Linear motor control system and control method

Abstract

The present invention provides a linear motor control system and method, the control system comprising a position control module, a speed control module, an electromechanical module and a sensing module; the position control module receives a position control signal and outputs a speed control signal to the speed control module, and then outputs a current control signal; the electromechanical module comprises a current control module, a force control module and a motor, the sensing module obtains a position feedback signal, a speed feedback signal and a current feedback signal fed back by the motor, the position control module adjusts and outputs the speed control signal according to the position feedback signal, and the speed control module adjusts and outputs the current control signal according to the speed feedback signal; the force control module performs force compensation according to the position feedback signal and the current feedback signal and outputs a current compensation signal, and the current control module adjusts and outputs the current control signal according to the current feedback signal and the current compensation signal.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to a linear motor control system and a control method. Background Art

[0002] At present, the production technology and application technology of linear motors and their drivers are in the development stage in industrially developed countries, and as a new feeding method, they show great vitality and have entered the industrial application stage abroad. However, the research and application of linear motors in China are still in their infancy. The three-loop (current loop, speed loop, position loop) control has been maturely applied to servo motors in the industrial field. This control method can be used as a reference and applied to linear motors.

[0003] Therefore, it is necessary to provide a linear motor control system and a control method to solve the above technical problems. Summary of the Invention

[0004] To solve the above technical problems, an embodiment of the present invention provides a linear motor control system, wherein the control system includes a position control module, a speed control module, an electromechanical module and a sensor module;

[0005] The position control module is connected to the speed control module and is used to receive a position control signal and output a speed control signal;

[0006] The speed control module is used to receive the speed control signal and output a current control signal;

[0007] The electromechanical module is connected to the speed control module and includes a current control module, a force control module and a motor, wherein the current control module is used to receive the current control signal and control the position of the motor according to the current control signal;

[0008] The sensing module is connected to the position control module, the speed control module, and the electromechanical module, and is used to obtain the position feedback signal, speed feedback signal, and current feedback signal fed back by the motor. The position control module adjusts and outputs the speed control signal based on the position feedback signal, and the speed control module adjusts and outputs the current control signal based on the speed feedback signal; the force control module performs force compensation based on the position feedback signal and the current feedback signal and outputs a current compensation signal, and the current control module adjusts and outputs the current control signal based on the current feedback signal and the current compensation signal.

[0009] According to one embodiment of the present invention, the sensing module includes a first sensing unit and a second sensing unit. The first sensing unit is connected to the position control module, the speed control module and the motor, and is used to obtain the position feedback signal and obtain the speed feedback signal based on the position feedback signal. The second sensing unit is connected to the current control module and the force control module, and is used to obtain the current feedback signal.

[0010] According to one embodiment of the present invention, the force control module includes a force observation unit and a cogging force unit. The force observation unit is connected to the first sensing unit and the second sensing unit, and is used to obtain the motor constant of the motor based on the current feedback signal and the position feedback signal. The cogging force unit is connected to the first sensing unit, and is used to obtain the cogging force of the motor based on the position feedback signal.

[0011] According to one embodiment of the present invention, the force control module also includes a force compensation unit, which is connected to the force observation unit and the cogging force unit, and is used to perform force compensation based on the motor constant, the cogging force and the preset load of the motor, so that when the difference between the force of the preset load of the motor and the force of the actual load of the motor is less than a preset threshold, the force compensation result is output.

[0012] According to an embodiment of the present invention, the current control module includes a current controller, which is connected to the force control module and is configured to output the current compensation signal according to the force compensation result.

[0013] According to one embodiment of the present invention, the current control module includes a drive unit and a current conversion unit. The drive unit is connected to the speed control module and is used to convert the external voltage into a drive voltage for driving the motor according to the current control signal. The current conversion unit is connected to the drive unit and the motor and is used to obtain the drive current according to the physical parameters of the motor and the drive voltage. When driven by the drive current, the motor outputs the position of the motor according to the actual load of the motor and the motor constant of the motor.

[0014] According to an embodiment of the present invention, the electromechanical module further includes a back electromotive force module, which is connected to the current control module and the motor and is configured to adjust the output drive current according to the position of the motor.

[0015] According to an embodiment of the present invention, the position control module includes a position controller, and the speed control module includes a speed controller.

[0016] According to an embodiment of the present invention, the current controller, the position controller, and the speed controller are all PI controllers.

[0017] To solve the above technical problems, another embodiment of the present invention provides a linear motor control method, the linear motor control method comprising:

[0018] The position controller receives the position control signal and outputs a speed control signal to the speed controller, so that the speed controller outputs a current control signal according to the speed control signal, and the electromechanical module receives the current control signal and controls the motor position of the electromechanical module according to the current control signal;

[0019] The sensor obtains the position feedback signal, speed feedback signal and current feedback signal of the motor position; the position controller adjusts and outputs the speed control signal according to the position feedback signal; and the speed controller adjusts and outputs the current control signal according to the speed feedback signal; the electromechanical module performs force compensation and outputs a current compensation signal according to the position feedback signal and the current feedback signal, and adjusts and outputs the current control signal according to the current feedback signal and the current compensation signal; and the electromechanical module adjusts the motor position of the electromechanical module according to the adjusted current control signal.

[0020] Compared with the prior art, the present invention provides a linear motor control system and control method, in which the position control module adjusts and outputs the speed control signal according to the position feedback signal, and the speed control module adjusts and outputs the current control signal according to the speed feedback signal; the force control module performs force compensation and outputs a current compensation signal according to the position feedback signal and the current feedback signal, and the current control module adjusts and outputs the current control signal according to the current feedback signal and the current compensation signal to achieve precise control of the motor by the linear motor control system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0022] Figure 1 1 is a schematic structural diagram of a linear motor control system according to an embodiment of the present invention.

[0023] Figure 2 1 is a schematic diagram of the principle of a linear motor control system according to an embodiment of the present invention.

[0024] Figure 3It is a schematic diagram of the principle of a force control module of a linear motor control system according to an embodiment of the present invention.

[0025] Figure 4 is a flow chart of a linear motor control method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] The terms "first," "second," and "third," etc., in the specification and claims of the present invention and the accompanying drawings are used to distinguish between different items, not to describe a specific order. Furthermore, the terms "comprise," "comprising," and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or elements is not limited to the listed steps or elements but may optionally include steps or elements not listed, or may optionally include other steps or elements inherent to the process, method, product, or apparatus.

[0028] Please also refer to Figure 1 、 Figure 2 and Figure 3 , Figure 1 1 is a schematic structural diagram of a linear motor control system 1 according to an embodiment of the present invention. Figure 2 1 is a schematic diagram of the principle of a linear motor control system 1 according to an embodiment of the present invention. Figure 3 FIG1 is a schematic diagram showing the principle of a force control module 132 of a linear motor control system 1 according to an embodiment of the present invention. The linear motor control system 1 includes a position control module 11 , a speed control module 12 , an electromechanical module 13 and a sensor module 14 .

[0029] According to one embodiment of the present invention, the position control module 11 includes a position controller 111, and the speed control module 12 includes a speed controller 121. In this embodiment, the position controller 111 and the speed controller 121 are both PI controllers. The position control module 11 is connected to the speed control module 12, and the electromechanical module 13 is connected to the speed control module 12. The position control module 11 receives a position control signal x*, outputs a speed control signal v* to the speed control module 12 through the position controller 111, and the speed controller 121 of the speed control module 12 outputs a current control signal i* based on the speed control signal v*. The electromechanical module 13 is connected to the speed control module 12. In this embodiment, the electromechanical module 13 includes a current control module 131, a force control module 132, and a motor 133. The current control module 131 also includes a current controller 131a, which is connected to the force control module 132. The current controller is also a PI controller. The current control module 131 receives the current control signal i* output by the speed control module 12 and controls the position x of the motor 133 according to the current control signal i*.

[0030] Specifically, the current control module 131 includes a drive unit 131b and a current conversion unit 131c. The drive unit 131b is connected to the speed control module 12. The drive unit 131b converts the external voltage V into a drive voltage V(s) for driving the motor 133 according to the current control signal i*. The current conversion unit 131c is connected to the drive unit 131b and the motor 133, and obtains the drive current i according to the physical parameters of the motor 133 and the drive voltage V(s). In this embodiment, the physical parameters of the motor 133 include motor phase inductance and motor phase resistance. The drive voltage V(s) loaded on both ends of the coil of the motor 133 is:

[0031]

[0032] Wherein, i(s) is the driving current, L is the motor phase inductance of the motor 133 , and R is the motor phase resistance of the motor 133 .

[0033] The motor 133 is driven by the driving current i(s) according to the actual load F of the motor 133. l , the motor constant k of the motor 133 outputs the position x of the motor 133.

[0034] If k c The current gain of the coil current of the motor 133 is converted. The closed-loop current loop function of the PI controller can be expressed as:

[0035]

[0036] i * (s) is the current control signal, i(s) is the driving current, kp and ki are PI controller gains respectively, L is the motor phase inductance of the motor 133, and R is the motor phase resistance of the motor 133.

[0037] When k c 、k p When it is much larger than R, the resistance can be ignored, and formula (2) can be expressed as:

[0038]

[0039] Among them, the parameters of the PI controller can be determined by the attenuation coefficient λ and the natural frequency ω n It is concluded that formula (3) can be expressed as:

[0040]

[0041] In formula (3), the motor constant k is used to represent the relationship between the electromagnetic force and the driving current. Therefore, the relationship between the driving current and the position of the mover of the motor 133 can be expressed as:

[0042]

[0043] Where M, B, and C are the denominator system numbers of the second-order transfer function.

[0044] In another embodiment, the electromechanical module 13 further includes a back-electromotive force module 134 . The back-electromotive force module 134 is connected to the current control module 131 and the motor 133 , and adjusts the output driving current i according to the position x of the motor 133 .

[0045] The sensing module 14 is connected to the position control module 11, the speed control module 12, and the electromechanical module 13. The sensing module 14 can obtain the position feedback signal, speed feedback signal, and current feedback signal fed back by the motor 133. The position control module 11 adjusts and outputs the speed control signal v* based on the position feedback signal, and the speed control module 12 adjusts and outputs the current control signal i* based on the speed feedback signal; the force control module 132 performs force compensation based on the position feedback signal and the current feedback signal and outputs a current compensation signal; the current control module 131 adjusts and outputs the current control signal i* based on the current feedback signal and the current compensation signal, thereby adjusting the position x of the motor 133. In this embodiment, the sensing module 14 includes a first sensing unit 141 and a second sensing unit 142. The first sensing unit 141 is connected to the position control module 11, the speed control module 12 and the motor 133. The first sensing unit 141 can obtain the position feedback signal of the motor 133, and obtain the speed feedback signal based on the position feedback signal, and output the position feedback signal to the position control module 11 and the speed feedback signal to the speed control module 12. The second sensing unit 142 is connected to the current control module 131 and the force control module 132. The second sensing unit 142 can obtain the current feedback signal from the output of the current control module 131, and output the current feedback signal to the current control module 131 and the force control module 132 at the same time.

[0046] The force control module 132 includes a force observation unit 132a and a cogging force unit 132b. The force observation unit 123a is connected to the first sensing unit 141 and the second sensing unit 142, and obtains the motor constant k of the motor 133 based on the position feedback signal fed back by the first sensing unit 141 and the current feedback signal fed back by the second sensing unit 142. The cogging force unit 132b is connected to the first sensing unit 141, and obtains the cogging force of the motor 133 based on the position feedback signal fed back by the first sensing unit 141. In this embodiment, the force control module 132 also includes a force compensation unit 132c, which is connected to the force observation unit 132a and the cogging force unit 132b, and performs force compensation based on the motor constant, the cogging force and the preset load of the motor 133, so that when the difference between the force of the preset load of the motor 133 and the force of the actual load of the motor is less than a preset threshold, the force compensation result is output, and the current controller 131a outputs the current compensation signal based on the force compensation result of the force control module 132.

[0047] Specifically, since the force output deformation is mainly caused by local magnetic field saturation and cogging force, due to magnetic field saturation, the relationship between the force output and current of the motor 133 will show nonlinear characteristics. During the entire stroke and operation of the motor 133, the motor constant k does not remain constant, and the relationship between the back electromotive force and the speed of the motor 133 is also nonlinear. The force control module 132 is used to compensate the current control signal i*. The force observation unit 132a is a function of the position x and the driving current i, which represents the nonlinear characteristics of the motor constant k. The force control module 132 integrates the motor constant k, the cogging force and the force generated by the actual load of the motor 133, and feeds it back to the current controller 131a to adjust the current control signal i*. The force generated by the actual load is equivalent to the product of the driving current i of the motor 133 and the force constant. The cogging force and force output deformation can be calculated by finite element analysis and force compensation is performed by the force control module 132. When the motor 133 enters a stable working state, formula (6) can be expressed as:

[0048]

[0049] Wherein, k1 is the interference coefficient of the motor current change rate on the motor output, k2 is the motor force constant, that is, the ratio of the motor output to the motor current, and s is the Laplace operator. To obtain k1 and k2, the force output generated by the actual load is actually measured and the results of the finite element analysis method and the theoretical calculation are combined. The force generated by the actual load, the cogging force and the force deformation can be estimated by the finite element analysis method. The error in the estimation can be regarded as the error in the parameter definition of the motor 133. The motor constant k can be defined by the following formula (8):

[0050] A(z -1 )x(t)=B(z -1 )i(t)+ε(t) (8)

[0051] Where i(t) is the driving circuit, x is the position of the motor, and equation (8) can be expressed in discrete time form. ε(t) is regarded as the estimation error and other interference coefficients of the linear motor control system 1, and its expression is:

[0052] A(z -1 )=1+a1z -1 +a2z -2 (9)

[0053] B(z -1 )=b0+b1z -1 (10)

[0054] Assuming that a1, a2, b0, and b1 in equations (9) and (10) can be calculated, the motor mass, attenuation coefficient B, and coefficient C of the motor 133 have been estimated, the motor constant k can be calculated.

[0055] Among them, as shown in the following formula (11), a1 a2 b0 b1 can be obtained by the least squares matrix method.

[0056]

[0057] Where, θ=[a1,a2,b0,b1], and ε(t) is the residual. θ can be obtained by recursive least squares and the forgetting factor ρ according to the following steps.

[0058]

[0059] P(t) and G(t) are the covariance matrix and gain adjustment, ρ is a constant value. In this embodiment, ρ is usually between 0.95 and 1. P(t) is an initial value matrix with a limited range, I is an identity matrix, and the emergency braking rule of the motor 133 is as follows:

[0060]

[0061] e is a preset threshold, that is, the difference between the force of the preset load of the motor 133 and the force of the actual load of the motor is less than the preset threshold, and the motor constant k can be obtained. When the motor constant k converges, the force compensation result is output, and the current controller 131a outputs the current compensation signal according to the force compensation result of the force control module 132.

[0062] A linear motor control system 1 of the present invention adjusts and outputs the speed control signal according to the position feedback signal through the position control module 11, and the speed control module 12 adjusts and outputs the current control signal according to the speed feedback signal; the force control module 132 performs force compensation and outputs a current compensation signal according to the position feedback signal and the current feedback signal, and the current control module 131 adjusts and outputs the current control signal according to the current feedback signal and the current compensation signal to achieve precise control of the motor 133 by the linear motor control system 1.

[0063] Furthermore, combining the results of the finite element analysis method with theoretical calculations can reduce the error of the theoretical calculations, and at the same time, the motor constant k of the motor 133 can be obtained without a complicated actual measurement process, thereby achieving precise control of the motor 133.

[0064] See also Figure 4 , Figure 4FIG. 1 is a flow chart of a linear motor control method according to an embodiment of the present invention. The linear motor control method includes:

[0065] Step S101: The position controller receives a position control signal and outputs a speed control signal to the speed controller, so that the speed controller outputs a current control signal according to the speed control signal. The electromechanical module receives the current control signal and controls the motor position of the electromechanical module according to the current control signal.

[0066] Specifically, in step S101, the position controller and the speed controller are both PI controllers. The position controller receives a position control signal x* and outputs a speed control signal v* to the speed controller. The speed controller outputs a current control signal i* based on the speed control signal v*. The electromechanical module controls the position x of the motor based on the current control signal i*.

[0067] In this embodiment, the driving unit of the electromechanical module converts the external voltage V into a driving voltage V(s) for driving the motor 133 according to the current control signal i*. The current conversion unit of the electromechanical module obtains the driving current i according to the physical parameters of the motor 133 and the driving voltage V(s). The motor 133 is driven by the driving current i according to the actual load F of the motor 133. l , the motor constant k of the motor 133 outputs the position x of the motor 133.

[0068] Step S102: The sensor obtains the position feedback signal, speed feedback signal and current feedback signal of the motor position, the position controller adjusts and outputs the speed control signal according to the position feedback signal, and the speed controller adjusts and outputs the current control signal according to the speed feedback signal.

[0069] Furthermore, the sensor can obtain the position feedback signal, speed feedback signal and current feedback signal fed back by the motor. The position controller adjusts and outputs the speed control signal v* according to the position feedback signal, and the speed controller adjusts and outputs the current control signal i* according to the speed feedback signal, thereby realizing position loop and speed loop control.

[0070] Step S103: The electromechanical module performs force compensation based on the position feedback signal and the current feedback signal and outputs a current compensation signal, and adjusts and outputs the current control signal based on the current feedback signal and the current compensation signal. The electromechanical module adjusts the motor position of the electromechanical module based on the adjusted current control signal.

[0071] In step S103, the force control module of the electromechanical module performs force compensation based on the position feedback signal and the current feedback signal and outputs a current compensation signal. The current controller of the electromechanical module adjusts and outputs the current control signal i* based on the current feedback signal and the current compensation signal, thereby adjusting the position x of the motor.

[0072] The force control module obtains the motor constant k of the motor and the cogging force of the motor 133 based on the feedback position feedback signal and the current feedback signal. In this embodiment, the force control module 132 further performs force compensation based on the motor constant k, the cogging force, and the preset load of the motor 133, so that the motor constant k is obtained when the difference between the force of the preset load of the motor 133 and the force of the actual load of the motor is less than a preset threshold. When the motor constant k converges, the force compensation result is output, and the current controller outputs the current compensation signal based on the force compensation result of the force control module.

[0073] A linear motor control method of the present invention, the electromechanical module performs force compensation and outputs a current compensation signal based on the position feedback signal and the current feedback signal, and adjusts and outputs the current control signal based on the current feedback signal and the current compensation signal. The electromechanical module adjusts the motor position of the electromechanical module based on the adjusted current control signal, and applies a three-closed-loop (position loop, speed loop, current loop) control method to the linear motor to achieve precise control of the linear motor.

[0074] Furthermore, the force control module of the electromechanical module performs force compensation and outputs a current compensation signal based on the position feedback signal and the current feedback signal, and the current controller of the electromechanical module adjusts and outputs the current control signal based on the current feedback signal and the current compensation signal, thereby adjusting the position of the motor and improving the accuracy of control of the linear motor.

[0075] The above disclosure is only one embodiment of the present invention and certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A linear motor control system, characterized in that: The control system includes a position control module, a speed control module, an electromechanical module and a sensor module; The position control module is connected to the speed control module and is used to receive a position control signal and output a speed control signal; The speed control module is used to receive the speed control signal and output a current control signal; The electromechanical module is connected to the speed control module and includes a current control module, a force control module and a motor, wherein the current control module is used to receive the current control signal and control the position of the motor according to the current control signal; The sensing module is connected to the position control module, the speed control module, and the electromechanical module, and is used to obtain the position feedback signal, speed feedback signal, and current feedback signal fed back by the motor. The position control module adjusts and outputs the speed control signal according to the position feedback signal, and the speed control module adjusts and outputs the current control signal according to the speed feedback signal. The force control module performs force compensation and outputs a current compensation signal according to the position feedback signal and the current feedback signal, and the current control module adjusts and outputs the current control signal according to the current feedback signal and the current compensation signal. The sensing module includes a first sensing unit and a second sensing unit. The first sensing unit is connected to the position control module, the speed control module, and the motor, and is used to obtain the position feedback signal and obtain the speed feedback signal based on the position feedback signal. The second sensing unit is connected to the current control module and the force control module, and is used to obtain the current feedback signal. The force control module includes a force observation unit and a cogging force unit. The force observation unit is connected to the first sensing unit and the second sensing unit and is used to obtain the motor constant of the motor according to the current feedback signal and the position feedback signal. The cogging force unit is connected to the first sensing unit and is used to obtain the cogging force of the motor according to the position feedback signal. The force control module also includes a force compensation unit, which is connected to the force observation unit and the cogging force unit, and is used to perform force compensation based on the motor constant, the cogging force and the preset load of the motor, so that when the difference between the force of the preset load of the motor and the force of the actual load of the motor is less than a preset threshold, the force compensation result is output.

2. The linear motor control system according to claim 1, characterized in that: The current control module includes a current controller, which is connected to the force control module and is configured to output the current compensation signal according to the force compensation result.

3. The linear motor control system according to claim 1, characterized in that: The current control module includes a drive unit and a current conversion unit. The drive unit is connected to the speed control module and is used to convert the external voltage into a drive voltage for driving the motor according to the current control signal. The current conversion unit is connected to the drive unit and the motor and is used to obtain the drive current according to the physical parameters of the motor and the drive voltage. When driven by the drive current, the motor outputs the position of the motor according to the actual load of the motor and the motor constant of the motor.

4. The linear motor control system according to claim 3, characterized in that: The electromechanical module further includes a back electromotive force module, which is connected to the current control module and the motor and is used to adjust the output of the driving current according to the position of the motor.

5. The linear motor control system according to claim 2, characterized in that: The position control module includes a position controller, and the speed control module includes a speed controller.

6. The linear motor control system according to claim 5, characterized in that: The current controller, the position controller, and the speed controller are all PI controllers.

7. A linear motor control method, characterized in that: The linear motor control method comprises: The position controller receives the position control signal and outputs a speed control signal to the speed controller, so that the speed controller outputs a current control signal according to the speed control signal, and the electromechanical module receives the current control signal and controls the motor position of the electromechanical module according to the current control signal; The sensor obtains a position feedback signal, a speed feedback signal, and a current feedback signal of the motor position; the position controller adjusts and outputs the speed control signal based on the position feedback signal; and the speed controller adjusts and outputs the current control signal based on the speed feedback signal; the electromechanical module performs force compensation and outputs a current compensation signal based on the position feedback signal and the current feedback signal, and adjusts and outputs the current control signal based on the current feedback signal and the current compensation signal; and the electromechanical module adjusts the motor position of the electromechanical module based on the adjusted current control signal; The method further comprises: Obtaining the position feedback signal, and obtaining the speed feedback signal based on the position feedback signal, obtaining the current feedback signal; Obtaining a motor constant of the motor according to the current feedback signal and the position feedback signal, obtaining the cogging force of the motor according to the position feedback signal; Force compensation is performed according to the motor constant, the cogging force, and the preset load of the motor, so that a force compensation result is output when a difference between the force of the preset load of the motor and the force of the actual load of the motor is less than a preset threshold.

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