Simple adaptive control method
Publication Date: 2011-May-24
The IP.com Prior Art Database
A simple control system, for example for temperature control, using a counter which is incremented or decremented when the temperature crosses certain thresholds.
Simple adaptive control method
This technique is applicable to many situations where a measurement is made and is used to adjust the rate at which a controlling influence is applied to a system, so that the measured quantity is kept within certain bounds. As an example, the temperature in an environmental chamber is measured and is used to control a heater and/or a chiller so as to keep the temperature close to the desired temperature. Another example is measuring the temperature within an enclosure and using it to control the fan speed so as to keep the temperature within acceptable limits.
The intensity of the influence is not infinitely variable, but can take on one of a number of discrete values.
The aim of the method is to minimise the use of the extreme values of the influence, and, after an initial settling down period, to keep the measurement within acceptable limits by only using a pair of adjacent influence values.
Description of the invention
The following description uses the scenario of varying the fan speed to control the temperature of an enclosure.
The temperature is divided into preferably four regions: too low, slightly low, slightly high and too high. The temperature is sensed and the outputs of three comparators are combined to indicate which region the temperature is in. The method adaptively adjusts the fan speed to keep the temperature in the slightly low and slightly high regions (collectively referred to as the comfort zone), as much as possible.
A counter, which can count up and down, is initialised to a suitable value such as one near the middle of its range. The counter will control the fan speed, making the speed higher for higher count values.
If the temperature lies in the comfort zone the fan is operated at the rate indicated by the value of the counter.
If the temperature lies in the too high region the fan is operated at its maximum rate, and if it lies in the too low region the fan is operated at its minimum rate, both of these being independent of the value in the counter.
Whenever the temperature rises from the slightly low to the slightly high region, or from the slightly high to the too high region, the counter is incremented, unless it is already at its maximum value, in which case it stays at its maximum value.
Whenever the temperature falls from the slightly high to the slightly low region, or from the slightly low to the too low region, the counter is decremented, unless it is already at its minimum value, in which case it stays at its minimum value.
This control method has these properties:
- Extreme fan speeds are only used outside the comfort zone.
- If the temperature moves outside the comfort zone the fan speed that will be used when the temperature gets back to the comfort zone is adjusted in the appropriate direction.
- Eventually a counter value will automatically be found which allows the temperature to stay in the comfort zone, the fan speed in the too high region bein...