CN115401948A - Stability design and control method for quick-falling motion curve of large hydraulic forming equipment - Google Patents
Stability design and control method for quick-falling motion curve of large hydraulic forming equipment Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B30—PRESSES
- B30B—PRESSES IN GENERAL
- B30B15/00—Details of, or accessories for, presses; Auxiliary measures in connection with pressing
- B30B15/16—Control arrangements for fluid-driven presses
- B30B15/166—Electrical control arrangements
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B30—PRESSES
- B30B—PRESSES IN GENERAL
- B30B15/00—Details of, or accessories for, presses; Auxiliary measures in connection with pressing
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Abstract
The invention discloses a stability design and control method for a fast descending motion curve of large hydraulic forming equipment. Aiming at the problems existing in the control research of the existing fast descent technology, the invention provides a fast descent motion rule design method based on a quintic curve by analyzing the dynamics characteristics of a hydraulic system when a movable cross beam fast descends, an NSGA-II algorithm is applied to solve an optimal motion curve by taking the maximum average speed and the minimum impact as constraints, and a motion curve tracking control strategy based on fuzzy PID is developed. Through simulation and experimental research, the effectiveness of design and control of the rapid-descent motion curve is verified, and the result shows that the impact of the movable cross beam in the rapid-descent motion process is effectively relieved, the reduction amplitude reaches 21%, and the method has important theoretical and application values on the research and development and stability control of large-scale hydraulic equipment.
Description
Technical Field
The invention belongs to the technical field of hydraulic forming equipment, and particularly relates to a stability design and control method for a quick-falling motion curve of large hydraulic forming equipment.
Background
The movable cross beam of the large hydraulic press needs to quickly finish the die assembly process in the descending process so as to prevent the problem of forming quality caused by material temperature change and the like. The movable cross beam of the existing high-power hydraulic forming equipment has sudden speed change in the quick descending process, so that a hydraulic system generates larger impact and unbalance loading. In order to solve the problems of impact and unbalance loading, domestic and foreign scholars make intensive researches on the aspects of hydraulic system structures, control algorithms, motion curves and the like.
In the aspect of hydraulic system structure optimization, researchers have conducted simulation research on cartridge valve opening adjustment, enlarged unloading pipelines, energy accumulator application and overhead type buffer devices, and the effect of relieving impact vibration is achieved to a certain extent. Therefore, the optimization research on the system structure can reduce the problems of impact and vibration in the quick descending process of the movable cross beam, but the traditional structure optimization scheme has higher requirements on the control performance of the hydraulic element.
In the aspect of control algorithm optimization, a predictive multi-mode control technology, a TS neural network control scheme and a radial basis function neural network technology are designed, relatively good stability control results are obtained, but certain tracking errors still exist, and the method cannot adapt to variable production environments. On the basis, researchers design an adaptive backstepping terminal sliding mode controller based on SMOD, and the robustness of the system is improved in the simulation verification of the hydraulic position servo control. The scheme of different control algorithms is comprehensively analyzed, the control algorithm is difficult to be singly quoted in actual production to complete the control process of the quick descending movement of the movable cross beam, and the control requirement of the quick descending movement of the movable cross beam cannot be met.
In the aspect of motion curves, DU and the like firstly analyze cubic polynomial motion trajectories in the research on variable-speed falling motion of a movable cross beam, but the cubic curves have poor capability of responding to impact effects caused by sudden speed change, and the problem of impact generated in the motion analysis process cannot be thoroughly solved. And secondly, optimizing the steepest descent curve without impact by using a multi-island genetic algorithm to obtain a reasonable quintic curve equation, and effectively solving the impact problem in the rapid descent of the movable cross beam. The research shows that the motion impact can be better relieved through the optimization of the motion curve, but how to improve the fast descending speed and the production efficiency while reducing the impact still needs to be further researched.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a stable design and control method for a quick-falling motion curve of large-scale hydraulic forming equipment. The hydraulic forming device aims at solving the technical problem that a hydraulic system generates larger impact and unbalance loading due to speed mutation in the quick descending process of the movable cross beam of the existing high-power hydraulic forming device.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a stable design structure of a fast descending motion curve of large hydraulic forming equipment in a first aspect, which comprises a hydraulic oil way of a forming hydraulic machine and a control system, wherein the system comprises:
the pump set is used for supplying oil to the system;
a check valve for preventing reverse flow of the oil flow;
the energy accumulator is used for storing redundant energy and releasing the energy when needed;
the first plug-in valve group is used for playing a role of opening and closing an oil way in the main oil way;
the electromagnetic valve is used for controlling the on-off of the oil path;
a first relief valve: the overflow protection device is used for performing an overflow protection effect on the oil return pipeline, one end of the overflow protection device is connected with the oil return pipeline, and the other end of the overflow protection device is connected with the oil tank;
the second overflow valve is used for performing an overflow protection effect on the oil inlet pipeline, one end of the second overflow valve is connected with the oil inlet pipeline, and the other end of the second overflow valve is connected with the oil tank;
the first pressure sensor is used for monitoring the pressure change of the oil return pipeline, one end of the first pressure sensor is connected to the oil return pipeline, and the other end of the first pressure sensor is connected to the control computer set;
the second pressure sensor is used for monitoring the pressure change of the oil inlet pipeline, one end of the second pressure sensor is connected with the oil inlet pipeline, and the other end of the second pressure sensor is connected with the control computer set;
the built-in displacement sensor is used for feeding back the stroke of the hydraulic cylinder, is arranged in the hydraulic cylinder, extends out of a signal wire and is connected with the control computer set;
the hydraulic cylinder is used as a hydraulic system executing mechanism;
the high-frequency response electromagnetic valve is used for accurately controlling the flow of the oil return pipeline so as to achieve accurate control of the stroke of the hydraulic cylinder;
the second plug-in valve group is used for performing a pressure relief effect in the oil return pipeline, one end of the second plug-in valve group is connected to the oil return pipeline, and the other end of the second plug-in valve group is connected to the oil tank;
the third plug-in valve group is used for performing oil return control on a pump port when the first plug-in valve group is closed and the pump group is not closed, one end of the third plug-in valve group is connected with an oil inlet path, and the other end of the third plug-in valve group is connected with an oil tank;
the oil tank is used for storing hydraulic oil required by the system;
and the control computer set is used for processing the feedback information, making a judgment, and controlling the on-off of the electromagnetic valve so as to control the speed of the hydraulic cylinder.
The second aspect of the invention provides a stability control method for a rapid descending motion curve of large-scale hydraulic forming equipment based on the design structure, which comprises the following steps:
s1, modeling a hydraulic system: designing a hydraulic oil circuit and a control system of the forming hydraulic machine, wherein the open-loop transfer function of the system is shown as the following formula (5):
wherein the content of the first and second substances,
；
s2, establishing a target motion curve function by adopting a quintic spline curve, designing a motion quintic curve motion model, and solving an optimal movable cross beam descending motion curve by applying an NSGA-II algorithm;
and S3, designing a self-adjusting fuzzy PID controller.
Preferably, in step S2, the designing of the motion quintic curve motion model and the applying of the NSGA-II algorithm to obtain the optimal movable beam descending motion curve specifically include:
a21, according to the set conditions and parameters, listing a general expression of a fifth-order polynomial curve as the following formula (6) and an optimization constraint equation set of the following formula (7):
wherein A is 0 、A 1 、A 2 、A 3 、A 4 And A 5 Is a polynomial coefficient, t is the total movement time of the movable cross beam, Y is the movement displacement of the movable cross beam, V is the movement speed of the movable cross beam, a is the movement acceleration of the movable cross beam, and J is the movement inertia of the movable cross beam; in the formula 7, the shortest motion time and the smallest impact are taken as optimization constraint conditions;
and A22, setting the optimized initial conditions of the quintic curve according to the starting point state and the end point state of the movement as follows:
starting point conditions:Y(t 0 )=Y 0 (m)，V(t 0 )=V 0 (m/s)，a(t 0 )=a 0 (m/s 2 )，J(t 0 )= J 0 (m/s 3 )；
end point conditions:Y(t s )=Y s (m)，V(t s )=V s (m/s)，a(t s )=a s (m/s 2 )，J(t s )=J s (m/s 3 )
wherein the content of the first and second substances,t 0 as a starting pointThe time of day is,t s the motion end point time is one of parameters needing to be optimized;Y 0 、V 0 、a 0 displacement, velocity, acceleration and jerk at the origin, correspondingY s 、V s 、a s AndJ s displacement, velocity, acceleration and jerk at the end of the motion.
A23, reasonable constraint conditions are given, and the optimization solution is as follows: assuming that the movable cross beam does free fast descending motion in an ideal limit state, setting a state constraint condition of quintic curve optimization according to parameter data, and preliminarily solving the maximum acceleration and the maximum speed according to known system parameters, wherein the solving process of related parameters is shown as the following formula (8):
wherein F is the slider gravity (N) borne by the piston rod of the oil cylinder, and F 1 The tension (N, F) of the negative pressure of the oil inlet to the piston during quick drop 2 The pressure reaction force (N) generated at the oil outlet when the piston rod is quickly lowered, f is the resistance (N) borne by the piston rod when the piston rod moves, m is the mass (kg) of the sliding block, a 1 Is the average acceleration (m/s) of the movable cross beam during falling 2 )，t 1 For a descent time (S), S is a nominal descent displacement (m), and g is set to 10m/S 2 ，P 1 Pressure intensity (MPa) of oil inlet of oil cylinder A 1 Is the area of the inlet piston (m) 2 )，P 2 The pressure (MPa) of the oil outlet of the oil cylinder A 2 The contact area (m) of the bottom of the piston rod of the oil outlet and the oil 2 )，f c Is the viscous friction coefficient of the oil cylinder, V 1 Is the piston rod movement speed (m/s). F 3 The maximum reaction force (N) of the oil outlet of the oil cylinder to the piston rod during the deceleration, f' is the maximum friction force (N) borne by the oil cylinder during the deceleration, a 2 Is the maximum deceleration (m/s) of the piston rod 2 ) (ii) a Wherein, P 3 The maximum pressure (MPa) applied to the oil outlet of the oil cylinder.
Preferably, in step S3, the self-adjusting fuzzy PID controller is composed of PThe two modules of the ID and the fuzzy logic controller are connected in parallel, wherein the displacement error and the error change rate are used as input, and the real-time K is output by the fuzzy logic controller p 、K d And K i And establishing the interaction between the PID module and the fuzzy logic controller according to the displacement error.
Preferably, the method further comprises the following steps: the AMEsim and Simulink combined simulation verifies the effectiveness of design and control of the fast descent motion curve, and the method specifically comprises the following steps: establishing a simulation model of a hydraulic system in AMEsim, establishing a design control system in Simulink, and setting a PID control group for a control scheme to perform simulation test; selecting a corresponding solution scheme according to the established model, constraint conditions and known parameters, and optimizing the curve model; and calculating the optimal solution under the conditions of the fastest speed, the minimum impact and the shortest time by adopting an NSGA-II algorithm to obtain an optimal solution coordinate curve.
Preferably, the method further comprises the following steps: and verifying the correctness and the effectiveness of the simulation analysis result.
The invention has the following beneficial effects:
the invention provides a quintic curve-based rapid-descent motion rule design method by analyzing the dynamic characteristics of a hydraulic system when a movable cross beam rapidly descends, solves an optimal motion curve by applying an NSGA-II algorithm with the maximum average speed and the minimum impact as constraints, and develops a motion curve tracking control strategy based on fuzzy PID. The effectiveness of design and control of the rapid descending motion curve is verified through simulation and experimental research, and the result shows that the impact of the movable cross beam in the rapid descending motion process is effectively relieved, the reduction amplitude reaches 21 percent, and the method has important theoretical and application values on the research and development and stability control of large-scale hydraulic equipment.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a movement displacement diagram of a descending movement curve of a movable cross beam;
FIG. 2 is a schematic diagram of a hydraulic circuit and control system of a forming hydraulic machine designed according to this invention;
FIG. 3 is a block diagram of hydraulic servo displacement feedback;
FIG. 4 is a transmission block diagram of a high-frequency response proportional servo valve-controlled hydraulic cylinder control system;
FIG. 5 is a flow chart of the fuzzy PID controller action;
FIG. 6 is a schematic diagram of a simulation control system;
FIG. 7 is a graph of the rapid lowering movement of the movable beam;
FIG. 8 is a graph of displacement tracking;
FIG. 9 is a tracking error graph;
FIG. 10 is a comparison of the speed of movement under the PID controller and the fuzzy PID controller;
FIG. 11 is a graph comparing acceleration under a PID controller and a fuzzy PID controller;
FIG. 12 is a pressure comparison plot of the lower oil outlets of the PID controller and the fuzzy PID controller;
FIG. 13 is a graph of the effect of displacement tracking in the analysis results of the displacement tracking experiment;
FIG. 14 is a velocity profile of the results of a displacement tracking experiment analysis;
fig. 15 is a graph of acceleration in the results of the displacement tracking experimental analysis.
Reference numerals are as follows: 1. a pump group; 2. a one-way valve; 3. an accumulator; 4. a first valve cartridge group; 5. an electromagnetic valve; 6. a first overflow valve; 7. a second overflow valve; 8. a first pressure sensor; 9. a second pressure sensor; 10. a built-in displacement sensor; 11. a hydraulic cylinder; 12. a high-frequency sound electromagnetic valve; 13. a second valve cartridge group; 14. a third valve plug-in mounting group; 15. an oil tank; 16. controlling the computer group.
Detailed Description
In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular system structures, techniques, etc. in order to provide a thorough understanding of the embodiments of the invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. In other instances, detailed descriptions of well-known systems, devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail.
Example 1
Referring to FIG. 1, the movement of the movable beam in a high power hydroforming apparatus is essentially divided into seven phases, T 1 To T 2 Is a fast descent stage, T 2 To T 3 For a deceleration phase, T 3 To T 4 For the working in stage, T 4 To T 7 Second T for pressing and pressure maintaining stage 7 To T 10 Respectively comprising the stages of mold opening, quick return and deceleration. Because a plurality of deceleration points are arranged in the moving process of the movable cross beam in the traditional scheme, the movable cross beam is enabled to be at T 4 The proper pressing speed is achieved, but the movable cross beam has larger inertia and generates larger impact at the speed inflection point. Therefore, in order to reduce the motion impact, the hydraulic system from the quick lowering starting point to the mold closing stage which is difficult to solve is selected for analysis.
Specifically, referring to fig. 2, in order to realize accurate control of a motion curve in the process of rapid descent of a movable cross beam, the invention provides a stable design structure of a rapid descent motion curve of large hydraulic forming equipment, which comprises a hydraulic oil circuit of a forming hydraulic machine and a control system, wherein the system comprises: the pump unit 1 is used for supplying oil to the system; a check valve 2 for preventing the reverse flow of the oil flow; the energy accumulator 3 is used for storing redundant energy and releasing the energy when needed; the first plug-in valve group 4 is used for playing a role of opening and closing an oil way in a main oil way; the electromagnetic valve 5 is used for controlling the on-off of an oil way; first relief valve 6: the overflow protection device is used for performing an overflow protection effect on an oil return pipeline, one end of the overflow protection device is connected with the oil return pipeline, and the other end of the overflow protection device is connected with the oil tank 15; the second overflow valve 7 is used for performing an overflow protection effect on the oil inlet pipeline, one end of the second overflow valve is connected with the oil inlet pipeline, and the other end of the second overflow valve is connected with the oil tank 15; the first pressure sensor 8 is used for monitoring the pressure change of the oil return pipeline, one end of the first pressure sensor is connected with the oil return pipeline, and the other end of the first pressure sensor is connected with the control computer set 16; the second pressure sensor 9 is used for monitoring the pressure change of the oil inlet pipeline, one end of the second pressure sensor is connected with the oil inlet pipeline, and the other end of the second pressure sensor is connected with the control computer set 16; a built-in displacement sensor 10 for feeding back the stroke of the hydraulic cylinder 11, which is arranged inside the hydraulic cylinder 11, extends out of a signal wire and is connected with a control computer set 16; the hydraulic cylinder 11 is used as a hydraulic system actuating mechanism; the high-frequency response electromagnetic valve 12 is used for accurately controlling the flow of an oil return pipeline to achieve accurate control over the stroke of the hydraulic cylinder 11; the second plug-in valve group 13 is used for performing a pressure relief function in the oil return pipeline, one end of the second plug-in valve group is connected to the oil return pipeline, and the other end of the second plug-in valve group is connected to the oil tank 15; the third valve plug-in mounting group 14 is used for performing oil return control on a pump port when the first valve plug-in mounting group 4 is closed and the pump group 1 is not closed, and one end of the third valve plug-in mounting group is connected to an oil inlet path while the other end of the third valve plug-in mounting group is connected to an oil tank 15; the oil tank 15 is used for storing hydraulic oil required by the system; and the control computer set 16 is used for processing the feedback information, making a judgment, and controlling the on-off of the electromagnetic valve 5 so as to control the speed of the hydraulic cylinder 11. Here, the invention sets up the high frequency response electromagnetic valve 12 on the oil return path, can control the flow size in the oil circuit accurately; the hydraulic cylinder 11 with the built-in displacement sensor 10 is used for processing displacement signals by a computer and outputting control signals, so that the real-time stable control of the speed and the pressure of the movable cross beam in the descending process can be realized.
The embodiment of the invention also provides a stability control method of a rapid descending motion curve of large hydraulic forming equipment based on the design structure, which comprises the following steps:
s1, modeling a hydraulic system: based on the designed hydraulic oil circuit and control system of the forming hydraulic machine, the dynamic characteristics of the hydraulic system when the movable cross beam quickly descends are analyzed.
Specifically, no load acts during the fast descending process of the movable cross beam, and a block diagram of the hydraulic servo system is obtained, as shown in fig. 3. The system combines related parameters to approximate a common electro-hydraulic servo valve into a second-order oscillation system, wherein the open-loop transfer function of the electro-hydraulic servo valve is shown as the following formula (1):
wherein, K SV As flow gain of the servo valve, G SV Is K SV A servo valve transfer function when =1,
being the natural frequency of the servo valve,
s is 0.7 for the damping ratio of the servo valve.
According to the actual situation analysis, the external load in the process of quickly descending the movable cross beam is 0, and the displacement x of the hydraulic cylinder can be obtained according to the analysis p Input command x to the valve v The transfer function of (3) is represented by the following formula (2):
wherein, K q Is the flow coefficient, A p The effective area of the piston of the hydraulic cylinder is,
is the natural frequency of the hydraulic cylinder,
the hydraulic damping ratio is generally 0.1-0.2.
In addition, the current of the servo amplifier
And an input voltage U g Approximately proportional, using servo proportional amplifier gain K a Specifically, the following formula (3):
wherein a displacement sensor gain K can be established f The mathematical model of (3) is shown in the following formula (4):
wherein, I f Is a feedback current signal, V; y is the hydraulic cylinder piston displacement, m.
Finally, a high-frequency response rate servo valve-controlled hydraulic cylinder control system transfer block diagram is derived through the above equations (1) to (4), as shown in fig. 4.
From the results of fig. 4, the system open-loop transfer function is shown in the following formula (5):
wherein the content of the first and second substances,
。
s2, establishing a target motion curve function by utilizing a quintic spline curve, designing a motion quintic curve motion model, and solving an optimal movable cross beam descending motion curve;
specifically, a general expression of a fifth-order polynomial curve as the following formula (6) and an optimization constraint equation set of the following formula (7) are listed according to the set conditions and parameters:
wherein, A 0 、A 1 、A 2 、A 3 、A 4 And A 5 Is a polynomial coefficient, t is the total movement time of the movable cross beam, Y is the movement displacement of the movable cross beam, V is the movement speed of the movable cross beam, a is the movement acceleration of the movable cross beam, and J is the movement inertia of the movable cross beam; in equation 7, the shortest motion time and the smallest impact are used as the optimization constraints.
According to the motion characteristics of the descending motion curve of the movable cross beam shown in fig. 2, the quintic curve designed in the rapid descending process is divided into two stages of variable acceleration and variable deceleration motions. The optimal initial conditions of the quintic curve according to the starting point state and the end point state of the movement are set as follows:
starting point conditions:Y(t 0 )=Y 0 (m)，V(t 0 )=V 0 (m/s)，a(t 0 )=a 0 (m/s 2 )，J(t 0 )= J 0 (m/s 3 )；
end point conditions:Y(t s )=Y s (m)，V(t s )=V s (m/s)，a(t s )=a s (m/s 2 )，J(t s )=J s (m/s 3 ) 。
wherein the content of the first and second substances,t 0 in order to be the time of the starting point,t s the motion endpoint time is one of the parameters needing to be optimized.Y 0 、V 0 、a 0 Displacement, velocity, acceleration and jerk at the origin, correspondingY s 、V s 、a s AndJ s displacement, velocity, acceleration and jerk at the end of the motion.
In order to achieve the result of obtaining the optimal solution, reasonable constraint conditions need to be given for optimal solution. Specifically, it is assumed that the movable cross beam performs free fast-descending motion in an ideal limit state, and a state constraint condition for quintic curve optimization is set according to parameter data. The maximum acceleration and the maximum speed are solved preliminarily according to the known system parameters, and the solving process of the related parameters is shown as the following formula (8):
wherein F is the slider gravity (N) borne by the piston rod of the oil cylinder (hydraulic cylinder), and F 1 The tension (N, F) of the negative pressure of the oil inlet to the piston during quick drop 2 The pressure reaction force (N) generated at the oil outlet when the oil is quickly dropped, f is the resistance (N) borne by the piston rod when the piston rod moves, m is the mass (kg) of the sliding block, a 1 Is the average acceleration (m/s) of the movable cross beam during falling 2 )，t 1 For a descent time (S), S is a nominal descent displacement (m), and g is set to 10m/S 2 ，P 1 Pressure intensity (MPa) of oil inlet of oil cylinder A 1 Is the area of the inlet piston (m) 2 )，P 2 The pressure (MPa) of the oil outlet of the oil cylinder A 2 The contact area (m) of the bottom of the piston rod of the oil outlet and the oil 2 )，f c Is the viscous friction coefficient of the oil cylinder, V 1 The motion speed (m/s) of the piston rod; f 3 The maximum reaction force (N) of the oil outlet of the oil cylinder to the piston rod during the deceleration, f' is the maximum friction force (N) borne by the oil cylinder during the deceleration, a 2 For maximum deceleration (m/s) of the piston rod 2 ) (ii) a Wherein, P 3 The maximum pressure (MPa) applied to the oil outlet of the oil cylinder.
S3, designing a self-adjusting fuzzy PID controller;
in order to research the motion model pair to reduce fast falling impact, improve displacement accuracy and overcome nonlinear motion effects, the invention designs a self-adjusting fuzzy PID controller. The fuzzy PID controller with good self-adaptive characteristic, simple structure and stable work can make up the defects of the PID controller and can be matched with a system and a motion model. The fuzzy PID controller designed in the research is divided into two modules of PID and fuzzy logic controller, as shown in FIG. 5. Wherein the displacement error and error change rate are used as input, and real-time K is output via the fuzzy logic controller p 、K d And K i . And establishing the interaction between the PID module and the fuzzy logic controller by using the displacement error.
It is known that the object directly affected by the fuzzy controller in the system under study is a high frequency response valve. At this time, the correlation of the displacement error and the error change rate with the set fuzzy controller output value needs to be resolved by the characteristics of the fuzzy PID controller. Then, the fuzzy rule setting and the output parameter quantification are completed according to the corresponding control requirements. Wherein, the fuzzy rule determines the quality of the fuzzy controller, and different motion conditions need to be specifically set with a specific fuzzy rule. In order to achieve a high degree of accuracy in the control, the fuzzy rules of the system are set as shown in table 1 below.
TABLE 1. K p 、K i 、K d Fuzzy rule
Example 2
The design in example 1 was verified by simulation and experiment.
The design scheme in the embodiment 1 is verified through AMEsim and Simulink combined simulation;
(1) As shown in table 2 below, the structure of the simulation system is shown.
TABLE 2 Main Hydraulic Components and their parameters
According to the schematic diagram of the hydraulic system in fig. 2, a simulation model of the hydraulic system is constructed in AMEsim, and specific hydraulic component models and simulation parameters are set as shown in table 2. Meanwhile, a design control system is built in Simulink, and the control system is modeled as shown in FIG. 6. And a PID control group was set for the control scheme. And (4) performing simulation test by combining software.
In addition, the input tracking error e and the error change rate e of the fuzzy controller are finally set by combining the design of the control system and the motion range parameters of the movable beam c The quantization domain of (1) is (-0.6, -0.4, -0.2,0,0.2,0.4, 0.6). Obtaining an output variable proportionality coefficient K in experimental simulation p Integral coefficient K i And a differential coefficient K d The quantization discourse domain of (c). K p Is (0, 5, 10, 15, 20, 25, 30). K is i Is (0, 0.09,0.17,0.25,0.33, 0.5). K d Is (0, 0.05,0.1,0.15,0.20,0.25, 0.3). Second, the quantization factor is for the error e and the rate of change of the error e c With reference to the setting of the stroke of the cylinder of 0.6m, K can be obtained e =0.6/0.6，K ec =0.6/0.6。
(2) Curve optimization solving
And selecting a corresponding solution scheme according to the established model, the constraint conditions and the known parameters, and optimizing the curve model. Through comparative analysis of the existing solving method, the embodiment of the invention adopts the NSGA-II algorithm to solve the optimal solution of the equation. Wherein, the motion situation of the movable beam can be known,
Y 0 =0(m)；V 0 =0(m/s)；a 0 =0(m/s 2 )；t 0 =0(s)；Y s =0.6(m)；a max =6(m/s 2 )。
(3) Analysis of simulation results
According to the analysis of the optimized result, the quintic curve motion model well meets the design requirements, the optimal solution meeting the conditions of the fastest speed, the minimum impact and the shortest time is obtained, and the coordinate curve of the optimal solution is shown in fig. 7.
In the simulation process, the system response is tracked by the ideal quintic curve after being optimized by the motion curve as shown in FIG. 8, and the tracking error is shown in FIG. 9. In a simulation system, within 0.8s, displacement curves of the movable cross beam have certain fluctuation, but fluctuation errors of the displacement curves are small and are within 2-10 mm. From the results of fig. 8, it is understood that the displacement error gradually decreases after 1.4 s. Wherein, the termination error under the action of the PID controller is 3.02mm, and the termination error under the action of the fuzzy PID controller is only 1.7mm.
Therefore, the simulation analysis effectively embodies that the model after the quintic curve optimization can obtain good system control tracking effect and response speed, can meet the requirements of speed and stability for system operation in design, and the control precision of the fuzzy PID is improved by 43.7 percent relative to the PID controller.
Referring to fig. 10 to 12, in the simulation process, the vibration amplitude of the optimized motion model is significantly smaller than that of the conventional motion control scheme. The maximum speed fluctuation under the action of the fuzzy PID controller and the PID controller is respectively improved by 60% and 40%, particularly after 1.4 seconds, the speed and the acceleration of the optimized motion model are stably reduced under the action of the corresponding controllers, and the phenomenon of sudden change of termination speed in the traditional scheme does not exist.
Secondly, as can be seen from the results in fig. 12, in the stage from the movement traverse rapid descending movement to the deceleration, the pressure abrupt fluctuation of 1000bar exists in the conventional scheme, while the pressure fluctuation of the optimized model in 0-1.4s is only 450bar at most and has no abrupt fluctuation, and the shortest fluctuation time is 0.04s. Therefore, the optimized model not only can effectively reduce impact vibration, but also can be stably matched with a traditional PID controller and a fuzzy PID controller and operated.
In addition, compared with the traditional PID control, the motion speed fluctuation of the movable cross beam is improved by 33.3% and the speed precision is improved by 2.9% under the action of the fuzzy PID controller. And as can be seen from the results in fig. 12, in the motion process under the action of the fuzzy PID controller, the pressure fluctuation is smaller, and after 1.6s, the comprehensive pressure value is obviously smaller than that of the PID controller. Most importantly, after the movement is stopped, the pressure value under the action of the PID controller is 300bar, and the pressure value in the fuzzy PID controller is only 230bar, so that the die deflection caused by overlarge pressure in the die closing process is avoided. Therefore, the optimized motion curve has the effects of high motion precision and low impact vibration under the coordination of the fuzzy PID controller.
(II) verifying the design scheme in the example 1 through experiments;
(1) The test bed of the hydraulic forming equipment is built, and meanwhile, a PID and fuzzy PID control system contrast group is set in an experiment and is respectively applied to motion control of curves:
in order to further research and verify the correctness and the effectiveness of the simulation analysis of the optimized motion curve model, the invention builds a hydraulic forming equipment test bed, and hydraulic elements and related parameters thereof are shown in a table 2. And the tracking of the ideal five-time motion curve is completed by performing displacement control on the master cylinder. The hydraulic machine is also provided with a pressure sensor, a speed sensor and the like. These sensors are mounted in the hydraulic machine frame and return line for monitoring the operating status of the system. In addition, the control system is integrated in the electrical cabinet and the console, and mainly comprises a personal computer, an industrial personal computer, an acquisition card, an output card and the like. The personal computer as main control computer exchanges TCP/IP data with the industrial control computer as target computer via network cable.
(2) Displacement tracking experimental analysis
The experimental results are shown in fig. 13 to 15. Wherein t is the movement time, s is the displacement of the movable cross beam, v is the movement speed of the movable cross beam, and a is the movement acceleration of the movable cross beam. In the embodiment of the invention, two control schemes are selected for experiments and respectively matched with the motion model for verification.
As can be seen from the results of fig. 13 to 15, in both cases of the controller, the movable beam was vibrated for 0.87s of movement time. Wherein, the fuzzy PID controller reduces the vibration of the movable beam, so that the integral displacement parameters are all larger than ideal displacement parameters, but the error is within 0-23.15mm and gradually approaches to 0; the displacement error of the PID controller in this time is in the range of 0-16.9mm and gradually approaches 0.
Secondly, the actual displacement curve under the action of the two controllers gradually tends to be stable after 0.8s, and the displacement error can still be stably reduced within 1.9s-2 s. Finally, the displacement error when the PID controller terminates the motion is 4.02mm (3.775%), and the displacement termination error of the fuzzy PID controller is only 2.7mm (2.825%). Because the simulation model is ideal and has no structural problem, the experimental error is about 1mm larger than the simulation error. However, the experimental result of the displacement accuracy of the model is still improved by about 20 percent compared with the traditional scheme.
Note that the velocity fluctuation was large before 0.8s, but the five times motion curve was converged. And after the movement speed is 1.2s, the device not only can move at a higher speed, but also has obviously reduced fluctuation. Wherein, the speed is stably reduced after 1.6s, the displacement termination speed error of the PID controller is 14.2%, and the speed error of the fuzzy PID controller is 10.8%. Further, the value of the pressure causing the vibration shock in the system is reduced by 20% by the oil outlet pressure detection data analysis of fig. 11.
(III) simulation and experimental result analysis:
(1) System stationarity promotion analysis
Through simulation and experimental analysis, compared with the traditional movable beam motion model, the optimized model well eliminates the problem of speed mutation in the motion process by a fifth-order polynomial motion curve model. In the process of the quick descending movement of the movable cross beam, the movement model eliminates the problems of impact and vibration caused by sudden speed change to the maximum extent. Meanwhile, the Simulink real platform of the industrial personal computer can complete better production application under the cooperation of the fuzzy PID controller and the high-frequency response valve, and lays a foundation for the application of a more advanced control algorithm.
(2) Controller application analysis
As shown in fig. 13 to 15, during the movement of the movable cross beam, within 0-0.8s, the movement under the action of the two controllers has certain fluctuation. However, under the action of the fuzzy PID controller, the displacement fluctuation error is reduced by 7.25mm relative to the PID controller, and meanwhile, in order to avoid large-range speed fluctuation caused by large inertia of the movable cross beam when the movable cross beam is started, the fuzzy PID controller allows the movement displacement to be advanced within 0.8s, so that the purpose of reducing the speed fluctuation is achieved. Secondly, it can be derived from the above chart that the error accuracy of the fuzzy PID controller is smaller compared to the PID controller. Wherein, the precision of the termination displacement is improved by 1.32mm (44%), and the speed precision is improved by 0.06m/s 2 (2.9%). The reduction is 20%. According to simulation and experimental analysis, the fuzzy PID controller can solve the problems of nonlinear impact vibration and large error in the descending process of the movable beam.
In conclusion, in order to solve the problems of impact and vibration in the process of quickly lowering the movable cross beam, the invention provides a stability control method based on a quintic motion curve rule, and simulation and experiment results show that motion impact and vibration are obviously reduced, and non-impact controllable nonlinear motion of the movable cross beam can be realized. Finally, the displacement tracking efficiency of the movable cross beam reaches 97%, the vibration impact is slowed down by 21%, and the production quality and the service life of the high-power hydraulic forming equipment are effectively improved and reduced quickly. Therefore, the method can provide effective reference for the design and stability control of the existing large hydraulic machine, and can meet more rigorous process requirements through continuous improvement and promote the development of the high-precision and high-stability hydraulic machine.
The present invention is not limited to the above-described embodiments, and various modifications made by those skilled in the art without inventive skill from the above-described conception fall within the scope of the present invention.
Claims (6)
1. A stability design structure of a fast descending motion curve of large hydraulic forming equipment comprises a hydraulic oil circuit of a forming hydraulic machine and a control system, and is characterized in that the system comprises:
the pump unit (1) is used for supplying oil to a system;
a check valve (2) for preventing the reverse flow of the oil flow;
the energy accumulator (3) is used for storing redundant energy and releasing the energy when needed;
the first plug-in valve group (4) is used for playing a role of opening and closing an oil way in the main oil way;
the electromagnetic valve (5) is used for controlling the on-off of the oil way;
first relief valve (6): the overflow protection device is used for performing an overflow protection effect on an oil return pipeline, one end of the overflow protection device is connected with the oil return pipeline, and the other end of the overflow protection device is connected with an oil tank (15);
the second overflow valve (7) is used for performing an overflow protection effect on the oil inlet pipeline, one end of the second overflow valve is connected with the oil inlet pipeline, and the other end of the second overflow valve is connected with the oil tank (15);
the first pressure sensor (8) is used for monitoring the pressure change of the oil return pipeline, one end of the first pressure sensor is connected with the oil return pipeline, and the other end of the first pressure sensor is connected with the control computer set (16);
the second pressure sensor (9) is used for monitoring the pressure change of the oil inlet pipeline, one end of the second pressure sensor is connected with the oil inlet pipeline, and the other end of the second pressure sensor is connected with the control computer set (16);
the built-in displacement sensor (10) is used for feeding back the stroke of the hydraulic cylinder (11), is arranged in the hydraulic cylinder (11), extends out of a signal wire and is connected with the control computer set (16);
the hydraulic cylinder (11) is used as a hydraulic system actuating mechanism;
the high-frequency response electromagnetic valve (12) is used for accurately controlling the flow of the oil return pipeline to achieve accurate control on the stroke of the hydraulic cylinder (11);
the second plug-in valve group (13) is used for performing a pressure relief effect in the oil return pipeline, one end of the second plug-in valve group is connected to the oil return pipeline, and the other end of the second plug-in valve group is connected to the oil tank (15);
the third plug-in valve group (14) is used for performing oil return control on a pump port when the first plug-in valve group (4) is closed and the pump group (1) is not closed, one end of the third plug-in valve group is connected to an oil inlet path, and the other end of the third plug-in valve group is connected to an oil tank (15);
the oil tank (15) is used for storing hydraulic oil required by the system;
and the control computer set (16) is used for processing the feedback information, making a judgment, controlling the on-off of the electromagnetic valve (5) and further controlling the speed of the hydraulic cylinder (11).
2. A stability control method for a rapid descending motion curve of a large-scale hydraulic forming device based on the design structure of claim 1 is characterized by comprising the following steps:
s1, modeling of a hydraulic system: designing a hydraulic oil circuit and a control system of the forming hydraulic machine, wherein the system open loop transfer function of the system is shown as the following formula (5):
wherein the content of the first and second substances,
；
s2, establishing a target motion curve function by adopting a quintic spline curve, designing a motion quintic curve motion model, and obtaining an optimal descending motion curve of the movable cross beam by applying an NSGA-II algorithm;
and S3, designing a self-adjusting fuzzy PID controller.
3. The stationarity control method for the fast descending motion curve of the large-scale hydroforming equipment according to claim 2, wherein in step S2, the design motion quintic curve motion model is applied to the NSGA-II algorithm to obtain the optimal descending motion curve of the movable cross beam, and the specific steps are as follows:
a21, according to the set conditions and parameters, listing a general expression of a fifth-order polynomial curve as the following formula (6) and an optimization constraint equation set of the following formula (7):
wherein, A 0 、A 1 、A 2 、A 3 、A 4 And A 5 Is a polynomial coefficient, t is the total movement time of the movable cross beam, Y is the movement displacement of the movable cross beam, V is the movement speed of the movable cross beam, a is the movement acceleration of the movable cross beam, and J is the movement inertia of the movable cross beam; in the formula (7), the shortest motion time and the shortest impact are taken as optimization constraint conditions;
and A22, setting the optimized initial conditions of the quintic curve according to the starting point state and the end point state of the movement as follows:
starting point conditions:Y(t 0 )=Y 0 (m)，V(t 0 )=V 0 (m/s)，a(t 0 )=a 0 (m/s 2 )，J(t 0 )= J 0 (m/s 3 )；
end point conditions:Y(t s )=Y s (m)，V(t s )=V s (m/s)，a(t s )=a s (m/s 2 )，J(t s )=J s (m/s 3 )；
wherein, the first and the second end of the pipe are connected with each other,t 0 in order to be the time of the starting point,t s in order to be the end time of the exercise,Y 0 、V 0 、a 0 as displacements, velocities, accelerations and summations at the starting pointAcceleration, corresponding toY s 、V s 、a s AndJ s displacement, velocity, acceleration and jerk at the end of the motion;
a23, reasonable constraint conditions are given, and the optimization solution is as follows: assuming that the movable cross beam does free fast-descending motion in an ideal limit state, setting a state constraint condition of quintic curve optimization according to parameter data, and preliminarily solving the maximum acceleration and the maximum speed according to known system parameters, wherein the solving process of related parameters is shown in the following formula (8):
wherein F is the slider gravity (N) borne by the piston rod of the oil cylinder, and F 1 The tension (N, F) of the negative pressure of the oil inlet to the piston during quick drop 2 The pressure reaction force (N) generated at the oil outlet when the piston rod is quickly lowered, f is the resistance (N) borne by the piston rod when the piston rod moves, m is the mass (kg) of the sliding block, a 1 Is the average acceleration (m/s) of the movable beam during the fall 2 )，t 1 For a descent time (S), S is a nominal descent displacement (m), and g is set to 10m/S 2 ，P 1 Pressure intensity (MPa) of oil inlet of oil cylinder A 1 Is the area of the inlet piston (m) 2 )，P 2 The pressure (MPa) of the oil outlet of the oil cylinder A 2 The contact area (m) of the bottom of the piston rod of the oil outlet and the oil liquid 2 )，f c Is the viscous friction coefficient of the oil cylinder, V 1 The motion speed (m/s) of the piston rod; f 3 The maximum reaction force (N) of the oil outlet of the oil cylinder to the piston rod during the deceleration, f' is the maximum friction force (N) borne by the oil cylinder during the deceleration, a 2 For maximum deceleration (m/s) of the piston rod 2 ) (ii) a Wherein, P 3 The maximum pressure (MPa) applied to the oil outlet of the oil cylinder.
4. The stationarity control method for fast descending motion curve of large hydraulic forming equipment according to claim 2, wherein in step S3, the self-adjusting fuzzy PID controller comprises two controllers of PID and fuzzy logic controllerThe modules are connected in parallel, wherein the displacement error and the error change rate are used as input, and the real-time K is output through a fuzzy logic controller p 、K d And K i And establishing the interaction between the PID module and the fuzzy logic controller according to the displacement error.
5. A stationarity control method of a fast descending motion curve of a large hydraulic forming equipment according to claim 2, further comprising: the AMEsim and Simulink combined simulation verifies the effectiveness of design and control of the fast descent motion curve, and the method specifically comprises the following steps: establishing a simulation model of a hydraulic system in AMEsim, establishing a design control system in Simulink, and setting a PID control group for a control scheme to carry out simulation test; selecting a corresponding solution scheme according to the established model, constraint conditions and known parameters, and optimizing the curve model; and calculating the optimal solution under the conditions of the fastest speed, the minimum impact and the shortest time by adopting an NSGA-II algorithm to obtain an optimal solution coordinate curve.
6. A stationarity control method of a fast descending motion curve of a large hydraulic forming equipment according to claim 5, further comprising: and verifying the correctness and the validity of the simulation analysis result.
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