METHOD FOR CORRECTING THE THERMAL INERTIA OF A TEMPERATURE CONTROL DEVICE

Abstract

A method (10) for correcting a thermal inertia of a temperature control device (200) comprising electronic circuitry adapted to implement the method (10). The method (10) comprises at least the following steps: characterizing (11) the temperature control device to determine a time constant specific to the temperature control device; acquiring (12) a measurement of a temperature; correcting (13) the measured temperature by modeling the temperature control device in the form of a first-order or higher low-pass filter using the specific time constant to obtain a corrected temperature; using (14) the corrected temperature in the temperature control device to control a temperature setpoint. Figure to be published with the abstract: Fig. 1

Description

Title of the invention: METHOD FOR CORRECTING A THERMAL INERTIA OF A TEMPERATURE CONTROL DEVICE Technical field

[0001] The invention relates to the field of temperature control. STATE OF PRIOR ART

[0002] In a known manner, temperature control devices such as thermostats and connected thermostats operate on the basis of a temperature setpoint associated with a regular measurement of the temperature of the room whose temperature is controlled.

[0003] Very schematically, the temperature control devices make it possible to maintain an ambient temperature substantially equal to a set temperature.

[0004] To measure the ambient temperature, the control devices integrate one (or more) temperature probes. However, it is known that temperature control devices have a thermal inertia which is notably due to the electronic architecture of the temperature control device and to the nature of the housing of the temperature control device. It is specified that by thermal inertia, it is meant a delay between the existence of a temperature step in the room and the measurement of this temperature step by the control device. It is recalled that a temperature step is a sudden variation in temperature (typically in the context of temperature control in a room, it may be the opening of a window).As is known, the nature of the material constituting the case and the heat released by the electronic card slow down the measurement of a temperature step by the probe integrated into the temperature control device.

[0005] Currently, to overcome the inertia of the temperature control device, it is known to optimize the routing of the electronic card of the temperature control device, avoiding ground planes around the temperature probe. Another known solution consists of placing the temperature probe on an edge of the electronic card, close to the outside of the temperature control device, to limit the thermal inertia of the structures surrounding the temperature probe. It is also known to integrate a “set point” type thermal regulation into the control device. These solutions are not entirely satisfactory because they require modifying the architecture of the temperature control devices (which is expensive), while not allowing the measurement delay to be exactly compensated. (ie the inertia) of the probe.

[0006] Thus, in this context, it is necessary to provide a method for correcting thermal inertia of a control device, which is inexpensive and which allows rapid correction of the inertia. Statement of the invention

[0007] For this purpose, according to a first aspect, a method is proposed for correcting a thermal inertia of a temperature control device comprising electronic circuitry adapted to implement the method. The method comprises at least the following steps: - characterize the temperature control device to determine a time constant specific to the temperature control device; - acquire a temperature measurement; - correct the measured temperature by modeling the temperature control device as a first-order or higher low-pass filter using the natural time constant to obtain a corrected temperature; - use the corrected temperature in the temperature control device to regulate a temperature setpoint.

[0008] Thus, the thermal inertia correction method allows for rapid inertia correction, with the inertia being modeled and the measured temperature being corrected based on the modeling. In addition, the proposed method is inexpensive.

[0009] According to a particular arrangement, the characterization step comprises: - apply a predetermined temperature step to the temperature control device; - measure the time taken by the temperature control device to detect a predetermined percentage of the temperature step; - determine the time constant from the measurement of the time taken by the control device to detect a predetermined percentage of the temperature step.

[0010] According to a particular arrangement, the predetermined percentage of the temperature step is between 50% and 100%, preferably between 60% and 65% and even more preferably between 62% and 64%.

[0011] According to a particular arrangement, the step of correcting the measured temperature by modeling the temperature control device in the form of a first-order or higher filter using the natural time constant to obtain a corrected temperature comprises: - Model the temperature control device as a first-order or higher low-pass filter using the time constant own ; - Determine an inverse response of the first-order or higher low-pass filter to estimate the corrected temperature.

[0012] According to a particular arrangement, the step of correcting the measured temperature by modeling the temperature control device in the form of a first-order filter using the natural time constant to obtain a corrected temperature further comprises filtering the inverse response to obtain the corrected temperature.

[0013] According to another aspect, there is provided a temperature control device comprising electronic circuitry adapted to implement the method according to the invention comprising at least the following steps: - characterize the temperature control device to determine a time constant specific to the temperature control device; - acquire a temperature measurement; - correct the measured temperature by modeling the temperature control device in the form of a first-order or higher low-pass filter using the natural time constant to obtain a corrected temperature; - use the corrected temperature in the temperature control device to control a temperature setpoint.

[0014] According to another aspect, there is provided a computer program product comprising program code instructions for executing the method according to the invention.

[0015] According to another aspect, there is provided a non-transitory storage medium on which is stored a computer program comprising program code instructions for executing the method according to the invention, when said instructions are read from said non-transitory storage medium and executed by a processor. Brief description of the drawings

[0016] The characteristics of the invention mentioned above, as well as others, will appear more clearly on reading the following description of at least one exemplary embodiment, said description being made in relation to the attached drawings, among which:

[0017] [Fig. 1] schematically illustrates a method for correcting thermal inertia of a temperature control device;

[0018] [Fig.2] illustrates a determination of a proper time constant;

[0019] [Fig.3] illustrates a correction of the measured temperature;

[0020] [Fig.4] schematically illustrates a computer system suitable for implementing the method.

[0021] DETAILED DESCRIPTION OF EMBODIMENTS

[0022] Method for correcting thermal inertia

[0023] With reference to [Fig. 1], according to a first aspect, a method 10 is proposed for correcting a thermal inertia of a temperature control device 200 which will be described below.

[0024] The method 10 comprises at least the following steps:

[0025] - characterize (step 11) the temperature control device to determine a time constant specific to the temperature control device;

[0026] - acquire (step 12) a measurement of a temperature;

[0027] - correct (step 13) the measured temperature by modeling the control device of temperature in the form of a first-order or higher filter using the natural time constant to obtain a corrected temperature;

[0028] - use (step 14) the corrected temperature in the temperature control device temperature to regulate a temperature setpoint.

[0029] Step 11 - Characterize

[0030] According to a particular arrangement, the characterization step comprises:

[0031] - apply (step 111) a predetermined temperature step to the device of temperature control;

[0032] - measure (step 112) the time taken by the control device to detect a predetermined percentage of the temperature step;

[0033] - determine (step 113) the time constant from the measurement of the time taken by the control device to detect a predetermined percentage of the temperature step.

[0034] According to a particular arrangement, the predetermined percentage of the temperature step is between 50% and 100%, preferably between 60% and 65% and even more preferably between 62% and 64%.

[0035] According to an even more particular provision, the predetermined percentage is 63.2%.

[0036] According to one embodiment, step 11 is carried out by placing the temperature control device 200 in an oven at a predetermined temperature. According to the example presented in [Fig. 2], the temperature control device 200 is positioned in an oven at 26°C. When the measured temperature is stable and corresponds to the ambient temperature of the oven (i.e. when the temperature measured by the temperature control device 200 is stable at 26°C), the device 200 is then removed from the oven and placed on a table at ambient room temperature (21°C in the embodiment in [Fig. 2]). This manipulation makes it possible to see the evolution of the temperature measurement by the temperature control device 200 for an instantaneous temperature difference of 5°C. The results of temperature measurement by the temperature control device 200 are obtained via a serial link between the temperature control device 200 and a terminal on a computer for recording data. The temperature control device 200 transmits a measurement every 5s. With reference to [Fig.2], curve I represents a temperature step of 5°C experienced by the temperature control device 200 (i.e. this curve is not a measurement). Curve II represents the temperature measured by the temperature control device. Assuming that this is a first-order system (i.e. a first-order low-pass filter), it is possible to determine the time constant of the first-order system by measuring the time taken by the temperature control device 200 to measure 63.2% of the step. In this case, the start of the step begins at 1015s at 26.2°C. 100% of the step corresponds to 21.3°C so 63.2% of the step corresponds to 23.1°C.the temperature control device 200 measures 23.1°C at 1410s of the test, this therefore makes a difference of 395s with the start of the step.

[0037] It is specified that in the embodiment presented in the remainder of the description, the device is modeled in the form of a first-order low-pass filter. Nevertheless, it is entirely possible to use a filter of a higher order.

[0038] Step 12 - Acquire

[0039] Step 12 of acquiring a temperature measurement is carried out by one (or more) temperature probes of the temperature control device.

[0040] Step 13 - Correct

[0041] Step 13 of correcting the measured temperature by modeling the temperature control device in the form of a first-order filter using the natural time constant to obtain a corrected temperature comprises:

[0042] - Model (step 131) the temperature control device in the form of a first-order low-pass filter using the natural time constant;

[0043] - Determine (step 132) an inverse response of the first order low-pass filter to estimate the corrected temperature.

[0044] More precisely, according to the embodiment presented here, the modeling step 131 is carried out by considering the evolution of the temperature as a first-order system (filter), which therefore presents the following transfer functions: - For a continuous time = e~ - For a sampled system: ,,

[0045] where r is the time constant and Te the sampling period.

[0046] The Z transform (i.e. the discrete equivalent of a Laplace transform) of this transfer function is: [°°471 / / (2)=0^=^(7)^00+7 + (7)^+-..

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[0067] The Z transform is therefore a geometric sequence with reason A hence the transfer function of the system TJ ( y \ _ Z _ 1 _ 1 “ ZA “ “ i.AZ On the other hand, the transfer function corresponds to the ratio between the Z transform of the output signal and that of the input signal. y(n) = h(n)*u(n) Y(Z) =H(Z).U(Z) H (Z} = ■— = ■— To have a unit gain on the function it is necessary to add the multiplier coefficient ' nz> a 1- / ^1 It is possible to deduce the product response by developing: Y(Z) - Y(Z). bZA=U(Z)zi Y (Z) — aU (Z} + bY(Z)Z7l Finally, the recurrent equation of the low-pass filter is obtained by replacing X(Z) by x(n) and X(Z).Z 1 by x(nl). Let the recurrent equation of the first-order infinite impulse response filter be: y(n) -au(n) + by(n-1). To be able to apply this equation, it is necessary to calculate the coefficients a and b as below, taking the sampling used for the measurement and the measured time constant. The coefficients a and b are determined as follows: a=lb and b — So, for example, with Te=5s on ar=395s, a=0.0126 and b=0.9874. Thus, the application of the infinite impulse response filter equation to the temperature step makes it possible to obtain the evolution of the filtered temperature according to the step response of the temperature control device. In other words, as shown in [Fig. 3], step 131 makes it possible to model the behavior of the temperature control device and therefore, more precisely, to model the inertia of the temperature control device. Indeed, curve 2 corresponding to the modeling of step 131 corresponds substantially to curve 1 of the temperature measured by the control device. Following modeling step 131, as previously indicated, step 13 includes a step 132 of determining an inverse response of the first-order low-pass filter to estimate the corrected temperature. The objective of this step 132 is to apply a software calculation to the measurement in using the filter equation to obtain a corrected temperature closest to the actual temperature.

[0068] Starting from the recurring equation which allows the filtered temperature to be calculated:

[0069] y(n) = a jc ( n ) + by(n-1)

[0070] the inverse equation corresponding to the correction on the filtered measurement y(n) and y(nl) is obtained in order to find the real temperature x(n): [0071 ] _ >90 -

[0072] According to the example of [Fig.3], step 132 is carried out over a period of 60 seconds, which corresponds to 12 measurements every 5 seconds with the temperature control device used. For comparison, step 132 is also carried out over a period of 20 seconds, which corresponds to 4 measurements every 5 seconds.

[0073] Thus, as shown in [Fig. 3], step 132 makes it possible to obtain a corrected temperature that approaches a real temperature more quickly. Thus, with reference to [Fig. 3], curve 4 and curve 5 which represent the corrected temperature at the end of step 132 are close to the temperature step. In other words, step 132 makes it possible to catch up with the measurement inertia of the temperature control device, to determine a corrected temperature closer to the real temperature. Thus, according to the example presented here, the time required to reach 63% of the temperature step is 75 seconds at the end of step 132 whereas it is 395 seconds without making corrections (i.e. the inertia of the temperature control device is such that the temperature control device takes 395 seconds to measure the temperature step). Furthermore, as shown in [Fig.3], increasing the number of measurements to perform step 132 makes it possible to obtain a more precise corrected temperature. Indeed, it is visible in [Fig.3] that curve 4 (which corresponds to a period of 20 seconds) presents more oscillations than curve 5 (which corresponds to a period of 60 seconds).

[0074] According to a particular arrangement, the method 10 further comprises a step 133 of filtering the inverse response to obtain the corrected temperature. The filtering step 133 makes it possible to smooth the corrected temperature determined in step 132. In other words, as shown in [Fig. 3], the determination of step 132 can generate noise (i.e. the oscillations of curves 4 and 5). Curves 4 and 5 can be used as they are, but step 133 makes it possible to perform smoothing, making the result even more relevant.

[0075] Curves 7 and 8 of [Fig.3] diagram a smoothing over 30 seconds (curve 7) and a smoothing over 60 seconds (curve 8). As shown in [Fig.3], filtering (smoothing) makes it possible to minimize the noise that can be generated by the calculation of the corrected temperature.

[0076] Step 14 - Use

[0077] As indicated previously, the method 100 then comprises using (step 14) the corrected temperature in the temperature control device to regulate a temperature setpoint. In other words, the corrected temperature is used by the temperature control device to trigger or not trigger heating setpoints sent to heating devices controlled by the temperature control device.

[0078] This arrangement very advantageously makes it possible to compensate for the inertia of the temperature control device, to ensure temperature control which is as close as possible to the actual temperature of the room, which makes it possible to save energy.

[0079] Temperature control device

[0080] According to another aspect, there is provided a temperature control device comprising electronic circuitry (computer system 200) adapted to implement a method 10.

[0081] As shown diagrammatically in [Fig. 4], the computer system 200 may comprise, connected by a communication bus 210: a processor 201; a random access memory 202; a read-only memory 203, for example of the ROM (“Read Only Memory” in English) or EEPROM (“Electrically-Erasable Programmable Read Only Memory” in English) type; a storage unit 204, such as a hard disk HDD (“Hard Disk Drive” in English), or a storage media reader, such as an SD (“Secure Digital” in English) card reader; and an input-output interface manager 205.

[0082] The processor 201 is capable of executing instructions loaded into the RAM 202 from the ROM 203, an external memory, a storage medium (such as an SD card), or a communications network. When the computer system 200 is powered on, the processor 201 is capable of reading instructions from the RAM 202 and executing them. These instructions form a computer program enabling the implementation, by the processor 201, of the method 10.

[0083] All or part of the method 10 can thus be implemented in software form by executing a set of instructions by a programmable machine, for example a DSP (Digital Signal Processor) type processor or a microcontroller, or be implemented in hardware form by a machine or a dedicated component, for example an FPGA (Field Programmable Gate Array) or ASIC (Application-Specified Integrated Circuit) component. Generally speaking, the computer system 200 comprises electronic circuitry adapted and configured to implement, in software and / or hardware form, the method in relation to the computer system 200 in question.

[0084] Computer program product

[0085] According to another aspect, there is also provided a computer program product comprising program code instructions for executing the method 10.

[0086] Storage medium

[0087] According to another aspect, there is also provided a non-transitory storage medium on which the computer program comprising program code instructions for executing the method 10 is stored.

Claims

Claims

1. Method (10) for correcting a thermal inertia of a temperature control device (200) comprising electronic circuitry adapted to implement the method (10), the method (10) being characterized in that it comprises at least the following steps: - characterizing (11) the temperature control device to determine a time constant specific to the temperature control device; - acquiring (12) a measurement of a temperature; - correcting (13) the measured temperature by modeling the temperature control device in the form of a first-order or higher low-pass filter using the specific time constant to obtain a corrected temperature; - using (14) the corrected temperature in the temperature control device to regulate a temperature setpoint.

2. Method (10) according to claim 1, in which the characterization step (11) comprises: - applying (111) a predetermined temperature step to the temperature control device; - measuring (112) the time taken by the temperature control device to detect a predetermined percentage of the temperature step; - determining (113) the time constant from the measurement of the time taken by the control device to detect a predetermined percentage of the temperature step.

3. Method (10) according to claim 2 wherein the predetermined percentage of the temperature step is between 50% and 100%, preferably between 60% and 65% and even more preferably between 62% and 64%.

4. A method (10) according to any preceding claim, wherein the step of correcting (13) the measured temperature by modeling the temperature control device (200) as a first-order or higher filter using the time constant own to obtain a corrected temperature comprises: - Modeling (131) the temperature control device in the form of a first-order or higher low-pass filter using the own time constant; - Determining (132) an inverse response of the first-order or higher low-pass filter to estimate the corrected temperature.

5. The method (10) of claim 4, wherein the step of correcting (13) the measured temperature by modeling the temperature control device as a first-order filter using the natural time constant to obtain a corrected temperature further comprises filtering (133) the inverse response to obtain the corrected temperature.

6. A temperature control device (200) comprising electronic circuitry adapted to implement the method (10) according to any one of claims 1 to 5 comprising at least the following steps: - characterizing (11) the temperature control device to determine a time constant specific to the temperature control device; - acquiring (12) a measurement of a temperature; - correcting (13) the measured temperature by modeling the temperature control device in the form of a first-order or higher low-pass filter using the specific time constant to obtain a corrected temperature; - using (14) the corrected temperature in the temperature control device to control a temperature setpoint.

7. A computer program product comprising program code instructions for executing the method (10) according to any one of claims 1 to 5.

8. A non-transitory storage medium having stored thereon a computer program comprising program code instructions for executing the method (10) according to any one of claims 1 to 5, when said instructions are read from said non-transitory storage medium and executed by a processor.

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