An absolute positioning method for electric actuators

Abstract

The application relates to the technical field of electric actuators, in particular to an absolute positioning method for an electric actuator, which solves the problems that the photoelectric encoder with zero point in the prior art needs to be powered to find zero, the absolute photoelectric encoder is constrained by the size of the electric actuator, the positioning resolution is not high, and the cost is relatively high; and the magnetic encoder is similar to the photoelectric encoder and belongs to a non-contact position sensor, and does not have the problem of abrasion. The absolute positioning method for the electric actuator comprises the cooperation of a relative photoelectric encoder and a high-line digital code disc, two relative encoder reading heads, and encoding relative code tracks, and the relative encoder reading heads and the encoding relative code tracks are used to acquire position increment information; two absolute zero point reading heads are used in cooperation, and the absolute position information is acquired through the characteristic code of the absolute zero point code track. The application realizes the above-mentioned high-precision absolute positioning by manufacturing a specific code disc and adding a power-off saving related circuit, and has the advantages of long service life, high precision, low temperature drift, compact structure and low cost.

Description

Technical Field

[0001] This invention relates to the field of electric actuator technology, and more particularly to an absolute positioning method for electric actuators. Background Technology

[0002] Electric actuators come in two types: partial-turn electric actuators and multi-turn electric actuators. The former mainly controls valves requiring partial rotation. Electric multi-turn actuators are one of the most commonly used and reliable types. They use a single-phase or three-phase motor to drive a gear or worm gear, which in turn drives the valve stem nut. The valve stem nut causes the valve stem to move, opening or closing the valve. Multi-turn electric actuators can quickly drive large-size valves. To protect the valve from damage, a limit switch installed at the end of the valve stroke cuts off the motor power. Simultaneously, a torque sensor cuts off the motor power when the safety torque is exceeded. A position switch indicates the valve's open / closed state. A handwheel mechanism with a clutch allows manual valve operation in case of power failure. An electric actuator is an electric device that can be executed to a specific position according to instructions. They often employ a rotary mechanism. With the development of industrial automation, manual operation is being replaced by mechanical or automated equipment. Electric actuators act as the interface between the control system and the mechanical movement of the valve, and are increasingly used. Electric actuators require long-term stable operation in some applications, have high positioning accuracy requirements, and a wide temperature variation range. To meet these requirements, the absolute positioning method of electric actuators needs to have a long life, high precision, low temperature drift, and be as compact and simple as possible with low cost.

[0003] Common absolute positioning methods for electric actuators include resistive position sensors, photoelectric encoders with zero points or absolute positioning, and magnetic encoders. Resistive position sensors are low-cost and simple in structure, but they are prone to wear, resulting in a short lifespan for the actuator. After wear, the position will also become inaccurate, and they are greatly affected by temperature drift. Photoelectric encoders overcome the wear problem of resistive position sensors and are less affected by temperature drift. Photoelectric encoders with zero points require power-on zeroing, while absolute photoelectric encoders are constrained by the size of the electric actuator, resulting in low positioning resolution and high cost. Magnetic encoders are similar to photoelectric encoders, belonging to non-contact position sensors, and do not suffer from wear problems. However, their positioning accuracy is relatively poor, and they are easily affected by temperature drift, which is extremely inconvenient. Therefore, there is an urgent need for an absolute positioning method for electric actuators to solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide an absolute positioning method for electric actuators, which solves the problems of existing photoelectric encoders with zero points requiring power-on zeroing, and absolute photoelectric encoders being constrained by the size of electric actuators, resulting in low positioning resolution and high cost; while magnetic encoders, similar to photoelectric encoders, are non-contact position sensors and do not suffer from wear problems.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] An absolute positioning method for an electric actuator includes a relative photoelectric encoder and a high-line digital disk, two relative encoder read heads that encode relative code tracks to obtain position increment information, and two absolute zero-point read heads that work together to obtain absolute position information through the feature codes of the absolute zero-point code tracks. The two complement each other and work together to save the position when the power is off, achieving high-precision absolute positioning. The power-off saving method records the real-time position and restores the power-off value when the power is on. It adopts distinguishable multi-zero-point absolute positioning. The actuator can achieve real-time calibration of the absolute position saved when the power is off under small-range movement. The above-mentioned high-precision absolute positioning is achieved by manufacturing a specific code disk and adding relevant circuitry for power-off saving.

[0007] Preferably, during the normal power outage process, two signals are triggered: a low power voltage signal and a low control voltage signal. The two signals are sequential, and sufficient time is allowed for effective signal detection and corresponding action execution. After the low power voltage signal is triggered and lasts for a predetermined time, it is considered to be valid. At this time, it is necessary to determine whether the motor is running. If it is running, the electric actuator is stopped; otherwise, it will wait for the low control voltage signal to be triggered. If the low power voltage signal does not last for the predetermined time, it is considered not to be a true power outage, and the normal operation of the electric actuator will be restored.

[0008] Preferably, after the low control voltage signal is triggered and lasts for a predetermined time, the low control voltage signal is considered valid. At this time, real-time position-related information will be saved. If the signal does not last for the predetermined time, it is considered that the electric actuator power may have been restored or the signal was falsely triggered. At this time, the low power voltage signal is judged. If the low power voltage signal is invalid, it is considered that the electric actuator power has been restored or that it is not a true power failure. At this time, the normal operation of the electric actuator will be restored.

[0009] Preferably, the real-time location at the time of power failure has a check bit when it is saved to ensure that the saved real-time location is valid.

[0010] Preferably, when the power is turned on, the electric actuator reads the real-time position saved during the last power failure. If the verification fails, it will move within a small range until it finds the zero point mark and recalibrates the real-time position. If the verification passes, the saved value is used as the current position. During subsequent operation, when the electric actuator reaches the zero point mark, it will be recalibrated to prevent the electric actuator from rotating after a power failure and causing a deviation in the real-time position.

[0011] Preferably, the zero-point markers are evenly distributed around the encoder disk. Different lengths and combinations are used to distinguish the absolute position of the current zero-point marker. When the electric actuator leaves the factory, it rotates forward and backward once to calibrate and record the position of each zero-point marker. In subsequent actual operation, the encoder position of the zero-point marker is compared with the factory-calibrated position. If there is a deviation, the calibrated position is assigned to the current position to achieve position calibration.

[0012] This invention has at least the following beneficial effects:

[0013] This invention employs a relative photoelectric encoder in conjunction with a high-resolution digital disk, achieving high resolution through a four-way frequency division, significantly improving relative positioning accuracy. It also addresses the lifespan and temperature drift issues associated with other sensors. Recognizing the inconvenience of traditional methods requiring zero-point matching and power-on zeroing, which are incompatible with absolute positioning by relative encoders, this invention utilizes a power-off preservation method to record the real-time position, restoring the power-off value upon power-on. Furthermore, it employs identifiable multi-zero-point absolute positioning, allowing the actuator to perform real-time calibration of the power-off-preserved absolute position within a small range of motion, thus achieving high-precision absolute positioning. Based on traditional photoelectric encoders with zero-point capabilities, this invention utilizes a specially designed code disk and incorporates power-off preservation circuitry to achieve the aforementioned high-precision absolute positioning, while also offering long lifespan, high accuracy, low temperature drift, a compact structure, and low cost. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a diagram showing the encoder and code disk arrangement of the present invention;

[0016] Figure 2 This is a flowchart illustrating the operation of the electric actuator of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Example 1

[0018] Reference Figure 1-2 This system includes a relative photoelectric encoder working in conjunction with a high-line digital disk. Two relative encoder read heads encode relative code tracks to obtain position increment information; two absolute zero-point read heads work together to obtain absolute position information through the feature codes of the absolute zero-point code tracks. The two complement each other and work together to save the position even when the power is off, achieving high-precision absolute positioning. The power-off saving method records the real-time position and restores the power-off value when the power is on. It also uses distinguishable multi-zero-point absolute positioning. The actuator can perform real-time calibration of the absolute position saved when the power is off under small-range movement. The high-precision absolute positioning mentioned above is achieved by manufacturing a specific code disk and adding relevant circuitry for power-off saving. Example 2

[0019] Reference Figure 1-2 During the normal power outage process, two signals will be triggered: a low power voltage signal and a low control voltage signal. The two signals are sequential and allow sufficient time for effective signal detection and corresponding action execution. If the low power voltage signal is triggered and lasts for a predetermined time, it is considered valid. At this time, it is necessary to determine whether the motor is running. If it is running, the electric actuator will be stopped; otherwise, it will wait for the low control voltage signal to be triggered. If the low power voltage signal does not last for the predetermined time, it is considered not a true power outage, and the electric actuator will resume normal operation. Example 3

[0020] Reference Figure 1-2 If the low control voltage signal is triggered and lasts for a predetermined time, the low control voltage signal is considered valid. At this time, real-time position-related information will be saved. If the signal does not last for the predetermined time, it is considered that the electric actuator power may have been restored or the signal was falsely triggered. At this time, the low power voltage signal is judged. If the low power voltage signal is invalid, it is considered that the electric actuator power has been restored or that it is not a true power failure. At this time, the normal operation of the electric actuator will be restored. Example 4

[0021] Reference Figure 1-2 The real-time location at the time of power failure has a check bit when it is saved to ensure that the saved real-time location is valid. Example 5

[0022] Reference Figure 1-2When powered on, the electric actuator reads the real-time position saved during the last power outage. If the verification fails, it will move within a small range until it finds the zero point mark and recalibrates the real-time position. If the verification passes, the saved value is used as the current position. During subsequent operation, when the electric actuator reaches the zero point mark, it will be recalibrated to prevent the electric actuator from rotating after a power outage and causing a deviation in the real-time position. Example 6

[0023] Reference Figure 1-2 The zero-point markers are evenly distributed around the encoder disk. Different lengths and combinations are used to distinguish the absolute position of the current zero-point marker. When the electric actuator leaves the factory, it rotates forward and backward once to calibrate and record the position of each zero-point marker. In subsequent actual operation, the encoder position of the zero-point marker will be compared with the factory-calibrated position. If there is a deviation, the calibrated position will be assigned to the current position to achieve position calibration.

[0024] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention. The scope of protection claimed by the appended claims and their equivalents is defined.

Claims

1. An absolute positioning method for an electric actuator, comprising a relative photoelectric encoder in conjunction with a high-resolution digital disk, two relative encoder read heads encoding relative code tracks to obtain position increment information; two absolute zero-point read heads used in conjunction to obtain absolute position information through the feature codes of the absolute zero-point code tracks. The two complement each other and work together to achieve high-precision absolute positioning by power-off saving. The power-off saving method records the real-time position and restores the power-off value upon power-on. It employs distinguishable multi-zero-point absolute positioning, allowing real-time calibration of the power-off saved absolute position even during small-range actuator movements. The high precision is achieved by fabricating a specific code disk and incorporating power-off saving circuitry. Absolute positioning involves two signals triggered during a normal power outage: a low power voltage signal and a low control voltage signal. These signals are sequential, with sufficient time allowed for effective signal detection and corresponding action execution. If the low power voltage signal is triggered and lasts for a predetermined time, it is considered valid. At this point, it's necessary to determine if the motor is running. If it is, the electric actuator stops; otherwise, it waits for the low control voltage signal to be triggered. If the low power voltage signal does not last for the predetermined time, it is considered not a true power outage, and the electric actuator resumes normal operation. Similarly, if the low control voltage signal is triggered and lasts for the predetermined time, it is considered a valid low power voltage signal. If the low voltage signal is valid, real-time position information will be saved. If the signal does not last for the agreed time, it is assumed that the electric actuator power may have been restored or the signal was falsely triggered. In this case, the low power voltage signal is checked. If the low power voltage signal is invalid, it is assumed that the electric actuator power has been restored or that the power failure was not real. In this case, normal operation of the electric actuator will resume. The real-time position at the time of power failure has a check bit when it is saved to ensure that the saved real-time position is valid. When power is restored, the electric actuator will read the real-time position saved during the last power failure. If the check fails, it will move within a small range until it finds the zero point marker and recalibrates the real-time position. If the verification passes, the saved value is used as the current position. During subsequent operation, when the electric actuator reaches the zero point mark, it will be recalibrated to prevent the electric actuator from rotating and causing deviation in real-time position after power failure. The zero point marks are evenly distributed around the encoder disk. Different lengths and combinations are used to distinguish the absolute position of the current zero point mark. When the electric actuator leaves the factory, it rotates one full cycle in both directions to calibrate and record the position of each zero point mark. During actual operation, the encoder position of the zero point mark will be compared with the factory-calibrated position. If there is a deviation, the calibrated position will be assigned to the current position to achieve position calibration.

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