Full-stroke Linear Absolute Position Detection Method

Abstract

A full-stroke linear absolute position detection method belongs to the technical field of position detection. The present invention aims at the problems of complex circuit structure and low detection accuracy of the existing full-stroke mover wireless cable absolute position detection method. It includes installing a permanent magnet array on the mover, arranging an anisotropic magnetoresistive sensor array correspondingly 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 is the same as the adjacent sensor pitch; determining the main sensor in the middle position in the coupled state according to the current number of coupled sensors and the number of permanent magnet poles, and calculating 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, performing position compensation on the initial value of the current absolute position of the mover to obtain the final detected position of the mover. The present invention is used for absolute position detection.

Description

Technical Field

[0001] The present 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 non-linear force caused by the cable drag on the mover, a linear motor with a moving secondary permanent magnet is adopted, and at the same time, it is required that there is no extra cable on the mover, which also poses requirements for position detection. The traditional grating position sensor installs the reading head on the mover, which cannot meet the requirement of no cable on the mover; when the reading head is placed on the stator, a large number of reading heads in the full stroke result in extremely high costs. For magnetic sensors, the commonly used incremental position detection needs to obtain the initial position each time, which is unacceptable in the modern industrial field.

[0003] The existing absolute position detection sensor for a full-stroke mover without cables is realized by the cooperation of two groups of Hall sensors, one group for encoding and the other for specific position detection. This method adds an extra group of sensors, making the circuit complex and the cost high. At the same time, Hall devices are sensitive to non-saturated magnetic fields, it is difficult to ensure the uniformity of the air gap between the magnet and the device, and the harmonic components in the magnet magnetic field cannot be avoided, which greatly limits the detection accuracy of this method. Summary of the Invention

[0004] Aiming at the problems of complex circuit structure and low detection accuracy of the existing full-stroke mover without cable absolute position detection method, 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 includes:

[0006] Design a permanent magnet array and a corresponding anisotropic magnetoresistive sensor array, install the permanent magnet array on the mover, and set the anisotropic magnetoresistive sensor array correspondingly on the stator, and the length of the anisotropic magnetoresistive sensor array is the full stroke of position detection; the pole pitch between adjacent permanent magnets in the permanent magnet array is the same as the sensor pitch between adjacent sensors in the anisotropic magnetoresistive sensor array;

[0007] Offline calibrate the sensor reading area in the state of sensor-permanent magnet coupling;

[0008] Determine the main sensor at the intermediate 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 angular 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, perform position compensation on the initial value of the current absolute position of the mover to obtain the final detected 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 poles of the permanent magnet is an even number and 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 outermost permanent magnet in the permanent magnet array exceeds three - quarters of the pole pitch is marked as the 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 coupled sensors is represented as C min :

[0016]

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

[0018] According to the full - stroke linear absolute position detection method of the present invention, when the total number of sensors is set to n, first, all sensors are numbered in order from 0 to n - 1;

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

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

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

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

[0023] If S0 = 0 and Count≤P + 1, then the permanent magnet array is in the left - hand region of the anisotropic magnetoresistive sensor array, and at this time S0≤n-(P + 2);

[0024] Otherwise, the permanent magnet array is in the middle region of the anisotropic magnetoresistive sensor array, and at this time 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 as S N ;

[0026] In the right region, the serial number S of the main sensor N is determined by S0;

[0027] In the left region, the serial number S of the main sensor N is determined by S1;

[0028] In the middle region, the value of Count varies between P + 1 and P + 2; the serial number S of the main sensor N is 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 represented as Pos:

[0031] Pos = S N *τ + Angle M *τ / 360,

[0032] where τ is the pole pitch and Angle M is the angle reading of the main sensor S N ;

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

[0034]

[0035] where Angle1 is the angle reading of sensor S1, and θ0 is the maximum value of the reading of sensor S1 at the moment before the switch from the uncoupled state to the coupled state;

[0036] In the right region, the calculation method of the position compensation amount Comp1 is:

[0037]

[0038] where Angle0 is the angle reading of sensor S0, and θ1 is the minimum value of the reading of sensor S0 at the moment before the switch 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 detected position Pos of the mover f is:

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

[0041] Advantages of the present invention: The method of the present invention is based on the magnetoresistive effect for absolute position detection of the full stroke of the motor, which can be applied in the fields of automation and intelligent manufacturing. It has the advantages of full stroke, high precision, low cost and no cable constraint, 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. The designed permanent magnet array is directly installed on the mover, and the sensor array is installed on the stator. The absolute position detection is carried out in the order of determining the main sensor number, position compensation calculation and position splicing algorithm. Experiments show that the method of the present invention can directly obtain the absolute position at system startup without position initialization, and the position will not change after abnormal power failure and restart. At the same time, a completely cable-free design is also realized on the motor mover, and only one row of permanent magnet arrays needs to be added to the mover. The air gap requirement between this 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. Description of the Drawings

[0043] Figure 1 is a schematic diagram of the correspondence 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 is a schematic diagram of the position jump caused by the sensor angle jump;

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

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

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

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

[0049] Figure 7 is a schematic diagram of the position detection result after compensation. Detailed Embodiments

[0050] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0051] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0052] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but it is not limited to the present invention.

[0053] Specific embodiments: I. Combining Figure 1 and Figure 5 as shown, the present invention provides a full-stroke linear absolute position detection method, including:

[0054] Design a permanent magnet array and a corresponding anisotropic magnetoresistive sensor array. Install the permanent magnet array on the mover, and 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 pitches in the permanent magnet array are the same as the adjacent sensor pitches in the anisotropic magnetoresistive sensor array;

[0055] Offline calibrate the sensor reading area in the coupled state of the sensor and the permanent magnet;

[0056] Determine the main sensor in the middle position in the coupled state according to the current number of coupled sensors 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, perform position compensation on the initial value of the current absolute position of the mover to obtain the final detected position of the mover.

[0058] Combining Figure 1 as shown, set the length of the anisotropic magnetoresistive sensor array as L:

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

[0060] where n is the total number of sensors and d is the adjacent sensor pitch.

[0061] In this embodiment, the number of poles P of the permanent magnet is not limited, but the number of poles of the permanent magnet is even. In order to generate a good sine wave of the magnetic field, it is at least 4. Generally speaking, the permanent magnet array is directly installed 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, as long as the magnetic field of the permanent magnet array can saturate the magnetic field detected by the sensor. Generally, the closer the better, but in practical applications, it is often limited by the actual motor structure.

[0062] The state where the linear distance of the sensor exceeds three-quarters of the pole pitch of the outermost permanent magnet in the permanent magnet array is marked as the non-coupling state.

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

[0064] During offline calibration, the reading area of the sensor is restricted within the area covered by the permanent magnet array, and the area outside is marked as the non-coupling state.

[0065] Let the minimum limit value of the number of coupled sensors be C min :

[0066]

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

[0068] Among them, C min is determined by the number of poles P of the permanent magnet. Increasing or decreasing it will change the maximum detection stroke. Considering the symmetry of the left and right regions and the position detection stroke being equal to the length of the sensor array, generally, half of the maximum number of coupled sensors during the movement of the mover is taken as C min .

[0069] Set the total number of sensors as n. First, label the serial numbers of all sensors in sequence from 0 to n-1;

[0070] Let the number of coupled sensors be Count, the serial number of the first sensor in the coupling state be S0, and the serial number of the last sensor in the coupling state be S1:

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

[0072] Then, divide the anisotropic magnetoresistive sensor array into a left region, a right region, and a middle region according to the coupling position of the anisotropic magnetoresistive sensor array and the permanent magnet array;

[0073] If S1 = n - 1 and Count ≤ P + 1, then the permanent magnet array is in the right region of the anisotropic magnetoresistive sensor array. At this time, S0 ≥ n - P - 1, that is, S0 > n - (P + 2);

[0074] If S0 = 0 and Count ≤ P + 1, the permanent magnet array is in the left region of the anisotropic magnetoresistive sensor array. At this time, S0 ≤ n - (P + 2).

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

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

[0077] When Count ≥ C min , it is considered that the position detection area is entered and the position calculation starts. Determine the position of the main sensor based on the position of the center of the permanent magnet array.

[0078] In the right region, the serial number S of the main sensor N is determined by S0; when Count is less than C min , it is considered that the mover leaves the range of the sensor array;

[0079] In the left region, when Count is greater than or equal to C min , the mover enters the range of the sensor array and starts to detect the position. The serial number S of the main sensor N is determined by S1;

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

[0081]

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

[0083] Position splicing: After determining the serial number of the main sensor, the angular readings of the sensors of S N , S0 and S1 can be read.

[0084] The initial value of the current absolute position of the mover is represented as Pos:

[0085] Pos = S N *τ + Angle M *τ / 360,

[0086] where τ is the pole pitch and Angle M is the angular reading of the main sensor S N .

[0087] Position compensation: When each sensor changes between the uncoupled state and the coupled state, the reading is not 0°. Therefore, within the detection period of each sensor, the reading does not range from 0° to 360°, but increases 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 accordingly, and the corresponding position will jump by one pole pitch. As Figure 2 shown, the abscissa is the actual spatial position of the mover, and the ordinate is the values of different variables, including S N , Count, Pos, and Angle M . It can be seen that when the mover moves from 209 mm to 210 mm, Angle M changes from 355° to 0.4°. At this time, S N remains unchanged, so Pos undergoes a negative jump.

[0088] Compensation is performed for the above jumps. First, for the left and middle regions, the S in this region N switches following the switching of S1, and S0 ≤ n - (P + 2). Therefore, it can be observed Figure 3 that when and only when the reading Angle1 of S1 and the reading Angle N of S M are both less than a specific angle θ0, a jump occurs at this time, and the value of the negative jump is τ.

[0089] Therefore, in the left and middle regions, the calculation method of the position compensation amount Comp0 is as follows:

[0090]

[0091] In the formula, Angle1 is the angle reading of sensor S1, and θ0 is the maximum reading at the moment before sensor S1 switches from the uncoupled state to the coupled state;

[0092] Then, for the right region. The S in this region N switches following the switching of S0, and S0 > n - (P + 2). Therefore, it can be observed Figure 4 that in the right region, only when and only when the reading Angle0 of S0 and the reading Angle N of S M are both greater than a specific angle θ1, there is no jump in this region, and a negative jump with a value of τ occurs in the remaining regions.

[0093] In the right region, the calculation method of the position compensation amount Comp1 is as follows:

[0094]

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

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

[0097] The final detected position Pos of the mover f is:

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

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

[0100] The method of the present invention is experimentally verified. By building a full-stroke linear motor system, an absolute position detection method is adopted. The designed permanent magnet array is directly installed on the mover, the sensor array is installed on the stator, and the PCB of the sensor array is perpendicular to the mover. The signals output by the anisotropic magnetoresistive sensors collected by the AD are read through the FPGA, and the absolute position detection is carried out in the order of determining the main sensor number, calculating the position compensation, and the position splicing algorithm. The experimental results show the effectiveness of this embodiment.

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

[0102] It can be seen that as the mover moves forward, the number S of the main sensorN It rises step by step continuously, and the number of coupled sensors Count gradually increases. Then it enters the fully coupled region and alternates between 9 and 10. Finally, it gradually decreases in the right region. And the position calculation starts only when the number of coupled sensors Count ≥ 5. The angle Angle of the main sensor M shows a periodic sawtooth wave, and there are negative jumps in the continuously increasing positions spliced out.

[0103] The compensation amount Comp0 is calculated in the left region and the middle region, and the compensation amount Comp1 is calculated in the right region. Let θ0 and θ1 be 180° and 220° respectively. Calculate the compensated position Pos f , and the experimental results obtained are as Figure 7 shown. 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 requirements of the invention design.

[0104] Although the present invention has been 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. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed, as long as they do not depart from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the different dependent claims and the features described herein can be combined in a manner different from that described in the original claims. It should also be understood that the features described in connection with a single embodiment can 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; 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: 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; 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 varies between P+1 and P+2, where P is the number of permanent magnet poles; the serial number of the main sensor S N Determined by S1; The initial value of the current absolute position of the actuator is expressed as Pos: Pos=S N * +Angle M * / 360, In the formula is the pole distance, Angle M Main sensor S N Angle readings of 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.

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 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 :

6. The full-stroke linear absolute position detection method according to claim 5, characterized in that: Count = S1 - S0 + 1; 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 final detection position of the mover Pos f for: Pos f =S N * +Angle M * / 360+Comp0+Comp1。

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