Error detection/correction and fault detection/recovery – Pulse or data error handling – Error/fault detection technique
Reexamination Certificate
2000-05-03
2004-03-23
Baker, Stephen M. (Department: 2133)
Error detection/correction and fault detection/recovery
Pulse or data error handling
Error/fault detection technique
C700S021000
Reexamination Certificate
active
06711713
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for detection, transmission and processing of safety-related signals having at least one detector, one transmission path and at least one signal processor.
BACKGROUND INFORMATION
In order to control machines in manufacturing systems in industry, in particular machine tools and robots, signals are transmitted from controllers or peripherals to a control unit. In this case, the controllers and peripherals may be either stationary or mobile units. In particular, safety-relevant signals such as EMERGENCY-OFF, EMERGENCY-STOP, START, STOP, confirmation signals, movement buttons and safety-related input signals regularly have to be reliably detected, transmitted and processed in order to ensure the safety of the operator, of the machines and of the systems. Signals which initiate movements, for example shaft movement, gripper pick-up and the like, are also related to this problem.
Conventionally, safety-related signals are therefore generally transmitted by wire. EMERGENCY-OFF, confirmation and safety-relevant input signals are detected via duplicated electromechanical switching elements. Movement buttons, START and STOP, on the other hand, are detected via simple electromechanical, electrical or electronic switching elements.
For transmission, the signals are conventionally transmitted via a bus system, a serial link or a parallel link, or else directly via wires.
EMERGENCY-OFF signals are passed via two pairs of wires to safety tripping units. On the other hand, depending on the mode, START, STOP and movement buttons are subject to different safety requirements. START, STOP and movement button signals are generally transmitted via the bus system, the serial link or the parallel link. If these signals have an associated safety function, then the signals are effective only in conjunction with confirmation buttons, which are routed to the tripping unit via wires. Such so-called confirmation buttons must in this case be operated at the same time as the movement buttons. Safety-relevant inputs are carried via their own wires.
Conventionally, the transmission itself takes place via a cable which, apart from the necessary signal lines, normally also includes supply lines for current and/or voltage for the control unit. The cable must be suitable for industrial operational conditions, which means that electrical interference, mechanical loads and chemical influences have to be considered.
Signals such as EMERGENCY-OFF and confirmation signals are electrically processed in two channels. On the other hand, START, STOP and movement buttons are processed in one channel, taking account of a confirmation signal.
The wire-based link between the control unit and the controllers or peripherals has the disadvantages, in particular, of the costs of a wire-based link, the installation complexity associated with this, as well as poorer mobility, maintenance effort for the cable, the risk of accidents linked to this, and the necessity for the already described confirmation button.
SUMMARY
An object of the present invention is to provide a method and an apparatus for detection, transmission and processing of safety-related signals, in which the disadvantages mentioned above can be avoided.
The term safety-related signals in this case means signals in which faults or errors in the detection, transmission and evaluation can lead to loss of safety functions in the machine, system or process.
According to the present invention, this object is achieved by a method for detection, transmission and processing of safety-related signals having at least one detection means, one transmission path and at least one signal processing means, in that
safety-relevant signals are physically detected on at least two channels at the transmitter end,
the detected data are logically transmitted by at least two channels using a safety technique by radio to a receiver end, and
the received data are likewise physically processed and monitored on at least two channels at the receiver end.
A corresponding apparatus for achieving the above object according to the present invention is characterized in that
the detection means for safety-related signals are designed physically with at least two channels at a transmitter end,
a radio path which logically has at least two channels and uses a safe technology is provided with in each case one radio module at the transmitter end and receiver end, and
the signal processing means at the receiver end are likewise designed physically with at least two channels.
The present invention thus allows radio transmission of signals for controlling machines, appliances and processes, including safety-relevant signals such as EMERGENCY-OFF, EMERGENCY-STOP, START, STOP, confirmation signals, movement buttons and safety-related input signals as well as signals which initiate movement. Safe evaluation of the signals by software can also be achieved. The present invention furthermore ensures that an individual fault or error in the detection, transmission and evaluation does not lead to any loss of safety functions.
According to a first example refinement, the safety-related signals are detected by redundant signals being produced, for example by means of duplicated electromechanical, electrical or electronic input elements. Various redundant signals are detected in two channels by means of two detection modules, and this can be achieved either by hardware, or by hardware and software. The detected signals provide protection data for signal transmission from each detection module, allowing monitoring for
incorrect transmitters or incorrect receivers,
adulteration of the data,
loss of data and
repetition of data.
In this case, each detection means uses the signal data to produce additional protection data for monitoring purposes.
According to a further example refinement of the present invention, the transmission is carried out using a transmission module, in each case one transmission and reception module, and one receiver module. The transmission and reception modules as well as the radio modules are each formed from different components. The radio transmission takes place using digital technology. Major parts of the signal processing for the transmission can be implemented in software. The transmission module receives the signal data, and the associated protection data, from both detection modules, cyclically. The data in both channels are then transmitted jointly, by radio. The received data in the two channels are separated again by the receiver module. In order to process the data and to carry out the monitoring function, the data are then passed on to the respective evaluation and monitoring module for channel
1
and channel
2
.
According to a further example refinement of the present invention, the signals are likewise monitored and processed in two channels, in particular on two separate processors, such as signal processors. The data are monitored in each channel on the basis of the following criteria:
incorrect sender or incorrect receiver,
adulteration of the data during transmission,
loss of data,
repetition of data and
interruption of the data.
A time criterion is monitored in each channel, as a consequence of which safety-relevant functions are, as a rule, initiated after a predetermined time period after detection of the signals. This is ensured according to the present invention by the signals always being transmitted after a predetermined time period for processing.
The serviceability of an EMERGENCY-OFF and STOP input element as well as the associated operation of the respective detection module are monitored in each channel by positive dynamic activation means.
After evaluation, faults and errors in each channel are detected by comparison of the evaluation results.
The reactions to be initiated after detection of a fault or error depend on various factors, such as the respective application, the respective safety policy, the respective machine, controller or system.
Furthermore, any protection methods can
Kahle-Nobis Gerhard
Meier Christof
Rumpler Gerhard
Baker Stephen M.
Siemens Aktiengesellschaft
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