CN112324749B - Method for determining and compensating null shift of servo valve - Google Patents
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
- F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
- F15B13/00—Details of servomotor systems ; Valves for servomotor systems
- F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
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Abstract
本发明属于液压伺服控制技术领域，具体涉及一种伺服阀零漂的确定及补偿方法，并对控制回路进行补偿。在油压正常情况下，若处于闭环控制中的液压伺服系统工作正常且处于空载状态，可利用过去一段时间的伺服阀控制电流值得出当前时刻的零漂值，并通过自学习对该零漂值不断进行修正，以跟随伺服阀零漂的缓慢变化；其他情况下零漂值保持不变。将获取的零漂值补偿到控制器输出上，可提高液压伺服系统中液压缸双向动作的一致性，防止一个方向调节范围过小，影响该方向的动作速度。本发明可有效提高液压伺服系统的闭环控制精度。
The invention belongs to the technical field of hydraulic servo control, in particular to a method for determining and compensating zero drift of a servo valve, and compensating a control loop. Under normal oil pressure, if the hydraulic servo system under closed-loop control works normally and is in a no-load state, the current value of the servo valve control current value in the past period can be used to obtain the zero drift value at the current moment, and the zero drift value at the current moment can be obtained through self-learning. The drift value is continuously corrected to follow the slow change of the servo valve zero drift; otherwise, the zero drift value remains unchanged. Compensating the acquired zero drift value to the output of the controller can improve the consistency of the two-way action of the hydraulic cylinder in the hydraulic servo system, and prevent the adjustment range of one direction from being too small and affecting the action speed in that direction. The invention can effectively improve the closed-loop control precision of the hydraulic servo system.
Description
Technical Field
The invention belongs to the field of hydraulic servo control, and particularly relates to a method for determining and compensating a servo valve null shift, which is a method for determining the servo valve null shift and compensating a control loop.
Background
Modern hydraulic servo systems usually consist of a controller, a servo valve, and a hydraulic cylinder. When the system works normally, the hydraulic servo valve inevitably has a null shift phenomenon, namely the actual zero point of the hydraulic servo valve in the zero position is different from the zero point of the control signal. The accumulation of the error between the two zero points over a plurality of control cycles can result in a large error, thereby affecting the control accuracy of the hydraulic servo system.
The reason for the zero drift may be that the servo valve used has zero drift itself; parameters may change due to long-term use of electronic components in each link; it may be that the supply voltage is not stable; the environment of the production field may be severe, and in the actual operation process of the system, the actual zero point of the servo valve may also change along with the change of external conditions such as the environmental temperature.
In the prior art, a solution for null shift of a hydraulic servo system comprises the following steps: the quality of the servo valve is improved, the zero offset and the zero drift of the servo valve are reduced, or the zero position of the regulating system is positioned at the zero point before the operation, but the two points have great limitations; when the null shift is generated, an opposite voltage signal is given to the servo valve, and the tiny voltage signal is restrained from being enlarged, so that the null shift is restrained; a displacement sensor, an oil pressure sensor and a servo valve are arranged on a hydraulic cylinder of the rolling mill, the displacement detection and the oil pressure signal of the hydraulic cylinder are read through a high-speed data acquisition module, the zero drift compensation quantity of the hydraulic servo valve is calculated, and the opening degree of the servo valve is controlled to carry out dynamic compensation of closed-loop adjustment of the position of the hydraulic cylinder; and when the integral reset signal is invalid and the integral enable signal is valid according to the hydraulic pressure pressing mode and whether the measuring equipment is in fault, integrating the servo valve control signal and outputting amplitude limitation to superimpose the integrated amplitude limitation output value on the servo valve control signal and output the servo valve control signal to a servo valve, and compensating the actual zero point of the servo valve and the servo valve control signal. However, the above methods are relatively complex, and it is difficult to ensure that the hydraulic servo system has a fast response speed and a high control accuracy.
Disclosure of Invention
Aiming at the technical problems, the invention provides a method for determining and compensating the null shift of a servo valve, which can solve the technical problem that the closed-loop control precision of a hydraulic servo system is influenced due to the null shift phenomenon in the conventional hydraulic control system.
The invention is realized by the following technical scheme:
a servo valve null shift determining and compensating method utilizes a servo valve null shift value at the previous moment and a current value output by a controller at the current moment to determine the servo valve null shift value at the current moment, and continuously corrects the servo valve null shift value at the current moment through self-learning; and compensating the acquired zero drift value of the servo valve at the current moment to the output of the controller so as to improve the consistency of the bidirectional actions of the hydraulic cylinder in the hydraulic servo system and improve the closed-loop control precision of the hydraulic servo control system.
Further, the method comprises the following steps:
the method comprises the following steps: acquiring a controller output current value when a hydraulic servo system in closed-loop control works normally under the condition that the oil pressure is normal;
step two: when the hydraulic servo system is in an idle state, determining the zero drift value of the servo valve at the current moment by utilizing the zero drift value of the servo valve at the previous moment and the output current value of the controller at the current moment, wherein the relation formula between the zero drift value of the servo valve and the output current value of the controller is as follows:
Z(n)＝(1-α)×Z(n-1)+α×I(n)
in the formula: i (n) and Z (n) respectively represent the output current value of the controller at the time n and the zero drift value of the servo valve at the time n, and the zero drift value is kept unchanged in a load state; z (n-1) represents a servo valve zero drift value at the time of n-1; alpha is an adjusting coefficient; the zero drift value can change slightly along with the change of time, and the size of the zero drift value at the current moment can be determined by adjusting the adjusting coefficient alpha.
Step three: determining an adjusting coefficient alpha, wherein the value of alpha is between 0 and 0.02;
step four: and compensating the acquired zero drift value of the servo valve at the current moment to the output of the controller, thereby realizing the improvement of the closed-loop control precision of the system.
Further, in the first step, when the hydraulic servo system works normally and is in an idle state, under the condition of no zero drift compensation device, the output current value of the controller is equal to the given current value of the servo valve.
Further, in the second step, when the hydraulic servo system is in an idle state, the zero drift value of the servo valve is continuously corrected through self-learning; when the hydraulic servo system is in a loaded state, the zero drift value of the servo valve is kept unchanged.
The invention has the beneficial technical effects that:
the method of the invention utilizes the servo valve zero drift value at the last moment and the current value output by the controller at the current moment to determine the servo valve zero drift value at the current moment; the zero drift value of the servo valve is continuously corrected through a self-learning method, the obtained zero drift value of the servo valve is compensated to the controller for output, the consistency of the bidirectional actions of the hydraulic cylinder in the hydraulic servo system can be improved, and the action speed of one direction is prevented from being influenced due to the fact that the adjustment range of the direction is too small. The method provided by the invention can improve the closed-loop control precision of the hydraulic servo control system without adding new equipment.
Drawings
FIG. 1 is a block diagram of a hydraulic system control according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a servo valve null shift value obtaining step according to an embodiment of the present invention;
FIG. 3 is a simulation diagram of a given current of a servo valve according to an embodiment of the present invention;
FIG. 4 is a diagram illustrating a null shift simulation of a servo valve according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to examples. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
On the contrary, the invention is intended to cover alternatives, modifications, equivalents and alternatives which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, certain specific details are set forth in order to provide a better understanding of the present invention. It will be apparent to one skilled in the art that the present invention may be practiced without these specific details.
The embodiment of the invention provides a method for determining and compensating the null shift of a servo valve, which is characterized in that the null shift value of the servo valve is obtained by utilizing the null shift value of the servo valve and the output current value of a controller through a self-learning method, the null shift value of the servo valve is compensated to the output of the controller, and the closed-loop control precision of a hydraulic servo system can be improved.
Specifically, the servo valve null shift value at the current moment is determined by utilizing the servo valve null shift value at the previous moment and the current value output by the controller at the current moment, and the servo valve null shift value at the current moment is continuously corrected through self-learning; and compensating the acquired zero drift value of the servo valve at the current moment to the output of the controller so as to improve the consistency of the bidirectional actions of the hydraulic cylinder in the hydraulic servo system and improve the closed-loop control precision of the hydraulic servo control system.
As shown in fig. 2, the method comprises the steps of:
the method comprises the following steps: acquiring a controller output current value when a hydraulic servo system in closed-loop control works normally under the condition that the oil pressure is normal; determining the output current value of the controller and the null shift value of the servo valve at the moment n, which are respectively represented by I (n) and Z (n);
step two: when the hydraulic servo system is in an idle state, a relation formula Z (n) between a servo valve null shift value and a controller output current value is utilized to calculate the null shift value, wherein the relation formula Z (n) is (1-alpha) multiplied by Z (n-1) + alpha multiplied by I (n). In the formula: i (n) and Z (n) respectively represent the output current value of the controller at the time n and the zero drift value of the servo valve at the time n, and the zero drift value of the servo valve is kept unchanged in a load state; z (n-1) represents a servo valve zero drift value at the time of n-1; alpha is an adjusting coefficient;
in this embodiment, the servo valve null shift value Z (n-1) at the previous time (i.e. at time n-1) is 0mA, and the current value I (n) output by the controller at the current time is 0.5 mA.
Step three: determining an adjusting coefficient alpha, wherein the value of alpha is between 0 and 0.02; in the present embodiment, the adjustment coefficient α is 0.01;
in this embodiment, it can be found that the null shift value z (n) of the servo valve at the present moment is 0.005mA, that is, the position of the hydraulic servo valve at which the actual zero output current is 0.005mA is determined, the servo valve extends when the actual zero output current is greater than 0.005mA, and the servo valve contracts when the actual zero output current is less than 0.005 mA. The null shift value at the next moment is corrected continuously according to the self-learning of the relation formula so as to follow the slow change of the null shift of the servo valve, and the simulated result is shown in figure 4.
Step four: as shown in fig. 1, the obtained zero drift value of the servo valve at the current moment is compensated to the output of the controller, so that the change range of the zero drift value of the system is smaller, the consistency of the bidirectional actions of the hydraulic cylinder in the hydraulic servo system is improved, and the closed-loop control precision of the hydraulic servo control system is improved.
Specifically, in the first step, when the hydraulic servo system is working normally and is in an idling state, under the condition of no zero drift compensation device, the output current value of the controller is equal to the given current value of the servo valve, and the given current of the servo valve in actual production is as shown in fig. 3.
Specifically, in the second step, when the hydraulic servo system is in an idle state, the zero drift value of the servo valve is continuously corrected through self-learning; when the hydraulic servo system is in a loaded state, the zero drift value of the servo valve is kept unchanged.
In the method provided by the embodiment of the invention, under the condition of normal oil pressure, if a hydraulic servo system in closed-loop control works normally and is in an idle state, the current value can be controlled by utilizing the servo valve in the past period of time to obtain the null shift value at the current moment, and the null shift value is continuously corrected through self-learning so as to follow the slow change of the null shift of the servo valve; otherwise the null shift value remains unchanged. The obtained null shift value is compensated to the output of the controller, so that the consistency of the two-way action of the hydraulic cylinder in the hydraulic servo system can be improved, the action speed in one direction is prevented from being influenced by the over-small adjustment range in the direction, and the closed-loop control precision of the hydraulic servo system can be effectively improved.
Claims (3)
1. A servo valve null shift determining and compensating method is characterized in that a servo valve null shift value at the current moment is determined by utilizing a servo valve null shift value at the previous moment and a current value output by a controller at the current moment, and the servo valve null shift value at the current moment is continuously corrected through self-learning; compensating the acquired zero drift value of the servo valve at the current moment to the output of the controller so as to improve the consistency of the bidirectional actions of the hydraulic cylinder in the hydraulic servo system and improve the closed-loop control precision of the hydraulic servo control system;
the method comprises the following steps:
the method comprises the following steps: acquiring a controller output current value when a hydraulic servo system in closed-loop control works normally under the condition that the oil pressure is normal;
step two: when the hydraulic servo control system is in an idle state, determining the servo valve null shift value at the current moment by utilizing the servo valve null shift value at the previous moment and the output current value of the controller at the current moment, wherein the relation formula between the servo valve null shift value and the output current value of the controller is as follows:
Z(n)＝(1-α)×Z(n-1)+α×I(n)
in the formula: i (n) and Z (n) respectively represent the output current value of the controller at the time n and the zero drift value of the servo valve at the time n, and the zero drift value is kept unchanged in a load state; z (n-1) represents a servo valve zero drift value at the time of n-1; alpha is an adjusting coefficient; the null shift value can generate slight changes along with the change of time, and the magnitude of the null shift value at the current moment can be determined by adjusting the adjustment coefficient alpha;
step three: determining an adjusting coefficient alpha, wherein the value of alpha is between 0 and 0.02;
step four: and compensating the acquired zero drift value of the servo valve at the current moment to the output of the controller, thereby realizing the improvement of the closed-loop control precision of the system.
2. The method for determining and compensating for servo valve null shift as set forth in claim 1, wherein in step one, when the hydraulic servo system is working normally and in idle condition, the controller outputs current value equal to the given current value of the servo valve under the condition of no null shift compensator.
3. The method for determining and compensating for servo valve null shift as claimed in claim 1, wherein in step two, the servo valve null shift value is continuously corrected by self-learning when the hydraulic servo system is in an unloaded state; when the hydraulic servo system is in a loaded state, the zero drift value of the servo valve is kept unchanged.
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| US4383431A (en) * | 1980-11-03 | 1983-05-17 | The Perkin-Elmer Corporation | Auto-zero system for pressure transducers |
| CN1032554C (en) * | 1994-08-01 | 1996-08-14 | 北京科技大学 | High-precision large-inertia hydraulic servo control system and control method thereof |
| CN100494698C (en) * | 2007-10-31 | 2009-06-03 | 东北大学 | A Method of Dynamic Compensation for Zero Drift of Hydraulic Servo Valve |
| CN102497141B (en) * | 2011-12-06 | 2014-07-02 | 北京特种机械研究所 | High torque starting method for high power alternating current (AC) servo driver |
| CN102632088A (en) * | 2012-03-26 | 2012-08-15 | 唐山钢铁集团微尔自动化有限公司 | Comprehensive control method for constant rolling force and roll gap and with servo valve for compensation |
| CN103995463B (en) * | 2014-05-30 | 2016-07-06 | 北京敬科海工科技有限公司 | A kind of electro-hydraulic proportional valve position servo driving method based on mixture control |
| CN104132015B (en) * | 2014-07-14 | 2016-04-20 | 中冶南方工程技术有限公司 | A kind of rolling mill hydraulic servovalve drift compensation method and device |
| CN108468615B (en) * | 2018-02-05 | 2020-06-30 | 中国长江电力股份有限公司 | Self-adaptive self-positioning method for self-diagnosis of neutral position in hydraulic servo system of speed regulator |
| JP7437980B2 (en) * | 2019-03-12 | 2024-02-26 | 株式会社堀場エステック | Fluid control device, fluid control system, diagnostic method, and program for fluid control device |
| CN111736454B (en) * | 2020-06-04 | 2023-04-18 | 北京科技大学设计研究院有限公司 | Automatic control method of double-servo-valve electro-hydraulic position system |
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