A control method of a spring-assisted variable-gap reluctance motor motion system

Abstract

This invention discloses a control method for a spring-assisted variable air gap reluctance motor motion system, belonging to the field of precision motion control technology. Existing technologies can only achieve fixed air gap control, which is not applicable to the air gap motion control of linear reluctance motors, and only linearize the magnetic flux without linearizing the output force. The steps are as follows: Step 1: Establish a dynamic model of the spring constraint; Step 2: Analyze the mechanical mechanism of the spring assistance; Step 3: Design a feedforward linearization controller; Step 4: Design a feedback controller; Step 5: Implement a composite control strategy. This invention uses mechanical assistance to compress the spring to provide positive stiffness to neutralize the negative stiffness instability of the reluctance motor, and linearizes the output force of the linear reluctance motor through a control algorithm. Simultaneously, feedback control is used to improve the robustness of the system, thereby achieving high-precision, low-power, and high-stability motion control.

Description

Technical Field

[0001] This invention belongs to the field of precision motion control technology, and in particular, it is a control method for a spring-assisted variable air gap reluctance motor motion system. Background Technology

[0002] With the development of semiconductor manufacturing, precision optical inspection, and nanotechnology, high-end equipment places extremely high demands on the accuracy, speed, and acceleration of motion positioning systems. For example, wafer scanning stages in semiconductor lithography machines and microscope motion platforms used for spectral imaging require drive devices capable of achieving micron- or even nanometer-level positioning accuracy. In existing precision motion control systems, commonly used motors include piezoelectric motors and voice coil motors. While piezoelectric motors offer extremely high precision, their stroke is very limited (typically on the micron level), restricting their application range. Voice coil motors, while possessing good linearity and a large stroke, have relatively low force density and experience high heat loss (energy dissipation) during high-thrust operation, which is a disadvantage in precision environments with extremely high thermal stability requirements. In contrast, linear reluctance motors, due to their simple structure, high force density, low energy consumption, and low heat generation, are gradually becoming the ideal choice for driving short-stroke precision motion platforms. Especially in applications requiring high acceleration and low energy dissipation, reluctance motors demonstrate great potential to replace voice coil motors.

[0003] Currently, reluctance motors face severe challenges in practical applications. Firstly, they can only output unidirectional attraction, leading to instability in open-loop control. Furthermore, since the magnetic resistance generated by a reluctance motor is inversely proportional to the square of the air gap (the distance between the mover and stator), the magnetic resistance increases sharply when the mover moves towards the stator (the air gap decreases). Without external constraints, even a small current can easily cause the mover to break equilibrium and quickly pull against the stator (i.e., the "negative stiffness" characteristic), resulting in extreme instability in the open-loop system. Secondly, their inherent strong nonlinearity is evident: the magnetic resistance is directly proportional to the square of the coil current and inversely proportional to the square of the air gap. This dual nonlinearity makes establishing an accurate control model extremely difficult, further increasing the complexity of the control system.

[0004] The invention patent application with publication number CN117792005A, publication date March 29, 2024, entitled "A High-Precision Force Measurement Device and Control Method for a Linear Reluctance Motor," provides a control method based on a voice coil motor, which has the advantage of precise air gap control. However, this patent can only achieve fixed control of the air gap and is not applicable to the air gap motion control of linear reluctance motors. Furthermore, it only linearizes the magnetic flux but not the output force. Summary of the Invention

[0005] The purpose of this invention is to solve the above-mentioned problems existing in the prior art and to provide a control method for a spring-assisted variable air gap reluctance motor motion system.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A spring-assisted variable air gap reluctance motor motion system includes: a linear reluctance motor stator, a linear reluctance motor mover, a compression spring, and a motion platform. The linear reluctance motor stator is connected to the linear reluctance motor mover via the compression spring. The linear reluctance motor mover is connected to the motion platform and is disposed between the compression spring and the motion platform.

[0008] The linear reluctance motor stator includes: a stator housing, a stator coil, a stator electromagnet, and a stator base. The stator electromagnet is of type E. The stator coil is wound around the middle tooth of the stator electromagnet. The stator electromagnet is embedded in the stator housing. The lower end of the stator housing is mounted on the stator base, and the stator base is fixed on the motion platform.

[0009] The linear reluctance motor mover includes: a mover housing and a mover electromagnet. The mover electromagnet is type I and is embedded in the mover housing. The left side of the mover housing is fixedly connected to the stator housing by a compression spring, and the right side of the mover housing is fixedly connected to the motion platform.

[0010] The motion platform includes: a platform base, a guide rail, a platform body, a guide sleeve, and a grating ruler. The guide sleeve is fixed on the platform base, the guide rail slides through the guide sleeve, the platform body is fixedly installed on the guide rail, the guide sleeve is located inside the platform body, the grating ruler is installed on the bottom surface of the guide rail, the stator base is fixed on the platform base, and the right side of the mover housing is fixedly connected to the guide rail.

[0011] A control method for a spring-assisted variable air gap reluctance motor motion system, the method comprising the following steps:

[0012] Step 1: Establish the dynamic model of the spring constraint

[0013] For the system of this invention, the mechanical equations of motion are established according to Newton's second law:

[0014] (1)

[0015] in, For the system displacement, The second derivative of the displacement is the system acceleration. For the mass of the mover, Let be the stiffness coefficient of the compression spring. That is, the elastic force of the compressed spring. , The magnetic resistance generated by the linear reluctance motor can be derived from Maxwell's equations. :

[0016] (2)

[0017] in, Given the vacuum permeability, the cross-sectional area of ​​the core of stator electromagnet 1-3 is... ， The number of turns of stator coil 1-2 is , For coil current, This refers to the size of the air gap.

[0018] Step 2: Analyze the mechanical mechanism of the spring's auxiliary effect.

[0019] In open-loop mode, a constant current is applied to the stator coil. For a system to be stable, that is, for it to satisfy the steady-state condition, then... and This requires a balance between magnetic resistance and elastic force: ;

[0020] Output force of magnetic resistance and elastic force Size, in units The horizontal axis represents displacement. The unit is ;

[0021] According to formula (2), the magnetic resistance will change with displacement. The increase in elasticity is quadratic, while the elastic force increases with displacement. It shows linear growth;

[0022] Therefore, it can be concluded that the system has a critical current. :when > At that time, magnetic resistance Always greater than elasticity At this point, the system cannot be balanced;

[0023] when = At that time, magnetic resistance With elasticity The curves have an intersection point It can remain stable in that position;

[0024] when > At that time, magnetic resistance With elasticity The curve has two intersection points and It can remain stable at these two positions, therefore the critical current This indicates the maximum current value that the system can stably operate in open-loop mode.

[0025] Step 3: Design the feedforward linearization controller

[0026] Set the system's desired output force as The required coil current can be calculated by reverse calculation using formula (2). The designed feedforward control law is:

[0027] (3)

[0028] This step involves real-time displacement measurement. Adjust the coil current The magnitude of this value makes the system exhibit characteristics close to a linear system, thus reducing the actual output magnetic reluctance. With expected output force Maintain consistency.

[0029] Step 4: Design the feedback controller

[0030] This explanation uses a PID controller:

[0031] Set the desired displacement of the system as Based on real-time displacement measurement The displacement error can be calculated. The output of the designed PID controller is:

[0032] (4)

[0033] in The integral of the error, The first derivative of the error. , , These are the proportional gain, integral gain, and derivative gain of the PID controller, respectively.

[0034] Step 5: Implement a composite control strategy

[0035] Based on expected input and displacement Calculation This is then fed into the feedback controller in step four to calculate... Then and displacement The result is obtained by substituting the values ​​into the feedforward controller in step three. ,Will As the coil current of a linear reluctance motor By exciting it, magnetic resistance is generated, causing the linear reluctance motor mover to move in the direction of decreasing air gap, thus realizing the control of the variable air gap reluctance motor motion system based on spring assistance.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] This invention provides a spring-assisted variable air gap reluctance motor motion system, which can solve the problems mentioned in the background:

[0038] Existing technologies can only achieve fixed control of the air gap, and are not suitable for the air gap motion control of linear reluctance motors. Furthermore, they only address the issue of linearizing the magnetic flux but not the output linearization.

[0039] This invention uses mechanical assistance to compress the spring to provide positive stiffness, thereby neutralizing the negative stiffness instability of the reluctance motor. It also uses a control algorithm to linearize the output of the linear reluctance motor and utilizes feedback control to improve the robustness of the system, thus achieving high-precision, low-power, and high-stability motion control.

[0040] Meanwhile, this invention is applicable to precision positioning platforms with micron-level or millimeter-level strokes. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the overall structure of the system of the present invention;

[0042] Figure 2 This is a schematic diagram of the stator structure of the linear reluctance motor in the system of the present invention;

[0043] Figure 3 This is a schematic diagram of the linear reluctance motor mover structure of the system of the present invention;

[0044] Figure 4 This is a schematic diagram of the motion platform structure of the system of the present invention;

[0045] Figure 5 This is a flowchart of the control method of the present invention;

[0046] Figure 6 This is a force-displacement diagram of magnetic resistance and elastic force in this invention;

[0047] Figure 7 This is a control block diagram of the control strategy of the system of the present invention. Detailed Implementation

[0048] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0049] Please see Figure 1-7 The present invention provides a technical solution: a spring-assisted variable air gap reluctance motor motion system, comprising: a linear reluctance motor stator 1, a linear reluctance motor mover 2, a compression spring 3, and a motion platform 4. The linear reluctance motor stator 1 is connected to the linear reluctance motor mover 2 via the compression spring 3. The linear reluctance motor mover 2 is connected to the motion platform 4, and the linear reluctance motor mover 2 is disposed between the compression spring 3 and the motion platform 4.

[0050] The linear reluctance motor stator 1 includes: a stator housing 1-1, a stator coil 1-2, a stator electromagnet 1-3, and a stator base 1-4. The stator electromagnet 1-3 is of type E. The stator coil 1-2 is wound around the middle tooth of the stator electromagnet 1-3. The stator electromagnet 1-3 is embedded in the stator housing 1-1. The lower end of the stator housing 1-1 is mounted on the stator base 1-4. The stator base 1-4 is fixed on the motion platform 4.

[0051] Furthermore: the number of turns of stator coils 1-2 is The current is The cross-sectional area of ​​the iron core of stator electromagnets 1-3 is .

[0052] The linear reluctance motor mover 2 includes: a mover housing 2-1 and a mover electromagnet 2-2. The mover electromagnet 2-2 is of type I and is embedded in the mover housing 2-1. The left side of the mover housing 2-1 is fixedly connected to the stator housing 1-1 by a compression spring 3, thereby forming a magnetic gap g between the mover electromagnet 2-2 and the stator electromagnet 1-3. The right side of the mover housing 2-1 is fixedly connected to the motion platform 4.

[0053] The motion platform 4 includes: a platform base 4-1, a guide rail 4-2, a platform body 4-3, a guide sleeve 4-4, and a grating ruler 4-5. The guide sleeve 4-4 is fixedly mounted on the platform base 4-1. The guide rail 4-2 slides through the guide sleeve 4-4. The platform body 4-3 is fixedly mounted on the guide rail 4-2. The guide sleeve 4-4 is disposed inside the platform body 4-3. The grating ruler 4-5 is mounted on the bottom surface of the guide rail 4-2 and is used to measure the displacement of the motion platform. The stator base 1-4 is fixed on the platform base 4-1, the platform 4-3 and the guide rail 4-2 can complete a single degree of freedom movement in the horizontal direction, and the right side of the mover housing 2-1 is fixedly connected to the guide rail 4-2.

[0054] Furthermore, in the initial state, when no current is applied to the stator coils 1-2, the compression spring 3 is in a compressed state, which will push the linear reluctance motor mover 2 to the maximum air gap position. At this time, the air gap value is... During system operation, current is supplied to stator coils 1-2. A magnetic resistance is generated between the stator electromagnet 1-3 and the mover electromagnet 2-2, attracting the mover 2 of the linear reluctance motor in the direction where the air gap decreases. The displacement is measured by the grating ruler 4-5. Then the air gap is at this time At this time, the elastic force generated by the compressed spring 3 Direction and magnetic resistance on the contrary.

[0055] A control method for a spring-assisted variable air gap reluctance motor motion system, the method comprising the following steps:

[0056] Step 1: Establish the dynamic model of the spring constraint

[0057] For the system of this invention, the mechanical equations of motion are established according to Newton's second law:

[0058] (1)

[0059] in, For the system displacement, The second derivative of the displacement is the system acceleration. For the mass of the mover, Let be the stiffness coefficient of compression spring 3. That is, the elastic force of the compression spring 3 , The magnetic resistance generated by the linear reluctance motor can be derived from Maxwell's equations. :

[0060] (2)

[0061] in, Given the vacuum permeability, the cross-sectional area of ​​the core of stator electromagnet 1-3 is... ， The number of turns of stator coil 1-2 is , For coil current, This refers to the size of the air gap.

[0062] Step 2: Analyze the mechanical mechanism of the spring's auxiliary effect.

[0063] The core function of adding a spring is to change the negative stiffness characteristic of the system and enhance the open-loop stability of the system.

[0064] In open-loop mode, a constant current is applied to stator coils 1-2. For a system to be stable, that is, for it to satisfy the steady-state condition, then... and This requires a balance between magnetic resistance and elastic force: ;

[0065] The equilibrium point can be combined Figure 5 The force-displacement diagrams of magnetic reluctance and elastic force are analyzed, with the vertical axis representing the output force. Size, in units The horizontal axis represents displacement. The unit is The three solid colored lines represent magnetic resistance, and the black dashed lines represent elastic force.

[0066] According to formula (2), the magnetic resistance will change with displacement. The increase in elasticity is quadratic, while the elastic force increases with displacement. It shows linear growth;

[0067] Therefore, it can be concluded that the system has a critical current. :when > At that time, that is Figure 5 When the solid yellow line is in the middle, the magnetic resistance is... Always greater than elasticity At this point, the system cannot be balanced;

[0068] when = At that time, that is Figure 5 When the solid red line is in the middle, the magnetic resistance is... With elasticity The curves have an intersection point It can remain stable in that position;

[0069] when > At that time, that is Figure 5 When the solid blue line is in the middle, the magnetic resistance is... With elasticity The curve has two intersection points and It can remain stable at these two positions, therefore the critical current This indicates the maximum current value that the system can stably operate in open-loop mode.

[0070] The function of a spring: Without a spring, even a small current would cause the mover to become unstable due to its negative stiffness. Introducing stiffness... After that, as long as the control current does not exceed The system then possesses a stable equilibrium point. This allows the controller to adjust its position within a relatively wide safe current range, ensuring stable system operation.

[0071] Step 3: Design the feedforward linearization controller

[0072] To eliminate the high nonlinearity of reluctance motors (magnetic resistance) With coil current It is proportional to the square of the air gap. (inversely proportional to the square of the value), to improve the dynamic characteristics of the reluctance motor motion platform, a feedforward controller is designed to achieve linearization of input and output.

[0073] Set the system's desired output force as The required coil current can be calculated by reverse calculation using formula (2). The designed feedforward control law is:

[0074] (3)

[0075] This step involves real-time displacement measurement. Adjust the coil current The magnitude of this value makes the system exhibit characteristics close to a linear system, thus reducing the actual output magnetic reluctance. With expected output force Maintain consistency.

[0076] Step 4: Design the feedback controller

[0077] Although feedforward control solves most nonlinear problems, model errors still exist. Therefore, a feedback controller is needed to enhance the system's robustness. Feedback controllers include, but are not limited to, PID controllers, state feedback controllers, sliding mode controllers, and robust controllers. The following explanation uses a PID controller:

[0078] Set the desired displacement of the system as Based on real-time displacement measurement The displacement error can be calculated. The output of the designed PID controller is:

[0079] (4)

[0080] in The integral of the error, The first derivative of the error. , , These are the proportional gain, integral gain, and derivative gain of the PID controller, respectively.

[0081] Step 5: Implement a composite control strategy

[0082] like Figure 7 The diagram shown is a control block diagram of the control strategy, based on the desired input. and displacement Calculation This is then fed into the feedback controller in step four to calculate... Then and displacement The result is obtained by substituting the values ​​into the feedforward controller in step three. ,Will As the coil current of a linear reluctance motor Excite it to generate magnetic resistance, which causes the linear reluctance motor mover 2 to move in the direction of decreasing air gap, thus realizing the control of the variable air gap reluctance motor motion system based on spring assistance.

[0083] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

[0084] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0085] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of the equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0086] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A spring-assisted variable air gap reluctance motor motion system, characterized in that: include: The linear reluctance motor stator (1), linear reluctance motor mover (2), compression spring (3) and motion platform (4) are provided. The linear reluctance motor stator (1) is connected to the linear reluctance motor mover (2) through the compression spring (3). The linear reluctance motor mover (2) is connected to the motion platform (4). The linear reluctance motor mover (2) is disposed between the compression spring (3) and the motion platform (4).

2. The spring-assisted variable air gap reluctance motor motion system according to claim 1, characterized in that: The linear reluctance motor stator (1) includes: a stator housing (1-1), a stator coil (1-2), a stator electromagnet (1-3), and a stator base (1-4). The stator electromagnet (1-3) is of type E. The stator coil (1-2) is wound around the middle tooth of the stator electromagnet (1-3). The stator electromagnet (1-3) is embedded in the stator housing (1-1). The lower end of the stator housing (1-1) is mounted on the stator base (1-4). The stator base (1-4) is fixed on the motion platform (4).

3. The spring-assisted variable air gap reluctance motor motion system according to claim 2, characterized in that: The linear reluctance motor mover (2) includes: a mover housing (2-1) and a mover electromagnet (2-2). The mover electromagnet (2-2) is of type I. The mover electromagnet (2-2) is embedded in the mover housing (2-1). The left side of the mover housing (2-1) is fixedly connected to the stator housing (1-1) by a compression spring (3). The right side of the mover housing (2-1) is fixedly connected to the motion platform (4).

4. The spring-assisted variable air gap reluctance motor motion system according to claim 1, characterized in that: The motion platform (4) includes: a platform base (4-1), a guide rail (4-2), a platform body (4-3), a guide sleeve (4-4), and a grating ruler (4-5). The guide sleeve (4-4) is fixed on the platform base (4-1). The guide rail (4-2) slides through the guide sleeve (4-4). The platform body (4-3) is fixedly installed on the guide rail (4-2). The guide sleeve (4-4) is located inside the platform body (4-3). The grating ruler (4-5) is installed on the bottom surface of the guide rail (4-2). The stator base (1-4) is fixed on the platform base (4-1). The right side of the mover housing (2-1) is fixedly connected to the guide rail (4-2).

5. A control method for a spring-assisted variable air gap reluctance motor motion system according to any one of claims 1-4, characterized in that: The method includes the following steps: Step 1: Establish the dynamic model of the spring constraint For the system of this invention, the mechanical equations of motion are established according to Newton's second law: ，（1） in, For the system displacement, The second derivative of the displacement is the system acceleration. For the mass of the mover, The stiffness coefficient of the compression spring (3) is... That is, the elastic force of the compression spring (3) , The magnetic resistance generated by the linear reluctance motor can be derived from Maxwell's equations. : ，（2） in, Given the vacuum permeability, the cross-sectional area of ​​the core of stator electromagnet 1-3 is... ， The number of turns of stator coil 1-2 is , For coil current, This refers to the size of the air gap; Step 2: Analyze the mechanical mechanism of the spring's auxiliary effect. In the open-loop state, a constant current is applied to the stator coils (1-2). For a system to be stable, that is, for it to satisfy the steady-state condition, then... and This requires a balance between magnetic resistance and elastic force: ; Output force of magnetic resistance and elastic force Size, in units The horizontal axis represents displacement. The unit is ; According to formula (2), the magnetic resistance will change with displacement. The increase in elasticity is quadratic, while the elastic force increases with displacement. It shows linear growth; Therefore, it can be concluded that the system has a critical current. :when > At that time, magnetic resistance Always greater than elasticity At this point, the system cannot be balanced; when = At that time, magnetic resistance With elasticity The curves have an intersection point It can remain stable in that position; when > At that time, magnetic resistance With elasticity The curve has two intersection points and It can remain stable at these two positions, therefore the critical current This indicates the maximum current value that the system can stably operate in open-loop mode; Step 3: Design the feedforward linearization controller Set the system's desired output force as The required coil current can be calculated by reverse calculation using formula (2). The designed feedforward control law is: ，（3） This step involves real-time displacement measurement. Adjust the coil current The magnitude of this value makes the system exhibit characteristics close to a linear system, thus reducing the actual output magnetic reluctance. With expected output force Maintain consistency; Step 4: Design the feedback controller This explanation uses a PID controller: Set the desired displacement of the system as Based on real-time displacement measurement The displacement error can be calculated. The output of the designed PID controller is: ，（4） in The integral of the error, The first derivative of the error. , , These are the proportional gain, integral gain, and derivative gain of the PID controller, respectively. Step 5: Implement a composite control strategy Based on expected input and displacement Calculation This is then fed into the feedback controller in step four to calculate... Then and displacement The result is obtained by substituting the values ​​into the feedforward controller in step three. ,Will As the coil current of a linear reluctance motor Excite it to generate magnetic resistance, which causes the linear reluctance motor mover (2) to move in the direction of decreasing air gap, thereby realizing the control of the variable air gap reluctance motor motion system based on spring assistance.

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