SYSTEM FOR INTERCONNECTING SENSOR AND ACTUATING DEVICES

Abstract: A system (10) for connecting sensor devices (11) to actuating devices (12), the system (10) substantially compris­ ing a cable (13) having a given number of signal conducting lines (1, 2, 3, 4, 5), a number of interface units (14, 15) each designed for assembly between the lines (1, 2, 3, 4, 5) of the aforementioned cable (13) and a respective sensor device (11) or actuating device (12), and processing means (16) designed to circulate, in the aforementioned cable (13), signals (v₂, v₃, v₄) enabling data to be transmitted between the devices (11) and (12) and the processing means (16).

Description: The present invention relates to a system for interconnecting sensor and actuating devices, of the type defined in the preamble of claim 1. On electronic control systems, analogue signal transfer and order distribution have become such a serious problem that the wiring involved often constitutes the most critical part of the system in terms of reliability, complexity (both design and production), weight, fault diagnosis and cost, especially when it comes to transferring analogue signals. Wiring, in fact, may be said to be a real hindrance to the extraordinary potential of electronic systems which, for years now, have continued to register a steady fall in the cost of strictly electronic components, whereas no substantial development has been made as regards wiring. On ships and, particularly, aircraft, an attempt has been made to overcome this problem by providing a single back-up wire for conveyed-wave or PCM (pulse code modulation) systems. Though they cater admirably on ships and aircraft, such systems are highly sophisticated and involve such high cost that large-scale application, e.g. for wiring automobiles or industrial vehicles, is out of the question. A system of the type defined in the preamble of claim 1 is disclosed in US-A-3 804 986, wherein each unit is connected in parallel to the transmission cable and has means for discriminating the time allotted thereto. This system is quite complex and thus expensive. US-A-3 518 628 describes a system including a central communication station and a plurality of remote units connected by a single time-shared communication cable and singularly addressed by the central station by a coded address signal. This system requires two lines for transmitting the reference signal for A/D conversion and for transmitting the reset signal. Thus this system is also bulky and complex. US-A-3 814 861 discloses a multiplex system including a central unit and a plurality of actuators sequentially enabled by a respective flip-flop operating as a counter. Here also many lines are required to transmit the signals from the central unit to the actuators. The aim of the present invention is to provide a system for interconnecting sensor and actuating devices, which system provides for a high degree of reliability, is fairly straightforward in terms of both design and actual wiring, is lightweight and reasonably cheap, allows a reduction of the signal conducting lines and provides for employing identical modules with no personalization required. With this aim in view, according to the present invention, there is provided a system for connecting sensor devices to actuating devices, as defined in claim 1 - comprises : A preferred arrangement of the present invention will now be described, purely by way of a non-limiting example, with reference to the accompanying drawings in which : Fig.1 shows a block diagram of a system in accordance with the present invention; Fig.2 shows a more detailed block diagram of two details in the Fig.1 diagram; Fig.s 3 and 4 show time graphs of a number of parameters detected in the Fig.2 block diagram; Fig.s 5, 6 and 7 show system arrangements equivalent to that described with reference to Fig.1. Number 10 in Fig.1 indicates a system for connecting sensor devices 11 to processing means 16 (described in more detail later on) controlling actuating devices 12. System 10 substantially comprises : a cable 13 having a given number of signal conducting lines (respectively numbered 1, 2, 3, 4 and 5 in Fig.2); a number of interface units, those located between sensor devices 11 and cable 13 being numbered 14, and those between actuating devices 12 and cable 13 being numbered 15; and the aforementioned processing means 16 designed, among other things and as shown more clearly in Fig.2, to circulate signals enabling given sensor 11 and actuating 12 devices to be connected to the said processing means 16. Note, in particular, the loop configuration of cable 13 which is interrupted solely by the insertion of processing means 16 conveniently in the form of a microprocessor unit. Fig.2 shows structural examples of interface units 14 and 15. In more detail, unit 14 substantially comprises a flip-flop 21, a comparator 22 and a diode 23. In more detail, flip-flop 21 (D type) presents an input and output series-connected over line 3, which is accordingly interrupted, and a clock input connected to line 2. The output of flip-flop 21 is also connected to an enabling input on comparator 22 which presents a non-inverting input (+) connected to a terminal on sensor device 11, and an inverting input (-) connected to the said line 2. The other terminal on sensor device 11 is grounded, whereas the output of comparator 22 is connected, via diode 23, to line 4. Unit 14 is supplied by lines 1 and 5 which, in this specific case, are located at the opposite ends of cable 13. Interface unit 15 substantially comprises a pair of flip-flops 25 and 26 (respectively, of the D and the T type type) and a two-input AND logic gate 27. In more detail, flip-flop 25 presents an input and output series-connected over line 3, the said output also being connected to a first input of gate 27. Line 2 is connected to both a clock input of flip-flop 25, and a second input of gate 27 the output of which is connected to the clock input of flip-flop 26. The said flip-flop 26 also presents an input connected to line 4, and an output connected to actuating device 12. In the example shown, actuating device 12 has an output controlling the lighting of lamp 28 or the supply of motor 29. Fig.s 3 and 4 show time graphs of a few of the parameters shown in Fig.2. Fig.s 5, 6 and 7 show respective systems 50, 60 and 70, which are equivalent in all respects to system 10 in Fig.1 and which employ the same numbering system for sensor and actuating devices 11 and 12, connecting cable 13, interface units 14 and 15, and processing units 16. The only difference between system 10 and system 50 in Fig.5 substantially consists in system 50 being a twin-loop configuration employing an auxiliary cable 13a connected to cable 13 at auxiliary processing means 16a also conveniently in the form of microprocessor logic units. As an equivalent solution, system 60 in Fig.6 presents an open cable 13 branching off from one side of processing unit 16. As a further equivalent solution, system 70 in Fig.7 presents a pair of cables, 13b and 13c, branching off separately from processing unit 16 and therefore conveniently controlled independently by the same. Operation of the system in accordance with the present invention will first be described with reference to Fig.s 1 to 4. Having determined which sensor devices 11 and actuating devices 12 are to be interconnected, the cable is arranged as shown in Fig.1, each sensor device 11 and actuating device 12 being assigned a respective interface unit 14 or 15. Examples of sensor devices could be : level or temperature sensors, or even a switch; of actuating devices: an indicator light, headlight, motor, etc. In strictly general terms, operation of system 10 consists substantially in picking up, cyclically and at the appropriate time, data produced by each sensor device 11, in transferring the said data to processing means 16, and supplying orders, at the appropriate time, to actuating devices 12. Such operation will be more readily understandable by examining the typical behaviour of two interface units 14 and 15 as shown in Fig.2. The said unit is supplied by cable 13, in particular, by lines 1 and 5 which, in the case of a flat cable 13, ore conveniently located at respective opposite ends of the cable, in such a manner as to safe-guard lines 2, 3 and 4 from outside interference. Line 2 is constantly supplied with a substantially saw-tooth signal v₂ (Fig.s 3a and 4a) presenting a rising edge, followed by a vertical falling edge back to zero, in turn, followed by a zero volt interval of a given time length, then another rising edge. Signal v₂ performs two functions : after being appropriately divided, as described later on, the rising portion is compared with the signal generated by sensor device 11, whereas the falling edge is used as a clock signal for updating the data in flip-flop 21 as regards unit 14, or in flip-flops 25 and 26 as regards unit 15. Signal v₃ (Fig.s 3b and 3c, 4b and 4c) may substantially be logic "1" or logic "0" in value, and is generated by processing unit 16. At each falling edge of signal v₂, signal v₃ is memorised on only one of the flip-flops on all the units connected to cable 13, the said flip-flops thus constituting a known type of loop counter. In other words, signal v₃ on line 3 constitutes an enabling signal for enabling operation of a specific interface unit 14 or 15, when signal v₃ presents a logic level "1" at the output of respective flip-flop 21 or 25. This permits units 14 to be interrogated one at a time for picking up the data generated by corresponding sensor device 11, or, similarly, it permits equally selective enabling of units 15 for transmitting any control signals to corresponding actuating devices 12. Line 4 of cable 13 is therefore supplied with a signal which depends on the data detected by sensor device 11 (Fig. 3c), or which is designed to control actuating device 12 (Fig.s 4e and 4f). The behaviour of units 14 and 15 will now be examined in more detail. Interface unit 14 must provide substantially for converting the voltage signal received from sensor device 11 into a corresponding pulse length v D , which pulse is then sent onto line 4 via diode 23. Such conversion of a voltage signal into a corresponding signal having a length proportional to the voltage value is achieved by means of comparator 22, which compares the voltage signal v C at its own non-inverting input (+) with the rising edge picked up from line 2 of cable 13 and present at its inverting input (-), (Fig.s 3b and 3c). The output of comparator 22 therefore presents a pulse signal v D the length of which is proportional to the voltage value (V₀) detected by sensor device 11. This operation is only performed when comparator 22 is enabled, i.e. when the enabling input of comparator 22 presents a logic "1" signal picked up at output v B of flip-flop 21, which, as already mentioned, occurs only once within each scanning cycle of the loop formed by cable 13. Interface 15 also performs a memory function via flip-flop 26, in that, the actuating function, e.g. lighting lamp 28 or supplying motor 29, cannot be performed solely over the brief period of time for which it is cyclically enabled. In this case too, the said unit is enabled via flip-flop 25 which, as already mentioned, constitutes a station on the said loop counter. Signal v H controlling actuating device 12 may be logic "1" or "0". Switching from one logic level to the other, accompanied by a corresponding switch in the control of actuating device 12, e.g. lamp 28 on or off, occurs at the falling edge of clock signal V G and depends on the corresponding value, at that moment, of signal v₄. That is to say, if signal v₄ is at logic level "0" (Fig. 4e), the output of flip-flop 26 does not switch and the corresponding signal v H retains its former level. If, on the other hand, signal v₄ is at logic level "1" (Fig. 4f), at the falling edge of signal v G , the output of flip-flop 26 switches, and the corresponding signal V H switches from logic level "1" to "0" (dash line) or from logic level "0" to "1" (dot-and-dash line). As processing unit 16 obviously provides for an extremely fast control cycle of all interface units 14 and 15, e.g. in the space of a few tens of milliseconds, the signal detected by a sensor device 11 may be assumed to be transmitted more or less instantaneously to the corresponding actuating device 12. To prevent a number of interface units from being enabled simultaneously, processing unit 16 could, at the end of each enabling cycle, conveniently circulate a logic "0" signal over the said loop counter, in such a manner as to cancel any falsely-enabled flip-flops on each unit 14 or 15. One of the most significant equivalent arrangements of the present system is the one shown in Fig.s. In this case, instead of being a single-loop configuration, system 50 presents two loops with a single contact point. Processing unit 16a, located at the said contact point, provides for transferring data from main cable 13 to auxiliary cable 13a. In like manner, each time the loop counter signal on line 3 reaches processing unit 16a, enabling of the interface units connected to loop 13a is moved forward one step. Such a configuration may be particularly useful in cases where updating of the data detected by sensor devices 11, or control of actuating devices 12 connected to cable 13a, may be performed at a slower rate as compared with the checking rate adopted for the corresponding devices connected to cable 13. Another possible equivalent solution is system 60 as shown in Fig.6. In this case, having an open cable 13, flip-flop enabling signal v₃ must be generated by unit 16 at the end of each control cycle. System 70 in Fig.7 may be considered both as an equivalent solution to that of Fig.6 with the addition of a further open branch, and as an emergency operating situation on system 10 in Fig.1. In fact, should cable 13 in Fig.1 be inadvertently cut, the resulting configuration would be identical to that of Fig.7, in which case, providing unit 16 is suitably designed, sensor devices 11 and actuating devices 12 may be kept equally under control, providing the possibility exists of circulating in reverse (e.g. on another cable 13 line) the data enabling the flip-flops on interface units 14 and 15. The advantages of the systems in accordance with the present invention will be clear from the foregoing description. In particular, the possibility of employing a single cable for connecting all the sensor and actuating devices drastically simplifies the wiring, while at the same time drastically reducing cost with no impairment in reliability. Furthermore, should it be possible to use the ground wire as a return wire, four-line cables may be employed in place of the five-line onces described. The addition of a new sensor and/or actuating device would not seriously complicate the system, except for updating processing unit 16 which must be informed as to how the new signals associated with the additional sensor and/or actuating devices are to be handled. Reliability could also be further improved by employing only high-level signals, or cables with optical-fibre lines. A type of system in accordance with the present invention obviously provides for low-cost manufacture and, consequent ly, large-scale application, for example, on automobiles or industrial vehicles. To those skilled in the art it will be clear that changes may be made to systems 10, 50, 60, 70 as described herein without, however, departing from the scope of the present invention. One particular system configuration equivalent to those described herein could be the type required for interconnecting a switch panel, an indicator light panel and a series of open/closed actuating devices and open/closed sensor devices. This is a typical case of a standard electrical panel for which a system may be devised whereby a processing unit such as 16 in the foregoing description may be dispensed with. The said unit, in fact, may be limited to no more than a stable oscillator for generating pulses for updating the data exchanged with the interface units. A typical configuration could be as shown in Fig.5, with unit 16 removed and unit 16a replaced by the said oscillator. In which case, all the sensor and/or actuating devices on the system would be connected, in due order, to cable 13, whereas cable 13a would be connected with all the indicator lights to be contacted by the said sensor devices, and with the switches to be contacted by the said actuating devices. Furthermore, an enabling signal must be circulated synchronously over both cable 13 and cable 13a, in such a manner as to cyclically connect the units on cable 13 to the corresponding units on cable 13a. Finally, the time interval between the end and start of saw-tooth signal v₂ may be employed for sending given check signals onto the line, particularly for checking the actuator. The solution proposed in accordance with the present invention is also valid and competitive when integrated in one CHIP. In which case, a few of the aforementioned safety provisions may be avoided, and reliable grid, star or mixed macrocircuit structures may be formed easily and cheaply.

Claims: A system for connecting sensor devices (11) to actuating devices (12), comprising: at least one cable (13) having a given number of signal conducting lines (1-5); a number of interface units (14, 15), each designed for assembly between the lines on said cable (13) and a respective sensor (11) or actuating device (12) and comprising flip-flop circuits, said interface units (14) which are interposed between said cable (13) and said sensors (11) comprising converting means (22) receiving an analog signal (v₀) from the respective sensor and a reference signal (v₂) from said cable; and processing means (16) for transmitting, on a first (2) and second (3) line on said cable (13), signals (v₂, v₃) cyclically determining connection of each said sensor (11) or actuating (12) device to a third line (4) on said cable (13) by means of the respective interface unit (14, 15) for respectively supplying to said third line (4) a signal (v₄) depending on a parameter detected by said sensor device (11) or for enabling said actuating device (12) to receive a control signal (v₄) generated by said sensor device (11) or by said processing means (16), characterized in that said signals (v₂, v₃) determining connection of said devices (11, 12) are circulated onto said cable (13), and in that said processing means (16) generates a sawtooth signal (v₂) including a ramp portion defining said reference signal and a falling edge for triggering said flipflop circuits (21, 25). A system according to claim 1, characterized in that each said interface unit (14, 15) comprises a flip-flop circuit (21, 25), said flip-flops of said interface units being series-connected to each other and defining counters. A system according to claim 2, characterized in in that each said flip-flop circuit comprises a D-type flip-flop (21, 25). A system according to claim 2 or 3, characterized in that said converting means comprises a comparator (22) for generating a signal the length of which depends on the voltage of said analog signal (v₀), said comparator (22) being enabled by a signal generated by the flip-flop circuit (21) defining the counter. A system according to any of the preceding claims, characterized in that the interface unit (15) interposed between said cable (13) and a respective actuating device (12) comprise memory means (26) connected to said cable to receive an actuating signal (v₄) and to the respective flip-flop circuit (15) to receive an enabling signal (v G ), the memory means output being directly connected to the respective actuating device (12). A system according to claim 5, characterized in that said memory means comprises a T-type flip-flop (26). A system according to any of the preceding claims, characterized in that said cable (13) extends substantially in a loop beginning and ending at said processing means. A system according to any of the preceding claims, characterized by a number of cables, each closed substantially in a loop about at least a respective processing unit, so as to define a single network the connecting points whereof conveniently consist of processing units (16a). A system according to any of the preceding claims, characterized in that the lines (1-5) constituting said cable (13) are made of optical fiber. A system according to any of the preceding claims, characterized in that said processing means (16) comprises at least a microprocessor unit.

Inventors: PALAZZETTI, MARIO
Applicants: FIAT AUTO S.P.A.
Application year: 1986
Main classification: G08C15
IPC codes: B60R16, G08C15