INDIVIDUALISED MANAGEMENT SYSTEM FOR MULTIPLE STEPPER MOTORS DESCRIPTION

This invention refers to stepper motor command and control systems.

More particularly, the system constructed according to the disclosed invention is designed to manage a plurality of stepper motors, and specifically a large number of stepper motors associated with batteries of solar radiation captors capable of being oriented to follow the sun's course through the day.

Current stepper motors can be ascribed to two basic construction technologies, unipolar and bipolar.

Unipolar stepper motors are usually provided with four coils arranged in parallel and connected to respective pole pairs. Voltage is applied to one pole, whereas the other pole is connected to ground, or earth.

Operating control of this type of stepper motor is through a system that manages the motor's electricity supply and basically includes contacts arranged in series with each coil; such contacts are operated on command via signals, produced by a control unit, so as to close the circuit between the input pole and the ground pole when the motor is to be activated, and conversely to open the circuit when the electricity supply must be stopped.

The direction of the motor's rotation is determined by appropriate alternation of the closure of the contacts of the various coils. Motor speed, on the other hand, is defined by the frequency of contact opening-closure.

Bipolar stepper motors are provided with two coils that are alternately energised with AC by impulse trains generated by a supply driver. In this case the control means interact directly with the driver through a suitable bus, and the two coils are then energised by the driver accordingly.

Despite the different implementation technologies, the two types of stepper motor share the characteristic that, in the prior art, one control system can manage no more than one or at most two motors.

For this reason, and to the applicant's knowledge, there are no known art applications in which a large number of stepper motors are served by a single motor. In fact, in the prior art the control systems multiply in direct proportion to the number of users, with a consequent increase in cost and installation complications, and a reduction in the general reliability of the users being served.

The object of the present invention is to obviate to such disadvantages by making it possible to use multiple stepper motors, at the occurrence combined in large groups, thus overcoming the intrinsic limitations of the management systems that are typical of the prior art.

In line with the invention such object is met by an individualised management system for multiple stepper motors compliant with claim 1 and, in particular, including technical features described in one or more of the attached claims.

The technical features of a system constructed according to the disclosed invention for the above-mentioned scope, and its advantages, will be apparent from the detailed description that follows, made with reference to attached drawings of a purely exemplary embodiment, which is illustrative but does not limit the invention, in which:

- figure 1 is a functional diagram of the supply and control system for a single unipolar stepper motor operating according to the prior art;

- figure 2 is a functional block diagram of an individualised management system for multiple unipolar stepper motors constructed according to the disclosed invention;

- in figure 3, drawings 3A to 3E illustrate several possible implementations of the physical devices symbolically represented by blocks in figure 2;

- figure 4 is a functional block diagram of a variant of the supply system shown in figure 2, with unipolar stepper motors;

- in figure 5 drawings 5A to 5G illustrate some possible implementations of the physical devices symbolically shown in figure 4;

- figure 6 is a functional diagram of the supply and control system for a single bipolar stepper motor operating according to the prior art;

- figure 7 is a functional block diagram of an individualised management system for multiple unipolar stepper motors realised as a variant of the diagram in figure 2; - in figure 8 drawings 8A to 8C represent some possible implementations of the physical devices symbolically represented by blocks in figure 7;

- figures 9 and 10 are functional block diagrams representing diagnostic systems for checking correct step execution by each of the motors shown in the diagrams of figures 2 and 4.

With reference to the figures shown in the attached drawings, in figure 1 the number 50 identifies a unipolar stepper motor, while the number 60 indicates a diagram of a local controller of the state commutation of motor 50 - activated/deactivated - both realised according to the prior art.

More particularly, motor 50 is provided with four coils L1 ,L2,L3,L4 that are connected upstream to a pole 2 connected electrically to a positive, predefined voltage supply VCC, and selectively connected downstream via an equal number of contacts K1 ,K2,K3,K4, arranged in series with said coils L1 ,L2,L3,L4, to a pole 3 connected electrically to ground or earth, or having a generally lower electrical potential than pole 2.

Contacts K1 ,K2,K3,K4 are normally open and can be closed, or vice versa, using digital output commands DO(K1 ) DO(K2) DO(K3) DO(K4) generated by a control unit 60a, symbolically represented, which can be implemented, for instance, by means of a PLC, a PC, or a dedicated system.

By appropriately alternating the closure of contacts K1 ,K2,K3,K4, motor 50 will rotate in one of the two rotation directions. Varying the commutation frequency of contacts K1 ,K2,K3,K4, on the other hand, will determine the rotation speed of motor 50.

Figure 2 illustrates a network, indicated overall as 5, in which multiple motors M(i,j) of the type described above are energised, controlled and regulated by an individualised management system, designated overall as 1 , which is the specific subject of this invention.

Basically, network 5 consists of a number of horizontal branches (illustrated graphically in figure 2), henceforth defined as row connections 6, and a number of vertical branches, defined as column connections 7.

Row connections 6 are connected to ground pole 3 which, as will be clearer later, is integrated into block 4.

Column connections 7 are connected to a common conductor connected to the electric power supply pole having potential VCC, which is to be considered as being associated with block 2.

Row connections 6 and column connections 7 connect to a plurality of nodes, indicated as 8, to which an equal number of motors M(i,j) of the type represented in figure 1 are connected.

The position of each motor M(i,j) in network 5, namely the position of each node 8 connected to it, is unequivocally identified by two co-ordinates (i,j); the former indicating the row connection to which the motor M(i,j) belongs, the latter indicating the column connection to which the motor M(i,j) also belongs.

The position of each motor M(i,j) in network 5 is therefore defined by a matrix of addresses (i,j) that are unique for each motor M(i,j).

Figure 3 shows in greater detail the meaning of the blocks shown in the diagram of figure 2.

In the detail "A" of figure 3 it can be noted that block 1 1 in figure 2 represents a column contactor, the term contactor indicating a device that can open or close one or more physical contacts (e.g. mechanical relays) or virtual contacts (i.e. means performing equivalent functions but realised with different technologies).

Contactor 1 1 can be constituted even by a single, open contact K, implemented for instance by means of a mechanical relay or a transistor. Contact K can be ordered to close by a command signal 10', represented by a digital output signal DO(j) issued by general control means 9 of management system 1 .

The closure command of contact K in block 1 1 of one or the other column connection 7 therefore allows electrical connection of poles 2 and 3 through the column connection 7 itself.

The same figure 3A also shows that the generic block 1 1 , besides representing the contactor solution just described, is also consistent with a variant, where the whole column connection 7 is directly supplied by tension VCC.

A similar solution can be seen in drawing "C" of figure 3, illustrating a possible embodiment of a row contactor 12 for network 5 of figure 2. Said contactor has four normally open contacts that can be commutated by a 10" command signal, it, too, represented by a digital output signal DO(i) produced by general control means 9 to ground selectively one or the other row connection 6 in network 5.

Column connections 7, supplying motors M(i,j) upstream of coils L1 ,L2,L3,L4, can be realised with single-conductor cables.

Conversely, row connections 6 are implemented as four-conductor cables, with one conductor per coil L1 ,L2,L3,L4 of each motor M(i,j).

Row connections 6 can be realised advantageously and economically with conventional network cable including, for instance, an RJ45 data transmission connector.

Therefore control means 9, through the signal pair 10' and 10", i.e. DO(j) DO(i), are capable of energizing each motor M(i,j) in network 5 separately and selectively.

Drawing "B" of figure 3 shows an embodiment of the physical devices that in network 5 of figure 2 are designated as block 8. Said block 8 represents the node structure formed by the four conductors or cables, issuing from coils L1 ,L2,L3,L4 of a generic motor M(i,j), interconnecting with an equal number of conductors which - in row connections 6 - connect in series the homologous coils of two consecutive motors M(i,j-1 ) M(i,j+1 ), namely two motors found on the same row connection 6 but belonging to two adjacent column connections 7 in network 5.

The use of diodes 13 downstream coils L1 ,L2,L3,L4 of motor M(i,j), and before the interconnection of said coils to the homologous conductors of row connections 6, allows the actuation of the screening means assuring the separate activation of motor M(i,j), upon command from control means 9, without electrical interference with the remaining motors M(i,j) of network 5.

In drawing "D" of figure 3 it can be noted that block 4 designates state commutation switch actuators that serve all motors M(i,j) in network 5. In fact, their location upstream of ground pole 3 and their being shared by all row connections 6 enable switch actuators 4, as a result of the commutation of respective contacts K1 ,K2,K3,K4, to ground motor M(i,j) each time it is connected to pole 2. The functioning of management system 1 of network 5 can be explained with the help of figure 2 by noting that, in relation to input signals from the specific user served by management system 1 , general control means 9 of network 5 issue digital outputs 10', 10" namely DO (i,j), which connect the generic motor M(i,j) to the supply pole 2 and the ground pole 3 by energizing the row connection 6 and the column connection 7 of the relevant motor M(i,j).

After addressing motor M(i,j), switch actuators 4 send the activation sequence signal to its coils L1 ,L2,L3,L4 through control 4a, associated with row connections 6.

Depending on the sequence, the selected motor M(i,j) rotates in one or the other direction, whereas the intensity of its rotational speed is determined by the commutation frequency.

Therefore a management system 1 designed in this way allows individualised, selective management of any motor M(i,j) in network 5, which can comprise large numbers of motors M(i,j) without any management difficulties arising.

The above-mentioned row connections 6 and column connections 7 are preferably implemented as conductors consisting physically of cables suitable for signal conduction. This sort of solution, in cabled form, should nonetheless be considered as purely indicative and does not limit the invention, since it is clear that some components of network 5 could also be realised in wireless form, i.e. a form that transmits signals via electromagnetic waves.

The management system 1 described above has a very broad range of applications. One example, but by no means the only one, is the use of motors M(i,j) to drive activation means of solar radiation captors in systems exploiting solar energy.

Management system 1 appears especially advantageous in such applications, since it is capable of orienting even large numbers of captor batteries, each fitted with one or two gear motors of stepper type, to follow the sun's course through the day. So it is clear that in this case control means 9 of management system 1 , which issue digital address signals DO (i,j) to the various motors M(i,j), are driven by input signals from the sun tracking system.

Since in such applications position adjustments are achieved by short cycles of activation of motor M(i,j), separated by relatively long time intervals, it is clear that a management system 1 realised according to the disclosed invention can manage as many as several hundred motors M(i,j) easily, reliably and with very low installation and running costs.

Figure 4 illustrates an operating variant of the invention represented in figure 2. It should be noted that in this variant the elements corresponding to those reported in figure 2 have the same numbering, but increased by one hundred. Moreover, for the sake of brevity the description that follows is substantially limited to the embodiments of this solution; the reader is referred to figure 2 for any aspect that is not explicitly described.

Like figure 3, figure 5 reports some drawings of the physical devices symbolically represented in figure 4.

Drawing "A" of figure 5, showing contactors 1 1 1 of column connection 107, requires no particular description, since it is substantially identical to drawing "A" of figure 3. Drawings "B" and "C" of figure 5 highlight the fact that row 106 and column 107 connections can both be implemented as a single-conductor cable connection (either permanent or commutable, using a single-contact contactor) to the respective poles 3 and 2. In this case, block 3 shows a ground connection passing through and associated with row connections 6 (see drawing "E" of figure 5).

The most significant part of this variant is illustrated in drawings "E" and "F" of figure 5, where each node 108 in network 5 can be seen to comprise a transistor array 27 operatively associated with the corresponding motor M(i,j). In drawing "E" of Figure 5 transistor array 27 presents a first series of pins N',E',S',W connected to coils L1 ,L2,L3,L4 of motor M(i,j), and a second series of pins, set opposite to the pins of the first series and designated N,E,S,W, connected to corresponding conductors of row 106 and column 107 connections (see drawing "F" in figure 5). The commons 25 of transistor arrays 27 are grounded to conductor 26 of row connection 106, conductor 26 connecting adjacent motors M(i,j-1 ) and M(i,j+1 ).

As shown in drawing "F" of figure 5, all nodes 108 are connected by a four-conductor cable serving simultaneously all transistor arrays 27 in network 105 and transmitting the signal sequence for grounding coils L1 ,L2,L3,L4, for separate activation of motors M(i,j).

Application of potential VCC to one of the pins N,S,E,W of transistor array 27 results in connection of the corresponding pin N',S',E',W, and consequently of the coil of motor M(i,j) connected to it, to the common 25 of transistor array 27, which is grounded.

Signals for grounding coils L1 ,L2,L3,L4 of motors M(i,j) are generated by switch actuators 104 upon command from control means 9. In the case in point said switch actuators 104 comprise control means 104a that issue digital commands DO(N), DO(S), DO(E), DO(W) to the corresponding conductors of the four-conductor cables N,S,E,W, and which generate the sequence for activating motor M(i,j).

Figure 6 shows a diagram of a bipolar-type stepper motor 70 constructed according to the prior art, whose supply/control system is designated overall as 80.

Functioning of motor 70 is determined by a dedicated driver unit 80b, which generates impulse trains for alternately energising coils L1 ,L2, upon a command signal received from a control unit indicated as 80a.

Multiple bipolar-type motors M(i,j) can be implemented in a network 205 shown in figure 7.

The topology of network 205 is substantially identical to that of the network in figure 2; the corresponding elements in the network of figure 7 have the same numbering, but increased by two hundred units, to mark their belonging to this third variant of the invention.

Drawings "A", "B" and "C" of figure 8 illustrate some possible implementations of the elements symbolically represented in figure 7.

Drawings "A" and "B" of figure 8 show that column contactors 21 1 of figure 7 are provided with two normally open contacts K set parallel to each other on two conductors 30 that energise the ends of a first coil L1 of each motor M(i,j) found along column connection 207 (j-th column). Similarly, row contactors 212 envisage two mechanical relay contacts that energise the ends of a second coil L2 of each motor M(i,j) lying on the same row connection 206 (i-th row). Upon an external command issued by control means 9, digital outputs DO(j) and DO(i), generated by switch actuators 204, supplied by pole 2 (see drawing "C" of figure 8), activate each motor M(i,j) found at the level of the node 208 on which the column (j) and the row (i) addressed depend.

Both unipolar solutions shown in figures 2 and 3 and in figures 4 and 5 are highly suitable for the implementation of diagnostic means 20,120 directed at establishing whether whichever network 5,105 motor M(i,j) has been activated has correctly executed the discrete number of steps commanded.

This is accomplished, in management system 1 , by an electrical signal analyser 20a placed near ground pole 3, where the currents flowing through coils L1 ,L2,L3,L4 of whichever motor has been activated M(i,j) are grounded (figure 9). The current signal acquired in real time by analyser 20a is compared to a previously memorised reference waveform of the correct operation of a motor M(i,j) under the action of respective switch actuators 4,104, to establish whether whichever motor M(i,j) is running at the time is working as commanded or is operating in an abnormal way. Figure 10 illustrates diagnostic means 120 implemented as described above and operated so as to interact on one side with ground pole 3 and on the other with state commutation switch actuators 104 of motors M(i,j), realised in this case according to the embodiment envisaging the activation of transistor arrays 27.

Basically, diagnostic means 20,120 provide a feedback that makes the operation of management system 1 , constructed according to the disclosed invention and comprising stepper motors intended to operate with open-ring circuit control, similar to that of a closed-ring system, without having to resort to the complex topology and components typical of the latter system.

The invention thus conceived is clearly optimally suited to industrial applications; it can also be modified to obtain countless variations, all within the sphere of the invention concept; moreover, all components can be replaced by technically equivalent elements.