CN113467243B - Hot pressing furnace temperature composite control method based on improved delay observer - Google Patents
Hot pressing furnace temperature composite control method based on improved delay observer Download PDFInfo
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- CN113467243B CN113467243B CN202110767214.1A CN202110767214A CN113467243B CN 113467243 B CN113467243 B CN 113467243B CN 202110767214 A CN202110767214 A CN 202110767214A CN 113467243 B CN113467243 B CN 113467243B
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- G05B13/00—Adaptive control systems, i.e. systems automatically adjusting themselves to have a performance which is optimum according to some preassigned criterion
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Abstract
The invention relates to the field of hot-pressing furnace temperature control, in particular to a hot-pressing furnace temperature composite control method based on an improved delay observer.
Description
Technical Field
The invention relates to the field of temperature control of a hot-pressing furnace, in particular to a method for compensating system disturbance by establishing a delay observer and a disturbance observer and combining the delay observer and the disturbance observer, which effectively inhibits adverse effects of time delay on a system, thereby improving the stability (disturbance resistance) of the system under disturbance and meeting the performance requirements of the hot-pressing furnace on temperature control.
Background
The temperature control system is used as an important component of intelligent equipment and is widely applied to the industrial field. With the development of industrial and intelligent manufacturing technologies, the precision requirement on a temperature control system is further improved, and whether the hot-pressing furnace equipment can be stably and accurately maintained at the required temperature is always an important aspect of research in the field of hot-pressing furnace temperature control. The accuracy and stability of the temperature control of the hot-pressing furnace can be influenced by disturbance caused by environmental condition change, large delay of a system and uncertainty of large inertia. Therefore, it is necessary to improve the response speed and the anti-interference capability of the system.
PID control systems which are controlled in proportion (P), integral (I) and derivative (D) of the deviation are nowadays more common in temperature control strategies. The conventional PID has a simple and practical structure, but the field PID parameter setting is troublesome, is easy to be interfered by the outside, and has overlong adjusting time for the process with large delay. The precise temperature is an important factor influencing the working process of the equipment, and the temperature of the equipment is required to quickly and accurately reach a set value in many times. Therefore, domestic and foreign scholars continuously improve and perfect on the basis, for example, the PID control strategy based on the neural network is utilized to optimize the system temperature control, but the method is easy to cause control parameter setting errors. In order to improve the stability and the anti-interference capability of a temperature control system of the hot pressing furnace, a sliding mode controller is selected, the sliding mode observer is few in adjusting parameters, fast in response speed, insensitive to disturbance and strong in anti-interference capability.
But the control system still has a delay problem. The time-lag system is a system with signal delay in time transmission, and the change of a controlled object lags behind disturbance due to the lag, so that the system is easy to be unstable. In order to solve the time lag problem of the temperature control system of the autoclave, a Delay Observer (Delay Observer) is designed in the system. The output before the delay time tau second is observed by the delay observer and then fed back to the input, so that the problem of system time lag is solved.
In summary, the present invention provides a composite control method for the temperature of a hot pressing furnace based on an improved delay observer, that is, the required temperature requirement is quickly and accurately met through sliding mode control, and the delay observer is used to observe the required temperatureThe output before the second solves the problem of time delay of the control system, and simultaneously compensates the external interference on the system by combining with a disturbance observer, thereby effectively improving the disturbance resistance of the system.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the method for designing the sliding mode controller by combining the delay observer and the disturbance observer is provided, so that the accuracy and the stability of the temperature control system of the hot-pressing furnace are improved, the temperature control system has good disturbance resistance, adverse effects caused by time delay can be effectively solved, and the performance requirement of the hot-pressing furnace on temperature control is better met.
The invention solves the technical problem by adopting the specific scheme that: by adopting a sliding mode control method based on an exponential approaching law, the hot-pressing furnace system can reach the required temperature quickly and accurately, the adverse effect caused by time delay is effectively solved through the design of a delay observer, and the compensation of external disturbance is completed by utilizing a disturbance observer. The method comprises the following steps:
a hot-pressing furnace temperature compound control method based on an improved time delay observer is characterized in that a control object transfer function is defined asWhereinIn order to be a lag link,for lag parameters, a, b and k are all system parameters, and the transfer function is converted into a time domain expression asWhere y (t) is the system temperature output and u (t) is the control input, including:
selecting a disturbance observer to predict the external disturbance of the system, and feedforward compensating the disturbance estimated value to a forward channel behind the controller,estimating a system by a delay observerOutput before secondAnd stateAnd fed back to the input end of the sliding mode controller, and the sliding mode controller receivesAnd stateAnd according to the set sliding mode surface and the control rate, the system moves according to the set state track through the sliding mode controller.
In the above method for compositely controlling the temperature of the hot-pressing furnace based on the improved delay observer, the disturbance observer is defined based on the following:
wherein Q(s) is a second order low pass filter, Y(s) is a system output, U(s) is a control input,is the inverse of the minimum phase part of the transfer function of the systemTime of flight
In the above composite control method for the temperature of the hot pressing furnace based on the improved delay observer, the delay observer is defined based on the following:
getThenIs shown asWhereinIs a matrix of systematic coefficients, H ═ 0, k]TA matrix is input to the system. The system has hysteresis and the system is a single-input single-output system, so that the output signal is defined to have delay,for the time delay of the output to be,wherein, C ═ 10]. At this timeAiming at the delay systemTaking the observed valueThe delay observer is then:
In the above composite control method for the temperature of the hot pressing furnace based on the improved delay observer, the sliding mode controller is defined based on the following:
definition errorSliding mode function of sliding mode controllerWherein c > 0, [ c 1 ]]Is a sliding mode surface parameter matrix. By means of a time-delay observerAndthe control law of the sliding mode controller designed based on the exponential approaching law is as follows:wherein epsilon and m are approach law parameters, epsilon is more than 0, m is more than 0, and in order to avoid larger system buffeting, a saturation function sat(s) is adopted in the controller to replace a sign function sat(s), namelyWhere Δ is the boundary layer.
Compared with the prior art, the invention has the following advantages:
(1) the sliding mode controller is used for controlling the temperature of the hot pressing furnace, so that the speed of the system reaching the set temperature is effectively increased, and the response speed of the system is accelerated.
(2) In order to solve the inherent time lag problem of a control system, a time delay observer is designed. The output of the observer and the actual input form a linear system without time lag through the time delay observer, the influence of the time lag is eliminated, and the design of the sliding mode controller is simplified.
(3) Compared with the conventional method of performing PI feedback, the disturbance observer can estimate disturbance in advance and actively perform disturbance compensation, and the method has the advantages of having the advance and effectively improving the disturbance resistance of the system.
Drawings
FIG. 1 is a block diagram of a hot-pressing furnace temperature compound control system based on an improved delay observer.
FIG. 2 is a graph comparing the output of the present invention with a conventional PID.
Detailed Description
The following detailed description of embodiments of the invention refers to the accompanying drawings.
The invention solves the technical problem by adopting the specific scheme that: by adopting a sliding mode control method, the hot pressing furnace system can reach the required temperature quickly and accurately, the adverse effect caused by time delay is effectively solved through the design of the delay observer, and the compensation of system disturbance is completed by utilizing the disturbance observer.
Fig. 1 is a block diagram of a hot-pressing furnace temperature composite control system based on an improved delay observer, wherein SMC is a sliding-mode controller; d(s) is the system disturbance; the virtual frame 1 is a disturbance observer; the virtual frame 2 is a delay observer; gp(s) is the actual controlled object;andrespectively, a disturbance observation value, an output observation value before time lag and a state.
Forcing the system to move according to a set state trajectory by a sliding mode controller, Gp(s) is an actual controlled object, a disturbance Observer is selected to predict external disturbance possibly suffered by the system, a disturbance estimation value is feedforward compensated to a forward channel, a Delay Observer is used as a Delay Observer, and the system is estimated through the Delay ObserverOutput before secondAnd stateAnd fed back to the input of the sliding mode controller.
FIG. 2 is a graph showing the temperature control output of PID-based control of the furnace temperature and the temperature control output of the modified time-delay observer-based furnace temperature combination. Wherein, the solid curve is a set temperature value; the SMC + D-DOV dotted line is an output curve of the invention; the dashed PID line is the output curve for conventional PID-based temperature control.
According to a mathematical model of temperature control, a sliding mode controller is constructed in Matlab/Simulink, so that the control process of the whole temperature control system is constructed, meanwhile, a common PID control temperature control system is also constructed, and the output contrast diagram is obtained after operation. The set temperature was 250 ℃, the black dashed line is the PID output curve, and the blue dashed line is the output curve based on the invention. According to the graph in the figure, the hot pressing furnace temperature control system based on the invention can reach the preset temperature value more quickly, has smaller overshoot and is stabilized at the set value more quickly. When disturbance exists in the system, the temperature control system based on the invention is more quickly stabilized at a preset value, and the robustness of the system is improved. The method comprises the following specific steps:
and the temperature of the hot-pressing furnace is controlled by using a sliding mode controller. The sliding mode controller can force the system to move according to a state track of a preset sliding mode according to the current state of the system in a dynamic process. The method is characterized in that the sliding mode can be designed and is independent of object parameters and disturbance. The method specifically comprises the following steps:
1. definition errorDesigning sliding mode functionWherein c is more than 0, and the sliding mode control rate is as follows:wherein epsilon and m are approximate law parameters, epsilon is more than 0, m is more than 0, and the temperature of the hot-pressing furnace can quickly reach the target temperature yd(s)。
2. Because of time lag of the system, in order to eliminate the influence of the time lag on the stability of the systemAnd designing a delay observer. System by time delay observerThe output and state before the second are observed and fed back, so that the output of the observer and the actual input form a linear system without time lag. The feedback control of the delay observer not only eliminates the influence of time lag, but also simplifies the design of the sliding mode controller.
3. The lumped disturbance of the system is observed by a disturbance observer and feed-forward compensated to the forward channel.
4. By designing the sliding mode controller and utilizing the combination of the delay observer and the disturbance observer, the temperature of the hot-pressing furnace is accurately controlled, the disturbance resistance of the system is effectively improved, and the influence caused by the time lag problem of the system is solved. The method specifically comprises the following steps:
(1) considering objectsEstablishingTime domain mathematical model, where is the system temperature output and u (t) is the control input.
(2) GetThen the above formulaCan be expressed asWhereinIs a matrix of systematic coefficients, H ═ 0, k]TA matrix is input to the system. Because the system is a single-input single-output system, I can see that the output signal has delay,for the time delay of the output to be,wherein, C ═ 10]. At this timeAiming at the delay systemTaking the observed valueDesigning a time delay observer:wherein the content of the first and second substances,is thatN is an error gain matrix.
Is provided withLeading: for linear delay systemsThe stability condition is sigma I-A-Be-AσThe real part of the feature root is negative, and the delay system is exponentially stable. Thus, can obtainThen according to the lemma, the stability condition of the delay observer is: selecting proper K to make the designed delay observerIs negative, the delay systemThe exponent δ (t) converges to 0 for exponential stability, i.e., t → ∞.
(3) Considering object model formulaDefinition errorDesigning sliding mode functions for sliding mode controllersWherein c > 0, [ c 1 ]]Is a sliding mode surface parameter matrix. Observing by using the time-delay observer in (2)Andthe control law of the sliding mode controller designed based on the exponential approaching law is as follows:wherein epsilon and m are approach law parameters, epsilon is more than 0, m is more than 0, and in order to avoid larger system buffeting, a saturation function sat(s) is adopted in the controller to replace a sign function sgn(s), namelyWhere Δ is the boundary layer.
(4) Mathematical model formula considering objectsInverse of minimum phase according to transfer function of controlled systemDesigning a disturbance observer:wherein Q(s) is a second order low pass filter, Y(s) is a system output, U(s) is a control input,is the inverse of the minimum phase part of the transfer function of the systemTime of flight
The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications or additions may be made to the described embodiments or alternatives may be employed by those skilled in the art without departing from the spirit or ambit of the invention as defined in the appended claims.
Claims (3)
1. A hot-pressing furnace temperature compound control method based on an improved time delay observer is characterized in that a control object transfer function is defined asWherein e-τsFor a lag link, tau is a lag parameter, a, b and k are system parameters, and a transfer function is converted into a time domain expressionWhere y (t) is the system temperature output and u (t) is the control input, including:
selecting a disturbance observer to predict external disturbance on the system, feeding back and compensating a disturbance estimation value to a forward channel behind the controller, and estimating the output of the system before tau seconds by using a delay observerAnd stateAnd fed back to sliding mode controlInput of the controller, reception of the sliding mode controllerAndenabling the system to move according to a set state track through a sliding mode controller according to a set sliding mode surface and a set control rate;
the sliding mode controller is based on the following definitions:
definition errorSliding mode function of sliding mode controllerWherein c > 0, [ c 1 ]]Observing the parameter matrix of the sliding mode surface by using a delay observer modelAndthe control law of the sliding mode controller designed based on the exponential approaching law is as follows:wherein epsilon and m are approach law parameters, epsilon is more than 0, m is more than 0, and in order to avoid larger system buffeting, a saturation function sat(s) is adopted in the controller to replace a sign function sgn(s), namelyWhere Δ is the boundary layer.
2. The hot-pressing furnace temperature compound control method based on the improved delay observer is characterized in that the disturbance observer is defined according to the following steps:
3. The hot-pressing furnace temperature compound control method based on the improved delay observer is characterized in that the delay observer is defined according to the following steps:
getThenIs shown asWhereinIs a matrix of systematic coefficients, H ═ 0, k]TFor the system input matrix, the system has hysteresis and the system is a single input single output system, so that the output signal is defined to have a delay, τ is the time delay of the output,wherein, C ═ 10]At this timeAiming at the delay systemTaking the observed valueThe delay observer is then:
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