Serial encoder feedback position estimation method and servo system

Abstract

The invention provides a serial encoder feedback position pre-estimation method and a servo control system, and the method comprises the steps: if a servo driver does not receive encoder return position data or the return detection fails, determining that the encoder return position data is not received; if yes, acquiring a current period motor target position, a previous period encoder single-circle position, and motor target positions and actual feedback positions in the previous two periods; calculating a theoretical position increment according to the motor target position of the current period and the motor target position of the previous period, and calculating a position deviation average value according to the motor target positions of the previous two periods and an actual feedback position; calculating a theoretical feedback position increment based on the theoretical position increment and the position deviation average value; and according to the theoretical feedback position increment and the single-circle position of the encoder in the previous period, judging the forward rotation or reverse rotation state of the motor, and estimating the feedback position of the encoder in the current period. According to the scheme, the feedback position of the encoder can be accurately estimated, accurate control over the servo motor is guaranteed, and the problems of motor speed shaking, motor abnormal sound and the like are prevented.

Description

Technical Field

[0001] The invention belongs to the technical field of servo control, and in particular relates to a serial encoder feedback position estimation method and a servo system. Background Art

[0002] In the motor servo control system, in order to achieve higher position accuracy and more precise absolute positioning, an absolute photoelectric encoder is usually used as a position feedback sensor. However, since the absolute encoder has a large number of output bits, in order to enhance the reliability of information transmission, the encoding information is generally output in serial mode and controlled by a specific communication protocol.

[0003] Serial communication may be interfered when used in an actual industrial environment, resulting in CRC check errors. If the motor runs at a fast speed, even the position loss of one control cycle will cause a large deviation in the control output, resulting in speed fluctuations and abnormal noise when the motor runs. Summary of the invention

[0004] In view of this, an embodiment of the present invention provides a serial encoder feedback position estimation method and servo system, which are used to solve the problem that when there is communication interference in the encoder, it will cause a large deviation in motor control, which will further cause speed fluctuations and abnormal noise during motor operation.

[0005] In a first aspect of an embodiment of the present invention, a method for estimating a serial encoder feedback position is provided, comprising: If the servo drive does not receive the encoder return position data within the predetermined time or the return data verification fails, the motor target position of the current cycle, the encoder single-turn position of the previous cycle, and the motor target position and actual feedback position of the previous two cycles are obtained; The theoretical position increment is calculated based on the motor target position of the current cycle and the motor target position of the previous cycle, and the average position deviation is calculated based on the motor target position and the actual feedback position of the previous two cycles; Calculate the theoretical feedback position increment based on the theoretical position increment and the average value of the position deviation; According to the theoretical feedback position increment and the single-turn position of the encoder in the previous cycle, the forward or reverse rotation state of the motor is determined, and the encoder feedback position in the current cycle is estimated.

[0006] In a second aspect of an embodiment of the present invention, a servo system is provided, comprising: The encoder is used to obtain the position of the servo motor and feed back the motor position data to the servo driver; A servo driver is used to receive the position data returned by the encoder and drive the servo motor; And, when the servo drive does not receive the encoder return position data within a predetermined time or the return data verification fails, the motor target position of the current cycle, the encoder single-turn position of the previous cycle, and the motor target position and actual feedback position of the previous two cycles are obtained; the theoretical position increment is calculated according to the motor target position of the current cycle and the motor target position of the previous cycle, and the position deviation average value is calculated according to the motor target position and the actual feedback position of the previous two cycles, and the theoretical feedback position increment is calculated based on the theoretical position increment and the position deviation average value; the motor forward or reverse state is judged according to the theoretical feedback position increment and the encoder single-turn position of the previous cycle, and the encoder feedback position of the current cycle is estimated; The servo motor is used to receive the drive of the servo driver and operate.

[0007] In a third aspect of an embodiment of the present invention, an electronic device is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method described in the first aspect of the embodiment of the present invention when executing the computer program.

[0008] In a fourth aspect of an embodiment of the present invention, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the method provided in the first aspect of the embodiment of the present invention are implemented.

[0009] In an embodiment of the present invention, when the encoder position feedback fails, the encoder feedback position of the current cycle is estimated, so as to avoid the problems of large control output deviation, speed fluctuation and abnormal motor noise when there is interference in the encoder serial communication. It can not only achieve accurate estimation of the feedback position, but also ensure precise control of the servo motor and prevent motor speed jitter and motor abnormal noise. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 creative work.

[0011] Figure 1 A schematic diagram of the structure of a servo system provided by an embodiment of the present invention; Figure 2 A schematic flow chart of a method for estimating a position of a serial encoder feedback provided by an embodiment of the present invention; Figure 3 A velocity feedback waveform before position estimation provided by one embodiment of the present invention; Figure 4A velocity feedback waveform after position estimation provided by one embodiment of the present invention; Figure 5 Another structural schematic diagram of a servo system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0012] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below 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.

[0013] It should be understood that the term "including" and other similar expressions in the specification or claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions, such as a process, method, system, or device including a series of steps or units is not limited to the listed steps or units. In addition, "first" and "second" are used to distinguish different objects, not to describe a specific order.

[0014] It is understandable that Figure 1 As shown in the figure, the servo system is generally composed of a servo drive, a servo motor, an encoder, a power line and an encoder cable. The servo drive is used to drive the servo motor. The encoder is a sensor installed on the servo motor to measure the magnetic pole position and the servo motor's rotation angle and speed. The encoder can feed back the motor position data to the servo drive according to the servo drive reading instruction. The servo drive can achieve precise control of the motor based on the position feedback signal. The CLK signal can be used for clock synchronization in the position reading of the servo drive, and the position data DATA is returned.

[0015] Communication interference is unavoidable during the actual use of the encoder. When the interference only lasts for 1-2 control cycles, if the drive is to not fail and shut down directly but to be able to run continuously and stably, it is necessary to estimate the motor feedback position so that the servo motor can meet normal control requirements when communication interference occurs.

[0016] See also Figure 2 , a flow chart of a serial encoder feedback position estimation method provided by an embodiment of the present invention includes: S201, if the servo driver does not receive the encoder return position data within a predetermined time or the return data verification fails, then obtain the motor target position of the current cycle, the encoder single-turn position of the previous cycle, and the motor target position and actual feedback position of the previous two cycles; The controller sends control instructions to the servo drive, and the servo drive executes the instructions to request the encoder to read the motor position data. When the encoder passes the verification, the motor position data will be fed back to the servo drive. When there is communication interference, the servo drive will not be able to receive the position data returned by the encoder within the predetermined time or the returned data verification fails (such as CRC verification), and the feedback position needs to be estimated.

[0017] The encoder data is read and verified using the Tamagawa protocol, the command frame is to read multiple turns + position, the transmission uses the SCI (Serial Communication Interface) protocol, and the baud rate uses 115200bps to minimize transmission delay.

[0018] The motor target position refers to the planned position of the motor within the control cycle, and the actual feedback position refers to the position fed back by the encoder within the control cycle. Before communication failure or communication interference occurs, the register can record the target position and actual feedback position of the previous two control cycles, as well as the single-turn position of the encoder in the previous cycle.

[0019] S202, calculating a theoretical position increment according to the motor target position of the current cycle and the motor target position of the previous cycle, and calculating a position deviation average value according to the motor target position and the actual feedback position of the previous two cycles; The theoretical motor position increment can be calculated based on the difference between the motor target position of the current cycle and the motor target position of the previous cycle. The motor target position of the previous cycle is also the given position of the previous cycle, which can be used as the base value for position estimation. The average value of the position deviation can be obtained based on the average value of the difference between the motor target position and the actual feedback position of the previous two cycles.

[0020] Specifically, the theoretical position increment of the motor is calculated according to formula (1): ; (1) In the formula, represents the theoretical position increment, Indicates the target position of the current cycle. Indicates the motor target position in the previous cycle; The average position deviation is calculated according to formula (2): ; (2) In the formula, represents the average position deviation, Indicates the motor target position in the previous cycle, that is, the motor target position in the previous cycle relative to the current cycle. Indicates the motor target position in the previous two cycles, Indicates the actual feedback position of the previous cycle, Indicates the actual feedback position in the previous two cycles.

[0021] S203, calculating a theoretical feedback position increment based on the theoretical position increment and the position deviation average value; The theoretical feedback position increment can be calculated based on the sum of the theoretical position increment and the average value of the position deviation.

[0022] Specifically, the theoretical feedback position increment is calculated according to formula (3): ; (3) In the formula, represents the theoretical feedback position increment, Theoretical position increment, Represents the average value of position deviation.

[0023] S204, judging the forward or reverse rotation state of the motor according to the theoretical feedback position increment and the single-turn position of the encoder in the previous cycle, and estimating the encoder feedback position in the current cycle.

[0024] The forward and reverse rotation of the motor can be determined based on the theoretical feedback position increment, and whether the motor has passed the forward rotation pole or reverse rotation zero point can be determined based on the theoretical feedback position increment and the encoder single-turn position of the previous cycle. The encoder single-turn position of the previous cycle can be derived from the single-turn position obtained by encoder feedback, or from the single-turn position calculated after position estimation. The forward rotation state of the motor can include passing the pole point and not passing the pole point, and the reverse rotation state of the motor can include passing the zero point and not passing the zero point.

[0025] Specifically, when the theoretical feedback position increment Greater than 0 and theoretical feedback position increment Plus one cycle encoder single turn position If the encoder resolution is less than R, the motor is judged to not exceed the forward rotation limit, and the encoder feedback position in the current cycle is for: ; When the theoretical feedback position increment Greater than 0 and theoretical feedback position increment Plus one cycle encoder single turn position If the value is greater than or equal to the encoder resolution R, it is determined that the motor has rotated forward past the pole point, and the encoder feedback position in the current cycle for: ; When the theoretical feedback position increment Less than 0 and theoretical feedback position increment Plus one cycle encoder single turn position If it is greater than 0, it is determined that the motor reverses but does not pass the zero point, and the encoder feedback position in the current cycle for: ; When the theoretical feedback position increment Less than 0 and theoretical feedback position increment Plus one cycle encoder single turn position If it is less than or equal to 0, it is determined that the motor reverses and crosses the zero point, and the encoder feedback position in the current cycle for: .

[0026] Optionally, based on the motor target position of the current cycle, the encoder feedback position estimated in the current cycle, and the PID controller proportional coefficient, the output of the position loop in the servo drive is calculated according to formula (4): ; (4) In the formula, Represents the output of the position loop, represents the proportional coefficient of the PID controller, Indicates the target position of the motor in the current cycle. Indicates the encoder feedback position estimated in the current cycle.

[0027] It can be understood that the servo control system generally samples three loops of control, namely the position loop, the speed loop and the current loop. The three loops are set by the servo, and the feedback is obtained by the encoder on the motor. The input of the position loop is an external pulse (usually, the servo that directly writes data to the driver address is an exception). The external pulse is processed by smoothing and filtering and the electronic gear is calculated as the "position loop setting". The setting and the pulse signal from the encoder feedback are calculated by the deviation counter. After the PID adjustment of the position loop (proportional gain adjustment, no integral differential link), the sum of the output and the position given feedforward signal constitutes the speed loop setting. The feedback of the position loop usually comes from the encoder. This application can estimate the position feedback when the encoder feedback is abnormal. The encoder is installed at the servo motor and the tail. It has no connection with the current loop. It samples from the rotation of the motor and has no connection with the input, output, and feedback of the current loop. The current loop is formed inside the driver. The position command is input from the outermost position loop. After position trajectory planning, a position control command is generated in each control cycle. The speed command input of the speed loop is calculated using the deviation between the position command and the position feedback. The current loop input is calculated through the given and feedback in the speed loop.

[0028] In some embodiments, when the encoder communication is abnormal, the speed feedback waveform before adding the position estimation and the speed feedback waveform after adding the position estimation are respectively as follows: Figure 3 , Figure 4 As shown, the test condition is given as 1000rpm, Figure 3 CH2 is the speed feedback waveform without position estimation. Figure 4CH2 in the figure is the speed feedback waveform after adding position estimation. It can be seen that after adding position estimation, the spike burrs of speed feedback are significantly reduced and the amplitude is reduced. There is no abnormal sound when actually observing the motor running.

[0029] In this embodiment, when there is communication interference in the servo motor serial encoder, the feedback position can be accurately estimated by adopting feedback position estimation, thereby achieving precise control of the servo motor and preventing problems such as motor speed jitter and motor abnormal noise due to feedback fluctuations.

[0030] It should be understood that the sequence numbers of the steps in the above embodiments do not imply a sequence of execution, and the execution sequence of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0031] Figure 5 A schematic diagram of the structure of a servo system using the serial encoder feedback position estimation method provided by an embodiment of the present invention, the system comprising: The encoder 510 is used to obtain the position of the servo motor and feed back the motor position data to the servo driver; A servo driver 520 is used to receive the position data returned by the encoder and drive the servo motor; And, when the servo drive does not receive the encoder return position data within a predetermined time or the return data verification fails, the motor target position of the current cycle, the encoder single-turn position of the previous cycle, and the motor target position and actual feedback position of the previous two cycles are obtained; the theoretical position increment is calculated according to the motor target position of the current cycle and the motor target position of the previous cycle, and the position deviation average value is calculated according to the motor target position and the actual feedback position of the previous two cycles, and the theoretical feedback position increment is calculated based on the theoretical position increment and the position deviation average value; the motor forward or reverse state is judged according to the theoretical feedback position increment and the encoder single-turn position of the previous cycle, and the encoder feedback position of the current cycle is estimated; The theoretical position increment of the motor is calculated according to formula (1): ; (1) In the formula, represents the theoretical position increment, Indicates the target position of the current cycle. Indicates the motor target position in the previous cycle; The average position deviation is calculated according to formula (2): ; (2) In the formula, represents the average position deviation, Indicates the motor target position in the previous cycle, Indicates the motor target position in the previous two cycles, Indicates the actual feedback position of the previous cycle, Indicates the actual feedback position in the previous two cycles; The theoretical feedback position increment is calculated according to formula (3): ; (3) In the formula, represents the theoretical feedback position increment, Theoretical position increment, Represents the average value of position deviation.

[0032] Specifically, judging the forward or reverse rotation state of the motor according to the theoretical feedback position increment and the single-turn position of the encoder in the previous cycle, and estimating the encoder feedback position in the current cycle includes: When the theoretical feedback position increment Greater than 0 and theoretical feedback position increment Plus one cycle encoder single turn position If the encoder resolution is less than R, the motor is judged to not exceed the forward rotation limit, and the encoder feedback position in the current cycle is for: ; When the theoretical feedback position increment Greater than 0 and theoretical feedback position increment Plus one cycle encoder single turn position If the value is greater than or equal to the encoder resolution R, it is determined that the motor has rotated forward past the pole point, and the encoder feedback position in the current cycle for: ; When the theoretical feedback position increment Less than 0 and theoretical feedback position increment Plus one cycle encoder single turn position If it is greater than 0, it is determined that the motor reverses but does not pass the zero point, and the encoder feedback position in the current cycle for: ; When the theoretical feedback position increment Less than 0 and theoretical feedback position increment Plus one cycle encoder single turn position If it is less than or equal to 0, it is determined that the motor reverses and crosses the zero point, and the encoder feedback position in the current cycle for: .

[0033] Optionally, based on the motor target position of the current cycle, the encoder feedback position estimated in the current cycle, and the PID controller proportional coefficient, the output of the position loop in the servo drive is calculated according to formula (4): ; (4) In the formula, Represents the output of the position loop, represents the proportional coefficient of the PID controller, Indicates the target position of the motor in the current cycle. Indicates the encoder feedback position estimated in the current cycle.

[0034] The servo motor 530 is used to receive the drive of the servo driver and operate.

[0035] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described systems and modules can refer to the corresponding processes in the aforementioned method embodiments, and will not be repeated here.

[0036] Those skilled in the art can understand that all or part of the steps in the above-mentioned embodiment method can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it implements part or all of the processes in steps S101 to S104. The storage medium includes ROM / RAM, etc. In the above-mentioned embodiments, the description of each embodiment has its own emphasis. For the part that is not described or recorded in detail in a certain embodiment, please refer to the relevant description of other embodiments.

[0037] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0038] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for estimating position of a serial encoder feedback, characterized in that: include: If the servo drive does not receive the encoder return position data within the predetermined time or the return data verification fails, the motor target position of the current cycle, the encoder single-turn position of the previous cycle, and the motor target position and actual feedback position of the previous two cycles are obtained; The theoretical position increment is calculated based on the motor target position of the current cycle and the motor target position of the previous cycle, and the average position deviation is calculated based on the motor target position and the actual feedback position of the previous two cycles; Calculate the theoretical feedback position increment based on the theoretical position increment and the average value of the position deviation; According to the theoretical feedback position increment and the single-turn position of the encoder in the previous cycle, the forward or reverse rotation state of the motor is determined, and the encoder feedback position in the current cycle is estimated.

2. The method according to claim 1, characterized in that The method of calculating the theoretical position increment according to the motor target position of the current cycle and the motor target position of the previous cycle, and calculating the position deviation average value according to the motor target position and the actual feedback position of the previous two cycles includes: Calculate the motor theoretical position increment according to formula (1): ;（1） In the formula, represents the theoretical position increment, Indicates the target position of the current cycle. Indicates the motor target position in the previous cycle; The average position deviation is calculated according to formula (2): ;（2） In the formula, represents the average position deviation, Indicates the motor target position in the previous cycle, Indicates the motor target position in the previous two cycles, Indicates the actual feedback position of the previous cycle, Indicates the actual feedback position in the previous two cycles.

3. The method according to claim 1, characterized in that The calculation of the theoretical feedback position increment based on the theoretical position increment and the position deviation average value comprises: The theoretical feedback position increment is calculated according to formula (3): ;（3） In the formula, represents the theoretical feedback position increment, Theoretical position increment, Represents the average value of position deviation.

4. The method according to claim 1, characterized in that: The step of judging the forward or reverse rotation state of the motor according to the theoretical feedback position increment and the single-turn position of the encoder in the previous cycle, and estimating the encoder feedback position in the current cycle includes: When the theoretical feedback position increment Greater than 0 and theoretical feedback position increment Plus one cycle encoder single turn position If the encoder resolution is less than R, the motor is judged to not exceed the forward rotation limit, and the encoder feedback position in the current cycle is for: ; When the theoretical feedback position increment Greater than 0 and theoretical feedback position increment Plus one cycle encoder single turn position If the value is greater than or equal to the encoder resolution R, it is determined that the motor has rotated forward past the pole point, and the encoder feedback position in the current cycle for: ; When the theoretical feedback position increment Less than 0 and theoretical feedback position increment Plus one cycle encoder single turn position If it is greater than 0, it is determined that the motor reverses but does not pass the zero point, and the encoder feedback position in the current cycle for: ; When the theoretical feedback position increment Less than 0 and theoretical feedback position increment Plus one cycle encoder single turn position If it is less than or equal to 0, it is determined that the motor reverses and crosses the zero point, and the encoder feedback position in the current cycle for: .

5. The method according to claim 1, characterized in that: The step of judging the forward or reverse rotation state of the motor according to the theoretical feedback position increment and the single-turn position of the encoder in the previous cycle, and estimating the encoder feedback position in the current cycle also includes: Based on the motor target position in the current cycle, the encoder feedback position estimated in the current cycle, and the PID controller proportional coefficient, the output of the position loop in the servo drive is calculated according to formula (4): ;（4） In the formula, Represents the output of the position loop, represents the proportional coefficient of the PID controller, Indicates the target position of the motor in the current cycle. Indicates the encoder feedback position estimated in the current cycle.

6. A servo system using the serial encoder feedback position estimation method as claimed in claim 1, characterized in that: include: The encoder is used to obtain the position of the servo motor and feed back the motor position data to the servo driver; A servo driver is used to receive the position data returned by the encoder and drive the servo motor; And, when the servo driver does not receive the encoder return position data within a predetermined time or the return data verification fails, the motor target position of the current cycle, the encoder single-turn position of the previous cycle, and the motor target position and actual feedback position of the previous two cycles are obtained; The theoretical position increment is calculated according to the motor target position of the current cycle and the motor target position of the previous cycle, and the position deviation average value is calculated according to the motor target position and the actual feedback position of the previous two cycles, and the theoretical feedback position increment is calculated based on the theoretical position increment and the position deviation average value; according to the theoretical feedback position increment and the single-turn position of the encoder in the previous cycle, the forward or reverse state of the motor is judged, and the encoder feedback position of the current cycle is estimated; The servo motor is used to receive the drive of the servo driver and operate.

7. The system according to claim 6, characterized in that The step of judging the forward or reverse rotation state of the motor according to the theoretical feedback position increment and the single-turn position of the encoder in the previous cycle, and estimating the encoder feedback position in the current cycle includes: When the theoretical feedback position increment Greater than 0 and theoretical feedback position increment Plus one cycle encoder single turn position If the encoder resolution is less than R, the motor is judged to not exceed the forward rotation limit, and the encoder feedback position in the current cycle is for: ; When the theoretical feedback position increment Greater than 0 and theoretical feedback position increment Plus one cycle encoder single turn position If the value is greater than or equal to the encoder resolution R, it is determined that the motor has rotated forward past the pole point, and the encoder feedback position in the current cycle for: ; When the theoretical feedback position increment Less than 0 and theoretical feedback position increment Plus one cycle encoder single turn position If it is greater than 0, it is determined that the motor reverses but does not pass the zero point, and the encoder feedback position in the current cycle for: ; When the theoretical feedback position increment Less than 0 and theoretical feedback position increment Plus one cycle encoder single turn position If it is less than or equal to 0, it is determined that the motor reverses and crosses the zero point, and the encoder feedback position in the current cycle for: .

8. The system according to claim 6, characterized in that The step of judging the forward or reverse rotation state of the motor according to the theoretical feedback position increment and the single-turn position of the encoder in the previous cycle, and estimating the encoder feedback position in the current cycle also includes: Based on the motor target position in the current cycle, the encoder feedback position estimated in the current cycle, and the PID controller proportional coefficient, the output of the position loop in the servo drive is calculated according to formula (4): ;（4） In the formula, Represents the output of the position loop, represents the proportional coefficient of the PID controller, Indicates the target position of the motor in the current cycle. Indicates the encoder feedback position estimated in the current cycle.

9. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of a serial encoder feedback position estimation method as described in any one of claims 1 to 5 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed, the steps of a serial encoder feedback position estimation method as described in any one of claims 1 to 5 are implemented.

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