Vehicle height and posture coupled control method for off-road multi-axle vehicle and vehicle therefor

Abstract

The application discloses a vehicle height and posture and wheel supporting force coupling control method for off-road multi-axle vehicles, and relates to active suspension technology of off-road multi-axle vehicles. Each wheel of the vehicle is configured with an actuator with an axial telescopic function, and a measurement system for measuring displacement and load of the actuator and posture of body pitching and rolling is configured. The control method firstly measures a load and deformation joint control matrix of the vehicle and current state parameters; calculates current vehicle height and posture and wheel supporting force of the vehicle; calculates posture adjustment amount of the actuator according to control expectation of pitching, rolling and height of the driver; superimposes control expectation of the wheel supporting force to calculate mixed adjustment amount of the vehicle height and posture and the wheel supporting force of the actuator; and finally implements synchronous adjustment of each actuator. The application can solve the coupling control of the vehicle height and posture and the wheel supporting force of the vehicle with any number of axles, and significantly improves passability, maneuverability and stability of the multi-axle vehicle under complex road conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of active suspension, in particular to the technical field of active suspension of off-road multi-axle vehicles. BACKGROUND

[0002] The active suspension system of an advanced vehicle and its control method should be able to achieve active control of vehicle height and posture during travel. For multi-axle (including two-axle and more than two-axle) vehicles with extensive off-road driving needs, when passing through extreme terrains such as longitudinal and transverse slopes, potholed roads, and rubble ruins, the distribution of wheel support reaction forces is often not ideal, and even one or more tires may be suspended or overloaded, resulting in insufficient adhesion and traction, and causing the vehicle body to shake violently, making it difficult to continue driving. If the coupling control of vehicle height, posture, and wheel support reaction force can be implemented during complex road travel, the passability, maneuverability, and stability of the vehicle during complex road travel can be greatly improved.

[0003] US 2019 / 0359025 A1 discloses an active suspension control system and control method. The suspension obtains the characteristics of the vehicle and the road surface through sensors, detects the pitch and roll state of the vehicle, and when the vehicle exceeds a horizontal threshold, an electronic controller controls the pressure in the adjustable suspension spring cavity to achieve horizontal control of the vehicle and correct the pitch and roll of the vehicle. When the vehicle is in a horizontal state, a pressure sensor detects whether the pressure in the adjustable suspension spring cavity exceeds a threshold to determine whether to adjust the pressure in each cavity to make the pressure in each wheel substantially equal. The disadvantage is that the vehicle body posture and wheel pressure of the control system are alternately controlled, rather than mixed and synchronized.

[0004] The coupling control of vehicle height, posture, and wheel support reaction force of current multi-axle vehicles under complex road conditions is still in the blank stage. The core problem is that the active control of the vehicle suspension is an over-determined problem, and the lifting of the actuator associated with any wheel will change the vehicle height and posture, and also cause the redistribution of the wheel support reaction force. The more axles, the more complex the control. If the vehicle height, posture, and wheel support reaction force are alternately controlled, the significant change of the other target in the iterative approximation process of any target will easily cause disturbance to the current target, resulting in defects in control accuracy and speed, and even causing the failure of control. SUMMARY

[0005] In view of the defects or deficiencies in the prior art, the present application proposes a vehicle height and posture and wheel supporting force coupling control method for off-road multi-axle vehicles. The control method takes the accurate characterization of the inherent load-carrying and deformation coupling properties of the vehicle as a prerequisite, first calculates the current vehicle height and posture and wheel supporting force according to the current state parameters; then, according to the driver's pitch, roll and height control expectations, the vehicle posture adjustment amount of the actuator is calculated; thirdly, the control expectation of the wheel supporting force is superimposed, and the mixed adjustment amount of the vehicle height, posture and wheel supporting force of the actuator is calculated; finally, the synchronous adjustment of each actuator is implemented. Under ideal conditions, any number of axle vehicles can simultaneously achieve the expected vehicle height, posture and wheel supporting force when passing through complex roads, thereby greatly improving the passability, maneuverability and stability of the vehicle when passing through complex roads.

[0006] In order to achieve the above purpose, the present application is realized by the following technical scheme. The vehicle height and posture and wheel supporting force coupling control method for off-road multi-axle vehicles, the vehicle can have any number of axles m of 2 or more. The wheels and the body of the vehicle are connected by active suspension, the active suspension adopts a double wishbone independent suspension structure, and the roll angle of the body relative to the horizontal plane is consistent with the roll angle of the wheel relative to the vertical plumb plane. The active suspension is provided with an actuator with axial extension function for each wheel, the actuator is connected in series with a shock absorber, and the stiffness of the shock absorber has been calibrated. It is worth noting that we do not limit the type of the actuator, which can be driven by a fluid system or an electromechanical system. When driven by a fluid system, the fluid can be any one of hydraulic fluid and compressed gas. Each wheel of the active suspension and its attached actuator and shock absorber are assigned a serial number i, i = 1, 2,..., n, n is the number of wheels. The vehicle is provided with displacement sensors for measuring the axial extension displacement of the actuator and force sensors for measuring the axial force, as well as inclination sensors for measuring the pitch angle and roll angle of the vehicle body. The driver's cabin of the vehicle is provided with pitch, roll, height and wheel supporting force adjustment switches, as well as a display screen with input and output functions, allowing the driver to input pitch, roll, height adjustment reference values and supporting force proportion of each wheel. The control method specifies a number of key nodes reflecting the attitude of the wheel, suspension and body, including but not limited to the center point of the wheel bottom surface and the wheel contour point, the upper and lower stop points of the active suspension, the hinge points of the double wishbone, and the vehicle height reference point defined by the intersection of the body longitudinal reference line and the active suspension cross section. The control method takes the vehicle driving in a high and low undulating off-road environment as a prerequisite, and the specific steps of the control method are as follows:

[0007] Step 1: Pre-construct a basic matrix for joint control of load and deformation: Place a vehicle with a horizontal posture and known height on a level and good road surface; Drive the i-th actuator to actively extend, and measure it in real time by the corresponding displacement sensor until a unit displacement is generated, during which other actuators are kept inactive; Measure the increment of the axial force of each actuator by the force sensor, and regard it as the increment of the corresponding wheel support reaction force, and store the increment of the wheel support reaction force in the order from 1 to n in the i-th column of the matrix from 1 to n.

[0008] At the same time, the roll angle and pitch angle increments of the vehicle body are measured by the tilt sensor, and the increments are sequentially stored in the n+1 to n+2 rows of the i-th column of the matrix in order from top to bottom.

[0009] Drive each actuator in turn and perform the above measurement and data storage until the basic matrix of joint control of load and deformation is constructed as shown in Formula 1

[0010]

[0011] Step 2: The tilt sensor measures the current pitch angle and roll angle of the vehicle body in real time, the displacement sensor measures the current axial telescopic displacement of the actuator in real time, and the force sensor measures the current axial force of the actuator in real time;

[0012] Step 3: Determine the local coordinate function of each key node of each axle, specifically including: based on each wheel on either side of the vehicle, establish the local rectangular coordinate system of each axle in order from the first axis to the mth axis. i x i y i z i , i = 1, 2, ..., m, where point o is always located at the lowest point of the wheel, the yz coordinate plane is flexibly parallel to the cross section of each axle active suspension, the x-axis is perpendicular to the yz coordinate plane and points in the direction of vehicle travel, the y-axis is horizontal and points to the left, and the z-axis is upward; within the local direct coordinate system of each axle, the local coordinate functions of each key node of each axle are sequentially established based on the body roll angle and the rotation angle of the axle double wishbone relative to the body;

[0013] Step 4: Determine the distance between the top dead center and the bottom dead center of the active suspension on both sides of each axle: Determine the absolute length of each actuator based on the current axial telescopic displacement of the actuator, and further determine the distance between the top dead center and the bottom dead center of the active suspension on both sides of each axle;

[0014] Step 5: Calculate the rotation angle of the double wishbone on both sides of each axle relative to the vehicle body: Calculate the rotation angle of the double wishbone on both sides of each axle relative to the vehicle body based on the distance between the top dead center and the bottom dead center of the active suspension on both sides of each axle;

[0015] Step 6: Determine the coordinates of all key nodes in the local rectangular coordinate system: Substitute the angles of the double wishbone relative to the vehicle body on both sides of each axle into the local coordinate function of each key node of each axle to determine the coordinates of all key nodes in the corresponding local rectangular coordinate system, referred to as local coordinates.

[0016] Step 7: Determine the coordinates of all key nodes in the global coordinate system, referred to as global coordinates, which specifically includes:

[0017] Establish a global coordinate system OXYZ with the origin of the local rectangular coordinate system of any axle as the origin, with the X-axis pointing horizontally forward, the Y-axis pointing horizontally left, and the Z-axis pointing vertically upward; determine the global coordinates of each key node of the axle according to the pitch angle of the vehicle body measured by the tilt sensor and the local coordinates of each key node of the axle in the global coordinate system.

[0018] Determine the global coordinates of the vehicle height reference points of other axles according to the pitch angle of the vehicle body measured by the tilt sensor; calculate the global coordinates of other key nodes according to their local coordinates and the global coordinates of the corresponding vehicle height reference points.

[0019] Step 8: Determine whether all wheels are in contact with the ground and implement ground contact adjustment: if not, i.e., there is a wheel in the air, then drive the associated actuator of the wheel in the air until all wheels are in contact with the ground; if yes, i.e., all wheels are in contact with the ground, then re-call steps 2 to 6 to recalculate the local coordinates of all key nodes.

[0020] Step 9: Construct a load and deformation combined control correction matrix: calculate the angles of each actuator relative to the longitudinal plumb plane of the vehicle body according to the local coordinates of all key nodes; divide the increments of each wheel support reaction force in the load and deformation combined control base matrix by the corresponding actuator angle relative to the longitudinal plumb plane of the vehicle body; divide the increments of each roll and pitch angle in the load and deformation combined control base matrix by the angle of the active elongation actuator relative to the longitudinal plumb plane of the vehicle body; thus obtain the load and deformation combined control correction matrix as follows

[0021]

[0022] In formula 2, σ j is the angle of the jth actuator relative to the longitudinal plumb plane of the vehicle body, σ i is the angle of the ith active elongation actuator relative to the longitudinal plumb plane of the vehicle body.

[0023] Step 10: Detect the pitch, roll, and height adjustment instructions of the driver; pick up the reference values of the pitch, roll, and height adjustment input by the driver or pre-stored in the internal memory.

[0024] Step 11: solving the vehicle posture adjustment amount of the actuator, specifically including:

[0025] According to the pitch angle reference value, the height adjustment reference value, and the z-axis coordinates of the current vehicle height reference points in the corresponding local rectangular coordinate system, the z-axis coordinates of the vehicle height reference points expected to be reached after active control are determined; the z-axis coordinates of the vehicle height reference points expected to be reached after active control are equal to the z-axis local coordinate functions of the corresponding vehicle height reference points.

[0026] At the same time, the z-axis coordinates of the center points of the bottom surfaces of the wheels on the opposite side of the wheel where the origin of the local rectangular coordinate system of the vehicle axle is located are equal to the z-axis local coordinate functions of the points.

[0027] According to the above equation, the angles of the double wishbone on both sides of the vehicle axle relative to the vehicle body after active control are solved.

[0028] The angles of the double wishbone on both sides of the vehicle axle relative to the vehicle body are substituted into the coordinate functions of the key nodes of the vehicle axle to calculate the coordinates of the upper and lower stop points of the active suspension on both sides of the vehicle axle after active control, and then the vehicle posture adjustment amount required by the actuator is determined;

[0029] Step 12: constructing the vehicle posture and wheel reaction force coupling control equation, specifically including:

[0030] According to the wheel reaction force adjustment command, the feasible optimal wheel load of the actuator is calculated: first, the wheel reaction force adjustment expectation F i s , the mean square error of the wheel reaction force F i and the wheel reaction force adjustment expectation F i is minimized as the optimization target, and the mechanical balance condition is used as the constraint to solve the wheel reaction force expectation initial value F s i *1 Since this method minimizes the mean square error of all wheel reaction forces as the optimization target, the result obtained may not be the globally optimal solution for some special wheel reaction force distribution expectations, so it is further optimized. Therefore, the feasible optimal wheel load F i *1 is obtained by setting the effective optimization range of the wheel reaction force and further optimizing the wheel reaction force expectation initial value F i * .

[0031] Based on the load and deformation combined control correction matrix, the feasible optimal wheel load, the pitch and roll adjustment reference values, the vehicle posture and wheel reaction force coupling control equation is established as follows

[0032]

[0033] F in formula 3 c F is a column vector of current wheel support reaction force, F * θ is a column vector of feasible optimal wheel load, θ * θ is a roll and pitch expected adjustment amount, θ c θ is a roll and pitch current amount, θ * -θ c is a column vector of roll and pitch adjustment reference value;

[0034] Step 13: solving the mixed adjustment amount of vehicle posture and wheel support reaction force of the actuator, solving formula 3, and correcting the result of formula 3 by the following formula to obtain the mixed adjustment amount of vehicle height and vehicle posture and wheel support reaction force

[0035]

[0036] {e in formula 4 i} r {e is a column vector of the vehicle posture adjustment amount, {e i} c is a column vector of the adjustment amount obtained by solving formula 3, is the average value of {e i} c σ i is the angle of each actuator relative to the longitudinal plumb surface of the vehicle body in the current state; {e i} f is the mixed adjustment amount of vehicle height and vehicle posture and wheel support reaction force;

[0037] Step 14: controlling all actuators to implement synchronous active extension adjustment: the active suspension control system drives all actuators to implement synchronous active extension adjustment, and simultaneously completes the extension adjustment at the next moment, that is, the mixed adjustment of vehicle height and vehicle posture and wheel support reaction force is completed;

[0038] Step 15: cyclically detecting whether the adjustment instruction of the driver is stopped: if there is still an adjustment instruction, jump to step 2 for continuous execution; if not, end the active control.

[0039] Another aspect of the present application is the vehicle height and vehicle posture and wheel support reaction force coupling control method of the off-road multi-axle vehicle, which is realized by calling steps 2 to 7 through the real-time output of the vehicle height and vehicle posture information in the display.

[0040] The beneficial effects of the present application are as follows:

[0041] 1. For two-axis or any axis number of vehicle, the vehicle height and attitude of the off-road multi-axle vehicle and the wheel supporting force coupling control method can realize the synchronous and active control of the vehicle height and attitude and the wheel supporting force. In complex road conditions, while ensuring that the vehicle height and attitude real-time pursuit target vehicle height and attitude, the wheel supporting force reaches the feasible wheel supporting force expectation, reduces the disturbance of the vehicle height and attitude caused by the ground supporting force, and maximizes the traction effect, providing a flexible, efficient, stable and safe suspension control method for the vehicle to pass through the complex road, significantly improving the passability, maneuverability and stability of the vehicle with any number of axes.

[0042] 2. The vehicle height and attitude of the off-road multi-axle vehicle and the wheel supporting force coupling control method takes the accurate characterization of the inherent load-bearing and deformation coupling properties of the vehicle as the premise, and in principle provides an active control method that can realize the synchronous target expectation of the vehicle height and attitude and the wheel supporting force without iteration. This scheme effectively avoids the time-consuming, oscillation, and even non-convergence caused by repeated measurement of vehicle height and attitude and wheel supporting force, and then cyclic judgment and iterative control. At the same time, this scheme does not require large sensing power, computing power and response speed requirements; it is a cost-effective, efficient and reliable control method.

[0043] 3. For the configuration of this suspension, the adjustment amount of the attitude and wheel supporting force coupling control equation has limited precision for the attitude and load synchronous control effect, so the precision of the attitude adjustment amount is higher and the precision of the coupling adjustment amount is lower to achieve load synchronous control under the more accurate attitude target. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 The control method flowchart of the vehicle height and attitude of the off-road multi-axle vehicle and the wheel supporting force coupling control method of the present application;

[0045] Figure 2 The vehicle structure schematic diagram of the vehicle height and attitude of the off-road multi-axle vehicle and the wheel supporting force coupling control method of the present application;

[0046] Figure 3 The control system block diagram of the vehicle height and attitude of the off-road multi-axle vehicle and the wheel supporting force coupling control method of the present application;

[0047] Figure 4 The coordinate system setting diagram of the vehicle height and attitude of the off-road multi-axle vehicle and the wheel supporting force coupling control method of the present application;

[0048] Figure 5 The key node setting diagram of the vehicle height and attitude of the off-road multi-axle vehicle and the wheel supporting force coupling control method of the present application;

[0049] Figure 6This is a vehicle height reference point diagram for the vehicle height, vehicle posture and wheel support reaction force coupling control method of the non-road multi-axle vehicle of the present invention.

[0050] In the figure: 1. Vehicle; 2. Wheel; 3. Body; 4. Active suspension; 5. Transverse arm; 6. Actuator; 7. Shock absorber; 8. Ground; 9. Displacement sensor; 10. Force sensor; 11. Inclination sensor. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. Figure 2 、 Figure 3 The actuator system, sensing system and control system of the 3-axle independent suspension vehicle shown, and Figure 1 The control method flow chart shown in the figure provides a specific example of a method for coupling vehicle height, vehicle posture, and wheel support reaction force control for an off-road multi-axle vehicle. It should be understood that the specific embodiments described herein are merely illustrative of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments described herein without inventive effort are intended to fall within the scope of protection of this application.

[0052] The control method of the vehicle height and attitude coupled with the wheel supporting force of the off-road multi-axle vehicle, the vehicle 1 can have any axle number m of 2 or more, that is, the control method is applicable to off-road vehicles with any axle number of 2 or more. The wheels 2 and the body 3 of the vehicle 1 are connected by active suspension 4, which adopts a double wishbone independent suspension structure, and the roll angle of the body 3 relative to the horizontal plane is consistent with the roll angle of the wheel 2 relative to the vertical plane. The active suspension 4 is provided with an actuator 6 with axial extension function for each wheel 2, the actuator 6 is connected in series with a shock absorber 7, and the stiffness of the shock absorber 7 has been calibrated. Each wheel 2 of the active suspension 4 and its attached actuator 6 and shock absorber 7 are assigned a unified serial number i, i = 1, 2,..., n, n is the number of wheels 2. The vehicle 1 is provided with displacement sensors 9 and force sensors 10 for measuring the axial displacement of the actuator 6 and the axial force, and inclination sensors 11 for measuring the pitch angle and roll angle of the vehicle body 3. The cockpit of the vehicle 1 is provided with pitch, roll, height and wheel supporting force adjusting switches, as well as input and output function display screen, allowing the driver to input pitch, roll, height adjustment reference value and supporting force proportion of each wheel 2. The control method specifies a number of key nodes reflecting the attitude of the wheel 2, the active suspension 4 and the body 3, including but not limited to the wheel 2 bottom center point E and the wheel 2 contour point, the upper stop point G, I and the lower stop point F, H of the active suspension 4, the hinge points A, B, C of the double wishbone 5, and the vehicle height reference point T defined by the intersection of the body 3 longitudinal reference line and the active suspension 4 cross section. It should be noted that in the calculation of any axle, the key nodes are given without subscript; while in the calculation of the position relationship between the axles, the key nodes are given with subscript. The subscripts 1, 2, 3 correspond to the Figure 6 1st, 2nd and 3rd axles of the 3-axle independent suspension vehicle shown.

[0053] The control method takes the vehicle driving in the high and low undulating off-road environment as the premise, including the following steps:

[0054] Step 101: Pre-construct the load and deformation combined control basic matrix: place the vehicle 1 with known vehicle attitude level and vehicle height on the horizontal and good road surface; drive the i-th actuator 6 to actively extend, and measure it in real time by the corresponding displacement sensor 9 until a unit displacement is generated, during which other actuators 6 are not actively adjusted; measure the increment of the axial force of each actuator 6 by the force sensor 10, and regard it as the increment of the corresponding wheel supporting force, and store the increments of the wheel supporting force in the 1st to n-th rows of the i-th column of the matrix in order from 1 to n.

[0055] Meanwhile, the roll angle and the pitch angle increments of the vehicle body 3 are measured by the roll and pitch angle sensor 11, and the increments are sequentially stored in the (n+1)th to (n+2)th rows of the ith column of the matrix in the order from top to bottom.

[0056] The actuators 6 are sequentially driven, and the above measurement and data storage are performed until the load and deformation combined control base matrix as shown in formula 1 is constructed.

[0057]

[0058] Step 102: Real-time measurement of the current pitch angle and roll angle of the vehicle body 3 by the roll and pitch angle sensor 11, real-time measurement of the current axial extension displacement of the actuator 6 by the displacement sensor 9, and real-time measurement of the current axial force of the actuator 6 by the force sensor 10.

[0059] Step 103: Determination of the local coordinate functions of the key nodes of each axle, specifically including: based on the wheels on either side of the vehicle 1, sequentially establishing the local rectangular coordinate system ox i x i y i z i of each axle from the 1st axle to the mth axle, wherein the o point is always located at the lowest point of the wheel, the yz coordinate plane is parallel to the cross section of the active suspension 4 of each axle, the x axis is perpendicular to the yz coordinate plane and points to the forward direction of the vehicle, the y axis is horizontally to the left, and the z axis is upward; in the local rectangular coordinate system of each axle, based on the roll angle a of the vehicle body 3, the rotation angles β and γ of the double wishbone 5 relative to the vehicle body 3, the local coordinate functions of the key nodes of each axle are sequentially established. For example, as shown in Figure 5 , according to the coordinate transformation theory, the coordinates of the key node A in the local rectangular coordinate system o3x3y3z3 satisfy formula 2

[0060]

[0061] In formula 2, r w is the wheel radius, r f is 1 / 2 of the double wishbone height difference, Rot(x, a) is the coordinate conversion matrix, and formula 3 is satisfied.

[0062]

[0063] The coordinates of the key node B in the local rectangular coordinate system o3x3y3z3 can be recursively obtained based on the local coordinates of the key node A, and formula 4 is satisfied.

[0064]

[0065] In formula 4, l dL is the length of the double wishbone 5, β is the rotation angle of the right double wishbone relative to the vehicle body 3.

[0066] The coordinate functions of each key node of each axle can be derived by analogy from the above method. It can be understood that the coordinates of the key nodes in the corresponding local rectangular coordinate system are functions of the rotation angles β and γ of the double wishbones 5 of each axle relative to the vehicle body 3.

[0067] Step 104: determining the distance between the upper and lower stops of the active suspension 4 on both sides of each axle, specifically including:

[0068] The absolute length of each actuator 6 is determined by the current axial telescopic displacement of the actuator 6, and the absolute length of each actuator 6 is determined.

[0069] The axial force of each shock absorber 7 of each axle is measured by the force sensor 10, and the absolute length of each shock absorber 7 is determined according to its stiffness characteristics.

[0070] The distance between the upper and lower stops of the active suspension 4 on both sides of each axle is determined by combining the two, i.e. GF and L HI ;

[0071] Step 105: solving the rotation angles β and γ of the double wishbones 5 on both sides of each axle relative to the vehicle body 3:

[0072] One way is to establish a system of equations for each axle active suspension 4 according to the coordinate functions of the upper and lower stops of the active suspension 4 on both sides of each axle and the determined distance between the upper and lower stops, and solve the rotation angles β and γ of the double wishbones 5 on both sides of each axle relative to the vehicle body 3.

[0073] Another way is to solve the rotation angle β according to L GF , the length L GB of the key nodes G and B, the length L FB of the key nodes F and B, and the triangular angle calculation formula; HI , the length L IC of the key nodes I and C, the length L CH of the key nodes C and H, and the triangular angle calculation formula;

[0074] Step 106: determining the coordinates of all key nodes in the local rectangular coordinate system: it can be understood that the calculated rotation angles β and γ of the double wishbones 5 on both sides of each axle relative to the vehicle body 3 are substituted into the coordinate functions of each key node of each axle, and the coordinates of all key nodes in the corresponding local rectangular coordinate system are determined.

[0075] Step 107: determining the coordinates of all key nodes in the global coordinate system, specifically including:

[0076] The global coordinate system OXYZ is established with the origin of the local rectangular coordinate system of any axle as the origin, with the X axis pointing horizontally to the front of the vehicle, the Y axis pointing horizontally to the left, and the Z axis pointing vertically upward; the pitch angle of the vehicle body 3 measured by the tilt sensor 11 And the local coordinates of each key node of the axle where the global coordinate system is located, determine the global coordinates of each key node of the axle. Figure 4 and Figure 6 The global coordinate system OXYZ and the local rectangular coordinate system o3x3y3z3 are located on the same axle. The key node G of the third axis is denoted as G3. Its global coordinates can be obtained by formula 5

[0077]

[0078] In formula 5 is the coordinate transformation matrix, satisfying Formula 6

[0079]

[0080] The pitch angle of the vehicle body 3 measured by the tilt sensor 11 Determine the global coordinates of the vehicle height reference points of the other axles. Taking the second axle as an example, the global coordinates of the vehicle height reference point T2 of the axle satisfy Formula 7

[0081]

[0082] The global coordinates of the key nodes are calculated based on the local coordinates of the other key nodes and the global coordinates of the corresponding vehicle height reference point. Taking the second axis as an example, the global coordinates of the key node G of the axis, denoted as G2, satisfy the formula 8

[0083]

[0084] Step 108: Determine whether all wheels 2 are in contact with the ground, and implement ground contact adjustment: If not, i.e., a wheel 2 is suspended, the actuator 6 associated with the suspended wheel 2 is driven to operate until all wheels 2 are in contact with the ground 8; if yes, i.e., all wheels 2 are in contact with the ground, then recall steps 2 to 6 and recalculate the local coordinates of all key nodes;

[0085] Step 109: Constructing a correction matrix for joint load and deformation control: Calculate the angle of each actuator 6 relative to the longitudinal plumb plane of the vehicle body in the current state based on the local coordinates of all key nodes; divide the increment of each wheel support reaction force in the joint load and deformation control basic matrix by the angle of the corresponding actuator 6 relative to the longitudinal plumb plane of the vehicle body; divide the increment of each roll angle and pitch angle in the joint load and deformation control basic matrix by the angle of the actively extended actuator 6 relative to the longitudinal plumb plane of the vehicle body; thus, the joint load and deformation control correction matrix is ​​obtained as follows:

[0086]

[0087] σ in formula 9 j is the angle of the jth actuator 6 relative to the longitudinal plumb plane of the vehicle body, σ i is the angle of the i-th actively extended actuator 6 relative to the longitudinal plumb plane of the vehicle body;

[0088] Step 110: Detecting the driver's pitch, roll, and height adjustment instructions; picking up the reference values ​​of the pitch, roll, and height adjustment input by the driver or pre-stored in the internal memory;

[0089] Step 111: Calculating the vehicle posture adjustment amount of the actuator 6, specifically including:

[0090] The z-axis coordinates of each vehicle height reference point expected to be reached after active control are determined based on the pitch angle reference value, the height adjustment reference value, and the z-axis coordinates of each current vehicle height reference point in the corresponding local rectangular coordinate system.

[0091] by Figure 6 Assume that the driver triggers the pitch, left and rise adjustment commands at the same time, and the reference values ​​of pitch, roll and height adjustment are the default values. Then, the z-axis coordinate of the vehicle body reference point T2 after active control satisfies Where △z is the height adjustment reference value, k1 is the lifting pointer, k1 = 1 when adjusting to increase, and k1 = -1 when adjusting to decrease; is the pitch angle adjustment reference value, k2 is the pitch pointer, k2=-1 when adjusting downward, and k2=1 when adjusting upward.

[0092] Let the z-axis coordinate of each vehicle height reference point expected to be reached after active control be equal to the z-axis coordinate function of the corresponding vehicle height reference point. Simultaneously, let the z-axis coordinate of the bottom center point of the wheel 2 opposite the wheel 2 where the origin of the local rectangular coordinate system of each axle is located, i.e., point E, be equal to the z-axis coordinate function of that point. It should be noted that the z-axis coordinate function of the vehicle height reference point and the z-axis coordinate function of the bottom center point of the opposite wheel are functions of the rotational angles β and γ of the double wishbone 5 of each axle relative to the vehicle body 3. The above equations can be used to solve for the rotational angles of the double wishbone on both sides of each axle relative to the vehicle body 3 after active control.

[0093] Substituting the rotation angles of the double wishbones on both sides of each axle relative to the vehicle body 3 into step 103, the coordinates of the top and bottom dead centers of the active suspension on both sides of each axle after active control are calculated. The distance between the top and bottom dead centers after active control is calculated based on the coordinates of the top and bottom dead centers of the active suspension on both sides of each axle after active control, and subtracting this distance from the current distance between the top and bottom dead centers to determine the required vehicle posture adjustment amount for all actuators.

[0094] Step 112: Construct the vehicle posture and wheel support reaction force coupling control equation, specifically including:

[0095] The active suspension controller or the driver needs to define the wheel support reaction force adjustment command that adapts to the road surface characteristics, that is, the wheel support reaction force adjustment expectation F i s Then, the wheel supports the reaction force F i Expected distribution of wheel reaction force F i s The optimization goal is to minimize the mean square error of the wheel support force, and the mechanical equilibrium condition is constrained. The optimization model shown in Formula 10 is used to solve the expected initial value F of the wheel support force. i *1

[0096]

[0097] In Formula 10, F i s =F i * The expected forced wheel support reaction force set for certain key wheels 2 is: is the uniform wheel reaction force expectation set for other general wheels 2, where p is the number of wheels 2 with mandatory wheel reaction force distribution, and G is the total vehicle weight. They are the vertical force balance constraint of vehicle 1, and the moment balance constraints around the x-axis and the y-axis.

[0098] Solving formula 10 can obtain the expected initial value F of the wheel support reaction force of each wheel i *1 However, since this method aims to minimize the mean square error of all wheel reaction forces, the result obtained by the calculation may not be a global optimal solution for some special wheel reaction force distribution expectations, so it needs to be further optimized. Therefore, it is also necessary to use the initial value of the wheel reaction force expectation F i *1 To optimize the initial value, set the effective optimization range F of the wheel support reaction force i lb ≤F i ≤F i ub , and still subject to the mechanical equilibrium condition, the optimization algorithm is called to solve the feasible optimal wheel load F i * , i=1,2,...n.

[0099] Based on the load and deformation joint control correction matrix, the feasible optimal wheel load, and the pitch and roll adjustment reference values, the vehicle posture and wheel support reaction force coupling control equation is established as shown in Formula 11

[0100]

[0101] F in formula 11 c F is a column vector of current wheel support reaction force, F * θ is a column vector of feasible optimal wheel load, θ * θ is a column vector of roll and pitch expected adjustment amount, θ c θ is a column vector of roll and pitch current amount, θ * -θ c i.e. a column vector composed of roll and pitch adjustment reference values;

[0102] Step 113: solving the mixed adjustment amount of vehicle posture and wheel support reaction force of the actuator 6: solving the formula 11; the result obtained by the formula 11 can be corrected by the following formula 12 to obtain the mixed adjustment amount of vehicle height and vehicle posture and wheel support reaction force

[0103]

[0104] {e in formula 12 i} r {e is a column vector of the vehicle posture adjustment amount, {e i} c is the adjustment amount column vector obtained by solving the formula 11, is the average value of {e i} c σ i is the angle of each actuator 6 relative to the longitudinal plumb plane of the vehicle body in the current state; {e i} f i.e. the mixed adjustment amount of vehicle height and vehicle posture and wheel support reaction force;

[0105] Step 114: controlling all actuators 6 to implement synchronous active extension adjustment: the active suspension controller calls the control method, first outputs the current wheel, suspension and vehicle posture information of the vehicle in the form of graphics and numbers in the explicit screen, and the wheel load information calculated according to the axial force of each actuator; then drive each actuator to implement synchronous active extension adjustment, complete the extension adjustment at the same time at the next moment, i.e. complete the mixed adjustment of vehicle height and vehicle posture and wheel support reaction force;

[0106] Step 115: cyclically detecting whether the driver's adjustment instruction is stopped: if there is still an adjustment instruction, jump to step 2 for continuous execution; if not, end the active control.

[0107] 2. The vehicle height and vehicle posture and wheel support reaction force coupling control method of the off-road multi-axle vehicle, which outputs the vehicle height and vehicle posture information of the vehicle 1 in the form of graphics in the explicit screen by calling steps 2 to 7.

[0108] Finally, it should be noted that the above merely describes the preferred embodiments of the present application and the principles of the technology applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that various obvious changes, reconfigurations and substitutions can be made by those skilled in the art without departing from the scope of the present application. Therefore, although the present application has been described in detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the appended claims.

Claims

1. A method for coupling vehicle height, vehicle posture, and wheel support reaction force control for an off-road multi-axle vehicle, wherein the vehicle has two or more axles, or any number m; the vehicle's wheels and body are connected via an active suspension, the active suspension employing a double wishbone independent suspension configuration, wherein the body's roll angle relative to the horizontal plane is consistent with the wheel's roll angle relative to the longitudinal plumb plane; the active suspension is configured with an actuator having an axial telescopic function for each wheel, the actuator being connected in series with a shock absorber, the shock absorber having a calibrated stiffness; each wheel of the active suspension and its associated actuator and shock absorber are assigned a serial number i, where i = 1, 2, ..., n, where n is the number of wheels; the vehicle is configured with a displacement sensor and a A force sensor for axial force, and an inclination sensor for measuring the pitch angle and roll angle of the vehicle body; the vehicle cockpit is equipped with pitch, roll, height and wheel support reaction force adjustment switches, as well as a display screen with input and output functions, allowing the driver to input pitch, roll, height adjustment reference values ​​and the support reaction force ratio of each wheel; the control method specifies several key nodes that reflect the posture of the wheels, suspension and vehicle body, including but not limited to the center point and wheel contour point of the wheel bottom surface, the top dead center and bottom dead center of the active suspension, the hinge points of the double wishbone, and the vehicle height reference point defined by the intersection of the longitudinal reference line of the vehicle body and the cross section of the active suspension; the control method is based on the premise that the vehicle is traveling in an uneven non-road environment, and is characterized in that, The following steps are involved: Step 1: Pre-construct the basic matrix for joint control of load and deformation: Place a vehicle with a horizontal posture and known height on a level and good road surface; The i-th actuator is driven to actively extend, and the corresponding displacement sensor measures the extension in real time until a unit displacement is generated, during which other actuators are kept inactive; the force sensor measures the increment of the axial force of each actuator, which is regarded as the increment of the corresponding wheel support reaction force, and the increment of the wheel support reaction force is sequentially stored in the i-th column and the 1st to nth rows of the matrix in order from 1 to n; At the same time, the tilt sensor measures the roll angle and pitch angle increments of the vehicle body, and stores the increments in the (n+1) to (n+2) rows of the (i) column of the matrix in descending order. Drive each actuator in turn and perform the above measurement and data storage until the basic matrix of joint control of load and deformation is constructed as shown in Formula 1 Step 2: The tilt sensor measures the current pitch angle and roll angle of the vehicle body in real time, the displacement sensor measures the current axial telescopic displacement of the actuator in real time, and the force sensor measures the current axial force of the actuator in real time; Step 3: Determine the local coordinate function of each key node of each axle, specifically including: based on each wheel on either side of the vehicle, establish the local rectangular coordinate system of each axle in order from the first axis to the mth axis. i x i y i z i , i = 1, 2, ..., m, where point o is always located at the lowest point of the wheel, the yz coordinate plane is flexibly parallel to the cross section of the active suspension of each axle, the x-axis is perpendicular to the yz coordinate plane and points in the direction of vehicle travel, the y-axis is horizontal and points to the left, and the z-axis is upward; within the local direct coordinate system of each axle, the local coordinate function of each key node of each axle is sequentially established based on the body roll angle and the angle of the double wishbone relative to the body; Step 4: Determine the distance between the top dead center and the bottom dead center of the active suspension on both sides of each axle: Determine the absolute length of each actuator based on the current axial telescopic displacement of the actuator, and further determine the distance between the top dead center and the bottom dead center of the active suspension on both sides of each axle; Step 5: Calculate the rotation angle of the double wishbone on both sides of each axle relative to the vehicle body: Calculate the rotation angle of the double wishbone on both sides of each axle relative to the vehicle body based on the distance between the top dead center and the bottom dead center of the active suspension on both sides of each axle; Step 6: Determine the coordinates of all key nodes in the local rectangular coordinate system: Substitute the rotation angles of the double wishbones on both sides of each axle relative to the vehicle body into the local coordinate function of each key node of each axle to determine the coordinates of all key nodes in the corresponding local rectangular coordinate system, referred to as local coordinates; Step 7: Determine the coordinates of all key nodes in the global coordinate system, referred to as global coordinates, including: Establishing a global coordinate system OXYZ with the origin of the local rectangular coordinate system of any axle as the origin, with the X axis pointing horizontally toward the front of the vehicle, the Y axis pointing horizontally to the left, and the Z axis pointing vertically upward; determining the global coordinates of the key nodes of the axle based on the pitch angle of the vehicle body measured by the inclination sensor and the local coordinates of the key nodes of the axle where the global coordinate system is located; Determine the global coordinates of the vehicle height reference points of other axles based on the vehicle body pitch angle measured by the inclination sensor; calculate the global coordinates of other key nodes based on the local coordinates of the key nodes and the global coordinates of the corresponding vehicle height reference points; Step 8: Determine whether all wheels are in contact with the ground and implement contact adjustment: If not, that is, a wheel is suspended, drive the actuator associated with the suspended wheel to actuate until all wheels are in contact with the ground; if yes, that is, all wheels are in contact with the ground, call steps 2 to 6 again and recalculate the local coordinates of all key nodes; Step 9: Construct the load-bearing and deformation joint control correction matrix: Calculate the angle of each actuator relative to the longitudinal plumb plane of the vehicle body in the current state based on the local coordinates of all key nodes; divide the increment of each wheel support reaction force in the load-bearing and deformation joint control basic matrix by the angle of the corresponding actuator relative to the longitudinal plumb plane of the vehicle body; divide the increment of each roll angle and pitch angle in the load-bearing and deformation joint control basic matrix by the angle of the actively extended actuator relative to the longitudinal plumb plane of the vehicle body; thus, the load-bearing and deformation joint control correction matrix is ​​obtained as follows σ in formula 2 j is the angle of the jth actuator relative to the longitudinal plumb plane of the vehicle body, σ i is the angle of the i-th actively extended actuator relative to the longitudinal plumb plane of the vehicle body; Step 10: Detecting the driver's pitch, roll, and height adjustment instructions; picking up the reference values ​​of the pitch, roll, and height adjustment input by the driver or pre-stored in the internal memory; Step 11: Calculate the vehicle posture adjustment amount of the actuator, including: Determining the z-axis coordinates that each vehicle height reference point is expected to reach after active control based on the pitch angle reference value, the height adjustment reference value, and the z-axis coordinates of each current vehicle height reference point in the corresponding local rectangular coordinate system; setting the z-axis coordinates that each vehicle height reference point is expected to reach after active control to be equal to the z-axis local coordinate function of the corresponding vehicle height reference point; At the same time, let the z-axis coordinate of the center point of the bottom surface of the wheel opposite to the wheel where the origin of the local rectangular coordinate system of each axle is located be equal to the z-axis local coordinate function of the point; According to the above equation, the rotation angle of the double wishbone on both sides of each axle relative to the vehicle body after active control is solved; Substituting the rotation angle of the double wishbone on both sides of each axle relative to the vehicle body into the coordinate function of the key nodes of each axle, calculating the coordinates of the top dead center and bottom dead center of the active suspension on both sides of each axle after active control, and then determining the required vehicle posture adjustment amount of the actuator; Step 12: Construct the vehicle posture and wheel support reaction force coupling control equation, including: Calculate the feasible optimal wheel load according to the wheel support reaction force adjustment instruction; Based on the load and deformation joint control correction matrix, the feasible optimal wheel load, and the pitch and roll adjustment reference values, the vehicle posture and wheel support reaction force coupling control equation is established as follows: F in Formula 3 c is the column vector of the current wheel support reaction force, F * is the column vector of feasible optimal wheel load, θ * is the expected roll and pitch adjustment, θ c is the current amount of roll and pitch, θ * -θ c That is, the column vector composed of the roll and pitch adjustment reference values; Step 13: Calculate the mixed adjustment amount of the vehicle height, vehicle posture and wheel support reaction force of the actuator: solve the above formula 3; modify the result of formula 3 by the following formula to obtain the mixed adjustment amount of vehicle height, vehicle posture and wheel support reaction force {e in formula 4 i } r is the column vector of the vehicle posture adjustment amount, {e i } c To solve the adjustment column vector obtained by formula 3, For {e i } c The average value of σ i The angle of each actuator relative to the longitudinal plumb plane of the vehicle body in the current state; i } f That is the mixed adjustment amount of vehicle height, vehicle posture and wheel support reaction force; Step 14: Control all actuators to synchronously perform active telescopic adjustment: The active suspension control system drives all actuators to synchronously perform active telescopic adjustment, completing the telescopic adjustment amount simultaneously at the next moment, thus completing the mixed adjustment of vehicle height, vehicle posture, and wheel support reaction force; Step 15: cyclically detect whether the driver's adjustment command has stopped: if there is still an adjustment command, jump to step 2 to continue execution; if so, end the active control.

2. The vehicle height, posture and wheel support reaction force coupling control method for a non-road multi-axle vehicle as described in claim 1 outputs the vehicle height and posture information of the vehicle in real time in a graphical form on a display screen by calling steps 2 to 7.

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