NL1005045C2 - Motor drive control system for automatic production line - Google Patents

Abstract

A product moves along a production conveyor belt (10), where a series of operations are carries out by machine tools at processing stations (11, 12, 13). Each of the machine tools has an individual drive motor (21, 22, 23). The speed of each motor is controlled by an individual control unit (100, 200, 300). A movement detector at the first station (11) measures the operating speed of the first "master" motor (11). That measurement is used to ensure that the speed difference ratio between the master motor (11) and the subsequent "slave" motors (12, 13) is maintained.

Description

Title: Control device

The invention relates to a control device for an actuator such as, for example, a motor.

It is quite common in practice for a production line to have two or more consecutive machining stations, each of those machining stations having movable parts to be driven by a motor. For the production line to function efficiently, it is desirable that the speeds at which those processing stations operate are matched.

A possible way to accomplish this is to provide the production line with a single drive motor, and to couple each machine to that single drive motor via a mechanical transmission system. However, there are some drawbacks to this. First, a motor of sufficient power is required to drive all the processing stations of the production line. Secondly, it is not easy to move a machine, or to replace or add a machine.

It is therefore desirable that a machine, or a module comprising several processing stations, be provided with its own drive motor. It is desirable here that the rotational speeds of the different drive motors are adapted to each other.

The object of the invention is to provide a relatively simple and inexpensive synchronization unit with which the rotational speed of a secondary motor, which will hereinafter also be referred to as a slave motor, can be adapted with a good degree of accuracy to the rotational speed of a primary motor, which will also be referred to hereinafter as master motor. It should be noted that it is not necessary for the speeds of the primary motor and the secondary motor to remain as accurate as possible in absolute terms: if the speed of rotation of the master 1005045 2 motor increases or decreases, the speed of rotation of the slave motor should be increase or decrease equally.

According to the present invention, this object is achieved by a control device as described in claim 1.

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These and other aspects, features and advantages of the present invention will be elucidated by the following description of a preferred embodiment of a synchronization unit according to the invention, with reference to the drawing, in which: figure 1 schematically shows a block diagram of a drive system; Figure 2 schematically shows a block diagram of a master controller; Figure 3 schematically shows a block diagram of a slave control device.

Figure 1 schematically illustrates a conveyor belt 10 with multiple processing stations 11, 12, 13, of which are outlined in Figure 3. Each processing station 11, 12, 13 is provided with its own drive motor 21, 22, 23. In the following, the first motor 21 will be referred to as the primary motor or master motor, and the subsequent motors 22, 23 will be referred to as secondary motors or 25 slave motors.

The master motor 21 is controlled by a master controller 100, while the slave motors 22, 23 are controlled by slave controllers 200 which according to the present invention may be mutually identical, for which reason only one slave controller 200 will be described in more detail below. will be discussed.

It should be noted that in Figure 1 the slave controller 200 for the third motor 23 is coupled to the slave controller 200 for the second motor 22. However, it will be appreciated that the slave controller 200 for the third motor 23 is also connected directly to the master. control device 100 may be coupled.

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Figure 2 shows in more detail an exemplary embodiment of the master controller 100. The master motor 21 has an output shaft 31, which is coupled via a transmission system 32, which usually has a speed-reducing function, to a drive shaft 33 of the processing station 11. The master controller 100 includes a master controller 110 programmed to give the master motor 21 a desired speed pattern. By this is meant that the speed of the master motor 21 can have a desired, predetermined constant value, but it is also possible that the speed of the master motor 21 can be varied in a desired, predetermined manner as a function of the time. The master controller 110 has an output 111 for providing a motor control signal S1. By way of example, the master motor 21 may be a frequency-controlled three-phase motor which is provided with a frequency controller 34 which receives said motor control signal SI. As a variant, the frequency controller 34 may be part of the master controller 20 100.

The master controller 100 has a first slave output 101 coupled to said output 111 of the master controller 110, to make said motor control signal SI available to a slave controller 25 200, as will be explained in more detail.

An angle detector 35 is coupled to the output shaft 31 of the master motor 21, an output of which is coupled to an input 113 of the master controller 110. The angle detector 35 is arranged to provide an angle signal S2 30 whenever the output shaft 31 of the master motor 21 is rotated by a predetermined angle. By way of example, the angle detector 35 may include a segmented disk having, for example, 512 segments, and a signal generator coupled to that segmented disk, which includes, for example, an opto-coupler, as schematically illustrated in Figure 2. In such a case, it exists angle signal S2 thus consists of 512 pulses per revolution of the output shaft 31 of the 1 0 0 5 0 45 4 master motor 21. However, it will be clear to a skilled person that the angle detector 35 can be of any other suitable construction and that use can be made of angle detectors known per se, wherein the above-mentioned number of 512 pulses per revolution can be chosen to be larger or smaller as desired.

A control loop is provided by the signals S1 and S2 for the master motor 21. via the angle signal S2 received at its input 113, the master controller 110 checks whether the rotation of the output shaft 31 of the master motor 21 corresponds with the desired pattern; if deviations occur, the master controller 110 adjusts the motor control signal SI to eliminate the deviations.

The master controller 100 has a second slave-15 output 102 coupled to said input 113 of the master controller 110, to make said angle signal S2 available to a slave controller 200, as will be explained in more detail.

Figure 3 shows in more detail an exemplary embodiment of the slave controller 200. The slave controller 200 has a first master input 201, which is preferably connected as shown to a first slave coupling output 204. The first master input 25 is 201 intended to receive said motor control signal SI, for which purpose the first master input 201 can be coupled to the first slave output 101 of the master controller 100 or to the first slave couple output of another slave controller. The slave control device 200 includes a slave controller 210, which may be, for example, a suitably programmed microprocessor, and a control input 212 of which is connected to the first master input 201 to receive said motor control signal SI.

The slave controller 210 has an output 211 for providing a slave motor control signal S3. By way of example, the slave motor 22 may be a frequency-controlled three-phase motor which is provided with a frequency controller 44 which receives said slave motor control signal S3. As a variant, it is possible that the frequency controller 44 forms part of the slave control device 200. The slave motor 22 has an output shaft 41, which is coupled to a drive shaft via a transmission system 42, which usually has a speed-reducing function. 43 of the processing station 12.

It is noted that it is possible that the motors 21 and 22 are mutually identical, and the same applies to the frequency controllers 34 and 44. In that case, in the first approximation, the slave motor control signal S3 can be identical to the master motor control signal. SI. It will be understood, however, that it is possible that the motors 21 and 22 are different from each other and / or that the frequency controllers 34 and 44 are different from each other, in which case the slave controller 15 210 is suitably a slave motor control signal S3 based on the master motor control signal S1 and adapted to the respective motor 22 and / or frequency controller 44 such that the slave motor 22 is synchronized with the master motor 21.

In the first approach, the slave controller 210 provides the slave motor control signal S3 based on the master motor control signal SI. In order to check whether the slave motor 22 indeed maintains the desired rotational speed, or follows the desired rotational speed pattern, the slave motor 22 could be provided with an accurate rotation detector, comparable to the angle detector 35 shown in figure 2 for the master motor 21. However, this is not desirable, because such a detector is rather expensive due to the required accuracy. According to an important aspect of the present invention, said check is performed on the basis of the angular signal S2 from said angle detector 35. To this end, the slave control device 200 has a second master input 202, which is preferably and as shown, connected to a second slave coupling output 205, and which is intended to receive said angular signal S2, to which the second master input 202 can be coupled. with the second slave output 102 of the master controller 1005045 6 100 or with the second slave torque output of another slave controller. The slave controller 210 has a detector input 213 which is connected to the second master input 202 to receive said angular signal S2.

According to an important aspect of the present invention, the processing station 12 is provided with a signal generator 51, which is arranged to give a period signal Sp to the slave controller 210 at predetermined phase moments in the processing cycle of the processing station 12. The slave controller 210 has a period input 214 for receiving the period signal Sp, and is arranged to count the number of Nx angular signals S2 received at its detector input 213 between two consecutive period signals Sp.

Under normal circumstances, that number Nx will be equal to a previously known number Nq. If at any time the counted number of pulses Nx between two consecutive period signals Sp is greater than No, the time between two consecutive period signals Sp is apparently greater than normal, which means that the slave motor 22 is running too slowly. Conversely, if at any time the counted number of pulses Nx between two consecutive period signals Sp is less than No, the time between two consecutive period signals Sp is apparently less than normal, which means that the slave motor 22 is running too fast.

The slave controller 210 is therefore arranged to compare the counted number of pulses Nx between two consecutive period signals Sp with the predetermined value No, and to correct the slave motor control signal S3 on the basis of the result of that comparison, ie make the slave-30 motor 22 run faster or slower, in order to correct a deviation between Nx and No.

The signal generator 51 can be a relatively simple signal generator, and can for instance be a fixed mechanical switch which cooperates with one or more cams 52 driven by the slave motor 22. Various positions are conceivable for the signal generator 51. For example, the signal generator 51 are disposed at the output shaft 41 of the slave motor 22, and one cam 52 can be formed on that output shaft 41, so that the signal transmitter 51 gives one pulse per revolution of that output shaft 41: in that case No is equal to the number of pulses that the detector 35 gives per revolution of the output shaft 31 of the master motor 21, that is to say in the aforementioned example equal to 512. However, the signal generator 51 may also be arranged after the transmission 42, and, for example, give one pulse per revolution of the output shaft 43 of the transmission 42: in that case, No, in comparison with the illustrated arrangement of the signal generator 51 at the output. on the shaft 41 of the slave motor 22, multiplied by the transmission ratio of the transmission 42.

In the following, it will be assumed that the drive shafts 33, 43 of the processing stations 11, 12 are cycle-15 shafts, which means that the driving shafts 33, 43 of the processing stations 11, 12 make one revolution per working cycle of the processing stations 11, 12 If the signal generator 51 gives one pulse per revolution of the output shaft 43 of the transmission 42, for example because one cam is arranged on the output shaft 43 of the transmission 42 to cooperate with the signal generator 51, the synchronization check takes place once per work cycle of the processing station 12, the resolution of that control being quite large, namely equal to the number of 25 pulses that the angle detector 35 gives per revolution of the output shaft 31 of the master motor 21, multiplied by the transmission ratio of the transmission 42. In general, the accuracy achieved by this is sufficient, although during the course of the duty cycle no synchronization check of the processing station 12 takes place. Within the scope of the present invention it is possible to choose the number of synchronization checks during the working cycle of the processing station 12 larger than one, namely by arranging the signal generator 51 such that these two or more period signals Sp gives per working cycle of the processing station 12. This can be done, for example, by providing the drive shaft 43 of the processing station 12 with 1005045 8 several cams which cooperate with the signal generator 51, or by placing the signal generator 51 at the output shaft 41 of the slave motor 22, which output shaft 41 can optionally be provided with several cams.

It is achieved by such a larger control frequency that the maximum deviation that can occur can be reduced at any time during the working cycle of the processing station 12. On the other hand, however, the signal generator 51 must be able to operate faster, and the available calculation time for the controller 210 is less. Furthermore, the control action of the controller 210 is complicated because, due to a possible speed variation of the master motor 21 during the duty cycle and a possible phase difference between the master motor 21 and the slave motor 22, 15 in that case, the nominal pulse numbers Nx between two consecutive signals Sp need not be the same.

As mentioned, it may be desirable to drive the master motor 21 and thus also the slave motor 22 at a constant speed, but it may also be desirable to drive those motors at a variable speed, the speed being varies in time according to a predetermined pattern. In principle, it may also suffice in the latter case that the slave controller 210 ensures that the duration T12 of the operating cycle of the processing station 12 is equal to the duration Tn of the operating cycle of the processing station 11, which duration in the following will be referred to as Tc. In general, however, it is desirable that a pre-specified and preferably adjustable phase difference be present between the duty cycle of the processing station 11 and that of the processing station 12.

Preferably, therefore, means are provided for providing phase information to the slave controller 210.

The figures illustrate an example of such phase information means.

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Figure 2 shows that the drive shaft 33 of the master machine 11 is provided with a master cycle signal transmitter 60, which gives a master cycle signal Smc once per revolution of the drive shaft 33. This master cycle signal transmitter 60 may, in a manner similar to that discussed above with regard to the signal transmitter 51, be a simple, relatively inexpensive signal transmitter, for instance a mechanical proximity switch which is operated by a cam mounted on the drive shaft 33. The master cycle signal generator 60 is connected to a third slave output 103 of the master controller 100.

Similarly, the slave controller 200, as illustrated in Figure 3, includes a slave cycle signal generator 53, which provides a slave cycle signal Ssc once per revolution of the drive shaft 43. The slave cycle signal generator 53 is connected to a slave cycle input 216 of the slave controller 210.

The slave controller 200 has a third master input 203, which is preferably and as shown, connected to a third slave couple output 206. The third master input 203 is adapted to receive said master cycle signal, for which purpose the third master input 203 can be coupled to the third slave output 103 of the master controller 100 or to the third slave couple output of another slave controller. The slave controller 210 has a master cycle input 215 which is connected to the third master input 203 to receive said master cycle signal S ^ c.

The slave controller 210 further has a slave phase input 30 207 for receiving a slave phase signal φ which is representative of the desired phase difference of the slave device 12 from the master device 11. For example, the slave phase signal φ are defined by a manually adjustable potentiometer, as will be apparent to one skilled in the art.

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According to the present invention, therefore, a control device is provided, wherein a slave controller 210 in a first approximation provides a slave motor control signal S3 based on a master motor control signal S1. At 5 fixed phase moments during the duty cycle of the slave device 12, the slave controller 210 checks whether the slave motor 22 is in line with the master motor 21, for which purpose an angle obtained from the master motor 21 is used. signal S2 is used as counter signal. If desired, the slave controller 210 maintains a predetermined phase difference between the duty cycle of the slave device 12 and the duty cycle of the master device 11 based on a slave phase signal φ.

An important advantage offered by such a control device is that only one encoder 35 is required for accurately driving several motors; more specifically, no encoder is required for the slave motors.

In a test arrangement, a cam with four 20 cams 52 was coupled to the output shaft 41 of the slave motor 22, so that the signal generator 51 gave four period signals Sp per revolution of that output shaft 41. At a constant revolution speed of the master motor 21 the angular position of the output shaft 41 of the slave motor 22 was measured using an angular position detector similar to the previously described detector 35. That angular position was found to deviate less than 1 ° from the intended position. It has thus proved possible to provide a relatively accurate synchronization with relatively simple and inexpensive means.

It will be clear to a person skilled in the art that the scope of the present invention as defined by the claims is not limited to the embodiments shown and discussed in the drawings, but that it is possible to show the embodiments of the control device according to the invention shown within the scope 1005045 11 of the inventive concept.

For example, it is possible that the signalers have a different construction. For example, a signal generator can be a magnetic, inductive or optical signal generator, as will be clear to a person skilled in the art.

For the sake of clarity, two separate signalers 51 and 53 for the slave controller 210 have been described, in which the signal Sp provided by the signaler 51 is used for synchronization and the signal Ssc provided by the signaler 53 is used as a reference in the maintaining a phase relationship. The signal Ssc is provided once per duty cycle, while the signal Sp can be provided multiple times per duty cycle. However, since, as described, the signal Sp can in principle also be provided once per operating cycle, it is possible to also use the signal Sac provided by the signal generator 53 as the synchronization signal Sp, so that the signal generator 51 can then be omitted.

It is further noted that the processing stations need not be part of a production line; the present invention is applicable in any situation where multiple processing stations have to cooperate with each other, or where it is desirable for any reason that the rotational speeds of multiple motors be adapted to each other.

Although the present invention has been specifically explained above for an application example where the actuators to be controlled are motors with an output rotary axis, it will be clear to a person skilled in the art that the present invention also applies to actuating actuators of another type. By way of example, one or more of the actuators to be controlled can be a linear motor with a linearly displaceable output member. In such a case, instead of "angular velocity of the output shaft", read "linear velocity of the output member". It will be clear to a person skilled in the art how, in such a case, signals Sp and Sac referred to the 1005045 12 can be derived from the movement of that output member.

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Claims (13)

A controller for a system of two or more actuators (21; 22), comprising a master controller (100) for a master actuator (21) and a slave controller (200) for a slave actuator (22); The master controller (100) comprising: a displacement detector (35) arranged to provide a displacement signal (S2) indicative of displacement of the output means (31) of the master actuator (21); 10. a master controller (110) with an output (111) for providing a master actuator control signal (SI), and an input (113) for receiving the displacement signal (S2); a first slave output (101) coupled to said output (111) of the master controller (110); a second slave output (102) coupled to said input (113) of the master controller (110); and wherein the slave controller (200) comprises: a slave controller (210) with an output (211) for providing a slave actuator control signal (S3); a first master input (201) coupled to the first slave output (101) of the master controller (100), which first master input (201) is connected to a control input (212) of the slave-25 controller (210); a second master input (202) coupled to the second slave output (102) of the master controller (100), which second master input (202) is connected to a detector input (213) of the slave-30 controller (210); a signal generator (51) for providing a period input (214) to the slave controller (210) with a period signal (Sp) at predetermined phase times in a process cycle; 1005045 wherein the slave controller (210) is arranged to count the number (Nx) of displacement signals (S2) received at its detector input (213) between two consecutive period signals (Sp); to compare the counted number of pulses (Nx) with 5 a pre-entered value (No); and to correct the slave actuator control signal (S3) based on the result of that comparison to eliminate a deviation between (Nx) and (No). A control device according to claim 1, wherein said signal generator (51) cooperates with the output member (41) of the slave actuator (22). Control device according to claim 1, wherein said signal generator (51) cooperates with a drive shaft (43) for a slave processing station (12). Control device according to any of the preceding claims, wherein the slave control device (200) has a first slave coupling output (204) connected to the first master input (201); and wherein the slave controller (200) has a second slave link output (205) connected to the second master input (202). Control device according to any one of the preceding claims, wherein phase information means (Smc / Ssc, φ) are provided. 6. Control device according to claim 5, wherein the master control device (100) comprises a master cycle signal transmitter (60) which gives a master cycle signal (SmC) once per revolution of a drive shaft (33) for a master processing station (11), and from a third slave output (103) connected to the master cycle signal generator 35 (60); the slave control device (200) comprising a slave cycle signal generator (53) which, once per revolution of 1005045, provides a drive shaft (43) for a slave processing station (12) with a slave cycle signal (Ssc), which slave cycle signal generator (53) is connected to a slave cycle input (216) from the slave controller (210); 5 wherein the slave controller (200) has a third master input (203) coupled to the third slave output (103) of the master controller (100), which third master input (203) is connected to a master cycle input (215 ) of the slave controller (210); 10 and wherein the slave controller (210) has a slave phase input (207) for receiving a slave phase signal (φ). The control device of claim 6, wherein the slave control device (200) has a third slave couple output 15 (206) connected to the third master input (203). A master controller (100) for use in a controller according to any one of claims 1-7, comprising: 20. a displacement detector (35) adapted to provide a displacement signal (S2) indicative of displacement of the output means (31) of a master actuator (21); a master controller (110) with an output (111) for providing a master actuator control signal (SI), and an input (113) for receiving the displacement signal (S2); a first slave output (101) coupled to said output (111) of the master controller (110); and 30. a second slave output (102) coupled to said input (113) of the master controller (110). The master controller of claim 8, comprising a master cycle signal generator (60) providing a master cycle signal (SmC) once per revolution of a drive shaft (33) for a master processing station (11), and comprising a third slave output (103) connected to said master cycle signal generator (60). 1005045 Slave control device (200) for use in a control device according to any one of claims 1-7, comprising: a slave controller (210) with an output (211) for providing a slave actuator control signal (S3); - a first master input (201) connected to a control input (212) of the slave controller (210); a second master input (202) connected to a detector input (213) of the slave controller (210); A signal generator (51) for providing a period input (214) to the slave controller (210) with a period signal (Sp) at predetermined phase times in a process cycle; wherein the slave controller (210) is arranged to count the number (Nx) of displacement signals (S2) received at its detector input (213) between two consecutive period signals (Sp); to compare the counted number of pulses (Nx) with a pre-entered value (No); and to correct the slave actuator control signal (S3) based on the result of that comparison to correct a deviation between (Nx) and (No). The slave control device of claim 10, further comprising a first slave couple output (204) connected to the first master input (201), and a second slave couple output (205) connected to the second master input (202). The slave controller of claim 10 or 11, 30 further comprising a third master input (203) connected to a master cycle input (215) of the slave controller (210), and a slave phase input (207) for receiving a slave phase signal (φ). The slave controller of claim 12, further comprising a third slave couple output (206) connected to the third master input (203). 1005045