor in ~ig. 1, and the posit:ion S6 by the output slgnal of the deceleration end posi-tion detector.
~ ;. 6 shows a circuit diaram for tal~ing out 1 the deceleratlon positions Sl to S5 determined ill accord-ance wi-th ~ig. 5, from the decoder c;.rcuit 16, storing the output of the decoder circuit 16 in the latch Gircu:Lt 17, applying the output of -the la-tch circuit 17 to the deceleration reference speed command generator circuit 18 including inverters with an open collector and dividing resistors, and thus produclng a reference speed command voltage.
In Fig. 6, the decoder ci.rcuit 16 is made up of five three-input NAND elements 16-1 to 16-5. Assuming that the number of pulses associated with the position S
in ~ig. 5 is 112, the outputs QA2, QB2 and Q~2 of the coun-ter circui-t 15 in ~ig. 4. are applied to the NAND
element 16-1, which produces an output for 112 pulses (= 16 ~ 32 ~ 64), thereby detecting the posi-tion Sl.
In like manner, the nurnber of pulses associ.ated with each of S2, S3, S~ and S5 is set. In order to a-tl.ain -the number of pulses thus set, the outputs of the counter circuit in Fig. 4 are combined appropriately and applied to the NA~D elements 1~-2 to 16-5 for posi-tion detection.
In the embodi.ment under consideration, the deceleration posi.tions Sl to S5 are taken out separate]y by the N4ND elements 16-1 to 16-5 from the count made by the counter circuit 15.
An alternative method is such that the decelera-tio~ position Sl is detected by the NAND element 16-1, while the deceleration position S2 is detected by the N~ND element 16-2 on the basis of generation of the si~nal from the N~N~ elernent 16-1 and -the subsequent co~m-ting of pulses corresponding to S2 ml.nus Sl. Subsequent , ~g6073 1 deceleration positlons S3 to S5 are also detacted Oll the basis of generation of sig~nals by the preceding N~ND
elements 16-2 to 16-4. In this method, however, if a NAND element in the preceding stage fails to produce a signal due to a fault or other causes, subsequent decelera-tion positions cannot be detected. In the case of car control requiring a high reliability, therefore, the method sho~n in the draw:ing is more desirable.
~he outputs of the decoder circuit 16 are applied to the latch circuits 17-1 to 17-5 respectively made up of two NA~ elements 17-11 and 17-21 to 17-51 and 17-52, in which the output of the decoder circuit 16 is `
stored upon application of a "1" signal to the reset terminal 17-6 of the latch circuit 17 from the reset signal generator circuit 12 in Fig. 1 at the deceleration-initiatillg poin-t. -;
~he p~rocess of generating the reference speed command voltage at an outpu-t terminal 18-]7 in Fig. 6 will be explained below with reference to ~ig. 7. A
contact 18-15 shown in Fig. 6 is so constructed as to be kept closed during the period from car start to the deceleration end position as shown in (a) of Fig. 7, in response to the car start signal and the output signal of the deceleration end point detector 11 of Fig. 1.
Until the car reaches the deceleration-initiating point, the deceleration-initiating point detector 10 in ~ig. 1 is no-t actuated, and -therefore the outputs of the reset signal generator circuit 12 for the latch circuit and the counter circuit are such that, as shown in (h) and (c) OI Fig. 7, the reset signal for -the co~Lnter circuit 37~3 1 15 is "1" ((c) of Fig. 7) and the reset signal of the latch circuit 17 is "0" ((b) of ~ig. 7), thus holding the counter circuit ancl the latch circuit in reset condi-tions.
5- As a result, all the outputs of the counter circuit 15 are "0", all the outputs of the decoder circuit 16 are "1", all the outputs of the latch circuit 17 are "0", and all the outputs of the inverters with open col- ~ `
lectors 18-1 to 18-6 are "1", thereby maintaining a high impedance.
When the contact 18-5 is closed by a car start signal, the series circuit including resistors 18-7 to 18-14 is connected to a DC power supply +E through the terminal 18-16. The voltage at -the output terminal 18-17 accordingly takes the form of a s-teppèd voltage with the maximum value thereof at the rise portion in (~j) of Fig.
7 :in accordance wi-th voltage division by the resistors 18-7 to 18-13 and the resistor 18-1~. This stepped voltage is the reference speed command for acceleration. The command voltages for both acceleration and deceleration are thus taken out from the same part, so that the command voltage at the end of acceleration may be easily rendered ;
to coincide with that at the time of the start of decele-ration. Consequently, the powering operation is smoothly
2~ switched to deceleration operation.
When the car reaches the deceleration-initiating point, the deceleration-initiating position detector is ~-act~ated. The reset signa1 generator circuit 12 in Fig.
1 operates in such a manner that, as shown in (b) and (c) of Fig. 7, the reset signal :Eor the counter circuit 15 ., . I . . . . -~ .
. . .
1 changes from "1" to "0", and the reset signal for the lateh circuit 17 from "0" to "1", thereby setting both -the counter circuit 15 and the latch circui-t 17.
At -the same time, the output of the inverter 18-1 with the open collector changes from "1" to "0" as shown in (d) of Fig. 7 and the resistor 18-7 is grounded, so that the voltage at the output terminal 18-17 drops as shown in (j) of Fig. 7.
The counter circuit 15 begins to count. When the pulses applied to the NA~ element 16-1 reach a prede-termined number, the output the NAND element changes from "1" -to "0". Upon application of this output to the latch 17-1, the output of the latch 17-1 changes from "0" to "1" and is held at that value. In response to the output of the latch 17-1, the output of the inverter 18-2 with the open collector ehanges from "1" to "0" as shown in (e) of Fig. 7. The result is that the resistor 18~~ is grounded, thereby further reducing the voltage at the terminal 18-17.
Subsequen-tly, the outputs o~ the ~ elements 16-2 to 16-5 are cha~ged from "1" -to "0", those of latches 17-2 to 17-5 from "0" to "1", and those of the inverters 18-~ to 18-6 with the open colleetor from "1" to "0" as shown in (f) to (i) of Fig. 7, thus grounding the resistors 18-9 to 18-12 sequentially. Accordingly, the voltage at the output terminal 18-17 is decreased stepwisely as shown in (j) of Fig. 7, which is the reference command voltage for deceleration. In other words, the reference speed command generator circult 18 constitutes a digi-tal-analog ~0 converter -for converting the output of the decodcr circuit .::
~6~73 1 17 into an analog signal.
When the car decelerates and reaches the decele-ration end position, the contact 18-15 is opened, thereby reducing the voltage at the output terminal 18-17 to ~ero.
In order to improve the reliability o~ the circuit of Fig. 6, it is desirable to -take into considera~
tion the matters mentioned below. A reference is made to the case where each of the inverters 18-1 to 18-6 of the reference speed command generator circui-t 18, the decoder circuit 16 and the latch circuit 17 is comprised of not one integrated circuitry but two or more integrated circuits. Assume, ~or example, that the decoder circuit 16 is made up of two integrated circuits each including three NAND elements. It is happened -that not only the individual NAND element is damaged but also -the whole of -the integrated circui-t is damaged. If one o:~ the integrated circuits includes the N.~ND elements 16-1 to 16-3 and the other integra-ted circuit the NAND elements 16-4 and 16-5, ~ -~
for instance, damage of the former integrated circuit would make three successive deceleration positions undetectable. Thus the reference speed command voltage for deceleration which is produced from the terminal 18-17 fails to decrease in the range from deceleration positions Sl to S3, but sharply drops at S~. As a result, the riding comfort is degraded to a great extent and also the car stoppage position is displaced from the desired floor landing position. To overcome this problem, one of the integrated circuits includes N~ND elements 16~
16-3 and 16-5 and the other integt~r.lted circuit NAND
- .. ~. ,. , .: , 6C~73 1 elements 16-2 and 16-~. Namely, the NAND elements in the integrated circuits are combincd alternately. This con-figuration, even i,f one of the integrated circuits is damaged, prevents a sharp change in the speed command as mentioned above, and assures a bearable riding comfort and floor-landing accuracy, thus improving the reliability.
Such a countermeasure is preferably to be made for the latch circui-t 17 and the inverters 18-1 to 18-6.
Referring to the circuit diagram of Fig. 8, the reference speed command voltage produced by the circuit of ~ig. 6 is applied to the acceleration command smoothing circuit 19 and the deceleration command smoothing circuit 20 there~y to produce a smoothly-increasing acceleration command and a smoothly-decreasing deceleration command.
These commands are compared with the speed feedback voltage detec-ted by the circuit of Fig. 2, thus detecting the speed devia-tion for acceleration control and tha-t for deceleration control.
In Fig. 8, the stepped voltage of the reference speed command (the rise portion in (j) of Fig. 7) is applied to the -terminal 18-17 in response to a car start signal. This stepped voltage is applied to the accelera-tion command smoothing circuit 19 including a primary delay circuit composed of resistors 19-1 and 19-2 and a capacitor 19-3. The circuit 19 thus produces a smoothly- -increasing acceleration command voltage as shown in (k) of Fig. 7. This acceleration command voltage is app]ied to the positive terminal of an operation amplifier 21-1 of the acceleration command control comparator circuit 21.
The negative terminal of the operation ~lmpiifier 21-1 is - 20 _ 6~3 1 impressed wi-th the speed feed~ack voltage delivered from the circuit of Fig. 2 through the terminal 13-] and a resistor 21-2. The difference between the acceleration command voltage and the speed feedback voltage is produced 5 at the output terminal 21-5 of the operation amplifier 21-1. During the powering cycle, the contact of the switching circuit 23 of ~ig. 1 is closed on side b, and therefore the voltage difference corresponding to the speed devia-tion is applied to the phase shifter circuit 10 24 and the pulse amplifier circuit 25, so that the thyristors ~CRl and SCR2 are subjected to gate control ;' for car powering control. In the process, the acceleration command voltage is appropriately determined by selecting -the values of the resistors 19-1 and 19-2 and the 15 capacitor 19-3 to attaln car acceleration in a prede- "
termined period of time. Reference numerals 21-3 and 21-4 show resistors.
The car deceleration command is produced from the deceleration command smoothing circuit 20. In other 20 words, the reference speed command voltage (the rise -portion in (j) of Fig. 7) is smoothed by a primary delay circuit composed of resistors 20-1 and 20-2 and a capacitor 20-3, and applied to the buffer amplifier including an ,~
operation amplifier 20-4 and a resis-tor 20-5. The re-25 sulting voltage is a deceleration command voltage smoothly decreasing, as shown in (1) of Fig. 7.
The deceleration command voltage thus obtained is applied through a resistor 22~4 to the negative terminal of an operation amplifier 22-1 of the decel2ration control 30 comparato~ circuit 22. The posi-tive terminal of the ' . ' 6~73 1 operation amplifi.er 20-4 is impressed with the speed feedback command voltage delivered from the circuit of Fig.
2 through the terminal 13-2 and a resistor 22-2. Thus, the operation amplifier 22-1 produces at the terminal 22-6 the difference between the speed feedback voltage and the deceleration command voltage. During deceleration, the contact of the switching circuit 23 in ~ig. 1 is closed on side c and therefore the voltage difference is applied to the phase shifter circuit 24. The phase shifter circuit 24 applies a gate signal corresponding to the above-men-tioned voltage difference to the gates of the thyristors SCRl and SCR2 through the pulse amplifier 25 for effecting deceleration control. Incidentally, reference numerals 22-3 and 22-5 show resistors.
It will be understood :Erom the foregoing descrip-tion that according to the present invention the car position and speed are easily detected by a single AC
tachometer genera-tion. This eliminates the need of separate devices for speed and position de-tection respec-tively unlike the conventional elevator contro] system, resulting in a very low cost configuration. ~urther, an AC tachometer generator is less expensive than a DC tacho- `
meter generator and approximately one-third of the later `-in cost and requires no maintenance or inspection, thus leading to a higher economy and reliability. ~urthermore~
the càr position is detected continually on the basis of the counting value of the counter circuit 15, so that it can be detected with high accuracy and at an optional point. This makes the apparatus according to the present invention applicable to any elcvator system.
l 'rhe abovc dcscription ls made mainly concerning with detection o-f the car posl-tion after initiation of car deceleration, in view of the :Eact -that car position de-tec-tion w:ith h:Lgh accuracy is especially rcquired -for genera-t:ion oE a c1eceleratio1l command. Neverthele~ss, the presentinvention is of eourse applicable also to o-the~r me-t;hods wi.th thc same effect, for example, to a car position detecting method which is convcntionally known ancl in whieh output pulst?s of a pulse generator are counted and -the ear position is deteeted ove~r all the flocrs. In thi.s ease no speeial deviee for speed de-teetion is required cmd the sa111t-~ effec-t as mentioned Wi th re:Et?renCe -to the above-mt-3ntioned embodi1nents is achieved.
When the car reaches the deceleration-initiating point, the deceleration-initiating position detector is ~-act~ated. The reset signa1 generator circuit 12 in Fig.
1 operates in such a manner that, as shown in (b) and (c) of Fig. 7, the reset signal :Eor the counter circuit 15 ., . I . . . . -~ .
. . .
1 changes from "1" to "0", and the reset signal for the lateh circuit 17 from "0" to "1", thereby setting both -the counter circuit 15 and the latch circui-t 17.
At -the same time, the output of the inverter 18-1 with the open collector changes from "1" to "0" as shown in (d) of Fig. 7 and the resistor 18-7 is grounded, so that the voltage at the output terminal 18-17 drops as shown in (j) of Fig. 7.
The counter circuit 15 begins to count. When the pulses applied to the NA~ element 16-1 reach a prede-termined number, the output the NAND element changes from "1" -to "0". Upon application of this output to the latch 17-1, the output of the latch 17-1 changes from "0" to "1" and is held at that value. In response to the output of the latch 17-1, the output of the inverter 18-2 with the open collector ehanges from "1" to "0" as shown in (e) of Fig. 7. The result is that the resistor 18~~ is grounded, thereby further reducing the voltage at the terminal 18-17.
Subsequen-tly, the outputs o~ the ~ elements 16-2 to 16-5 are cha~ged from "1" -to "0", those of latches 17-2 to 17-5 from "0" to "1", and those of the inverters 18-~ to 18-6 with the open colleetor from "1" to "0" as shown in (f) to (i) of Fig. 7, thus grounding the resistors 18-9 to 18-12 sequentially. Accordingly, the voltage at the output terminal 18-17 is decreased stepwisely as shown in (j) of Fig. 7, which is the reference command voltage for deceleration. In other words, the reference speed command generator circult 18 constitutes a digi-tal-analog ~0 converter -for converting the output of the decodcr circuit .::
~6~73 1 17 into an analog signal.
When the car decelerates and reaches the decele-ration end position, the contact 18-15 is opened, thereby reducing the voltage at the output terminal 18-17 to ~ero.
In order to improve the reliability o~ the circuit of Fig. 6, it is desirable to -take into considera~
tion the matters mentioned below. A reference is made to the case where each of the inverters 18-1 to 18-6 of the reference speed command generator circui-t 18, the decoder circuit 16 and the latch circuit 17 is comprised of not one integrated circuitry but two or more integrated circuits. Assume, ~or example, that the decoder circuit 16 is made up of two integrated circuits each including three NAND elements. It is happened -that not only the individual NAND element is damaged but also -the whole of -the integrated circui-t is damaged. If one o:~ the integrated circuits includes the N.~ND elements 16-1 to 16-3 and the other integra-ted circuit the NAND elements 16-4 and 16-5, ~ -~
for instance, damage of the former integrated circuit would make three successive deceleration positions undetectable. Thus the reference speed command voltage for deceleration which is produced from the terminal 18-17 fails to decrease in the range from deceleration positions Sl to S3, but sharply drops at S~. As a result, the riding comfort is degraded to a great extent and also the car stoppage position is displaced from the desired floor landing position. To overcome this problem, one of the integrated circuits includes N~ND elements 16~
16-3 and 16-5 and the other integt~r.lted circuit NAND
- .. ~. ,. , .: , 6C~73 1 elements 16-2 and 16-~. Namely, the NAND elements in the integrated circuits are combincd alternately. This con-figuration, even i,f one of the integrated circuits is damaged, prevents a sharp change in the speed command as mentioned above, and assures a bearable riding comfort and floor-landing accuracy, thus improving the reliability.
Such a countermeasure is preferably to be made for the latch circui-t 17 and the inverters 18-1 to 18-6.
Referring to the circuit diagram of Fig. 8, the reference speed command voltage produced by the circuit of ~ig. 6 is applied to the acceleration command smoothing circuit 19 and the deceleration command smoothing circuit 20 there~y to produce a smoothly-increasing acceleration command and a smoothly-decreasing deceleration command.
These commands are compared with the speed feedback voltage detec-ted by the circuit of Fig. 2, thus detecting the speed devia-tion for acceleration control and tha-t for deceleration control.
In Fig. 8, the stepped voltage of the reference speed command (the rise portion in (j) of Fig. 7) is applied to the -terminal 18-17 in response to a car start signal. This stepped voltage is applied to the accelera-tion command smoothing circuit 19 including a primary delay circuit composed of resistors 19-1 and 19-2 and a capacitor 19-3. The circuit 19 thus produces a smoothly- -increasing acceleration command voltage as shown in (k) of Fig. 7. This acceleration command voltage is app]ied to the positive terminal of an operation amplifier 21-1 of the acceleration command control comparator circuit 21.
The negative terminal of the operation ~lmpiifier 21-1 is - 20 _ 6~3 1 impressed wi-th the speed feed~ack voltage delivered from the circuit of Fig. 2 through the terminal 13-] and a resistor 21-2. The difference between the acceleration command voltage and the speed feedback voltage is produced 5 at the output terminal 21-5 of the operation amplifier 21-1. During the powering cycle, the contact of the switching circuit 23 of ~ig. 1 is closed on side b, and therefore the voltage difference corresponding to the speed devia-tion is applied to the phase shifter circuit 10 24 and the pulse amplifier circuit 25, so that the thyristors ~CRl and SCR2 are subjected to gate control ;' for car powering control. In the process, the acceleration command voltage is appropriately determined by selecting -the values of the resistors 19-1 and 19-2 and the 15 capacitor 19-3 to attaln car acceleration in a prede- "
termined period of time. Reference numerals 21-3 and 21-4 show resistors.
The car deceleration command is produced from the deceleration command smoothing circuit 20. In other 20 words, the reference speed command voltage (the rise -portion in (j) of Fig. 7) is smoothed by a primary delay circuit composed of resistors 20-1 and 20-2 and a capacitor 20-3, and applied to the buffer amplifier including an ,~
operation amplifier 20-4 and a resis-tor 20-5. The re-25 sulting voltage is a deceleration command voltage smoothly decreasing, as shown in (1) of Fig. 7.
The deceleration command voltage thus obtained is applied through a resistor 22~4 to the negative terminal of an operation amplifier 22-1 of the decel2ration control 30 comparato~ circuit 22. The posi-tive terminal of the ' . ' 6~73 1 operation amplifi.er 20-4 is impressed with the speed feedback command voltage delivered from the circuit of Fig.
2 through the terminal 13-2 and a resistor 22-2. Thus, the operation amplifier 22-1 produces at the terminal 22-6 the difference between the speed feedback voltage and the deceleration command voltage. During deceleration, the contact of the switching circuit 23 in ~ig. 1 is closed on side c and therefore the voltage difference is applied to the phase shifter circuit 24. The phase shifter circuit 24 applies a gate signal corresponding to the above-men-tioned voltage difference to the gates of the thyristors SCRl and SCR2 through the pulse amplifier 25 for effecting deceleration control. Incidentally, reference numerals 22-3 and 22-5 show resistors.
It will be understood :Erom the foregoing descrip-tion that according to the present invention the car position and speed are easily detected by a single AC
tachometer genera-tion. This eliminates the need of separate devices for speed and position de-tection respec-tively unlike the conventional elevator contro] system, resulting in a very low cost configuration. ~urther, an AC tachometer generator is less expensive than a DC tacho- `
meter generator and approximately one-third of the later `-in cost and requires no maintenance or inspection, thus leading to a higher economy and reliability. ~urthermore~
the càr position is detected continually on the basis of the counting value of the counter circuit 15, so that it can be detected with high accuracy and at an optional point. This makes the apparatus according to the present invention applicable to any elcvator system.
l 'rhe abovc dcscription ls made mainly concerning with detection o-f the car posl-tion after initiation of car deceleration, in view of the :Eact -that car position de-tec-tion w:ith h:Lgh accuracy is especially rcquired -for genera-t:ion oE a c1eceleratio1l command. Neverthele~ss, the presentinvention is of eourse applicable also to o-the~r me-t;hods wi.th thc same effect, for example, to a car position detecting method which is convcntionally known ancl in whieh output pulst?s of a pulse generator are counted and -the ear position is deteeted ove~r all the flocrs. In thi.s ease no speeial deviee for speed de-teetion is required cmd the sa111t-~ effec-t as mentioned Wi th re:Et?renCe -to the above-mt-3ntioned embodi1nents is achieved.
Claims (15)
1. An elevator control apparatus including a motor for driving a car running in an elevator hoistway, a device for generating a speed command signal in accordance with the position of said car, and a device for controlling said motor in response to said speed command signal and a feedback signal of the speed of said motor; said elevator control apparatus further comprising an AC tachometer generator driven by said car drive motor, a rectifier circuit for rectifying the output of said AC tachometer generator to deliver said speed feedback signal, and a counter for detecting a car position by counting the number proportional to the output frequency of said AC
tachometer generator.
tachometer generator.
2. An elevator control apparatus according to Claim 1, further comprising a waveform-shaping circuit for shaping the waveform of the output of said AC tachometer generator and producing pulses whose number is proportional to the output frequency of said AC tachometer generator, said counter counting the output pulses produced from said waveform-shaping circuit.
3. An elevator control apparatus according to Claim 2, in which said waveform-shaping circuit generates one pulse for each cycle of the output of said AC
tachometer generator.
tachometer generator.
4. An elevator control apparatus according to Claim 1, in which said rectifier circuit comprises a full-wave rectifier bridge circuit including a plurality of diodes, and said counter counts a signal proportional to the output frequency of said AC tachometer generator taken out of one arm of said full-wave rectifier bridge circuit.
5. An elevator control apparatus according to Claim 1, in which said AC tachometer generator is a three-phase AC tachometer generator and said rectifier is a three-phase full-wave rectifier bridge circuit for full-wave rectifying the output of said three-phase AC
tachometer generator, and in which said apparatus further comprises a circuit for shaping a signal proportional to the output frequency of said three-phase AC tachometer generator taken out of one arm of said three-phase full-wave rectifier bridge circuit, into a pulse which is counted by said counter.
tachometer generator, and in which said apparatus further comprises a circuit for shaping a signal proportional to the output frequency of said three-phase AC tachometer generator taken out of one arm of said three-phase full-wave rectifier bridge circuit, into a pulse which is counted by said counter.
6. An elevator control apparatus according to Claim 1, in which said speed command signal generator device generates a speed command signal on the basis of the counting value of said counter.
7. An elevator control apparatus according to Claim 1, further comprising means for detecting -that the car reaches a deceleration-initiating point, said counter being adapted to count the number proportional to the output frequency of said AC tachometer generator after said car has passed said deceleration-initiating point, and said speed command signal generator including means for generating a deceleration command signal on the basis of the counting value of said counter after said car has passed said deceleration-initiating point.
8. An elevator control apparatus according to Claim 7, in which said deceleration command signal generat-ing means includes a decoder for generating a signal at each time when the counting value of said counter reaches one of a plurality of predetermined settings, and a digital-analog converter for generating a deceleration command voltage sequentially decreasing at each time of generation of the output signal of said decoder.
9. An elevator control apparatus according to Claim 8, in which the settings of said decoder are regulated in such a manner that said sequentially-decreasing deceleration command voltage has a constant deceleration rate.
10. An elevator control apparatus according to Claim 8, in which said decoder comprises two integrated circuits each including associated ones of a plurality of elements corresponding to said plurality of settings respectively, said elements of said two integrated circuits being combined alternately with each other.
11. An elevator control apparatus according to Claim 7, further comprising means for applying a count-prohibition signal to said counter before said car reaches the deceleration-initiating point, and means for cancelling the count prohibition after said car has passed said deceleration-initiating point.
12. An elevator control apparatus according to Claim 7, further comprising means for detecting that said car has passed a deceleration end point, said deceleration command signal generator including means for converting said deceleration command signal into a zero speed command signal in response to the output of said deceleration end point passage detector means.
13. An elevator control apparatus according to Claim 8, further comprising means for generating a car accelera-tion command voltage, the output voltage of said digital-analog converter at the time of deceleration start being made coincident with said acceleration command voltage at the time of acceleration end.
14. An elevator control apparatus according to Claim 13, further comprising a switch for applying said acceleration command voltage to the output terminal of said digital-analog converter, and means for generating a reference speed command voltage continuously from car start to car stop at the output terminal of said digital-analog converter.
15. An elevator control apparatus according to Claim 14, further comprising an acceleration command smoothing circuit for smoothing said reference speed command voltage, an acceleration control comparator circuit impressed with the output voltage of said acceleration command smoothing circuit and said speed feedback voltage and producing a difference therebetween, a deceleration command smoothing circuit for smoothing said reference speed command voltage, a deceleration control comparator circuit impressed with the output voltage of said decelera-tion command smoothing circuit and said speed feedback voltage and producing a difference therebetween, and a switching circuit for controlling said drive motor in response to the output of said acceleration control comparator circuit during car powering operation and for controlling said drive motor in response to the output of said deceleration control comparator circuit during car deceleration.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA295,504A CA1096073A (en) | 1978-01-24 | 1978-01-24 | Elevator control apparatus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA295,504A CA1096073A (en) | 1978-01-24 | 1978-01-24 | Elevator control apparatus |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1096073A true CA1096073A (en) | 1981-02-17 |
Family
ID=4110612
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA295,504A Expired CA1096073A (en) | 1978-01-24 | 1978-01-24 | Elevator control apparatus |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1096073A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110386524A (en) * | 2019-08-16 | 2019-10-29 | 钱良楚 | Generally applicable arrival gong |
| CN110386524B (en) * | 2019-08-16 | 2024-05-10 | 钱良楚 | Universal arrival clock |
-
1978
- 1978-01-24 CA CA295,504A patent/CA1096073A/en not_active Expired
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110386524A (en) * | 2019-08-16 | 2019-10-29 | 钱良楚 | Generally applicable arrival gong |
| CN110386524B (en) * | 2019-08-16 | 2024-05-10 | 钱良楚 | Universal arrival clock |
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