Disclosure of Invention
The invention aims to provide an xPC Target-based real-time platform, which realizes real-time communication between a shock absorber solenoid valve and a man-vehicle-road closed-loop digital simulation model and a DCC controller, and the running state of the shock absorber solenoid valve is controlled by the DCC controller.
In order to solve the technical problems, the invention provides a hardware-in-loop simulation test bed of an automobile dynamic chassis control system, which comprises a host machine, a target machine, a monitor, an I/O data conversion module, a network interface card, a USBCAN interface card, a BDM downloader, a DCC controller, a damper solenoid valve and a current sampling module, wherein the host machine is provided with a man-vehicle-road closed-loop digital simulation model based on a Matlab/Simulink platform, the man-vehicle-road closed-loop digital simulation model is converted into an executable C code through an RTW compiling module and downloaded into a CPU of the target machine, the DCC controller is communicated with the target machine through the I/O data conversion module, the DCC controller acquires man-vehicle-road closed-loop digital model data in the target machine in real time, the output of the DCC controller controls the damper solenoid valve, and the current acquisition module acquires a control current signal of the damper solenoid valve in real time, feeding back to the target machine through an I/O data conversion module to form a closed loop; and the simulation test bed evaluates the control effects under different working conditions and different modes, and gives a corresponding evaluation result after each simulation is finished.
The invention provides a vehicle longitudinal-lateral-vertical dynamics unified modeling idea, which is used for building a human-vehicle-road closed loop digital simulation model on a host machine based on a Matlab/Simulink platform, so that the built dynamic model is representative, and the mathematical theory analysis and simulation modeling of a vehicle longitudinal-lateral-vertical dynamics nonlinear model are realized on the basis of analyzing the behavior characteristics of complex nonlinear dynamics coupled by multiple vehicle systems, and the method comprises the following steps: 1) modeling assumptions; 2) modeling a power transmission system; 3) modeling a vehicle body; 4) modeling a suspension; 5) modeling a tire; 6) modeling of the driver.
1) Modeling assumptions:
generally, the higher the complexity of the model or the more degrees of freedom, the higher the simulation accuracy, but the numerical computation amount will increase and affect the real-time performance of the simulation. Therefore, taking into account the necessary vehicle dynamics coupling factors, it is necessary to make corresponding assumptions simplifications. Coupling factors that must be considered during vehicle motion are:
the vehicle yaw motion caused by the steering of the wheels is coupled with each other kinematically and dynamically;
the interaction between the tire and the road surface is not negligible, the distribution of its longitudinal and lateral tire forces being affected by the traction ellipses;
the coupling exists between the longitudinal-lateral-vertical motion of the vehicle, the vertical load transfer of the vehicle can be caused by the longitudinal and lateral acceleration motion of the vehicle, so that the vertical dynamics of the vehicle is influenced, and the adhesion characteristic and the lateral deviation characteristic of the tire can be influenced by the change of the vertical load, so that the braking performance and the operation stability of the whole vehicle are influenced.
To simplify the modeling process, the following assumptions are made on the basis of fully considering vehicle coupling and strong non-linearity:
1. simplifying the modeling process of the power transmission system; 2. neglecting the influence of asymmetric wheel alignment parameters, and assuming that the center distance and the wheel distance of the suspension are equal; 3. assuming that the roll center and the pitch center are both located on the vehicle longitudinal bisecting plane and the roll axis is located above the pitch axis; 4. neglecting the roll and pitch motions of the unsprung mass; 5. it is assumed that the unsprung mass and the sprung mass are resiliently connected in the vertical direction and rigidly connected in the horizontal direction.
2) Modeling a power transmission system:
in order to comprehensively represent the unstable state process of the engine in the actual working process of the vehicle, a first-order inertia link with a hysteresis characteristic is added on the basis of the stable output characteristic of the engine to obtain the dynamic torque characteristic of the engine, namely:
in the formula (I), the compound is shown in the specification,
in order to output the torque dynamically from the engine,
hair with indicationSteady state torque characteristic function of engine, which is engine speed
And throttle opening degree
Is a function of the non-linear function of (c),
is a time constant, taken here
。
The dynamic relation between the output torque and the output rotating speed of the engine is as follows:
in the formula (I), the compound is shown in the specification,
effective rotational inertia of the rotating part of the engine and the clutch part;
is the engine rotational angular acceleration;
outputting torque for an engine flywheel;
to input torque to the clutch.
The vehicle under study was equipped with a dual clutch automatic transmission, and the engine output torque was considered equal to the transmission input torque, i.e., the input torque of the transmission, regardless of the engagement/disengagement process of the dual clutches during the modeling process
In the formula (I), the compound is shown in the specification,
effective rotational inertia of a rotating part of a transmission and a transmission shaft at a certain gear;
and
transmitting angular acceleration and angular velocity for a certain gear of the transmission;
total drive torque for the wheels;
is the transmission speed ratio;
the speed ratio of the main speed reducer is obtained;
for the transmission efficiency of the transmission system;
is the wheel angular velocity.
Total drive torque
Is simultaneously applied to two front wheels
The wheel rotation dynamics equation is as follows:
in the formula (I), the compound is shown in the specification,
equivalent moment of inertia for the wheel;
and
the angular velocity and the angular acceleration of the wheel are respectively;
is the tire longitudinal force;
is the effective radius of the tire;
and
driving torque and braking torque of the wheels respectively;
the wheel rotation damping coefficient;
corresponding to the left front, right front, left rear and right rear wheels, respectively.
3) Vehicle body modeling
The vehicle body comprises a sprung mass and an unsprung mass, and the longitudinal-lateral-vertical unified dynamic model of the vehicle is established based on Lagrangian analytical mechanics.
Vehicle coordinate system
Origin of (2)
And center of pitch
Center of coincidence, roll
Relative to
Satisfy the requirement of
And (4) relationship. Sprung mass coordinate system
Origin of (2)
Coinciding with the sprung mass centre of mass, the unsprung mass mainly corresponds to four unsprung masses. Inertial frame
Vehicle coordinate system
And sprung mass coordinate system
Can be converted into each other. If directional cosine matrix is used
Representing the above-mentioned coordinate rotation transformation, i.e.
The conversion relationship between the inertial, vehicle and sprung mass coordinate systems is:
according to the foregoing definition and analysis, the body portion contains a total of 6 degrees of freedom, namely 3 degrees of freedom in the longitudinal, lateral and yaw shared by the unsprung mass and the sprung mass, and 3 degrees of freedom in the roll, pitch and vertical directions shared by the sprung mass. The translational and rotational angular velocities of the sprung and unsprung masses are separately determined and the respective kinetic and potential energies are then represented.
According to the coordinate conversion relation, the sprung mass center of mass (the origin of the sprung mass coordinate system)
) Relative to the inertial coordinate system
Absolute position vector of point
And absolute velocity vector
Respectively as follows:
in the formula (I), the compound is shown in the specification,
is in an inertial coordinate system
Dot relative to
A position vector of the point;
as in the vehicle coordinate system
Dot relative to
The position vector of the point, expressed as:
in the formula (I), the compound is shown in the specification,
as vectors
A component of (a);
is composed of
Relative to each other
Vertical distance;
is composed of
Relative to each other
The vertical distance is set according to the distance,
。
under the inertial coordinate system
The translational velocity of the point, i.e.
Noting the angular velocity of the sprung mass about its own reference axis as
Then, then
The kinetic energy of the sprung mass comprises both translational and rotational parts of the sprung mass, namely:
in the formula (I), the compound is shown in the specification,
is the sprung mass;
for sprung mass about its centre of mass
The inertia tensor, taking into account the sprung mass about
Plane symmetry, then
Comprises the following steps:
in the formula (I), the compound is shown in the specification,
is the center of mass of sprung mass
The moment of inertia or the product of inertia.
Substituting the formulas (10), (11) and (13) for the formula (12) to obtain the sprung mass kinetic energy
:
Similarly, the unsprung mass kinetic energy is composed of the translation and rotation of the unsprung mass and the runout of four wheels, namely:
the total kinetic energy being sprung mass kinetic energy
And unsprung mass kinetic energy
To sum, i.e.
。
The potential energy of the vehicle body comprises gravitational potential energy generated by height change of the sprung mass
In the formula (I), the compound is shown in the specification,
vertical displacement from sprung mass centre to unsprung mass centre;
for sprung mass at its equilibrium point position
The value of (c).
The total kinetic energy, potential energy and dissipation energy of the vehicle body are introduced into a Lagrange equation, and then partial derivatives of the total kinetic energy, potential energy and dissipation energy are solved, so that a motion equation of the vehicle body can be obtained, wherein the Lagrange equation of the vehicle body is as follows:
in the formula (I), the compound is shown in the specification,
is a generalized coordinate under an inertial coordinate system;
is a generalized force in an inertial coordinate system.
In general, the motion of the vehicle is used to be described in the vehicle coordinate system, and the following relationship is used to convert the generalized variable in the formula (18) into the generalized variable in the vehicle coordinate system.
In the formula (I), the compound is shown in the specification,
generalized coordinates under a vehicle coordinate system;
is a generalized force in a vehicle coordinate system.
So far, a kinetic equation of the six-degree-of-freedom vehicle body model is obtained
In the formula (I), the compound is shown in the specification,
,
and
in the form of a matrix of coefficients,
generalized coordinates under a vehicle coordinate system;
is a generalized force in a vehicle coordinate system.
If the air resistance is to be neglected,
primarily from ground tire forces and suspension forces,
expressed as:
in the formula (I), the compound is shown in the specification,
in the form of a matrix of coefficients,
in the tire coordinate system for four wheels
And
directional tire forces, derived from a tire model;
suspension forces for four wheels were obtained from the suspension model.
The motion of the vehicle under the inertial coordinate system is obtained through the following kinematic relationship:
in the formula (I), the compound is shown in the specification,
,
for the whole vehicle
Longitudinal, lateral speed of the shaft;
,
vehicle edge
Longitudinal, lateral speed of the shaft;
is the yaw angle of the vehicle.
4) Suspension modeling:
the purpose of the suspension model is here to find the suspension forces and the vertical loads of the wheels and to give the vertical equations of motion of the unsprung mass. The suspension force includes the elastic force of the elastic member, the damping force of the damping member, and the vertical acting force of the stabilizer bar, and the suspension force corresponding to each wheel is expressed as
In the formula (I), the compound is shown in the specification,
is the stiffness coefficient of the elastic element;
is a damping force of the shock absorber, which is controlled by a control current
Relative speed of motion of damper
(ii) related;
a vertical acting force generated for the transverse stabilizer bar;
vertical displacement for four wheels;
vertical displacement of sprung mass and four suspension contacts, from vehicle pitch angle
Side inclination angle
And calculating the geometrical parameters of the vehicle.
Damping force of the shock absorber
The relationship between the control current and the relative movement speed of the damper is shown in FIGS. 4-5.
The contact force between the wheel and the ground is
In the formula (I), the compound is shown in the specification,
the contact force between the four wheels and the ground is the dynamic load of the wheels moving vertically;
respectively the stiffness coefficient of each wheel,
and inputting the road surface corresponding to the four wheels.
Under the action of suspension force and contact force between the wheel and the ground, the vertical motion equation of the unsprung mass is
The vertical load of the wheel being constituted by the static normal force, the longitudinal load transfer, the lateral load transfer and the dynamic load of the tyre, i.e.
In the formula (I), the compound is shown in the specification,
vertical load for four wheels;
the vertical loads of four wheels under the static state of the vehicle;
and
the vertical load variation of the wheels caused by the longitudinal load transfer and the lateral load transfer of the vehicle respectively;
is the tire dynamic load of four wheels.
5) Tire modeling:
the tire model is a mathematical relationship description between six component forces of the tire and the wheel motion parameters. The invention uses MF tyre model to obtain the generalized force acting on the vehicle body in the form of
Easily known, tire force
Load perpendicular to wheel
Longitudinal slip ratio
Tire slip angle
Road surface adhesion coefficient
And camber angle of the wheel
It is related.
6) Modeling a driver:
during simulation, the speed and the driving direction of the vehicle dynamic model need to be controlled so as to ensure that the speed and the driving track of the vehicle conform to expected values. The speed control being PID control, i.e.
In the formula (I), the compound is shown in the specification,
setting the vehicle speed;
the actual vehicle speed;
is a desired acceleration; control parameter
,
,
。
The driving direction control of the vehicle dynamic model adopts an optimal curvature driver model, and the relationship between the characteristic parameters of the driver and the parameters of the vehicle model is established according to the operating characteristics of the driver.
The system comprises an I/O data conversion module, a DCC controller and a CAN bus, wherein the I/O data conversion module comprises an I/O data conversion card and a CAN conversion card, the I/O data conversion card converts various dynamic parameter signals of the vehicle obtained by calculation of a target computer from digital quantity to analog quantity, a vehicle height sensor signal and a vehicle vertical acceleration sensor signal are directly sent to the DCC controller, and the rest signals are packaged into CAN data by the CAN conversion card and sent to the network interface card and then transmitted to the DCC controller through the CAN bus; the I/O data conversion card simultaneously converts the analog quantity output by the current sampling module into digital quantity to be sent to the target machine to form a closed loop.
The monitoring machine monitors and collects data on the CAN bus in real time through the CAN conversion card, and performs post-processing and analysis on the data.
The DCC controller comprises an MC9S12XDP512 minimum system, a signal input module and an output driving module, wherein the MC9S12XDP512 minimum system comprises a power module, a clock circuit, a reset circuit and a BDM interface circuit, the signal input module comprises a filter circuit module, a voltage division circuit module and a CAN signal receiving and transmitting circuit module, and the output driving module comprises a PWM module, an electromagnetic valve driving circuit module and a current feedback circuit module; the input signals of the DCC controller comprise a vehicle height sensor signal, an acceleration sensor signal, a DCC mode selection signal and a CAN signal; in the simulation process of the DCC system, the change of the damping force of each shock absorber and the change of the control current of the shock absorber are given, the control strategy is verified in real time, and the control parameters are adjusted until a satisfactory control effect is obtained.
The electromagnetic valves of the shock absorber comprise four proportional electromagnetic valves, PWM and I/O ports output by a control chip are adopted for control, and the duty ratio of the PWM is changed to control the opening degree of a valve core of the proportional electromagnetic valves, so that the damping force output by the shock absorber is changed.
The current sampling module comprises a high-precision sampling resistor, a high-impedance amplifier and a filter circuit, the high-precision sampling resistor is connected in series in a driving circuit of the proportional solenoid valve, the high-impedance amplifier amplifies the voltage at two ends of the sampling resistor, the voltage is filtered by the filter circuit and then input into the I/O data conversion card, and the current working current of the proportional solenoid valve is fed back.
The network interface card is a multi-node CAN communication card, and CAN signal transmission from the CAN conversion card to the DCC controller and the USBCAN interface card is realized.
And the USBCAN interface card collects data on the CAN bus in real time and sends the data to the monitor.
The invention has the following advantages:
1) hardware of a controller and an actuator of the dynamic chassis control system is in a loop, and prediction results of various control strategies are more definite;
2) in the early development stage of a controller of a dynamic chassis control system, a hardware-in-the-loop simulation test bed is adopted, and various control parameters, particularly control parameters under extreme dangerous working conditions, can be optimized;
3) the smoothness of a vehicle with the assembled dynamic chassis control system, the anti-roll stability of the curve working condition, the pitching attitude control of the starting working condition, the tire adhesion characteristic and the transverse stability under the emergency working condition can be tested;
4) the test environment is simplified, and various performances obtained by testing and the obtained optimized parameters are closer to those of the real vehicle test;
5) the vehicle running state is simulated by the real-time processing platform running simulation model, comprehensive and systematic testing is carried out on the automobile dynamic chassis control system hardware, the number of real vehicle road test testing times is reduced, the risk of test faults is effectively reduced, the development time is shortened, and the cost is reduced.
Detailed Description
The embodiments of the invention will be described in detail below with reference to the drawings, but the invention can be implemented in many different ways as defined and covered by the claims.
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
Fig. 1 shows a schematic block diagram of an embodiment of the invention. As shown in figure 1, the invention provides a hardware-in-the-loop simulation test bed for an automobile dynamic chassis control system, which comprises a host machine 1, a target machine 2, a monitor 3, an I/O data conversion card 4, a CAN conversion card 5, a network interface card 6, a USBCAN interface card 7, a BDM downloader 8, a DCC controller 9, a shock absorber solenoid valve 10 and a current sampling module 11. On a host machine 1, a man-car-road closed-loop digital simulation model is built based on a Matlab/Simulink platform, the man-car-road closed-loop digital simulation model is converted into executable C codes through an RTW compiling module and downloaded to a CPU of a target machine 2 through an Ethernet, a DCC controller 9 keeps communication with the target machine 2 through an I/O data conversion card 4, man-car-road closed-loop digital model information in the target machine is collected in real time, four shock absorber electromagnetic valves 10 are controlled, a current collecting module 9 collects control current signals of the four shock absorber electromagnetic valves in real time and feeds the control current signals back to the target machine 2 through the I/O data conversion card 4, and a closed-loop is formed. LabVIEW graphical data acquisition software is installed on the monitor 3, data on a CAN bus is monitored and acquired in real time through the CAN conversion card 5, and post-processing and analysis are carried out on the data. The software code inside the DCC controller may be written on host 1 or other PC and sintered into the DCC controller 9 through BDM 8.
Based on the software and hardware composition, the hardware-in-loop simulation test bed of the automobile dynamic chassis control system controlled by the DCC controller is established.
As shown in fig. 2, the host 1 is a PC installed with Matlab/Simulink and Visual C + + target language compiler software environment, and a man-car-road closed-loop digital simulation model is established on the host 1 and can be converted into an executable C code by an RTW compiling module.
In order to make the established dynamics model representative, the invention provides a unified modeling idea of vehicle longitudinal-lateral-vertical dynamics, which realizes mathematical theory analysis and simulation modeling of the vehicle longitudinal-lateral-vertical dynamics nonlinear model on the basis of analyzing the behavior characteristics of complex nonlinear dynamics coupled by multiple systems of a vehicle, and comprises the following steps: 1) modeling assumptions; 2) modeling a power transmission system; 3) modeling a vehicle body; 4) modeling a suspension; 5) modeling a tire; 6) modeling of the driver.
1) Modeling assumptions:
generally, the higher the complexity of the model or the more degrees of freedom, the higher the simulation accuracy, but the numerical computation amount will increase and affect the real-time performance of the simulation. Therefore, taking into account the necessary vehicle dynamics coupling factors, it is necessary to make corresponding assumptions simplifications. Coupling factors that must be considered during vehicle motion are:
1. the vehicle yaw motion caused by the steering of the wheels is coupled with each other kinematically and dynamically; 2. the interaction between the tire and the road surface is not negligible, the distribution of its longitudinal and lateral tire forces being affected by the traction ellipses; 3. the coupling exists between the longitudinal-lateral-vertical motion of the vehicle, the vertical load transfer of the vehicle can be caused by the longitudinal and lateral acceleration motion of the vehicle, so that the vertical dynamics of the vehicle is influenced, and the adhesion characteristic and the lateral deviation characteristic of the tire can be influenced by the change of the vertical load, so that the braking performance and the operation stability of the whole vehicle are influenced.
To simplify the modeling process, the following assumptions are made on the basis of fully considering vehicle coupling and strong non-linearity:
1. simplifying the modeling process of the power transmission system; 2. neglecting the influence of asymmetric wheel alignment parameters, and assuming that the center distance and the wheel distance of the suspension are equal; 3. assuming that the roll center and the pitch center are both located on the vehicle longitudinal bisecting plane and the roll axis is located above the pitch axis; 4. neglecting the roll and pitch motions of the unsprung mass; 5. it is assumed that the unsprung mass and the sprung mass are resiliently connected in the vertical direction and rigidly connected in the horizontal direction.
2) Modeling a power transmission system:
in order to comprehensively represent the unstable state process of the engine in the actual working process of the vehicle, a first-order inertia link with a hysteresis characteristic is added on the basis of the stable output characteristic of the engine to obtain the dynamic torque characteristic of the engine, namely:
in the formula (I), the compound is shown in the specification,
in order to output the torque dynamically from the engine,
representing the steady-state torque characteristic function of the engine, which is the engine speed
And throttle opening degree
Is a function of the non-linear function of (c),
is a time constant, taken here
。
The dynamic relation between the output torque and the output rotating speed of the engine is as follows:
in the formula (I), the compound is shown in the specification,
effective rotational inertia of the rotating part of the engine and the clutch part;
is the engine rotational angular acceleration;
outputting torque for an engine flywheel;
to input torque to the clutch.
The vehicle under study was equipped with a dual clutch automatic transmission, and the engine output torque was considered equal to the transmission input torque, i.e., the input torque of the transmission, regardless of the engagement/disengagement process of the dual clutches during the modeling process
In the formula (I), the compound is shown in the specification,
effective rotational inertia of a rotating part of a transmission and a transmission shaft at a certain gear;
and
transmitting angular acceleration and angular velocity for a certain gear of the transmission;
total drive torque for the wheels;
is the transmission speed ratio;
the speed ratio of the main speed reducer is obtained;
for the transmission efficiency of the transmission system;
is the wheel angular velocity.
Total drive torque
Is simultaneously applied to two front wheels
The wheel rotation dynamics equation is as follows:
in the formula (I), the compound is shown in the specification,
equivalent moment of inertia for the wheel;
and
the angular velocity and the angular acceleration of the wheel are respectively;
is the tire longitudinal force;
is the effective radius of the tire;
and
driving torque and braking torque of the wheels respectively;
the wheel rotation damping coefficient;
corresponding to the left front, right front, left rear and right rear wheels, respectively.
3) Vehicle body modeling
The vehicle body comprises a sprung mass and an unsprung mass, and the longitudinal-lateral-vertical unified dynamic model of the vehicle is established based on Lagrangian analytical mechanics.
Vehicle coordinate system
Origin of (2)
And center of pitch
Center of coincidence, roll
Relative to
Satisfy the requirement of
And (4) relationship. Sprung mass coordinate system
Origin of (2)
Coinciding with the sprung mass centre of mass, the unsprung mass mainly corresponds to four unsprung masses. Inertial frame
Vehicle coordinate system
And sprung mass coordinate system
Can be converted into each other. If directional cosine matrix is used
Representing the above-mentioned coordinate rotation transformation, i.e.
The conversion relationship between the inertial, vehicle and sprung mass coordinate systems is:
according to the foregoing definition and analysis, the body portion contains a total of 6 degrees of freedom, namely 3 degrees of freedom in the longitudinal, lateral and yaw shared by the unsprung mass and the sprung mass, and 3 degrees of freedom in the roll, pitch and vertical directions shared by the sprung mass. The translational and rotational angular velocities of the sprung and unsprung masses are separately determined and the respective kinetic and potential energies are then represented.
According to the coordinate conversion relation, the sprung mass center of mass (the origin of the sprung mass coordinate system)
) Relative to the inertial coordinate system
Absolute position vector of point
And absolute velocity vector
Respectively as follows:
in the formula (I), the compound is shown in the specification,
is in an inertial coordinate system
Dot relative to
A position vector of the point;
as in the vehicle coordinate system
Dot relative to
The position vector of the point, expressed as:
in the formula (I), the compound is shown in the specification,
as vectors
A component of (a);
is composed of
Relative to each other
Vertical distance;
is composed of
Relative to each other
The vertical distance is set according to the distance,
。
under the inertial coordinate system
The translational velocity of the point, i.e.
Noting the angular velocity of the sprung mass about its own reference axis as
Then, then
The kinetic energy of the sprung mass comprises both translational and rotational parts of the sprung mass, namely:
in the formula (I), the compound is shown in the specification,
is the sprung mass;
for sprung mass about its centre of mass
The inertia tensor, taking into account the sprung mass about
Plane symmetry, then
Comprises the following steps:
in the formula (I), the compound is shown in the specification,
is the center of mass of sprung mass
The moment of inertia or the product of inertia.
Substituting the formulas (10), (11) and (13) for the formula (12) to obtain the sprung mass kinetic energy
:
Similarly, the unsprung mass kinetic energy is composed of the translation and rotation of the unsprung mass and the runout of four wheels, namely:
the total kinetic energy being sprung mass kinetic energy
And unsprung mass kinetic energy
To sum, i.e.
。
The potential energy of the vehicle body comprises gravitational potential energy generated by height change of the sprung mass
In the formula (I), the compound is shown in the specification,
vertical displacement from sprung mass centre to unsprung mass centre;
for sprung mass at its equilibrium point position
The value of (c).
The total kinetic energy, potential energy and dissipation energy of the vehicle body are introduced into a Lagrange equation, and then partial derivatives of the total kinetic energy, potential energy and dissipation energy are solved, so that a motion equation of the vehicle body can be obtained, wherein the Lagrange equation of the vehicle body is as follows:
in the formula (I), the compound is shown in the specification,
is a generalized coordinate under an inertial coordinate system;
is a generalized force in an inertial coordinate system.
In general, the motion of the vehicle is used to be described in the vehicle coordinate system, and the following relationship is used to convert the generalized variable in the formula (18) into the generalized variable in the vehicle coordinate system.
In the formula (I), the compound is shown in the specification,
generalized coordinates under a vehicle coordinate system;
is a generalized force in a vehicle coordinate system.
So far, a kinetic equation of the six-degree-of-freedom vehicle body model is obtained
In the formula (I), the compound is shown in the specification,
,
and
in the form of a matrix of coefficients,
generalized coordinates under a vehicle coordinate system;
is a generalized force in a vehicle coordinate system.
If the air resistance is to be neglected,
primarily from ground tire forces and suspension forces,
expressed as:
in the formula (I), the compound is shown in the specification,
in the form of a matrix of coefficients,
in the tire coordinate system for four wheels
And
directional tire forces, derived from a tire model;
suspension forces for four wheels were obtained from the suspension model.
The motion of the vehicle under the inertial coordinate system is obtained through the following kinematic relationship:
in the formula (I), the compound is shown in the specification,
,
for the whole vehicle
Longitudinal, lateral speed of the shaft;
,
vehicle edge
Longitudinal, lateral speed of the shaft;
is the yaw angle of the vehicle.
4) Suspension modeling:
the purpose of the suspension model is here to find the suspension forces and the vertical loads of the wheels and to give the vertical equations of motion of the unsprung mass. The suspension force includes the elastic force of the elastic member, the damping force of the damping member, and the vertical acting force of the stabilizer bar, and the suspension force corresponding to each wheel is expressed as
In the formula (I), the compound is shown in the specification,
is the stiffness coefficient of the elastic element;
is a damping force of the shock absorber, which is controlled by a control current
Relative speed of motion of damper
(ii) related;
a vertical acting force generated for the transverse stabilizer bar;
vertical displacement for four wheels;
vertical displacement of sprung mass and four suspension contacts, from vehicle pitch angle
Side inclination angle
And calculating the geometrical parameters of the vehicle.
Damping force of the shock absorber
The relationship between the control current and the relative movement speed of the damper is shown in FIGS. 4-5.
The contact force between the wheel and the ground is
In the formula (I), the compound is shown in the specification,
the contact force between the four wheels and the ground is the dynamic load of the wheels moving vertically;
respectively the stiffness coefficient of each wheel,
and inputting the road surface corresponding to the four wheels.
Under the action of suspension force and contact force between the wheel and the ground, the vertical motion equation of the unsprung mass is
The vertical load of the wheel being constituted by the static normal force, the longitudinal load transfer, the lateral load transfer and the dynamic load of the tyre, i.e.
In the formula (I), the compound is shown in the specification,
vertical load for four wheels;
the vertical loads of four wheels under the static state of the vehicle;
and
the vertical load variation of the wheels caused by the longitudinal load transfer and the lateral load transfer of the vehicle respectively;
is the tire dynamic load of four wheels.
5) Tire modeling:
the tire model is a mathematical relationship description between six component forces of the tire and the wheel motion parameters. The invention uses MF tyre model to obtain the generalized force acting on the vehicle body in the form of
Easily known, tire force
Load perpendicular to wheel
Longitudinal slip ratio
Tire slip angle
Road surface adhesion coefficient
And camber angle of the wheel
It is related.
6) Modeling a driver:
during simulation, the speed and the driving direction of the vehicle dynamic model need to be controlled so as to ensure that the speed and the driving track of the vehicle conform to expected values. The speed control being PID control, i.e.
In the formula (I), the compound is shown in the specification,
setting the vehicle speed;
the actual vehicle speed;
is a desired acceleration; control parameter
,
,
。
The driving direction control of the vehicle dynamic model adopts an optimal curvature driver model, and the relationship between the characteristic parameters of the driver and the parameters of the vehicle model is established according to the operating characteristics of the driver.
The target machine 2 is a 610H industrial personal computer and realizes the communication between the target machine 2 and the DCC controller 9 through a data conversion module.
The data conversion module comprises an I/O data conversion card 4 (PCL-818L and PCL-726) and a CAN conversion card 5. The I/O data conversion card 4 converts various dynamic parameter signals of the vehicle calculated by the target computer 2 from digital quantity to analog quantity, wherein the vehicle height sensor signal and the vehicle vertical acceleration sensor signal are directly received by the DCC controller 9, and the rest signals are packaged into CAN messages by the CAN conversion card 5 and sent to the network interface card 6 and then transmitted to the DCC controller 9 through the CAN bus. The I/O data conversion card 4 simultaneously converts the analog quantity output by the current sampling module 11 into digital quantity for receiving by the target machine 2, thereby forming a closed loop.
The circuit principle of the CAN conversion card 5 is shown in figure 6, according to the input requirement of a signal acquisition module of a DCC controller 9, the CAN conversion card is designed by taking a Freescale Feishakall 8-bit control chip as a core, and various dynamic parameter signals of a vehicle output by the I/O data conversion card 4 are converted into CAN messages to be sent to a network interface card 6 for the DCC controller 9 and a USBCAN interface card 7 to receive.
The circuit principle of the DCC controller 9 is shown in FIG. 7, and the invention develops and designs the DCC controller by itself with a Freescale 16-bit control chip MC9S12XDP512 as a core according to the characteristics of a DCC system, wherein input signals of the DCC controller comprise a vehicle body height sensor signal, an acceleration sensor signal, a DCC mode selection signal and a CAN signal. The DCC controller includes an MC9S12XDP512 minimum system, a signal input module, and an output driver module. The MC9S12XDP512 minimum system comprises a power module, a clock circuit, a reset circuit, a BDM interface circuit and the like; the signal input module comprises a filter circuit module, a voltage division circuit module and a CAN signal transceiving circuit module; the output driving module comprises a PWM module, an electromagnetic valve driving circuit module and a current feedback circuit module.
The damper solenoid valve 10 includes four proportional solenoid valves, and is controlled by PWM and I/O ports output by a control chip. The valve core opening degree of the proportional solenoid valve can be realized by using BTS5090 of Infineon (England flying) as a driving chip and controlling through an I/O port and changing the duty ratio of PWM, so that the damping force output by the shock absorber is changed.
The current sampling module 11 is shown in fig. 8 and includes a high-precision sampling resistor, a high-impedance amplifier, and a filter circuit. A high-precision sampling resistor is connected in series in a proportional solenoid valve driving circuit, voltages at two ends of the sampling resistor are amplified by using a high-impedance differential amplifier, and high-frequency noise in signals is reduced through an RC (resistor-capacitor) filter circuit. And finally, inputting the filtered signal into an I/O data conversion board card 4 of the host machine 1, so that the current working current of the proportional solenoid valve can be determined.
The network interface card 6 is a multi-node CAN communication card to realize CAN signal transmission from the CAN conversion card 5 to the DCC controller 9 and the USBCAN interface card 7.
The USBCAN interface card 7 is a ZLG USBCAN-II intelligent CAN interface card and is used for collecting messages on a CAN bus in real time.
The monitoring machine 3 is a PC machine provided with LabVIEW graphical data acquisition software, is connected with the network interface card 6 through the USBCAN interface card 7, acquires the interactive information of the target machine 2 and the DCC controller 9 in real time, monitors abnormal data in the test process, and stores the data so as to carry out post-processing and analysis.
The BDM8 is used for sintering control codes written on the host machine 1 or other PC machines into the DCC controller 9, so as to realize the read-write and erase operations of the microprocessor Flash, facilitate the online tracking and debugging of the operation of the control codes and improve the development efficiency of the controller.
Through the steps, a hardware-in-loop simulation test bed of the dynamic chassis control system is established, and the hardware-in-loop simulation test bed can run and evaluate the control parameters of the electric control unit. The man-vehicle-road closed-loop system model runs in the target machine 2, the DCC controller 9 controls the working state of the electromagnetic valve 10 according to vehicle information given by the target machine 2 in real time, such as height sensor signals, acceleration sensor signals, DCC mode selection signals, CAN signals and the like, the circuit acquisition module 9 feeds back the current of the corresponding shock absorber to the CPU of the target machine 2 through the data board card, and the monitoring machine 3 judges test results in real time through the USBCAN interface card 7.
As shown in fig. 9, which is a working flow chart of the present invention, the hardware-in-loop simulation test bed can evaluate the control effect under different working conditions and different modes, and each simulation can give a corresponding result for evaluation. In the simulation process of the DCC system, the change of the damping force of each shock absorber, the change of the control current of the shock absorber and the like can be comprehensively given, so that the control strategy is verified in real time, and the control parameters are adjusted until a satisfactory control effect is obtained.
In addition, the hardware-in-the-loop simulation test bed can also realize the optimized matching of parameters of each component of a vehicle chassis, a tire and a transmission system, can realize the debugging of control parameters of the vehicle under the extreme dangerous working condition, and can detect and debug the circuit fault of the designed electronic control unit 3.
Due to the fact that hardware of the DCC controller 9 and the shock absorber electromagnetic valve is in a ring, various tested performances and obtained optimized parameters are close to those of a real vehicle test, the times of the real vehicle test are obviously reduced, the development period is shortened, and meanwhile a large amount of development cost is saved.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.