A control method for a linear motor

Abstract

The present application discloses a control method for a linear motor. The linear motor includes a mover and at least two stator segments. The control method includes: obtaining 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; calculating the coupling coefficients between the mover and each stator segment, where the coupling coefficients are related to the stator length, 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; and powering the stator according to the coupling state between the mover and 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 stator segment being non-zero, powering the stator segment, and in response to the coupling coefficient between the mover and any stator segment being zero, stopping power supply to the stator segment. The present application can achieve general control of long / short mover motors and improve the stability of the mover movement process.

Description

Technical Field

[0001] The present 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 applied to occasions such as mine hoisting, rail traction, shipboard catapulting, etc. Due to the absence of a transmission mechanism, they have high transmission efficiency, and the motor structure can be made into flat, U-shaped, cylindrical, disc-shaped and other structures, with flexible application scenarios. For long-stroke and high-power linear motors such as maglev linear motors, shipboard catapult motors, and elevator linear motors, in order 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, resulting in high costs and high usage costs for linear motors. Summary of the Invention

[0003] In order to solve the deficiencies of the prior art, the present application adopts the following technical solutions:

[0004] A control method for a linear motor provided by the present application, the linear motor includes a mover and at least two segments of stators, and the control method includes:

[0005] 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 segments;

[0006] 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;

[0007] 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 not being zero, supply power to this segment of the stator, and 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.

[0008] In summary, according to the above description, a control method for a linear motor provided by the present 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.

[0009] 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;

[0010] 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, and combine the initial values of the first quantity of coupling coefficients with the power supply strategy to determine the initial power supply state of each segment of the stator;

[0011] 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 state of each segment of the stator according to the power supply strategy.

[0012] Further, the control method further includes:

[0013] 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.

[0014] Further, define a first intermediate variable, and the first intermediate variable is represented by the following formula:

[0015] ;

[0016] The initial value of the coupling coefficient is obtained through the following formula:

[0017] When , there is

[0018] ;

[0019] When , there is

[0020] ;

[0021] 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.

[0022] 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:

[0023] The mover enters a certain segment of the stator, the mover detaches from a certain segment of the stator, the mover is stably coupled with the stator, and the mover is not coupled with the stator.

[0024] Further, define a state switching function of the coupling coefficient, and the state switching function is obtained by calculating through the following formula:

[0025] ;

[0026] In the formula, p s represents the number of stator pole pairs, represents the mover position, which is a function of time, and the initial value ; is the position of the mover's head in different states, and its value is discrete. Its value is related to the stator length, the mover length, and the mover's current position, and the initial value ; represents the slope of the change process; represents the pole pitch.

[0027] Further, the control method further includes:

[0028] Define a second intermediate variable, and the second intermediate variable is represented by the following formula:

[0029] ;

[0030] 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 position;

[0031] When the mover enters the stator state, at this time there is , and the coupling coefficient is:

[0032] ;

[0033] In the formula, x represents the mover head position, 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.

[0034] Further, the control method further includes:

[0035] Define a second intermediate variable, and the second intermediate variable is represented by the following formula:

[0036] ;

[0037] 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 position;

[0038] When the mover is detached from the stator, there is , and the coupling coefficient is:

[0039] ;

[0040] 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, and y(t) represents the state switching function.

[0041] Furthermore, the control method further includes:

[0042] Define a second intermediate variable, and the second intermediate variable is represented by the following formula:

[0043] ;

[0044] 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 position;

[0045] When the mover and the stator are in a stable coupling state, there is , and the coupling coefficient is:

[0046] ;

[0047] When the mover and the stator are in a non-coupling state, there is , and the coupling coefficient is:

[0048] ;

[0049] 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.

[0050] Furthermore, the control method further includes:

[0051] 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 stators, the gap length of the stators 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 stators is added as an influencing factor. Description of the Drawings

[0052] Figure 1 is the step flow chart of the control method of the linear motor provided by an embodiment of the present application;

[0053] Figure 2 Flow chart of steps for calculating coupling coefficient in a control method of a linear motor provided by an embodiment of the present application;

[0054] Figure 3 Flow block diagram of switching power supply strategy in a control method of a linear motor provided by an embodiment of the present application;

[0055] Figure 4 Waveform diagram of coupling coefficient and power supply signal when the mover length is less than the stator length in a control method of a linear motor provided by an embodiment of the present application;

[0056] Figure 5 Waveform diagram of coupling coefficient and power supply signal when the mover length is equal to the stator length in a control method of a linear motor provided by an embodiment of the present application;

[0057] Figure 6 Waveform diagram of coupling coefficient and power supply signal when the mover length is greater than the stator length in a control method of a linear motor provided by an embodiment of the present application;

[0058] Figure 7 Waveform diagram of coupling coefficient and power supply signal when the maximum number of coupling segments between the mover and the stator is three in a control method of a linear motor provided by an embodiment of the present application;

[0059] Figure 8 Schematic diagram of the change in the moving speed of the mover in a control method of a linear motor provided by an embodiment of the present application;

[0060] Figure 9 Schematic diagram of thrust synthesis of the thrust received by the mover in a control method of a linear motor provided by an embodiment of the present application. Specific embodiments

[0061] The present application will be described in detail below in conjunction with the specific embodiments shown in the drawings, but these embodiments do not limit the present application. 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.

[0062] 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:

[0063] Step S11: Obtain the structural parameters of the linear 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.

[0064] 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.

[0065] Step S13: According to the coupling state between the mover and the stator, supply power to the stator in accordance with the power supply strategy. The power supply strategy includes: in response to the coupling coefficient between the mover and any stator segment being non-zero, supply power to that stator segment; in response to the coupling coefficient between the mover and any stator segment being zero, stop supplying power to that stator segment.

[0066] 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:

[0067] (1);

[0068] In the formula, u represents voltage, and ; R s represents resistance, and ; i represents voltage, and ; represents magnetic flux linkage, and , where represents the amplitude of the permanent magnet flux linkage, represents the electrical angle; Li represents inductance, where .

[0069] The thrust of the permanent magnet linear motor can be expressed by the following formula:

[0070] (2);

[0071] In the formula, f represents the electromagnetic thrust, P represents the mechanical power output of the motor, 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 .

[0072] Obtain the structural parameters of the motor. The structural parameters include the pole pitch, mover length, mover pole pairs, stator length, stator pole pairs, and stator segments. Among the above structural parameters, the mover length is twice the product of the pole pitch and the mover pole pairs, and the stator length is twice the product of the pole pitch and the stator pole pairs 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.

[0073] A linear motor with a stator length greater than the mover length, a mover length greater than zero, and the mover having at least a pair of magnetic poles is defined as a linear motor with a short mover. A linear motor with a mover length greater than M times the stator length and less than M + 1 times the stator length is defined as a linear motor with a long mover; further, the linear motor with a long mover also includes a motor with a mover length equal to M times the stator length. Wherein, M belongs to non-zero natural numbers and M is greater than or equal to 1.

[0074] In a 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 synthetic thrust can be expressed by the following formula:

[0075] (3);

[0076] 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…}.

[0077] According to the position information of the mover, calculate the coupling coefficient between the mover and each segment of the stator. 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.

[0078] According to the coupling coefficient between the mover and the stator, if the coupling coefficient between the mover and any segment of the stator is not zero, then supply power to this segment to generate effective thrust; if the coupling coefficient between the mover and any segment of the stator is zero, then stop supplying power to this segment of the stator to cut off the power to reduce energy consumption. For example, when the head of the mover enters a new segment of the stator, the coupling coefficient of this segment gradually increases from 0, and the power supply signal is synchronously activated to supply power to this segment of the stator; when the tail of the mover disengages 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 accordingly.

[0079] Further, according to the length relationship between the mover and the stator, one or several inverters can be selected to supply power to the stator segments in a switched manner. At least one inverter can be selected for power supply, and at most the same number of inverters as the total number of stator segments can be selected for power supply. In the embodiment of the present application, the number of selected inverters is equal to the maximum number of stator segments coupled by the mover, which reduces the cost and the requirements for the power supply performance while meeting the working requirements of the linear motor.

[0080] According to the above description, a control method for a linear motor provided by the present application calculates the coupling coefficients between the mover and each section 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. According to the coupling coefficients between the mover and each section of the stator of the linear motor, the power supply unit is flexibly adjusted to supply power to the stator section, ensuring the continuity of the thrust received by the mover while reducing energy loss and lowering the operating cost of the linear motor.

[0081] As an implementation, as Figure 2 shown, the control method further includes the following steps:

[0082] Step S121, define the number of coupling coefficients to be calculated within a control period as the first quantity, and the first quantity is determined by the maximum number of coupled sections between the mover and the stator.

[0083] Step S122, determine the initial position of the mover relative to the stator, and 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 to determine the initial power supply state of each section of the stator.

[0084] Step S123, 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 state of each section of the stator according to the power supply strategy.

[0085] Specifically, the determination of the first quantity depends on the maximum number of coupled sections between the mover and the stator, that is, the maximum value of the stator sections that the mover may be coupled with simultaneously during the movement. The maximum number of coupled sections is determined by the length of the mover and the length of a single section of the stator. For example, if the length of the mover is twice the length of a single section of the stator, the mover can cover at most three sections of the stator. By defining the first quantity, computing resources can be pre-allocated to ensure that only the possibly coupled stator sections are accurately calculated within each control period, avoiding redundant operations.

[0086] When the motor starts or resets, determine the initial position of the mover relative to the stator. Taking the position of the mover's head as a reference point, calculate the initial values of the coupling coefficients corresponding to the first quantity based on the initial position of the mover. Combine the initial values of the coupling coefficients 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 an effective coupling with the mover. Through the precise matching of the initial position of the mover and the coupling coefficients, a stable thrust output is quickly established in the motor startup stage, reducing the mechanical impact on the mover during motor startup.

[0087] During the movement of the mover, its position changes continuously with time. Based on the new position information of the mover, the coupling coefficients of the first quantity are recalculated to ensure that the operation is only performed on the stator segments that may be coupled currently. After the calculation of the coupling coefficients is completed, the power supply states of each stator segment are redetermined according to the power supply strategy: the newly coupled segments between the mover and the stator are immediately powered on, and the disengaged segments between the mover and the stator are powered off in a timely manner. By continuously updating the position and adjusting the power supply, the stability of the thrust and the optimization of the energy efficiency are maintained during complex motion trajectories.

[0088] As an implementation manner, the control method further includes: after updating the position of the mover relative to the stator, determining whether the mover exceeds the stator track of the linear motor. If so, controlling to stop power supply to the stator; otherwise, continuously updating the position of the mover.

[0089] Specifically, the position of the mover is dynamically monitored. If it is detected that the mover exceeds the stator track of the linear motor, at this time, the coupling coefficients between the mover and all stator segments are zero, and the power supply to the stator segments is stopped 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, the position data of the mover is continuously updated, and the power supply states of each stator segment are dynamically adjusted according to the latest coupling coefficients to ensure continuous thrust. By monitoring the position of the mover in real time and intelligently adjusting the power supply strategy to the stator, the motion state of the mover is adjusted, and the safety and energy saving of the operation of the linear motor are realized.

[0090] As an implementation manner, a first intermediate variable is defined, and the first intermediate variable is represented by the following formula:

[0091] (4);

[0092] 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.

[0093] It can be seen from the above formula that the maximum number of segments coupled between the mover and the stator is segments. Then, at any moment, coupling coefficients are calculated simultaneously, that is, there are inverters and power supply signals respectively. At this time, there are coupling coefficients , and 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 segments of the stator.

[0094] When the length of the rotor x m and the length of the stator x s satisfy the relationship: or , where . Define the current motor as a long-rotor motor. During the movement of the rotor, the position of the rotor head is taken as the rotor position. At the initial moment, . At this time, the coupling coefficient p c ( n ) The initial value is obtained through the following formula:

[0095] When , there is

[0096] (5);

[0097] In the formula, p s represents the number of stator pole pairs, p m represents the number of rotor pole pairs.

[0098] When , there is

[0099] (6);

[0100] As an implementation, the coupling coefficient is also related to the motion state of the rotor relative to the stator. The motion state includes one or more of the following types of motion states: the rotor enters a certain segment of the stator, the rotor detaches from a certain segment of the stator, the rotor is stably coupled with the stator, and the rotor is not coupled with the stator.

[0101] The state of the rotor at a certain moment can be a combination of one or more of the above motion states. For example, the rotor enters a certain segment of the stator and detaches from a certain segment of the stator at the same time. When the head of the rotor starts to enter a certain segment of the stator, the coupling coefficient gradually increases, gradually activating the power supply to this segment of the stator. The rotor and this segment of the stator have magnetic field coupling to increase the thrust on the rotor. When the tail of the rotor gradually detaches from a certain segment of the stator, the coupling coefficient gradually decreases, gradually reducing the power supply to this segment of the stator until it is completely cut off, and the magnetic field between the rotor and this segment of the stator decays to zero, thereby preventing the magnetic field residue from interfering with the thrust synthesis of the rotor.

[0102] When the mover completely covers a certain section of the stator, the two are in a fully coupled state, and the coupling coefficient can reach the maximum value of 1. Continuously supply full power to this section of the stator to provide a stable maximum thrust and ensure the efficient operation of the motor. When the mover completely disengages from a certain section of the stator and has not entered the next section of the stator, the coupling coefficient between the mover and the stator is zero, there is no magnetic field interaction between the mover and the stator, cut off the power supply to this section of the stator, reduce the ineffective energy consumption of the motor, and reduce electromagnetic interference.

[0103] Accurately obtain the position information of the mover. When the mover is coupled with a certain section of the stator, power needs to be supplied to this section of the stator. During the movement of the mover, it is necessary to continuously calculate the coupling coefficient. As an implementation method, define the state switching function of the coupling coefficient, and the state switching function is obtained by calculating through the following formula:

[0104] (7);

[0105] In the formula, p s represents the number of stator pole pairs, represents the mover position, which is a function of time, and the initial value ; is the position of the head of the mover in different states. Its value is discrete and is related to the stator length, mover length, and the current position of the mover. The initial value ; represents the slope of the change process; represents the pole pitch.

[0106] During the movement of the mover on the stator track, the state switching function is continuously calculated, and then the coupling coefficient is calculated by p c ([[]] n ). If the head of the mover enters the next section of the stator and the tail of the mover disengages from the previous section of the stator, the thrust gradually decreases, and the thrust gradually increases. The combined thrust still remains at the thrust required for the movement of the mover. During the movement of the mover, the minimum forward distance is one pole pitch as a unit to calculate the coupling coefficient. That is, when the mover is coupled with multiple sections of the stator, the minimum unit of thrust fluctuation is measured by the distance that the mover advances one pole pitch .

[0107] As an implementation method, the control method also includes:

[0108] Define a second intermediate variable, and the second intermediate variable is represented by the following formula:

[0109] (8);

[0110] In the formula, T emp represents the second intermediate variable, N c represents the first intermediate variable, and b is an integer variable, and the integer variable b changes with the change of the mover position.

[0111] During the forward movement of the mover, the second intermediate variable T emp has a value 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.

[0112] The coupling coefficient p c ( n ) is updated as follows, where n = (1, 2, 3... N c +1).

[0113] When the mover enters the stator state, at this time , the coupling coefficient is expressed by the following formula:

[0114] (9);

[0115] 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, y ( t ) represents the state switching function.

[0116] When the mover detaches from the stator state, at this time , the coupling coefficient is expressed by the following formula:

[0117] (10);

[0118] In the formula, x represents the position of the mover head, x s represents the stator length, x m represents the mover length, p s represents the number of stator pole pairs, pm represents the number of rotor pole pairs, y ( t ) represents the state switching function.

[0119] In the stable coupling state of the rotor and the stator, there is , and the coupling coefficient is expressed by the following formula:

[0120] (11);

[0121] In the non - coupling state of the rotor and the stator, there is , and the coupling coefficient is expressed by the following formula:

[0122] (12);

[0123] In the formula, x represents the position of the rotor head, x s represents the stator length, x m represents the rotor length, p s represents the number of stator pole pairs, p m represents the number of rotor pole pairs.

[0124] Furthermore, when the relationship between the rotor length x m and the stator length x s satisfies: ; define the current motor as a short - rotor motor. During the movement of the rotor, taking the position of the rotor head as the rotor 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 relationship between the first intermediate variable N c and the second intermediate variable T emp satisfies:

[0125] (13);

[0126] When the rotor enters the stator state, the coupling coefficient is expressed by the following formula:

[0127] (14);

[0128] In the formula, x represents the position of the rotor head, xs Represents the stator length, x m Represents the rotor length, T emp Represents the second intermediate variable.

[0129] When the rotor is disengaged from the stator, the coupling coefficient is expressed by the following formula:

[0130] (15);

[0131] In the formula, x Represents the position of the rotor head, x s Represents the stator length, x m Represents the rotor length, T emp Represents the second intermediate variable.

[0132] When the rotor and the stator are in a stable coupling state, when the rotor state satisfies:

[0133] (16);

[0134] At this time, the coupling coefficient is: , .

[0135] When the rotor and the stator are in a non - coupling state, when the rotor position satisfies:

[0136] (17);

[0137] At this time, the coupling coefficient is: , .

[0138] Furthermore, when the rotor 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 rotor. The power - supply signal is expressed by the following formula:

[0139] (18);

[0140] In the formula, s c ( n ) represents the power - supply signal, and , p c ( n ) represents the coupling coefficient.

[0141] 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.

[0142] In the control method provided by this application, the process of switching the power supply strategy is as Figure 3 shown. Determine the mover length x m and the stator length x s . According to the mover length and the stator length, determine whether the linear motor is a long-mover linear motor or a short-mover linear motor, 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 mover and the stator, and the initial values of both the coupling coefficient and the power supply signal are zero. Denote the initial value of the coupling coefficient as p c0 ( n ), and denote the initial value of the power supply signal as s c0 ( n ). Denote the number of coupled segments between the mover 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 mover and the stator is N c +1.

[0143] Initialize the loop, configure the integer variable b and the number of coupled segments n to 0, calculate the mover position x ( n ) = g ( T emp , N c ), update the mover position data, and calculate the coupling coefficient p c ( n ) and the power supply signal s c ( n ), and control the power supply to the stator segment (the specific calculation processes of the coupling coefficient p c ( n ) and the power supply signal s c ( n ) have been described above and will not be described here again).

[0144] Increment the number of coupled segments n, and judge whether the number of coupled segments n is greater than or equal to the maximum number of coupled segments between the mover and the stator N c +1. Calculate at each moment within a control periodN c +1 coupling coefficient p c ( n ) with the power supply signal s c ( n ), if the number of coupling segments n is less than the maximum number of coupling segments between the mover and the stator N c +1, then return the coupling coefficient after the increment of the calculated number of coupling segments n p c ( n ) with the power supply signal s c ( n ), the number of coupling segments n is incremented again, and judged according to the loop condition. If the number of coupling segments n is greater than or equal to the maximum number of coupling segments 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 length of the stator track X max x s + x m , then the judgment condition is satisfied and the loop ends.

[0145] At this time, the power supply signal s c ( n ) is configured to 0, the power supply to the stator segment is ended, 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. For the power supply to the stator segment coupled to the mover, the thrust applied to the mover is maintained until the mover position exceeds the stator track and the loop ends.

[0146] According to the above description, when the linear motor is in the working state, the mover position changes continuously by position, and the head position of the mover is re-assigned. Each 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, thus forming a complete control cycle.

[0147] As an implementation, the control method further includes: in response to a gap existing between the stators of the linear motor, when determining the maximum number of coupled segments between the mover and the stators, the gap length of the stators 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 stators is added as an influencing factor.

[0148] Specifically, if there is a gap between the stators, the determination of the maximum number of coupled segments needs to consider the compression of the mover's coverage range by the gap. When there is a gap, the mover needs to move an additional gap distance 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 accurate distribution of power supply to the stators.

[0149] 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, thereby avoiding mis-triggering of power supply in the gap area and ensuring the effectiveness of magnetic field interaction. At the same time, when the tail of the mover 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 operation of subsequent segments.

[0150] By incorporating the gap length of the stators as an influencing factor into the power supply strategy, the control method can dynamically adjust the power supply timing to the stators. 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 the thrust mutation and improve the performance of the linear motor.

[0151] To further illustrate a control method for a linear motor provided in the present application, the following will be described with different length combinations of the stator and the mover.

[0152] The moving speed of the mover is set as shown in Table 1 below:

[0153]

[0154] When the length of the mover x m and the length of the stator x s satisfy: , where h is a constant.

[0155] 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:

[0156]

[0157] Configure the constant h to 0.8. At this time, the coupling coefficient of the linear motor and the power supply signal waveform are as Figure 4 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 4 The upper part is the coupling coefficient and power supply signal waveform diagram of the odd stator segments. Figure 4 The lower part is the coupling coefficient and power supply signal waveform diagram of the even stator segments. It can be seen from Figure 4 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.

[0158] 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:

[0159]

[0160] Configure the constant h to 1. At this time, the coupling coefficient of the linear motor and the power supply signal waveform 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 power supply signal waveform diagram of the odd stator segments. Figure 5 The lower part is the coupling coefficient and power supply signal waveform diagram of the even 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 inverters supplying power to the stator segments in the linear motor.

[0161] 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:

[0162]

[0163] Configure the constant h to 1.5. At this time, the coupling coefficient of the linear motor and the power supply signal waveform 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 power supply signal waveform diagram of the (n + 1)-th stator segment. Figure 6 The middle part is the coupling coefficient and power supply signal waveform diagram of the (n + 2)-th stator segment. Figure 6The lower part is the coupling coefficient and power supply signal waveform diagram of the n+3 stator segment.

[0164] 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 segment, and there are two or more power supply signals at any time in the linear motor.

[0165] 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.

[0166]

[0167] At this time, when the mover length x m and the stator length x s satisfy: , the maximum number of coupled segments between the mover and the stator is three. At the same time, it is necessary to calculate three coupling coefficients. The converter 1, converter 2, and converter 3 are respectively connected to , , segments of the stator for power supply. The electrical parameters of the linear motor are as follows: the resistance is , the inductance is , the fundamental flux linkage amplitude is , the mover mass is 300 kg, the ejected cargo is 2000 kg, and the bus voltage is .

[0168] Adopt vector control of current . Each segment 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.

[0169] The motion speed of the mover is set as shown in Table 6 below:

[0170]

[0171] 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 coupling coefficient waveform diagram, and the dashed line is the power supply signal waveform diagram. Take the state switching function to calculate the coupling coefficient , and the magnitude of the coupling coefficient Determines the thrust magnitude of each stator segment on the mover, and the sum of the coupling coefficients of each stator segment is equal to 1, that is, the coupling coefficients exist .

[0172] After the mover of the linear motor throws the goods when the speed is the highest, then the mover returns to realize the catapulting process. Exemplarily, as Figure 8 shown in the lower part, the mover carries the goods to move. When the linear velocity reaches the maximum of 35 m / s (t = 2.2 s) during the forward acceleration stage, 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. Finally, the return speed drops to zero, and the mover returns to the origin, waiting for the next catapulting. As Figure 8 shown in the upper part, during the catapulting stage and the return stage of the mover, the maximum speed error of the mover does not exceed .

[0173] Exemplarily, using a turn-off high-power silicon carbide module 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 is composed of 6 silicon carbide modules in parallel in pairs and then 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 composed of , , the electromagnetic forces applied by the stator segments thrust synthesis. According to the maximum mass and acceleration of the mover, the theoretical maximum thrust is .

[0174] According to the above description, a control method for a linear motor provided by the present application calculates the coupling coefficients between the mover and each stator segment of the linear motor based on the relative length relationship between the mover and the stator, combines the position information of the mover, and flexibly adjusts the power supply unit to supply power to the stator segments, realizing the general control of long / short mover motors, 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 operating cost of the linear motor.

[0175] It will be understood that the term "exemplary" as used herein means "serving as an example, instance, or illustration". Any embodiment described as "exemplary" is not necessarily preferred or superior to other embodiments and / or does not exclude incorporating features of other embodiments. It should be understood that certain features of the present application that are described in the context of separate embodiments for clarity may also be provided in combination in a single embodiment. Conversely, the various features of the present application that are described in the context of a single embodiment for clarity may also be provided separately or in any suitable combination or as any other described embodiment of the present application.

[0176] 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 sections of stators, characterized in that, The control method includes: Obtaining the structural parameters of the linear motor, where the structural parameters include pole pitch, mover length, mover pole pair number, stator length, stator pole pair number, and stator segment number; Calculating the coupling coefficients between the mover and each stator segment, where 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 stator segment is equal to 1; Powering the stator according to a power supply strategy based on the coupling state between the mover and the stator, where the power supply strategy includes: powering a stator segment in response to the coupling coefficient between the mover and any stator segment being non-zero, and stopping power supply to a stator segment in response to the coupling coefficient between the mover and any stator segment being zero; Defining the number of coupling coefficients to be calculated within a control period as a first quantity, where the first quantity is determined by the maximum number of coupled segments between the mover and the stator; Determining the initial position of the mover relative to the stator, calculating the initial values of the first quantity of coupling coefficients based on the initial position, and combining the first quantity of coupling coefficient initial values with the power supply strategy to determine the initial power supply state of each stator segment; Updating the position of the mover relative to the stator, recalculating the first quantity of coupling coefficients after the position update, and re-determining the power supply state of each stator segment according to the power supply strategy; Defining a first intermediate variable, where the first intermediate variable is represented by the following formula: ； The initial values of the coupling coefficients are obtained through the following formula: When there is ； When there is ； In the formula, x s represents the stator length, x m represents the rotor length; p s represents the number of stator pole pairs, p m represents the number of rotor pole pairs.

2. The control method of the linear motor according to claim 1, wherein The control method further includes: After updating the position of the mover relative to the stator, determining whether the mover exceeds the stator track of the linear motor. If so, controlling to stop power supply to the stator; otherwise, continuously updating the mover position.

3. The control method of the linear motor according to any one of claims 1 to 2, characterized in that The coupling coefficients are 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 stator segment, the mover detaches from a certain stator segment, the mover is stably coupled with the stator, and the mover has no coupling with the stator.

4. The control method of the linear motor according to claim 3, characterized in that Defining a state switching function of the coupling coefficients, where the state switching function is calculated through the following formula: ； wherein, p s represents the number of stator pole pairs, represents the mover position, which is a function of time, with an initial value ; is the position of the mover's head in different states, and its value is discrete. It is related to the stator length, mover length, and the current position of the mover, with an initial value ; represents the slope of the change process; represents the pole pitch.

5. The control method of the linear motor according to claim 4, wherein The control method further includes: Defining a second intermediate variable, where the second intermediate variable is represented by the following formula: ； wherein, N c represents a first intermediate variable, b is an integer variable, and the integer variable b changes with the change of the mover position; When the mover enters the stator 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, y ( t ) represents the state switching function.

6. The control method of the linear motor according to claim 4, wherein, The control method further includes: Defining a second intermediate variable, where the second intermediate variable is represented by the following formula: ； In the formula, N c represents a first intermediate variable, b is an integer variable, and the integer variable b changes with the change of the mover position; When the mover is detached from the stator, 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, y ( t ) represents the state switching function.

7. The control method of the linear motor according to claim 4, characterized in that The control method further includes: Defining a second intermediate variable, where the second intermediate variable is represented by the following formula: ； In the formula, N c represents a first intermediate variable, b is an integer variable, and the integer variable b changes with the change of the mover 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-coupled 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.

8. The control method of the linear motor according to claim 4, characterized in that, The control method further includes: In response to a gap existing between stators of the linear motor, when determining the maximum number of coupled segments of the coupling between the mover and the stators, the gap length of the stators 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 stators is added as an influencing factor.

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