Automatic zero searching method for brushless servo motor

Abstract

The invention provides an automatic zero searching method for a brushless servo motor, and belongs to the technical field of embedding, the automatic zero searching method for the brushless servo motor depends on an SvPWM brushless servo control algorithm, a corresponding PWM signal is given to the motor through software, the brushless servo motor is driven to automatically deflect, and zero searching is carried out on the brushless servo motor. Whether the current output is an expected value or not is judged according to a value fed back by the angle sensor, and the zero position can be found out by software after several rounds of attempts. According to the method, the servo parameters do not need to be manually collected and measured before the servo product is assembled, zero position automatic calibration is carried out after the finished product is finished, the zero position calibration efficiency of the servo motor and the product assembling efficiency can be greatly improved, and later maintenance of the finished product is also facilitated.

Description

Technical Field

[0001] The invention belongs to the field of embedded technology, and more specifically, relates to a method for automatically finding zero of a brushless servo motor. Background Art

[0002] The polarity and zero position of different products of the servo system's position markers are inconsistent due to factors such as installation angle and structural accuracy. The current method for finding the zero position of the frame is manual: that is, when the motor is disabled, manually rotate the frame and record the positive pitch limit. Negative pitch limit Positive azimuth limit (ψ lim+ ), negative azimuth limit (ψ lim- ), the pitch zero position is: Azimuth zero position is: ψ0=(ψ lim+ +ψ lim- ) / 2.

[0003] For brushless motors, the commutation time must be known, so the rotor zero position must be found. The method is: U phase power supply +, V phase and W phase are connected to the power supply ground, the rotor will be fixed at a certain angle, and the position of the rotor at this time is the rotor mechanical zero position, recorded as θ M0 The rotor electrical zero position is θ E0 =P*θ M0 , P is the number of magnetic pole pairs.

[0004] With the frame zero position, rotor mechanical zero position, and rotor electrical zero position, SvPWM brushless servo control can be performed. However, the above method requires that the product must be in a loose state, the frame can be manually rotated, the angle sensor information can be recorded, and a special tooling cable is required to manually power the brushless motor and record the rotor angle, which affects the efficiency of product assembly, and the finished product parameters need to be disassembled for later correction, which is not conducive to maintenance. Summary of the invention

[0005] The purpose of the present invention is to provide a method for automatic zeroing of a brushless servo motor, which can eliminate the need for manual participation in the collection and measurement of servo parameters before the servo product is assembled, and automatically calibrate the zero position after the product is finished, which can greatly improve the efficiency of the servo motor zero position calibration and the efficiency of product assembly, and is also convenient for the maintenance of the finished product at a later stage.

[0006] To achieve the above object, the present invention provides a method for automatically finding zero of a brushless servo motor, comprising the following steps:

[0007] Step 1: Input PWM signals to the U, V, and W phases of the motor, and obtain the motor's rotor mechanical zero position θ after the angle sensor output stabilizes. M0 ;

[0008] Step 2: Apply the first driving voltage to the motor and perform servo control according to the SvPWM algorithm to make the motor frame, and obtain the first limit angle of the motor after the motor deflection is stable;

[0009] Step 3: Apply the second driving voltage to the motor and perform servo control according to the SvPWM algorithm to make the motor rotate in the reverse direction to frame, and obtain the second limit angle of the motor after the motor deflection is stable; the second driving voltage = - the first driving voltage;

[0010] Step 4: If X1° ≤ |first limit angle - second limit angle| ≤ X2°, it means that the motor frames in both deflections, and the current motor is of positive polarity, then jump to Step 5; if |first limit angle - second limit angle| < X1°, then the current motor is of negative polarity, and jump to Step 2; if |first limit angle - second limit angle| > X2°, and X1° ≤ |first limit angle - second limit angle - 360°| ≤ X2° or X1° ≤ |first limit angle - second limit angle + 360°| ≤ X2°, then the current motor is of positive polarity, and jump to Step 5, otherwise the current motor is of negative polarity, and jump to Step 2; X1° is 95% - 98% of the angle between the motor and the limiter, and X2° is the angle between the motor and the limiter;

[0011] Step 5: Calculate the motor frame zero position = (first limit angle + second limit angle) / 2;

[0012] Step 6: Calculate the motor rotor zero position = (θ M0 - motor frame zero position) * Polar, where Polar = 1 or -1.

[0013] Further: Input PWM signals with duty cycles of 10 - 90%, 0%, 0% to the U, V, W phases of the pitch motor, and input PWM signals with duty cycles of 0%, 0%, 0% to the U, V, W phases of the azimuth motor to obtain the rotor mechanical zero position θ M0 。

[0014] Further, Step 1 includes the following steps: Input PWM signals with duty cycles of 10 - 90%, 0%, 0% to the U, V, W phases of the azimuth motor, and input PWM signals with duty cycles of 0%, 0%, 0% to the U, V, W phases of the pitch motor to obtain the rotor mechanical zero position θ M0 。

[0015] Further, input a PWM signal with a duty cycle of 40 - 50% to the U phase of the pitch motor.

[0016] Further, input a PWM signal with a duty cycle of 40 - 50% to the U phase of the azimuth motor.

[0017] Further, Step 2 includes the following steps:

[0018] Give the pitch motor the first drive voltage U q_p , give the azimuth motor drive voltage U q_y =0, then Where: θ p =P*(θ M -θ M0 ), θ M is the real-time angle of the pitch motor, θ M0 is the mechanical zero position of the pitch motor rotor, and P is the number of magnetic pole pairs.

[0019] Furthermore, the step 2 comprises the following steps:

[0020] Give the azimuth motor the first drive voltage U q_y , give the pitch motor drive voltage U q_p =0, then Where: θ y =P*(θ M -θ M0 ), θ M is the real-time angle of the azimuth motor, θ M0 is the mechanical zero position of the azimuth motor rotor, and P is the number of magnetic pole pairs.

[0021] Furthermore, the first driving voltage is 20% to 50% of the supply voltage of the DC motor.

[0022] Compared with the prior art, the present invention has the following technical effects:

[0023] The invention discloses a method for automatically finding zero position of a brushless servo motor, which relies on the SvPWM brushless servo control algorithm, uses software to give the motor a corresponding PWM signal, drives the brushless servo motor to automatically deflect, and determines whether the current output is the expected value according to the value fed back by the angle sensor. The software can find the zero position after several rounds of attempts. The method of the invention uses software program to replace manual calibration, which is more efficient and more convenient for finished product maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0025] Figure 1 A diagram showing the relationship between the αβ coordinate system and sector division provided in an embodiment of the present invention;

[0026] Figure 2A flowchart of a method for automatic zeroing of a brushless servo motor provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0028] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. The singular forms "a", "said" and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0029] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. For example, without departing from the scope of the embodiments of the present invention, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0030] In view of the inconvenience of the existing homing method of a brushless servo motor, an embodiment of the present invention provides a method for automatically homing a brushless servo motor.

[0031] The embodiment of the present invention uses software to issue a corresponding PWM signal to the motor to drive the brushless servo motor to automatically deflect. Since the zero position required for the drive signal has not been measured, the signal needs to be output tentatively, and the value fed back by the angle sensor is used to determine whether the current output is the expected value. The software can find the zero position after several rounds of attempts, store it in the on-chip Flash, and restart the device to enable it.

[0032] A method for automatically finding zero of a brushless servo motor according to an embodiment of the present invention comprises the following steps:

[0033] (1) Obtaining the mechanical zero position and electrical zero position of the motor rotor: Input PWM signals to the U, V, and W phases of the motor. Generally, the U, V, and W phases of the motor input PWM signals with duty cycles of 10-90%, 0%, and 0% in sequence. The rotor will be fixed at a certain angle. At this time, the position of the rotor is the mechanical zero position of the rotor, which is recorded as θ M0 , then the rotor electrical zero position is θ E0 =P*θ M0 , P is the number of magnetic pole pairs.

[0034] (2) Obtaining the frame zero position of the motor rotor: driving the motor to rotate to the limit angle, commonly known as framing. The limit angle is generally limited by a limiter or structural member, including the following steps:

[0035] 1) According to the principle of FOC (Field-Oriented Control) brushless motor control algorithm, to drive the motor to rotate, a quadrature axis voltage U is required q (U q The voltage can be taken as 20% to 50% of the DC motor supply voltage to make the motor generate torque). At this time, the voltage is in the dq coordinate system and needs to be converted to the αβ coordinate system. α =U q sinθ、U β =U q cosθ, such as Figure 1 As shown, θ is the electrical angle between the actual rotor position and the rotor zero position (the relationship between the electrical angle and the mechanical angle is: mechanical angle * P = electrical angle). At this time, θ = (actual value of the angle sensor - θ M0 )×P.

[0036] 2) Determine the sector where the voltage is located based on the control voltage in the αβ coordinate system.

[0037] 3) Calculate the conduction time of the basic voltage space vector in the sector, divide it by the PWM control period to get the duty cycle, and the motor is framed. After the motor deflection is stable, the first limit angle of the motor frame can be obtained;

[0038] 4) Give the motor a reverse quadrature axis voltage U q , drive the motor to rotate in the opposite direction, the motor frames, and after the motor deflection stabilizes, the second limit angle of the motor frames can be obtained;

[0039] 5) Based on the obtained first limit angle and second limit angle of the motor frame, the motor frame zero position can be calculated, and the motor rotor zero position can be further calculated.

[0040] The above steps 1)-4) are the SvPWM brushless servo control algorithm. Since the polarity of the angle sensor cannot be determined by the tooling, the frame punching process cannot be completed in one step. This step is tentative and can be completed at most twice. The frame zero position can be obtained after punching up and down or left and right.

[0041] The following is an example of a method for automatic zeroing of a brushless servo motor according to an embodiment of the present invention. The method is based on an embedded servo platform, and the specific steps are as follows:

[0042] The method of automatic zeroing of the pitch motor is as follows: Figure 2 As shown, the following steps are included:

[0043] Step 1: Input PWM signals with a duty cycle of 40%, 0%, and 0% to the U, V, and W phases of the pitch motor, and input PWM signals with a duty cycle of 0%, 0%, and 0% to the U, V, and W phases of the azimuth motor. At this time, the pitch motor will deflect and produce a certain amount of oscillation. After the output of the angle sensor stabilizes (i.e., after 3s), record the rotor mechanical zero position θ of the pitch motor. M0 (i.e. the current output value of the pitch angle sensor).

[0044] Step 2: Software setting of the pitch motor drive voltage U q_p =7(U q_p The unit is V, the DC motor supply voltage is 28v), the azimuth motor drive voltage is U q_y = 0, eliminate the interference of the azimuth motor and ensure that the current pitch motor moves up and down. Where: θ p =P*(θ M -θ M0 ), θ M is the real-time angle of the pitch motor, θ M0 is the mechanical zero position of the pitch motor rotor, P is the number of magnetic pole pairs, and the control is performed according to the SvPWM algorithm. After the pitch motor deflection is stable (i.e. after 3s), the angle of the pitch motor is recorded. If the current pitch motor polarity is correct, the box will be checked, otherwise it will not be checked. M You need to multiply the real-time angle of the pitch motor by -1.

[0045] Step 3: Software setting of pitch motor drive voltage U q_p =-7, U q_y =0, repeat step 2, perform servo control according to the SvPWM algorithm, make the pitch motor rotate in the opposite direction to make a frame, and record the angle of the pitch motor

[0046] Step 4: If The value of X1° is 95% to 98% of the angle between the pitch motor and the upper and lower limiters, and the value of X2° is the angle between the pitch motor and the upper and lower limiters. This means that both deflections are framed, and the current pitch motor is positive polarity. Jump to step 5. If The current pitch motor is negative polarity, jump to step 2. This indicates that the angle sensor has zero crossing and needs 360° compensation. or If one of the conditions is met, it means that the pitch motor is in the frame, jump to step 5, otherwise the pitch motor is negative polarity, jump to step 2.

[0047] Step 5: Calculate the Pitch Motor Frame Zero Position

[0048] Step 6: Calculate the final pitch motor rotor zero position: the positive polarity is Negative polarity is The subsequent SvPWM brushless servo control algorithm pitches the rotor position relative to this zero position.

[0049] Similarly, the method for automatically finding the zero position of the azimuth motor includes the following steps:

[0050] Step 1: Input PWM signals with a duty cycle of 40%, 0%, and 0% to the U, V, and W phases of the azimuth motor, and input PWM signals with a duty cycle of 0%, 0%, and 0% to the U, V, and W phases of the pitch motor. At this time, the azimuth motor will deflect and produce a certain amount of oscillation. After the output of the angle sensor stabilizes (i.e., after 3s), record the rotor mechanical zero position θ of the azimuth motor. M0 (i.e. the current output value of the azimuth angle sensor).

[0051] Step 2: Software setting of azimuth motor drive voltage U q_y =7(U q_y The unit is V, the DC motor supply voltage is 28v), the pitch motor drive voltage is U q_p = 0, eliminate the interference of the pitch motor and ensure that the current azimuth motor is in the left and right frame. Where: θ y =P*(θ M -θ M0 ), θ M is the real-time angle of the azimuth motor, θ M0 is the mechanical zero position of the azimuth motor rotor, P is the number of magnetic pole pairs, and the azimuth motor is controlled according to the SvPWM algorithm. After the azimuth motor deflection stabilizes (i.e., after 3s), the angle ψ of the azimuth motor is recorded. lim+ =θ M If the current position motor polarity is correct, the box will be ticked, otherwise it will not. M The real-time angle of the azimuth motor needs to be multiplied by -1.

[0052] Step 3: Software Setup q_y =-7, U q_p =0, repeat step 2, perform servo control according to the SvPWM algorithm, make the azimuth motor rotate in the opposite direction to make a frame, and record the angle ψ of the azimuth motor lim- .

[0053] Step 4: If X1°≤|ψ lim+ -ψ lim- |≤X2°, X1° is 95% to 98% of the angle between the azimuth motor and the left and right limiters, and X2° is the angle between the azimuth motor and the left and right limiters, which means that both deflections are framed, and the current azimuth motor is positive polarity. Jump to step 5. If |ψ lim+ -ψ lim-|<1X°, the current azimuth motor is negative polarity, jump to step 2. lim+ -ψ lim -|>X2°, it means that the angle sensor has zero crossing and 360° compensation is required, specifically X1°≤|ψ lim+ -ψ lim --360°|≤X2°orX1°≤|ψ lim+ -ψ lim- +360°|≤X2°, if one of the conditions is met, it means the frame is ticked, jump to step 5, otherwise the azimuth motor is negative polarity, jump to step 2.

[0054] Step 5: Calculate the zero position of the azimuth motor frame: ψ0 = (ψ lim+ +ψ lim- ) / 2.

[0055] Step 6: Calculate the final azimuth motor rotor zero position: positive polarity is y R0 =θ M0 -ψ0, negative polarity is y R0 =-(θ M0 -ψ0), the subsequent SvPWM brushless servo control algorithm azimuth rotor position is the relative position of this zero position.

[0056] A method for automatic zeroing of a brushless servo motor provided by an embodiment of the present invention replaces manual calibration with a program, so that there is no need for manual participation in the collection and measurement of servo parameters before the servo product is assembled. Automatic zero position calibration is performed after the product is finished, which can greatly improve the efficiency of zero position calibration and product assembly efficiency, and is also convenient for the maintenance of the finished product at a later stage.

[0057] The embodiment of the present invention provides a method for automatic zeroing of a brushless servo motor based on an embedded servo platform. When the control parameters (i.e., motor rotor zero position) required by the SvPWM brushless servo control algorithm are incomplete, the software uses a tentative input, judges the correctness of the input based on the output feedback, and finally determines the accurate servo parameters, including determining the servo motor polarity, motor frame zero position, and motor rotor zero position, thereby completing precise SvPWM control. The method of the present invention is applicable to all SvPWM servo control platforms.

[0058] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the attached claims.

Claims

1. A method for automatic zeroing of a brushless servo motor, characterized in that: Including the following steps: Step 1: Input PWM signals to the U, V, and W phases of the motor, and obtain the motor's rotor mechanical zero position θ after the angle sensor output stabilizes. M0 ; Step 2: Apply a first driving voltage to the motor and perform servo control according to the SvPWM algorithm to make the motor frame, and obtain the first limit angle of the motor after the motor deflection is stable; Step 3: Apply a second driving voltage to the motor and perform servo control according to the SvPWM algorithm to make the motor rotate in the reverse direction to frame, and obtain the second limit angle of the motor after the motor deflection is stable; the second driving voltage = - the first driving voltage; Step 4: If X1° ≤ |the first limit angle - the second limit angle| ≤ X2°, it means that the motor deflects and frames twice, and the current motor is of positive polarity, then jump to Step 5; if |the first limit angle - the second limit angle| < X1°, then the current motor is of negative polarity, and jump to Step 2; if |the first limit angle - the second limit angle| > X2°, and X1° ≤ |the first limit angle - the second limit angle - 360°| ≤ X2° or X1° ≤ |the first limit angle - the second limit angle + 360°| ≤ X2°, then the current motor is of positive polarity, and jump to Step 5, otherwise the current motor is of negative polarity, and jump to Step 2; X1° is 95% - 98% of the included angle between the motor and the limiter, and X2° is the included angle between the motor and the limiter; Step 5: Calculate the motor frame zero position = (the first limit angle + the second limit angle) / 2; Step 6: Calculate the motor rotor zero position = (θ M0 - Motor frame zero position)*Polar, Polar=1 or -1.

2. A method for automatic zeroing of a brushless servo motor as claimed in claim 1, characterized in that: The step 1 comprises the following steps: inputting PWM signals with a duty cycle of 10-90%, 0%, 0% to the U, V, and W phases of the pitch motor, inputting PWM signals with a duty cycle of 0%, 0%, 0% to the U, V, and W phases of the azimuth motor, and obtaining the rotor mechanical zero position θ of the pitch motor. M0 .

3. A method for automatic zeroing of a brushless servo motor as claimed in claim 1, characterized in that: The step 1 comprises the following steps: inputting PWM signals with a duty cycle of 10-90%, 0%, 0% to the U, V, and W phases of the azimuth motor, inputting PWM signals with a duty cycle of 0%, 0%, 0% to the U, V, and W phases of the pitch motor, and obtaining the rotor mechanical zero position θ of the azimuth motor. M0 .

4. A method for automatic zeroing of a brushless servo motor as claimed in claim 2, characterized in that: Input a PWM signal with a duty cycle of 40 - 50% to the U phase of the pitch motor.

5. A method for automatic zeroing of a brushless servo motor as claimed in claim 3, characterized in that: Input a PWM signal with a duty cycle of 40 - 50% to the U phase of the azimuth motor.

6. A method for automatic zeroing of a brushless servo motor as claimed in claim 2, characterized in that: The said Step 2 includes the following steps: Give the pitch motor the first drive voltage U q_p , give the azimuth motor drive voltage U q_y =0, then Where: θ p =P*(θ M -θ M0 ), θ M is the real-time angle of the pitch motor, θ M0 is the mechanical zero position of the pitch motor rotor, and P is the number of magnetic pole pairs.

7. A method for automatic zeroing of a brushless servo motor as claimed in claim 3, characterized in that: The said Step 2 includes the following steps: Give the azimuth motor the first drive voltage U q_y , give the pitch motor drive voltage U q_p =0, then Where: θ y =P*(θ M -θ M0 ), θ M is the real-time angle of the azimuth motor, θ M0 is the mechanical zero position of the azimuth motor rotor, and P is the number of magnetic pole pairs.

8. A method for automatic zeroing of a brushless servo motor as claimed in any one of claims 1 to 7, characterized in that: The first driving voltage is 20% - 50% of the DC motor supply voltage.

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