Communications: electrical – Condition responsive indicating system – With particular system function
Patent
1997-10-21
2000-02-08
Pope, Daryl C.
Communications: electrical
Condition responsive indicating system
With particular system function
340501, 340514, G08B 2900
Patent
active
060232226
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATION
This application is a national phase of PCT/EP97/00748 filed Feb. 17, 1997 and based upon German National Application 196 06 776.6 filed Feb. 23, 1996 under the International Convention.
FIELD OF THE INVENTION
Our present invention relates to a method of monitoring a plurality of control loops and, in particular, to a method which is applicable to temperature measurement and the measurement of other parameters in textile machines which may have a large number of control loops.
BACKGROUND OF THE INVENTION
The reliability of control systems, in particularly of temperature control loops, essentially depends on the accurate performance of its individual components forming the control loop, such as the actual value sensor, the controller and the final control element. The performance may be monitored e.g. by a second measuring circuit consisting of a second measuring sensor which is connected to an independent monitoring device for the actual value of the controlled quantity. If a permitted limit of the control deviation is exceeded, an alarm routine is generated. Such redundant monitoring systems are commonly in use. However, they are associated with high cost, especially if there is a large number of similar control loops as is the case in controlling the temperature of textile machines like stretch winding machines or stretch twisting machines, where several hundred temperature control points with identical temperature setpoints are provided for each machine.
OBJECT OF THE INVENTION
It is the object of the present invention to provide an improved method of monitoring a plurality of control loops for the purposes described.
SUMMARY OF THE INVENTION
This object is attained, in accordance with the invention in that, during an initial phase, actual values of a controlled quantity of all of the control loops are controlled to a common setpoint and, after reaching a stationary operating condition, respective regulation ratios are measured and stored as are required in each control loop for achieving the common actual value. During a subsequent operating phase, the actual regulation ratio is compared with a stored value and an alarm signal is generated if a regulation ratio deviates from the stored value by more than a predetermined amount.
The invention avoids the high costs of a redundant system with two measuring sensors for each control circuit and nevertheless guarantees a reliable monitoring of the temperature or of another controlled quantity.
The invention monitors the control or regulation ratio of the controller at each controlled system, i.e. it controls the percentage ratio of the actual controller output quantity to the maximum controller output quantity or the permitted maximum controller output quantity, respectively: ##EQU1##
In the case of an electrical heater the controller output quantity is the heating power. A signal, which is proportional to the actual controller output quantity and therewith is proportional to the regulation ratio, already exists in the controller. It is the controller output quantity signal at the controller output. Instead of requiring a plurality of additional redundant actual value sensors for the controlled quantity (e.g. temperature), the invention utilizes the already available controller output signal for such monitoring by standardizing the signal to a common level by forming the regulation ratio for all control loops and by thereafter evaluating this regulation ratio signal.
This will be described with reference to the temperature control of a textile machine. However, the method is also useful for controlling in an analogous manner any other physical quantities.
The method is based on the fact that the heating power of a plurality of identical heating devices, like heated rolls or heated plates, must be identical if those heating devices are exposed to the same interference quantities and if the temperatures are identical. If one heating element deviates from its setpoint temperature, then its heating power will a
REFERENCES:
patent: 4707310 (1987-11-01), Debeaud
patent: 5392226 (1995-02-01), Hamilton
Brossmer Max
Gehrmann Wolfgang
Lehle Erhard
Straka Derrick
D.I.E.N.E.S. Apparatebau GmbH
Dubno Herbert
Pope Daryl C.
Zinser Textilmaschinen GmbH
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