A displacement control method of a DC motor electric cylinder with open-closed loop compound control

Abstract

The application discloses a displacement control method for a DC motor electric cylinder with open-loop and closed-loop compound control, and comprises the following steps: obtaining the actual position of the piston rod of the DC motor electric cylinder; calculating the displacement deviation according to the target position and the actual position; selectively adopting an open-loop control mode or a closed-loop PID control mode to generate a duty cycle control signal according to the size relationship between the absolute value of the displacement deviation and a preset threshold value, so as to drive the piston rod of the DC motor electric cylinder to move; wherein, when the absolute value of the displacement deviation is greater than the preset threshold value, the open-loop control mode is adopted to output a fixed duty cycle signal; and when the absolute value of the displacement deviation is less than or equal to the preset threshold value, the closed-loop PID control mode is adopted to adjust the duty cycle signal in real time. By introducing the open-loop and closed-loop compound control strategy, the application effectively solves the contradiction that the traditional single PID control is difficult to balance the response speed and the positioning accuracy under the gain limited condition. The application can improve the motion performance and the control quality of the DC motor electric cylinder.

Description

Technical Field

[0001] This invention relates to the field of electric cylinder motion control technology, and in particular to a DC motor electric cylinder displacement control method with open-loop and closed-loop composite control. Background Technology

[0002] An electric cylinder is an actuator that converts rotary motion into linear motion. Due to its environmental friendliness, superior controllability, and fast response speed, it is widely used in engineering equipment, medical devices, and other fields. Currently, DC brushed motors are one of the commonly used drive components for electric cylinders. In existing motion controllers, PID control has become a standard feature. PID control generates a control signal by calculating proportional, integral, and derivative gains, aiming to reduce the error between the target displacement and the actual displacement of the electric cylinder piston rod.

[0003] However, to ensure system stability, the value of the PID feedback gain is strictly limited and cannot be set too high. Therefore, without causing system oscillations and instability, relying solely on the PID gain is often insufficient to reduce displacement errors to an acceptable level, resulting in insufficient positioning accuracy or slow response speed. Current technology lacks a solution that can effectively balance fast response and accurate positioning. Summary of the Invention

[0004] In view of this, the present invention provides a displacement control method for a DC motor electric cylinder with open-loop and closed-loop composite control. The open-loop control generates as much displacement control quantity as possible to ensure response speed while avoiding oscillation and instability; and the closed-loop PID control plays a precise adjustment role to reduce displacement error in steady state, ultimately achieving fast and accurate positioning.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A displacement control method for a DC motor electric cylinder using open-loop and closed-loop composite control includes the following steps: obtaining the actual position of the piston rod of the DC motor electric cylinder; calculating the displacement deviation based on the target position and the actual position; and selectively generating a duty cycle control signal using either an open-loop control mode or a closed-loop PID control mode based on the relationship between the absolute value of the displacement deviation and a preset threshold, to drive the piston rod of the DC motor electric cylinder to move; wherein, when the absolute value of the displacement deviation is greater than the preset threshold, an open-loop control mode is used to output a fixed duty cycle signal; and when the absolute value of the displacement deviation is less than or equal to the preset threshold, a closed-loop PID control mode is used to adjust the duty cycle signal in real time.

[0006] Preferably, the preset threshold is a proportional threshold, which is obtained by multiplying a set proportional coefficient by a reference benchmark value.

[0007] Preferably, when the piston rod performs the extension positioning action, the reference reference value is the target position, the proportional coefficient is a first proportional coefficient, and the preset threshold is the product of the first proportional coefficient and the target position.

[0008] Preferably, the first proportionality coefficient is a real number greater than 0 and less than 1.

[0009] Preferably, when the piston rod performs a retraction positioning action, the reference reference value is the original actual positioning position, the proportional coefficient is a second proportional coefficient, and the preset threshold is the product of the second proportional coefficient and the original actual positioning position.

[0010] Preferably, the second proportionality coefficient is a real number greater than 0 and less than 1.

[0011] Preferably, in the open-loop control mode, the duty cycle of the fixed duty cycle signal is a pre-calibrated constant value.

[0012] Preferably, in the closed-loop PID control mode, the duty cycle signal is adjusted in real time based on the calculation results of the proportional gain, integral gain and derivative gain to eliminate steady-state error.

[0013] Preferably, the DC motor electric cylinder displacement control method with open-loop and closed-loop composite control further includes acquiring the actual position information of the piston rod through a position sensor, wherein the position sensor includes a potentiometer or a wire displacement sensor.

[0014] Preferably, the duty cycle control signal is used to adjust the duty cycle of the PWM waveform driving the DC motor.

[0015] The present invention also proposes a computer device, including 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, it implements the steps of the DC motor electric cylinder displacement control method of open-loop and closed-loop composite control as described in any of the above embodiments.

[0016] The present invention also proposes a computer-readable storage medium storing a computer program thereon, wherein the computer program, when executed by a processor, implements the steps of the DC motor electric cylinder displacement control method of open-loop and closed-loop composite control as described in any of the above embodiments.

[0017] The beneficial effects of this invention are as follows: This invention effectively solves the contradiction between response speed and positioning accuracy in traditional single PID control under gain-limited conditions by introducing a combined open-loop and closed-loop control strategy. Specifically, when the displacement deviation is large, open-loop fixed duty cycle control is used, which can quickly generate a large displacement control quantity, accelerate the response process, and avoid the risk of system oscillation and instability caused by excessive PID gain. When the displacement deviation decreases to within the threshold range, closed-loop PID control is switched on, and the precise adjustment capability of the PID algorithm is used to gradually eliminate residual errors, ensuring the accuracy of the final positioning. In addition, dynamic thresholds based on the target position and the original actual position are set for the extension and retraction actions, respectively, making the control strategy more consistent with the actual motion conditions and further improving the system's adaptability and control efficiency. The overall solution of this invention has a simple structure and clear logic, and can significantly improve the motion performance and control quality of DC motor electric cylinders. Detailed Implementation

[0018] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0019] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0020] The following describes a DC motor electric cylinder displacement control method with open-loop and closed-loop composite control in an embodiment of the present invention.

[0021] This application discloses a displacement control method for a DC motor electric cylinder using a combined open-loop and closed-loop control, comprising the following steps: obtaining the actual position of the piston rod of the DC motor electric cylinder; calculating the displacement deviation based on the target position and the actual position; and selectively generating a duty cycle control signal using either an open-loop control mode or a closed-loop PID control mode based on the relationship between the absolute value of the displacement deviation and a preset threshold, to drive the piston rod of the DC motor electric cylinder to move; wherein, when the absolute value of the displacement deviation is greater than the preset threshold, an open-loop control mode is used to output a fixed duty cycle signal; and when the absolute value of the displacement deviation is less than or equal to the preset threshold, a closed-loop PID control mode is used to adjust the duty cycle signal in real time.

[0022] Specifically, if the absolute value of the deviation is greater than a preset threshold, the system is determined to be in the coarse adjustment stage. The system switches to open-loop control mode and directly outputs a fixed duty cycle signal to drive the motor, thereby quickly closing the distance between the piston rod and the target position. If the absolute value of the deviation is less than or equal to the preset threshold, the system is determined to be in the fine adjustment stage. The system switches to closed-loop PID control mode and dynamically adjusts the duty cycle according to the real-time error to finely correct the position.

[0023] This embodiment provides a dynamic control mode switching mechanism based on the magnitude of the deviation. Its technical advantage lies in breaking through the limitations of traditional single PID control. Open-loop coarse adjustment ensures the system's rapid response capability, avoiding the lag in the initial stage of PID control, while closed-loop fine adjustment ensures the final positioning accuracy, achieving a balance between speed and accuracy. Compared to existing technologies that rely entirely on PID control, which can easily lead to slow response or overshoot oscillations, this embodiment provides a more efficient and stable control path.

[0024] In some embodiments, the preset threshold is a proportional threshold, which is obtained by multiplying a set proportional coefficient by a reference value. Specifically, this proportional threshold method allows the switching point to be dynamically adjusted according to actual operating conditions, rather than being a fixed absolute value. Its technical advantage lies in enhancing the flexibility and adaptability of the control method, making it applicable to electric cylinder applications with different strokes and loads. Compared to fixed thresholds, which may switch control modes too early or too late under certain operating conditions, proportional thresholds can better match system characteristics and optimize overall control performance.

[0025] In some embodiments, when the piston rod performs the extension and positioning action, the reference value is the target position, the proportional coefficient is the first proportional coefficient, and the preset threshold is the product of the first proportional coefficient and the target position. For example, when the target position is 100 mm, and the first proportional coefficient is set to 0.2, the threshold is 20 mm. When the difference between the actual position and the target position is greater than 20 mm, open-loop control is used; otherwise, PID control is used. The advantage of this technology is that, for the extension action, setting the threshold based on the target position can reasonably reflect the relative distance to the target position, ensuring full acceleration when moving away from the target and a smooth transition when approaching the target, effectively preventing impact and overshoot during the extension process.

[0026] In some embodiments, the first proportional coefficient is a real number greater than 0 and less than 1. This limitation ensures that the preset threshold is always less than the target position, thus ensuring that the control mode switch will occur before the piston rod reaches the target position. The technical effect is to guarantee the rigor and feasibility of the control logic, avoiding situations where the threshold is greater than or equal to the target position due to improper coefficient values, preventing the entry into the fine-tuning mode. This ensures that the entire positioning process can be completed smoothly and ultimately achieves high-precision stopping.

[0027] In some embodiments, when the piston rod performs a retraction positioning action, the reference value is the original actual position, the proportional coefficient is a second proportional coefficient, and the preset threshold is the product of the second proportional coefficient and the original actual position. For example, if the starting position is 80 mm and the second proportional coefficient is 0.2, the threshold is 16 mm. When the difference between the target position and the original actual position is greater than 16 mm, open-loop control is used; otherwise, PID control is used.

[0028] In this embodiment, for the retraction action, since the target position is usually zero or a small value, if the target position is still used as the reference, the threshold may be too small, causing premature PID control and losing the meaning of coarse adjustment. Therefore, using the starting position as the reference is more reasonable. This embodiment specifically optimizes the logic of the retraction control to ensure that the retraction process also has good speed and smoothness.

[0029] In some embodiments, the second proportional coefficient is a real number greater than 0 and less than 1. This limitation ensures that the preset threshold is always less than the target position, thus ensuring that the control mode switch will occur before the piston rod reaches the target position. The technical effect is to guarantee the rigor and feasibility of the control logic, avoiding situations where the threshold is greater than or equal to the target position due to improper coefficient values, preventing the entry into the fine-tuning mode. This ensures that the entire positioning process can be completed smoothly and ultimately achieves high-precision stopping.

[0030] In some embodiments, in the open-loop control mode, the duty cycle of the fixed duty cycle signal is a pre-calibrated constant value. This fixed duty cycle is a constant value determined beforehand through experimentation or calibration, and remains unchanged during open-loop control once selected.

[0031] In this embodiment, a constant duty cycle provides stable and robust power output, ensuring the piston rod moves at a fast and uniform speed, avoiding jitter or inconsistent response caused by duty cycle fluctuations. Simultaneously, pre-calibration allows this value to be optimized based on specific motor and load characteristics, minimizing initial errors when entering the fine-tuning stage while maintaining response speed, thus creating favorable conditions for subsequent PID control.

[0032] In some embodiments, in the closed-loop PID control mode, the duty cycle signal is adjusted in real time based on the calculated results of the proportional gain, integral gain, and derivative gain to eliminate steady-state error. Specifically, the integral action is mainly used to eliminate steady-state error, while the proportional and derivative actions affect the system's response speed and damping characteristics, respectively. Its technical advantage lies in fully utilizing the precision of PID control in error elimination, enabling the piston rod to be ultimately stabilized within a very small error range near the target position, meeting the requirements of high-precision positioning. Compared to open-loop control, which can only approximate the target position, this embodiment ensures the accuracy of the final positioning result.

[0033] In some embodiments, the DC motor electric cylinder displacement control method with open-loop and closed-loop composite control further includes acquiring the actual position information of the piston rod through a position sensor, including a potentiometer or a wire displacement sensor. By configuring position detection elements such as potentiometers or wire displacement sensors, the actual position information of the piston rod is acquired in real time and fed back to the host computer or controller. Its technical advantage lies in providing an accurate position feedback basis for the entire control method, which is a prerequisite for realizing closed-loop PID control, and also provides a reliable basis for judging the transition from open-loop to closed-loop control. Using standardized sensor names rather than specific model numbers ensures the universality and feasibility of the solution.

[0034] In some embodiments, the duty cycle control signal is used to adjust the duty cycle of the PWM waveform driving the DC motor, thereby controlling the average voltage and speed of the motor. Its technical advantage lies in implementing an abstract control method at a concrete hardware execution level, clarifying the signal chain, and making the solution more operable and industrially applicable.

[0035] The present invention also proposes a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the processor executes the computer program to implement the steps of the DC motor electric cylinder displacement control method of open-loop and closed-loop composite control as described in any of the above embodiments.

[0036] The present invention also proposes a computer-readable storage medium storing a computer program thereon, wherein when the computer program is executed by a processor, it implements the steps of the DC motor electric cylinder displacement control method of open-loop and closed-loop composite control as described in any of the above embodiments.

[0037] Other configurations and operations of the DC motor electric cylinder displacement control method with open-loop and closed-loop composite control according to embodiments of the present invention are known to those skilled in the art and will not be described in detail here.

[0038] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0039] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for displacement control of a DC motor electric cylinder using open-loop and closed-loop composite control, characterized in that, Includes the following steps: Obtain the actual position of the piston rod of the DC motor electric cylinder; Calculate the displacement deviation based on the target position and the actual position; Based on the relationship between the absolute value of the displacement deviation and the preset threshold, an open-loop control mode or a closed-loop PID control mode is selectively used to generate a duty cycle control signal to drive the piston rod of the DC motor electric cylinder. Specifically, when the absolute value of the displacement deviation is greater than the preset threshold, an open-loop control mode is adopted, and a fixed duty cycle signal is output; when the absolute value of the displacement deviation is less than or equal to the preset threshold, a closed-loop PID control mode is adopted, and the duty cycle signal is adjusted in real time.

2. The DC motor electric cylinder displacement control method with open-loop and closed-loop composite control according to claim 1, characterized in that, The preset threshold is a proportional threshold, which is obtained by multiplying a set proportional coefficient by a reference base value.

3. The DC motor electric cylinder displacement control method with open-loop and closed-loop composite control according to claim 2, characterized in that, When the piston rod performs the extension positioning action, the reference reference value is the target position, the proportional coefficient is the first proportional coefficient, and the preset threshold is the product of the first proportional coefficient and the target position.

4. The DC motor electric cylinder displacement control method with open-loop and closed-loop composite control according to claim 3, characterized in that, The first proportionality coefficient is a real number greater than 0 and less than 1.

5. The DC motor electric cylinder displacement control method with open-loop and closed-loop composite control according to claim 2, characterized in that, When the piston rod performs a retraction positioning action, the reference reference value is the original actual positioning position, the proportional coefficient is a second proportional coefficient, and the preset threshold is the product of the second proportional coefficient and the original actual positioning position.

6. The DC motor electric cylinder displacement control method with open-loop and closed-loop composite control according to claim 5, characterized in that, The second proportionality coefficient is a real number greater than 0 and less than 1.

7. The DC motor electric cylinder displacement control method with open-loop and closed-loop composite control according to claim 1, characterized in that, In the open-loop control mode, the duty cycle of the fixed duty cycle signal is a pre-calibrated constant value.

8. The DC motor electric cylinder displacement control method with open-loop and closed-loop composite control according to claim 1, characterized in that, In the closed-loop PID control mode, the duty cycle signal is adjusted in real time based on the calculation results of proportional gain, integral gain and derivative gain to eliminate steady-state error.

9. The DC motor electric cylinder displacement control method with open-loop and closed-loop composite control according to claim 1, characterized in that, It also includes acquiring the actual position information of the piston rod through a position sensor, which includes a potentiometer or a wire displacement sensor.

10. The DC motor electric cylinder displacement control method with open-loop and closed-loop composite control according to claim 1, characterized in that, The duty cycle control signal is used to adjust the duty cycle of the PWM waveform that drives the DC motor.

11. A computer 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, it implements the steps of the DC motor electric cylinder displacement control method with open-loop and closed-loop composite control as described in any one of claims 1-10.

12. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the DC motor electric cylinder displacement control method with open-loop and closed-loop composite control as described in any one of claims 1-10.