A semi-active damper

Description

The present invention relates to a semi-active shock absorber, and more generally to a shock absorber control system that includes a direct control loop including an inverse model of the shock absorber, A solution is already known from the patent application FR-9408337 of the present application which uses the principle of force tracking by means of an inverse model with an open control loop. In the case of a semi-active shock absorber controlled by the above control, the control device comprises a direct control loop which includes the inverse model of the shock absorber. The inverse model of the shock absorber determines the value of the nominal control current (ith) required to control the pressure-side and expansion-side throttle valves, namely on the basis of the measured value of the relative speed (y) between the two end positions of the shock absorber and the reference force (Fc). The above solution uses a force feedback loop to take into account a correction factor (5y) proportional to the nominal value of the control current (ith), taking into account the force error (eF) between the measured value of the reference force (Fc) and the force (F) actually exerted by the shock absorber. The inverse model of the shock absorber can be defined by the following expressions: - K13 and K23 - positive constants depending on the size of the actuator, the physical properties of the working medium, and the flow rate of the valves; - y - measured value of the relative velocity between the two end positions of the shock absorber; - Fc- reference force. The above inverse model of the shock absorber assumes that the working medium used is incompressible. We note at the outset that this is not necessarily the case. The aim of the present invention is to create an improved solution for the continuous control of the force exerted by a semi-active shock absorber, which allows a certain degree of compressibility of the working medium to be taken into account, without this adversely affecting the system. The object of the present invention is achieved by a semi-active shock absorber having a pressure-side check valve and an expansion-side check valve and having a control connection with a control circuit. This control circuit has a direct control circuit, which includes an inverse model of the shock absorber, which, based on physical values, determines the nominal value of the electric current of the pressure-side controlled throttle valve and the expansion-side throttle valve of the shock absorber - or a single combined valve performing these two functions - based on the measured value of the relative speed between the two ends of the shock absorber and the reference force. The essence of the inverse model includes: a) a first unit determining the pressure loss ΔΡν of the active controlled throttle valve; b) a second unit for calculating the nominal control current ith of the active controlled throttle valve; c) a third unit calculating the correction factor 5y for the relative y velocity; and d) a summing circuit calculating the sum of the measured value of the speed ay and the speed correction factor öy to determine the equivalent speed y, which calculates the nominal itfl control current taking into account the pressure loss ΔΡν of the active throttle valve and the equivalent speed y. A design that also has a fourth unit that calculates the pressure loss of the open pressure-side check valve and the expansion-side check valve is advisable. Preferably, the output signals of the fourth unit calculating the pressure loss of the open throttle are interpolated from a characteristic matrix whose matrix elements are determined as a function of the input speed values ​​and control current values ​​of the fourth unit. Preferably, the active controlled throttle pressure loss determination unit is designed to determine an estimated pressure loss to be created by the active controlled throttle valve arranged between the pressure chamber of the shock absorber and its accumulator. The output pressure drop of the first active controlled throttle pressure loss determination unit is calculated from the following equations as a function of the two input values ​​of the unit, namely the reference force Fc and the pressure drop ΔΡει_: APv=[Fc-APcl S2] / S1; (throttle valve is pressureless; in this case the shock absorber is in expansion), or APv=[-Fc-APCLS1] / S2; (in the throttle valve under pressure; in this case the shock absorber is under compression), where - S·) - the pressed surface of the piston on the piston rod side, - S2- the pressed surface of the piston on the rod-free side, - Fc- the reference force, - APCL- pressure loss of the open check valve. The measured value of the relative velocity y between the two end positions of the shock absorber can be used to determine the velocity correction factor, which in turn determines the equivalent velocity, as follows: 5y=e(y) r(y) ^1, where: dt - 5y=speed correction factor, - ε(Ϋ)=—1, if y >0 (in expansion), and - ε(γ)=1, if y <0 (for compression), - r(y) - velocity function, HU 225 356 B1 - ΔΡν- pressure loss at the outlet of the first unit, _ dAPv _g is the derivative of pressure loss (ΔΡν) with respect to time (t) dt. The characteristic of the controlled throttle valves is preferably determined in advance according to a nonlinear K(i) function, the value of which is obtained from the measured ΔΡν-measured pressure loss of the valve, as well as the equivalent velocity y generated from the measured pressure loss APv and the measured values ​​of the relative velocity (y), and the control current i according to the following relationship: ΛΡ ΗΗ , J / e-measured | J e-measured The value of the nominal ittl control current is preferably determined by minimizing the error function εΚ(ί) to the permissible current values, i.e.: ε K(ith)=minj[eK(i)]=minj K( / )ΔΡ„ |ye|ye, where: - K(i) - nonlinear function determined from measurements, - ΔΡν- the pressure loss to be achieved, which is obtained at the outlet of the unit to determine the pressure drop of the active valve, - ye- is the calculated equivalent speed at the output of the summing circuit. According to a further feature of the invention, it is expedient to introduce a proportional correction factor δί, which is smaller than the nominal control current ith, by means of a secondary force feedback circuit, to take into account the force error cF between the reference force Fc and the measured value of the actually exerted force F. The value of the reference force Fc can be calculated from the following equation: Fc=(1-q) Cvy|y|+q Usa; where q=min(|y| / V0,1); where - Usa- high speed control force, - Vo- speed threshold, - Cv-y|y|_square value; to eliminate the uncertainty of the control current at zero speed, in which Cva is a constant for the throttle valve. In our description, we call a force control circuit “direct” if it does not require the use of force sensors. The main advantage of the semi-active shock absorber according to the invention is that, by using the equivalent velocity, it takes into account for the first time a certain degree of compressibility of the working medium. The inverse model of the semi-active damper according to the invention therefore determines the nominal value of the control current ilh required to control the pressure-side controlled throttle valve and the expansion-side controlled throttle valve (or a single combined valve combining both functions), based on the measured value of the relative velocity y between the two end positions of the damper and the reference force Fc. The force used to control the semi-active shock absorber according to the invention significantly simplifies the system, since only the damping force is needed to optimize the dynamics of the system, not the speed. Thus, the continuous force control structure according to the invention is always able to follow the reference force, i.e. to continuously determine an infinite number of relationships between force and speed, in contrast to the controlled shock absorbers according to the prior art, the control system of which has limited capabilities in this regard. A further advantage of the continuous force control device for controlling the semi-active shock absorber according to the invention is that it allows the use of standard and inexpensive hydraulic elements. The continuous force control device for controlling the semi-active shock absorber according to the invention enables the proposed system to operate satisfactorily with less instrumentation, even with a single speed sensor. For example, if the force sensor fails, the correction factor (δί) will be zero, but its main effect on the nominal control current ith (based on the value of the reference force Fc and the measurement of the control force acting on the shock absorber) alone ensures satisfactory operation. The invention is described in more detail with reference to the attached drawings. In the drawings: Figure 1 is a schematic diagram of a conventional semi-active shock absorber; Figure 2 is a block diagram of a control mechanism for the shock absorber of Figure 1; Figure 3 is a schematic circuit diagram of the semi-active shock absorber with continuous force control according to the invention; and Figure 4 is a block diagram of the control mechanism of the shock absorber according to Figure 3. Figure 1 shows a schematic diagram of a semi-active controlled shock absorber according to patent application FR-9408337 (published under number FR27 22 265). It has a cylindrical housing 1 in which 2 pistons with 3 piston rods are displaceably arranged, so that this structural unit as a whole forms 14 control units. The piston 2, in the position shown in Figure 1, defines a lower chamber 4, which is referred to as the “pressure chamber”, and with its opposite side defines an upper chamber 5, which is also referred to as the “expansion chamber”. The chambers 4 and 5 of the housing 1 are filled with a liquid, for example hydraulic oil, as the working medium in this case. The semi-active damper also includes a one-way flow check valve 7, also referred to as the "expansion-side" check valve, and another one-way flow check valve 8, also referred to as the "pressure-side" check valve. HU 225 356 B1 The shock absorber according to Figure 1 has a first hydraulic throttle valve 9, also referred to as the “compression-side” throttle valve, and a second hydraulic throttle valve 10, also referred to as the “expansion-side” throttle valve. The throttle valves 9 and 10 are electrically controlled. The semi-active shock absorber also includes a pressure accumulator 11, which is slightly pressurized during assembly of the semi-active shock absorber. The accumulator 11 is a hydropneumatic accumulator, the predetermined fixed volume of which receives a pressurized inert gas charge and hydraulic oil, and in the closed space the gas exerts pressure on the oil. In the accumulator 11, the two media are usually separated from each other by a membrane or balloon, not shown separately. The task of the accumulator 11 is to absorb the amount of oil corresponding to the volume of the piston rod 3 when the piston 2 of the shock absorber is fully retracted, and on the other hand, to ensure the minimum necessary oil pressure in the hydraulic circuit. The operation of the semi-active shock absorber according to Figure 1 does not require any other external hydraulic power source, such as a high-pressure accumulator or pump. The expansion-side check valve 7 and the controlled throttle valve 10 are connected in parallel with each other and are located between the expansion chamber 5 and the accumulator 11. The pressure-side check valve 8 and the controlled throttle valve 9 are also connected in parallel with each other, but are installed between the chamber 4 and the accumulator 11. According to Figure 1, the semi-active shock absorber in this case includes 12 force sensors and 13 speed sensors for sensing relative speed. Figure 2 is a block diagram of the control circuit of the semi-active controlled shock absorber of Figure 1, in which the symbols used have the following meanings: - Fc- reference force; - F - actual damping force; - Fm- force measured by the force sensor, - eF - force error (calculated from the equation EF=Fc-Fm), - y - relative velocity between the two end positions of the shock absorber; - i - control current for controlling throttle valves 9 and 10; - ith- the value of the nominal control current determined by the inverse model, which is applied to the controlled throttle valves 9 and 10 to determine the reference force Fc, - δί - correction factor (in the formula i=ith+Si, to take into account the force error eF). The circuit diagram of Figure 2 includes, in addition to the above-mentioned force sensor 12 and speed sensor 13, a control unit 14, an inverse model 15, a force feedback loop 16, a corrector unit 17, a speed feedback loop and a main direct controller, which will be discussed in more detail below. The operation of the above semi-active shock absorber is described below with reference to Figures 1 and 2. Two phases of the hydraulic operation of the controlled semi-active shock absorber can be distinguished, namely the first phase, called the “compression phase”, in which the piston 2 is pushed into the housing 1, the direction of which is indicated by arrow C in Figure 1; and the second phase, called the “expansion phase”, in which the piston 2 is moved upwards in the housing 1 in Figure 1. During the compression phase, the piston 2 moves in the direction of arrow C, i.e. downwards in Figure 1, while during the expansion phase, the piston moves in the direction of arrow D in the housing 1, from bottom to top. During the compression phase, the liquid stored in the chamber 4 is compressed, the check valve 8 closes at this time, thereby forcing the liquid to flow only through the throttle valve 9 with a controlled flow cross-section. The check valve 7, on the other hand, allows the working medium 6 in the chamber 4 to bypass the controlled throttle valve 10 and freely enter the chamber 5. The control of the throttle valve 9 allows the pressure in the chamber 4 to be controlled, and thus the reaction force that occurs during the compression of the shock absorber. In the expansion phase of the control unit 14, the above elements exchange roles; the expansion-side throttle valve 10 regulates the outflow of the working medium 6 from the chamber 5, thereby allowing the expansion force to be controlled, while the check valve 7 closes. The check valve 8 is then active, therefore allowing the free inflow of the working medium 6 into the chamber 5. The throttle valves 9 and 10 are electrically controlled in such a way that they always modulate the damping force opposite to the speed. It follows from the above that the damping always remains a dissipative system (note that the term “dissipation” in vehicle technology refers to an irreversible process occurring inside the system, in this case the process of converting kinetic energy into heat in the case of the shock absorber). The modulation of the applied force allows the force (not shown in the figure) to be servo-controlled in relation to the computer-generated Fcreference force. The fundamental problem with the above solution is how to determine the control current to be given to the throttle valves 9 and 10 in order to achieve the desired Fcreference force. If we assume the equilibrium relations for the flow rates of the two chambers of the shock absorber at constant velocity, both in the compression and expansion phases, then we can derive a simple relation between the nominal ith control flow provided by the inverse model of the shock absorber 15, the instantaneous relative velocity y and the damping force F. In the compression phase, this relation is given by the following equation: HU 225 356 Β1F=P. Gi s2y2+| s, Cd- Α3ι(ΔΡ3ι) SryMPs-PeJS,; where: - F - the applied damping force, - p - density of the working medium, for example oil, - S·, - the cross-sectional area of ​​the piston on the side free from the pistons, exposed to pressure, - S2- the cross-sectional area of ​​the piston exposed to pressure on the side with the piston rod, - St- piston rod cross-sectional area, - y - relative velocity between the two ends of the shock absorber, - Gj - pressure increase of the control valve, - i - control current, - Cd- expansion side check valve flow coefficient, - A31- expansion side check valve flow cross-section, - ΔΡ31- pressure drop between the accumulator and the chamber during suction, - P3- pressure inside the accumulator, - Pe- atmospheric pressure. This damper model can be used in the sense of determining the nominal control current ith of the controlled throttle valves as a function of the reference force Fc and the measured relative velocity y. These values ​​can be obtained by using the inverse model of the damper 15. Due to the simplifications applied to the damping equation, a proportional correction factor 5i can be introduced in the inverse model 15 via the force feedback loop 16. For the value of Fmeasure measured by the force sensor 12, the force feedback circuit allows the generation of the force error signal eF between the value of the reference force Fc and the measured value of Fmeasure. This force error signal eF is fed to the corrector unit, which corrects the value of the control current i to be supplied to the throttle valves 9 and 10 with the additional correction factor öi. The value of the relative velocity y is input into the inverse model of the shock absorber 15 via the velocity feedback loop 18, which also includes the velocity sensor 13. The nominal ith control current value is generated by the inverse model of the shock absorber 15. The nominal ith control current is fed through the main direct control circuit 19 to the controlled hydraulic throttle valves 9 and 10 to generate the reference force Fc. The direct control circuit 19 includes the inverse model 15. The nominal ith control current is determined from the following expressions: during compression (y <0), where ith=K23-p=; during expansion (y >0), and #c| are positive constants K13 and K23, which depend on the control unit, the physical properties of the hydraulic oil, and the current flow rates of the controlled throttle valves 9 and 10. Such a semi-active shock absorber can be satisfactorily used, for example, for the transverse secondary suspension of railway passenger cars. In the following description, the semi-active shock absorber with continuous force control according to the present invention is described with reference to Figures 3 and 4. Figure 3 shows the circuit diagram of the shock absorber according to the invention, and Figure 4 shows an exemplary embodiment of the semi-active continuous force control unit according to the invention in a block diagram. The solution shown in Figure 4 can be considered a further development of the conventional solution according to Figure 2, therefore, similar elements are indicated by the same reference numbers in Figures 2 and 4. In the exemplary embodiment shown in Figures 3 and 4, 17 corrector units and 12 force sensors are also shown, but these are not necessarily necessary for the solution according to the invention. As explained above, a conventional shock absorber exerts a damping force Fv as a function of the velocity y, but without providing the possibility of external control. In the case of the force-controlled shock absorber, according to the invention, this cause-and-effect relationship is reversed, i.e., the control parameter, i.e. the nominal ith control current value for controlling the valves, is determined based on the knowledge of the speed y and the reference force Fc, which then allows the value of the actually exerted Fshock to be equal to the value of the reference force F. Based on the knowledge of the physical properties of the structure, our invention made it possible to implement a model of the system in which the relative velocity y, the reference force Fc, and the nominal control current ith are assigned to each other, and with these, the original development of the inverse model became possible. According to the invention, the equivalent velocity y is derived from the relative velocity y, thereby extending the control principle to systems that operate with a somewhat compressible working medium. Traditional servo control techniques based on force error (eF=Fv-Fc) would not be effective in this application, as they require the actual applied damping force F to be measured in the main circuit. In contrast, we have developed an open loop control system that allows the nominal control current ith to be determined directly from the desired reference force Fc and the relative y HU 225 356 Β1 as a function of speed, but without measuring the force for this. The following description concerns the correction to be applied to the movement speed, which is determined based on the estimation of the pressure dynamics, and introduces the concept of "equivalent speed". According to practical experience, a certain degree of compressibility of the working medium causes the force / velocity characteristic Fv=fct(y,i), which, however, exhibits hysteresis, and is therefore not suitable for use in traditional inverse models designed for incompressible fluids. The value of the velocity y is therefore corrected in the form of an equivalent velocity ye to obtain a clear definition of the characteristic Fv=fct (ye, i), which already allows the use of the principle of the inverse model. Namely, a certain degree of compressibility of the working medium has an effect on the equations relating to the continuity of the fluid quantities in the compression and expansion chambers 4 and 5 (namely, in the form of the compressible flow quantity associated with the derivative of the pressure). The value of the velocity y is therefore corrected by a factor that is proportional to the derivative of the pressure in the pressurized chamber, thereby reducing it to a form (analogous to that which we would obtain assuming that the working medium is incompressible). Ignoring the pressure changes in the accumulator 11, the operating pressure in the pressure chamber is essentially the same as the pressure drop ΔΡν desired across the active opening of the controlled throttle valve. The equivalent velocity y is calculated from the following equation: . . ... ... dAPvye=ysgn(y)r(y)·——. dt The sgn(y) in the above equation is the sign function (signum function), which refers to the operating state when the r(y) term is modulated according to the relative velocity y (where the last fraction is the time derivative of the ΔΡν pressure loss). The following describes the operation of the controlled throttle valve. The positive value corresponds to the theoretical assumption that takes into account a certain degree of compressibility of fluids. The negative value, on the other hand, allows the use of an equivalent speed, which serves to limit the speed at which the controlled throttle valve would close (for lower speeds), thus avoiding any kind of hydraulic "blocking". To determine the reference force Fc, we start from a control equation derived from the optimal control principle and, for example, limit the value of the reference force to the dissipation range. In Figure 4, the control force is denoted by U, from which 21 units calculate the required force. This is determined by the physical properties of the shock absorber in its fully compressed position (in which case the controlled throttle valve is fully open) and in its fully extended position (in which case the controlled throttle valve is minimally open). In accordance with the semi-active mode of operation, the resulting dissipation control force is denoted by “Usa” below. Furthermore, since the natural characteristics of the system vary quadratically when a given valve is opened at low reference speeds (at the V threshold speed), the following relationship (Cvy |y|) is used to avoid any uncertainty regarding the control current to be applied to the valve at zero speed (where Cva is a constant for the throttle valve): Fc=(1-q)cv y|yl+q Usa; where q=min(|y| / V0, 1); where - Usa- resulting dissipation control force, - Vo- speed threshold, - CvylyI - square value, where Cv is a constant for the throttle valve. If the value of |y| is less than the Vo speed threshold, then we increase the passive damping and the dissipation control force; on the other hand, if the value of |y| is greater than the Vo speed threshold, then Fc=q Usa. Figure 3 therefore shows an exemplary embodiment of the hydraulic circuit of the force-controlled semi-active shock absorber according to the invention. Here, P1 denotes the pressure in the expansion chamber 5, P2 denotes the pressure in the compression chamber 4, and P3 denotes the pressure in the accumulator 11. Furthermore, the reference symbol CL denotes the pressure-side check valve 8 and the reference symbol CLc denotes the expansion-side check valve 7 (in accordance with the designations used in Figure 1). In Figure 3, reference symbols Vc and V indicate, as a further embodiment, the flow openings of a combined controlled throttle valve 20 (for example, a 4 / 2-type valve), or, as an alternative embodiment, the flow openings of two separate 2 / 2-type throttle valves in the controlled throttle valves 9 and 10. One advantage of this embodiment of the invention is that a single controlled valve 20 is used, which has two controlled ports Vd and Vc, which are controlled in parallel, as shown in Figure 3. In the expansion phase (i.e. when the piston 2 moves in the direction of arrow D), the check valve 8 opens, short-circuits the hose opening Vc of the throttle valve 20 and allows the free filling of the chamber 4. The check valve 7 is closed during this time. The flow cross-sectional area of ​​the active hose opening Vd of the throttle valve 20 is controlled, thereby regulating the pressures prevailing in the housing 1 and, through this, the force F exerted by the piston rod 3 of the shock absorber in the expansion phase. The operation is naturally reversed during the compression phase, when the piston 2 moves in the housing 1 in the direction of arrow C. The force F exerted by the shock absorber can be calculated from the following equation: HU 225 356 B1 F=(P1-P3)S1-(P2-P3)S2-(P3-Pe)S„ where F - Fv-Fpneu; within this Fv-(Pi-P3) Si-(P2-P3) S2, and Fpneu-(P3—Pe)'§t From the above relationship, the only force of interest to us is the damping force F (the factors in the relationship have already been mentioned above, but we will not deal with the pneumatic force F here). Below we will show through an example (referring to Figure 3) how the calculations are performed in the expansion phase. The pressure loss across the open check valve 8 can be given as a function of the speed y and the control flow applied to the controlled throttle valve (given in the table), which is actually a correction factor. The control flow allows us to take into account the effect of opening the Vc hose opening on the amount of working medium flowing through the check valve, according to the following relationship: APCLd=P3_P2=GCLd (y- 'th)· The desired pressure loss value at the Vd hose opening of the active controlled throttle valve 20 can be calculated based on the relationships relating to Fc and APCi_ as follows: áPv=P1-P3=(Fc-áPclS2) / S1. If we differentiate the value of ΔΡνpressure loss with respect to time and then multiply it by the term y - r(y), which varies according to the velocity function ar(y), then we can simply determine the equivalent operating speed y from the following formula: The nominal ith control current has already been calculated to determine the operating limit from the following equation: APv=fct (ith, ye). The pressure drop parameter was previously defined as the (tabular / matrix) form of the nonlinear function K(ith), as follows: ΔΡν=Κ(ΐ#,)|ΫβΐΎβ· According to the principle of the inverse model, the nominal control current ith is determined as follows: In the following description, we will deal in more detail with the main direct control loop 19 and the inverse model 15. In Figure 4, the structural units of the inverse model 15 are delimited by a dashed line. The nominal ith control current is determined using the inverse model of the shock absorber 15 as a function of the reference force Fc and the relative speed y measured by the speed sensor 13. The inverse model 15 according to the invention includes several units, namely the following: - a first unit 15B for determining the pressure loss ΔΡν of the active controlled throttle valve; - a second unit 15C for calculating the nominal ith control current to be applied to the active controlled throttle valve; - a third unit 15D for calculating the correction factor 5y for the y speed; - a fourth unit 15A, whose task is to calculate the pressure loss ΔΡει_ of the open check valve; - a summing circuit 15E, the task of which is to calculate the sum of the measured y speed and the correction factor 6y to determine the equivalent y speed. With the circuits of the above units of the 15 inverse model, based on the physical interpretation of the damping system, we determine the estimated physical parameters, namely: - the estimated value of the pressure loss ΔΡοι of the open check valve; in the expansion phase this estimated pressure loss APCL is equal to the estimated value P3-P2 for the check valve 8; however, during the compression phase this estimated pressure loss APCL is equal to the estimated value Ρ3-Ρ·ι for the check valve 7; - the estimated ΔΡνpressure loss to be achieved by the active controlled throttle valve located between the pressurized chamber 4 and the accumulator 11. During the expansion, this estimated ΔΡνpressure loss at the throttle valve 10 is P-1-P3; during the compression phase, however, the ΔΡνpressure loss is equal to the estimated P2-P3 value of the throttle valve 9; and - the calculated equivalent speed value ye=y+öy, which is the sum of the measured speed y and the correction factor Sy. The units of the inverse model of the shock absorber 15 perform the following functions: The fourth unit 15A calculates the pressure loss APcl of the open check valve, i.e. the losses through the check valve 8 during expansion and through the check valve 7 during compression. The output APCL value of unit 15A is interpolated from a characteristic matrix, the values ​​of which are given in tabular form as a function of the input values ​​of said unit 15A, i.e. the relative speed y and the control current ith. The first unit 15B produces the value of the pressure loss ΔΡν of the active controlled throttle valve located between the pressurized chamber 4 and the accumulator 11. The output value of the pressure loss ΔΡν of the unit 15B is calculated from the values ​​of the two input values ​​of the unit, i.e. the reference force Fc and the pressure loss APcl, as follows: APv=[Fc-APCLS2] / S1(at expansion; at throttle valve 10) and APv=[-Fc-APCLS1] / S2(compression phase at throttle valve 9), where - S1- the pressed surface of the piston on the piston rod side, HU 225 356 B1 - S2- the pressed surface of the piston on the rod-free side, - ΔΡν- pressure loss at the outlet of unit 15B, - APcl- pressure loss of the open check valve. In order to take into account the compressibility of the liquid, the measured velocity value y is corrected according to the invention by the correction factor öy obtained from the third unit 15D, in order to obtain a velocity equivalent to ye at the output of the summing circuit 15E, from the following relationship: ye=y+Sy. The third 15D unit calculates the correction factor for the speed öy based on the following formula: 5y=e(y) r(y)·^^, where dt - s(y)=-1 / if y >0 (for expansion), and e(y )= 1 if y <0 (for compression), - r(y) - velocity function, - ΔΡν- pressure loss at the outlet of the first unit (15B), --- - the derivative dt of the pressure loss (ΔΡν) with respect to time (t). The task of the second 15C unit is to calculate the nominal control flow rate as a function of the two values ​​entered into the 15C unit, i.e. the ΔΡν pressure loss and the equivalent velocity values. The cross-sectional areas of the Vc and Vd hose openings of the controlled throttle valves 9 and 10 are determined in advance according to the nonlinear K(i) function; their value can be calculated from the measured APv_measured pressure loss of the throttle valve 9 or 10, and from the measured ye-measured value of the equivalent ye velocity calculated from the values ​​of the ΔΡν pressure drop, the velocity y and the control current i, according to the following relationship: e-measure IXe -measure In the second unit 15C, we utilize this relationship to determine the function K(ith) of the nominal ith control current satisfying the following condition: ΔΡ, |ye|ye' K(ith):where - K(i) is a nonlinear function determined based on measurements; - ΔΡν is the pressure loss to be achieved, as calculated as the output value of unit 15B; and - ye is the equivalent speed obtained at the output of the summing circuit 15E. The nonlinear function used to determine the above parameter is reformulated as a minimization problem as follows; the value of the control current ilh is calculated so that it minimizes the error function εΚ(ϊ) within the acceptable range: 8K(ith)=mini[εΚ(ϊ)]=πιίηί K( / )Δ^ |ye|ys; where: - K(i) - nonlinear function determined from measurements, - ΔΡν- is the pressure loss, which can be measured at the output of the first unit 15B determining the pressure drop of the active throttle valve, - ye- calculated equivalent speed, which appears at the output of the summing circuit 15E (see Fig. 4).

Claims

15 PATENT CLAIMS 1. A semi-active shock absorber having a pressure-side check valve (8) and an expansion-side check valve (7) and being in control connection with a control circuit 20 having a main direct control circuit (19), comprising an inverse model of the shock absorber, which, based on physical values, determines the nominal value (ith) of the electric control current of the pressure-side controlled throttle valve (10) and the expansion-side throttle valve (9) of the shock absorber, or a single throttle valve (20) performing these two functions, based on the measured value of the relative speed (y) between the two ends of the shock absorber and the reference force (Fc), characterized in that the inverse model (15) comprises 30: e) a first step determining the pressure loss (ΔΡν) of the active controlled throttle valve (9, 10) a unit (15B); f) a second unit (15C) for calculating the nominal control current (ith) of the active controlled throttle valve (9, 10);g) a third unit (15D) for calculating a correction factor (öy) for the speed (y); and h) a summing circuit (15E) for calculating the sum of the measured value of the speed (y) and the correction factor (öy) to determine an equivalent speed (ye), which is designed to determine the nominal control current (ith) by means of the pressure loss (ΔΡν) of the active throttle valve and the equivalent speed (ye).; 2. The shock absorber according to claim 1, characterized in that the inverse model (15) also has a fourth unit (15A) for calculating the pressure loss (APCL) of the open check valve (7, 8). 50 3. A shock absorber according to claim 2, characterized in that the output signals of the fourth unit (15A) for calculating the pressure loss of the open check valve (APCL) are interpolated from a matrix whose elements are determined as a function of the input signals of the unit (15A) of the speed (y) 55 and the nominal control current (ith).

4. The shock absorber according to claim 1, characterized in that the pressure loss determining unit (15B) of the active controlled throttle valve is designed to determine the value of the pressure loss (ΔΡν) of the active controlled throttle valve (9, 10) arranged between the pressure chamber and the accumulator (11) of the shock absorber.

5. The shock absorber according to claim 4, characterized in that the value of the output pressure drop (ΔΡν) of the unit (15B) determining the pressure loss of the active controlled throttle valve (9, 10) is calculated from the following relationships as a function of the two input values ​​of the unit (15B), namely the reference force (Fc) and the pressure drop of the open check valve (APCl): APv=[Fc-APCLS2] / S1; (at the throttle valve 10; at the expansion of the shock absorber), and APv=[-Fc-APCL-S1] / S2; (at the throttle valve 9; at the compression of the shock absorber), where 15 - S1 - the pressed surface of the piston on the piston rod side, - S2 - the pressed surface of the piston on the rod-free side, - ΔΡν - pressure loss at the outlet of the unit (15B), - aPcl - pressure loss of the open check valve.

6. The shock absorber according to claim 1, characterized in that the speed correction factor (5y) is calculated by the third unit (15D) from the following expression: Sy=e(y) r(y)-5^, where dt 30 - s(y)=—1, if y >0 (for expansion), and - s(y)=1, if y <0 (for compression), - r(y) - speed function, - ΔΡν - pressure loss at the outlet of the first unit (15B), 35 - - the derivative of the pressure loss (ΔΡν) with respect to time dt.

7. The shock absorber according to claim 1, characterized in that the characteristic of the controlled throttle valve (9, 10) is predetermined according to a nonlinear function [K(i)j, the value of which is obtained from the measured pressure loss (APv.measured) of the throttle valve (9, 10) and the measured value of the equivalent velocity (ye) (ye-measured) calculated from the values ​​of the pressure drop (ΔΡν), the velocity (y) and the control current (i) according to the following relationship: | / e- measured / e- measured 8. A shock absorber according to claim 7, characterized in that the nominal control current (ith) is determined by minimizing the error function [sK(i)] to the permissible control current values, from the following relationship: EK(ith)=mini[eK(i)]=mini ΔΡ„ |ye|y where: - K(i) - a nonlinear function determined from the measurements, - ΔΡν - the pressure loss to be realized, which appears at the output of the first unit (15B) estimating the pressure drop of the active throttle valve (9, 10), - ye=calculated equivalent speed, which appears at the output of the summing circuit (15E).

9. A shock absorber according to any one of claims 1-8, characterized in that it has a secondary force feedback circuit (16), which is designed to take into account a correction factor (öi) proportional to the nominal control current (ith), thereby forming a force error (sF) between the measured value of the reference force (Fc) and the actually exerted force (F).

10. A shock absorber according to any one of claims 1-9, characterized in that the reference force (Fc) is determined from the following relationship: Fc=(1-q) Cv-y|y|+q-Usa; where q=min(|y| / V0,1), where - Usa - damping force corresponding to high speed, - Vo - speed threshold value, - Cv y|y|- squared value, in which Cv is a constant related to the throttle valve.