Device and method for taking any point position as zero point in motor teaching

Abstract

The invention provides a device for taking any point position as a zero point in motor teaching and a method thereof, and belongs to the field of encoders. The device comprises a DDR motor, a DDR rotary table and an encoder, the resolution ratio of the encoder is Enc, the encoder is randomly placed in a single-loop position, the DDR rotary table is provided with a limiting column, the limiting column is used for single-loop position feedback, the DDR rotary table is provided with a teaching zero position Pb, and the teaching zero position Pb is latched through IO signals. The zero point is latched, different point position control requirements are met based on the zero point position, and after control is completed, the motor needs to return to zero with the shortest path on the basis of the current position.

Description

Technical Field

[0001] The present invention relates to the technical field of motor control, and in particular to a device and a method for teaching a motor to use any point as a zero point. Background Art

[0002] Direct-drive rotary motors (DDR) have the advantages of high torque and high mechanical precision, and are widely used in semiconductor, photovoltaic, medical and other industries. The encoder types used in DDR motors include incremental encoders and absolute encoders. After the incremental encoder is powered on, there is no fixed initial phase angle. Each time it is powered on, the initial phase angle learning needs to be completed, which is not suitable for occasions where absolute position is required. The absolute encoder used in DDR motors is currently the mainstream BissC protocol encoder. This type of encoder uses synchronous serial communication and has the advantages of high-speed data transmission and low cost. In DDR motor turntable applications, BissC protocol encoders have special advantages. For such occasions, the BissC protocol encoder motor needs to return to zero when powered on, and various point position controls are realized based on the zero position. The 35 types of zero return methods commonly used in the 402 protocol are mainly used in incremental encoder systems. For absolute encoders, there is no physical Z signal, and the only way to determine the single-circle zero point as Z is through absolute position. This method will have a large error when determining the single-circle zero point as Z due to different zero return speeds. The zero return method of the photoelectric switch is also limited by the actual application scenarios, so a zero return method that does not rely on the Z signal or photoelectric switch is needed.

[0003] For example, a Chinese invention patent discloses a robot zero-point calibration method and device [application number CN201611047078.4], comprising: obtaining the coarse positioning zero-point position of the robot axis after the zero-point position of the robot axis is lost; taking the coarse positioning zero-point position as the starting point, running the robot according to the original trajectory, and obtaining the first actual position of the robot axis after running; teaching the robot axis after running to the trajectory centering position, and obtaining the second actual position of the robot axis after teaching; fine-tuning the coarse positioning zero-point position according to the first actual position and the second actual position, and obtaining the zero-point position of the robot axis. However, the return to zero in this technical solution does not use the shortest path to return to zero, but returns to the zero point after a complete rotation. Summary of the invention

[0004] The present invention provides a device and method for teaching a motor to use any point as a zero point, so as to solve the problem that there is no Z signal in some occasions, no electric switch, and the movement range is limited, resulting in failure to return to zero.

[0005] To solve the above technical problems, the present application proposes a method for teaching any point of a motor as the zero point, including a DDR motor, a DDR turntable, an encoder, and a servo driver. The DDR turntable is equipped with a limit post due to special requirements of structure and process. The resolution of the encoder is Enc, and it is characterized in that: the encoder is an absolute encoder, and there is no special requirement for the power-on position of the motor, that is, the power-on position is random. The servo driver is used to teach any point of the DDR motor as the zero position and lock the zero offset. The present invention recombines the actual position of the limit post and the current position of the motor to recalculate the target position that the motor needs to run to return to the zero position, and realizes returning to zero with the shortest path. Returning to zero with the shortest path is the key point of this patent.

[0006] A method for teaching any point of a motor as the zero point records the current position Pb as the zero point position and locks this value into the EEPROM of the driver; the motor is moved to any other position, and the single-turn position value Ps of the encoder is read at this time, and the theoretically required moving distance of the motor is calculated as P = Ps - Pb.

[0007] In the above method for teaching any point of a motor as the zero point, it is necessary to judge the position relationship between the current position of the motor and the taught point, and recalculate the target position according to the position relationship and the shortest path.

[0008] Condition A: When the theoretically required moving distance of the motor P <= 0, further judge the magnitude relationship between 2*P and the number of pulses -Enc for one revolution of the motor to see whether the current motor position is on the left or right side of the limit post, and Pos is the current position of the motor.

[0009] When condition A is satisfied and 2*P < -Enc, recalculate the target position that the motor needs to travel from the current position to the zero position: Po = Pos - Enc - P;

[0010] When condition A is satisfied and 2*P > -Enc, recalculate the target position that the motor needs to travel from the current position to the zero position: Po = Pos - P.

[0011] Condition B: When the theoretically required moving distance of the motor P > 0, further judge the magnitude relationship between 2*P and the number of pulses Enc for one revolution of the motor to see whether the current motor position is on the left or right side of the limit post, and Pos is the current position of the motor;

[0012] When condition B is satisfied and 2*P < Enc, recalculate the target position that the motor needs to travel from the current position to the zero position: Po = Pos - P;

[0013] When condition B is satisfied and 2*P > Enc, recalculate the target position that the motor needs to travel from the current position to the zero position: Po = Pos + Enc - P.

[0014] In the above-mentioned method of teaching a motor to use any point as the zero point, after obtaining the new zero point position, the zero point position is assigned to the target position to achieve zero return.

[0015] In the above-mentioned method of teaching a motor to use any point as the zero point, the motor can return to the zero point by the shortest path when moving to any position or restarting after power failure.

[0016] Compared with the prior art, the advantages of the present invention are:

[0017] The present invention latches the zero point through the IO signal and realizes different point control requirements based on the zero point position. After the control is completed, the motor needs to be able to return to the zero point based on the current position in the shortest path. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the overall process provided by an embodiment of the present invention;

[0019] Figure 2 is a motor operation diagram of an embodiment when the single-turn position is read as 0;

[0020] Figure 3 This is the motor operation diagram of the embodiment when the single-turn position read is non-zero and is 0.25*Enc. DETAILED DESCRIPTION

[0021] The technical scheme of the present invention will be described clearly and completely below in conjunction with the accompanying drawings and embodiments. It should be understood that the embodiments described herein are only part of the embodiments disclosed but not all of them. They are only used to explain the present invention and are not used to limit the present invention.

[0022] The specific implementation of the present disclosure is described in detail below with reference to the accompanying drawings. A method for teaching a motor to use any point as a zero point, combined with Figure 1 This is a schematic diagram of the overall process of this application.

[0023] This embodiment is applied to the servo system of the DDR turntable. The system includes a DDR motor, an absolute encoder for position feedback on the motor, and a servo driver. The DDR turntable is equipped with limit posts due to special structural and process requirements; the encoder is an absolute encoder and has no special requirements for the motor power-on position, that is, the power-on position is random. This embodiment mainly uses the IO signal of the driver to trigger the rising edge, latch the taught zero position value into the EPROM of the servo driver, and further plan the shortest path. When the return to zero action is triggered, the motor returns from the current position to the latched position. Specifically, the following steps are included:

[0024] Latch the zero position and obtain the theoretical distance the motor needs to move.

[0025] In this embodiment, first, rotate the motor to the position that needs to be taught as the zero point. When the IO signal is triggered to be valid and lasts for a certain period of time, through the servo driver, record the current position Pb as the zero point position and latch this value into the EEPROM of the driver; move the motor to any other position, read the single-turn position value Ps of the encoder at this time, and calculate the theoretically required moving distance P of the motor as P = Ps - Pb.

[0026] Considering the limit posts, to achieve homing with the shortest path, before calculating the actual position that the motor really needs to move, the resolution of the motor encoder is known, that is, the number of pulses corresponding to one revolution of the motor is Enc.

[0027] Recalculate the true target position Po that the motor needs to move from the current position back to the zero point position.

[0028] Condition A: When the theoretically required moving distance P of the motor <= 0, further judge the magnitude relationship between 2*P and the number of pulses Enc for one revolution of the motor to see whether the current motor position is on the left or right side of the limit post. Pos is the current position of the motor.

[0029] When condition A is met and 2*P < -Enc, recalculate the target position that the motor needs to move from the current position to the zero point position: Po = Pos - Enc - P.

[0030] When condition A is met and 2*P > -Enc, recalculate the target position that the motor needs to move from the current position to the zero point position: Po = Pos - P.

[0031] Condition B: When the theoretically required moving distance P of the motor > 0, further judge the magnitude relationship between 2*P and the number of pulses Enc for one revolution of the motor to see whether the current motor position is on the left or right side of the limit post. Pos is the current position of the motor.

[0032] When condition B is met and 2*P < Enc, recalculate the target position that the motor needs to move from the current position to the zero point position: Po = Pos - P.

[0033] When condition B is met and 2*P > Enc, recalculate the target position that the motor needs to move from the current position to the zero point position: Po = Pos + Enc - P.

[0034] After obtaining the new target position, whether the motor moves to any position or powers off and restarts, it can achieve homing with the shortest path.

[0035] Please refer to Figure 2 and Figure 3 for the dynamic diagram of the motor operation.

[0036] The DDR turntable is equipped with a limit post. At the limit post position, the single-turn position read is 0. When the motor runs to P1 and triggers zero return, the motor needs to move counterclockwise from P1 to Pb to complete zero return; when the motor runs to P2, it triggers zero return, and the motor runs clockwise from P2 to Pb to complete zero return.

[0037] At the limit column, the single-turn position read is not 0. When the motor runs to P1, it triggers zero return, and the motor moves counterclockwise from P1 to Pb to complete zero return. When the motor runs at P2 (0-0.25*Enc interval), it triggers zero return. Since the P2 position is smaller than Pb, the motor still returns to zero counterclockwise. Due to the existence of the limit column, P2 cannot return to the Pb position after running to the limit column. At this time, the motor needs to be controlled to run clockwise from P2 to Pb to complete zero return.

[0038] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A device for teaching a motor to use any point as a zero point, comprising a DDR motor, a DDR turntable, an encoder and a servo driver, wherein the resolution of the encoder is Enc, and wherein: The single-turn position of the encoder is randomly placed. The DDR turntable is provided with limit posts for single-turn position feedback. The DDR turntable is provided with a taught zero position Pb, and the taught zero position Pb is latched through IO signals.

2. A method for teaching a motor to use any point as a zero point using the device of claim 1, characterized in that: Record the current position Pb as the zero position, and latch this value into the EEPROM of the driver; move the motor to any other position, read the single-turn position value Ps of the encoder at this time, and calculate the theoretically required moving distance of the motor P = Ps - Pb.

3. A method for teaching any point of a motor as the zero point according to claim 2, characterized in that Condition A: When the required moving distance P of the motor <= 0, further judge the magnitude relationship between 2*P and the number of pulses for one revolution of the motor - Enc to see whether the current motor position is on the left or right side of the limit post, and Pos is the current position of the motor.

4. A method for teaching a motor to use any point as a zero point according to claim 3, characterized in that: When condition A is satisfied and 2*P < -Enc, recalculate the target position that the motor needs to travel from the current position to the zero position: Po = Pos - Enc - P.

5. A method for teaching a motor to use any point as a zero point according to claim 3, characterized in that: When condition A is satisfied and 2*P > -Enc, recalculate the target position that the motor needs to travel from the current position to the zero position: Po = Pos - P.

6. A method for teaching a motor to use any point as a zero point according to claim 2, characterized in that: Condition B: When the required moving distance P of the motor > 0, further judge the magnitude relationship between 2*P and the number of pulses Enc for one revolution of the motor to see whether the current motor position is on the left or right side of the limit post, and Pos is the current position of the motor; 7. A method for teaching a motor to use any point as a zero point according to claim 6, characterized in that: When condition B is satisfied and 2*P < Enc, recalculate the target position that the motor needs to travel from the current position to the zero position: Po = Pos - P; 8. A method for teaching a motor to use any point as a zero point according to claim 6, characterized in that: When condition B is satisfied and 2*P > Enc, recalculate the target position that the motor needs to travel from the current position to the zero position: Po = Pos + Enc - P.

9. A method for teaching a motor to use any point as a zero point according to any one of claims 2 to 8, characterized in that: After obtaining the new zero position, assign the zero position to the target position to achieve homing.

10. A method for teaching a motor to use any point as a zero point according to any one of claims 2 to 8, characterized in that: Moving to any position or powering off and restarting can achieve homing with the shortest path.

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