CN108459499B - Optimal obstacle avoidance method and system for inhibiting liquid shaking time - Google Patents
Optimal obstacle avoidance method and system for inhibiting liquid shaking time Download PDFInfo
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Abstract
An optimal obstacle avoidance method and system for inhibiting liquid shaking time comprises (1) carrying out region division on a phase plane formed by horizontal position errors and speed errors of a relative landing point in an obstacle avoidance process of a spacecraft; (2) determining a control law when the current horizontal position error and speed error data of the spacecraft are in different regions; (3) and the spacecraft calculates an air injection pulse width command according to the determined control law, performs translational obstacle avoidance control, and realizes obstacle avoidance with optimal liquid shaking inhibiting time. The invention solves the problem of liquid shaking excited by translational control, and reduces the posture shaking angle in the translational process.
Description
Technical Field
The invention relates to an optimal obstacle avoidance method and system for inhibiting liquid shaking time, and belongs to the field of spacecraft guidance control.
Background
For a deep space soft landing detector, the deep space soft landing detector generally needs to keep a vertical posture when the deep space soft landing detector finally approaches the surface of a celestial body, and horizontal position and speed control are implemented by means of a translation engine, so that the functions of obstacle avoidance and safe soft landing are realized.
The translational control of the obstacle avoidance process of the existing lunar lander is realized by using a phase plane method. Several switch lines are arranged on the phase plane formed by the position error and the speed error, and when the switch lines pass through and enter the air injection control area, the air injection full pulse width instruction in the corresponding direction is output. The method is simple and easy to implement. However, when the landing gear uses a surface tension reservoir, it is difficult to design out the problem of exciting liquid sloshing using a phase plane approach that is inherently specific to rigid application environments. This causes potential risk to this kind of lander that uses surface tension storage tank, has the translation control to arouse that liquid rocks and makes the gesture range of oscillation increase constantly, and influence the problem of translation control effect in return.
Disclosure of Invention
The invention solves the problems: the method and the system overcome the defects of the prior art, provide the optimal obstacle avoidance method and the optimal obstacle avoidance system for inhibiting the liquid shaking time, solve the problem that liquid is excited to shake by translational control on the premise of keeping the translational rapidity, and reduce the posture shaking angle in the translational process.
The technical scheme adopted by the invention is as follows:
an optimal obstacle avoidance method for inhibiting liquid shaking time comprises the following implementation steps:
(1) carrying out region division on a phase plane formed by horizontal position errors and speed errors of a relative landing point in the obstacle avoidance process of the spacecraft;
(2) determining a control law when the current horizontal position error and speed error data of the spacecraft are in different regions;
(3) and the spacecraft calculates an air injection pulse width command according to the determined control law, performs translational obstacle avoidance control, and realizes obstacle avoidance with optimal liquid shaking inhibiting time.
The area division of the phase plane in the step (1) is specifically as follows:
the phase plane is divided into an inner rectangular area and an outer Bang-Bang control area, the Bang-Bang control area is divided into a positive spray area and a negative spray area by two parabolas, and R+Is a forward full spray area controlled by Bang-Bang; r-Is a negative full spray area controlled by Bang-Bang; r0Is a PD control area, i.e. a rectangular area.
R+Region and R-The division line of the region satisfies the relational expression
Lc＝-dLc|dLc|/(2·aref)
Wherein, arefThe reference acceleration on the horizontal axis is greater than the thrust acceleration generated by the translation engine of the lander; the position error of the relative landing point on the horizontal axis is LcAt a speed dLc(ii) a The horizontal axis refers to: axis of the body of the lander parallel to the horizontal plane in the nominal attitude.
PD control area range | Lc|<LHmAnd | dLc|<dLHmWherein L isHmIs the position control error bound, dLHmIs the speed control error bound.
Determining a control law when the current horizontal position error and speed error data of the spacecraft are in different regions, specifically:
(a) when phase point, i.e. (L)c，dLc) At R of+In the area, the horizontal axis forward thruster outputs full pulse width, namely the forward thruster always jets air in the current control period;
(b) when the phase point is at R-When the area is in, the horizontal axis negative thruster outputs full pulse width; namely, the negative thruster always injects air in the current control period;
(c) when the phase point is at R0Region or once at R0And in the area, calculating the command thrust acceleration according to a PD control law, modulating the command thrust acceleration into the jet pulse width of the translation engine, and finally outputting the command thrust acceleration according to the jet pulse width duration by using a positive thruster or a negative thruster according to the direction of the jet pulse width.
The PD control law specifically comprises the following steps:
ac＝-kpsLc-kdsdLc
wherein k ispsIs the proportionality coefficient, kdsIs the differential coefficient, kpsAnd kdsThe parameter value is taken so that the bandwidth of the horizontal axis closed-loop system is 1 order of magnitude lower than the shaking frequency of the liquid in the storage tank, acIs the commanded acceleration.
The modulation is the jet pulse width of the translation engine, and specifically comprises the following steps:
(c1) calculating the ratio W of the command thrust to the actual thrust;
W＝|Y|/Fhwherein Y is the commanded thrust and Y ═ macLander mass m, FhIs the translational engine thrust on the horizontal axis;
(c2) determining an intermediate variable WcAnd PonA value of (d);
if W>1+HH2Then, then
Wc＝1；
Pon＝∞；
If 1+ HH2≥W>HH1Then, then
If W is not more than HH1Then, then
Wc＝0；
Pon＝tmin；
Wherein, tminIs minimum jet pulse width, HH1、HH2And TmThree design parameters for pulse width modulation;
(c3) calculating the remaining air injection time PWI: will PWI-WcΔ t sign (PWI) assigned to PWI;
the control period is delta t, sign is a sign function, 1 is output when the input is a positive number, minus 1 is output when the input is a negative number, 0 is output when the input is 0, and the initial value of PWI is 0;
(c4) calculating an air injection pulse width PW:
if | PWI | > Δ t, then
PW＝Δt·sign(PWI)；
If the | PWI | is less than or equal to delta t and the | PWI | phosphor<PonThen, then
PW＝0；
If the absolute PWI is less than or equal to delta t and the absolute PWI is more than or equal to PonThen, then
PW＝PWI；
PW is a signed parameter, the sign representing the direction of the jet and the magnitude representing the pulse width of the jet.
An optimal obstacle avoidance system for suppressing liquid sloshing time, comprising:
a region division module: the method is used for carrying out region division on a phase plane formed by horizontal position errors and speed errors of a relative landing point in the obstacle avoidance process of the spacecraft;
a control law determination module: the control law is used for determining the current horizontal position error and speed error data of the spacecraft when the data are in different regions;
keep away barrier control module: the method is used for calculating the air injection pulse width command according to the determined control law by the spacecraft, carrying out translational motion obstacle avoidance control and realizing the obstacle avoidance with optimal liquid shaking time inhibition.
The area division module is used for carrying out area division on a phase plane formed by a horizontal position error and a speed error of a relative landing point in the obstacle avoidance process of the spacecraft, and specifically comprises the following steps:
the phase plane is divided into an inner rectangular area and an outer Bang-Bang control area, the Bang-Bang control area is divided into a positive spray area and a negative spray area by two parabolas, and R+Is a forward full spray area controlled by Bang-Bang; r-Is a negative full spray area controlled by Bang-Bang; r0Is a PD control area, i.e. a rectangular area;
R+region and R-The division line of the region satisfies the relational expression
Lc＝-dLc|dLc|/(2·aref)
Wherein, arefThe reference acceleration on the horizontal axis is greater than the thrust acceleration generated by the translation engine of the lander; the position error of the relative landing point on the horizontal axis is LcAt a speed dLc(ii) a The horizontal axis refers to: an axis of the landing gear body in the nominal attitude parallel to the horizontal plane;
PD control area range | Lc|<LHmAnd | dLc|<dLHmWherein L isHmIs the position control error bound, dLHmIs the speed control error bound.
The control law determining module determines the control laws when the current horizontal position error and speed error data of the spacecraft are in different regions, and specifically comprises the following steps:
(a) when phase point, i.e. (L)c，dLc) At R of+In the area, the horizontal axis forward thruster outputs full pulse width, namely the forward thruster always jets air in the current control period;
(b) when the phase point is at R-In the region, the horizontal axis negative thruster outputsDischarging full pulse width; namely, the negative thruster always injects air in the current control period;
(c) when the phase point is at R0Region or once at R0In the area, the command thrust acceleration is calculated according to a PD control law, then the command thrust acceleration is modulated into the jet pulse width of the translation engine, and finally a positive thruster or a negative thruster is used for outputting according to the jet pulse width duration according to the direction of the jet pulse width;
the PD control law specifically comprises the following steps:
ac＝-kpsLc-kdsdLc
wherein k ispsIs the proportionality coefficient, kdsIs the differential coefficient, kpsAnd kdsThe parameter value is taken so that the bandwidth of the horizontal axis closed-loop system is 1 order of magnitude lower than the shaking frequency of the liquid in the storage tank, acIs an instruction acceleration;
the modulation is the jet pulse width of the translation engine, and specifically comprises the following steps:
(c1) calculating the ratio W of the command thrust to the actual thrust;
W＝|Y|/Fhwherein Y is the commanded thrust and Y ═ macLander mass m, FhIs the translational engine thrust on the horizontal axis;
(c2) determining an intermediate variable WcAnd PonA value of (d);
if W>1+HH2Then, then
Wc＝1；
Pon＝∞；
If 1+ HH2≥W>HH1Then, then
If W is not more than HH1Then, then
Wc＝0；
Pon＝tmin；
Wherein, tminIs minimum jet pulse width, HH1、HH2And TmThree design parameters for pulse width modulation;
(c3) calculating the remaining air injection time PWI: will PWI-WcΔ t sign (PWI) assigned to PWI;
the control period is delta t, sign is a sign function, 1 is output when the input is a positive number, minus 1 is output when the input is a negative number, 0 is output when the input is 0, and the initial value of PWI is 0;
(c4) calculating an air injection pulse width PW:
if | PWI | > Δ t, then
PW＝Δt·sign(PWI)；
If the | PWI | is less than or equal to delta t and the | PWI | phosphor<PonThen, then
PW＝0；
If the absolute PWI is less than or equal to delta t and the absolute PWI is more than or equal to PonThen, then
PW＝PWI；
PW is a signed parameter, the sign representing the direction of the jet and the magnitude representing the pulse width of the jet.
Compared with the prior art, the invention has the beneficial effects that:
(1) the influence of liquid shaking is considered, and the liquid shaking can be inhibited by adjusting PD control parameters; .
(2) And long-distance obstacle avoidance control adopts Bang-Bang control, so that the rapidity is improved. The method can improve the control effect of the surface tension storage tank lander translation control process, improve the rapidity and reduce the influence of liquid shaking on the posture.
Drawings
Fig. 1 is a phase plan view of an obstacle avoidance translational optimal control method.
FIG. 2 is a horizontal position and speed error time variation curve in the obstacle avoidance process.
Fig. 3 is a phase point motion trail diagram in the obstacle avoidance process.
Detailed Description
For the lander using the surface tension storage tank, the displacement control is implemented in the obstacle avoidance process, and a simple phase plane control method is used, so that the risk of exciting liquid to shake and finally causing attitude instability exists.
Aiming at the problem, the invention provides a novel translation control method with Bang-Bang control as an outer ring and PD control + pulse width modulation as an inner ring. PD control and pulse width modulation are adopted to generate an air injection control instruction with variable pulse width, and the parameter of a PD controller is adjusted to enable the bandwidth of a control system loop to be one order of magnitude lower than the natural frequency of liquid shaking, so that the liquid shaking is prevented from being excited by air injection control; a phase plane switch line is added outside the PD control to realize Bang-Bang control, and the problem that the response time of pure PD control is long when the large-range translation maneuvering control is carried out is solved. By combining and switching the inner ring and the outer ring by two methods, the problem of liquid shaking excited by translation control is solved, so that the attitude shaking angle in the translation process is reduced, the rapidity problem of long-distance translation is improved, and the optimal balance of obstacle avoidance control performance is achieved.
If the nominal flight attitude of the lander in the obstacle avoidance process keeps the longitudinal axis vertical to the ground, the axis of the lander body in the nominal attitude, which is parallel to the horizontal plane, is called a horizontal axis, and the number of the horizontal axes is two, then the horizontal position and the movement speed of the lander relative to the target landing point can be decomposed into the two horizontal axes of the lander body in the nominal attitude. Respectively controlling two horizontal axes, and setting the position error of a relative landing point on one horizontal axis as LcAt a speed dLcThen translation procedure (L)c，dLc) The phase plane is formed. The obstacle avoidance control method provided by the invention is based on the phase plane.
1) Phase plane area division
As shown in FIG. 1, the phase plane is divided into an inner rectangular area and an outer Bang-Bang control area, and the Bang-Bang control area is divided into two areas of positive and negative spray by two parabolas, so that R is used as the area in the figure+、R-And R0Three regions are shown. R+Is a forward full spray area controlled by Bang-Bang; r-Is a negative full spray area controlled by Bang-Bang; r0Is a PD control area.
R+Region and R-The division line of the region satisfies the relational expression
Lc＝-dLc|dLc|/(2·aref)
Wherein, arefThe reference acceleration on a single horizontal axis is generally a value slightly larger than the thrust acceleration which can be generated by the translation engine of the lander.
PD control area range | Lc|<LHmAnd | dLc|<dLHmWherein L isHmIs the position control error bound, dLHmIs the speed control error bound. These two parameters need to be determined according to the application object characteristic design.
2) Phase plane control law calculation
In each control period, calculating a jet instruction according to the horizontal position error and the speed error of the relative target landing point determined by the navigation system:
(a) when phase point, i.e. (L)c，dLc) At R of+In the area, the horizontal axis forward thruster outputs full pulse width, namely the forward thruster always jets air in the current control period;
(b) when the phase point is at R-In the area, the horizontal axis negative thruster outputs full pulse width, namely the negative thruster always jets air in the current control period;
(c) when relatively located at R0And when the area is in the area, the command thrust acceleration is calculated according to the PD control rate, then the command thrust acceleration is modulated into the jet pulse width of the translation engine, and finally a positive thruster or a negative thruster is used according to the direction of the jet pulse width and is output according to the jet pulse width duration.
PD control law is
ac＝-kpsLc-kdsdLc
Wherein k ispsIs the proportionality coefficient, kdsIs a differential coefficient, the value of which can be determined according to the designed natural frequency and damping ratio. The parameter is generally selected so that the bandwidth of the horizontal axis closed loop system is 1 order of magnitude lower than the tank liquid shaking frequency, acIs the commanded acceleration.
The function of the pulse width modulation is to convert the commanded acceleration into a thruster pulse width.
Assuming that the mass of the lander is m, then
Y＝-mac
W＝|Y|/Fh
Wherein, FhIs the axial translation engine thrust, W is the ratio of commanded thrust to actual thrust.
W>1+HH2Then, then
Wc＝1
Pon＝∞
1+ HH2≥W>HH1Then, then
W is not more than HH1Then, then
Wc＝0
Pon＝tmin
Wherein, tminIs the minimum jet pulse width, which is determined by the translational thruster performance. HH (Hilbert-Huang) with high hydrogen storage capacity1、HH2And TmAre three design parameters for pulse width modulation. WcAnd PonAre two intermediate variables.
Setting the residual air injection time of the previous period as PWI and the control period as delta t, then PWI-W is calculatedcΔ t sign (PWI) is assigned to PWI. sign is a sign function that outputs 1 when the input is a positive number, outputs-1 when the input is a negative number, and outputs 0 when the input is 0. The pulse width of the output jet is defined as PW.
If | PWI | > Δ t, then
PW＝Δt·sign(PWI)
If | PWI | is less than or equal to Δ t and | PWI | is non-luminous<PonThen, then
PW＝0
If | PWI | is less than or equal to Δ t and | PWI | is more than or equal to PonThen, then
PW＝PWI
PW is a signed parameter, the sign representing the direction of the jet and the magnitude representing the pulse width of the jet. The translation engine performs the jet according to PW.
(d) When the phase point once entered R0Region, even if phase point exceeds R again0Zone boundaries, i.e. | Lc|≥LHmOr | dLc|≥dLHmAnd calculating the jet control command by using the PD + pulse width modulation mode in the step c).
According to the method, the invention also provides an optimal obstacle avoidance system for inhibiting the liquid shaking time, which comprises the following steps: a region division module: the method is used for carrying out region division on a phase plane formed by horizontal position errors and speed errors of a relative landing point in the obstacle avoidance process of the spacecraft;
a control law determination module: the control law is used for determining the current horizontal position error and speed error data of the spacecraft when the data are in different regions;
keep away barrier control module: the method is used for calculating the air injection pulse width command according to the determined control law by the spacecraft, carrying out translational motion obstacle avoidance control and realizing the obstacle avoidance with optimal liquid shaking time inhibition.
Simulation analysis:
assuming that the mass m of the lander is 1954kg, the horizontal thrust Fh209N; reference acceleration a of Bang-Bang boundaryref＝1.1·Fh(ii)/m; PD control region boundary LHm＝2m、dLHm0.8 m/s; the parameters of the translation controller are designed according to the natural frequency of 0.2rad/s and the damping ratio of 1.2, namely kps＝0.04，kds0.48; modulation factor according to Tm＝4，HH1＝0.03，HH2Selecting as 0.02; control period Δ t of 0.128s, minimum jet width tmin＝0.04s。
Initial state is Lc＝-15m，dLcThe liquid shaking frequency in the translation process is between 2.483rad/s and 3.152rad/s, the position, speed and time change curve of the control method is shown in figure 2, and the phase plane motion trail is shown in figure 3. Can be seen to be in R before 0-12 s+The area outputs positive full jet gas, and the speed is continuously increased; then crosses the Bang-Bang boundary and enters R-In the region, negative full jet is output, and the speed is continuously reduced; entering the PD control region at about 17.5s, the position and velocity errors tend to be 0.
Claims (6)
1. An optimal obstacle avoidance method for inhibiting liquid shaking time is characterized by comprising the following implementation steps:
(1) carrying out region division on a phase plane formed by horizontal position errors and speed errors of a relative landing point in the obstacle avoidance process of the spacecraft;
(2) determining a control law when the current horizontal position error and speed error data of the spacecraft are in different regions;
(3) the spacecraft calculates an air injection pulse width command according to a determined control law, and performs translational obstacle avoidance control to realize obstacle avoidance with optimal liquid shaking inhibiting time;
the area division of the phase plane in the step (1) is specifically as follows:
the phase plane is divided into an inner rectangular area and an outer Bang-Bang control area, the Bang-Bang control area is divided into a positive spray area and a negative spray area by two parabolas, and R+Is a forward full spray area controlled by Bang-Bang; r-Is a negative full spray area controlled by Bang-Bang; r0Is a PD control area, i.e. a rectangular area;
R+region and R-The division line of the region satisfies the relational expression
Lc＝-dLc|dLc|/(2·aref)
Wherein, arefThe reference acceleration on the horizontal axis is greater than the thrust acceleration generated by the translation engine of the lander; the position error of the relative landing point on the horizontal axis is LcAt a speed dLc(ii) a The horizontal axis refers to: axis of the body of the lander parallel to the horizontal plane in the nominal attitude.
2. The optimal obstacle avoidance method for inhibiting liquid shaking time according to claim 1, wherein the optimal obstacle avoidance method comprises the following steps: PD control area range | Lc|<LHmAnd | dLc|<dLHmWherein L isHmIs the position control error bound, dLHmIs the speed control error bound.
3. The optimal obstacle avoidance method for inhibiting liquid shaking time according to claim 1, wherein the optimal obstacle avoidance method comprises the following steps: determining a control law when the current horizontal position error and speed error data of the spacecraft are in different regions, specifically:
(a) when phase point, i.e. (L)c，dLc) At R of+In the area, the horizontal axis forward thruster outputs full pulse width, namely the forward thruster always jets air in the current control period;
(b) when the phase point is at R-When the area is in, the horizontal axis negative thruster outputs full pulse width; namely, the negative thruster always injects air in the current control period;
(c) when the phase point is at R0Region or once at R0And in the area, calculating the command thrust acceleration according to a PD control law, modulating the command thrust acceleration into the jet pulse width of the translation engine, and finally outputting the command thrust acceleration according to the jet pulse width duration by using a positive thruster or a negative thruster according to the direction of the jet pulse width.
4. The optimal obstacle avoidance method for inhibiting liquid shaking time according to claim 3, wherein the optimal obstacle avoidance method comprises the following steps: the PD control law specifically comprises the following steps:
ac＝-kpsLc-kdsdLc
wherein k ispsIs the proportionality coefficient, kdsIs the differential coefficient, kpsAnd kdsThe parameter value is taken so that the bandwidth of the horizontal axis closed-loop system is 1 order of magnitude lower than the shaking frequency of the liquid in the storage tank, acIs the commanded acceleration.
5. The optimal obstacle avoidance method for inhibiting liquid shaking time according to claim 3, wherein the optimal obstacle avoidance method comprises the following steps: the modulation is the jet pulse width of the translation engine, and specifically comprises the following steps:
(c1) calculating the ratio W of the command thrust to the actual thrust;
W＝|Y|/Fhwherein Y is the commanded thrust and Y ═ macLander mass m, FhIs the translational engine thrust on the horizontal axis;
(c2) determining an intermediate variable WcAnd PonA value of (d);
if W>1+HH2Then, then
Wc＝1；
Pon＝∞；
If 1+ HH2≥W>HH1Then, then
If W is not more than HH1Then, then
Wc＝0；
Pon＝tmin；
Wherein, tminIs minimum jet pulse width, HH1、HH2And TmThree design parameters for pulse width modulation;
(c3) calculating the remaining air injection time PWI: will PWI-WcΔ t sign (PWI) assigned to PWI;
the control period is delta t, sign is a sign function, 1 is output when the input is a positive number, minus 1 is output when the input is a negative number, 0 is output when the input is 0, and the initial value of PWI is 0;
(c4) calculating an air injection pulse width PW:
if | PWI | > Δ t, then
PW＝Δt·sign(PWI)；
If the | PWI | is less than or equal to delta t and the | PWI | phosphor<PonThen, then
PW＝0；
If the absolute PWI is less than or equal to delta t and the absolute PWI is more than or equal to PonThen, then
PW＝PWI；
PW is a signed parameter, the sign representing the direction of the jet and the magnitude representing the pulse width of the jet.
6. An optimal obstacle avoidance system for inhibiting liquid shaking time is characterized by comprising:
a region division module: the method is used for carrying out region division on a phase plane formed by horizontal position errors and speed errors of a relative landing point in the obstacle avoidance process of the spacecraft;
a control law determination module: the control law is used for determining the current horizontal position error and speed error data of the spacecraft when the data are in different regions;
keep away barrier control module: the spacecraft is used for calculating an air injection pulse width command according to the determined control law, carrying out translational obstacle avoidance control and realizing obstacle avoidance with optimal liquid shaking time inhibition;
the area division module is used for carrying out area division on a phase plane formed by a horizontal position error and a speed error of a relative landing point in the obstacle avoidance process of the spacecraft, and specifically comprises the following steps:
the phase plane is divided into an inner rectangular area and an outer Bang-Bang control area, the Bang-Bang control area is divided into a positive spray area and a negative spray area by two parabolas, and R+Is a forward full spray area controlled by Bang-Bang; r-Is a negative full spray area controlled by Bang-Bang; r0Is a PD control area, i.e. a rectangular area;
R+region and R-The division line of the region satisfies the relational expression
Lc＝-dLc|dLc|/(2·aref)
Wherein, arefThe reference acceleration on the horizontal axis is greater than the thrust acceleration generated by the translation engine of the lander; the position error of the relative landing point on the horizontal axis is LcAt a speed dLc(ii) a The horizontal axis refers to: an axis of the landing gear body in the nominal attitude parallel to the horizontal plane;
PD control area range | Lc|<LHmAnd | dLc|<dLHmWherein L isHmIs the position control error bound, dLHmIs the speed control error bound;
the control law determining module determines the control laws when the current horizontal position error and speed error data of the spacecraft are in different regions, and specifically comprises the following steps:
(a) when phase point, i.e. (L)c，dLc) At R of+In the area, the horizontal axis forward thruster outputs full pulse width, namely the forward thruster always jets air in the current control period;
(b) when the phase point is at R-When the area is in, the horizontal axis negative thruster outputs full pulse width; namely, the negative thruster always injects air in the current control period;
(c) when the phase point is at R0Region or once at R0In the area, the command thrust acceleration is calculated according to a PD control law, then the command thrust acceleration is modulated into the jet pulse width of the translation engine, and finally a positive thruster or a negative thruster is used for outputting according to the jet pulse width duration according to the direction of the jet pulse width;
the PD control law specifically comprises the following steps:
ac＝-kpsLc-kdsdLc
wherein k ispsIs the proportionality coefficient, kdsIs the differential coefficient, kpsAnd kdsThe parameter value is taken so that the bandwidth of the horizontal axis closed-loop system is 1 order of magnitude lower than the shaking frequency of the liquid in the storage tank, acIs an instruction acceleration;
the modulation is the jet pulse width of the translation engine, and specifically comprises the following steps:
(c1) calculating the ratio W of the command thrust to the actual thrust;
W＝|Y|/Fhwherein Y is the commanded thrust and Y ═ macLander mass m, FhIs the translational engine thrust on the horizontal axis;
(c2) determining an intermediate variable WcAnd PonA value of (d);
if W>1+HH2Then, then
Wc＝1；
Pon＝∞；
If 1+ HH2≥W>HH1Then, then
If W is not more than HH1Then, then
Wc＝0；
Pon＝tmin；
Wherein, tminIs minimum jet pulse width, HH1、HH2And TmThree design parameters for pulse width modulation;
(c3) calculating the remaining air injection time PWI: will PWI-WcΔ t sign (PWI) assigned to PWI;
the control period is delta t, sign is a sign function, 1 is output when the input is a positive number, minus 1 is output when the input is a negative number, 0 is output when the input is 0, and the initial value of PWI is 0;
(c4) calculating an air injection pulse width PW:
if | PWI | > Δ t, then
PW＝Δt·sign(PWI)；
If the | PWI | is less than or equal to delta t and the | PWI | phosphor<PonThen, then
PW＝0；
If the absolute PWI is less than or equal to delta t and the absolute PWI is more than or equal to PonThen, then
PW＝PWI；
PW is a signed parameter, the sign representing the direction of the jet and the magnitude representing the pulse width of the jet.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
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