Fault-tolerant control method for actuator of ultra-precise photoetching equipment

Abstract

The invention discloses a fault-tolerant control method for an actuator of ultra-precise photoetching equipment. A track generator Cr generates a reference position signal r and an acceleration signal a; the r and an output signal # imgabs0 # of a state observer are subtracted, and a feedback control signal ufb is obtained through a feedback controller Cfb; a passes through a feedforward controller Cff to obtain a feedforward control signal uff; uff and ufb are added, and an actuator control signal uact is obtained through an output decoupling matrix GB; the uact and the actual position signal y pass through a virtual actuator to obtain a virtual actuator compensation control signal uva and an output signal yva; uact and uva are added to obtain an actual output signal Fact of the actuator through an electric control system; obtaining an actual position signal y by the Fact through a motion platform system P of the ultra-precision photoetching equipment; y and yva are added to obtain a reconstruction system state signal yf, and yf and uact pass through a state observer to obtain a state observer output signal # imgabs1 #. The fault-tolerant control method can play a good fault-tolerant control role when an ultra-precision motion platform system actuator has an output degradation fault.

Description

Technical Field

[0001] The present invention belongs to the field of ultra-precision equipment manufacturing and relates to a fault-tolerant control method for an actuator of ultra-precision lithography equipment. Background Art

[0002] Ultra-precision lithography equipment motion stages play a crucial role in high-end equipment manufacturing, widely used in applications such as semiconductor manufacturing that require extremely high motion accuracy. As the core component of ultra-precision lithography equipment motion stage systems, actuator performance is directly related to the stability and motion accuracy of these systems.

[0003] Generally, a feedforward-feedback composite controller is used in the control system of the motion stage of ultra-precision lithography equipment. This type of controller does not have fault tolerance. In actual operation, the actuator is affected by factors such as complex working environment, mechanical wear and component aging, and various types of faults may occur. Among them, the more common type of fault is output degradation. This type of fault will cause abnormal power output of the motor, resulting in a decrease in the positioning accuracy of the motion stage system of the ultra-precision lithography equipment, leading to a decrease in product quality and yield. It may also cause damage to the mechanical structure of the system, resulting in huge economic losses. Therefore, it is necessary to design a fault-tolerant control method for the output degradation fault of the actuator of the motion stage of ultra-precision lithography equipment to ensure the closed-loop stability and tracking accuracy of the motion stage system of ultra-precision lithography equipment under fault conditions. Summary of the Invention

[0004] To address the issue of decreased closed-loop stability and tracking accuracy when an actuator output degradation failure occurs during the actual operation of an ultra-precision lithography system, the present invention provides a method for fault-tolerant control of actuator faults in ultra-precision lithography equipment. This method provides effective fault-tolerant control when an actuator output degradation failure occurs in an ultra-precision motion system, ensuring closed-loop stability and tracking accuracy, and further improving the reliability and fault tolerance of the ultra-precision motion system.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A fault-tolerant control method for an actuator of ultra-precision lithography equipment comprises the following steps:

[0007] Step 1: Design the feedforward controller C ff and feedback controller C fb ;

[0008] Step 2: Design the output decoupling matrix GB;

[0009] Step 3: Using trajectory generator C r Generate a reference position signal r and a reference acceleration signal a of an ultra-precision lithography equipment motion stage system P;

[0010] Step 4: Combine the reference position signal r and the state observer output signal The position tracking error signal e is obtained by performing the difference, and the position tracking error signal e is passed through the feedback controller C fb Get the feedback control signal u fb ; The reference acceleration signal a passes through the feedforward controller C ff Get the feedforward control signal u ff ;

[0011] Step 5: Feedforward control signal u ff With the feedback control signal u fb Add up to get the logic axis control signal u cor , logical axis control signal u cor The actuator control signal u is obtained through the output decoupling matrix GB act ;

[0012] Step 6: Actuator control signal u act The actual position signal y is passed through 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 control signal u after compensation is obtained by adding 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 ultra-precision lithography equipment motion stage system P;

[0015] Step 9: Actual position signal y and virtual actuator output signal y va Add to get the reconstructed system state signal y f , reconstruct the system state signal y f and actuator control signal u act The state observer output signal is obtained through the state observer Thus forming a closed-loop control.

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

[0017] 1. Without changing the original controller, the present invention adds a reconstruction module based on a virtual actuator and a state observer to the closed-loop control loop. The reconstruction module compensates for the impact of actuator output degradation, ensures closed-loop stability and tracking accuracy, and improves the reliability and fault tolerance of the ultra-precision lithography equipment motion stage.

[0018] 2. Compared with traditional control methods, the present invention can ensure closed-loop stability when the actuator output is degraded, and can limit the tracking error to a certain range, providing satisfactory tracking accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the fault-tolerant control method based on control reconstruction for the ultra-precision lithography equipment motion stage of the present invention.

[0020] Figure 2 Physical layout of the actuators for the motion stage of the ultra-precision lithography equipment of the present invention.

[0021] Figure 3 is the reference signal in the embodiment of the present invention.

[0022] Figure 4 It is the position tracking error signal when the actuator output degrades to different degrees before the method of the present invention is adopted.

[0023] Figure 5 It is the position tracking error signal when the actuator output degrades to different degrees after adopting the method of the present invention. DETAILED DESCRIPTION

[0024] The technical solution of the present invention is further described below with reference to the accompanying drawings, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention that does not depart from the spirit and scope of the technical solution of the present invention should be included in the scope of protection of the present invention.

[0025] The present invention provides a fault-tolerant control method for an actuator of an ultra-precision lithography equipment. Figure 1 As shown, the method includes the following steps:

[0026] Step 1: Design the feedforward controller C ff and 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] Among them, s is the Laplace operator, Kff is the feedforward gain, and m is the mass of the ultra-precision lithography equipment motion stage system.

[0030] In this step, the feedback controller C fb By PID controller C PID and low-pass filter C lp Composition, of which:

[0031] PID controller C PID Has the following structure:

[0032]

[0033] Where, assuming 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 integration frequency and f i =f bw / α 2 , f d is the differential frequency and f d =f bw / α.

[0034] Low-pass filter C lp Has the following structure:

[0035]

[0036] Among them, 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] Feedback controller C fb Has the following structure:

[0038]

[0039] Step 2: Design the output decoupling matrix GB.

[0040] In this step, the output decoupling matrix GB needs to be based on Figure 2 The physical layout of the actuator of the motion stage of the super-precision lithography equipment is designed. The specific steps are as follows:

[0041] Step 21: Logical axis control signal u cor and actuator control signal u act The relationship between (also called inverse decoupling relationship) is:

[0042]

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

[0044] Step 22: Inverse the decoupling relationship to obtain the output decoupling relationship:

[0045]

[0046] Step 2 and 3: Define the output decoupling matrix GB as:

[0047]

[0048] Step 3: Using trajectory generator C r Generate a reference position signal r and a reference acceleration signal a of the ultra-precision lithography equipment motion stage system P.

[0049] Step 4: Combine the reference position signal r and the state observer output signal The position tracking error signal e is obtained by performing the difference, and the position tracking error signal e is passed through the feedback controller C fb Get the feedback control signal u fb ; The reference acceleration signal a passes through the feedforward controller C ff Get the feedforward control signal u ff .

[0050] Step 5: Feedforward control signal u ff With the feedback control signal u fb Add up to get the logic axis control signal u cor , logical axis control signal u cor The actuator control signal u is obtained through the output decoupling matrix GB act .

[0051] Step 6: Actuator control signal u act The actual position signal y is passed through 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 61: Under nominal conditions, the state space equation of the ultra-precision lithography equipment motion stage system is:

[0053]

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

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

[0056] Step 62: When the actuator has output degradation, the state space equation of the ultra-precision lithography equipment motion stage system is:

[0057]

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

[0059] Among them, x f (t) is the system state when the actuator output is degraded, y f (t) is the system state output when the actuator output degrades, B f (t) is the system matrix when the actuator output is degraded. B f (t) has the following form:

[0060] B f (t) = B·(1-λ(t))

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

[0062] Step 63: 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] Among them, x va (t) is the internal state of the virtual actuator, u va (t) is the compensation control signal output by the virtual actuator, 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] in, To find the pseudo-inverse of the matrix.

[0069] B * Has the following form:

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

[0071] Step 7: Actuator control signal u act and virtual actuator compensation control signal u va The control signal u after compensation is obtained by adding c , the compensated control signal u c The actual output signal F of the actuator is obtained through the electronic control system act .

[0072] Step 8: Actual output signal F of the actuator act The actual position signal y is obtained through the ultra-precision lithography equipment motion stage system P.

[0073] Step 9: Actual position signal y and virtual actuator output signal y va Add to get the reconstructed system state signal y f , reconstruct the system state signal y f and actuator control signal u act The state observer output signal is obtained through the state observer Thus forming a closed-loop control.

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

[0075]

[0076] Where 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] Example:

[0078] The following combination Figure 1The technical solution of this embodiment is described. Assuming that the mass m of the ultra-precision lithography equipment motion stage system P is 4.5 kg and the control system servo frequency is 5 kHz, the state space equation of the ultra-precision lithography equipment motion stage system under nominal conditions is:

[0079]

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

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

[0082]

[0083] The feedforward controller should be designed as:

[0084] C ff (s) = K ff ms 2 =0.9×4.5s 2 =4.05s 2

[0085] 2. Design the output decoupling matrix GB as follows:

[0086] like Figure 2 As shown, the coordinates of the three actuators are: Act1 (-0.106, 0.106), Act2 (0.106, 0.106), Act3 (0, -0.15). After substituting them into the output decoupling matrix, we can get:

[0087]

[0088] 3. Design the virtual actuator and state observer as follows:

[0089] Take the virtual actuator state gain Mva =[-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 failures of 10%, 20%, 30%, 40%, and 50%, respectively.

[0090]

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

[0092] 4. Adoption Figure 3 The reference signal shown is used for fault-tolerant control of the motion stage system of ultra-precision lithography equipment. Figure 4 、 Figure 5 The figures show a comparison of the position tracking errors of the ultra-precision lithography equipment motion stage system before and after the implementation of the present invention, after varying degrees of actuator failure. This demonstrates that the method of the present invention significantly improves the closed-loop stability and tracking accuracy of the ultra-precision lithography equipment motion stage system under conditions of actuator output degradation, thereby enhancing the reliability and fault tolerance of the ultra-precision lithography equipment motion stage system.

Claims

1. A fault-tolerant control method for an actuator of an ultra-precision lithography equipment, characterized in that The method comprises the following steps: Step 1: Design the feedforward controller C ff and feedback controller C fb ; Step 2: Design the output decoupling matrix GB; Step 3: Using trajectory generator C r Generate a reference position signal r and a reference acceleration signal a of an ultra-precision lithography equipment motion stage system P; Step 4: Combine the reference position signal r and the state observer output signal The position tracking error signal e is obtained by performing the difference, and the position tracking error signal e is passed through the feedback controller C fb Get the feedback control signal u fb ; The reference acceleration signal a passes through the feedforward controller C ff Get the feedforward control signal u ff ; Step 5: Feedforward control signal u ff With the feedback control signal u fb Add up to get the logic axis control signal u cor , logical axis control signal u cor The actuator control signal u is obtained through the output decoupling matrix GB act ; Step 6: Actuator control signal u act The actual position signal y is passed through the virtual actuator to obtain the virtual actuator compensation control signal u va and the virtual actuator output signal y va ; Step 7: Actuator control signal u act and virtual actuator compensation control signal u va The control signal u after compensation is obtained by adding c , the compensated control signal u c The actual output signal F of the actuator is obtained through the electronic control system act ; Step 8: Actual output signal F of the actuator act The actual position signal y is obtained through the ultra-precision lithography equipment motion stage system P; Step 9: Actual position signal y and virtual actuator output signal y va Add to get the reconstructed system state signal y f , reconstruct the system state signal y f and actuator control signal u act The state observer output signal is obtained through the state observer Thus forming a closed-loop control.

2. The method for controlling the fault tolerance of an actuator of an ultra-precision lithography equipment according to claim 1, characterized in that In step 1, the feedforward controller C ff Has the following structure: C ff (s)=K ff ms 2 Among them, s is the Laplace operator, K ff is the feedforward gain, and m is the mass of the ultra-precision lithography equipment motion stage system.

3. The method for controlling the fault tolerance of an actuator of an ultra-precision lithography equipment according to claim 1, characterized in that In step 1, the feedback controller C fb By PID controller C PID and low-pass filter C lp Composition, of which: PID controller C PID Has the following structure: Among them, K p is the proportional gain, f i is the integration frequency, f d is the differential frequency, s is the Laplace operator; Low-pass filter C lp Has the following structure: Among them, f lp is the low-pass filter cutoff frequency, z lp is the low-pass filter damping ratio; Feedback controller C fb Has the following structure:

4. The method for controlling the fault tolerance of an actuator of an ultra-precision lithography equipment according to claim 3, characterized in that The K p =m(2πf bw ) 2 / α,f i =f bw / α 2 , f d =f bw / α,f lp =αf bw , z lp ∈[0.5,1], f bw is the closed-loop bandwidth, and α is the frequency ratio.

5. The method for controlling the fault tolerance of an actuator of an ultra-precision lithography equipment according to claim 1, characterized in that The specific steps of step 2 are as follows: Step 21: Logical axis control signal u cor and actuator control signal u act The relationship between them, that is, the inverse decoupling relationship is: Among them, l 1y ,l 2y is the distance between actuator 1, actuator 2 and the X-axis of the center of mass coordinate system of the ultra-precision lithography equipment motion stage, l 1x ,l 2x is the distance between actuator 1, actuator 2 and the Y axis of the center of mass coordinate system of the ultra-precision lithography equipment motion stage, l 3y is the distance between actuator 3 and the X-axis of the center-of-mass coordinate system of the ultra-precision lithography equipment motion stage; Step 22: Inverse the decoupling relationship to obtain the output decoupling relationship: Step 2 and 3: Define the output decoupling matrix GB as:

6. The method for controlling the fault tolerance of an actuator of an ultra-precision lithography equipment according to claim 1, characterized in that The specific steps of step six are as follows: Step 61: Under nominal conditions, the state space equation of the ultra-precision lithography equipment motion stage system is: y(t)=Cx(t) Where t is the time variable, A, B, C are known system matrices, x(t) is the system state, and y(t) is the system state output; Step 62: When the actuator has output degradation, the state space equation of the ultra-precision lithography equipment motion stage system is: y f (t)=Cx f (t) Among them, x f (t) is the system state when the actuator output is degraded, y f (t) is the system state output when the actuator output degrades, B f (t) is the system matrix when the actuator output is degraded; Step 63: The state space equation of the virtual actuator is: u va (t)=N va (t)(u act (t)-M va x va (t)) y va (t)=Cx va (t) Among them, x va (t) is the internal state of the virtual actuator, u va (t) is the compensation control signal output by the virtual actuator, 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, B * Has the following form: B * =B f (t)N va (t)。 7. The method for controlling the fault tolerance of an actuator of an ultra-precision lithography equipment according to claim 6, characterized in that The B f (t) has the following form: B f (t)=B·(1-λ(t)) Where λ(t) is the degree of actuator output degradation, 0<λ(t)≤1.

8. The method for controlling the fault tolerance of an actuator of an ultra-precision lithography equipment according to claim 6, characterized in that The N va (t) has the following form: in, To find the pseudo-inverse of the matrix.

9. The method for controlling the fault tolerance of an actuator of an ultra-precision lithography equipment according to claim 1, characterized in that In step nine, the state observer has the following structure: Where z(t) is the internal state of the state observer, L is the state observer gain, and N is the state observer output gain.

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