Control method of linear motor

Abstract

The invention discloses a control method of a linear motor, the linear motor comprises a rotor and at least two sections of stators, and the control method comprises the following steps: obtaining structure parameters of the linear motor, the structure parameters comprising a pole distance, a rotor length, a rotor pole pair number, a stator length, a stator pole pair number and a stator section number; the coupling coefficients of the rotor and all the sections of stators are calculated, the coupling coefficients are related to the stator length, the rotor length and the relative position between the rotor and the stators, and the sum of the coupling coefficients of the rotor and all the sections of stators is equal to 1; and according to the coupling state between the rotor and the stator, power is supplied to the stator according to a power supply strategy, and the power supply strategy comprises the steps of supplying power to any section of stator in response to the fact that the coupling coefficient between the rotor and any section of stator is not zero, and stopping supplying power to the section of stator in response to the fact that the coupling coefficient between the rotor and any section of stator is zero. According to the invention, the general control of the long / short rotor motor can be realized, and the stability of the rotor movement process is improved.

Description

Technical Field

[0001] This application relates to the technical field of motors, and particularly to a control method for a linear motor. Background Art

[0002] Linear motors can be used in mine hoisting, rail traction, shipboard catapults, etc. Due to no transmission mechanism, they have high transmission efficiency. The motor structure can be made into flat, U-shaped, cylindrical, disc-shaped and other structures, and the application scenarios are flexible. For long-stroke and high-power linear motors such as maglev linear motors, shipboard catapult motors, and elevator linear motors, to reduce losses and improve efficiency, the stator side can be made into a segmented structure and spliced into a specific length according to requirements. When powering multiple segments of the stator, a large power supply capacity is required and the cost is high, resulting in a high usage cost of the linear motor. Summary of the Invention

[0003] To solve the deficiencies of the prior art, the following technical solutions are adopted in this application: A control method for a linear motor provided in this application, the linear motor includes a mover and at least two segments of stators, and the control method includes: Obtain the structural parameters of the linear motor, where the structural parameters include pole pitch, mover length, mover pole pairs, stator length, stator pole pairs, and the number of stator segments; Calculate the coupling coefficients between the mover and each segment of the stator. The coupling coefficients are related to the stator length, the mover length, and the relative position between the mover and the stator, and the sum of the coupling coefficients between the mover and each segment of the stator is equal to 1; According to the coupling state between the mover and the stator, supply power to the stator according to a power supply strategy, where the power supply strategy includes: in response to the coupling coefficient between the mover and any segment of the stator being non-zero, supply power to this segment of the stator; in response to the coupling coefficient between the mover and any segment of the stator being zero, stop supplying power to this segment of the stator.

[0004] In summary, according to the above description, a control method for a linear motor provided in this application calculates the coupling coefficients between the mover and each segment of the stator of the linear motor based on the relative length relationship between the mover and the stator and in combination with the position information of the mover, and flexibly adjusts the power supply unit to supply power to the stator segments according to the coupling coefficients between the mover and each segment of the stator of the linear motor, ensuring the continuity of the thrust received by the mover while reducing energy consumption and lowering the operating cost of the linear motor.

[0005] Further, define the number of coupling coefficients to be calculated within one control period as the first quantity, and the first quantity is determined by the maximum number of coupling segments between the mover and the stator; Determine the initial position of the mover relative to the stator, calculate the initial values of the first quantity of coupling coefficients based on the initial position, combine the initial values of the first quantity of coupling coefficients with the power supply strategy, and determine the initial power supply states of each section of the stator; Update the position of the mover relative to the stator, recalculate the first quantity of coupling coefficients after the position update, and re-determine the power supply states of each section of the stator according to the power supply strategy.

[0006] Further, the control method further includes: After updating the position of the mover relative to the stator, determine whether the mover exceeds the stator track of the linear motor. If so, control to stop power supply to the stator; otherwise, continuously update the position of the mover.

[0007] Further, define a first intermediate variable, and the first intermediate variable is represented by the following formula: ; The initial values of the coupling coefficients are obtained through the following formula: When At this time, there is ; When At this time, there is ; In the formula, x s Represents the stator length, x m Represents the mover length; p s Represents the number of stator pole pairs, p m Represents the number of mover pole pairs.

[0008] Further, the coupling coefficient is also related to the motion state of the mover relative to the stator, and the motion state includes one or more of the following types of motion states: The mover enters a certain section of the stator, the mover detaches from a certain section of the stator, the mover is stably coupled with the stator, and the mover is not coupled with the stator.

[0009] Further, define the state switching function of the coupling coefficient, and the state switching function is calculated through the following formula: ; In the formula, p s Represents the number of stator pole pairs, Represents the mover position, which is a time function, and the initial value ; It is the position of the mover's head in different states, and its value is discrete. Its value is related to the stator length, mover length, and the position of the mover at the current moment. The initial value ; represents the slope of the change process; represents the pole pitch.

[0010] Furthermore, the control method further includes: defining a second intermediate variable, and the second intermediate variable is represented by the following formula: ; In the formula, N c represents the first intermediate variable, b is an integer variable, and the integer variable b changes with the change of the mover's position; When the mover enters the stator state, at this time there is , and the coupling coefficient is: ; In the formula, x represents the position of the mover's head, x s represents the stator length, p s represents the number of stator pole pairs, p m represents the number of mover pole pairs, and y(t) represents the state switching function.

[0011] Furthermore, the control method further includes: defining a second intermediate variable, and the second intermediate variable is represented by the following formula: ; In the formula, N c represents the first intermediate variable, b is an integer variable, and the integer variable b changes with the change of the mover's position; When the mover detaches from the stator state, at this time there is , and the coupling coefficient is: ; In the formula, x represents the position of the mover's head, x s represents the stator length, p s represents the number of stator pole pairs, p m represents the number of mover pole pairs, and y(t) represents the state switching function.

[0012] Furthermore, the control method further includes: defining a second intermediate variable, and the second intermediate variable is represented by the following formula: ; In the formula, N c represents the first intermediate variable, b is an integer variable, and the integer variable b changes with the change of the mover's position; When the mover and the stator are in a stable coupling state, there is , and the coupling coefficient is: ; When the mover and the stator are in a non-coupling state, there is , and the coupling coefficient is: ; In the formula, x represents the position of the mover head, x s represents the stator length, p s represents the number of stator pole pairs, p m represents the number of mover pole pairs.

[0013] Furthermore, the control method further includes: In response to the existence of a gap between the stators of the linear motor, when determining the maximum number of coupling segments of the coupling between the mover and the stator, the gap length of the stator is added as an influencing factor, and when determining the position of the head of the mover in different states , the gap length of the stator is added as an influencing factor. Brief Description of the Drawings

[0014] Figure 1 is a flowchart of the steps of a control method for a linear motor provided by an embodiment of the present application; Figure 2 is a flowchart of the steps of calculating the coupling coefficient in a control method for a linear motor provided by an embodiment of the present application; Figure 3 is a flowchart of switching the power supply strategy in a control method for a linear motor provided by an embodiment of the present application; Figure 4 is a waveform diagram of the coupling coefficient and the power supply signal when the mover length is less than the stator length in a control method for a linear motor provided by an embodiment of the present application; Figure 5 is a waveform diagram of the coupling coefficient and the power supply signal when the mover length is equal to the stator length in a control method for a linear motor provided by an embodiment of the present application; Figure 6 is a waveform diagram of the coupling coefficient and the power supply signal when the mover length is greater than the stator length in a control method for a linear motor provided by an embodiment of the present application; Figure 7 is a waveform diagram of the coupling coefficient and the power supply signal when the maximum number of coupling segments between the mover and the stator is three in a control method for a linear motor provided by an embodiment of the present application; Figure 8 is a schematic diagram of the change in the movement speed of the mover in a control method for a linear motor provided by an embodiment of the present application; Figure 9 Schematic diagram of thrust synthesis of the thrust received by the mover in the control method of a linear motor provided by an embodiment of the present application. Specific embodiments

[0015] The present application will be described in detail below in conjunction with the specific embodiments shown in the drawings. However, these embodiments do not limit the present application, and any structural, method, or functional transformation made by those of ordinary skill in the art based on these embodiments is included in the protection scope of the present application.

[0016] To solve the deficiencies of the prior art, the present application provides a control method for a linear motor. The linear motor includes a mover and at least two stator segments. As Figure 1 shown, the control method includes the following steps: Step S11: Obtain the structural parameters of the linear motor. The structural parameters include pole pitch, mover length, mover pole pairs, stator length, stator pole pairs, and stator segment number.

[0017] Step S12: Calculate the coupling coefficients between the mover and each stator segment. The coupling coefficients are related to the stator length, mover length, and the relative position between the mover and the stator. Moreover, the sum of the coupling coefficients between the mover and each stator segment is equal to 1.

[0018] Step S13: Supply power to the stator according to the power supply strategy based on the coupling state between the mover and the stator. Among them, the power supply strategy includes: in response to the coupling coefficient between the mover and any stator segment not being zero, supply power to this stator segment; in response to the coupling coefficient between the mover and any stator segment being zero, stop supplying power to this stator segment.

[0019] Exemplarily, taking the control method applied to a permanent magnet linear motor as an example, the voltage of the permanent magnet linear motor can be expressed by the following formula: (1); In the formula, u represents voltage, and ; R s represents resistance, and ; i represents voltage, and ; represents magnetic flux, and , where represents the amplitude of the permanent magnet magnetic flux, represents the electrical angle; Li represents inductance, where .

[0020] The thrust of the permanent magnet linear motor can be expressed by the following formula: (2); In the formula, f represents the electromagnetic thrust, P represents the mechanical power output of the motor, and v represents the linear velocity of the mover, e a , e b and e c represent the back electromotive force of the stator, and the back electromotive force of the stator .

[0021] Obtain the structural parameters of the motor. The structural parameters include pole pitch, mover length, number of mover pole pairs, stator length, number of stator pole pairs, and number of stator segments. Among the above structural parameters, the mover length is 2 times the product of the pole pitch and the number of mover pole pairs, and the stator length is 2 times the product of the pole pitch and the number of stator pole pairs, so as to ensure seamless connection of the stator in the motor and the on-off state of the power supply switch of the inverter in the motor is in an ideal state.

[0022] Define a linear motor with a short mover as a motor in which the stator length is greater than the mover length, the mover length is greater than zero, and the mover includes at least one pair of magnetic poles. Define a linear motor with a long mover as a motor in which the mover length is greater than M times the stator length and less than M + 1 times the stator length; further, the linear motor with a long mover also includes a motor in which the mover length is equal to M times the stator length. Among them, M belongs to non-zero natural numbers and M is greater than or equal to 1.

[0023] In the linear motor, the stator is segmented. During the traveling process, the mover will be coupled with one or more segments of the stator. The thrust received by the mover is synthesized by superimposing the thrusts of each segment of the stator on the mover. The synthesized thrust can be expressed by the following formula: (3); In the formula, represents the total thrust received by the mover, represents the thrust when the mover is fully coupled with a single segment of the stator, represents the coupling coefficient, represents the maximum number of stator segments coupled by the mover, and satisfies = {1, 2, 3...}.

[0024] Calculate the coupling coefficient between the mover and each segment of the stator according to the position information of the mover. The coupling coefficient characterizes the magnetic field interaction intensity between the mover and a certain segment of the stator. The coupling coefficient is between 0 and 1, and the sum of the coupling coefficients between the mover and each segment of the stator is constantly 1. Based on the change of the motion state of the mover, update and calculate the coupling coefficient in real time, and execute the power supply strategy for the stator segment according to the coupling coefficient to ensure the continuity of the thrust on the mover.

[0025] According to the coupling coefficient between the mover and the stator, if the coupling coefficient between the mover and any stator segment is not zero, the segment is powered to generate effective thrust; if the coupling coefficient between the mover and any stator segment is zero, the power supply to the segment is stopped and the power is cut off to reduce energy consumption. For example, when the head of the mover enters a new segment of the stator, the coupling coefficient of the segment gradually increases from 0, the power supply signal is activated synchronously, and the segment of the stator is powered; when the tail of the mover is separated from the previous segment of the stator, the coupling coefficient between the previous segment and the mover decays to zero, and the power supply is turned off.

[0026] Furthermore, according to the length relationship between the mover and the stator, one or more inverters can be selected to switch the power supply to the stator segments. At least one inverter can be selected for power supply, and at most the number of inverters equal to the total number of stator segments can be selected for power supply. In the embodiment of the present application, the number of inverters is selected to be equal to the maximum number of stator segments coupled to the mover, which reduces the cost and the requirements for power supply performance while meeting the working needs of the linear motor.

[0027] According to the above description, the present application provides a control method for a linear motor, which calculates the coupling coefficient between the mover and each stator segment of the linear motor based on the relative length relationship between the mover and the stator and combines the position information of the mover. According to the coupling coefficient between the mover and each stator segment of the linear motor, the power supply unit is flexibly adjusted to supply power to the stator segment, thereby ensuring the continuity of the thrust exerted on the mover while reducing energy loss and reducing the operating cost of the linear motor.

[0028] As a way to achieve this, Figure 2 As shown, the control method also includes the following steps: Step S121, defining the number of coupling coefficients required to be calculated within a control cycle as a first number, where the first number is determined by the maximum number of coupling sections between the mover and the stator.

[0029] Step S122, determining the initial position of the mover relative to the stator, and calculating a first number of initial values ​​of coupling coefficients based on the initial position, combining the first number of initial values ​​of coupling coefficients with the power supply strategy, and determining an initial power supply state for each stator segment.

[0030] Step S123, updating the position of the mover relative to the stator, recalculating the coupling coefficient of the first quantity after the position is updated, and re-determining the power supply status of each stator section according to the power supply strategy.

[0031] Specifically, the determination of the first number depends on the maximum number of coupling segments between the mover and the stator, that is, the maximum number of stator segments that the mover may be coupled to simultaneously during movement. The maximum number of coupling segments is determined by the length of the mover and the length of a single stator segment. For example, if the length of the mover is twice the length of a single stator segment, the mover can cover up to three stator segments at the same time. By defining the first number, computing resources can be pre-allocated to ensure that only the stator segments that may be coupled are accurately calculated in each control cycle to avoid redundant operations.

[0032] When the motor starts or resets, determine the initial position of the mover relative to the stator. Taking the position of the mover head as the reference point, based on the initial position of the mover, calculate the initial value of the coupling coefficient corresponding to the first quantity. Combine the initial value of the coupling coefficient with the power supply strategy to determine the initial power supply state of each section of the stator. In the power supply strategy, only supply power to the stator sections that have effective coupling with the mover. Through the precise matching of the initial position of the mover and the coupling coefficient, quickly establish a stable thrust output in the motor startup stage, and reduce the mechanical impact on the mover when the motor starts.

[0033] During the movement of the mover, its position changes continuously with time. Based on the new position information of the mover, recalculate the coupling coefficient of the first quantity to ensure that the operation is only performed on the stator sections that may be coupled currently. After completing the calculation of the coupling coefficient, re-determine the power supply state of each section of the stator according to the power supply strategy: immediately energize the newly coupled sections between the mover and the stator, and cut off the power of the separated sections between the mover and the stator in a timely manner. Through continuous position update and power supply adjustment, achieve the maintenance of thrust stability and the optimization of energy efficiency in complex motion trajectories.

[0034] As an implementation method, the control method further includes: after updating the position of the mover relative to the stator, determine whether the mover exceeds the stator track of the linear motor. If so, control to stop power supply to the stator, otherwise, continuously update the position of the mover.

[0035] Specifically, dynamically monitor the position of the mover. If it is detected that the mover exceeds the stator track of the linear motor, at this time, the coupling coefficient between the mover and all stator sections is zero. Stop power supply to the stator sections according to the power supply strategy, so that the mover loses the driving force and gradually stops moving; if the mover is still within the stator track of the linear motor, continue to update the position data of the mover, and dynamically adjust the power supply state of each stator section according to the latest coupling coefficient to ensure continuous thrust. By real-time monitoring the position of the mover and intelligently adjusting the power supply strategy for the stator, the motion state of the mover is adjusted, and the safety and energy saving of the linear motor operation are realized.

[0036] As an implementation method, define a first intermediate variable, and the first intermediate variable is represented by the following formula: (4); In the formula, x s represents the stator length, x m represents the mover length; N c represents the first intermediate variable, and M is a constant.

[0037] As can be seen from the above formula, the maximum number of sections of coupling between the mover and the stator is sections, then calculate simultaneously at any time A coupling coefficient, that is, there are respectively inverters and power supply signals. At this time, there is a coupling coefficient , where n is the maximum number of stator segments coupled by the mover. Set inverter numbers as , , , , The numbers of the stators connected in sequence by , , … , , where , represents the maximum number of stator segments.

[0038] When the mover length x m and the stator length x s satisfy the relationship: or , where . Define the current motor as a long mover motor. During the movement of the mover, take the position of the mover head as the mover position. At the initial moment, . At this time, the coupling coefficient p c ( n ) The initial value is obtained through the following formula: When , there is (5); In the formula, p s represents the number of stator pole pairs, p m represents the number of mover pole pairs.

[0039] When , there is (6); As an implementation, the coupling coefficient is also related to the movement state of the mover relative to the stator. The movement state includes one or more of the following types of movement states: the mover enters a certain stator segment, the mover detaches from a certain stator segment, the mover is stably coupled with the stator, and the mover is not coupled with the stator.

[0040] ​The state of the mover at a certain moment can be a combination of one or more of the above-mentioned motion states. For example, the mover enters a certain stator section and detaches from a certain stator section simultaneously. When the head of the mover starts to enter a certain stator section, the coupling coefficient gradually increases, gradually activating the power supply to this stator section. The mover and this stator section undergo magnetic field coupling to increase the thrust on the mover. When the tail of the mover gradually detaches from a certain stator section, the coupling coefficient gradually decreases, gradually reducing the power supply to this stator section until it is completely cut off, and the magnetic field between the mover and this stator section decays to zero, thereby preventing the magnetic field residue from interfering with the synthesis of the thrust on the mover.

[0041] When the mover completely covers a certain stator section, the two are in a full-coupling state, and the coupling coefficient can reach the maximum value of 1, continuously supplying full power to this stator section to provide a stable maximum thrust and ensure the efficient operation of the motor. When the mover completely detaches from a certain stator section and does not enter the next stator section, the coupling coefficient between the mover and the stator is zero, there is no magnetic field interaction between the mover and the stator, the power supply to this stator section is cut off, reducing the ineffective energy consumption of the motor and reducing electromagnetic interference.

[0042] Accurately obtain the position information of the mover. When the mover is coupled with a certain stator section, power needs to be supplied to this stator section. During the movement of the mover, it is necessary to continuously calculate the coupling coefficient. As a way of implementation, define the state switching function of the coupling coefficient, and the state switching function is obtained by calculating through the following formula: (7); In the formula, p s represents the number of pole pairs of the stator, represents the position of the mover, which is a function of time, and the initial value ; is the position of the head of the mover in different states, and its value is discrete. Its value is related to the stator length, the mover length, and the current position of the mover. The initial value ; represents the slope of the change process; represents the pole pitch.

[0043] During the movement of the mover on the stator track, the state switching function is continuously calculated, and then is used to calculate the coupling coefficient p c ([[]] n ). For example, when the head of the mover enters the next stator section and the tail of the mover detaches from the previous stator section, the thrust gradually decreases, and the thrust gradually increases, and the combined thrust still remains at the thrust required for the movement of the mover. During the movement of the mover, it advances at least by one pole pitch The forward distance is taken as a unit to calculate the coupling coefficient. That is, when the mover is coupled with multiple stator segments, the minimum unit of thrust fluctuation is measured by the distance that the mover advances by one pole pitch. The distance is used to measure the minimum unit of thrust fluctuation.

[0044] As an implementation method, the control method further includes: Defining a second intermediate variable, which is represented by the following formula: (8); In the formula, T emp represents the second intermediate variable, N c represents the first intermediate variable, b is an integer variable, and the integer variable b changes with the change of the mover's position.

[0045] During the forward movement of the mover, the value of the second intermediate variable T emp is related to the current state of the mover. Whenever the second intermediate variable T emp is updated once, coupling coefficients p c ( n ) need to be updated.

[0046] The coupling coefficient p c ( n ) is updated as follows, where n = (1, 2, 3... N c +1).

[0047] When the mover enters the stator state, at this time , the coupling coefficient is represented by the following formula: (9); In the formula, x represents the position of the mover's head, x s represents the stator length, p s represents the number of stator pole pairs, p m represents the number of mover pole pairs, y ( t ) represents the state switching function.

[0048] When the mover is out of the stator state, at this time , the coupling coefficient is represented by the following formula: (10); In the formula, xIndicates the mover head position, x s Indicates the stator length, x m Indicates the mover length, p s Indicates the number of stator pole pairs, p m Indicates the number of mover pole pairs, y ( t ) Indicates the state transition function.

[0049] In the case of stable coupling between the mover and the stator, at this time there is , and the coupling coefficient is expressed by the following formula: (11); In the case of no coupling between the mover and the stator, at this time there is , and the coupling coefficient is expressed by the following formula: (12); In the formula, x Indicates the mover head position, x s Indicates the stator length, x m Indicates the mover length, p s Indicates the number of stator pole pairs, p m Indicates the number of mover pole pairs.

[0050] Furthermore, when the mover length x m and the stator length x s satisfy the relationship: ; Define the current motor as a short mover motor. During the movement of the mover, taking the mover head position as the mover position, set the initial value of the coupling coefficient p c0 (1) = 1, p c0 (2) = 0. At this time, the first intermediate variable N c is 1, and the first intermediate variable N c and the second intermediate variable T emp satisfy: (13); When the mover enters the stator state, the coupling coefficient is expressed by the following formula: (14); In the formula, xIndicates the position of the mover head, x s Indicates the stator length, x m Indicates the mover length, T emp Indicates the second intermediate variable.

[0051] When the mover is detached from the stator, the coupling coefficient is expressed by the following formula: (15); In the formula, x Indicates the position of the mover head, x s Indicates the stator length, x m Indicates the mover length, T emp Indicates the second intermediate variable.

[0052] When the mover is in a stable coupling state with the stator, when the mover state satisfies: (16); At this time, the coupling coefficient is: 、 .

[0053] When the mover is in a non-coupling state with the stator, when the mover position satisfies: (17); At this time, the coupling coefficient is: 、 .

[0054] Furthermore, when the mover is coupled with a certain section of the stator, this section of the stator is in the power supply state, and a power supply signal is sent to trigger the inverter to supply power to the stator section coupled with the mover. The power supply signal is expressed by the following formula: (18); In the formula, s c ( n ) represents the power supply signal, and , p c ( n ) represents the coupling coefficient.

[0055] During the operation of the mover, protection conditions can also be added. If the mover is not within the stator track range, both the coupling coefficient and the power supply signal are zero, and the power supply to the stator is stopped, improving the safety of the motor operation.

[0056] The process of switching the power supply strategy in the control method provided by this application is as shown in Figure 3 Determine the mover lengthx m With the stator length x s , determine whether the linear motor is a long-rotor linear motor or a short-rotor linear motor according to the rotor length and the stator length, and determine the maximum number of stator segments of the linear motor X max . In the initial state of the motor, there is no coupling between the rotor and the stator, and the initial values of the coupling coefficient and the supply signal are both zero. Denote the initial value of the coupling coefficient as p c0 ( n ), and denote the initial value of the supply signal as s c0 ( n ). Denote the number of coupled segments between the rotor and the stator as n, and introduce the first intermediate variable N c . According to formula (4), it can be known that the maximum number of coupled segments n between the rotor and the stator is N c + 1.

[0057] Initialize the loop, configure the integer variable b and the number of coupled segments n to 0, and calculate the rotor position x ( n ) = g ( T emp , N c ), update the rotor position data, and calculate the coupling coefficient p c ( n ) and the supply signal s c ( n ), and control the power supply to the stator segments (the specific calculation processes of the coupling coefficient p c ( n ) and the supply signal s c ( n ) have been described above and will not be described here).

[0058] Increment the number of coupled segments n, and determine whether the number of coupled segments n is greater than or equal to the maximum number of coupled segments between the rotor and the stator N c + 1. Calculate N c + 1 coupling coefficients p c ( n ) and the supply signals s c ( n ) at each moment within a control cycle. If the number of coupled segments n is less than the maximum number of coupled segments between the rotor and the statorN c If it is +1, then return the coupling coefficient after the calculated coupling segment number n is incremented. p c ( n ) and the power supply signal s c ( n ), the coupling segment number n is incremented again, and a judgment is made according to the loop condition. If the coupling segment number n is greater than or equal to the maximum coupling segment number between the mover and the stator N c +1, the integer variable b is incremented, and it is judged whether the mover exceeds the stator track according to the mover position. If the mover position x is greater than or equal to the stator track length X max x s + x m , then the judgment condition is satisfied and the loop ends.

[0059] At this time, the power supply signal s c ( n ) is configured to 0, the power supply to the stator segment ends, and the thrust applied to the mover gradually decays to 0; if it is judged that the mover position has not exceeded the stator track, the loop continues, the mover position is recalculated and the mover position data is continuously updated, and the above loop process is repeated to supply power to the stator segment coupled to the mover and maintain the thrust applied to the mover until the mover position exceeds the stator track and the loop ends.

[0060] According to the above description, when the linear motor is in the working state, every time the mover position continuously changes by one position, the head position of the mover is re-assigned. Every time the head position of the mover is updated, the corresponding coupling coefficients and the power supply signal are calculated respectively to adjust the power supply to the stator segment, thereby forming a complete control cycle.

[0061] As an implementation manner, the control method further includes: in response to a gap existing between the stators of the linear motor, when determining the maximum coupling segment number between the mover and the stator, adding the gap length of the stator as an influencing factor, and when determining the position of the head of the mover in different states, adding the gap length of the stator as an influencing factor.

[0062] Specifically, if there is a gap between stators, the determination of the maximum number of coupled segments needs to consider the compression of the mover's coverage range caused by the gap. When there is a gap, the mover needs to move an additional distance equal to the gap to couple with the new segment of the stator. At this time, the maximum number of coupled segments needs to be recalculated based on the corrected stator interval to avoid misjudgment of coverage caused by the gap and ensure the accurate distribution of power supply to the stators.

[0063] Moreover, the determination of the mover's head position needs to combine the starting coordinates of the stator segment after gap correction. The mover's head position is compared with the coordinates of this corrected stator segment. When the mover crosses the gap and enters a new stator segment, power is supplied to this segment of the stator, thus avoiding mis-triggering of power supply in the gap area and ensuring the effectiveness of magnetic field interaction. At the same time, when the mover's tail leaves the current stator segment, the power supply to the stator is cut off in a timely manner to prevent magnetic field residue from interfering with the work of subsequent segments.

[0064] By incorporating the gap length of the stator as an influencing factor into the power supply strategy, the control method can dynamically adjust the power supply timing to the stator. For example, when the mover leaves the previous stator segment but has not reached the next stator segment, the power supply signal to the next stator segment will be delayed until the mover enters the new stator segment; considering the dead time of the switching device, the controller can supply power to the stator segment that the mover is about to enter in advance or delay the power-off of the stator segment that the mover is about to leave to reduce thrust mutation and improve the performance of the linear motor.

[0065] To further illustrate a control method for a linear motor provided by the present application, the following will be described with different length combinations of stators and movers.

[0066] The moving speed of the mover is set as shown in Table 1 below:

[0067] When the length of the mover x m and the length of the stator x s satisfy: , where h is a constant.

[0068] If the constant h is greater than 0 and less than 1, at this time the linear motor is a short-mover motor, and the structural parameters of the mover and the stator can be configured as shown in Table 2:

[0069] Configure the constant h as 0.8. At this time, the coupling coefficient and the power supply signal waveform of the linear motor are as Figure 4 shown. In the figure, the solid line is the waveform diagram of the coupling coefficient, and the dashed line is the waveform diagram of the power supply signal. Figure 4 The upper part is the waveform diagram of the coupling coefficient and the power supply signal of the odd-numbered stator segments. Figure 4 The lower part is the waveform diagram of the coupling coefficient and the power supply signal of the even-numbered stator segments. FromFigure 4 It can be seen that when the constant h is 0.8, the mover length x m is less than the single-segment stator length x s , and there is a full-coupling stage between the mover and the stator.

[0070] If the constant h is a positive integer, such as , at this time the linear motor is a long-stator motor, and the structural parameters of the mover and the stator can be configured as shown in Table 3:

[0071] Configure the constant h to 1. At this time, the coupling coefficient and the power supply signal waveform of the linear motor are as Figure 5 shown. The solid line in the figure is the coupling coefficient waveform diagram, and the dashed line is the power supply signal waveform diagram. Figure 5 The upper part is the coupling coefficient and the power supply signal waveform diagram of the odd-numbered stator segments. Figure 5 The lower part is the coupling coefficient and the power supply signal waveform diagram of the even-numbered stator segments. It can be seen from Figure 5 that when the constant h is 0.8, the mover length x m is equal to the single-segment stator length x s , and the stator is seamlessly connected. At this time, there are always two power supply signals from the inverters supplying power to the stator segments in the linear motor.

[0072] If the constant h satisfies , at this time the linear motor is a long-mover motor, and the structural parameters of the mover and the stator can be configured as shown in Table 4:

[0073] Configure the constant h to 1.5. At this time, the coupling coefficient and the power supply signal waveform of the linear motor are as Figure 6 shown. The solid line in the figure is the coupling coefficient waveform diagram, and the dashed line is the power supply signal waveform diagram. Figure 6 The upper part is the coupling coefficient and the power supply signal waveform diagram of the (n + 1)-th stator segment. Figure 6 The middle part is the coupling coefficient and the power supply signal waveform diagram of the (n + 2)-th stator segment. Figure 6 The lower part is the coupling coefficient and the power supply signal waveform diagram of the (n + 3)-th stator segment.

[0074] It can be seen from Figure 6 that when the constant h is 1.5, the mover length x m is greater than one stator length x s and less than two stator lengths x s, at this time, at least two of the three inverters in the linear motor supply power to the stator section, and there are two or more power supply signals in the linear motor at any time.

[0075] Furthermore, configure the structural parameters of the linear motor as shown in Table 5 to verify the switching process of the linear motor provided by this application.

[0076]

[0077] At this time, when the mover length x m and the stator length x s satisfy: , the maximum number of coupling segments between the mover and the stator is three. At the same time, three coupling coefficients need to be calculated. The converter 1, converter 2, and converter 3 are respectively connected to , , section of the stator for power supply. The electrical parameters of the linear motor are as follows: the resistance is , the inductance is , the fundamental magnetic flux linkage amplitude is , the mover mass is 300 kg, the ejected cargo is 2000 kg, and the bus voltage is .

[0078] Adopt the vector control of the current . Each section of the stator is equivalent to a three-phase motor, and the mover is pushed in a relay form. The tracking of the mover speed and the stability of the thrust are ensured through continuous closed-loop control.

[0079] The motion speed of the mover is set as shown in Table 6 below:

[0080] At this time, the coupling coefficient and power supply signal waveform of the linear motor are as Figure 7 shown. The solid line in the figure is the waveform diagram of the coupling coefficient, and the dotted line is the waveform diagram of the power supply signal. Take the state switching function to calculate the coupling coefficient . The magnitude of the coupling coefficient determines the thrust magnitude of each section of the stator on the mover, and the sum of the coupling coefficients of each section of the stator is equal to 1, that is, the coupling coefficient exists .

[0081] After the mover of the linear motor throws out the cargo at the highest speed, then the mover returns to realize the ejection process. Exemplarily, such as Figure 8As shown in the lower part, the mover carries goods and moves. When the linear velocity reaches the maximum of 35 m / s at the forward acceleration stage (t = 2.2 s), the goods are thrown out, and it enters the forward braking state, and the speed gradually decreases to 0. Then it enters the reverse acceleration stage, and the mover accelerates back. When the linear velocity reaches the reverse maximum of -30 m / s, it enters the reverse braking state, and finally the return speed decreases to zero. The mover returns to the origin and waits for the next ejection. As Figure 8 As shown in the upper part, during the ejection stage and return stage of the mover, the maximum speed error of the mover does not exceed .

[0082] Exemplarily, a turn-off high-power silicon carbide module is used as the power supply switch contact for the segmented stator. The winding phase current exists in the power supply signal time interval. The single-segment stator power supply consists of 6 silicon carbide modules in parallel in pairs and is connected in series in the three-phase power supply circuit of the motor. The anti-parallel switch module can realize the on / off of the power supply between segments. As Figure 9 shown, the total thrust received by the mover is from , , the electromagnetic force exerted by the segment stator thrust synthesis. According to the maximum mass and acceleration of the mover, the theoretical maximum thrust is .

[0083] According to the above description, a control method for a linear motor provided by the present application calculates the coupling coefficient between the mover and each segment stator of the linear motor based on the relative length relationship between the mover and the stator and combines the position information of the mover. According to the coupling coefficient between the mover and each segment stator of the linear motor, the power supply unit is flexibly adjusted to supply power to the stator segment, realizing the general control of the long / short mover motor, ensuring the continuity of the thrust received by the mover, improving the stability of the mover movement process, reducing the energy loss of the motor, and reducing the operation cost of the linear motor.

[0084] It can be understood that the word "exemplarily" used in this article means "as an example, illustration or explanation". Any embodiment described as "exemplarily" is not necessarily superior to or better than other embodiments and / or does not exclude combining the features of other embodiments. It should be understood that certain features of the present application described in the context of separate embodiments can also be provided in a single embodiment by combination. Conversely, the various features of the present application described in the context of a single embodiment can also be provided separately or by any suitable combination or as any other described embodiment of the present application.

[0085] The above-disclosed are only the preferred embodiments of the present application, but they are not intended to limit the scope of the rights of the present application. Those of ordinary skill in the art can understand that within the spirit and scope of the present application and the appended claims, changes, modifications, substitutions, combinations, and simplifications should all be equivalent replacement methods and still fall within the scope covered by the invention.

Claims

1. A control method for a linear motor, the linear motor comprising a mover and at least two stators, characterized in that: The control method comprises: Acquire structural parameters of the linear motor, wherein the structural parameters include pole pitch, mover length, number of mover pole pairs, stator length, number of stator pole pairs, and number of stator segments; Calculating a coupling coefficient between the mover and each stator segment, wherein the coupling coefficient is related to the stator length, the mover length, and the relative position between the mover and the stator, and the sum of the coupling coefficients between the mover and each stator segment is equal to 1; The stator is powered according to a power supply strategy based on a coupling state between the mover and the stator, wherein the power supply strategy includes: in response to a coupling coefficient between the mover and any section of the stator being not zero, powering the section of the stator; in response to a coupling coefficient between the mover and any section of the stator being zero, stopping powering the section of the stator.

2. The control method of the linear motor according to claim 1, characterized in that: The number of coupling coefficients required to be calculated within the control cycle is defined as a first number, wherein the first number is determined by a maximum number of coupling sections between the mover and the stator; Determine an initial position of the mover relative to the stator, calculate a first number of initial values ​​of coupling coefficients based on the initial position, combine the first number of initial values ​​of coupling coefficients with the power supply strategy, and determine an initial power supply state for each stator segment; The position of the mover relative to the stator is updated, the coupling coefficient of the first quantity after the position update is recalculated, and the power supply state of each stator section is re-determined according to the power supply strategy.

3. The control method of the linear motor according to claim 2, characterized in that: The control method further comprises: After the position of the mover relative to the stator is updated, it is determined whether the mover exceeds the stator track of the linear motor. If so, power supply to the stator is stopped. Otherwise, the position of the mover is continuously updated.

4. The control method of the linear motor according to claim 2, characterized in that: A first intermediate variable is defined, and the first intermediate variable is represented by the following formula: ； The initial value of the coupling coefficient is obtained by the following formula: when Sometimes, there is ； when Sometimes, there is ； In the formula, x s represents the stator length, x m represents the length of the mover; p s represents the number of stator pole pairs, p m Represents the number of rotor pole pairs.

5. The control method of a linear motor according to any one of claims 1 to 4, characterized in that: The coupling coefficient is also related to the motion state of the mover relative to the stator, and the motion state includes one or more of the following types of motion states: The mover enters a certain section of the stator, the mover leaves a certain section of the stator, the mover and the stator are stably coupled, and the mover and the stator are not coupled.

6. The control method of the linear motor according to claim 5, characterized in that: A state switching function of the coupling coefficient is defined, and the state switching function is calculated by the following formula: ； In the formula, p s represents the number of stator pole pairs, Represents the position of the actuator, which is a time function, and the initial value ; It is the position of the head of the mover in different states. Its value is discrete. Its value is related to the stator length, the mover length and the current position of the mover. The initial value ; express The slope of the change process; Indicates the pole distance.

7. The control method of the linear motor according to claim 6, characterized in that: The control method further comprises: A second intermediate variable is defined, and the second intermediate variable is represented by the following formula: ； In the formula, N c represents the first intermediate variable, b is an integer variable, and the integer variable b changes with the change of the position of the mover; When the mover enters the stator state, there is , the coupling coefficient is: ； In the formula, x represents the position of the mover head, x s represents the stator length, p s represents the number of stator pole pairs, p m represents the number of motor pole pairs, y ( t ) represents the state switching function.

8. The control method of the linear motor according to claim 6, characterized in that: The control method further comprises: A second intermediate variable is defined, and the second intermediate variable is represented by the following formula: ； In the formula, N c represents the first intermediate variable, b is an integer variable, and the integer variable b changes with the change of the position of the mover; When the mover is separated from the stator, there is , the coupling coefficient is: ； In the formula, x represents the position of the mover head, x s represents the stator length, p s represents the number of stator pole pairs, p m represents the number of motor pole pairs, y ( t ) represents the state switching function.

9. The control method of the linear motor according to claim 6, characterized in that: The control method further comprises: A second intermediate variable is defined, and the second intermediate variable is represented by the following formula: ； In the formula, N c represents the first intermediate variable, b is an integer variable, and the integer variable b changes with the change of the position of the mover; In the stable coupling state between the mover and the stator, there is , the coupling coefficient is: ； When the mover and stator are not coupled, there is , the coupling coefficient is: ； In the formula, x represents the position of the mover head, x s represents the stator length, p s represents the number of stator pole pairs, p m Represents the number of rotor pole pairs.

10. The control method of the linear motor according to claim 6, characterized in that: The control method further comprises: In response to the presence of a gap between the stators of the linear motor, the gap length of the stator is added as an influencing factor when determining the maximum number of coupling segments between the mover and the stator, and the position of the head of the mover in different states is determined. When , the gap length of the stator is added as an influencing factor.

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