Large-size ultrathin silicon wafer multi-wire cutting high-speed wiring tension fractional order anti-interference control method and system

Abstract

The invention discloses a large-size ultrathin silicon wafer multi-wire cutting high-speed wiring tension fractional order anti-interference control method and system, and the method comprises the steps: observing a tension estimation value and a total interference estimation value through an expansion state observer, and calculating a tension error signal according to the tension estimation value and a preset tension control target value; inputting the tension error signal into a fractional order PI controller to obtain a preliminary tension control signal; and compensating the initial tension control signal according to the total interference estimated value to obtain a tension control signal for adjusting the tension of the cutting line. The method has better robustness, response speed and tension stability under the cutting scene of strong disturbance, high nonlinearity and multivariable coupling, accurate tension control is achieved for the large-size ultrathin silicon wafer under the high-speed cutting condition, and the silicon wafer cutting precision and the system reliability are effectively improved.

Description

Technical Field

[0001] This invention relates to the field of precision machining control technology, and in particular to a fractional-order disturbance rejection control method and system for high-speed wiring tension during multi-wire cutting of large-size ultrathin silicon wafers. Background Technology

[0002] Silicon wafers, as the fundamental material for photovoltaic cells and semiconductor chips, are directly affected by the cutting quality during their manufacturing process, which impacts device conversion efficiency, product yield, and subsequent processing costs. With the rapid development of the photovoltaic industry and the continuous increase in wafer size, multi-wire dicing technology has become one of the mainstream processes in silicon wafer processing due to its advantages such as high efficiency, low loss, and strong mass production capabilities. In multi-wire dicing, diamond wires perform multiple simultaneous cuts on the silicon ingot through high-speed reciprocating motion, with the dicing tension playing a crucial role.

[0003] When cutting ordinary silicon ingots, their large thickness provides them with high mechanical strength and stability, effectively resisting various stresses introduced by the steel wires during the cutting process, making them less prone to breakage or deformation. However, cutting large-size ultrathin silicon wafers presents more challenges. "Large size" means a larger wafer area, typically 8-12 inches. During high-speed multi-wire cutting, the long processing lines and large strokes result in high amplitude and wide frequency range disturbances. Furthermore, the uneven distribution of various processing stresses across this large area can lead to warping or even breakage of the silicon wafer. The "ultra-thin" requirement makes the silicon wafer's structure extremely fragile during cutting, drastically reducing its mechanical strength. It becomes highly sensitive to any vibrations, tension fluctuations, or uneven abrasive distribution during the cutting process, easily resulting in edge chipping, microcracks, or even fragmentation. In the high-speed multi-wire cutting of large-size ultrathin silicon wafers, the stability of the cutting line tension directly affects indicators such as wafer thickness consistency, surface roughness, line mark morphology, and control of edge microcracks. Insufficient tension can easily cause the dicing wire to bend, bounce, warp, or break; excessive tension may lead to stress concentration in the silicon ingot or wire breakage. Therefore, the dicing tension must be controlled with high precision and dynamic stability under high-speed changing conditions.

[0004] In traditional multi-wire cutting equipment, wire tension is typically passively adjusted using mechanical structures such as tension hammers and spring guide wheels. Some high-end equipment uses servo motors combined with proportional-integral-derivative (PID) algorithms for active control. While these methods improve control performance to some extent, they often suffer from control lag, insufficient accuracy, and large overshoot when facing complex disturbances (such as changes in material hardness, fluctuations in wire speed, uneven frictional resistance, and chip accumulation). In recent years, disturbance rejection control (ADRC) has been introduced into tension control systems because it does not require precise modeling, can dynamically estimate system disturbances and compensate in real time, and possesses good robustness and adaptability. For example, CN116495570A discloses a yarn tension control method for winding machines based on sliding mode active disturbance rejection control. It employs a second-order extended state observer and sliding mode control approach for yarn tension control. However, this method primarily targets flexible, continuous, lightweight yarns that can withstand a certain amount of tension. Its control logic maintains uniform stress on the yarn during winding by coordinating winding speed and tension sensing. Tension setting mainly revolves around changes in roll diameter, resulting in a slow dynamic response speed. For instance, CN115847786A discloses a method using time-varying fractional-order PID control to output a stable control tension value. While time-varying fractional-order PID enhances adjustment flexibility through fractional-order operators and time-varying parameters, it essentially still relies on error feedback for parameterized compensation. Its disturbance rejection capability is limited, especially during the cutting process when tension is affected by multiple uncertain disturbances such as high-speed reversal, linear speed fluctuations, and material brittleness, leading to a decline in control performance.

[0005] In summary, existing tension control methods are insufficient in terms of robustness and control accuracy to meet the control requirements of high-speed, intelligent, high-speed, and precise multi-wire cutting processes for large-size ultrathin silicon wafers. Summary of the Invention

[0006] Purpose of the invention: The purpose of this invention is to provide a fractional-order disturbance rejection control method and system for high-speed wiring tension of large-size ultrathin silicon wafers through multi-wire cutting, thereby improving the robustness, response speed and tension stability in high-speed multi-wire cutting scenarios of large-size ultrathin silicon wafers under strong disturbances, high nonlinearity and multivariable coupling.

[0007] Technical solution: The method for controlling the fractional-order disturbance rejection of tension in high-speed wiring of large-size ultrathin silicon wafers by multi-wire cutting as described in this invention includes the following steps:

[0008] The actual tension value of the cutting line is detected, and the actual tension value is input into the expansion state observer to observe the tension estimate and the total disturbance estimate.

[0009] The tension error signal is calculated based on the tension estimate and the preset tension control target value;

[0010] The tension error signal is input into a fractional-order PI controller to obtain a preliminary tension control signal;

[0011] The initial tension control signal is compensated based on the total interference estimate to obtain a tension control signal for adjusting the tension of the cutting wire.

[0012] Furthermore, the expressions for the tension estimate and the total disturbance estimate observed by the extended state observer are as follows:

[0013] ;

[0014] ;

[0015] in, It is a tension estimate. This is the total disturbance estimate. yes The derivative, yes The derivative; and It is the observer gain of the extended state observer. It is the disturbance compensation coefficient. It is a tension control signal. This is the actual tension value.

[0016] Furthermore, and Determined according to the bandwidth method as follows: and , This represents the observer bandwidth.

[0017] Furthermore, the transfer function of the fractional-order PI controller is:

[0018] ;

[0019] It is a preliminary tension control signal without disturbance compensation. This is the tension error signal. yes Fractional integral operator, order of which is ; , These are the proportional and integral coefficients, respectively.

[0020] Furthermore, the preliminary tension control signal is compensated based on the total disturbance estimate to obtain a tension control signal that satisfies the dynamic disturbance rejection compensation law:

[0021] ;

[0022] The initial tension control signal output by the fractional-order PI controller is without disturbance compensation. This is the estimated total disturbance. This is the disturbance compensation coefficient.

[0023] Furthermore, after obtaining the tension control signal, the process also includes:

[0024] The tension control signal is processed by the tension swing arm system to obtain the torque control signal. After the torque control signal is converted into a torque current, it is output as a reference current to the current loop of the servo motor, which drives the motor to work and cause the tension swing arm system to reach the set tension.

[0025] Furthermore, the total disturbance includes gravity disturbance terms, inertial disturbance terms, external disturbance terms, and unmodeled dynamic disturbance terms. The unmodeled dynamic disturbance terms include friction, gap, and cutting force variations.

[0026] Furthermore, the actual tension value of the cutting wire is detected in real time by a piezoelectric tension sensor installed on the guide wheel or tension lever.

[0027] The large-size ultrathin silicon wafer multi-wire cutting high-speed trace tension fractional-order disturbance rejection control system of the present invention includes:

[0028] The disturbance estimation unit is used to detect the actual tension value of the cutting line, input the actual tension value into the expansion state observer, and observe the tension estimate and the total disturbance estimate.

[0029] The disturbance compensation unit is used to calculate the tension error signal based on the tension estimate and the preset tension control target value; input the tension error signal into the fractional-order PI controller to obtain the preliminary tension control signal; and compensate the preliminary tension control signal based on the total disturbance estimate to obtain the tension control signal used to adjust the tension of the cutting wire.

[0030] The computer program product of the present invention includes a computer program that, when executed by a processor, implements the fractional-order anti-interference control method for high-speed wiring tension of large-size ultrathin silicon wafer multi-wire cutting.

[0031] Beneficial effects: Compared with the prior art, the advantages of the present invention are: (1) The fractional-order anti-disturbance control method of the present invention realizes high-precision and real-time adjustment of tension during multi-wire cutting, effectively suppressing tension fluctuations caused by process disturbances and changes in system parameters during cutting. (2) The present invention comprehensively utilizes a first-order extended state observer to dynamically estimate the total disturbance of the system, and combines a fractional-order PI to construct a disturbance compensation mechanism, which shows stronger robustness and faster dynamic response speed under conditions of high nonlinearity, strong coupling and uncertain disturbances. Even under high-speed wiring conditions of 3600m / min, the system can still maintain excellent dynamic performance, realize millisecond-level response and precise tension deviation control, effectively avoid the risk of wire breakage, and have real-time wire breakage warning capability. (3) The present invention achieves the continuity and stability of tension control by adjusting the output torque of the servo motor to drive the tension swing arm or guide wheel system, which is significantly better than the control accuracy and stability of the traditional PI control system. (4) This invention is applicable to the ultra-thin slicing process of large-size silicon blanks of 8 to 12 inches (slicing thickness 100μm). It not only improves the tension control level of the cutting line during the cutting process and significantly reduces the breakage rate and the risk of silicon wafer surface damage in high-speed processing, but also further improves the cutting quality and yield of ultra-thin silicon wafers. It has high engineering application value and promotion prospects. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the multi-wire cutting machine of the present invention.

[0033] Figure 2 This is a force diagram of the tension swing arm mechanical structure of the present invention.

[0034] Figure 3 This is a diagram showing the change in the angular velocity of the pendulum during the processing of this invention.

[0035] Figure 4 This is a flowchart of the control method according to an embodiment of the present invention.

[0036] Figure 5 This is a schematic diagram of the control method according to an embodiment of the present invention.

[0037] Figure 6 This is a comparison chart of the fractional-order disturbance rejection and tension control effects of traditional PI control in an embodiment of the present invention. Detailed Implementation

[0038] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0039] This invention is used for real-time adjustment and control of the cutting wire tension during multi-wire silicon wafer dicing, and is especially suitable for large-size ultra-thin silicon wafers. Figure 1The diagram illustrates the operation of a multi-wire cutting machine. Structurally, it mainly consists of key components such as a take-up / feed-out reel, cutting wire, guide wheels, a rocker arm, a tension motor, and spindle rollers. The feed reel is wound with high-strength diamond cutting wire. During operation, the wire is released from the feed reel, passes through the wiring system, and enters the tension rocker arm mechanism. Here, an AC servo motor is used as the tension motor to directly apply tension. The cutting wire winds around the rollers of the tension arm at the feed end and then passes through the guide wheel system to be guided into three cutting spindle rollers. The cutting spindle rollers are driven by a motor to rotate, with the cutting wire arranged in grooves at regular intervals, forming a neatly arranged cutting surface. After passing through the cutting spindle rollers, the cutting wire is finally collected on the take-up reel by a similar take-up system. The take-up and feed-out processes alternate, allowing the entire system to continuously and uniformly cut the material. During processing, the tension state of the cutting wire is adjusted by the tension servo motors on the feed and take-up sides. Figure 2 The diagram illustrates the force distribution of the tension lever's mechanical structure. The upper half of the diagram shows the lever's ideal position before cutting begins or when the system is in a completely steady state, with the lever's rotation angle Φ=0. The tension of the cutting wire is only related to the initial torque of the tension motor. However, during processing, the linear velocities of the take-up and untake-up reels change, making it difficult to synchronize with the speed of the main processing roller. Combined with variations in material hardness, uneven frictional resistance, and chip accumulation, these linear velocity fluctuations cause the lever to deviate from its original position (as shown in the lower half of the diagram) and oscillate repeatedly. This phenomenon is particularly severe during the speed reversal phase. During processing, the lever's angular velocity is highly sensitive to small-amplitude, high-frequency disturbances, allowing it to more quickly reflect changes in the cutting force. Figure 3 The figure shown is a graph of the angular velocity variation of the pendulum. Figure 3 The first and third seconds show the angular velocity curves of the swing arm during the constant speed cutting process of the simulated cutting machine, while the second second shows the angular velocity curve of the swing arm during the speed reversal phase of the cutting machine.

[0040] like Figure 4 The diagram shown is a flowchart of the high-speed wiring tension fractional-order disturbance rejection control method for multi-wire cutting of large-size ultrathin silicon wafers according to the present invention. Figure 5 The diagram shown illustrates the implementation principle of the high-speed wiring tension fractional-order disturbance rejection control method for multi-wire cutting of large-size ultrathin silicon wafers described in this invention. Figure 4 and Figure 5 The steps of the control method described in this invention will be introduced.

[0041] Step 1: Detect the actual tension value of the cutting line, input the actual tension value into the expansion state observer, and observe the tension estimate and the total disturbance estimate.

[0042] Specifically, a piezoelectric tension sensor installed on the guide wheel or tension lever detects the force on the diamond cutting wire in real time and outputs the current tension signal. , It will be used as one of the input signals to the extended state observer to generate estimates of tension changes and total disturbances.

[0043] A first-order extended state observer (ESO) is used to observe the system state and total disturbance, and its expression is:

[0044] ;

[0045] ;

[0046] in, It is an estimate of the system state x, i.e., an estimate of the actual tension. For total disturbance The estimated value, yes The derivative of yes The derivative of the value reflects how the estimated value changes over time and is used to drive... and It can quickly and accurately track the actual tension and total disturbance. These are known disturbance compensation coefficients. It is a tension control signal. It is the actual tension signal collected by the sensor. and This is the observer gain of the ESO, which needs to be adjusted according to system characteristics and performance requirements. The output of the expansion state observer is an estimate of the actual tension change. and estimates of the total disturbance .

[0047] In some alternative embodiments, and Determined according to the bandwidth method as follows: and , This represents the observer bandwidth.

[0048] In some alternative embodiments, the total disturbance includes gravity disturbance terms, inertial disturbance terms, and all unmodeled dynamics (friction, gap, cutting force variations, etc.) and external disturbances.

[0049] Step 2: Calculate the tension error signal based on the estimated tension change value and the preset tension control target value.

[0050] Specifically, tension error signal The expression is: ;

[0051] in It is a preset tension control target value, which is set through a human-machine interface or a host computer system based on the type of material being cut, wire diameter, wire speed, and process parameters. .

[0052] Step 3: Input the tension error signal into the fractional-order PI controller to obtain the preliminary tension control signal.

[0053] Specifically, the fractional-order PI controller responds to the tension error signal. The fractional-order PI controller processes the torque control signal of the servo motor in real time to optimize the control process. The expression for the transfer function of the fractional-order PI controller is:

[0054] ;

[0055] in, It is a preliminary tension control signal without disturbance compensation. yes Fractional integral operator, order of which is ; , These are the proportional and integral coefficients, respectively.

[0056] Step 4: Compensate the preliminary tension control signal based on the total interference estimate to obtain the tension control signal used to adjust the tension of the cutting line.

[0057] Specifically, the estimation of the total disturbance This will be used to compensate the control signal, resulting in a compensated tension control signal. The generation satisfies the dynamic disturbance rejection compensation law:

[0058] ;

[0059] The initial tension control signal output by the fractional-order PI controller is without disturbance compensation. This is the estimated total disturbance. This is the disturbance compensation coefficient.

[0060] Step 5: The tension control signal is processed by the tension lever system to obtain a torque control signal. After torque-current conversion, the torque control signal is output as a reference current to the current loop of the corresponding servo motor, driving the motor to operate and causing the tension lever system to reach the set tension. Since the electromechanical characteristics and disturbance sources of the pay-off and take-up sides are not completely symmetrical, and the take-up and pay-off processes on one side are repeatedly switching, the take-up-side servo motor and the pay-off-side servo motor are controlled separately. That is, the acquisition and processing of signals on both sides are independent. This embodiment uses a single-side servo motor as an example for explanation; the control method for the other side servo motor is the same.

[0061] Specifically, the tension control signal passes through the rocker arm system and torque-current converter sequentially, and the resulting current signal is used as the reference current input to the servo motor current loop. The servo motor outputs the corresponding torque based on the torque control signal T through current loop modulation, driving the tension rocker arm system to adjust the cutting tension, thus achieving real-time, interference-resistant, and precise control.

[0062] In some optional embodiments, the expression for the tension lever system is: ;

[0063] in, For cutting line tension; For the mass of the tension lever; It is the length of the tension rod; It is the distance from the center of gravity of the tension swing arm to the axis of the tension motor. This refers to the output torque of the tension motor; This is the equivalent moment of inertia of the tension lever; It is the angular velocity of the tension pendulum; It is gravitational acceleration.

[0064] In some optional embodiments, the expression for torque-current conversion is: ;

[0065] in, This is the q-axis reference value for the current loop, i.e., the reference current. For torque control signals, This represents the number of pole pairs of the motor. For motor flux linkage.

[0066] Specifically, The input is fed into the current loop PI controller to adjust the d-axis and q-axis voltages of the motor. , Three-phase drive signals are generated through SVPWM modulation. , , The inverter applies electromagnetic torque to the three-phase windings of the PMSM, thereby driving the motor to output the desired electromagnetic torque, which in turn drives the tension swing arm system to reach the set tension.

[0067] Step 6: Adjust the force state of the cutting wire through the tension lever mechanical structure to achieve real-time adjustment of the cutting wire tension, and perform tension detection as a new current actual tension value feedback input to the control system to form a closed loop.

[0068] The method described in this invention will be verified through specific simulation experiments below.

[0069] In the processing of a multi-wire cutting machine, the swing arm angle is a direct physical indicator of the tension change on the cutting line. Tension fluctuations caused by changes in cutting load, line speed fluctuations, etc., can all be reflected in the change of the swing arm angle Φ. The expression for the tension swing arm system shows that the tension magnitude is directly affected by the change in the swing arm angular velocity. During the constant speed cutting phase, the angular velocity change is relatively small, simulating the system's operation under normal and stable conditions. However, during the speed reversal phase, the drastic fluctuation in angular velocity reflects the typical scenario where tension instability is most likely to occur during speed reversal.

[0070] In this embodiment Figure 3 The angular velocity curve of the pendulum is presented, and it is used as the disturbance input condition for the tension pendulum system in this simulation experiment to verify the stability and robustness of the control method under different operating conditions. By applying this angular velocity curve in the simulation, the effects of different control methods can be compared under the same conditions.

[0071] Figure 6 The tension curves of tension control using the fractional-order disturbance rejection control method of this invention and the conventional PI control method are shown. Figure 6 As can be seen, during the commutation process of multi-wire cutting, the acceleration and deceleration introduce significant dynamic disturbances and instantaneous changes in system parameters. Traditional PI control, due to its fixed parameter design and inability to estimate and compensate for external disturbances in real time, results in a lag in response to rapidly changing tension deviations, leading to a significant deviation of the tension curve from the set value of 20N. In contrast, fractional-order disturbance rejection control can estimate the total system disturbance in real time through an extended state observer and enhance the perception and adjustment capabilities of error change trends using a fractional-order controller, enabling the tension to remain stable near the set value during commutation. This demonstrates its superior disturbance rejection, dynamic response capability, and robustness.

[0072] The large-size ultrathin silicon wafer multi-wire cutting high-speed trace tension fractional-order disturbance rejection control system of the present invention includes:

[0073] The disturbance estimation unit is used to detect the actual tension value of the cutting line, input the actual tension value into the expansion state observer, and observe the tension estimate and the total disturbance estimate.

[0074] The disturbance compensation unit is used to calculate the tension error signal based on the tension estimate and the preset tension control target value; input the tension error signal into the fractional-order PI controller to obtain the preliminary tension control signal; and compensate the preliminary tension control signal based on the total disturbance estimate to obtain the tension control signal used to adjust the tension of the cutting wire.

[0075] The computer program product of the present invention includes a computer program that, when executed by a processor, implements the fractional-order anti-interference control method for high-speed wiring tension of large-size ultrathin silicon wafer multi-wire cutting.

Claims

1. A large-size ultra-thin silicon wafer multi-wire saw high-speed walking tension fractional order disturbance control method, characterized in that, The method comprises the following steps: detecting an actual tension value of the cutting line, inputting the actual tension value into an extended state observer, and observing a tension estimation value and a total disturbance estimation value; calculating a tension error signal according to the tension estimation value and a preset tension control target value; inputting the tension error signal into a fractional order PI controller to obtain a preliminary tension control signal; compensating the preliminary tension control signal according to the total disturbance estimation value to obtain a tension control signal for adjusting the tension of the cutting line.

2. The large-size ultra-thin silicon wafer multi-wire saw high-speed walking tension fractional order disturbance control method according to claim 1, characterized in that, An expression of the extended state observer observing the tension estimation value and the total disturbance estimation value is: ； ； wherein is a tension estimate value, is a total interference estimate value, is a derivative of a derivative of ; and are observer gains of an extended state observer, is a disturbance compensation coefficient, is a tension control signal, is an actual tension value. 3.The large-size ultra-thin silicon wafer multi-wire saw high-speed walking tension fractional order disturbance control method according to claim 2, characterized in that, and are determined as and , is the observer bandwidth. 4.The large-size ultra-thin silicon wafer multi-wire saw high-speed walking tension fractional order disturbance control method according to claim 1, wherein, A transfer function of the fractional order PI controller is: ； is a preliminary tension control signal without disturbance compensation, is a tension error signal, is a fractional order integral operator with order ; , are proportional and integral coefficients, respectively.

5. The method of claim 1, wherein the method is characterized by: The tension control signal is obtained by compensating the preliminary tension control signal according to the total disturbance estimation value, and the tension control signal satisfies a dynamic anti-disturbance compensation law: ； a preliminary tension control signal output by the fractional order PI controller without disturbance compensation, a total disturbance estimation value, a disturbance compensation coefficient. 6.The large-size ultra-thin silicon wafer multi-wire saw high-speed walking tension fractional order disturbance control method according to claim 1, wherein, After obtaining the tension control signal, the following steps are further included: The tension control signal is obtained through a tension swing lever system to obtain a torque control signal, and the torque control signal is converted into a reference current after a torque current conversion and is output to a current loop of a servo motor to drive the motor to work and drive the tension swing lever system to reach a set tension. 7.The large-size ultra-thin silicon wafer multi-wire saw high-speed walking tension fractional order disturbance control method according to claim 1, wherein, The total disturbance includes a gravity disturbance term, an inertia disturbance term, an external disturbance term and an unmodeled dynamic disturbance term, and the unmodeled dynamic disturbance term includes friction, clearance and cutting force variation. 8.The large-size ultra-thin silicon wafer multi-wire saw high-speed walking tension fractional order disturbance control method according to claim 1, wherein, The actual tension value of the cutting line is detected in real time by a piezoelectric tension sensor installed on a guide roller or a tension swing lever.

9. A large-size ultra-thin silicon wafer multi-wire saw high-speed walking line tension fractional order disturbance control system, characterized in that, The method comprises the following steps: a disturbance estimation unit for detecting an actual tension value of the cutting line, inputting the actual tension value into an extended state observer, and observing a tension estimation value and a total disturbance estimation value; a disturbance compensation unit for calculating a tension error signal according to the tension estimation value and a preset tension control target value; inputting the tension error signal into a fractional order PI controller to obtain a preliminary tension control signal; compensating the preliminary tension control signal according to the total disturbance estimation value to obtain a tension control signal for adjusting the tension of the cutting line.

10. A computer program product comprising a computer program, characterized in that, The computer program is executed by the processor to implement the large-size ultra-thin silicon wafer multi-wire cutting high-speed walking tension fractional order anti-disturbance control method according to any one of claims 1-8.

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