An ultra-precision lithography equipment actuator fault-tolerant control method

Abstract

The application discloses an ultra-precision lithography equipment actuator fault-tolerant control method, a trajectory generator C r generates a reference position signal r and an acceleration signal a; the r and a state observer output signal are subtracted, and a feedback controller C fb obtains a feedback control signal u fb ; the a passes through a feedforward controller C ff to obtain a feedforward control signal u ff ; the u ff and the u fb are added and pass through an output decoupling matrix GB to obtain an actuator control signal u act ; the u act and an actual position signal y pass through a virtual actuator to obtain a virtual actuator compensation control signal u va and an output signal y va ; the u act and the u va are added and pass through an electric control system to obtain an actuator actual output signal F act ; the F act passes through an ultra-precision lithography equipment motion stage system P to obtain an actual position signal y; the y and the y va are added to obtain a reconstructed system state signal y f , the y f and the u act pass through a state observer to obtain a state observer output signal The application can play a better fault-tolerant control role when an actuator of an ultra-precision motion stage system has an output degradation fault.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of ultra-precision equipment manufacturing, and relates to an ultra-precision lithography equipment actuator fault-tolerant control method. BACKGROUND

[0002] In the field of high-end equipment manufacturing, an ultra-precision lithography equipment motion table plays a vital role, and is widely used in scenes with extremely high requirements for motion precision such as semiconductor manufacturing. As a core component of the ultra-precision lithography equipment motion table system, the performance of the actuator is directly related to the stability and motion precision of the ultra-precision lithography equipment motion table system.

[0003] Generally, a feedforward-feedback compound controller is used in the control system of the ultra-precision lithography equipment motion table, and such a controller does not have fault-tolerant capability. In actual operation, the actuator may be affected by complex working environment, mechanical wear and tear, element aging and other factors, and may have various faults. A common fault type is output degradation, which may cause abnormal motor power output, reduce the positioning precision of the ultra-precision lithography equipment motion table system, cause product quality and yield to decrease, and even cause the mechanical structure of the system to be damaged, resulting in huge economic losses. Therefore, a fault-tolerant control method must be designed for the output degradation fault of the actuator of the ultra-precision lithography equipment motion table to ensure the closed-loop stability and tracking precision of the ultra-precision lithography equipment motion table system under fault conditions. SUMMARY

[0004] In order to solve the problem of closed-loop stability and tracking precision reduction of the ultra-precision lithography equipment motion table under the condition of actuator output degradation fault in actual operation, the application provides an ultra-precision lithography equipment actuator fault-tolerant control method. The application can play a good fault-tolerant control role when the actuator of the ultra-precision motion table system has an output degradation fault, can ensure the closed-loop stability and tracking precision, and further improve the reliability and fault tolerance of the ultra-precision motion table system.

[0005] The purpose of the application is achieved by the following technical solutions:

[0006] An ultra-precision lithography equipment actuator fault-tolerant control method comprises the following steps:

[0007] Step 1: design a feedforward controller C ff and a feedback controller C fb ;

[0008] Step 2: design an output decoupling matrix GB;

[0009] Step 3: generate a reference position signal r and a reference acceleration signal a of the ultra-precision lithography equipment motion table system P by a trajectory generator C r ;

[0010] Step 4: Connect the reference position signal r and the state observer output signal The difference is calculated to obtain the position tracking error signal e, which is then passed through the feedback controller C. fb The feedback control signal u is obtained fb The reference acceleration signal a passes through the feedforward controller C. ff Obtain the feedforward control signal u ff ;

[0011] Step 5: Feedforward control signal u ff With feedback control signal u fb The sum is used to obtain the logic axis control signal u. cor Logic axis control signal u cor The actuator control signal u is obtained after passing through the output decoupling matrix GB. act ;

[0012] Step Six: Actuator Control Signal u act The actual position signal y is processed by the virtual actuator to obtain the virtual actuator compensation control signal u. va and the virtual actuator output signal y va ;

[0013] Step 7: Actuator control signal u act and virtual actuator compensation control signal u va The compensated control signal u is obtained by adding them together. c The compensated control signal u c The actual output signal F of the actuator is obtained through the electronic control system. act ;

[0014] Step 8: Actual output signal F of the actuator act The actual position signal y is obtained through the motion stage system P of the ultra-precision lithography equipment;

[0015] Step 9: Compare the actual position signal y with the virtual actuator output signal y va The summation yields the reconstructed system state signal y. f Reconstruct the system state signal y f and actuator control signal u act The output signal of the state observer is obtained after passing through the state observer. This forms a closed-loop control.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] 1. The application adds a reconstruction module based on a virtual actuator and a state observer in a closed-loop control circuit without changing the original controller, compensates for the influence of actuator output degradation through the reconstruction module, ensures closed-loop stability and tracking accuracy, and improves the reliability and fault tolerance of the motion table of the ultra-precision lithography equipment.

[0018] 2. Compared with the traditional control method, the application can ensure the closed-loop stability under the condition of actuator output degradation, limit the tracking error within a certain range, and provide satisfactory tracking accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The figure is a schematic diagram of the fault-tolerant control method of the ultra-precision lithography equipment motion table based on control reconstruction.

[0020] Figure 2 The figure is the physical layout of the actuator of the ultra-precision lithography equipment motion table.

[0021] Figure 3 The figure is the reference signal in the embodiment of the application.

[0022] Figure 4 The figure is the position tracking error signal when the actuator is degraded to different degrees before the method of the application is adopted.

[0023] Figure 5 The figure is the position tracking error signal when the actuator is degraded to different degrees after the method of the application is adopted. DETAILED DESCRIPTION

[0024] The technical solutions of the application will be further described below in combination with the drawings, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the application without departing from the spirit and scope of the technical solutions of the application shall be covered in the protection scope of the application.

[0025] The application provides an actuator fault-tolerant control method for ultra-precision lithography equipment, as shown in the figure, the method comprises the following steps: Figure 1

[0026] Step 1: Design a feedforward controller C ff and a feedback controller C fb .

[0027] In this step, the feedforward controller C ff has the following structure:

[0028] C ff (s)=K ff ms 2

[0029] Wherein, s is the Laplace operator, K​ff is the feedforward gain, m is the mass of the motion stage system of the ultra-precision lithography equipment.

[0030] In this step, the feedback controller C fb is composed of a PID controller C PID and a low-pass filter C lp , wherein:

[0031] The PID controller C PID has the following structure:

[0032]

[0033] wherein, assuming that the closed-loop bandwidth is f bw , the frequency ratio is α; K p is the proportional gain and K p = m (2πf bw ) 2 / α, f i is the integral frequency and f i = f bw / α 2 , f d is the derivative frequency and f d = f bw / α.

[0034] The low-pass filter C lp has the following structure:

[0035]

[0036] wherein, f lp is the low-pass filter cutoff frequency and f lp = αf bw , z lp is the low-pass filter damping ratio and z lp ∈ [0.5, 1].

[0037] The feedback controller C fb has the following structure:

[0038]

[0039] Step two: design the output decoupling matrix GB.

[0040] In this step, the output decoupling matrix GB needs to be designed according to the physical layout of the motion stage actuator of the ultra-precision lithography equipment in Figure 2 , and the specific steps are as follows:

[0041] Step two: the relationship (also known as inverse decoupling relationship) between the logical axis control signal u cor and the actuator control signal u act is:

[0042]

[0043] wherein, l 1y ,l 2y is the distance between actuator 1, actuator 2 and the X axis of the mass center coordinate system of the motion stage system of the ultra-precision lithography equipment, l 1x ,l 2x is the distance between actuator 1, actuator 2 and the Y axis of the mass center coordinate system of the motion stage system of the ultra-precision lithography equipment, l 3y is the distance between actuator 3 and the X axis of the mass center coordinate system of the motion stage system of the ultra-precision lithography equipment.

[0044] Step two: inverse decoupling relationship can be obtained:

[0045]

[0046] Step two: define the output decoupling matrix GB as:

[0047]

[0048] Step three: the reference position signal r and the reference acceleration signal a of the motion stage system P of the ultra-precision lithography equipment are generated by the trajectory generator C r .

[0049] Step four: the reference position signal r and the state observer output signal are subtracted to obtain the position tracking error signal e, and the position tracking error signal e is subjected to the feedback controller C fb to obtain the feedback control signal u fb ; the reference acceleration signal a is subjected to the feedforward controller C ff to obtain the feedforward control signal u ff .

[0050] Step five: the feedforward control signal u ff and the feedback control signal u fb are added to obtain the logical axis control signal u cor , and the logical axis control signal u cor is subjected to the output decoupling matrix GB to obtain the actuator control signal u act .

[0051] Step six: the actuator control signal u act and the actual position signal y are subjected to the virtual actuator to obtain the virtual actuator compensation control signal u va and the virtual actuator output signal y va . The specific steps are as follows:

[0052] Step six one: the state space equation of the motion stage system of the ultra-precision lithography equipment in the nominal case is:

[0053]

[0054] y(t) = Cx(t)

[0055] wherein t is a time variable, A, B and C are known system matrices, x(t) is a system state, and y(t) is a system state output.

[0056] Step six two: when the actuator has output degradation, the state space equation of the motion stage system of the ultra-precision lithography equipment is:

[0057]

[0058] y f (t) = Cx f (t)

[0059] wherein x f (t) is a system state when the actuator has output degradation, y f (t) is a system state output when the actuator has output degradation, and B f (t) is a system matrix when the actuator has output degradation. B f (t) has the following form:

[0060] B f (t) = B·(1-λ(t))

[0061] wherein λ(t) is the degree of actuator output degradation, and 0 < λ(t) ≤ 1. For example, when the degree of actuator output degradation is 10%, λ(t) = 0.1.

[0062] Step six three: the state space equation of the virtual actuator is:

[0063]

[0064] u va (t) = N va (t)(u act (t) - M va x va (t))

[0065] y va (t) = Cx va (t)

[0066] wherein x va (t) is an internal state of the virtual actuator, u va (t) is a compensation control signal output by the virtual actuator, and y va(t) is the virtual actuator state output signal, M va is the virtual actuator state gain, N va (t) is the virtual actuator output gain. N va (t) has the following form:

[0067]

[0068] wherein, is the pseudo-inverse of the solution matrix.

[0069] B * has the following form:

[0070] B * = B f (t) N va (t)

[0071] Step seven: the actuator control signal u act and the virtual actuator compensation control signal u va are added to obtain the compensated control signal u c , the compensated control signal u c passes through the electric control system to obtain the actuator actual output signal F act .

[0072] Step eight: the actuator actual output signal F act passes through the super-precision lithography equipment motion table system P to obtain the actual position signal y.

[0073] Step nine: the actual position signal y and the virtual actuator output signal y va are added to obtain the reconstructed system state signal y f , the reconstructed system state signal y f and the actuator control signal u act pass through the state observer to obtain the state observer output signal , thereby forming a closed-loop control.

[0074] In this step, the state observer has the following structure:

[0075]

[0076] wherein, z(t) is the internal state of the state observer, L is the state observer gain, and N is the state observer output gain.

[0077] Embodiment:

[0078] The following will be combined with Figure 1The technical scheme of the embodiment is illustrated. Assuming that the mass m of the motion table system P of the ultra-precision lithography equipment is 4.5 kg, the servo frequency of the control system is 5 kHz, and the state space equation of the motion table system of the ultra-precision lithography equipment under the nominal condition is:

[0079]

[0080] 1. The feedback controller C is designed as follows fb and the feedforward controller C ff :

[0081] Supposing that the control bandwidth is f bw = 80 Hz, the frequency ratio a = 3, the low-pass filter damping ratio z lp = 0.707, the proportional gain K p = m (2pif bw ) 2 / a = 378994.58, the integral frequency f i = f bw / a 2 = 8.89, the differential frequency f d = f bw / a = 26.67, the low-pass filter cutoff frequency f lp = a f bw = 240, the feedforward gain K ff = 0.9, and the feedback controller should be designed as:

[0082]

[0083] The feedforward controller should be designed as:

[0084] C ff (s) = K ff m s 2 = 0.9 x 4.5 s 2 = 4.05 s 2

[0085] 2. The output decoupling matrix GB is designed as follows:

[0086] As shown in the figure, the coordinates of the three actuators are: Act1(-0.106, 0.106), Act2(0.106, 0.106), and Act3(0, -0.15). After being brought in, the output decoupling matrix can be obtained: Figure 2

[0087]

[0088] 3. The virtual actuator and the state observer are designed as follows:

[0089] The virtual actuator state gain M​va = [-2×18289-3×18289] T Virtual actuator state gain λ(t) takes values ​​of 0.1, 0.2, 0.3, 0.4, and 0.5, representing actuator failure rates of 10%, 20%, 30%, 40%, and 50%, respectively.

[0090]

[0091] Assuming the desired poles of the state equation of the motion stage system of ultra-precision lithography equipment are [-50-100], the gain L of the state observer can be designed as L = [1505000] based on the desired poles.

[0092] 4. Adopt Figure 3 The reference signal shown is used for fault-tolerant control of the motion stage system of the ultra-precision lithography equipment. Figure 4 , Figure 5 The images show a comparison of the position tracking errors of the ultra-precision lithography equipment motion stage system before and after the application of this invention, after different degrees of actuator failure. It can be seen that the method of this invention can significantly improve the closed-loop stability and tracking accuracy of the ultra-precision lithography equipment motion stage system under actuator output degradation conditions, thereby enhancing the reliability and fault tolerance of the ultra-precision lithography equipment motion stage system.

Claims

1. A fault-tolerant control method for actuators in ultra-precision lithography equipment, characterized in that... The method includes the following steps: Step 1: Design the feedforward controller and feedback controller ; Step 2: Design the force decoupling matrix ; Step 3: Trajectory Generator Generating ultra-precision lithography equipment motion stage system Reference position signal and reference acceleration signal ; Step 4: Transfer the reference position signal and state observer output signal The difference is used to obtain the position tracking error signal. Position tracking error signal After feedback controller Obtain feedback control signal Reference acceleration signal After feedforward controller Obtain feedforward control signal ; Step 5: Feedforward Control Signal With feedback control signal The sum is used to obtain the logic axis control signal. Logic axis control signals After the output decoupling matrix Get actuator control signal ; Step Six: Actuator Control Signal and actual location signal The virtual actuator compensation control signal is obtained after the virtual actuator. and virtual actuator output signal The specific steps are as follows: Step 61: The state-space equation of the motion stage system of the ultra-precision lithography equipment under nominal conditions is: in, For time variables, Given the system matrix, For system status, Output the system status; Step 62: When the actuator experiences output degradation, the state-space equation of the ultra-precision lithography equipment motion stage system is: in, This refers to the system state when the actuator output degrades. The system state output is for when the actuator output degrades. The system matrix for actuator output degradation has the following form: in, The degree of actuator output degradation, ; Step 63: The state-space equation of the virtual actuator is: in, This refers to the internal state of the virtual executor. The compensation control signal output by the virtual actuator. Output signals for the virtual actuator status. For the virtual actuator state gain, To increase the output gain of the virtual actuator, It has the following forms: It has the following forms: in, To find the pseudo-inverse of the matrix; Step 7: Actuator Control Signal and virtual actuator compensation control signal The compensated control signal is obtained by adding them together. The compensated control signal The actual output signal of the actuator is obtained through the electronic control system. ; Step 8: Actual output signal of the actuator The motion stage system is equipped with ultra-precision photolithography equipment. Obtain actual position signal ; Step Nine: Actual Location Signal With virtual actuator output signal The summation yields the reconstructed system state signal. Reconstruct system state signals and actuator control signals The output signal of the state observer is obtained after passing through the state observer. This forms a closed-loop control.

2. The fault-tolerant control method for actuators of ultra-precision lithography equipment according to claim 1, characterized in that... In step one, the feedforward controller It has the following structure: in, For the Laplace operator, For feedforward gain, To ensure the quality of the motion stage system for ultra-precision lithography equipment.

3. The fault-tolerant control method for actuators of ultra-precision lithography equipment according to claim 1, characterized in that... In step one, the feedback controller By PID controller and low-pass filter Composition, in which: PID controller It has the following structure: in, For proportional gain, For the integral frequency, The differential frequency, For the Laplace operator; low-pass filter It has the following structure: in, This is the cutoff frequency of the low-pass filter. This refers to the damping ratio of the low-pass filter. Feedback controller It has the following structure: 。 4. The fault-tolerant control method for actuators of ultra-precision lithography equipment according to claim 3, characterized in that... The , , , , , For closed-loop bandwidth, This represents the frequency ratio.

5. The fault-tolerant control method for actuators of ultra-precision lithography equipment according to claim 1, characterized in that... The specific steps of step two are as follows: Step 21: Logic Axis Control Signals With actuator control signals The relationship between them, i.e., the inverse decoupling relationship, is as follows: in, The distance between actuator 1, actuator 2 and the X-axis of the centroid coordinate system of the ultra-precision lithography equipment motion stage system. The distance between actuator 1, actuator 2 and the Y-axis of the centroid coordinate system of the ultra-precision lithography equipment motion stage system. The distance between actuator 3 and the X-axis of the centroid coordinate system of the ultra-precision lithography equipment motion stage system; Step 22: Inversely solve the decoupling relationship to obtain the output decoupling relationship: Steps 2 and 3: Define the output decoupling matrix for: 。 6. The fault-tolerant control method for actuators of ultra-precision lithography equipment according to claim 1, characterized in that... In step nine, the state observer has the following structure: in, For the internal state of the state observer, For the state observer gain, This is the output gain for the state observer.

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