Electronic controller for cyclically operating machinery

Details Electronic controller for cyclically operating machinery Electronic controller for cyclically operating machinery

1983-10-11

1986-12-23

Smith, Jerry

Excavating

371 68, 364133, 364184, G06F 1100, G06F 734, G05B 1508, G05B 902

Patent

active

046317228

DESCRIPTION:

BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national phase application corresponding to PCT/EP83/00030 filed Feb. 4, 1983 and based, in turn, upon a German national application No. P 32 04 709.6 filed Feb. 11, 1982.


FIELD OF THE INVENTION

The invention relates to an electronic controller with safety facilities for a device with mechanical sequences with two differently designed safety channels, of which the first safety channel is constructed with hard-wired switching logic and the second according to microcomputer technology, and with a common safety stage which upon the occurrence of unequal output signals of the two safety channels places the device in a safe state, as well as with a self-check facility for the second safety channel.


BACKGROUND OF THE INVENTION

Especially high safety-technological demands must be made on controllers where control malfunctions can cause injury to persons. For the enhancement of the safety of electronically controlled production machines numerous possibilities are known (Dipl. Ing. W. Wienandts "Sicherheitstechnische Anforderungen und electronische Steuerungen" published in "Die BG", March 1980, pp. 220-224). FIG. 2 of the cited reference shows a press controller with two identically constructed control channels whose individual stages are monitored by a safety channel by means of comparison. The safety channel in turn contains a self-check feature. In a system of this type, system errors are possible, e.g. design errors, which are not recognized. It does thereby not offer the necessary safety.
FIG. 6 of the cited publication shows the systemic structure of an electronic controller for a moving staircase. It has one control channel and two safety channels, one of which is constructed with hard-wired switching logic and the other with microcomputer technology. Owing to different technologies utilized in processing the signals, the probability of systematic errors affecting the two control channels simultaneously and in the same manner is considerably reduced. Nevertheless, the probability of simultaneously occurring malfunctions in the first and second safety channels is unacceptably high, since on account of the great number of integrated components in the safety channels with microcomputer technology there exists a high probability of malfunction for this channel. Self-check facilities in this safety channel can reduce the effects of frequent errors. A self-check with a high rate of malfunction recognition, however, requires a time which, depending on circumstances, can last several seconds. This monitoring time may undesirably prolong the cycle time in devices operating cyclically and with periodic monitoring of this device and may thus decrease the availability and utilization of the device.


OBJECT OF THE INVENTION

The invention has the object of providing an electronic controller with safety facilities for cyclically operating devices, which affects the cycle time either not at all or only negligibly, and yields a high degree of safety.


SUMMARY OF THE INVENTION

This object is realized according to the invention by providing cyclically operating devices such that
(a) the safety channels simultaneously have identical control functions and act upon respectively associated operating members,
(b) the self-check facility effects the monitoring of the entire second safety channel by means of a monitoring program via a microcomputer and a control circuit,
(c) the first safety channel also has its own self-check facility,
(d) the self-checks occur periodically within the cycle periods,
(e) amplifiers are connected to the outputs of the safety channels whose output signals are monitored by a comparator for equality and synchronism,
(f) the output signal of the comparator and the output signals of the self-check facilities act upon a common safety stage.
Inasmuch as the safety channels simultaneously have identical safety functions and act upon respectively operating members, a redundant diversified system is realized with simple means and few comp

REFERENCES:
patent: 3686493 (1972-08-01), Schmid
patent: 4198678 (1980-04-01), Maatje et al.
patent: 4200226 (1980-04-01), Piras
patent: 4233682 (1980-11-01), Liebergot et al.
patent: 4350225 (1982-09-01), Sakata et al.
patent: 4358823 (1982-11-01), McDonald et al.
patent: 4400792 (1983-08-01), Strelow
"Sicherheitstechnishe Anforderungen an eleletronische Steuerungen", published in Mar. 1980, in Arbeitssichercheit.

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