Full-stroke linear absolute position detection method

Abstract

The invention discloses a full-stroke linear absolute position detection method, and belongs to the technical field of position detection. The invention aims to solve the problems of complex circuit structure and low detection precision of the existing full-travel rotor cable-free absolute position detection method. Comprising the steps that a permanent magnet array is installed on a rotor, an anisotropic magnetoresistive sensor array is correspondingly arranged on a stator, and the length of the anisotropic magnetoresistive sensor array is the position detection total stroke; the polar distance between adjacent permanent magnets is the same as the distance between adjacent sensors; determining a main sensor in a middle position in a coupling state according to the current sensor coupling number and the permanent magnet pole number, and calculating the current absolute position initial value of the rotor according to the angle reading of the main sensor; and position compensation is carried out on the current absolute position initial value of the rotor according to the pole number of the permanent magnets, the total number of the sensors and the relative position relation between the main sensor and the permanent magnet array, and the final detection position of the rotor is obtained. The method is used for absolute position detection.

Description

Technical Field

[0001] The invention relates to a full-stroke linear absolute position detection method, belonging to the technical field of position detection. Background Art

[0002] In high-precision and high-speed direct drive applications, in order to avoid the nonlinear force caused by cable drag on the mover, a linear motor with a permanent magnet on the moving secondary is used. At the same time, it is required that there are no additional cables on the mover, which also puts forward requirements for position detection. Traditional grating position sensors install the reading head on the mover, which cannot meet the requirement of cable-free movers; and when the reading head is placed on the stator, a large number of reading heads under the full stroke leads to extremely high costs. For magnetic sensors, the commonly used incremental position detection requires obtaining the initial position each time, which is unacceptable in the modern industrial field.

[0003] The existing full-stroke mover cable-free absolute position detection sensor is realized by the cooperation of two groups of Hall sensors, one group is used for encoding, and the other group is used for specific position detection. This method adds an extra group of sensors, which makes the circuit complex and the cost high. At the same time, the Hall device is sensitive to non-saturated magnetic fields, and the air gap between the magnet and the device is difficult to ensure uniformity. The harmonic components in the magnet's magnetic field cannot be avoided, which greatly limits the detection accuracy of this method. Summary of the invention

[0004] In view of the problems that the existing full-stroke mover cable-free absolute position detection method has a complex circuit structure and low detection accuracy, the present invention provides a full-stroke linear absolute position detection method.

[0005] A full-stroke linear absolute position detection method of the present invention comprises:

[0006] A permanent magnet array and a corresponding anisotropic magnetoresistive sensor array are designed, the permanent magnet array is mounted on the mover, the anisotropic magnetoresistive sensor array is correspondingly arranged on the stator, and the length of the anisotropic magnetoresistive sensor array is the full stroke of position detection; the adjacent permanent magnet pole pitch in the permanent magnet array is the same as the adjacent sensor pitch in the anisotropic magnetoresistive sensor array;

[0007] Offline calibration of the sensor reading area when the sensor is coupled with a permanent magnet;

[0008] Determine the main sensor in the middle position in the coupling state according to the current number of sensor couplings and the number of permanent magnet poles, and calculate the initial value of the current absolute position of the mover according to the angle reading of the main sensor;

[0009] Then, according to the number of permanent magnet poles, the total number of sensors and the relative position relationship between the main sensor and the permanent magnet array, the initial value of the current absolute position of the mover is compensated to obtain the final detection position of the mover.

[0010] According to the full-stroke linear absolute position detection method of the present invention, the length of the anisotropic magnetoresistive sensor array is set to L:

[0011] L = (n-1)*d,

[0012] Where n is the total number of sensors and d is the distance between adjacent sensors.

[0013] According to the full-stroke linear absolute position detection method of the present invention, the number of permanent magnet poles is an even number and is at least 4.

[0014] According to the full-stroke linear absolute position detection method of the present invention, the state when the linear distance of the sensor beyond the permanent magnet at the edge of the permanent magnet array exceeds three quarters of the pole pitch is marked as a non-coupling state.

[0015] According to the full-stroke linear absolute position detection method of the present invention, the minimum limit value of the number of sensor couplings is expressed as C min :

[0016]

[0017] Where P is the number of permanent magnet poles.

[0018] According to the full-stroke linear absolute position detection method of the present invention, the total number of sensors is set to n, and firstly, all sensors are marked with serial numbers in order from 0 to n-1;

[0019] The number of sensor couplings is represented as Count, the serial number of the first sensor in the coupling state is represented as S0, and the serial number of the last sensor in the coupling state is represented as S1:

[0020] Then Count = S1 - S0 + 1;

[0021] Then, the anisotropic magnetoresistive sensor array is divided into a left area, a right area and a middle area according to the coupling position between the anisotropic magnetoresistive sensor array and the permanent magnet array;

[0022] If S1=n-1, and Count≤P+1, the permanent magnet array is in the right area of ​​the anisotropic magnetoresistive sensor array, and S0>n-(P+2);

[0023] If S0=0, and Count≤P+1, the permanent magnet array is located in the left area of ​​the anisotropic magnetoresistive sensor array, and S0≤n-(P+2);

[0024] Otherwise, the permanent magnet array is located in the middle area of ​​the anisotropic magnetoresistive sensor array, and S0≤n-(P+2).

[0025] According to the full-stroke linear absolute position detection method of the present invention, the serial number of the main sensor is represented by S N ;

[0026] In the right area, the serial number S of the main sensor N Determined by S0;

[0027] In the left area, the main sensor is numbered S N Determined by S1;

[0028] In the middle area, the value of Count varies between P+1 and P+2; the serial number of the main sensor S N Determined by S1;

[0029]

[0030] According to the full-stroke linear absolute position detection method of the present invention, the initial value of the current absolute position of the mover is expressed as Pos:

[0031] Pos=S N *τ+Angle M *τ / 360,

[0032] Where τ is the pole distance, Angle M Main sensor S N Angle reading.

[0033] According to the full-stroke linear absolute position detection method of the present invention, in the left area and the middle area, the calculation method of the position compensation amount Comp0 is:

[0034]

[0035] Where Angle1 is the angle reading of sensor S1, θ0 is the maximum reading of sensor S1 before it switches from the uncoupled state to the coupled state;

[0036] In the right area, the position compensation value Comp1 is calculated as follows:

[0037]

[0038] Where Angle0 is the angle reading of sensor S0, and θ1 is the minimum reading of sensor S0 before it switches from the coupled state to the uncoupled state.

[0039] According to the full-stroke linear absolute position detection method of the present invention, the final detection position of the mover Pos f for:

[0040] Pos f =S N *τ+Angle M*τ / 360+Comp0+Comp1.

[0041] Beneficial effects of the invention: The method of the invention performs dynamic magnetic absolute position detection of the motor's full stroke based on the magnetoresistance effect, can be applied in the fields of automation and intelligent manufacturing, has the advantages of full stroke, high precision, low cost and no cable constraints, and can be used for precise position control of flexible linear motor transmission systems, intelligent logistics and production lines.

[0042] The method of the present invention adopts absolute position detection, and the designed permanent magnet array is directly installed on the mover, and the sensor array is installed on the stator. Absolute position detection is performed in the order of main sensor serial number determination, position compensation calculation and position splicing algorithm. Experiments have shown that the method of the present invention can directly obtain the absolute position when the system starts without position initialization, and the restart position will not change after an abnormal power outage. At the same time, a completely cable-free design is also realized on the motor mover, and only a row of permanent magnet arrays needs to be added to the mover. The air gap requirement between the array and the stator is also low, which greatly reduces the structural and installation requirements, and has great significance for the industrial application of long-stroke linear motors. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic diagram of the corresponding relationship between the permanent magnet array and the anisotropic magnetoresistive sensor array in the full-stroke linear absolute position detection method of the present invention;

[0044] Figure 2 This is a schematic diagram of position jump caused by sensor angle jump;

[0045] Figure 3 It is a schematic diagram of position compensation in the left area;

[0046] Figure 4 It is a schematic diagram of position compensation in the right area;

[0047] Figure 5 is a flow chart of the method of the present invention;

[0048] Figure 6 is a schematic diagram of position detection results before compensation;

[0049] Figure 7 It is a schematic diagram of the position detection result after compensation. DETAILED DESCRIPTION

[0050] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0051] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0052] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0053] Specific implementation method 1. Combination Figure 1 and Figure 5 As shown, the present invention provides a full-stroke linear absolute position detection method, comprising:

[0054] A permanent magnet array and a corresponding anisotropic magnetoresistive sensor array are designed, the permanent magnet array is mounted on the mover, the anisotropic magnetoresistive sensor array is correspondingly arranged on the stator, and the length of the anisotropic magnetoresistive sensor array is the full stroke of position detection; the adjacent permanent magnet pole pitch in the permanent magnet array is the same as the adjacent sensor pitch in the anisotropic magnetoresistive sensor array;

[0055] Offline calibration of the sensor reading area when the sensor is coupled with a permanent magnet;

[0056] Determine the main sensor in the middle position in the coupling state according to the current number of sensor couplings and the number of permanent magnet poles, and calculate the initial value of the current absolute position of the mover according to the angle reading of the main sensor;

[0057] Then, according to the number of permanent magnet poles, the total number of sensors and the relative position relationship between the main sensor and the permanent magnet array, the initial value of the current absolute position of the mover is compensated to obtain the final detection position of the mover.

[0058] Combination Figure 1 As shown, the length of the anisotropic magnetoresistive sensor array is set to L:

[0059] L = (n-1)*d,

[0060] Where n is the total number of sensors and d is the distance between adjacent sensors.

[0061] In this embodiment, the number of permanent magnet poles P is not limited, but the number of permanent magnet poles is an even number, and in order to generate a good sinusoidal magnetic field, it is at least 4. Generally speaking, the permanent magnet array is directly mounted on the mover, and the total length is less than or equal to the length of the mover. There is no strict distance limit between the permanent magnet array and the sensor array. It only needs the magnetic field of the permanent magnet array to saturate the magnetic field detected by the sensor. Generally, the closer the better. In practical applications, it is often limited by the actual motor structure.

[0062] A state in which the linear distance of the sensor beyond the permanent magnet at the edge of the permanent magnet array exceeds three quarters of the pole pitch is marked as a non-coupling state.

[0063] Further, based on the above hardware design, the method for realizing position detection is as follows:

[0064] Offline calibration limits the sensor's reading area to the area covered by the permanent magnet array, and the area outside is marked as a non-coupling state.

[0065] The minimum limit of the number of sensor couplings is expressed as C min :

[0066]

[0067] Where P is the number of permanent magnet poles.

[0068] Among them, C min Determined by the number of permanent magnet poles P, increasing or decreasing it will change the maximum detection stroke. Considering the symmetry of the left and right areas and the position detection stroke equal to the sensor array length, half of the maximum number of couplings during the motion of the actuator is generally taken as C. min .

[0069] Assume the total number of sensors is n, first mark all sensors in order from 0 to n-1;

[0070] The number of sensor couplings is represented as Count, the serial number of the first sensor in the coupling state is represented as S0, and the serial number of the last sensor in the coupling state is represented as S1:

[0071] Then Count = S1 - S0 + 1;

[0072] Then, the anisotropic magnetoresistive sensor array is divided into a left area, a right area and a middle area according to the coupling position between the anisotropic magnetoresistive sensor array and the permanent magnet array;

[0073] If S1=n-1, and Count≤P+1, the permanent magnet array is in the right area of ​​the anisotropic magnetoresistive sensor array, and S0≥nP-1, that is, S0>n-(P+2);

[0074] If S0=0, and Count≤P+1, the permanent magnet array is located in the left area of ​​the anisotropic magnetoresistive sensor array, and S0≤n-(P+2);

[0075] Otherwise, after removing the left area and the right area, the remaining situation is that the permanent magnet array is in the middle area of ​​the anisotropic magnetoresistive sensor array, and at this time S0≤n-(P+2).

[0076] Furthermore, the serial number of the main sensor is represented as S N ;

[0077] In Count≥C min In the case of , it is considered to have entered the position detection area and the position calculation begins. The position of the main sensor is determined by the position of the center of the permanent magnet array.

[0078] In the right area, the serial number S of the main sensor N Determined by S0; when Count is less than C min When the mover leaves the range of the sensor array;

[0079] In the left area, Count is greater than or equal to C min When the actuator enters the range of the sensor array, it starts to detect the position, and the serial number of the main sensor is S N Determined by S1;

[0080] In the middle area, the value of Count varies between P+1 and P+2; the serial number of the main sensor S N Determined by S1;

[0081]

[0082] According to the setting that the permanent magnet pole pitch τ is equal to the sensor spacing d, it can be known that the detection range of each sensor only covers one magnetic pole, which corresponds exactly to one cycle of the sensor output signal. Therefore, after determining the main sensor, the unique sensor cycle can be determined, locking the range of the absolute position in space.

[0083] Position stitching: After determining the serial number of the main sensor, you can read the S N , S0 and S1 sensors' angle readings.

[0084] The initial value of the current absolute position of the actuator is expressed as Pos:

[0085] Pos=S N *τ+Angle M *τ / 360,

[0086] Where τ is the pole distance, Angle M Main sensor S N Angle reading.

[0087] Position compensation: The reading of each sensor when changing between the uncoupled state and the coupled state is not 0°, so the reading of each sensor detection cycle is not from 0° to 360°, but from a certain initial angle to 360°, then jumps from 360° to 0, and then increases from 0 to near the initial angle. When the angle of the main sensor jumps from 360° to 0°, the serial number of the main sensor does not increase, then the corresponding position will jump by one pole distance. Figure 2 As shown, the horizontal axis is the actual spatial position of the mover, and the vertical axis is the value of different variables, including S N , Count, Pos, and Angle M It can be seen that when the mover moves from 209mm to 210mm, the Angle M From 355° to 0.4°, S N unchanged, so Pos has a negative jump.

[0088] Compensate for the above jump. First, the left and middle areas. The S N It switches following the switching of S1, and S0≤n-(P+2), so observe Figure 3 It can be found that if and only if the reading of S1 is Angle1 and S N Reading Angle M At the same time, when it is less than a specific angle θ0, a jump occurs, and the value of the negative jump is τ.

[0089] Therefore, in the left area and the middle area, the position compensation amount Comp0 is calculated as follows:

[0090]

[0091] Where Angle1 is the angle reading of sensor S1, θ0 is the maximum reading of sensor S1 before it switches from the uncoupled state to the coupled state;

[0092] Then the right area. The S N It switches following the switching of S0, and S0>n-(P+2). Therefore, observe Figure 4 It can be found that in the right area, only if and only if the readings of S0 Angle0 and S N Reading Angle M At the same time, no jump occurs in the area greater than the specific angle θ1, and a negative jump with a value of τ occurs in the remaining areas.

[0093] In the right area, the position compensation value Comp1 is calculated as follows:

[0094]

[0095] Where Angle0 is the angle reading of sensor S0, and θ1 is the minimum reading of sensor S0 before it switches from the coupled state to the uncoupled state.

[0096] Comp0 is calculated only when S0≤n-(P+2). When S0>n-(P+2), Comp0 is always 0. Comp1 is calculated only when S0>n-(P+2). When S0≤n-(P+2), Comp0 is always 0. θ0 and θ1 are the values ​​obtained in the experiment. The upper and lower limits of the value are affected by many factors such as the sinusoidality of the magnetic field, the output bias of different sensors, and the AD sampling bias. They need to be adjusted according to the actual application, but the value still has a very wide range of values, and the difference in values ​​does not affect the result as long as it is within the range. Generally speaking, the range of θ0 is 120° to 300°, and the range of θ1 is 60° to 240°.

[0097] The final detection position of the mover Pos f for:

[0098] Pos f =S N *τ+Angle M *τ / 360+Comp0+Comp1.

[0099] The flowchart of this embodiment is as follows Figure 5 shown.

[0100] The method of the present invention is experimentally verified by building a full-stroke linear motor system and adopting an absolute position detection method. The designed permanent magnet array is directly installed on the mover, and the sensor array is installed on the stator. The PCB of the sensor array is perpendicular to the mover. The signal output by the anisotropic magnetic resistance sensor collected by AD is read by FPGA, and absolute position detection is performed in the order of main sensor serial number determination, position compensation calculation and position splicing algorithm. The experimental results show the effectiveness of this implementation.

[0101] Example: Take a single detection circuit board composed of 32 magnetic sensor arrays as an example, the sensor spacing is 15mm, and the planned position detection stroke is 480mm. The number of permanent magnet poles of the permanent magnet array is 8, the pole pitch is 15mm, and C min 5 is obtained through cloud computing. Perform full-stroke movement and calculate S N , read Angle M , calculate the uncompensated position Pos, and get the result as Figure 6 shown.

[0102] It can be seen that with the positive movement of the mover, the serial number S of the main sensorN The number of coupled sensors Count gradually increases, then enters the fully coupled area and becomes 9 and 10 alternately, and finally gradually decreases in the right area. The position calculation starts only when the number of coupled sensors Count ≥ 5. Angle of the main sensor Angle M It presents a periodic sawtooth wave, and the increasing positions of the splicing also have negative jumps.

[0103] Compensation amount Comp0 is calculated in the left area and the middle area, and compensation amount Comp1 is calculated in the right area, and θ0 and θ1 are taken as 180° and 220° respectively. Calculate the position after compensation Pos f The experimental results obtained are as follows Figure 7 It can be seen that the output position signal is continuous, and the total position detection stroke is about 490mm, which is greater than 480mm, meeting the design requirements of the invention.

[0104] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims

1. A full-stroke linear absolute position detection method, characterized in that: include: A permanent magnet array and a corresponding anisotropic magnetoresistive sensor array are designed, the permanent magnet array is mounted on the mover, the anisotropic magnetoresistive sensor array is correspondingly arranged on the stator, and the length of the anisotropic magnetoresistive sensor array is the full stroke of position detection; the adjacent permanent magnet pole pitch in the permanent magnet array is the same as the adjacent sensor pitch in the anisotropic magnetoresistive sensor array; Offline calibration of the sensor reading area when the sensor is coupled with a permanent magnet; Determine the main sensor in the middle position in the coupling state according to the current number of sensor couplings and the number of permanent magnet poles, and calculate the initial value of the current absolute position of the mover according to the angle reading of the main sensor; Then, according to the number of permanent magnet poles, the total number of sensors and the relative position relationship between the main sensor and the permanent magnet array, the initial value of the current absolute position of the mover is compensated to obtain the final detection position of the mover.

2. The full-stroke linear absolute position detection method according to claim 1, characterized in that: Set the length of the anisotropic magnetoresistive sensor array to L: L = (n-1)*d, Where n is the total number of sensors and d is the distance between adjacent sensors.

3. The full-stroke linear absolute position detection method according to claim 2, characterized in that: The number of permanent magnet poles is an even number and is at least 4.

4. The full-stroke linear absolute position detection method according to claim 3, characterized in that: A state in which the linear distance of the sensor beyond the permanent magnet at the edge of the permanent magnet array exceeds three quarters of the pole pitch is marked as a non-coupling state.

5. The full-stroke linear absolute position detection method according to claim 4, characterized in that: The minimum limit of the number of sensor couplings is expressed as C min : Where P is the number of permanent magnet poles.

6. The full-stroke linear absolute position detection method according to claim 5, characterized in that: Assume the total number of sensors is n, first mark all sensors in order from 0 to n-1; The number of sensor couplings is represented as Count, the serial number of the first sensor in the coupling state is represented as S0, and the serial number of the last sensor in the coupling state is represented as S1: Then Count = S1 - S0 + 1; Then, the anisotropic magnetoresistive sensor array is divided into a left area, a right area and a middle area according to the coupling position between the anisotropic magnetoresistive sensor array and the permanent magnet array; If S1=n-1, and Count≤P+1, the permanent magnet array is in the right area of ​​the anisotropic magnetoresistive sensor array, and S0>n-(P+2); If S0=0, and Count≤P+1, the permanent magnet array is located in the left area of ​​the anisotropic magnetoresistive sensor array, and S0≤n-(P+2); Otherwise, the permanent magnet array is located in the middle area of ​​the anisotropic magnetoresistive sensor array, and S0≤n-(P+2).

7. The full-stroke linear absolute position detection method according to claim 6, characterized in that: The serial number of the main sensor is represented by S N ; In the right area, the serial number S of the main sensor N Determined by S0; In the left area, the main sensor is numbered S N Determined by S1; In the middle area, the value of Count changes between P+1 and P+2; the serial number of the main sensor S N Determined by S1; 8. The full-stroke linear absolute position detection method according to claim 7, characterized in that: The initial value of the current absolute position of the actuator is expressed as Pos: Pos=S N *τ+Angle M *t / 360, Where τ is the pole distance, Angle M Main sensor S N Angle reading.

9. The full-stroke linear absolute position detection method according to claim 8, characterized in that: In the left and middle areas, the position compensation amount Comp0 is calculated as follows: Where Angle1 is the angle reading of sensor S1, θ0 is the maximum reading of sensor S1 before it switches from the uncoupled state to the coupled state; In the right area, the position compensation value Comp1 is calculated as follows: Where Angle0 is the angle reading of sensor S0, and θ1 is the minimum reading of sensor S0 before it switches from the coupled state to the uncoupled state.

10. The full-stroke linear absolute position detection method according to claim 9, characterized in that: The final detection position of the mover Pos f for: Pos f =S N *τ+Angle M *τ / 360+Comp0+Comp1.

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