Smart control strategy for regulating a temperature controller

Details Smart control strategy for regulating a temperature controller Smart control strategy for regulating a temperature controller

1999-07-26

2003-02-18

Picard, Leo (Department: 2125)

Data processing: generic control systems or specific application

Specific application, apparatus or process

Mechanical control system

C700S276000, C700S300000

Reexamination Certificate

active

06522954

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a smart control strategy for regulating a temperature controller for supplying or exhausting heat to/from a room, object or fluid.
BACKGROUND OF THE INVENTION
No such smart regulating control strategy was known hitherto. What is known are self-optimizing control systems for regulating room heating, requiring, however, the user to first input a wealth of information as to nature of the heating, the supply flow temperature, the heat losses for various indoor and outdoor temperatures, and so on. It is especially in the case of systems very slow to react, such as those used as a rule in domestic heating systems, as well as in initiating changed setpoint temperatures, that these self-optimizing closed-circuit controllers are unable to prevent a relatively strong overshoot or undershoot of the setpoint temperature. Aside from this, presetting the control parameters is often a highly complicated business in some cases and necessitates much trial and error before arriving at a satisfactory result in functioning.
Also known, of course, are thermostats for regulating living room heating radiators which signal the heating ON/OFF, e.g., via a valve or a circulating pump as soon as a critical setpoint temperature is violated. The ON/OFF hysteresis is usually of the order of 0.5 to 1° C., even as much as 2° C. in the case of unsophisticated radiator thermostat valves. It is this ON/OFF response of such thermostat regulators that results in room temperature fluctuating seriously, due to the heating system not being able to instantly react to the control signals of the regulator, but only after a considerable delay. Should the thermostat signal the heating OFF, for example, the radiators which are still hot at this time will continue to radiate heat to the surrounding room for quite a few minutes, thus resulting in room temperature significantly increasing above the setpoint temperature. In the reverse situation, when the regulator signals the heating back ON, it will take quite some time until the radiators again become hot, and during this time room temperature drops even further below the setpoint temperature.
This overshoot/undershoot nuisance is aggravated furthermore by the relatively wide hysteresis of thermostatic regulators inherent in their design.
SUMMARY OF THE INVENTION
It is on the basis of that said above that the object of the invention is to define a smart control strategy having no need of prior information as to the nature of the heating or cooling required, as to the ambient conditions, especially as regards the temperature losses between the room, object or fluid to be heated and the colder surroundings or, respectively, as regards the heat transfer from the higher temperature surroundings to the room, object or fluid to be cooled, and which not only assures the setpoint temperature desired by the user being maintained very accurately, but also permits speedy achievement of this setpoint temperature with no serious overshoot/ undershoot thereof. In addition to this, the strategy is also intended for use with or facilitated retrofitting to existing heating or cooling systems.
This object is achieved, for one thing, by a smart control strategy for regulating a temperature controller for supplying or exhausting heat to/from a room, object or fluid in which a maximum temperature setpoint (setpoint-MAX) and a minimum temperature setpoint (setpoint-MIN) is specified and the time profile of the actual temperature of the room, object or fluid is regularly measured, comprising the following steps:
defining an nth ON point in time (t-ON(n)) at which the temperature controller is to be signaled ON,
defining an nth OFF point in time (t-OFF(n)) at which the temperature controller is to be signaled OFF,
sensing the two nth extreme values (actual-MAX(n) and actual-MIN(n)) resulting after ON of the temperature controller in the actual temperature profile in which the actual temperature has a local minimum and a local maximum,
determining the 1st derivation of the time profile with time in the nth ON point in time (t-ON(n)),
determining the optimum nth ON/OFF points in time (t-optON(n) and t-optOFF(n)) from the values of the nth OFF point in time (t-OFF(n)) and the nth ON point in time (tON(n)), the two nth extreme values (actual-MAX(n) and actual-MIN(n)) in the temperature profile and the 1st derivation of the temperature profile with time in the nth ON point in time (t-ON(n)) at which for the nth extreme value (actual-MAX(n)) a local maximum in the temperature profile equaling the specified maximum temperature setpoint (setpoint-MAX(n)) and for the nth extreme value (actual-MIN(n)) a local minimum in the temperature profile equaling the specified minimum temperature setpoint (setpoint-MIN(n)) is attained,
incrementing n by 1 and repeating the steps a) to f) taking into account the determined nth ON/OFF points in time (t-optON(n) and t-optOFF(n)) as well as the 1st derivation of the temperature profile with time in the nth ON point in time (t-ON(n)) in establishing the n+1 ON/OFF points in time (t-ON(n+1) and t-OFF(n+1)).
The gist of the invention is thus based on the fact that the temperature of any room, object or fluid to be heated or cooled will always dither about the actually desired setpoint due to the inertia of the heating or cooling system and due to ambient losses. Whilst in the case of simple thermostats only one setpoint is specified which when exceeded results in the heating being signaled OFF and when no longer attained results in the heating being signaled ON, in the control strategy in accordance with the invention two setpoints are specified. These two setpoints mark the maximum swing of the dither about the temperature value as lastly desired, thereby automatically sensing the reaction of the room, object or fluid to a heating or cooling action and taking it into account when the heating or cooling system is next signaled ON. The strategy thus learns the parameters needed for optimum regulation of the corresponding temperature controller without the user having to specify them beforehand. Should the strategy “see” for instance that a radiator is still giving off relatively too much heat to the room to be heated after the OFF signal has been given, resulting in the actual temperature exceeding the specified maximum setpoint temperature, then the radiator is signaled off correspondingly earlier in the next heating cycle.
One major advantage afforded by the strategy is that it may be put to use for all kinds of temperature control applications, such as e.g. oil, gas, electric heating, hot air fans, heating coils, heating or cooling elements on heating agent/coolant flow, especially cooling elements in refrigerators, cold rooms and air-conditioning facilities, etc. It is also irrelevant for the strategy whether heat needs to be supplied to or exhausted from a room or object, i.e. the strategy can be put to use in the temperature control of houses, industrial buildings, rooms, tents, vehicle interiors, baking ovens, refrigerator rooms, cold stores, refrigerator trailer vehicles, trains and the like since it automatically establishes the ambient parameters needed for optimum regulation.
In one particularly simple embodiment of the control strategy with no change in the setpoints, setpoint-MAX/MIN, the ON point in time t-ON(n+1) (relative to the temperature profile) is set=t-optON(n) and/or the OFF point in time t-OFF(n+1) (again relative to the temperature profile) is set=t-optOFF(n). It is, of course, clear that instead of the relative ON point in time the strategy will work just as well with the absolute ON point in time. In such a case, of course, a constant time factor needs to be added to the values t-optON(n) and t-optOFF(n). In other words, the strategy may be implemented either so that relative optimum ON/OFF points in time are established for the temperature controller, it being good practice to determine the ON point in time of the temperature controller relative to the actual t

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