A method and system for calculating the suspension state of a manned lunar rover

Abstract

The present invention relates to a method and system for calculating the state of a suspension of a manned lunar rover, comprising: arranging an inertial measurement combination module at the center of mass of a manned lunar rover body, arranging an acceleration measurement module at the top of an independent suspension, arranging an acceleration measurement module at a wheel hub, measuring the vertical acceleration, pitch and roll angular velocity of the vehicle body, and measuring the vertical acceleration of the independent suspension and wheels; establishing vertical and angular motion differential equations of a seven-degree-of-freedom whole vehicle suspension system of the manned lunar rover; establishing a state equation of a seven-degree-of-freedom whole vehicle suspension system of the manned lunar rover according to the vertical and angular motion differential equations of the seven-degree-of-freedom whole vehicle suspension system and taking a suspension performance evaluation index as an output variable; establishing a suspension state observation model of the manned lunar rover; and performing calculations according to a Kalman prediction calculation method to obtain a suspension state quantity.

Description

Technical Field

[0001] The present invention relates to a method and system for calculating the state of a manned lunar rover suspension, which can be used for suspension control of a manned lunar rover and belongs to the technical field of manned lunar exploration. Background Art

[0002] As a complex multi-degree-of-freedom system with nonlinear, time-varying and time-delay characteristics, the manned lunar rover mobile system will cause the vehicle body to vibrate due to steering, acceleration and deceleration during driving. At the same time, the low gravity environment and the non-structural rugged lunar surface will aggravate the vibration effect. When the vibration reaches a certain level, it will affect the normal driving of the manned lunar rover, the fatigue life of the components, and directly affect the riding comfort, operational stability and safety of the astronauts in the vehicle. Unlike the unmanned lunar rover, the manned lunar rover uses an elastic active suspension system to connect the vehicle body and wheels as the main device to attenuate the vibration of the vehicle body. Therefore, the suspension performance directly determines the comprehensive performance of the manned lunar rover. In order to improve the handling stability and smoothness of the manned lunar rover, researchers have proposed controllers based on various control theories for its active suspension control. However, these theories are based on the complete and accurate measurement of suspension parameters. The vertical acceleration of the vehicle center of mass, the roll angle acceleration, the pitch angle acceleration, the suspension dynamic deflection and the dynamic load on the wheels are the main indicators of suspension performance. Therefore, real-time and accurate acquisition of the vehicle suspension state parameters is the premise for improving the control performance of the vehicle semi-active suspension.

[0003] Traditional suspension state calculation methods mainly use Kalman filter, improved Romberg prediction method, robust prediction method, sliding mode prediction method to calculate the state quantities such as vehicle speed and body posture of 1 / 4 suspension or 1 / 2 suspension model. In traditional suspension state calculation methods, they are mainly aimed at single road conditions in ground environment. There are few studies on vehicle longitudinal speed algorithms under complex road conditions, and the accuracy of vehicle suspension state estimation is not high. There is no research on suspension state calculation and ride comfort of manned lunar rover under low gravity environment and complex non-structure lunar surface.

[0004] In order to achieve the manned lunar rover's handling stability and ride comfort on the lunar surface, suspension state information is indispensable in the closed-loop control of the manned lunar rover's active suspension. Therefore, it is necessary to propose a suspension state calculation method based on multi-sensor measurement fusion and accurate mathematical modeling for the manned lunar rover, which can adapt to the complex working conditions on the lunar surface and meet the requirements of easy hardware implementation, guaranteed calculation accuracy and real-time performance. Summary of the invention

[0005] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art and provide a method for calculating the suspension state of a manned lunar rover, so as to further improve the ride comfort and stability control of the manned lunar rover.

[0006] The technical solution of the present invention is:

[0007] A method for calculating the suspension state of a manned lunar rover, comprising:

[0008] An inertial measurement unit module is arranged at the center of mass of the manned lunar rover, an acceleration measurement module is arranged at the top of the independent suspension, and an acceleration measurement module is arranged at the wheel hub to measure the vertical acceleration, pitch and roll angular velocity of the vehicle body, and the vertical acceleration of the independent suspension and wheels;

[0009] Establish the vertical and angular motion differential equations of the manned lunar rover's seven-degree-of-freedom vehicle suspension system;

[0010] According to the vertical and angular motion differential equations of the seven-degree-of-freedom vehicle suspension system, the state equation of the seven-degree-of-freedom vehicle suspension system of the manned lunar rover is established with the suspension performance evaluation index as the output variable;

[0011] Establish a manned lunar rover suspension state observation model;

[0012] The suspension state quantity is obtained by performing calculations according to the Kalman estimation method.

[0013] Furthermore, the vertical and angular motion differential equations of the seven-degree-of-freedom vehicle suspension system of the manned lunar rover are specifically:

[0014]

[0015] The vertical motion equation of the unsprung mass is:

[0016]

[0017] Among them, m and m u and unsprung mass, respectively; z and z u and the vertical displacement of the sprung and unsprung masses, respectively. and are the vertical velocities of the sprung and unsprung masses, is the vertical acceleration at the center of mass of the vehicle body; I x ,I y are the roll acceleration, pitch acceleration, and the moment of inertia of the X and Y axes respectively; k and c are the suspension spring stiffness and the non-adjustable damping coefficient respectively; k t is the tire stiffness; f is the adjustable damping force of the magnetorheological damper; q is the wheel-road excitation; d l ,d r ,d f ,d b are the distances from the center of mass to the left wheel, right wheel, front axle, and rear axle respectively;

[0018] The subscripts lf, rf, rr, and lr represent left front, right front, right rear, and left rear, respectively;

[0019] The displacement and velocity of the sprung mass are:

[0020]

[0021] Furthermore, the state equation of the seven-degree-of-freedom vehicle suspension system of the manned lunar rover is specifically:

[0022] x=[x1 x2 x3 x4 x5 x6 x7 x8 x9 x 10 x 11 x 12 x 13 x 14 x 15 ] T

[0023] State variables x1~x4 are the relative displacements of the left front, right front, right rear and left rear suspensions, state variables x5~x8 are the vertical displacements of the left front, right front, right rear and left rear wheels, state variables x9~x 12 is the vertical velocity of the left front, right front, right rear and left rear wheels, and the state variable x 13 ~x 15 is the vertical velocity, roll angular velocity and pitch angular velocity at the center of mass of the vehicle body, and we get:

[0024]

[0025] Among them, the state variable are the vertical velocities of the left front, right front, right rear and left rear suspensions, and the state variables is the vertical velocity of the left front, right front, right rear and left rear wheels, and the state variable is the vertical acceleration of the left front, right front, right rear and left rear wheels, and the state variable are the vertical acceleration, roll acceleration and pitch acceleration at the center of mass of the vehicle body, m f and m r are the vehicle masses carried by the front and rear suspensions, respectively, and k f and k r are the front and rear suspension spring stiffnesses, c f and c r are the damping coefficients of the front and rear suspensions, respectively;

[0026] The four adjustable damping forces of the suspension system are the input variables of the system, expressed as:

[0027] u=[f lf f rf frr f lr ] T

[0028] The four-wheel road excitation of the suspension system is the disturbance input of the system, which is expressed as:

[0029] w=[q lf q rf q rr q lr ] T

[0030] According to the performance evaluation index of the suspension system, the output variables of the system are selected as:

[0031]

[0032] Then its state equation, output equation and coefficient matrices are:

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

[0039] The coefficient of the lower right corner of the system state matrix A is:

[0040]

[0041] Furthermore, the manned lunar rover suspension state observation model is specifically:

[0042]

[0043] in, is the measured calculated value, V k is the measurement noise sequence, whose measurement noise power matrix is ​​determined by the characteristics of the sensor used; Z k is the observed quantity, which is composed of the vertical acceleration, pitch angular velocity, roll angular velocity at the center of mass of the vehicle body collected by the sensor, and the accelerations at the upper and lower ends of the four independent suspensions. lf 、a rf 、a rr and a lr are the accelerations of the upper ends of the left front, right front, right rear and left rear suspensions, respectively, a ulf 、aurf 、a urr and a ulr They are the accelerations of the upper ends of the left front, right front, right rear and left rear suspensions respectively. The nonlinear function h(x) represents the measurement calculation equations of 11 suspension states:

[0044]

[0045] Where, h(1), h(2) and h(3) are the vehicle body vertical acceleration, roll angular acceleration and pitch acceleration respectively; l a and l b are the distances from the center of mass to the front and rear axles, respectively, l c and l d are the distances from the center of mass to the left and right wheels respectively;

[0046] Using the Coriolis effect, we can find that the accelerations at the four corners of the vehicle body are related to the vertical acceleration of the center of mass, and the relationship is expressed as:

[0047] a i =a CG +ω×(ω×r i )+α×r i

[0048] In the formula, a CG is the vertical acceleration of the vehicle's center of mass, a CG +ω×(ω×r i )+α×r i is the rotational acceleration, r i is the feedback vector of each corner of the vehicle body in the vehicle body reference system, i = lf, rf, rr, lr; α and ω are the angular motion matrices, expressed as:

[0049]

[0050] Ignoring the yaw motion of the vehicle body, the vertical acceleration at the upper ends of the four shock absorbers connected to the vehicle body is calculated as:

[0051]

[0052] The vertical acceleration at the four wheel hubs is expressed as:

[0053]

[0054] Furthermore, the suspension state quantity is obtained by performing calculation according to the Kalman estimation method, which is specifically:

[0055] A priori estimation is made by applying the suspension state parameters of the previous moment and the vertical and angular motion differential equations of the seven-degree-of-freedom vehicle suspension system, and then the estimated state is updated through the signals collected by the inertial measurement combination module and the acceleration measurement module, and the accurate vehicle suspension state information is obtained by weighted calculation combined with the state information;

[0056] The suspension state parameters include: vertical acceleration, roll angle acceleration, and pitch angle acceleration;

[0057] The measurement update is expressed as:

[0058]

[0059] In the formula, is the suspension parameter calculation quantity, is the prior estimate of the suspension state, z k is the measured value of suspension parameters, h() is the measurement calculation equation of suspension state, K k is the Kalman gain matrix, expressed as:

[0060]

[0061] Where P k (-) is the prior estimated covariance matrix, R k is the measurement noise covariance matrix, H k is the Jacobian matrix of the prior estimate of the suspension state at time t = k, which can be obtained by Taylor series expansion

[0062]

[0063] In order to reduce the probability that the error covariance matrix is ​​negative, it is corrected by the following formula:

[0064]

[0065] Among them, I is the unit matrix;

[0066] Update on suspension status:

[0067]

[0068] Among them, u k is the control matrix, w k is Gaussian white noise, and the state transfer matrix Ф(k+1,k) in the above formula is an exponential matrix:

[0069] Φ(k+1,k)=exp(AΔT)

[0070] ΔT is the sensor sampling period;

[0071] Then input matrix B dIt is expressed as:

[0072]

[0073] The error covariance of the suspension state is updated as:

[0074] P k+1 (-)=Φ(k+1,k)P k (-)Φ(k+1,k) T +Q k

[0075] In the formula, Q k is the discrete process noise power, which is related to the continuous process white noise covariance matrix.

[0076] Furthermore, the present invention also proposes a manned lunar rover suspension state calculation system, comprising:

[0077] Parameter measurement module: an inertial measurement module is arranged at the center of mass of the manned lunar rover, an acceleration measurement module is arranged at the top of the independent suspension, and an acceleration measurement module is arranged at the wheel hub to measure the vertical acceleration, pitch and roll angular velocity of the vehicle body, and the vertical acceleration of the independent suspension and wheels;

[0078] Differential equation building module: Building vertical and angular motion differential equations of the manned lunar rover's seven-degree-of-freedom vehicle suspension system;

[0079] State equation establishment module: according to the vertical and angular motion differential equations of the seven-degree-of-freedom vehicle suspension system, the state equation of the seven-degree-of-freedom vehicle suspension system of the manned lunar rover is established with the suspension performance evaluation index as the output variable;

[0080] State observation model building module: building a state observation model for the manned lunar rover suspension;

[0081] Suspension state quantity calculation module: performs calculations according to the Kalman estimation method to obtain the suspension state quantity.

[0082] The beneficial effects of the present invention compared with the prior art are:

[0083] (1) The method for calculating the suspension state of a manned lunar rover proposed in the present invention establishes a seven-degree-of-freedom motion state equation for the active suspension of the manned lunar rover, which can accurately calculate the suspension state under the low gravity environment of the lunar surface and in complex unstructured terrain.

[0084] (2) The method for calculating the suspension state of a manned lunar rover proposed in the present invention has high real-time performance and can be further applied to the closed-loop control of the suspension of a manned lunar rover.

[0085] (3) The calculation method of the present invention measures the state information of the suspension vibration of the manned lunar rover through the configuration of the inertial measurement unit and the accelerometer, and uses it as the observation value of the active suspension system. On the basis of establishing the state equation of the seven-degree-of-freedom whole vehicle model system, the observation equation is established according to the suspension state variables, the mathematical relationship between the state variables and the suspension's own parameters, and the discrete extended Kalman filter algorithm is used to calculate the suspension state information, which can be used to further improve the ride comfort and stability control of the manned lunar rover. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 This is a flow chart of a method for calculating the suspension state of a manned lunar rover in an embodiment of the present invention;

[0087] Figure 2 This is a schematic diagram of a seven-degree-of-freedom whole vehicle suspension model of a manned lunar rover in an embodiment of the present invention;

[0088] Figure 3 This is a flow chart of the steps of the Kalman estimation calculation method in an embodiment of the present invention;

[0089] Figure 4 is a schematic diagram of the calculation result of the vertical acceleration of the vehicle body in an embodiment of the present invention;

[0090] Figure 5 Schematic diagram of calculation results of vehicle body roll angular velocity in an embodiment of the present invention;

[0091] Figure 6 Schematic diagram of the calculation result of the pitch angular velocity of the vehicle body in an embodiment of the present invention. DETAILED DESCRIPTION

[0092] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0093] The present invention provides a method for calculating the state of a manned lunar rover suspension. The method measures the state information of the manned lunar rover suspension vibration through an inertial measurement unit and an accelerometer configuration, and uses it as the observation value of the active suspension system. On the basis of establishing a seven-degree-of-freedom vehicle model system state equation, an observation equation is established according to the suspension state variable, the mathematical relationship between the state variable and the suspension's own parameters, and a discrete extended Kalman filter algorithm is used to calculate the suspension state information, which can be used to further improve the ride comfort and stability control of the manned lunar rover. The method of the present invention is described in detail below in conjunction with the accompanying drawings.

[0094] like Figure 1 As shown, the present invention proposes a method for calculating the suspension state of a manned lunar rover, comprising the following steps:

[0095] Step 1: Arrange an inertial measurement unit module at the center of mass of the manned lunar rover, an acceleration measurement module at the top of the independent suspension, and an acceleration measurement module at the wheel hub to measure the vertical acceleration, pitch and roll angular velocity of the vehicle body, and measure the vertical acceleration of the independent suspension and wheels;

[0096] Step 2: Establish the vertical and angular motion differential equations of the manned lunar rover's seven-degree-of-freedom vehicle suspension system:

[0097]

[0098] The vertical motion equation of the unsprung mass is:

[0099]

[0100] Among them, m and m u and unsprung mass, respectively; z and z u and the vertical displacement of the sprung and unsprung masses, respectively. and are the vertical velocities of the sprung and unsprung masses, is the vertical acceleration at the center of mass of the vehicle body; I x ,I y are the roll acceleration, pitch acceleration, and the moment of inertia of the X and Y axes respectively; k and c are the suspension spring stiffness and the non-adjustable damping coefficient respectively; k t is the tire stiffness; f is the adjustable damping force of the magnetorheological damper; q is the wheel-road excitation; d l ,d r ,d f ,d b are the distances from the center of mass to the left wheel, right wheel, front axle, and rear axle respectively;

[0101] The subscripts lf, rf, rr, and lr represent left front, right front, right rear, and left rear, respectively;

[0102] Considering the roll angle of the suspension of the manned lunar rover under normal circumstances The variation range of the pitch angle θ is relatively small, so the displacement and velocity of the sprung mass are:

[0103]

[0104] Step 3: Based on the suspension dynamics motion differential equations established in step 2, the suspension performance evaluation index is used as the output variable to establish the state equation of the manned lunar rover's seven-degree-of-freedom vehicle suspension system:

[0105] x=[x1 x2 x3 x4 x5 x6 x7 x8 x9 x 10 x11 x 12 x 13 x 14 x 15 ] T

[0106] State variables x1~x4 are the relative displacements of the left front, right front, right rear and left rear suspensions, state variables x5~x8 are the vertical displacements of the left front, right front, right rear and left rear wheels, state variables x9~x 12 is the vertical velocity of the left front, right front, right rear and left rear wheels, and the state variable x 13 ~x 15 are the vertical velocity, roll angular velocity and pitch angular velocity at the center of mass of the vehicle body.

[0107] available:

[0108]

[0109] Among them, the state variable are the vertical velocities of the left front, right front, right rear and left rear suspensions, and the state variables is the vertical velocity of the left front, right front, right rear and left rear wheels, and the state variable is the vertical acceleration of the left front, right front, right rear and left rear wheels, and the state variable are the vertical acceleration, roll acceleration and pitch acceleration at the center of mass of the vehicle body, m f and m r are the vehicle masses carried by the front and rear suspensions, respectively, and k f and k r are the front and rear suspension spring stiffnesses, c f and c r are the damping coefficients of the front and rear suspensions, respectively;

[0110] The four adjustable damping forces of the suspension system are the input variables of the system and can be expressed as:

[0111] u=[f lf f rf f rr f lr ] T

[0112] The four-wheel road excitation of the suspension system is the disturbance input of the system, which can be expressed as:

[0113] w=[q lf q rf q rr q lr ] T

[0114] According to the performance evaluation index of the suspension system, the output variables of the system are selected as:

[0115]

[0116] Then its state equation, output equation and coefficient matrices are:

[0117]

[0118]

[0119]

[0120]

[0121]

[0122]

[0123] The coefficient of the lower right corner of the system state matrix A is:

[0124]

[0125] Step 4: Establish the manned lunar rover suspension state observation model:

[0126]

[0127] in, is the measured calculated value, V k is the measurement noise sequence, whose measurement noise power matrix is ​​determined by the characteristics of the sensor used; Z k is the observed quantity, which is composed of the vertical acceleration, pitch angular velocity, roll angular velocity at the center of mass of the vehicle body collected by the sensor, and the accelerations at the upper and lower ends of the four independent suspensions. lf 、a rf 、a rr and a lr are the accelerations of the upper ends of the left front, right front, right rear and left rear suspensions, respectively, a ulf 、a urf 、a urr and a ulr They are the accelerations of the upper ends of the left front, right front, right rear and left rear suspensions respectively. The nonlinear function h(x) represents the measurement calculation equations of 11 suspension states:

[0128]

[0129] Where, h(1), h(2) and h(3) are the vehicle body vertical acceleration, roll angular acceleration and pitch acceleration respectively; l a and l bare the distances from the center of mass to the front and rear axles, respectively, l c and l d are the distances from the center of mass to the left and right wheels respectively.

[0130] By applying the Coriolis effect, we can find that the acceleration at the four corners of the vehicle body is related to the vertical acceleration of the center of mass, and the relationship can be expressed as:

[0131] a i =a CG +ω×(ω×r i )+α×r i

[0132] In the formula, a CG is the vertical acceleration of the vehicle's center of mass, a CG +ω×(ω×r i )+α×r i is the rotational acceleration, r i is the feedback vector of each corner of the vehicle body in the vehicle body reference system, i = lf, rf, rr, lr; α and ω are the angular motion matrices, expressed as:

[0133]

[0134] Ignoring the yaw motion of the vehicle body, the vertical acceleration at the upper ends of the four shock absorbers connected to the vehicle body is calculated as:

[0135]

[0136] The vertical acceleration at the four wheel hubs is expressed as:

[0137]

[0138] Step 5: Use Taylor series expansion to omit high-order terms in the nonlinear part of the suspension state and measurement equation to obtain the discrete state and measurement equation, and then perform calculations according to the classic Kalman estimation method to obtain the suspension state quantity:

[0139] The suspension state parameters of the previous moment and the vertical and angular motion differential equations of the seven-degree-of-freedom vehicle suspension system are used to make a priori estimates, and then the estimated state is updated through the signals collected by the inertial measurement combination module and the acceleration measurement module, and the state information is combined for weighted calculation to obtain accurate vehicle suspension state information. The measurement update is expressed as:

[0140]

[0141] In the formula, is the suspension parameter calculation quantity, is the prior estimate of the suspension state, z kis the measured value of suspension parameters, h() is the measurement calculation equation of suspension state, K k is the Kalman gain matrix, which can be expressed as:

[0142]

[0143] Where P k (-) is the prior estimated covariance matrix, R k is the measurement noise covariance matrix, H k is the Jacobian matrix of the prior estimate of the suspension state at time t = k, which can be obtained by Taylor series expansion

[0144]

[0145] In order to reduce the probability that the error covariance matrix is ​​negative, it is corrected by the following formula:

[0146]

[0147] Among them, I is the unit matrix;

[0148] Update on suspension status:

[0149]

[0150] Among them, u k is the control matrix, w k is Gaussian white noise, and the state transfer matrix Ф(k+1,k) in the above formula is an exponential matrix:

[0151] Φ(k+1,k)=exp(AΔT)

[0152] ΔT is the sensor sampling period;

[0153] Then input matrix B d It is expressed as:

[0154]

[0155] The error covariance of the suspension state is updated as:

[0156] P k+1 (-)=Φ(k+1,k)P k (-)Φ(k+1,k) T +Q k

[0157] In the formula, Q k is the discrete process noise power, which is related to the continuous process white noise covariance matrix.

[0158] The present invention also proposes a manned lunar rover suspension state calculation system, comprising:

[0159] Parameter measurement module: an inertial measurement module is arranged at the center of mass of the manned lunar rover, an acceleration measurement module is arranged at the top of the independent suspension, and an acceleration measurement module is arranged at the wheel hub to measure the vertical acceleration, pitch and roll angular velocity of the vehicle body, and the vertical acceleration of the independent suspension and wheels;

[0160] Differential equation building module: Building vertical and angular motion differential equations of the manned lunar rover's seven-degree-of-freedom vehicle suspension system;

[0161] State equation establishment module: according to the vertical and angular motion differential equations of the seven-degree-of-freedom vehicle suspension system, the state equation of the seven-degree-of-freedom vehicle suspension system of the manned lunar rover is established with the suspension performance evaluation index as the output variable;

[0162] State observation model building module: building a state observation model for the manned lunar rover suspension;

[0163] Suspension state quantity calculation module: performs calculations according to the Kalman estimation method to obtain the suspension state quantity.

[0164] Example:

[0165] Reference Figure 1 , shows a flow chart of the steps of a method for calculating the suspension state of a manned lunar rover in an embodiment of the present invention. In an embodiment of the present invention, the method for calculating the suspension state of a manned lunar rover includes:

[0166] In step S1, the inertial measurement module and the acceleration measurement module measure the acceleration and angular velocity of the vehicle body as well as the acceleration of the suspension and wheels.

[0167] In this embodiment, an inertial measurement combination module is arranged at the center of mass of the manned lunar rover body to measure the angular motion velocity of the vehicle body and the acceleration along the coordinate axis in the carrier coordinate system. Acceleration measurement modules are arranged at the upper and lower ends of the four independent suspensions to measure the motion states of the vehicle suspension and unsprung mass, respectively.

[0168] Step S2, establishing vertical and angular motion differential equations of the manned lunar rover's seven-degree-of-freedom vehicle suspension system.

[0169] To facilitate modeling, the manned lunar rover model needs to be simplified: 1) The wheel hub, axle, and frame are rigidly connected. 2) The wheels are treated as elastic elements and are always in contact with the road surface. 3) The vehicle suspension and wheels are treated as springs with a certain stiffness. 4) The vehicle body is always perpendicular to the road surface.

[0170] The vehicle suspension model includes seven degrees of freedom: vertical motion of the vehicle body, pitch motion of the vehicle body, roll motion of the vehicle body and vertical motion of the four wheels. The seven-degree-of-freedom suspension model can be found in Figure 2The differential equations for the vertical, roll and pitch motions of the vehicle body are:

[0171]

[0172] The vertical motion equation of the unsprung mass is:

[0173]

[0174] Among them, m, m u and are the sprung and unsprung masses, respectively; z is the vertical displacement at the center of mass of the vehicle body; z, z u are the vertical displacements of the sprung and unsprung masses, respectively; θ、I x ,I y are the roll angle, pitch angle, X-axis and Y-axis moments of inertia respectively; k and c are the suspension spring stiffness and the non-adjustable damping coefficient respectively; k t is the tire stiffness; f is the adjustable damping force of the magnetorheological damper; q is the wheel-road excitation; d l ,d r ,d f ,d b are the distances from the center of mass to the left wheel, right wheel, front axle, and rear axle, respectively. The subscripts lf, rf, rr, and lr represent the left front, right front, right rear, and left rear, respectively.

[0175] Considering the roll angle of the suspension of the manned lunar rover under normal circumstances The variation range of the pitch angle θ is relatively small, so the displacement and velocity of the sprung mass are:

[0176]

[0177] Substituting equation (3) into equation (1) and equation (2), we can obtain the equation group of the manned lunar rover suspension model:

[0178]

[0179]

[0180] Step S3, establishing the state equation of the seven-degree-of-freedom whole-vehicle suspension system of the manned lunar rover.

[0181] According to the suspension model, the suspension dynamics motion differential equations expressed by equations (4) and (5), the suspension state parameters that affect ride comfort and handling stability are selected as the state variables of the system to establish the state equation of the suspension system, and the suspension performance evaluation index is used as the output variable to establish the output equation.

[0182] The state equation of the seven-degree-of-freedom suspension system of the manned lunar rover is established as:

[0183] x=[x1 x2 x3 x4 x5 x6 x7 x8 x9 x 10 x 11 x 12 x 13 x 14 x 15 ] T (6)

[0184] Among them, the state variables x1~x4 are the relative displacements of the left front, right front, right rear and left rear suspensions, and the state variables x5~x 12 is the vertical displacement and velocity of the left front, right front, right rear and left rear wheels, and the state variable x 13 ~x 15 is the vertical velocity, roll angular velocity and pitch angular velocity at the center of mass of the vehicle body, we can get:

[0185]

[0186] The four adjustable damping forces of the suspension system are the input variables of the system and can be expressed as:

[0187] u=[f lf f rf f rr f lr ] T (7)

[0188] The four-wheel road excitation of the suspension system is the disturbance input of the system, which can be expressed as:

[0189] w=[q lf q rf q rr q lr ] T (8)

[0190] According to the performance evaluation index of the suspension system, the output variables of the system are selected as:

[0191]

[0192] Then its state equation, output equation and coefficient matrices are:

[0193]

[0194]

[0195]

[0196]

[0197]

[0198]

[0199] The coefficient of the lower right corner of the system state matrix A is:

[0200]

[0201] Step S4, establishing a manned lunar rover suspension state observation model:

[0202]

[0203] in, is the measured calculated value, V k is the measurement noise sequence, whose measurement noise power matrix is ​​determined by the characteristics of the sensor used; Z k is the observed quantity, which is composed of the vertical acceleration, pitch angular velocity, roll angular velocity at the center of mass of the vehicle body collected by the sensor, and the accelerations at the upper and lower ends of the four independent suspensions. lf 、a rf 、a rr and a lr are the accelerations of the upper ends of the left front, right front, right rear and left rear suspensions, respectively, a ulf 、a urf 、a urr and a ulr They are the accelerations of the upper ends of the left front, right front, right rear and left rear suspensions respectively. The nonlinear function h(x) represents the measurement calculation equations of 11 suspension states:

[0204]

[0205] Where, h(1), h(2) and h(3) are the vehicle body vertical acceleration, roll angular acceleration and pitch acceleration respectively; l a and l b are the distances from the center of mass to the front and rear axles, respectively, l c and l d are the distances from the center of mass to the left and right wheels respectively.

[0206] By applying the Coriolis effect, we can find that the acceleration at the four corners of the vehicle body is related to the vertical acceleration of the center of mass, and the relationship can be expressed as:

[0207] a i =a CG +ω×(ω×r i )+α×r i

[0208] In the formula, a CG is the vertical acceleration of the vehicle's center of mass, a CG +ω×(ω×r i )+α×r iis the rotational acceleration, r i is the feedback vector of each corner of the vehicle body in the vehicle body reference system, i = lf, rf, rr, lr; α and ω are the angular motion matrices, expressed as:

[0209]

[0210] Ignoring the yaw motion of the vehicle body, the vertical acceleration at the upper ends of the four shock absorbers connected to the vehicle body is calculated as:

[0211]

[0212] The vertical acceleration at the four wheel hubs is expressed as:

[0213]

[0214] Step S5, performing calculations using the Kalman prediction method to obtain the suspension state quantity.

[0215] Refer to the manned lunar rover suspension model parameters to set the model parameters, as shown in the following table:

[0216]

[0217]

[0218] The parameters in the above table are substituted into the suspension state equation in step S4 as input. The road surface excitation uses filtered white noise random road surface input to generate the road surface roughness time profile. The established road surface excitation model is used. The simulation experiment conditions are set to a medium vehicle speed of 5km / h and the road surface grade is set to B. The nonlinear part in the suspension state and measurement equations is expanded by Taylor series to omit the high-order terms to obtain the discrete state and measurement equations, and then the calculation is performed according to the classic Kalman prediction calculation method. The steps of the Kalman prediction algorithm are shown in Figure 3 , the algorithm predicts and estimates the state of the manned lunar rover suspension, including the dynamic parameters of the vehicle body in the vertical pitch and roll directions, the suspension vibration parameters, and the vibration parameters of the wheels, see Figures 4 to 6 .

[0219] The following table shows the root mean square error between the calculated values ​​and reference values ​​of various state parameters of the manned lunar rover suspension.

[0220] Suspension status parameters Root mean square error Vertical acceleration of vehicle 0.0683 Vehicle roll angle velocity 0.0577 Vehicle pitch angular velocity 0.0701

[0221] The root mean square error between the calculated value and the reference value of each state parameter in the above table is very small, indicating that the calculated value deviates little from the true value and the algorithm has high accuracy. This verifies that the present invention can be applied to the calculation of the state parameters of the active suspension of a manned lunar rover, and can realize real-time and effective calculation of the suspension state of a manned lunar rover, and can be further applied to the closed-loop control of the suspension of a manned lunar rover.

[0222] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A method for calculating the suspension state of a manned lunar rover, characterized in that include: An inertial measurement unit module is arranged at the center of mass of the manned lunar rover, an acceleration measurement module is arranged at the top of the independent suspension, and an acceleration measurement module is arranged at the wheel hub to measure the vertical acceleration, pitch and roll angular velocity of the vehicle body, and the vertical acceleration of the independent suspension and wheels; The vertical and angular motion differential equations of the manned lunar rover's seven-degree-of-freedom vehicle suspension system are established, specifically: The vertical motion equation of the unsprung mass is: Among them, m and m u and unsprung mass, respectively; z and z u and the vertical displacement of the sprung and unsprung masses, respectively. and are the vertical velocities of the sprung and unsprung masses, is the vertical acceleration at the center of mass of the vehicle body; I x ,I y are the roll acceleration, pitch acceleration, and the moment of inertia of the X and Y axes respectively; k and c are the suspension spring stiffness and the non-adjustable damping coefficient respectively; k t is the tire stiffness; f is the adjustable damping force of the magnetorheological damper; q is the wheel-road excitation; d l d r d f d b are the distances from the center of mass to the left wheel, right wheel, front axle, and rear axle respectively; The subscripts lf, rf, rr, and lr represent left front, right front, right rear, and left rear, respectively; The displacement and velocity of the sprung mass are: According to the vertical and angular motion differential equations of the seven-degree-of-freedom vehicle suspension system, the state equation of the seven-degree-of-freedom vehicle suspension system of the manned lunar rover is established with the suspension performance evaluation index as the output variable, which is specifically: x=[x1 x2 x3 x4 x5 x6 x7 x8 x9 x 10 x 11 x 12 x 13 x 14 x 15 ] T State variables x1~x4 are the relative displacements of the left front, right front, right rear and left rear suspensions, state variables x5~x8 are the vertical displacements of the left front, right front, right rear and left rear wheels, state variables x9~x 12 is the vertical velocity of the left front, right front, right rear and left rear wheels, and the state variable x 13 ~x 15 is the vertical velocity, roll angular velocity and pitch angular velocity at the center of mass of the vehicle body, and we get: Among them, the state variable are the vertical velocities of the left front, right front, right rear and left rear suspensions, and the state variables is the vertical velocity of the left front, right front, right rear and left rear wheels, and the state variable is the vertical acceleration of the left front, right front, right rear and left rear wheels, and the state variable are the vertical acceleration, roll acceleration and pitch acceleration at the center of mass of the vehicle body, m f and m r are the vehicle masses carried by the front and rear suspensions, respectively, and k f and k r are the front and rear suspension spring stiffnesses, c f and c r are the damping coefficients of the front and rear suspensions, respectively; The four adjustable damping forces of the suspension system are the input variables of the system, expressed as: u=[f lf f rf f rr f lr ] T The four-wheel road excitation of the suspension system is the disturbance input of the system, which is expressed as: w=[q lf q rf q rr q lr ] T According to the performance evaluation index of the suspension system, the output variables of the system are selected as: Then its state equation, output equation and coefficient matrices are: The coefficient of the lower right corner of the system state matrix A is: Establish a manned lunar rover suspension state observation model, specifically: in, is the measured calculated value, V k is the measurement noise sequence, whose measurement noise power matrix is ​​determined by the characteristics of the sensor used; Z k is the observed quantity, which is composed of the vertical acceleration, pitch angular velocity, roll angular velocity at the center of mass of the vehicle body collected by the sensor, and the accelerations at the upper and lower ends of the four independent suspensions. lf 、a rf 、a rr and a lr are the accelerations of the upper ends of the left front, right front, right rear and left rear suspensions, respectively, a ulf 、a urf 、a urr and a ulr They are the accelerations of the upper ends of the left front, right front, right rear and left rear suspensions respectively. The nonlinear function h(x) represents the measurement calculation equations of 11 suspension states: Where, h(1), h(2) and h(3) are the vehicle body vertical acceleration, roll angular acceleration and pitch acceleration respectively; l a and l b are the distances from the center of mass to the front and rear axles, l c and l d are the distances from the center of mass to the left and right wheels respectively; Using the Coriolis effect, we can find that the accelerations at the four corners of the vehicle body are related to the vertical acceleration of the center of mass, and the relationship is expressed as: a i =a CG +ω×(ω×r i )+α×r i In the formula, a CG is the vertical acceleration of the vehicle's center of mass, a CG +ω×(ω×r i )+α×r i is the rotational acceleration, ri is the feedback vector of each angle of the vehicle body in the vehicle body reference system, i = lf, rf, rr, lr; α and ω are the angular motion matrices, expressed as: Ignoring the yaw motion of the vehicle body, the vertical acceleration at the upper ends of the four shock absorbers connected to the vehicle body is calculated as: The vertical acceleration at the four wheel hubs is expressed as: The suspension state quantity is obtained by performing calculations according to the Kalman estimation method.

2. A method for calculating the suspension state of a manned lunar rover according to claim 1, characterized in that: The suspension state quantity is obtained by performing calculation according to the Kalman estimation method, which is specifically: A priori estimation is made by applying the suspension state parameters of the previous moment and the vertical and angular motion differential equations of the seven-degree-of-freedom vehicle suspension system, and then the estimated state is updated through the signals collected by the inertial measurement combination module and the acceleration measurement module, and the accurate vehicle suspension state information is obtained by weighted calculation combined with the state information; The suspension state parameters include: vertical acceleration, roll angle acceleration, and pitch angle acceleration; The measurement update is expressed as: In the formula, is the suspension parameter calculation quantity, is the prior estimate of the suspension state, z k is the measured value of suspension parameters, h( ) is the measurement calculation equation of suspension state, K k is the Kalman gain matrix, expressed as: Where P k (-) is the prior estimated covariance matrix, R k is the measurement noise covariance matrix, H k is the Jacobian matrix of the prior estimate of the suspension state at time t = k, which can be obtained by Taylor series expansion In order to reduce the probability that the error covariance matrix is ​​negative, it is corrected by the following formula: Among them, I is the unit matrix; Update on suspension status: Among them, u k is the control matrix, w k is Gaussian white noise, and the state transfer matrix Ф(k+1,k) in the above formula is an exponential matrix: Φ(k+1,k)=exp(AΔT) ΔT is the sensor sampling period; Then input matrix B d It is expressed as: The error covariance of the suspension state is updated as: P k+1 (-)=Φ(k+1,k)P k (-)Φ(k+1,k) T +Q k In the formula, Q k is the discrete process noise power, which is related to the continuous process white noise covariance matrix.

3. A manned lunar rover suspension state calculation system, characterized in that include: Parameter measurement module: an inertial measurement module is arranged at the center of mass of the manned lunar rover, an acceleration measurement module is arranged at the top of the independent suspension, and an acceleration measurement module is arranged at the wheel hub to measure the vertical acceleration, pitch and roll angular velocity of the vehicle body, and the vertical acceleration of the independent suspension and wheels; Differential equation building module: Establish the vertical and angular motion differential equations of the manned lunar rover's seven-degree-of-freedom vehicle suspension system, specifically: The vertical motion equation of the unsprung mass is: Among them, m and m u and unsprung mass, respectively; z and z u and the vertical displacement of the sprung and unsprung masses, respectively. and are the vertical velocities of the sprung and unsprung masses, is the vertical acceleration at the center of mass of the vehicle body; I x ,I y are the roll acceleration, pitch acceleration, and the moment of inertia of the X and Y axes respectively; k and c are the suspension spring stiffness and the non-adjustable damping coefficient respectively; k t is the tire stiffness; f is the adjustable damping force of the magnetorheological damper; q is the wheel-road excitation; d l d r d f d b are the distances from the center of mass to the left wheel, right wheel, front axle, and rear axle respectively; The subscripts lf, rf, rr, and lr represent left front, right front, right rear, and left rear, respectively; The displacement and velocity of the sprung mass are: State equation establishment module: According to the vertical and angular motion differential equations of the seven-degree-of-freedom vehicle suspension system, the state equation of the seven-degree-of-freedom vehicle suspension system of the manned lunar rover is established with the suspension performance evaluation index as the output variable, which is specifically: x=[x1 x2 x3 x4 x5 x6 x7 x8 x9 x 10 x 11 x 12 x 13 x 14 x 15 ] T State variables x1~x4 are the relative displacements of the left front, right front, right rear and left rear suspensions, state variables x5~x8 are the vertical displacements of the left front, right front, right rear and left rear wheels, state variables x9~x 12 is the vertical velocity of the left front, right front, right rear and left rear wheels, and the state variable x 13 ~x 15 is the vertical velocity, roll angular velocity and pitch angular velocity at the center of mass of the vehicle body, and we get: Among them, the state variable are the vertical velocities of the left front, right front, right rear and left rear suspensions, and the state variables is the vertical velocity of the left front, right front, right rear and left rear wheels, and the state variable is the vertical acceleration of the left front, right front, right rear and left rear wheels, and the state variable are the vertical acceleration, roll acceleration and pitch acceleration at the center of mass of the vehicle body, m f and m r are the vehicle masses carried by the front and rear suspensions, respectively, and k f and k r are the front and rear suspension spring stiffnesses, c f and c r are the damping coefficients of the front and rear suspensions, respectively; The four adjustable damping forces of the suspension system are the input variables of the system, expressed as: u=[f lf f rf f rr f lr ] T The four-wheel road excitation of the suspension system is the disturbance input of the system, which is expressed as: w=[q lf q rf q rr q lr ] T According to the performance evaluation index of the suspension system, the output variables of the system are selected as: Then its state equation, output equation and coefficient matrices are: The coefficient of the lower right corner of the system state matrix A is: State observation model building module: Establish the state observation model of the manned lunar rover suspension, specifically: in, is the measured calculated value, V k is the measurement noise sequence, whose measurement noise power matrix is ​​determined by the characteristics of the sensor used; Z k is the observed quantity, which is composed of the vertical acceleration, pitch angular velocity, roll angular velocity at the center of mass of the vehicle body collected by the sensor, and the accelerations at the upper and lower ends of the four independent suspensions. lf 、a rf 、a rr and a lr are the accelerations of the upper ends of the left front, right front, right rear and left rear suspensions, respectively, a ulf 、a urf 、a urr and a ulr They are the accelerations of the upper ends of the left front, right front, right rear and left rear suspensions respectively. The nonlinear function h(x) represents the measurement calculation equations of 11 suspension states: Where, h(1), h(2) and h(3) are the vehicle body vertical acceleration, roll angular acceleration and pitch acceleration respectively; l a and l b are the distances from the center of mass to the front and rear axles, l c and l d are the distances from the center of mass to the left and right wheels respectively; Using the Coriolis effect, we can find that the accelerations at the four corners of the vehicle body are related to the vertical acceleration of the center of mass, and the relationship is expressed as: a i =a CG +ω×(ω×r i )+α×r i In the formula, a CG is the vertical acceleration of the vehicle's center of mass, a CG +ω×(ω×r i )+α×r i is the rotational acceleration, ri is the feedback vector of each angle of the vehicle body in the vehicle body reference system, i = lf, rf, rr, lr; α and ω are the angular motion matrices, expressed as: Ignoring the yaw motion of the vehicle body, the vertical acceleration at the upper ends of the four shock absorbers connected to the vehicle body is calculated as: The vertical acceleration at the four wheel hubs is expressed as: Suspension state quantity calculation module: performs calculations according to the Kalman estimation method to obtain the suspension state quantity.

4. The manned lunar rover suspension state calculation system according to claim 3, characterized in that: The suspension state quantity is obtained by performing calculation according to the Kalman estimation method, which is specifically: A priori estimation is made by applying the suspension state parameters of the previous moment and the vertical and angular motion differential equations of the seven-degree-of-freedom vehicle suspension system, and then the estimated state is updated through the signals collected by the inertial measurement combination module and the acceleration measurement module, and the accurate vehicle suspension state information is obtained by weighted calculation combined with the state information; The suspension state parameters include: vertical acceleration, roll angle acceleration, and pitch angle acceleration; The measurement update is expressed as: In the formula, is the suspension parameter calculation quantity, is the prior estimate of the suspension state, z k is the measured value of suspension parameters, h( ) is the measurement calculation equation of suspension state, K k is the Kalman gain matrix, expressed as: Where P k (-) is the prior estimated covariance matrix, R k is the measurement noise covariance matrix, H k is the Jacobian matrix of the prior estimate of the suspension state at time t = k, which can be obtained by Taylor series expansion In order to reduce the probability that the error covariance matrix is ​​negative, it is corrected by the following formula: Among them, I is the unit matrix; Update on suspension status: Among them, u k is the control matrix, w k is Gaussian white noise, and the state transfer matrix Ф(k+1,k) in the above formula is an exponential matrix: Φ(k+1,k)=exp(AΔT) ΔT is the sensor sampling period; Then input matrix B d It is expressed as: The error covariance of the suspension state is updated as: P k+1 (-)=Φ(k+1,k)P k (-)Φ(k+1,k) T +Q k In the formula, Q k is the discrete process noise power, which is related to the continuous process white noise covariance matrix.

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