Animal House Climate Control System and Method for Operating an Air Inlet of the Animal House using Timed Inlet Control

Abstract

An animal house climate control system uses a method for operating a baffle of an air inlet of an animal house with a motor using timed inlet control. The method includes performing a calibration sequence to calculate opening velocity and opening inertia values and closing velocity and closing inertia values. The method also includes moving the baffle from an initial position to a final position by calculating a calculated power on time for the motor using the opening inertia or closing inertia values. The method can also include calculating a real position error value by comparing the calculated on time for the motor and a measured on time for the motor and using the real position error value to calculate adjusted opening and closing velocity values.

Claims

1. A climate control system for an animal house, the climate control system comprising: a plurality of climate control input devices configured to measure a climate input selected from the group of temperature and static pressure, wherein the plurality of input devices are located in different portions of the animal house; a plurality of climate control ventilation fans; at least one air inlet used to control airflow into the animal house, the at least one air inlet having a baffle configured to change the area of the opening of the air inlet to vary the amount of air coming into the animal building; at least one actuator operably connected to the baffle of the at least one air inlet having a motor, the at least one actuator used to selectively control the position of the baffle; an open limit switch that is triggered when the baffle reaches a fully open position; a closed limit switch that is triggered when the baffle reaches a fully closed position; a sensor configured to read the current applied to the motor; and a control unit configured to receive input information from the plurality of climate control input devices and regulate the operation of the ventilating fans, wherein the control unit controls operation of the actuator using a calibrated timed position opening and closing commands to adjust the position of the baffle of the at least one air inlet wherein the control unit accounts for dragging delays and overshoot inertias at calibration and considers these dragging delays or inertias into the calibrated timed position opening and closing commands.

2. The climate control system of claim 1 wherein dragging delays and overshoot inertias are measured as the amount of time the baffle continues to move after the control unit has given a command to stop.

3. The climate control system of claim 2 wherein the inertias are calculated for open and close operation at different position of the baffle.

4. The climate control system of claim 3 wherein the control unit uses a calibration step that reads actuator motor current to determine when the actuator hits one of the opening and closing limit switches, and an air inlet calibration sequence to determine an open travel time, a close travel time, an open inertia, a close inertia, an open velocity and a close velocity.

5. The climate control system of claim 1 wherein the control unit moves the baffle from an initial position to a final position by calculating a calculated power on time for the motor using an opening inertia value or a closing inertia value.

6. A method for operating a baffle of an air inlet of an animal house with a motor using timed inlet control, the method comprising: performing a calibration sequence to calculate opening velocity and opening inertia values and closing velocity and closing inertia values; moving the baffle from an initial position to a final position by calculating a calculated power on time for the motor using the opening inertia or closing inertia values.

7. The method of claim 1 further comprising calculating a real position error value by comparing the calculated on time for the motor and a measured on time for the motor and using the real position error value to calculate adjusted opening and closing velocity values.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The above mentioned and other features of this invention will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

[0012] FIG. 1 is a schematic drawing of a climate control system of an animal house;

[0013] FIG. 2 is a calibration sequence for the climate control system;

[0014] FIG. 3 is a baffle opening sequence for the climate control system; and

[0015] FIG. 4 is an error correction sequence for the climate control system.

[0016] Corresponding reference characters indicate corresponding parts throughout the views of the drawings.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0017] The invention will now be described in the following detailed description with reference to the drawings, wherein preferred embodiments are described in detail to enable practice of the invention. Although the invention is described with reference to these specific preferred embodiments, it will be understood that the invention is not limited to these preferred embodiments. But to the contrary, the invention includes numerous alternatives, modifications and equivalents as will become apparent from consideration of the following detailed description.

[0018] Referring to FIG. 1, a schematic of an animal house 10 having a climate control system 20 is shown. The climate control system 20 has a plurality of climate control sensing or input devices, such as temperature or static pressure probes, indicated at 21. The sensing devices 21 may be located in different portions of the animal house 10 so that climate information, such as temperature and static pressure, may be received for the different portions. Although three input devices 21 are shown, it will be understood that this is for purposes of illustrations only, and that additional or fewer input devices may be provided, as required. The climate control system 20 also has a plurality of climate control output devices, such as ventilation fans and/or heaters, indicated at 23 mounted in the building 10. Although three heaters and ventilating fans 23 are shown, it will be understood that this is for purposes of illustrations only, and that additional or fewer heaters and fans may be provided, as required. Various air inlets such as sidewall inlets, ceiling inlets and or tunnel inlets, indicated at 25, are used by the climate control system 20 to control airflow into the animal house 10. Although three air inlets 25 are shown, it will be understood that this is for purposes of illustrations only, and that additional or fewer air inlets may be provided, as required.

[0019] The climate control system 20 has a main control unit 27, which incorporates a suitable controller, such as a microprocessor main control unit 28, which receives input information from the input devices 21 and regulates the operation of the ventilating fans and heaters 23 and the air inlets 25.

[0020] Each air inlet 25 has a baffle or a curtain 30 used to change the area of the opening of the air inlet 25 and vary the amount of air coming into the animal building 10. The position of the baffle 30 determines the air flow and air speed for a fixed ventilation power of the ventilating fans 23. The baffle 30 is positioned by an actuator 32 driven by a motor 34 controlled by the control unit 27. In one embodiment, the baffle 30 is moved by a linear actuator 32 driven by electric motor 34. As would be understood by one skilled in the art, rotary motion of the motor 34 is converted to linear displacement of the actuator 32 and thus movement of the baffle 30. The air inlet 25 also has an open limit switch 36 that is triggered when the baffle 30 reaches the fully open position and a closed limit switch 38 that is triggered when the baffle reaches the fully closed position.

[0021] In one embodiment, reading the current of the motor 34 lets the control unit 27 know every time a limit switch 36, 38 is hit, a situation that happens during normal operation. In one embodiment, each time one of the limit switches 36, 38 is hit, motor 34 current drops to zero. Desirably, the control unit 27 causes an automatic error position reset with each such occurrence. In operation, the actuator 32 is moved many times every hour to reposition the baffle 30 based on the inputs from the input devices 21. Depending on weather and animal conditions, the baffle 30 may be operated close to its fully extended or fully retracted position. Doing so, the baffle 30 hits limit switches 36, 38 and stops by itself even though the control unit 27 can continue to apply power. By reading motor current through a sensor in line with the commanding relays, the control unit 27 can determine when the actuator 32 hits a switch 36, 38, i.e., when the current drops to zero. Each time an actuator 32 hits a limit switch 36, 38 an automatic error position reset happens. Thus, mandatory called for position reset can be reduced to minimum, every 12 hours or so for which the actuator 32 has not hit a limit switch 36, 38. Moreover, a reset normally requires the control unit 27 to close (or open) the actuator 32 for a period of time equal to a full stroke (typically 60-120 seconds) even though it may reach position after only a few seconds. By reading motor current, reset time can be reduced to minimum and normal operation can resume as soon as motor current drops to zero.

[0022] Additionally, reading the current of the motor 34 lets the control unit 27 detect a malfunction of the air inlet 25 which may lead to animal discomfort or death. As an example, an actuator 32 that won't move in any direction (motor current stays at zero or is out of range) is defective and should backed-up by another air inlet 25 such as by opening wider another air inlet 25 or by using a separate air inlet 25.

[0023] The climate control system 20 uses a calibrated timed position method to adjust the position of the baffle 30 of the air inlet 25. An advantage of using timed position control is the method does not require problematic position sensing devices to sense the position of the baffle 30; the control unit 27 just needs to be calibrated to mathematically relate cumulative Open Time with opening. One problem with climate control systems 20 is that they drag at start and at stop leading to significant drift into opening calculations/estimates after 10-20 open and close cycles. According to one embodiment of the invention, the climate control system 20 accounts for drag and overshoot at calibration and considers these dragging delays or inertias into the opening and closing calculations. The time before stopping to move is measured as the amount of time the baffle 30 is still moving after the control unit 27 has given the command to stop. Inertia of the baffle 30 varies with load on the actuator 32. Thus, inertias are calculated for open and close operation at different position of the baffle 30 as the load on the actuator 32 may vary.

[0024] FIG. 2 illustrates a method for calibrating the climate control system 20. First, an automatic calibration step reads actuator motor 34 current to determine when the actuator 32 hits it's a limit switch 36, 38. Second, an air inlet calibration sequence is used to determine the open travel time, the close travel time, the open inertia, the close inertia, the open velocity and the close velocity. In the example calibration sequence for time based inlets:

[0025] TT.sub.o=Travel time open

[0026] TT.sub.c=Travel time close

[0027] i.sub.o=Inertia open

[0028] i.sub.c=Inertia close

[0029] t.sub.a=total movement time for inertia measurement

[0030] t.sub.b=small movement for inertia measurement

[0031] t.sub.c=remaining close time after known movement sequence

[0032] t.sub.o=remaining open time after known movement sequence

[0033] n=number of small movements for inertia measurement

[0034] v.sub.o=open velocity in %/sec.

[0035] v.sub.c=close velocity in %/sec. (close velocity is negative)

[0036] Using the measurements from the calibration sequence, inertia open (i.sub.o) and inertia close (i.sub.c) values are calculated. In one embodiment, the inertia open (i.sub.o) value is calculated using the following equation:

[00001]$i_o=\frac{-\left(n^2+2.Math.n\right).Math.t_b-\left(n+1\right).Math.t_c+\left(n+2\right).Math.t_a-t_o}{n^2+2.Math.n}$

[0037] In one embodiment, the inertia close (ic) value is calculated using the following equation:

t.sub.c=nt.sub.b+(m+1)t.sub.o+t.sub.ct.sub.a

[00002]$v_o=\frac{100}{{\mathrm{TT}}_o}$$v_c=-\frac{100}{{\mathrm{TT}}_c}$

[0038] Set t.sub.a, t.sub.b and n

[0039] Measure t.sub.c, t.sub.o, TT.sub.o, TT.sub.c while executing sequence.

[0040] With:

[0041] ta=10 sec

[0042] tb=2 sec

[0043] n=2

[0044] The inertia open (i.sub.o) value is calculated:

[00003]$i_o=\frac{24-3.Math.t_c-t_o}{8}$

[0045] The inertia close (ic) value is calculated:

t.sub.c=t.sub.c+3t.sub.a6

[0046] Desirably, inertia is measured in hundredth of a second for time-based inlets.

Time Based Inlet Movement

[0047] Turning now to FIG. 3, to move a baffle 30 from an estimated or known position to another, the on time for the actuator 32 can be calculated as follows:

[0048] Key:

[0049] Pi=Initial position

[0050] Pf=Final position

[0051] On time=Power on time needed for suited movement

[00004]$\mathrm{Open}.Math..Math.\mathrm{on}.Math..Math.\mathrm{time}=\frac{P_f-P_i}{v_o}-i_o$$\mathrm{Close}.Math..Math.\mathrm{on}.Math..Math.\mathrm{time}=\frac{P_f-P_i}{v_c}-i_c$

Accumulated Error and Reset

[0052] Turning now to FIG. 4, it is desired to calculate an accumulated error and reset. This section presents velocity correction theory and an application example. Relations presented here holds for a reset to closed position.

[0053] Let actuator A be at an estimated position of 50%, TT.sub.o=120 sec, v.sub.c=0.869%/sec, v.sub.o=0.830%/sec.

[0054] Last actuator movements were:

[0055] n.sub.o=32 movements in open direction

[0056] n.sub.c=18 movements in close direction

[00005]$C_{\mathrm{OT}}=\frac{P_f-P_i}{v_c}-i_c=\frac{0.Math.\text{-}.Math.50.Math.\%}{-0.869}-0.5=57.03.Math..Math.\sec ..Math.M_{\mathrm{OT}}=58.10.Math..Math.\sec$$\mathrm{Error}=M_{\mathrm{OT}}-C_{\mathrm{OT}}=1.07.Math..Math.\sec$

[0057] If |Error|1% and known last movements distribution, take the appropriate path shown in Table 1

TABLE-US-00001 TABLE 1 Reset type Error n.sub.o:n.sub.c Open time Close time Relation Closed Positive n.sub.o > n.sub.c Decrease = 1 Closed Positive n.sub.o < n.sub.c Decrease Increase 2 Closed Negative n.sub.o > n.sub.c Increase Decrease 3 Closed Negative n.sub.o < n.sub.c = Decrease 4 Open Positive n.sub.o > n.sub.c Increase Decrease 3 Open Positive n.sub.o < n.sub.c = Decrease 4 Open Negative n.sub.o > n.sub.c Decrease = 1 Open Negative n.sub.o < n.sub.c Decrease Increase 2

[00006]$\begin{array}{cc}{\mathrm{TT}}_o^{}={\mathrm{TT}}_o-\frac{n_c}{n_o+n_c}.Math.\mathrm{Error}=120-\frac{18}{18+32}.Math.1.07=119.61.Math..Math.v_o^{}=\frac{100}{{\mathrm{TT}}_o^{}}=\frac{100}{119.61}=0.836& 1\end{array}$

[00007]$\begin{array}{cc}{\mathrm{TT}}_o^{}={\mathrm{TT}}_o-\frac{n_o}{n_o+n_c}.Math.\mathrm{Error}.Math..Math.{\mathrm{TT}}_c^{}={\mathrm{TT}}_c+\frac{n_c}{n_o+n_c}.Math.\mathrm{Error}.Math..Math.v_o^{}=\frac{100}{{\mathrm{TT}}_o^{}}.Math..Math.v_c^{}=\frac{100}{{\mathrm{TT}}_c^{}}& 2\end{array}$

[00008]$\begin{array}{cc}{\mathrm{TT}}_o^{}={\mathrm{TT}}_o+\frac{n_o}{n_o+n_c}.Math.\mathrm{Error}.Math..Math.{\mathrm{TT}}_c^{}={\mathrm{TT}}_c-\frac{n_c}{n_o+n_c}.Math.\mathrm{Error}.Math..Math.v_o^{}=\frac{100}{{\mathrm{TT}}_o^{}}.Math..Math.v_c^{}=\frac{100}{{\mathrm{TT}}_c^{}}& 3\end{array}$

[00009]$\begin{array}{cc}{\mathrm{TT}}_c^{}={\mathrm{TT}}_c-\frac{n_o}{n_o+n_c}.Math.\mathrm{Error}.Math..Math.v_c^{}=\frac{100}{{\mathrm{TT}}_c^{}}& 4\end{array}$

[0058] Wherein increasing velocity shortens calculated movement times and decreasing velocity lengthens calculated movement times.

[0059] The foregoing has broadly outlined some of the more pertinent aspects and features of the present invention. These should be construed to be merely illustrative of some of the more prominent features and applications of the invention. Other beneficial results can be obtained by applying the disclosed information in a different manner or by modifying the disclosed embodiments. Accordingly, other aspects and a more comprehensive understanding of the invention may be obtained by referring to the detailed description of the exemplary embodiments taken in conjunction with the accompanying drawings.