CN111622996B - Heterogeneous multi-valve parallel drive electro-hydraulic servo system and control method - Google Patents
Heterogeneous multi-valve parallel drive electro-hydraulic servo system and control method Download PDFInfo
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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
- F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
- F15B11/08—Servomotor systems without provision for follow-up action; Circuits therefor with only one servomotor
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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
- F15B13/04—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor
- F15B13/0401—Valve members; Fluid interconnections therefor
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
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- F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
- F15B15/20—Other details, e.g. assembly with regulating devices
- F15B15/28—Means for indicating the position, e.g. end of stroke
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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
- F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
- F15B21/04—Special measures taken in connection with the properties of the fluid
- F15B21/041—Removal or measurement of solid or liquid contamination, e.g. filtering
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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
- F15B21/00—Common features of fluid actuator systems; Fluid-pressure actuator systems or details thereof, not covered by any other group of this subclass
- F15B21/08—Servomotor systems incorporating electrically operated control means
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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
- F15B2211/00—Circuits for servomotor systems
- F15B2211/30—Directional control
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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
- F15B2211/00—Circuits for servomotor systems
- F15B2211/30—Directional control
- F15B2211/315—Directional control characterised by the connections of the valve or valves in the circuit
- F15B2211/31523—Directional control characterised by the connections of the valve or valves in the circuit being connected to a pressure source and an output member
- F15B2211/31529—Directional control characterised by the connections of the valve or valves in the circuit being connected to a pressure source and an output member having a single pressure source and a single output member
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Abstract
The invention discloses a heterogeneous multi-valve parallel driving electro-hydraulic servo system and a control method thereof, wherein the heterogeneous multi-valve parallel driving electro-hydraulic servo system comprises a plunger pump, the plunger pump is communicated with a hydraulic cylinder through a plurality of parallel servo valves and proportional valves, a piston rod of the hydraulic cylinder is in signal connection with a displacement sensor, the displacement sensor is in signal connection with an input end of a controller, an output end of the controller is in signal connection with the proportional valves and the servo valves, the controller distributes according to the residual total amount of oil according to the working priority of the proportional valves and the servo valves, and control voltage is set according to the distributed oil. The invention makes up the problems of dead zone, slow response speed and the like of the proportional valve by a multi-valve parallel coordination control method, saves the cost by a parallel structure of heterogeneous multi-valves while meeting the performances of high precision, fast response, large flow and the like, and solves the problems of self-adaptive adjustable parameters, external interference and the like by a self-adaptive robust algorithm.
Description
Technical Field
The invention relates to an electro-hydraulic servo system and control, in particular to a heterogeneous multi-valve parallel driving electro-hydraulic servo system and a control method.
Background
The electro-hydraulic servo is widely applied in industrial production, and along with the technical progress, the requirements on the flow and response speed performance of an electro-hydraulic servo system are higher and higher, so that a large-flow and high-precision electro-hydraulic servo valve is produced. However, the low-speed performance of the high-flow electro-hydraulic servo valve is not ideal and the cost is high. In order to save cost and meet the requirement of high-precision control, the scheme of parallel control by using a plurality of servo valves/proportional valves has certain theoretical and implementation significance.
Chinese patent CN201210467404.2 discloses a "hydraulic parallel speed change-over circuit connection method", which realizes the switching circuit of two times of feeding speeds by connecting two speed regulating valves in parallel and by using the speed regulating valves, and the position control precision of the system is improved by the method. Secondly, the Chinese patent application No. CN200820087129.0 discloses a large-flow high-frequency response electro-hydraulic servo valve based on a parallel pilot stage, the patent provides a method for connecting a plurality of small-flow servo valves in parallel to be equivalent to a large-flow servo valve, then the synchronization of the output flow of each servo valve is realized through a synchronous control algorithm, and the method effectively improves the response precision and the flow of the system.
Although the control accuracy and the response speed of the electro-hydraulic servo system are improved by the methods, the control is usually performed by a synchronous control method because the same valves are connected in parallel, and the synchronous control requires that the performance indexes of the valves in the system are consistent as much as possible, so that the cost of the system is increased and the reliability of the system is reduced.
Disclosure of Invention
The purpose of the invention is as follows: the invention aims to provide a heterogeneous multi-valve parallel drive electro-hydraulic servo system and a control method, and solves the problems of high requirements on performance indexes of valves, low reliability and high cost in synchronous control in the conventional multi-valve parallel system.
The technical scheme is as follows: the heterogeneous multi-valve parallel driving electro-hydraulic servo system comprises a plunger pump, wherein an oil inlet of the plunger pump is connected with an oil tank, an oil outlet of the plunger pump is communicated with all parallel servo valves and proportional valves through a one-way valve and then through a branch, oil return ports of all the servo valves and the proportional valves are communicated with the oil tank through pipelines, oil outlets of all the servo valves and the proportional valves are communicated with a hydraulic cylinder through pipelines, a piston rod of the hydraulic cylinder is in signal connection with a displacement sensor, the displacement sensor is in signal connection with an input end of a controller, and an output end of the controller is in signal connection with all the proportional valves and the servo valves.
The plunger pump is electrically connected with a three-phase motor, and the three-phase motor controls the plunger pump to work.
In order to ensure the pipeline pressure on the main oil return pipeline, the one-way valve is communicated with an oil tank through an oil return branch, and an overflow valve and an oil filter are arranged on the oil return branch.
The invention relates to a control method of an isomerous multi-valve parallel drive electro-hydraulic servo system, which comprises the following steps:
(1) the controller calculates and obtains the target displacement x of the current hydraulic cylinder according to the working time T of the systemdAnd to xdFirst derivative ofSecond derivative ofAnd third derivativeThe displacement sensor R collects the actual displacement x at the current momentpComparing the actual displacement xpAnd a target displacement xdObtaining the displacement deviation e and calculating the first derivative of eSecond derivative ofThird derivative
(2) Calculating to obtain the total flow Q of the hydraulic cylinder according to the obtained target displacement, the displacement deviation and the derivativey(T), the calculation formula is as follows:
wherein d isy、My、By、DyAnd CyAll the parameters are self-adaptive adjustable parameters obtained by a hydraulic system through a mathematical model;
(3) taking the total flow obtained in the step (2) for driving the hydraulic cylinder to move as an initial residual total flow, and taking the initial residual total flow Qyi(T)=Qy(T);
(4) And sequentially distributing the residual total flow to the flow of each proportional valve according to the working priority of each proportional valve, and obtaining the control voltage of the proportional valve in the current control period according to the distributed flow, wherein the control voltage is as follows:
When Q isyi(T)>fi(Upi(T-t)+ΔUpi) Time, proportional valve PiIs set to Upi(T)=Upi(T-t)+ΔUpi;
When Q isyi(T)<fi(Upi(T-t)-ΔUpi) While, the proportional valve PiIs set to Upi(T)=Upi(T-t)-ΔUpi;
When f isi(Upi(T-t)-ΔUpi)≤Qyi(T)≤fi(Upi(T-t)+ΔUpi) When is, Qyi(T) > 0 then the proportional valve PiIs set toQyi(T) < 0, the control voltage is set to
Wherein the content of the first and second substances,indicating the maximum increment of the control voltage, U, per control cyclepimaxIndicating the proportional valve PiMaximum output voltage of, TpiIndicating the proportional valve PiResponse time of spool, DiIndicating the proportional valve PiDead zone of, KpiIndicating the proportional valve PiT denotes a control period, fi(Upi(T-t)+ΔUpi) Indicating the maximum flow f of the proportional valve output of the current control cyclei(Upi(T-t)-ΔUpi) Indicating the minimum flow, U, of the proportional valve output for the current control cyclepi(T-T) represents the voltage output by the proportional valve for the last control cycle;
(5) the residual flow after the flow of each proportional valve is distributed sequentially distributes the flow of each servo valve according to the working priority of the servo valve, and the control voltage of the servo valve in the current control period is obtained according to the distributed flow, which is specifically as follows:
when g isi(Usi(T-t)-ΔUsi)≤Qyi(T)≤gi(Usi(T-t)+ΔUsi) Time, servo valve SiIs set to Usi(T)=Usi(T-t)+ΔUsi;
When Q isyi(T)<gi(Usi(T-t)-ΔUsi) Time, servo valve SiIs set to Usi(T)=Usi(T-t)-ΔUsi;
Wherein S isiIncrement of voltage value ofUsimaxIs a servo valve SiMaximum output voltage of, TsiServo valve SiValve element response time, g i(Usi(T-t)+ΔUsi) Maximum value g representing the possible output flow of the servo valve in the current control periodi(Usi(T-t)-ΔUsi) Represents the minimum value, U, of the flow that can be output by the servo valve in the current control periodsi(T-T) represents the output voltage of the servo valve for the last control cycle;
(6) working time T < Tmax0And (3) carrying out control of the next control period, updating the self-adaptive adjustable parameters, and repeating the steps (1) - (5) until T is more than or equal to Tmax0The system stops the control.
Wherein, the step (1) is according to a preset function xdF (t) calculating the target displacement of the hydraulic cylinder according to e xp-xdAnd calculating the displacement deviation.
The step (6) of updating the adaptive adjustable parameters specifically comprises the following steps:
adaptive adjustable parameter MyAccording to the formulaPerforming updating when updating value My>MymaxWhen M is in contact withy=Mymax(ii) a When updating value My<MyminWhen M is in contact withy=Mymin;
Adaptive adjustable parameter ByAccording to the formulaPerforming updating when updating value By>BymaxWhen, By=Bymax(ii) a When updating value By<ByminWhen, By=Bymin;
Adaptive adjustable parameter CyAccording to the formulaPerforming updating when updating value Cy>CymaxWhen, Cy=Cymax(ii) a When updating value Cy<CyminWhen, Cy=Cymin;
Adaptive tunable parameter DyAccording to the formulaUpdating is carried out when the value D is updatedy>DymaxWhen D isy=Dymax(ii) a When updating value Dy<DyminWhen D isy=Dymin;
Adaptive adjustable parameter dyAccording to the formulaPerforming updating when the updated value d isy>dymaxWhen d is greater thany=dymax(ii) a When updating value d y<dyminWhen d is greater thany=dymin;
Wherein, Mymin、MymaxAre each MyMinimum and maximum of, Bymin、BymaxAre respectively ByMinimum and maximum of, Cymin、CymaxAre respectively CyMinimum and maximum of, Dymin、DymaxAre respectively DyMinimum and maximum of dymin、dymaxAre respectively dyλ is the system gain.
Has the advantages that: the invention makes up the problems of dead zone, slow response speed and the like of the proportional valve by a multi-valve parallel coordination control method, saves the cost by a parallel structure of heterogeneous multi-valves while meeting the performances of high precision, fast response, large flow and the like, and solves the problems of self-adaptive adjustable parameters, external interference and the like by a self-adaptive robust algorithm.
Drawings
FIG. 1 is a schematic structural view of the present invention;
FIG. 2 is a schematic control flow diagram of the present invention;
FIG. 3 is a simulation diagram incorporating the present invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings.
As shown in fig. 1, the heterogeneous multi-valve parallel drive electro-hydraulic servo system mainly includes: plunger pump 6, three-phase motor 7, proportional valve P 13. Proportional valve P2… … proportional valve P m2, servo valve S m+19. Servo valve Sm+2… … Servo valve S n10, a check valve 8, a hydraulic cylinder 1, an overflow valve 4, a displacement sensor 12, a controller 11 and an oil filter 5. The three-phase motor 7 is connected with the plunger pump 6, an oil inlet of the plunger pump 6 is connected with the oil tank, the three-phase motor rotates to drive the plunger pump to work, and the plunger pump starts to supply oil to the hydraulic system; the output hydraulic oil flows to the one-way valve through the oil outlet of the plunger pump, the hydraulic oil flows to the oil filter through the one-way valve, and then the hydraulic oil flows to each of the hydraulic oil filters through the high-pressure hose The oil inlet of the servo valve and the oil inlet of each proportional valve. The overflow valve is arranged on the main oil return pipeline to ensure the pipeline pressure, and the hydraulic oil is connected with the high-pressure hose through the oil return ports of each servo valve and each proportional valve and flows to the oil tank. The hydraulic cylinder is connected with the oil outlet of each servo valve and the oil outlet of each proportional valve, and a piston rod of the hydraulic cylinder is connected with the displacement sensor; the signal output end of the displacement sensor 12 is connected with the input end of the controller 11, and n output ends of the controller 11 are respectively connected with the proportional valve P1……PmControl signal input and servo valve Sm+1……SnThe control signal input ends are connected.
The control method of the invention specifically comprises the following steps:
(1) the controller calculates and obtains the target displacement x of the current hydraulic cylinder according to the working time T of the systemd,xdF (t), and for xdFirst derivative ofSecond derivative ofAnd third derivativeThe displacement sensor R collects the actual displacement x at the current momentpAccording to e ═ xp-xdObtaining the displacement deviation e and calculating the first derivative of eSecond derivative ofThird derivative
(2) And calculating the total flow for driving the hydraulic cylinder to move according to the obtained target displacement, the displacement deviation and the derivative, wherein the calculation formula is as follows:
wherein d isy、My、By、DyAnd CyAll the parameters are self-adaptive adjustable parameters obtained by a hydraulic system through a mathematical model;
(3) Taking the total flow of the hydraulic cylinder driven to move in the step (2) as an initial residual total flow Qyi(T)=Qy(T);
(4) And sequentially distributing the residual total flow to the flow of each proportional valve according to the working priority of each proportional valve, and obtaining the control voltage of the proportional valve in the current control period according to the distributed flow, wherein the control voltage is as follows:
when Q isyi(T)>fi(Upi(T-t)+ΔUpi) While, the proportional valve PiIs set to Upi(T)=Upi(T-t)+ΔUpi;
When Q isyi(T)<fi(Upi(T-t)-ΔUpi) While, the proportional valve PiIs set to Upi(T)=Upi(T-t)-ΔUpi;
When f isi(Upi(T-t)-ΔUpi)≤Qyi(T)≤fi(Upi(T-t)+ΔUpi) When is, Qyi(T) > 0 then the proportional valve PiIs set toQyi(T) < 0, the control voltage is set to
Wherein the content of the first and second substances,indicating the maximum increment of the control voltage, U, per control cyclepimaxIndicating the proportional valve PiMaximum output voltage of, TpiIndicating the proportional valve PiResponse time of spool, DiIndicating the proportional valve PiDead zone of, KpiIndicating the proportional valve PiT denotes a control period, fi(Upi(T-t)+ΔUpi) Indicating the maximum flow f of the proportional valve output of the current control cyclei(Upi(T-t)-ΔUpi) Indicating the minimum flow, U, of the proportional valve output for the current control cyclepi(T-T) represents the voltage output by the proportional valve for the last control cycle;
(5) the residual flow after the flow of each proportional valve is distributed sequentially distributes the flow of each servo valve according to the working priority of the servo valve, and the control voltage of the servo valve in the current control period is obtained according to the distributed flow, which is specifically as follows:
When g isi(Usi(T-t)-ΔUsi)≤Qyi(T)≤gi(Usi(T-t)+ΔUsi) While servo valve SiIs set to Usi(T)=Usi(T-1)+ΔUsi;
When Q isyi(T)<gi(Usi(T-t)-ΔUsi) Time, servo valve SiIs set to Usi(T)=Usi(T-1)-ΔUsi;
Wherein S isiIncrement of voltage value ofUsimaxIs a servo valve SiMaximum output voltage of, TsiServo valve SiValve element response time gi(Usi(T-t)+ΔUsi) Representing the maximum value of the flow that can be output by the servo valve in the current control period, gi(Usi(T-t)-ΔUsi) Indicating the possible output flow of the servovalve during the current control cycleMinimum value, Usi(T-T) represents the output voltage of the servo valve in the last control period;
(6) working time T < Tmax0Then, the next control period is controlled, the self-adaptive adjustable parameters are updated, and then the steps (1) - (5) are repeated until T is more than or equal to Tmax0And the system stops control, and the updating of the self-adaptive adjustable parameters specifically comprises the following steps:
adaptive adjustable parameter MyAccording to the formulaPerforming updating when updating value My>MymaxWhen M is in contact withy=Mymax(ii) a When updating value My<MyminWhen M is in contact withy=Mymin;
Adaptive adjustable parameter ByAccording to the formulaPerforming updating when updating value By>BymaxWhen, By=Bymax(ii) a When updating value By<ByminWhen, By=Bymin;
Adaptive adjustable parameter CyAccording to the formulaPerforming updating when updating value Cy>CymaxWhen, Cy=Cymax(ii) a When updating value Cy<CyminWhen, Cy=Cymin;
Adaptive tunable parameter DyAccording to the formulaUpdating is carried out when the value D is updatedy>DymaxWhen D isy=Dymax(ii) a When updating value D y<DyminWhen, Dy=Dymin;
Adaptive adjustable parameter dyAccording to the formulaPerforming updating when the updated value d isy>dymaxWhen d is greater thany=dymax(ii) a When updating value dy<dyminWhen d is greater thany=dymin;
Wherein M isymin、MymaxAre respectively MyMinimum and maximum of, Bymin、BymaxAre respectively ByMinimum and maximum of, Cymin、CymaxAre respectively CyMinimum and maximum of, Dymin、DymaxAre respectively DyMinimum and maximum of dymin、dymaxAre respectively dyλ is the system gain.
When carrying out simulation test aiming at the system:
(1) numbering the proportional valves according to the response speeds of the proportional valves, wherein the proportional valve with the slowest response speed is numbered as P1The proportional valve number of the response time is P2,., the proportional valve with the fastest response is numbered Pm. Numbering the servo valves according to the response speeds of the servo valves, wherein the servo valve with the slowest response speed is numbered Sm+1The servo valve number with the second slowest response is Sm+2,., the servo valve with the fastest response is numbered Sn. The priority of operation of the proportional valve and the servo valve is thus P1>P2>...>Pm>Sm+1>Sm+2>...>SnThe control period t is 1 ms; working time T; total working time Tmax(ii) a Total flow Q of the systemy(T), proportional valve PiControl voltage U ofpi(T), output flow rate Qpi(T), wherein i represents the serial number of the valve, i is more than or equal to 1 and less than or equal to m; servo valve SiControl voltage U ofsi(T), output flow rate Qsi(T), wherein i represents the serial number of the valve, and m +1 is not less than i not more than n; target displacement x of hydraulic cylinder H d,xdF (T) is a function that varies with the operating time T. Each control cycle of the system calculates the current time according to the working time TTarget displacement xd(ii) a Actual trajectory x of hydraulic cylinder HpAnd each control cycle of the system can carry out actual displacement x through the displacement sensorpSampling is carried out; the target displacement x is obtained in each control cycle of the systemdAnd the actual displacement xpTaking the difference to obtain the displacement deviation, i.e. e ═ xp-xdPresetting a system adaptive adjustable parameter My,Mymin、MymaxAre respectively MyMinimum and maximum, system adaptive adjustable parameter By,Bymin、BymaxAre respectively ByMinimum and maximum, system adaptive adjustable parameter Cy,Cymin、CymaxAre respectively CyMinimum and maximum, system adaptive adjustable parameter Dy,Dymin、DymaxAre respectively DyMinimum and maximum values of; system adaptive adjustable parameter dy,dymin、dymaxAre respectively dyMinimum and maximum values of; the system gain is lambda;
the proportional valve P being dependent on the physical characteristics of the proportional valveiOutput flow rate Q ofpi(T) and a control voltage Upi(T) formula:
formula I middle KpiIndicating the proportional valve PiGain of (D)iIndicating the proportional valve PiWherein i is more than or equal to 1 and less than or equal to m.
Setting proportional valve PiHas a maximum output voltage of UpimaxProportional valve PiValve core response time of TpiProportional valve PiHas a voltage value increment of
Defining the servo valve S according to the physical characteristics of the servo valve iOutput flow rate Q ofsi(T) and a control voltage Usi(T) formula:
Qsi(T)=gi(Ui(T))=KsiUsi(T) ②
formula IIsiIndicating a servo valve SiWherein m +1 is not less than i not more than n.
Servo valve SiHas a maximum output voltage of UsimaxA servo valve SiValve core response time of Tsi,SiIncrement of voltage value of
(2) Initializing the parameters, specifically:
working time T is 0 ms; total working time Tmax300 ms; control voltage U of proportional valvepi(T) ═ 0V, where i ═ 1, 2, 3, …, m; control voltage U of servo valvesi(T) ═ 0V, where i ═ m +1, m +2, m +3, …, n; my0=4.5×10-7,Mymin=1×10-7、Mymax=10×10-7;By0=8.5×10-5,Bymin=1×10-5、Bymax=9×10-5;Cy0=0.36,Cymin=0.1、Cymax=0.6;Dy0=5.3×10-7,Dymin=1×10-7、Dymax=10×10-7;dy0=0,dymin=-10×10-7、dymax=10×10-7;λ0110; initialization xdAnd the function F (T) is a slope curve with 20 slope and 1mm amplitude.
(3) The system starts/continues to work, and the working time T is T + 1. System according to function xdF (t) calculating the current target displacement xdAnd to xdFirst derivative ofSecond derivative ofThird derivativeMeanwhile, the displacement sensor R collects the actual displacement x at the current momentpAnd sends it to the motion control card C; the system calculates the displacement deviation e and calculates the first derivative thereofSecond derivative ofThird derivative
(5) The system is used for obtaining the total flow Q in the step (4)y(T) carrying out flow distribution.
Let Qyi(T) is the residual flow, let Qyi(T)=Qy(T), i is 1, and the process proceeds to step (5.1).
(5.1) the system distributes flow to each proportional valve according to the operating priority of the proportional valve:
(5.1.1) when Qyi(T)>fi(Upi(T-t)+ΔUpi) While, the proportional valve PiIs set to Upi(T)=Upi(T-t)+ΔUpi。
(5.1.2) when Q isyi(T)<fi(Upi(T-t)-ΔUpi) While, the proportional valve PiIs set to Upi(T)=Upi(T-t)-ΔUpi。
(5.1.2) cases of dividing (5.1.1) and (5.1.2), when Q isyi(T) > 0 proportional valve PiIs set toWhen Q isyi(T) < 0 time controlA braking voltage is set to
(5.1.4) the flow is then further dispensed by the next proportional valve, i.e. i + 1. The system is based on formula Qyi(T)=Qy(i-1)(T)-f(i-1)(Up(i-1)(T)) calculating the residual flow rate and returning to step (5.1.1). Until i > m, proceed to step (5.2).
(5.2) the system distributes the residual flow to each servo valve according to the working priority of the servo valve:
(5.2.1) when Qyi(T)>gi(Usi(T-t)+ΔUsi) Time, servo valve SiIs set to Usi(T)=Usi(T-1)+ΔUsi;
(5.2.2) when Q isyi(T)<gi(Usi(T-t)-ΔUsi) Time, servo valve SiIs set to Usi(T)=Usi(T-1)-ΔUsi;
(5.2.4) then the next servo valve continues to dispense flow, i.e., i +1, the system follows equation Qyi(T)=Qy(i-1)(T)-f(i-1)(Up(i-1)(T)) calculating the residual flow rate, returning to step (5.2.1) until i>When n, go to step (6).
(6) The system updates the adaptive adjustable parameters of the next control period.
(7) And (4) returning to the step (3) if the working time T is less than 300ms, and automatically stopping control and setting the control signal output of all valves to be 0 if T is more than or equal to 300 ms.
The simulation result is shown in fig. 3, and it can be seen from fig. 3 that the response speed and the tracking accuracy of the tracking curve of the control method of the invention are obviously improved compared with the existing single-valve PID control method.
Claims (4)
1. The control method of the heterogeneous multi-valve parallel driving electro-hydraulic servo system is characterized in that the heterogeneous multi-valve parallel driving electro-hydraulic servo system comprises a plunger pump, an oil inlet of the plunger pump is connected with an oil tank, an oil outlet of the plunger pump is communicated with each parallel servo valve and each parallel proportional valve through a one-way valve and a branch, oil return ports of each servo valve and each proportional valve are communicated with the oil tank through a pipeline, oil outlets of each servo valve and each proportional valve are communicated with a hydraulic cylinder through pipelines, a piston rod of the hydraulic cylinder is in signal connection with a displacement sensor, the displacement sensor is in signal connection with an input end of a controller, and an output end of the controller is in signal connection with each proportional valve and each servo valve;
the control method of the system comprises the following steps:
firstly, the controller calculates and obtains the target displacement x of the current hydraulic cylinder according to the working time T of the systemdAnd to xdFirst derivative of the orderSecond derivative ofAnd third derivativeThe displacement sensor R collects the actual displacement x at the current moment pComparing the actual displacement xpAnd a target displacement xdObtaining the displacement deviation e and calculating the first derivative of eSecond derivative ofThird derivative
II, according toCalculating the obtained target displacement, the displacement deviation and the derivative to obtain the total flow Q for driving the hydraulic cylinder to movey(T), the calculation formula is as follows:
wherein d isy、My、By、DyAnd CyAll the parameters are self-adaptive adjustable parameters obtained by a hydraulic system through a mathematical model;
thirdly, the total flow obtained in the step two and used for driving the hydraulic cylinder to move is used as the initial residual total flow, and the initial residual total flow Qyi(T)=Qy(T);
Fourthly, sequentially distributing the residual total flow to the flow of each proportional valve according to the working priority of each proportional valve, and obtaining the control voltage of the proportional valve in the current control period according to the distributed flow, wherein the specific steps are as follows:
when Q isyi(T)>fi(Upi(T-t)+ΔUpi) While, the proportional valve PiIs set to Upi(T)=Upi(T-t)+ΔUpi;
When Q isyi(T)<fi(Upi(T-t)-ΔUpi) While, the proportional valve PiIs set to Upi(T)=Upi(T-t)-ΔUpi;
When f isi(Upi(T-t)-ΔUpi)≤Qyi(T)≤fi(Upi(T-t)+ΔUpi) When is, Qyi(T) > 0 then the proportional valve PiIs set toQyi(T) < 0, the control voltage is set to
Wherein the content of the first and second substances,indicating the maximum increment of the control voltage, U, per control cyclepimaxIndicating the proportional valve PiMaximum output voltage of, TpiIndicating the proportional valve PiResponse time of spool, DiIndicating the proportional valve PiDead zone of, KpiIndicating the proportional valve PiT denotes a control period, f i(Upi(T-t)+ΔUpi) Representing the maximum flow f of the proportional valve output of the current control cyclei(Upi(T-t)-ΔUpi) Indicating the minimum flow, U, of the proportional valve output for the current control cyclepi(T-T) represents the voltage output by the proportional valve for the last control cycle;
fifthly, the residual flow after the flow of each proportional valve is distributed sequentially distributes the flow of each servo valve according to the working priority of the servo valve, and the control voltage of the servo valve in the current control period is obtained according to the distributed flow, which is as follows:
when g isi(Usi(T-t)-ΔUsi)≤Qyi(T)≤gi(Usi(T-t)+ΔUsi) Time, servo valve SiIs set to Usi(T)=Usi(T-t)+ΔUsi;
When Q isyi(T)<gi(Usi(T-t)-ΔUsi) Time, servo valve SiIs set to Usi(T)=Usi(T-t)-ΔUsi;
Wherein S isiIncrement of voltage value ofUsimaxIs a servo valve SiMaximum output voltage of,TsiServo valve SiValve element response time, gi(Usi(T-t)+ΔUsi) Representing the maximum value of the flow that can be output by the servo valve in the current control period, gi(Usi(T-t)-ΔUsi) Represents the minimum value, U, of the flow that can be output by the servo valve in the current control periodsi(T-T) represents the output voltage of the servo valve in the last control period;
sixthly, the working time T is less than Tmax0And then, the next control period is controlled, the self-adaptive adjustable parameters are updated, and the steps from one to five are repeated until T is more than or equal to Tmax0And stopping control of the system, wherein the updating of the self-adaptive adjustable parameters specifically comprises the following steps:
Adaptive adjustable parameter MyAccording to the formulaPerforming update when the update value My>MymaxWhen M is in contact withy=Mymax(ii) a When updating value My<MyminWhen M is in contact withy=Mymin;
Adaptive adjustable parameter ByAccording to the formulaPerforming updating when updating value By>BymaxWhen, By=Bymax(ii) a When updating value By<ByminWhen, By=Bymin;
Adaptive adjustable parameter CyAccording to the formulaPerforming updating when updating value Cy>CymaxWhen, Cy=Cymax(ii) a When updating value Cy<CyminWhen, Cy=Cymin;
Adaptive tunable parameter DyAccording to the formulaUpdating is carried out when the value D is updatedy>DymaxWhen D isy=Dymax(ii) a When updating value Dy<DyminWhen D isy=Dymin;
Adaptive adjustable parameter dyAccording to the formulaPerforming updating when the updated value d isy>dymaxWhen d is greater thany=dymax(ii) a When updating value dy<dyminWhen d is greater thany=dymin;
Wherein M isymin、MymaxAre respectively MyMinimum and maximum of, Bymin、BymaxAre respectively ByMinimum and maximum of, Cymin、CymaxAre respectively CyMinimum and maximum of, Dymin、DymaxAre respectively DyMinimum and maximum of dymin、dymaxAre respectively dyλ is the system gain.
2. The control method of the heterogeneous multi-valve parallel drive electro-hydraulic servo system according to claim 1, wherein the plunger pump is electrically connected with a three-phase motor, and the three-phase motor controls the plunger pump to work.
3. The control method of the heterogeneous multi-valve parallel drive electro-hydraulic servo system according to claim 1, wherein the one-way valve is communicated with an oil tank through an oil return branch, and an overflow valve and an oil filter are arranged on the oil return branch.
4. The control method for the heterogeneous multi-valve parallel drive electro-hydraulic servo system according to claim 1, wherein in the first step, the control method is based on a preset function xdF (T) calculating the target displacement of the hydraulic cylinder according to e xp-xdAnd calculating the displacement deviation.
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