Method for controlling a linear motor and actuator

Abstract

The application provides a control method of a linear motor and an actuator; in the control method of the linear motor, first, a first current control logic is used to control a stator until a mover stops moving; then, a second current control logic is used to control the stator, a mapping relationship between a Hall edge of a Hall encoder and a corresponding mover displacement is obtained, and a target corresponding relationship between the Hall edge and a theoretical electric angle of the stator is determined according to a target electric angle and the mapping relationship; finally, a current theoretical electric angle of the stator is determined according to a current Hall edge and the target corresponding relationship, and the linear motor is controlled to operate according to the current theoretical electric angle; this control method not only avoids the situation that the linear motor needs to have a certain micro-motion during conventional micro-motion phase searching, and meets the demand that some specific application scenarios do not allow power-on micro-motion; but also reduces the risk of phase searching failure during heavy-load phase searching of the linear motor, thereby improving the phase searching precision of the linear motor, and further improving the control precision of the linear motor.

Description

Technical Field

[0001] This invention relates to the field of motor control technology, and in particular to control methods and actuators for linear motors. Background Technology

[0002] Currently, as the main drive device in linear actuators, linear motor encoders, especially AB-type incremental encoders, typically use micro-motion phase finding to obtain the initial position of the linear motor. Otherwise, the actuator may experience runaway or stalling when controlled. However, certain application scenarios (such as precision machine tools and semiconductor equipment) do not allow for motor micro-motion caused by power-on phase finding, as this would lead to a loss of overall positional accuracy. Furthermore, when the linear motor is under heavy load, micro-motion phase finding carries a certain probability of failure. Therefore, there is an urgent need to develop a Hall effect phase finding correction function for linear motor applications to obtain a precise zero-bias position of the motor after each power-on operation. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a control method and actuator for a linear motor to alleviate the above-mentioned technical problems.

[0004] In a first aspect, embodiments of the present invention provide a control method for a linear motor. The linear motor includes a stator, a mover, and a Hall encoder. The stator has a drive coil, and the mover has a drive magnet. The mover can move linearly under the magnetic drive of the stator. The Hall encoder is used to detect the displacement of the mover relative to the stator. The control method includes: controlling the stator with a first current control logic until the mover stops moving, and taking the position of the mover at this time as the target position; the first current control logic includes controlling the electrical angle of the stator to maintain the target electrical angle; controlling the stator with a second current control logic to obtain the mapping relationship between the Hall edge of the Hall encoder and the corresponding displacement of the mover; the second current control logic includes controlling the stator to move the mover in a first direction to a first mechanical hard limit, and controlling the stator to move the mover in a second direction to a second mechanical hard limit, wherein the first direction and the second direction are opposite; determining the target correspondence between the Hall edge and the theoretical electrical angle of the stator according to the target electrical angle and the mapping relationship; obtaining the current Hall edge of the linear motor, determining the current theoretical electrical angle of the stator according to the current Hall edge and the target correspondence, and controlling the operation of the linear motor according to the current theoretical electrical angle.

[0005] Optionally, the stator is controlled by a second current control logic, including: controlling the stator by the second current control logic so that the mover first moves from the target position in a first direction to a first mechanical hard limit, and then moves from the first mechanical hard limit in a second direction to a second mechanical hard limit.

[0006] Optionally, the stator is controlled by a second current control logic, including: controlling the stator by the second current control logic so that the mover first moves from the target position to the first mechanical hard limit in a first direction, then returns from the first mechanical hard limit to the target position, and moves from the target position to the second mechanical hard limit in a second direction.

[0007] Optionally, obtaining the mapping relationship between the Hall edges of the Hall encoder and the corresponding mover displacement includes: when the mover moves in the second direction to the second mechanical hard limit, obtaining all Hall edges and the mover displacement corresponding to each Hall edge, and generating a mapping relationship based on all Hall edges and the mover displacement corresponding to each Hall edge.

[0008] Optionally, based on the target electrical angle and the mapping relationship, the target correspondence between the Hall edge and the theoretical electrical angle of the stator is determined, including: based on the mapping relationship, determining the stator electrical angle difference between the mover position corresponding to each Hall edge and the target position; based on the stator electrical angle difference and the target electrical angle, determining the theoretical electrical angle of the stator corresponding to each Hall edge, and generating the target correspondence based on the theoretical electrical angle of the stator corresponding to each Hall edge.

[0009] Optionally, the displacement of the mover is the displacement of the mover relative to the target position.

[0010] Optionally, the stator is controlled by a first current control logic, including: controlling the stator by the first current control logic to make the mover start moving from a specified position until the mover stops moving; wherein the specified position is the intermediate position between the first mechanical hard limit and the second mechanical hard limit.

[0011] Optionally, the first current control logic and / or the second current control logic include a control current that increases according to a preset curve until it reaches a target control current; wherein the target control current is used to characterize the maximum allowable current.

[0012] Secondly, embodiments of the present invention also provide an actuator, including a linear motor and a controller; wherein the controller is used to control the linear motor using the control method described in the first aspect.

[0013] Thirdly, embodiments of the present invention also provide a computer-readable storage medium storing a computer program, which, when executed by a processor, performs the steps of the control method described in the first aspect.

[0014] The embodiments of the present invention bring the following beneficial effects:

[0015] This invention provides a control method and actuator for a linear motor. First, a first current control logic controls the stator until the mover stops moving, and the current position of the mover is taken as the target position. Then, a second current control logic controls the stator, obtaining the mapping relationship between the Hall edge of the Hall encoder and the corresponding mover displacement. Next, based on the target electrical angle and the mapping relationship, the target correspondence between the Hall edge and the theoretical electrical angle of the stator is determined. Finally, the current Hall edge of the linear motor is obtained, and the current theoretical electrical angle of the stator is determined based on the current Hall edge and the target correspondence. The linear motor is then controlled to operate based on the current theoretical electrical angle. This control method not only avoids the need for a certain amount of micro-motion in the linear motor during conventional micro-motion phase finding, meeting the requirements of some specific application scenarios where power-on micro-motion is not allowed, but also reduces the risk of phase finding failure when the linear motor is under heavy load, thereby improving the phase finding accuracy of the linear motor and thus improving the control accuracy of the linear motor.

[0016] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained through the structures particularly pointed out in the description and the drawings.

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 A flowchart of a linear motor control method provided in an embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of a discrete signal generated by a Hall encoder according to an embodiment of the present invention;

[0021] Figure 3 This is a schematic diagram of the structure of a controller provided in an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] To facilitate understanding of this embodiment, the embodiments of the present invention will be described in detail below.

[0024] This invention provides a control method for a linear motor. The linear motor includes a stator, a mover, and a Hall encoder. The stator has a drive coil, and the mover has a driving magnet, allowing the mover to move linearly under the magnetic drive of the stator. Furthermore, the Hall encoder is an incremental encoder used to detect the displacement of the mover relative to the stator. In practical applications, the magnetic code disk of the Hall encoder is mounted on the mover and follows its movement. Three Hall switches are fixedly installed (generally on the motor housing), and the Hall switches are arranged at certain electrical angle intervals, corresponding to HALLA, HALLB, and HALLC Hall signals. Specific Hall encoders can be found in existing Hall encoders; this invention will not elaborate further here.

[0025] like Figure 1 As shown, the control method includes the following steps:

[0026] Step S102: The stator is controlled by the first current control logic until the mover stops moving, and the position of the mover at this time is taken as the target position.

[0027] The first current control logic includes a control current that increases according to a preset curve until it reaches a target control current; the target control current is used to characterize the maximum allowable current to ensure that the mover can overcome the load and static friction to move.

[0028] Furthermore, when the stator is controlled by the first current control logic, the control current is generally the q-axis torque current, which is perpendicular to the mover magnetic field and is used to generate driving force. The first current control logic controls the stator's electrical angle to remain at the target electrical angle θ (generally 0°). The mover moves under the drive of the stator magnetic field until the electrical angle of the mover magnetic field is also the target electrical angle θ. The position where the mover stops moving is taken as the target position.

[0029] Furthermore, the stator is controlled by a first current control logic, including: controlling the stator by the first current control logic to make the mover start moving from a specified position until the mover stops moving; wherein, the specified position is the intermediate position between the first mechanical hard limit and the second mechanical hard limit.

[0030] In practical applications, the stroke of the mover in a linear motor is limited, and there are generally two mechanical hard limits, namely the first mechanical hard limit and the second mechanical hard limit. Here, the first mechanical hard limit and the second mechanical hard limit can also be called the negative mechanical hard limit and the positive mechanical hard limit. When the stator is controlled by the first current control logic, in order to avoid the mover being blocked by the mechanical hard limits and thus unable to move to the target position (i.e., the position when the electric angle of the mover's magnetic field reaches the target electric angle), in this embodiment of the invention, the mover starts to move from a designated position. Here, the designated position needs to be far away from the two mechanical hard limits, preferably the middle position between the first mechanical hard limit and the second mechanical hard limit. In some scenarios, the designated position can also be near the middle position, thereby ensuring that the mover stops moving at the target position.

[0031] Step S104: The stator is controlled by the second current control logic to obtain the mapping relationship between the Hall edge of the Hall encoder and the corresponding mover displacement.

[0032] The second current control logic includes a control current that increases according to a preset curve until it reaches a target control current. This target control current characterizes the maximum allowable current, ensuring the mover can overcome load and static friction to move. Furthermore, the second current control logic controls the stator to move the mover in a first direction to a first mechanical hard limit, and controls the stator to move the mover in a second direction to a second mechanical hard limit, the first and second directions being opposite.

[0033] When the stator is controlled using the second current control logic, in one control method, the stator is controlled so that the mover first moves from the target position in a first direction to a first mechanical hard limit, and then moves from the first mechanical hard limit to a second mechanical hard limit in a second direction. In another control method, the stator is controlled using the second current control logic so that the mover first moves from the target position in a first direction to the first mechanical hard limit, then the mover returns from the first mechanical hard limit to the target position, and then moves from the target position to the second mechanical hard limit in a second direction.

[0034] Specifically, during the movement of the mover from the target position in the first direction, the second current control logic maintains the maximum allowable current, the linear motor position is operated in open loop, and the changes in the stator's electrical angle and the mover's position are detected simultaneously. When the change in the mover's position is significantly smaller than the change in the stator's electrical angle, if the absolute value of the difference between the two changes is greater than a preset difference, it is determined that the mover has reached the first mechanical hard limit. Similarly, when the mover moves in the second direction, the second current control logic maintains the maximum allowable current, the linear motor position is operated in open loop, and the changes in the stator's electrical angle and the mover's position are detected simultaneously. When the change in the mover's position is significantly smaller than the change in the stator's electrical angle, it is determined that the mover has reached the second mechanical hard limit.

[0035] Furthermore, when the mover moves in the second direction to the second mechanical hard limit, all Hall edges and the mover displacement corresponding to each Hall edge are acquired, and a mapping relationship is generated based on all Hall edges and the mover displacement corresponding to each Hall edge. Here, the mover displacement is the displacement of the mover relative to the target position, that is, the displacement starting from the target position.

[0036] Specifically, when the mover moves in the second direction to the second mechanical hard limit, the linear motor may have multiple cycles of Hall signals, and the discrete signals generated by the Hall encoder are as follows: Figure 2 As shown in the figure, the horizontal axis S represents the mechanical position of the mover, the vertical axis represents the Hall signal, and the areas between points A and B, C and D, and E and F represent Hall edges. All other vertical points in the figure are Hall edges.

[0037] Each Hall edge corresponds to a specific mover mechanical position. At this time, taking the target position as the starting point, the mover displacement from the target position to the mover mechanical position corresponding to the Hall edge can be determined. Thus, a mapping relationship is generated based on all Hall edges and the mover displacement corresponding to each Hall edge. This mapping relationship is used to characterize the correspondence between the Hall edge and the mover displacement.

[0038] Step S106: Determine the target correspondence between the Hall edge and the theoretical electrical angle of the stator based on the target electrical angle and the mapping relationship.

[0039] Specifically, firstly, based on the mapping relationship, the stator electrical angle difference corresponding to the mover position relative to the target position corresponding to each Hall edge is determined; then, based on the stator electrical angle difference and the target electrical angle, the theoretical electrical angle of the stator corresponding to each Hall edge is determined, and a target correspondence relationship is generated based on the theoretical electrical angle of the stator corresponding to each Hall edge. Thus, in the subsequent control process, the current theoretical electrical angle can be quickly determined based on the current Hall edge of the linear motor and the target correspondence relationship, so as to control the operation of the linear motor according to the current theoretical electrical angle, avoid Hall phase search failure, and improve the control accuracy of the linear motor.

[0040] Step S108: Obtain the current Hall edge of the linear motor, determine the current theoretical electrical angle of the stator based on the correspondence between the current Hall edge and the target, and control the operation of the linear motor based on the current theoretical electrical angle.

[0041] The linear motor control method provided in this invention determines the target correspondence between the Hall edge and the theoretical electrical angle of the stator, and controls the linear motor operation based on the target correspondence and the Hall edge. This not only avoids the need for a certain amount of micro-motion in the linear motor during conventional micro-motion phase finding, thus meeting the requirements of some specific application scenarios where power-on micro-motion is not allowed, but also reduces the risk of phase finding failure when the linear motor is under heavy load, thereby improving the phase finding accuracy of the linear motor and thus improving the control accuracy of the linear motor.

[0042] Based on the above method embodiments, this invention also provides an actuator, including a linear motor and a controller; wherein the linear motor includes a stator, a mover, and a Hall encoder; the stator has a drive coil, the mover has a drive magnet, and the mover can move linearly under the magnetic drive of the stator; the Hall encoder is used to detect the displacement of the mover relative to the stator; and the controller is used to control the linear motor using the above method embodiments. The specific control process can be referred to the above embodiments, and this invention will not be described in detail here.

[0043] The actuator provided in this embodiment of the invention has the same technical features as the linear motor control method provided in the above embodiments, so it can also solve the same technical problems and achieve the same technical effects.

[0044] This invention also provides a controller, including a processor and a memory. The memory stores machine-executable instructions that can be executed by the processor, and the processor executes the machine-executable instructions to implement the above-described linear motor control method.

[0045] See Figure 3 As shown, the controller includes a processor 100 and a memory 101. The memory 101 stores machine-executable instructions that can be executed by the processor 100. The processor 100 executes the machine-executable instructions to implement the control method of the upper linear motor.

[0046] Furthermore, Figure 3 The controller shown also includes a bus 102 and a communication interface 103. The processor 100, the communication interface 103 and the memory 101 are connected via the bus 102.

[0047] The memory 101 may include high-speed random access memory (RAM) and may also include non-volatile memory, such as at least one disk storage device. Communication between this system network element and at least one other network element is achieved through at least one communication interface 103 (which can be wired or wireless), such as the Internet, wide area network, local area network, metropolitan area network, etc. The bus 102 may be an ISA (Industrial Standard Architecture) bus, a PCI (Peripheral Component Interconnect) bus, or an EISA (Enhanced Industry Standard Architecture) bus, etc. These buses can be categorized as address buses, data buses, control buses, etc. For ease of representation, Figure 3 The symbol is represented by a single double-headed arrow, but this does not mean that there is only one bus or one type of bus.

[0048] Processor 100 may be an integrated circuit chip with signal processing capabilities. In implementation, each step of the above method can be completed by the integrated logic circuitry in the hardware of processor 100 or by instructions in software form. Processor 100 may be a general-purpose processor, including a Central Processing Unit (CPU), a Network Processor (NP), etc.; it may also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this invention. The general-purpose processor may be a microprocessor or any conventional processor. The steps of the methods disclosed in the embodiments of this invention can be directly manifested as execution by a hardware decoding processor, or execution by a combination of hardware and software modules in the decoding processor. The software module can reside in a readily available storage medium in the art, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, or registers. This storage medium is located in memory 101, and the processor 100 reads the information from memory 101 and, in conjunction with its hardware, completes the steps of the method described in the foregoing embodiments.

[0049] This embodiment also provides a computer-readable storage medium storing a computer program, which is executed by a processor to perform the above-described linear motor control method.

[0050] The computer program product for the linear motor control method and actuator provided in this embodiment of the invention includes a computer-readable storage medium storing program code. The instructions included in the program code can be used to execute the methods described in the preceding method embodiments. For specific implementation details, please refer to the method embodiments, which will not be repeated here.

[0051] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the system and apparatus described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0052] Furthermore, in the description of the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0053] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a processor-executable, non-volatile, computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0054] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0055] Finally, it should be noted that the above-described embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A control method for a linear motor, the linear motor comprising a stator, a mover, and a Hall encoder, the stator having a drive coil, the mover having a drive magnet, the mover capable of linear motion under the magnetic drive of the stator, and the Hall encoder for detecting the displacement of the mover relative to the stator; characterized in that, The control method includes: The stator is controlled by a first current control logic until the mover stops moving, and the position of the mover at this time is taken as the target position; the first current control logic includes controlling the electrical angle of the stator to maintain the target electrical angle. The stator is controlled by a second current control logic to obtain the mapping relationship between the Hall edge of the Hall encoder and the corresponding displacement of the mover; the second current control logic includes controlling the stator to move the mover in a first direction to a first mechanical hard limit, and controlling the stator to move the mover in a second direction to a second mechanical hard limit, wherein the first direction and the second direction are opposite. Based on the target electrical angle and the mapping relationship, a target correspondence is determined between the Hall edge and the theoretical electrical angle of the stator; based on the mapping relationship, the electrical angle difference between the mover position corresponding to each Hall edge and the stator corresponding to the target position is determined; based on the stator electrical angle difference and the target electrical angle, the theoretical electrical angle of the stator corresponding to each Hall edge is determined, and the target correspondence is generated based on the theoretical electrical angle of the stator corresponding to each Hall edge. The current Hall edge of the linear motor is obtained, the current theoretical electrical angle of the stator is determined according to the correspondence between the current Hall edge and the target, and the linear motor is controlled to run according to the current theoretical electrical angle.

2. The control method according to claim 1, characterized in that, The method of controlling the stator using the second current control logic includes: The stator is controlled by the second current control logic so that the mover first moves from the target position in a first direction to the first mechanical hard limit, and then moves from the first mechanical hard limit in a second direction to the second mechanical hard limit.

3. The control method according to claim 1, characterized in that, The method of controlling the stator using the second current control logic includes: The stator is controlled by the second current control logic so that the mover first moves from the target position in a first direction to the first mechanical hard limit, then returns from the first mechanical hard limit to the target position, and moves from the target position in a second direction to the second mechanical hard limit.

4. The control method according to claim 1, characterized in that, The step of obtaining the mapping relationship between the Hall edge of the Hall encoder and the corresponding mover displacement includes: When the mover moves in the second direction to the second mechanical hard limit, all the Hall edges and the mover displacement corresponding to each Hall edge are obtained, and the mapping relationship is generated according to all the Hall edges and the mover displacement corresponding to each Hall edge.

5. The control method according to claim 1, characterized in that, The displacement of the mover is the displacement of the mover relative to the target position.

6. The control method according to claim 1, characterized in that, The method of controlling the stator using the first current control logic includes: The stator is controlled by the first current control logic so that the mover starts moving from a specified position until the mover stops moving; wherein the specified position is the midpoint between the first mechanical hard limit and the second mechanical hard limit.

7. The control method according to claim 1, characterized in that, The first current control logic and / or the second current control logic include a control current that increases according to a preset curve until it reaches a target control current; wherein the target control current is used to characterize the maximum allowable current.

8. An actuator, characterized in that, It includes a linear motor and a controller; wherein the controller is used to control the linear motor using the control method described in any one of claims 1-7.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores a computer program, which, when executed by a processor, performs the steps of the control method according to any one of claims 1-7.

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