Linear temperature rise control method

Abstract

The invention discloses a linear temperature rise control method, which belongs to the technical field of temperature control, and comprises the following steps: self-tuning; performing constant-temperature control; and carrying out linear temperature rise control. In the constant temperature process, proportional differential control is adopted, then the gradient value in the heating process is calculated, integral control is added according to the set gradient value, and at the moment, overshoot can be effectively restrained; and the speed concept is introduced, so that the temperature rise linearity becomes good, the strong wave phenomenon always existing in the temperature rise process is overcome, meanwhile, the PID values of linear temperature rise and constant temperature are unified, PID parameters do not need to be manually tested, and the debugging time is shortened.

Description

Technical Field

[0001] The invention relates to the technical field of temperature control, and in particular to a linear temperature increase control method. Background Art

[0002] The existing method for temperature control is mainly PID control. However, in the actual PID control process, some systems need to control linear temperature rise. However, the current method of linear temperature rise is generally to split the temperature rise process into multiple targets, set the target value according to the control time each time, and then the PID controller calculates normally. This will cause two problems. One is that when the temperature rises, the temperature rise curve shows obvious waves and the temperature rise curve is poorly linear. The second is that the overshoot is more serious. In addition, two PID controllers are generally used for constant temperature and linear temperature rise, which is time-consuming and labor-intensive to adjust and inefficient.

[0003] The above problems need to be solved urgently, and for this purpose, a linear temperature rise control method is proposed. Summary of the invention

[0004] The technical problem to be solved by the present invention is: how to solve the problem of poor linearity of the heating process and severe overshoot in the current linear heating method, and unify the linear heating and constant temperature PID controllers, providing a linear heating control method.

[0005] like Figure 1 As shown, the present invention solves the above technical problems through the following technical solutions, and the present invention comprises the following steps:

[0006] S1: Perform self-tuning on the PID controller and calculate the PID parameters, including the proportional parameter m_p, the integral parameter m_i and the differential parameter m_d;

[0007] S2: After PID self-tuning is completed, the control temperature is set to the set target value F, and the target temperature T is set and whether linear temperature rise is required;

[0008] S3: When "No" is selected, that is, constant temperature control is required, the temperature rise gradient threshold is set, and PD control is performed on the temperature. At this time, the temperature rise gradient threshold is judged. When the temperature rise gradient threshold requirement is reached, I control is added to perform complete PID control.

[0009] S4: When the selection is yes, that is, linear temperature rise control is required, the entire temperature rise process is divided into sections, the control interval t and the temperature rise rate V per minute are set, the temperature value S that can be raised by a single control interval t is calculated, and then the temperature rise target Tj for each stage is determined;

[0010] S5: setting a constant temperature control threshold M and a linear temperature rise allowable range D, and scaling the P value according to the system resolution to obtain a scaling factor sc;

[0011] S6: Compensate for the temperature rise error and calculate the compensation value;

[0012] S7: Calculate the temperature rise difference D1 between two adjacent times and update the I value;

[0013] S8: Calculate the pwm, and determine whether the actual temperature R at the current moment reaches the target temperature T for the first time. If it does not reach, return to step S6. If it reaches, enter step S9;

[0014] S9: At this time, it is converted to a constant temperature state, record the current I value, set the constant temperature integral quantity as I_I. If it exceeds the constant temperature control threshold M, calculate the updated I value and calculate the pwm;

[0015] S10: When the actual temperature R at the current moment first drops within the constant temperature control threshold M for the first time, that is, when R < T + M, perform constant temperature PID control based on the current I value.

[0016] Furthermore, in the step S1, the specific processing process is as follows:

[0017] S11: Set the tuning target value F. The maximum value of the pwm output of the system is 1, and the minimum value is 0;

[0018] S12: When reaching the tuning target value, the input pwm is the minimum value. When it is lower than the tuning target value, the input pwm is the maximum value;

[0019] S13: Cross - repeat step S12 at least three times to obtain multiple amplitudes and the corresponding periods;

[0020] S14: Calculate the PID parameters according to the last two periods and the corresponding amplitudes, including the proportional parameter m_p, the integral parameter m_i, and the derivative parameter m_d.

[0021] Furthermore, in the step S14, through the empirical formula of the algorithm to calculate the PID parameters.

[0022] Furthermore, the specific processing process is as follows:

[0023] S31: After the PID self - tuning is completed, control the temperature to stabilize at the tuning target value F, and set the target temperature T;

[0024] S32: When selecting constant temperature, first set the temperature rise gradient threshold. At this time, the pwm is in the PD control mode, and the control formula is as follows:

[0025] pwm = m_i * err + m_d * lasterr

[0026] Where, the target temperature is T, the actual temperature at the current moment is R, and the actual temperature at the previous moment is R1, then err = TR, lasterr = R-R1;

[0027] S33: When the temperature rise gradient is less than the temperature rise gradient threshold, the PWM switches to the PID control mode, and the control formula is as follows:

[0028] I=I+m_i*err

[0029] pwm=m_p*err+I+m_d*lasterr

[0030] Where I is the integral of the error.

[0031] Furthermore, the calculation formula for the temperature value S that can be increased by a single control interval t is as follows:

[0032] S=V / 60*1000*t.

[0033] Furthermore, in step S6, when lasterr≤S, the compensation value errp=err+lasterr, and when lasterr>S, the compensation value errp=err.

[0034] Furthermore, if D1>S and TR>D are satisfied at the same time, then I=I-m_i*err; otherwise, I=I+m_i*err.

[0035] Furthermore, in step S8, the calculation formula of pwm is as follows:

[0036] pwm=m_p*sc*errp+I+m_d*lasterr.

[0037] Furthermore, in step S9, the updating formula of the I value is as follows:

[0038] I = I*(threshold value / portion exceeding the threshold value)+I_I*(1-(threshold value / portion exceeding the threshold value))

[0039] Among them, the threshold is the constant temperature control threshold M, and I_I is the I value when the target temperature T is first reached;

[0040] Furthermore, in step S10, the constant temperature PID control formula is as follows:

[0041] pwm=m_p*err+I+m_d*lasterr

[0042] Among them, I=I+m_i*err.

[0043] Compared with the prior art, the present invention has the following advantages: the linear temperature rise control method adopts proportional differential control in the constant temperature process and then calculates the gradient value in the temperature rise process, and adds integral control according to the set gradient value, which can effectively suppress overshoot; and introduces the concept of speed to improve the temperature rise linearity, overcome the strong wave phenomenon that always exists during temperature rise, and at the same time unify the PID values ​​of linear temperature rise and constant temperature, and the PID parameters do not need to be manually tested, which reduces the debugging time. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a schematic flow chart of the main steps of the linear temperature rise control method of the present invention;

[0045] Figure 2 1 is a flow chart of a linear temperature rise control method in an embodiment of the present invention. DETAILED DESCRIPTION

[0046] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0047] like Figure 2 As shown, this embodiment provides a technical solution: a linear temperature rise control method, comprising the following steps:

[0048] Step 1: Assume that the setting target value F is 100℃, the maximum value of the system's PWM (duty cycle) output is 1, and the minimum value is 0. When the setting target value is reached, the input PWM is the minimum value, and when it is lower than the setting target value, the input PWM is the maximum value. In order to increase the speed, three cycles are generally run to obtain the amplitude and cycle time. The last two cycles are used to calculate the PID parameters. The specific calculation method is to use The empirical formula of the algorithm is used to obtain the PID parameters m_p, m_i and m_d, where m_p is the proportional parameter, m_i is the integral parameter, and m_d is the differential parameter.

[0049] Step 2: After PID self-tuning is completed, the control temperature is stabilized at 100 degrees, and the target temperature T is set to 150 degrees. If constant temperature control is selected, the temperature rise gradient threshold is first set. For simple identification, the temperature rise gradient threshold is set to 1, then PWM is controlled by PD, and the control formula is: PWM = m_i*err + m_d*lasterr, (where err = T-actual temperature R at the current moment, lasterr = R-R1, R1 is the actual temperature at the previous moment), when the temperature rise gradient is less than 1, it switches to PID control mode, and the control formula is: I = I + m_i*err, PWM = m_p*err + I + m_d*lasterr.

[0050] It should be noted that in each control interval in step 2, it is necessary to judge whether the heating gradient exceeds the heating gradient threshold. When the heating gradient has not exceeded the heating gradient threshold, PD control is always used. After exceeding the heating gradient threshold for the first time, PID control is used subsequently and PD control is no longer used.

[0051] Step 3: If linear heating is selected, the basic parameters are first determined. The basic parameters are set as follows: 1. Control interval 50ms, 2. Heating rate V=10℃ / minute, then S=(10 / 60000)*50; the actual temperature at the current moment is R=T=100, then the stage heating target of each control is Tj=Tj+S (Tj is the stage heating target, so it is always changing and will slowly rise to the final target value T); the actual temperature at the current moment is R, the constant temperature control threshold M is set to 0.5℃, and the linear heating allowable range D is set to 0.1℃.

[0052] Step 4: Enlarge the P value. The enlargement factor needs to be set according to the system resolution. Generally, the higher the resolution, the smaller the value will be, and the smaller the resolution, the larger the value will be. The default enlargement is 2 times (when the resolution is 0.01 degrees)

[0053] Step 5: Compensate for the temperature rise error. When lasterr≤S, the compensation value errp=err+lasterr. When lasterr>S, errp=err.

[0054] Step 6: Calculate the temperature difference D1 between two adjacent temperature rises. If D1>S and TR>D are both satisfied, then I=I-m_i*err; otherwise I=I+m_i*err;

[0055] Step 7: Calculate pwm=m_p*2(amplification factor)*errp+I+m_d*lasterr; if pwm<0, pwm is 0, if>1, pwm is 1, if I>1, I is 1, if I<0, I is 0;

[0056] Step 8: Determine whether the actual temperature R reaches the final target value of the linear heating up of 150. If not, return to step 5. If reached, proceed to step 9.

[0057] Step 9: At this time, the temperature is converted to a constant temperature state, the current I value is recorded, and the constant temperature integral is set to I_I. If the constant temperature control threshold M is exceeded (0.5°C in this embodiment), the weighted I value is calculated = I*(threshold value / part exceeding the threshold value)+I_I*(1-(threshold value / part exceeding the threshold value)), and then pwm is calculated; wherein the threshold value is the constant temperature control threshold value M, and I_I is the I value when the target temperature T is first reached;

[0058] Step 10: When the actual temperature R falls back to the constant temperature control threshold M for the first time, that is, <150.5, the constant temperature PID control is performed normally based on the current I as the basic value. The control formula is: pwm=m_p*err+I+m_d*lasterr, where I=I+m_i*err.

[0059] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A linear temperature rise control method, characterized in that: It includes the following steps: S1: Perform self-tuning on the PID controller to calculate and obtain PID parameters, including the proportional parameter m_p, the integral parameter m_i, and the derivative parameter m_d; S2: After the PID self-tuning is completed, control the temperature to the set target value F, set the target temperature T, and determine whether linear heating is required; S3: When the choice is no, that is, constant temperature control is required, set the heating gradient threshold. At this time, perform PD control on the temperature, and at the same time judge the heating gradient threshold. When the heating gradient threshold requirement is met, add I control to perform complete PID control; S4: When the choice is yes, that is, linear heating control is required, divide the entire heating process into segments, set the control interval t and the heating rate V per minute, calculate the temperature value S that can be increased in a single control interval t, and then determine the stage heating target Tj for each time; S5: Set the constant temperature control threshold M and the linear heating allowable range D, and scale the P value according to the system resolution to obtain the scaling coefficient sc; S6: Compensate for the heating error and calculate the compensation value; S7: Calculate the difference D1 between two adjacent heating increments and update the I value; S8: Calculate the pwm, and judge whether the actual temperature R at the current moment reaches the target temperature T for the first time. If it does not reach, return to step S6. If it reaches, enter step S9; S9: At this time, switch to the constant temperature state, record the current I value, set the constant temperature integral as I_I. If it exceeds the constant temperature control threshold M, calculate the updated I value and calculate the pwm; S10: When the actual temperature R at the current moment first drops within the constant temperature control threshold M for the first time, that is, R < T + M, perform constant temperature PID control based on the current I value.

2. A linear temperature rise control method according to claim 1, characterized in that: In the step S1, the specific processing process is as follows: S11: Set the tuning target value F. The maximum pwm output of the system is 1 and the minimum is 0; S12: When the tuning target value is reached, the input pwm is the minimum value. When it is lower than the tuning target value, the input pwm is the maximum value; S13: Cross-repeat step S12 at least three times to obtain multiple amplitudes and corresponding periods; S14: Calculate the PID parameters, including the proportional parameter m_p, the integral parameter m_i, and the derivative parameter m_d, according to the last two periods and the corresponding amplitudes.

3. A linear temperature rise control method according to claim 2, characterized in that: In step S14, by The algorithm's empirical formula calculates the PID parameters.

4. A linear temperature rise control method according to claim 2, characterized in that: In the step S3, the specific processing process is as follows: S31: After the PID self-tuning is completed, control the temperature to stabilize at the tuning target value F and set the target temperature T; S32: When constant temperature is selected, first set the heating gradient threshold. At this time, the pwm is in the PD control mode, and the control formula is as follows: pwm = m_i * err + m_d * lasterr where the target temperature is T, the actual temperature at the current moment is R, and the actual temperature at the previous moment is R1, then err = T - R, lasterr = R - R1; S33: When the heating gradient is less than the heating gradient threshold, the pwm switches to the PID control mode, and the control formula is as follows: I = I + m_i * err pwm = m_p * err + I + m_d * lasterr where I is the integral of the error.

5. A linear temperature rise control method according to claim 4, characterized in that: In step S4, the calculation formula of the temperature value S that can be increased by a single control interval t is as follows: S=V / 60*1000*t.

6. A linear temperature rise control method according to claim 5, characterized in that: In step S6, when lasterr≤S, the compensation value errp=err+lasterr, and when lasterr>S, the compensation value errp=err.

7. A linear temperature rise control method according to claim 6, characterized in that: In step S7, if D1>S and TR>D are satisfied at the same time, I=I-m_i*err; otherwise, I=I+m_i*err.

8. A linear temperature rise control method according to claim 7, characterized in that: In step S8, the calculation formula of pwm is as follows: pwm=m_p*sc*errp+I+m_d*lasterr.

9. A linear temperature rise control method according to claim 8, characterized in that: In step S9, the updating formula of the I value is as follows: I = I*(threshold value / portion exceeding the threshold value)+I_I*(1-(threshold value / portion exceeding the threshold value)) The threshold is the constant temperature control threshold M, and I_I is the I value when the target temperature T is reached for the first time.

10. A linear temperature increase control method according to claim 9, characterized in that: In step S10, the constant temperature PID control formula is as follows: pwm=m_p*err+I+m_d*lasterr Among them, I=I+m_i*err.

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