FI118608B - Control system and method for controlling an actuator and for optimizing control by means of parallel connected valve series - Google Patents

Abstract

A control system and a method for controlling a pressure medium circuit which is arranged for the rate control and/or the position control of an actuator driven by pressurized medium. The pressure medium circuit comprises a first connection (1) between an input port (P) and a first working port (A), a second connection (2) between an output port (T) and a second working port (B), and valve means (102) for guiding the volume flow of said connections (1, 2), which valve means comprise at least a first set (103) and at least a second set (104) of controllable valves (V1-V4), coupled in parallel, which can be opened and closed, wherein the volume flow of the set (103, 104) is determined as the sum of the capacities of the valves controlled to be opened at a time, and wherein the first set (103) is coupled in series with the first connection (1) and the second set (104) is coupled in series with the second connection (2), and control means (105, 109) for controlling said valve means (102). The method comprises the steps of determining at least some of the discrete rates achieved by said actuator, when valves (V1-V4) of the sets (103, 104) are opened and closed in various combinations, selecting from these combinations at least one which, according to a set optimization criterion, realizes the desired rate at each moment of time, and guiding the valves (V1-V4) of said sets to positions complying with the selected combination.

Description

118608

Control system and method for controlling the actuator and optimizing the control by means of parallel valve sets

The invention relates to a control system 5 according to the preamble of claim 1 for speed control and / or position control of a pressure medium actuator. The invention also relates to a method according to the preamble of claim 11 for speed control and / or position control of a pressure medium actuator.

10

As is known in hydraulic technology, energy is transmitted by means of a pressure medium, whereby the pressurized volume flow produced by the pump means is controlled by means of valves and utilized in actuators such as cylinders and motors to provide linear motion, force, 15 torque or rotational motion. Known pressure media include hydraulic oil, compressed air and water or aqueous hydraulic fluids (HFA, HFB, HFC, HFD).

Known proportions are used to control cylinders and engines: ·. 20 female control valves, an example of which is disclosed in the patent application. in US 5,785,087. The valve shown is a slide type valve in which the position of the slide is controlled by a proportional magnet to choke the pressure medium while controlling the volume flow and direction 'of the flow. The valve is controlled by an external electrical setting signal proportional to the desired volume flow. Valve • ·: Provides infinitely variable volume flow control.

It is an object of the present invention to provide an alternative way of controlling the flow of a volume, particularly in connection with actuators, which also enables energy savings. The invention provides considerable advantages over conventional proportional control and »·. eliminating their problems. The control system of the invention is set forth in claim 1. The method of the invention is' set forth in claim 11.

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118608 2

The control system is particularly suited for actuator speed control, but it can also be applied to position control when continuously monitoring the desired or set, time-dependent position.

Systems for stepwise volume flow control are known, implemented by means of separate simple valves. In the system, control of different volume flow rates is implemented with valves having only an open position and a closed position (so-called on / off valve, 2/2 valve). The 4/3-valve (4-connection and 3-position), implemented with separate valves, is even more versatile than the proportional 4/3 valve with some features.

Highly affordable, readily available valves can be used as on / off components, using simple structures that do not have the problem of sealing or volume flow wear. On the other hand, these components can be afforded even short lifetimes due to their low cost and ease of installation. Another benefit is the durability of their impurities.

20

An example of an on / off system to be connected to the pressure or return side of the cylinder is disclosed in US 2,999,482. Patent- * · · I ·,. US 5,313,871, in turn, discloses the control of an on / off system on the pressure side * .1 / to move the cylinder to the desired volume. US 4,590,966, in turn, discloses a version of an on / off system, i.e., a kind of digital valve block · * "· 1 that is coupled to the pressure and return side of the valve. A similar type of block is also disclosed in US 4,518,011.

*: ··: 30 The number of control steps can be reduced and increased as necessary and · ***. depending on the application, allowing the same valve system • • f ·. more effectively applied in different situations. Low need for steering stairs ·· ♦ * ;;; also reduces the number of on / off valves, which reduces costs * ·: ·. The operation of the valves, especially the change of control, always involves: 1 · 1.- 35 also the response time which the slider valve depends on how long the slider has to travel. The on / off valves operate simultaneously when required, with the operating delay being substantially constant with all changes in the volume flow control 118608 3, since the valves move only between open and closed positions.

An advantage over slip-controlled valves is also achieved by the fact that the flows of two simultaneous connections of the 5 valve systems can be controlled separately. Em. At the valve, these different pressurized fluid flows are simultaneously controlled by different guide edges of the same slide. Control independence in the on / off system allows for the reduction of unnecessary pressure losses in the flow and thus also significant energy savings without affecting the controllability. Functional independence, on the other hand, also increases the way the 4/3 valve is operated and controlled.

In the following description, the invention will be illustrated with reference to the accompanying drawings, in which Figure 1 is a diagrammatic representation of a prior art proportional valve, Figure 2 is a diagrammatic representation of a valve system according to the invention for one valve assembly. Figure 3 illustrates a preferred embodiment of the invention; Fig. 4a-4d illustrate various switching possibilities of the valve system of Fig. 3 ««:: · «· The diagram shows a diagram of an on / off valve system. : ··· 30 circuits for cylinder control, · «« • · Figure 6 shows the cylinder speeds of the system of Figure 5 with various combinations of vent • · · *: / bricks, *: • · · 35 Figure 7 shows the speeds of Figure 6 set and • · 118608 4 Figure 8 shows the pressure variations of the system of Figure 5 on the pressure side with various combinations of valve openings.

Figure 1 shows the characteristic curve of a prior art pro-proportional directional valve in which the throughput capacity of the valve volume flow Q is linearly dependent on the control signal V. The slope of the characteristic curve further depends on the pressure difference across the valve, i.e. the magnitude of pressure drop. In the example shown, the voltage signal V10 is used as the control signal, but the current signal / can also be used. The selected level of the control signal V acts as a setpoint VSET, whereby the maximum control VMAX corresponds to the maximum flow rate Qmax, and the other levels curve the flow rate QSet, respectively. whereby the control is zero and no volume flow is obtained. The characteristic curve usually continues as a mirror image to the negative side 15, whereby the VSet can also be negative, whereby the direction of flow and the position of the valve are also changed.

In the directional proportional valve, the proportional magnet acts on the control slide, which is usually centered by springs. Proportional magnet, in turn, is usually a direct current magnet (DC), which outputs an anchor force or Motion distance that is proportional to the level of electrical control signal input.

A: The valve control means is formed on a circuit board that is electrically connected to the valve. The circuit board, in turn, can be connected to any control system 25 for controlling the valve and the wider hardware. Thus, a certain level of control signal from the control system can be used to control the volume flow through the valve and the actuator further connected to the valve ·· ♦ · * ... · *. The flow rate and direction of movement of the cylinder actuator can be further controlled by means of a pressurized volume flow. Example:: ··: 30 chips with a variable setting signal of -10 V to +10 V cylinder movement · ”*: direction (ie valve slide position) is determined by the sign and * ·· \ with a limit of 0 V, the valve is in the closed position and the cylinder is stopped. The setting signal may also be, for example, 0 V - 20 V * ·; ·: a signal with a limit of 10 V. Figure 1 also shows the drawing symbol of the directional proportional valve and the connections therein.

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118608 5

Fig. 2 shows a stepwise characteristic of one set of valves of an on / off valve system, whereby, as the control signal V changes, the volume flow Q changes only stepwise. The volumetric flow QSet of the valve system changes incrementally when the set signal VSet 5 exceeds or falls below the set limits. Of course, the adjustable volume flow rate of the pressure medium is the better the smaller the step size dQ relative to the maximum flow rate QMAX, i.e. the more valves there are.

Referring to Figure 3, a preferred actuator control valve system 100 of the invention comprises at least P, T, A, and B connections. The inlet connection P is arranged to connect a pressure line to the system, usually to receive a volume flow of pressurized pressure medium from the pump. An outlet T is provided for connecting a return line 15 to a system which is a tank line or a line lower than the pressure line. The first working port A is arranged to operate the device, such as the piston side of the cylinder in the system. The second working port B is arranged on an actuator such as a cylinder the piston rod side of a system. Volume current is supplied to the actuator through one of the 20 work connections, and volume flow is received from the actuator through the other.

• · · * ·,. For the various directions of movement of the actuator, the system 100 comprises electrically controlled coupling means 101 arranged to provide at least a first connection 1 (between the input P and the first * ···! Work interface A) and simultaneously a second connection 2- ****** * (between output terminal T and second work interface B). The switching means 101 are also arranged to establish at least a third connection 3 (between the input P and a second work interface B) and at least ·: ··: 30 simultaneously to establish a fourth connection 4 (between the output · ** '; T and the first work connection A) ). The various switching options M · \ are also illustrated in Figure 4c with the aid of drawing symbols.

* · ♦ ·· ··· * ·; · ** The desired switching options can be realized, for example: * ♦ *: 35 electrically operated 4/2-valves, which are slider-type on / off valves V, · * ·.: marked in Figure 3. Alternatively, connections can be made using two parallel electrically controlled 3/2 valves. Adding slide positioning options to the slide 118608 6 can increase the overall system switching options. Indeed, the coupling means 101 may vary widely and may also be connected separately to the system 100. In this case, the system 100 comprises in its basic form only the first connection 1 between the input terminal P and 5, the first working interface A, and the separate second connection 2 between the output terminal T and the second working interface B. The connection means 101 are then connected to the working terminals A and B, for example. , if the motor rotates in only one direction.

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Referring further to Figure 3, the pressure medium passing through the connections 1-4 is further controlled by valve means 102. Valve means 102 comprises two sets of valves 103 and 104. Each set comprises a plurality of electrically controlled, parallel on / off valves having a mutual pressure medium throughput capacity arranged in a step-by-step sequence. The minimum volume flow rate of the pressure medium for the entire valve system 100 is determined by the smallest valve capacity in the series and the maximum capacity based on the total capacity of all valves in the series. Series 103 (at interface P) adjusts the flow rates for connections 1 and 3, and series 104 (at interface T) controls the flow rates at connections 2 and 4. However, only connections 1 and 2 or connections 3 and 4 can be used simultaneously. Valve sets 103 and 104. may also be assembled in other ways to produce the desired stepped characteristic, whereby a plurality of valves of the same size may be present. Valve sets may also differ. The valve system of the exemplary system, '···', in turn, is easy to mathematically represent and the number of valves J '"is as small as possible in the number of steps. The reachable control curve shown in Figure 7 of the exemplary system also provides precise, almost linear control. 30 at high speeds.

The series 103 and 104 in the illustrated embodiment of the invention are implemented with four electrically controlled 2/2 valves (solenoid controlled on / off valve) as shown in Figure 3. The mutual flow capacities of the V1 to V4 pressurized fluid volumes: * · *: 35 are arranged in accordance with Table 1.

: * ·. · At least two valves are required for adjustment.

• · 118608 7

As shown in Figure 3, in a preferred embodiment of the invention, each set has four (denoted by N) valves 15 to provide a control stage. In this case, the throughput of the first valve (V1) is 0.5 l / min (denoted Q) and the successive valves of successive 5 are 1.0 l / min (V2), 2.0 l / min (V3) and 4 l / min. (V4), i.e. according to the computational rule 2 ° "1> · 0, where the variable n is the sequence number of the valve. Thus step size dQ is given by Q, the maximum number of steps is 15 (i.e. according to counting rule 2 * '1) The system has a minimum-10 capacity of Q and a maximum capacity of 7.5 l / min (i.e. according to the calculation rule Q ^ -1) The calculation rules can be used to calculate the required number of valves N when the desired maximum capacity and the desired dQ are known. steps and six valves with 63. 15 Typically, the number of valves varies between 3-7.

Qtot Valve V1 Valve V2 Valve V3 Valve V4 [l / minl Qw = 0.51 / min Qi / g = 1.01 / min Qv3 = 2.0l / min Qw = 4.0l / min 0_0_0__0_0_ 0.5_J_0_0_0_ 1.0_0_J__0_0_ 1.5 _J_J_0_0_ 2J) _0_0_J_0_: V: '2J5_J_0_J_0_ r': 3J) _0__J_o_ 3.5 1110 • * - 1 mi mu, m · - i 11-1.11 i ~ '' '' 4.0 (4,5) 0 (1). _0__0_J_ 4.5 (4.5) 1 (1) _0__0_J_ ....: 5.0 (5.5) 0 (1) 1__0_J_ 5.5 (5.5) 1 (1) 1__0_J_ 6.0 (6 , 5) 0 (1) _0__J_J_ .SV 6.5 (6.5) 1 (1) _0__J_J_ O 7.0 (7.5) 0 (1) 1__J_J_: * ·;. · 17.5 (7.5) ) 11 (1) UM M_

Table 1 • * ♦ • · 118608 8

In order to control the throughput capacity of the valve system to the desired level Qset, the valves whose total capacity QTot corresponds to the desired level and the setting signal VSet are opened in Table 1 so that the levels occur at 0.5 l / min and each line is marked with ) or closed (0). To close the entire connection, all valves are closed (0). In some situations, the operation of the valve system can be improved by keeping the smallest valve (V1) open continuously at high flow rates (Qset> Qmax / 2). The number of steps is then reduced, but may still be sufficient for control. This situation is shown in Table 1 in brackets.

Figure 4a illustrates, by means of drawing symbols, the connection possibilities of the series 103 and Figure 4b illustrates the connection possibilities of the series 104. The connection to terminal A or B depends on the position of the coupling means 101. The kits shown are the same in the 15 embodiments shown, but may vary as desired. When all valves V1 - V4 of each series are closed, connection 1 - 4 can be closed and even one of the valves V1 - V4 in the series is opened, whereby the volume flow rate through the valve system depends on the valves opened at any given time. The adjustability of the volume-20 current Q in this connection is indicated by a dash. When viewed as a whole, the connection possibilities of the valve system 100 shown in Figure 4d show that. in addition to conventional 4/3-valve connections, it is possible to achieve connections where one connection in turn is closed. This is mah - *: *. ** for $ 25, as the kits 103 and 104 can be controlled separately if needed.

Separation also means that pressure losses can also be separately controlled at the same time.

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Referring further to Figure 3, the valve system 100 further comprises *: · *: 30 electrical control means 105 for controlling the valve means 103, 104 by means of the control signals 106. According to a preferred embodiment of the invention, the control means 105 are formed by a programmable *;:! with a microcontroller connected via control wires to the valves V of series 103, 104 and to the valve V of the means 101 Controller 105 implements: ** \ · 35 control by means of a control algorithm stored in its memory means: * ·. The control algorithm • · is designed to provide the desired control. For control 118608 9, controller 105 receives externally, if necessary, one or more set signals 107 and 108, by means of which the valves of the series are opened and closed or the valves of the means 101 are moved as needed. The controller 105 also automatically controls, if necessary, how quickly the volume flow of the connections of the valve system 100 is changed, i.e., the acceleration and deceleration ramps of the actuator. It also provides kits for the flow asymmetry of the transmission of a given situation, e.g. reverse side a series of transmission 104 is controlled to a higher level than the pressure in the transmission-side set 103, the 10-painehäviöi reduce. Alternatively, to avoid cavitation, the throughput of the series 103 is controlled higher than that of the series 104. In addition, based on the control signal 107, 108 supplied to the controller 105, such as a setting signal (e.g., -10V to +10V or current signal) level and the direction of motion of the actuator 15, after which valves and means 101 of the series 103 and 104 are controlled. The control of the valves V, V1 to V4 may be effected, for example, by the relays of the control means 105 through which the operating voltage is supplied to the valves.

20 Em. parameters related to calculating the control algorithm of controller 105, such as deceleration ramp, acceleration ramp, asymmetry, size of control zero or dead zone, setting signal and throughput capacity **: ratio of ratio, valve combination at different throughput levels, sequence control * · · 4.V 4a to 4d are preferably supplied to controller 105, for example by means of a programming device or control system 109, such as computer hardware, which forms a higher level control system. At least some of the parameters can be set directly by means of control screws or control buttons attached to controller 105. It can even have a display and keyboard •: ··: 30 for manually entering parameter values. Said control system 109 can simultaneously control other valve systems or equipment to which the valve system 100 is associated. To set the valve system 100 in different modes, inter alia, for setting up various connections, the setpoint and parameters of the controller 105 can be input to the controller 105. 35, for example via bus 107 or 108, but in some embodiments also in analog form with the setting signal 107 • · or 108. Each parameter may also have its own signal line.

118608 10

Default values can also be used for the parameters, whereby the control is performed simply by a single setpoint (e.g., a voltage signal of -10V to +10V or a current signal) and the controller provides optimal control of the system 100 via the control algorithm. The setpoint can also be entered in manual control, for example by means of a joystick controlled by the user to achieve the desired speed. The desired speed is then, for example, slow or fast, depending on the position of the joystick.

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In one embodiment of the invention, the valve system 100 consists of separate valves V and V1-V4, which are preferably mounted on a common bottom plate, which also has the necessary bores and ducts for forming the aforementioned connections. The System-15 forms a single, compact unit. Preferably, the base plate also includes some of the connections (P, T, A, B) of the valve system 100, for example for pipe mounting or mounting plate mounting. It is clear that the necessary connections can also be made by means of pipes and hoses by connecting the valves. It will be appreciated that other connections may be provided to the valve system 20 to provide special connections in addition to the connections 1-4 shown. In this case, in particular, the connection possibilities of the valve V of the coupling means 101 are increased. Valve V. ·. For example, it could be used to close connections A and B and establish a connection between connections P and T via the series 103 and 104 shown.

• * * 25 * · *** \ Calculation of Valve Controls for Exemplary System Valve Controls Figure 5 illustrates a typical circuit for on / off valve control for cylinder 200. For the sake of simplicity, calculating - * "·: 30 bar is used as a tank pressure of 0 bar and valve 101 · *": pressure losses are assumed to be insignificant and valve flow rates Q are selected as 0.5 (V1), 1 (V2), 2 (V3) and 4 (V4) l / min for a differential pressure across the valve of 5 bar, alternatively the series may be, for example, 2, 4, 8 and 16 l / min The proportion of tank pressure and pressure drop can also be taken into account. Let's look at the following! * ·: Modeling the system using the following entries: 118608 11

Aa 1) of the cylinder of the piston-side area [m2]

Ab 1) of the cylinder piston rod-side area [m2]

1 KVP) on the pressure side valve of the smallest displacement of the valve flow coefficient [m 3 / (s-Pa05)]

Kvr 1) on the return side valve of the smallest valve flowrate coefficient [m 3 / (sPa0 · 5)] n P 1) the number of discharge valves nT r> Number return side valves AVP 2) The discharge valve in the opening (an integer of 0 - 2V;) avr 2) on the return side valve in the opening (integer 0 - 2fnr1)) γ Cylinder area ratio Aa / Ab z Auxiliary variables avPKVp / (avrKvt) v 3) Cylinder speed [m / s]

3 Pa) Pressure in the chamber on the piston side [Pa] p B 3) of the piston rod-side pressure chamber [Pa] ps 1), 2) Feeding pressure [Pa]

The volume flow Q p through the discharge valve set [m3 / s]

Flow rate Qt return side through a series of valves [m3 / s] F1), 2) Net force effective on the cylinder (external forces and frictions) • • · T · 1 1 <1 1. ···. As the piston 201 moves in the positive direction, the flow rates are: • · • · ·

5 (1): QP = avpKVPyJps -pA = v Aa and (2): QT = avTKwJp ^ = v-AB

With the power equation: (3) F = aaPa - abPb • a • · 9 * ·: · In the equilibrium state of the circuit (positive direction), the pressures and velocities are: • · · «··" · (4) e -I'Ps + r ' FlA, (5. _ r z2ps-z1FIAa WP1 z2 + y, .WP, - z2 + yl, and 2 {R \ v - avp ^ vp Ir-Ps ~ F "/ Ag 2 ab i z2 + f 118608 12 Männän In turn, 201 moves in a negative direction into volume flows, where: (8) Qt = αντKvr V ^ T = ~ vAa and (8) Qp = avpKVP4pS ~ Pb = ~ vAb

In the force equation: (9) F ~ AaPa ~ AbPb

At circuit equilibrium (negative direction), pressures and velocity 10 are: y2 / \ + y2F / AB .... γ3 · p, .z ~ 2F I Aa.

0 °) Pa = 7 py + f. en) pb = l ......? sz-2 + f Ja (12) v = _ ^ vl ^ s + F / ab

Ab VZ ~ 2 + Y 15 from the above formulas it is apparent that the equilibrium pressures will depend on the pressure side (P) and the return side (T) being opened, the feed pressure and 200 of the active cylinder power, making it possible to mark functions: v = v (AVP, AVT, ps, D) (13) pA = pA (avp, avT, ps, F) • · pB = pB (avp> avT, ps, F) Ö 20

The necessary calculation is performed by the control algorithms of the control means 105. ···. where the system parameters that are represented by the system (the characters '*' typed above in reference 1) are entered. The calculation is performed by various combinations of variable parameters (denoted by 2 above), resulting in 25 outputs (denoted by 3 above). After optimization and selection of the combination, the control means 105 control the valve means 102, i.e. the valves, to the desired position by means of the control signals ·: · 106.

• · * ·

If the desired setpoint changes, the procedure is repeated. The setpoint can be continuously changed, which is then followed by the control algorithm 30. The procedure of the control algorithm itself to obtain the desired setpoint is also shown below.

118608 13

The calculation of combinations may also be performed separately, within or outside the control system 109. The calculation is carried out, for example, by computer hardware, and the control means 105 store, for example, the values of speed calculated in the form of a table and the values of the aforementioned parameters 5 used for computing (pressures, opening combination, forces, etc.). The values in the table can be placed in an optimization algorithm to determine the order of preference of the opening combinations. The desired combination is selected for operation and the valves are moved to the corresponding position according to the table. The arrangement reduces 10 and speeds up the calculation of the control means 105. The control means 105 may also comprise an easy-to-use, ready-to-use assembly with the calculation of opening combinations, whereupon the actuator and valve assembly used are first fed to it. The control means 105 may then be supplied with a plurality of ready-made, alternative designs 15 of the pressure medium circuits 100 used, or may be defined, for example, by means of parameters or modeling. The control means 105 take care of the computation and storage of the required computation algorithms.

20 Sample System Speed Control * · t. ·. A: Let's look at action in a positive direction. The negative direction can be treated in the same way by taking it into account as well.

• · «in the formulas. If it is desired to control speed without feedback, the supply pressure ps and the force F acting on the cylinder 200 should be known or measured. According to the invention, the above formulas can be calculated: ··· * balance the pressures and the rate for all the possible P- and T-side on / off valve opening combinations. From these values, the best possible choice can be selected by using the desired criteria. Here, according to the invention, the desired penalty function J is used, which is, for example, a function of the equilibrium pressures and velocities, and possibly also of the pressure change, where: · · · · · * f7 (14) J = J (v, pA, pB ) * ·

Figure 6 shows the barrel 200 of Figure 5 the velocity v of the P-side of the valve set 103 on the T side and the valve set 104 of openings of different combined cycle 35 118 608 14 contamination, to give the on / off valves because of large number of separate, discontinuous or discrete values. By arranging the combinations in order based on the speed attainable by the actuator, a stair pattern according to Fig. 7 is obtained in which each stage corresponds to one of a particular combination. A particular advantage of the invention is that there are several different combinations corresponding to substantially the same speed, the pressure levels of which may be very different and from which the most suitable can be selected, as long as, for example, the velocity error is within the permitted limits. The pressure fluctuations on the piston side of the exemplary system are illustrated in Figure 8. For example, the smallest change in pressure relative to the prevailing pressure level is used as a selection criterion. Other criteria may be used to select the combinations to be used next.

15 In control mode where the P and T sides are controlled separately, the second set of valves is usually completely open. In this case, only the step shown in Figure 2 is used, whereby Vmax corresponds to the extreme combination of the T or P series of valves parallel to either the T or P axis.

The present invention is not limited to these steps, but all 20 steps are considered. Also, moving at the same speed level is possible with different combinations, because of equal columns. ; illustrate different combinations (and simultaneously different pressure levels) but • * ·, .V essentially the same speed. The control mode of the invention can proceed from column to column while optimizing control.

The selection of the opening combination to be used for control is a difficult task which is solved by the fine function J of the present invention. Based on this, the following * ··· *: switchable opening combination can be selected to provide the desired speed control of the cylinder · * ": 30. The following discussion applies to] .m analogously to hydraulic motors, the application of which will be apparent to those skilled in the art.

• I • · · •

f · *: In the first embodiment of the invention there is J in the fine function

For speed control 35, only the speed error is considered: 118608 15 (15) ./(ν) = Κ „''ν-ν |) χ, where νκ / is the desired cylinder speed. The variable X is the desired power, for example 2, and the factor K0 is the weight factor. In speed control 5, it is also necessary to know the force F acting on the cylinder. Next, equilibrium pressures pA, Pb and velocity v are calculated for all possible opening combinations. The value of the fine function J is then calculated from these different values (pA, pB, v). Thereafter, the opening combination of the valve series (e.g., 103 and 104) that best meets the criteria of the 10 Functions J is selected. In this case, the opening combination with the smallest function J is selected with the smallest rate error. It is clear that a maximum value can be set for the velocity error, so that any suitable opening combination with which the function J is smaller can be selected. The selection of a suitable opening combination may also be based on other criteria.

In another preferred embodiment of the invention, in addition to velocity control, cavitation is taken into account, thereby rejecting opening combinations in which the pressure pA and / or pB is 20 pmin closer to the zero pressure. Then the fine function J is, for example: ··· yi (16) j \ Ko · (| V v |) X. her: PA> ja 'Ps ^ p ^ * \ 0 1 her: pA <PmJai: pB <p ^ n ··· • · • · «··

The value of the finite function J is set to a very large number (or that: ***; 25 options can be ruled out) if the opening combination • · * threatens to cause cavitation, so this combination is clearly not among the choices in minimization.

In the third embodiment, the pressures pA and pB are set at ... T 30 the target pressures pA> ref and pB, mf from which they should not deviate further than desired. The amount of deviation depends on the coefficient of the fine function. : v, Target pressures affect eg. energy saving with pressure). *. should be kept as low as possible, however cavitation should be *: avoided. The aspiration to target pressure can be combined with the need for 118608 16 to keep the velocity approximately desired and represented by the formula (without the conditions for cavitation suppression, which can be added to the formula): (17) J = Κ0 · ψν'-ν |) χ + ΑΓ, (| ) r + Κ, · ψ>,. * -ps |) z, 5 where K * and K2 (weight factor) determine how aggressively the pressure is to be maintained. When the pressure level does not matter, the coefficient is zero.

10 The on / off valves operate stepwise and a variety of discrete steps are available for different combinations, so that high pressure level fluctuations in counterbalance to good speed control are not always acceptable. In a fourth embodiment of the invention, changes in pressure levels, i.e. pressure jumps, are reduced by adding a change in pressure level 15 to the penalty function J as follows: (18) JV (| Vv |) '+ *, ·] κ. | Ρλ-ρ «| Γ + Ks \ pB-ps" \ f \, where pA, ed and Pe, ed are the pressures selected in the previous calculation, i.e. the discrete step used by the 20 controls to move 'to the next to implement cylinder control and speed change. The fine function can be supplemented with e.g. optimization of target pressures: .v, where fluctuation occurs within a given pressure value.

• · «« · # ·: *: 25 In order to save energy, the maximum supply pressure ps should be kept: ***: as low as possible. This is achieved by requiring that the minimum pressure in the ··· system be relatively low and constant. Usually the minimum pressure is on the return side when the force is. anti. In this case, according to one example, it is sought to keep pB '. ** 30 desired (pe, re /) within the set limits (pB, nf - Pb) and pA may vary freely.

··· • · • *> ··: ·! ·. Example System Speed Controls Next, let's look at different ways to determine the speed required to select opening combinations vnf \ The simplest case is 118608 17 open control, where the desired speed is obtained directly from the control means 105, 109, or from a user, e.g. . The better the load force F and the feed pressure ps are, the smaller the velocity error is. Indeed, open steering provides accurate 5-speed control only if the load force is known precisely or measured. On the other hand, for example, manual control does not require very precise speed control.

In speed control, the force acting on the cylinder is not always known. More accurate speed control is achieved by measuring the actual speed and selecting valve combinations to minimize the speed error. If the target velocity v ^ f is greater than the measured velocity v, then an opening combination that produces a higher velocity must be selected. However, there is a problem with the load force F, the value of which may be poorly known. However, it has been discovered in the invention that it is essential for the closed control that the order of the opening combinations is independent of the load force, whereby in the formulas (4) - (6) and (10) - (12) a rough estimate of the load force can be used This allows the opening combinations to be used to be determined and selected in advance, for example with small variations in velocity v and / or to prevent cavitation. These combinations are set in order · · ·. * And if you want to increase the speed, for example, opening combinations are selected, · * ·· *. in this order, towards the higher speed, until the desired speed t *** j 25 is realized. The same principle applies when slowing down. At the beginning of the control, you can select, for example, every Fifth value and gradually refine the selection of * ··· * ', so that the next value is always selected.

If the force F is known in advance or can be estimated reliably, then a series of different opening combinations can be determined in advance. * ·, (Finite function J). For example, kits achieve good speed control (formula (15)) and optimum pressures (formula (16)) when the load - **: · * force F is positive, negative, or zero, each in its own series. Based on the load force estimate, it is possible to determine more precisely 35 and always select the most appropriate series to be used in open or closed control. In this case, the appropriate opening combination may be selected directly without progression in sequence, depending of course on the desired velocity profile. At the same time, for example, pressures can be optimized.

In closed speed control, the required vnf 'for selecting the opening combinations 5 is generated by a speed controller which has a speed error (vref - v) input and whose control algorithm tends to minimize the rate error. The function of the computation algorithm used is of the form v ^ '= fy (vref - v), where fv is some static or dynamic representation. The control accuracy can be further improved by using feed-forward-10, whereby the desired speed vnf is summed to the output of the speed controller: vnf = Vnf + fv (Vref - v). The advantage of this mode of adjustment is that the speed controller operates at small differences.

The desired speed may vary as a function of time so that, for example, the desired speed ramp vref (t) can be followed. The control means 105 may be arranged to continuously determine this desired speed. The desired velocity as a function of time vnf (t) can also be stored, for example, as a function or as a table and the control means reads that table. The desired rate value, constant or variable, may also be a control signal 107 and / or 108 generated by the same or separate control system 109.

• · · · · · · · · · · · · · · · · · · · 25 Controls of actuators often use movements in which the position, * "* changes according to a track or curve, such as position and velocity ramps. Based on system speed control, good position control can also be achieved, though the control provides "- **: discrete combinations. The system is particularly suitable for 30 position control when the actuator is constantly in motion, following the desired position.

At each point in time, the desired rate vref can be generated based on the desired xn1 (t) position path. The desired path xn1 (t) may also be stored as, for example, a function or a table read by control means 105. For feedback, the system further comprises means for determining the position of the actuator 118608 19, which in turn is measured relative to the desired position xnf.

In one embodiment of the invention, the required speed is determined based on the position reference xni (t) 5, for example based on the fact that the actuator must have a certain speed in order to reach the next position in a given time. The orbit can also often be represented in the form of a curve, such as a position ramp, a speed ramp, or a third or fifth degree polynomial, and in most cases is also 1 to 3 times derivative. The result of the derivation is the velocity curve used, which shows the desired velocity vnf at each point in time. The velocity profile may also be pre-stored, for example, in a table, or determined computationally by the control means 105 to which the station track is entered.

15

Closed position control operates as described above for speed control, but the speed control is replaced by the position control in the form νη / = fx (xKf - x). When using feedrate, the format is: vref '= Vref + fx (Xref - *) One simple position control is 20 forms, for example: fx = Kp-fx ^ f-x), where KP is the gain.

· ·

Exemplary system control for pressure measurement • · • · j · t. ···. Measurement of the pressures pA, Pb can be used to determine the load force • · 25, for example, by the formula (3). As a result, good speed control can be achieved without feedback from speed. • · ** ♦ · optimization of pressures is also better, as measured pressure data is also obtained. Smaller backpressures without the risk of cavitation can also be used, since the pressures are measured. Alternatively, a force transducer may be used to measure force in a manner known per se.

··· * · * ·. The control according to the invention achieves advantages in particular *: * 'in energy saving, in particular the supply pressure ps can be reduced.

V kiinteätilavuuksista When using the pump and setting the supply pressure Ps with a pressure valve 35, and to use a lower input pressure than with symmetrical valves of prior art, where both the pressure and the pressure on the return side of the Common 118 608 20 slide over the pressure drops. Separate valve sets can be individually adjusted to minimize back pressure, while avoiding cavitation.

5 There is greater potential for energy savings when using a variable volume pump, as the operating pressure of the actuator can be optimized as low as possible and the pump supply pressure slightly higher.

It will further be apparent to those skilled in the art that, although the invention has been illustrated in the foregoing description by means of a preferred valve system, the invention may be applied within the scope of the claims. Furthermore, it should be noted that the above function is just one example of the mathematical form of the function that can be converted to computation. For example, when the mathematical form varies, it is possible that the optimum result is obtained by maximizing the function formed. The penalty function and its coefficients may also depend, for example, on the direction and speed of motion.

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Claims (18)

11860? 21 A control system for a pressure medium circuit configured for speed control and / or position control of a pressure medium actuator comprising at least: a first connection (1) coupled between an inlet (P) and a first working connection (A); (2) coupled between an output terminal (T) and a second working interface (B), and valve means (102) for controlling a volume flow of said connections (1,2), said valve means comprising at least a first set (103) and at least a second set 15 (104). ) controlled, parallel opened and closed valves (V1 to V4), whereby the volume flow of the series (103, 104) is defined as the sum of the capacities of the valves being opened each time, and the first series (103) is in series connection with the first connection (1); . The 20 series (104) is serially connected to the second connection (2) * * *. and the control system (100) comprises at least the control means (105, 109) for controlling said valve means (102). The control means are arranged to control each of the valves (V1 - V4) of said sets (103, 104) in an open or closed position, characterized in that:. . The control means (105,109) are arranged to:] · '· - record at least some of the discrete pressure levels and the speeds achieved by said actuator when at least both the first series (103) and the second the valves (V1 - V4) of the series (104) are opened and closed in various possible combinations, and • 118608 22 - to select at least one of these combinations which, according to a set optimization criterion, achieves the desired speed at each instant, and to direct the valves (V1 - V4) of said series to the positions corresponding to the selected combination in each case. Control system according to claim 1, characterized in that it further comprises sensor means for measuring the speed of the actuator, that the control means (105, 109) are arranged to order different combinations according to said optimization criterion, and that the control means (105, 109) are further arranged. to change the current combination into a new combination following the said order so that the difference between the measured speed and the desired speed vw is reduced. 15 Control system according to claim 1 or 2, characterized in that a calculation algorithm is stored in the control means (105, 109) for determining said discrete velocities, the parameters of which describe said actuator and pressure medium circuit. "v 20 Control system according to claim 3, characterized in that it further comprises sensor means for measuring actuator force / pressures, the control means (105,109) being arranged to calculate a selectable combination using a force estimate obtainable by calculation measured force / pressures, and which ku-C; load the said actuator. A control system according to claim 1 or 3, characterized in that the control means (105, 109) are arranged to select said: 30 desired speed based on a set position track stored in the control means (105,109). «· -« »* · · Control system according to any one of claims 1 to 5, characterized in that said computational optimization criterion for comparing different combinations is based on one or more of the following. Criteria: • 118608 23 actuator speed error, preferably the speed error is the difference between the desired speed and the design speed, the set minimum pressure level, 5. the pressure difference to the set reference pressure, - the magnitude of the pressure change in the actuator the sum of one or more of the above criteria, weighted or unweighted. 10 Control system according to claim 6, characterized in that said optimization criterion is defined by a computation algorithm comprising a fine function J of the form J = K0 (| v ^ -v |) x, where X is the desired power, K0 is a weighting factor, v ^ f is the desired speed and v is the calculated speed. Control system according to one of Claims 1 to 7, characterized in that an actuator, which is a cylinder or a motor, is connected to the pressure medium circuit. Control system according to one of Claims 1 to 8, characterized in that the valves have a capacity of * t 1 in each series (103,104). ' arranged in ascending order, for example, said series (103, 104) comprising N valves such that the capacity of the first · ·· * - 25 valves is Q and the successive valves! ·. the capacity is essentially 2 (n'1) * Q, where the variable n is the order number of the valve to obtain the volume flow control step Q, the maximum number of control steps 2N-1, the minimum capacity Q and the maximum capacity Q * (2N-1). Control system according to any one of claims 1 to 9, characterized in that it further comprises feedback means for measuring the speed / position of the actuator, and for determining and supplying a difference between the desired speed / position and the measured speed / position. ·: · 35 peos / station, which in turn generates the new desired speed. «118608 24th A method for controlling a pressure medium circuit arranged for speed control and / or position control of a pressure medium actuator, comprising: a first connection (1) coupled between an inlet (P) and a first working connection (A), a second connection (2) coupled between an output connection (T) and a second working connection (B), 10. valve means (102) for controlling a volume flow of said connections (1,2), said valve means comprising at least a first set (103) and at least a second set (104). ) controlled, parallel opened and closed valves (V1 to V4), wherein the volume flow 15 of the series (103, 104) is defined as the sum of the capacities of the valves being opened each, and the first series (103) is in series connection with the first connection (1) (104 is in series connection with the second connection (2), and ... 20 - control means (105, 109 ) for controlling said valve means \ V (102), which means are arranged to control; ] to divide each valve (V1 - yV V4) of said sets (103, 104) into an open or closed position, t * «*« * * "* 25 characterized in that the method: • · 9 9 9 determines at least some of these discrete pressure levels; the speeds achieved by said actuator when at least one of the valves (V1 to V4) of both the first series (103) and the second series (104) is opened and closed in various possible combinations, - selecting at least one of these combinations, which, according to a set optimization criterion, achieves the desired speed ·: ··, which is desired at each instant, and 35. controls the valves (V1 - V4) of the said series at each time. * to the positions of the selected combination m «- • · · •« 118608 25 A method according to claim 11, characterized by comparing different combinations computationally using an optimization criterion based on one or more of the following criteria: 5. actuator speed error, wherein said speed error is the difference between the desired speed and the calculated speed, the minimum pressure level set; pressure difference to the set reference pressure, 10. the calculated amount of pressure change in the actuator when switching from one combination to another, or the sum of two or more of the above criteria, weighted or unweighted. A method according to claim 11 or 12, characterized in that an optimization criterion is used, which is defined as an algorithm comprising a penalty function J of the form J = K0 <\ Vref -v |) \ where X is the desired power, Ko is weight factor, νηί is the desired speed and v is the calculated speed. 20 A method according to any one of claims 11 to 13, characterized in that said desired speed is continuously determined based on the desired position path. A method according to any one of claims 11 to 14, characterized in that said desired speed is supplied as a set value to the control means (105,109). A method according to any one of claims 11 to 15, characterized by providing said discrete speeds to the control means (105,109) for recording and selection, for example as a table. 44. m 444 4 '··· A method according to any one of claims 11 to 15, characterized by storing in the control means (105, 109) an algorithm for calculating said discrete velocities and describing the parameters thereof. said actuator and pressure medium circuit. il 118608 26 Method according to one of Claims 11 to 17, characterized in that one of these combinations is selected which, in accordance with the set optimization criterion, achieves both the desired speed desired at each moment and the desired pressure level which fulfills the set optimization criterion when the actuator is controlled. • · • · • i • * • * • · * · t • · * »·· * • 4 ··« M «| * »« • · • ' 9 I »·» · 4 • 4 • * ··· Φ 9 · »· ♦ • I <· -m · '*!> 118608 27