Electro-hydraulic active suspension constant force output tracking control method for high-speed tracked vehicle

Abstract

According to the electro-hydraulic active suspension constant force output tracking control method for the high-speed tracked vehicle, the active force can be output in real time, the output of the active force can be tracked in real time, fuzzy PID is utilized, output errors are reduced, and the system stability is improved. Calculating the output force of the active suspension when the acceleration of the vehicle body is maintained to be 0 according to each suspension displacement, then calculating the actual output force of the actuator according to a pressure sensor of a high-low pressure working cavity on the actuator, and tracking and controlling the actual output force through an inner loop fuzzy control method to enable the actual output force to be close to the calculated output force; the active suspension outputs constant force to reduce the influence of spring elastic elements such as a torsion bar on pitching and vibration of a vehicle body, and the smoothness and comfort of the vehicle are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of vehicle engineering, and particularly relates to a constant force output tracking control method for an electro-hydraulic active suspension of a high-speed tracked vehicle. Background Art

[0002] The shock absorber or suspension system is an important guarantee for the ride comfort and driving safety of a vehicle. Due to its non-adjustable characteristics, the passive suspension can only adopt a parameter design method that compromises between comfort and stability in the selection of the characteristics of the stiffness and damping elements, and the allowable dynamic stroke space in the design cannot be utilized effectively in real time. The active suspension replaces the elastic element and the shock absorption device with the execution unit of the active actuator, has a large adjustment bandwidth, and automatically and real-time changes the active output force according to the changes of the external conditions and the environment, ensuring the ride comfort and driving safety of the vehicle to the greatest extent.

[0003] The key to the active suspension is to require a control law that can provide good performance for the vehicle. The traditional constant force control requires PID feedback control to reduce the active force output error, and the PID parameters are fixed values. However, the tracked vehicle has strong hysteresis and large inertia. In addition, since the system state of the tracked vehicle changes continuously during operation, the PID control parameters also need to be adjusted online, but the traditional constant force control cannot meet this condition. In addition, during the operation of the vehicle, it is necessary to track the active force output in real time to reduce the output error. Summary of the Invention

[0004] In view of the technical problems existing in the prior art, the present invention proposes a constant force output tracking control method for an electro-hydraulic active suspension of a high-speed tracked vehicle, which can output the active force in real time, track the active force output in real time, utilize fuzzy PID to reduce the output error, and improve the system stability.

[0005] The present invention is realized through the following technical solutions.

[0006] A constant force output tracking control method for an electro-hydraulic active suspension of a high-speed tracked vehicle includes the following steps:

[0007] Step 1: According to Newton's second law of motion, establish a 1 / 4 suspension dynamics model, that is, a vehicle dynamics differential equation in the vertical direction of the unsprung mass.

[0008] Step 2: When the wheel hits a protrusion, the spring compresses, the suspension displacement is negative, the suspension speed is negative, the active force is negative, and the direction is downward. The force exerted by the active suspension on the wheel is upward, that is, it lifts the wheel, and the magnitude of the output active force is the sum of the spring force of the suspension and the damping force of the suspension; when the wheel encounters a depression, the spring stretches, the suspension displacement is positive, the suspension speed is positive, the active force is positive, and the direction is upward. The force exerted by the active suspension on the wheel is downward, that is, it presses the wheel, and the magnitude of the output active force is the sum of the spring force of the suspension and the damping force of the suspension.

[0009] Step 3: The suspension controller outputs the active force in real time and performs closed-loop PID control. During the driving process of the tracked vehicle, the road surface applies excitation to the road wheels, causing the torsion bar elastic element to rotate. The elastic element acts on the vehicle body in the opposite direction, and the active suspension outputs a constant force to reduce the influence of spring elastic elements such as torsion bars on the pitching and vibration of the vehicle body. The suspension controller obtains the magnitude of the ideal active force required by the suspension system through a constant force algorithm, and calculates the reference current of the servo valve at this time according to the relationship between the active force of the system and the servo valve current obtained from the active suspension output force characteristic test. The hydraulic system changes the pressures in the two chambers of the suspension actuator through the servo valve. The controller collects the pressure values in the two chambers, and further calculates the actual output active force value of the actuator, the difference between the real-time suspension output active force and the model-calculated tension force, the change rate of the difference, and the correction amounts of the proportional coefficient and integral coefficient of the suspension active force output adjustment PID controller.

[0010] Step 4: The outer loop control uses a constant force control algorithm, and the inner loop closed-loop control uses the fuzzy logic algorithm of a fuzzy PID controller to optimize the PID parameters in real time according to fuzzy rules until the ideal control effect is achieved. At the same time, the real-time suspension output active force and the model-calculated tension force are compared, and fuzzy reasoning is performed according to the deviation and its change rate to obtain the correction amounts of parameters P and I, and then the suspension output active force compensation amount is obtained. Further, the servo valve output current compensation amount is obtained, so as to achieve the function of adjusting the active force in real time.

[0011] Advantages of the present invention:

[0012] 1. Through the control of the active suspension, the outer loop control uses a constant force control algorithm, and the inner loop closed-loop control uses a fuzzy PID. The PID parameters are optimized in real time according to certain fuzzy rules.

[0013] 2. The present invention can reduce the output error, overshoot and chattering of the system, improve the system stability, and achieve a relatively ideal control effect.

[0014] 3. The present invention can adjust the suspension active force in real time, and has the characteristics of fast response and high precision. Brief Description of the Drawings

[0015] Figure 1 It is the schematic diagram of the constant force output tracking control method for the electro-hydraulic active suspension of the high-speed tracked vehicle of the present invention.

[0016] Figure 2 It is the 1 / 4 suspension dynamics model of the present invention. Detailed Embodiments

[0017] The exemplary embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the drawings are merely exemplary, intended to illustrate the principles and spirit of the present invention, and not to limit the scope of the present invention.

[0018] As Figure 1 shown, a constant force output tracking control method for the electro-hydraulic active suspension of a high-speed tracked vehicle according to the present invention specifically includes the following steps:

[0019] Step 1: According to Newton's second law of motion, establish a 1 / 4 suspension dynamics model, that is, the vehicle dynamics differential equation in the vertical direction of the sprung mass is:

[0020]

[0021] In the formula, m b is the sprung mass, k s is the suspension stiffness, x b is the sprung displacement, x w is the unsprung displacement, C s is the suspension damping coefficient, U a is the active control force used to suppress the vertical vibration of the vehicle body. Since the vehicle ride comfort is evaluated by the vehicle body vibration acceleration, the smaller the acceleration, the better the vehicle ride comfort. Therefore, let be 0, then the formula (1) is transformed into:

[0022]

[0023] To maintain the vehicle ride comfort, that is, the sprung acceleration is 0, then the magnitude of the target output force of the active suspension is the spring force k s (x b -x w ) plus the damping force of the suspension In the formula, (x b -x w ) is the suspension displacement, is the suspension speed, and the positive direction is vertically upward;

[0024] Step 2: When the wheel hits a protrusion, the spring compresses, the suspension displacement (x b -x w ) is negative, the suspension speed is negative, U a The active force is negative and the direction is downward. The active suspension acts on the wheel upward, that is, it lifts the wheel, and the magnitude of the output active force is the spring force of the suspension plus the damping force of the suspension; when the wheel encounters a depression, the spring stretches, the suspension displacement (x b -x w ) is positive, the suspension speed is positive, U aThe driving force is positive and upward. The force exerted by the active suspension on the wheel is downward, i.e., pressing the wheel. The magnitude of the output driving force is the sum of the spring force and the damping force of the suspension.

[0025] Step 3: The suspension controller outputs the driving force in real time and performs closed-loop PID control. During the driving process of the tracked vehicle, the road surface applies excitation to the load-bearing wheels, causing elastic components such as torsion bars to rotate. The elastic components act on the vehicle body in the opposite direction, and the active suspension outputs a constant force to reduce the influence of spring elastic components such as torsion bars on the pitch and vibration of the vehicle body. The suspension controller obtains the magnitude of the ideal driving force required by the suspension system through a constant force algorithm, and calculates the reference current of the servo valve at this time according to the relationship between the driving force and the servo valve current obtained from the active suspension output force characteristic test. The hydraulic system changes the pressures in the two chambers of the suspension actuator through the servo valve. The controller collects the pressure values in the two chambers, and further calculates the actual output driving force value of the actuator, the difference e between the real-time suspension output driving force and the tension force calculated by the model T , the change rate du / dt of the difference value, and the correction amounts ΔK P and ΔK I ;

[0026] Step 4: The constant force control algorithm is used for the outer loop control, and the fuzzy logic algorithm of the fuzzy PID controller is used for the inner loop closed-loop control. The PID parameters are optimized in real time according to the fuzzy rules until the ideal control effect is achieved. At the same time, the real-time suspension output driving force and the tension force calculated by the model are compared, and fuzzy reasoning is performed according to the deviation and its change rate to obtain the correction amounts of parameters P and I. Then, the compensation amount of the suspension output driving force is obtained, and further the compensation amount of the servo valve output current is obtained, so as to achieve the function of adjusting the driving force in real time.

[0027] In this embodiment, the real-time optimization of the PID parameters according to the fuzzy rules is specifically as follows:

[0028] 1) When the deviation between the suspension output driving force and the tension force calculated by the model is large, in order to shorten the system response time and avoid overshoot, make K P take a large value, and K I take a value of 0; when the deviation is small, in order to further reduce the deviation and prevent overshoot and deterioration of stability, reduce the value of K P , and K I take a smaller value; when the deviation is very small, in order to further eliminate the static error, prevent overshoot, and ensure that the suspension driving force is stabilized as soon as possible, the value of K P should continue to decrease, and the value of K I remains unchanged or takes a slightly larger value;

[0029] 2) When the deviation between the suspension output driving force and the model-calculated tension force and the change rate of the deviation have the same sign, it indicates that the difference between the current track tension force and the reference track tension force is increasing. To eliminate the tension force deviation as soon as possible, the K P value takes the maximum. When the deviation between the suspension output driving force and the model-calculated tension force and the change rate of the deviation have different signs, the K P value gradually decreases as the deviation decreases.

[0030] Among them, the fuzzy control table of the proportional coefficient and the integral coefficient correction amount is shown in the following table. Among them: NB, NM, NS, Z, PS, PM, and PB respectively represent that the fuzzy states of the variables are negative large, negative medium, negative small, zero, positive small, positive medium, and positive large.

[0031] Table 1 Fuzzy control table of proportional coefficient correction amount

[0032]

[0033] Table 2 Fuzzy control table of integral coefficient correction amount

[0034]

[0035]

[0036] During the high-speed driving process of the tracked vehicle, the suspension displacement changes sharply, and the real-time requirement of the active suspension is high. To improve the ride comfort of the vehicle in real time, the difference between the reference suspension output driving force and the model-calculated tension force should be made to tend to 0 as soon as possible, that is, the deviation of the track tension force should be eliminated as soon as possible.

[0037] Example 1:

[0038] In this example, the vehicle's accompanying motion is defined as the vertical motion, pitching motion, and rolling motion generated by the vehicle during driving, and the vehicle's main motion is the vehicle's longitudinal motion and pitching motion. Since the active suspension adjusts the dynamic performance of a single wheel in real time, a 1 / 4 suspension system is used to verify this control method.

[0039] The parameters of the 1 / 4 suspension system are as shown in Table 3 below:

[0040] Table 3 Test parameter table of 1 / 4 suspension system

[0041]

[0042] In this example, the selected road condition is a D-class random road surface. The active suspension system includes: 1. Actuator, 2. Hydraulic pump, 3. Pipeline, 4. Control system. Among them, the control system includes: controller, two pressure sensors, inclination sensor, and cables, etc.

[0043] Active output force The suspension displacement (xb -x w ) can be converted through the balance elbow. The suspension angle of the balance elbow is θ, and the initial angle of the balance elbow is θ0;

[0044] Suspension displacement (x b -x w ) = L * sin(θ - θ0) = 0.36 * sin(θ - θ0);

[0045] Suspension speed

[0046] That is, the active output force U a = 75528 * sin(θ - θ0) + 6840 * cos(θ - θ0) * dθ / dt.

[0047] Here, the fuzzy control method is used to realize the online adjustment of PID parameters. The input of the fuzzy control is the deviation eT. The basic domain is [-30000N, 30000N], and the deviation change rate is [-15000, 15000]. ΔK p 、ΔK i are the adjustment amounts of the two PID parameters P and I. ΔK p The corresponding fuzzy domains are all taken as {-3, -2, -1, 0, 1, 2, 3}. Therefore, the quantization factors are Ke = 0.0001 and Kec = 0.0002; ΔK i The corresponding fuzzy domain is {-0.3, -0.2, -0.1, 0, 0.1, 0.2, 0.3}. The quantization factors are Ke = 0.0002 and Kec = 0.0004, and their fuzzy sets are all {NB, NM, NS, Z, PS, PM, PB}. The fuzzy control tables for the correction amounts of the proportional coefficient and the integral coefficient are given respectively, as shown in Tables 3 and 4. Among them: NB, NM, NS, Z, PS, PM, and PB respectively represent that the fuzzy states of the variables are negative large, negative medium, negative small, zero, positive small, positive medium, and positive large.

[0048] The main - passive contrast test is carried out by using a single - wheel bench to excite the actuator. The root - mean - square value of the pitch angle in the passive condition is 0.78° when the vehicle speed is 30 km / h, and the root - mean - square value of the pitch angle in the active condition is 0.68° when the vehicle speed is 38 km / h. The reduction rate of the pitch angle is 12.8%.

[0049] In summary, the above is only the preferred embodiment of the present invention, and is not used to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0050] For those skilled in the art, it is obvious that the embodiments of the present invention are not limited to the details of the above-described exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the embodiments of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the embodiments of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the embodiments of the present invention. Any reference signs in the claims should not be construed as limiting the claims involved. In addition, it is obvious that the word "comprising" does not exclude other units or steps, and the singular does not exclude the plural. The multiple units, modules or devices stated in the system, apparatus or terminal claims can also be implemented by the same unit, module or device through software or hardware. The words such as first, second, etc. are used to denote names and do not denote any particular order.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present invention and not to limit them. Although the technical solutions of the embodiments of the present invention have been described in detail with reference to the above preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the embodiments of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A constant force output tracking control method for the electro-hydraulic active suspension of a high-speed tracked vehicle, characterized in that, including the following steps: Step 1: According to Newton's second law of motion, establish a 1 / 4 suspension dynamics model, that is, the vehicle dynamics differential equation in the vertical direction of the unsprung mass; Step 2: When the wheel hits a protrusion, the spring compresses, the suspension displacement is negative, the suspension speed is negative, the active force is negative, and the direction is downward. The active suspension acts on the wheel upward, that is, lifts the wheel, and the magnitude of the output active force is the spring force of the suspension plus the damping force of the suspension; when the wheel encounters a depression, the spring stretches, the suspension displacement is positive, the suspension speed is positive, the active force is positive, and the direction is upward. The active suspension acts on the wheel downward, that is, presses the wheel, and the magnitude of the output active force is the spring force of the suspension plus the damping force of the suspension.

2. The control method according to claim 1, characterized in that, After Step 2, it further includes: Step 3: The suspension controller outputs the active force in real time and performs closed-loop PID control; during the driving process of the tracked vehicle, the road surface applies an excitation to the road wheel, causing the torsion bar elastic element to rotate. The elastic element acts on the vehicle body in the reverse direction, and the active suspension outputs a constant force to reduce the influence of spring elastic elements such as the torsion bar on the pitch and vibration of the vehicle body; the suspension controller obtains the magnitude of the ideal active force required by the suspension system through a constant force algorithm, and calculates the reference current of the servo valve at this time according to the relationship between the active force of the system and the servo valve current obtained from the active suspension output force characteristic test. The hydraulic system changes the pressures of the two chambers of the suspension actuator through the servo valve. The controller collects the pressure values of the two chambers, and further calculates the actual output active force value of the actuator, the difference between the real-time suspension output active force and the model-calculated tension force, the change rate of the difference, and the correction amounts of the proportional coefficient and the integral coefficient of the suspension active force output adjustment PID controller; Step 4: Adopt a constant force control algorithm for outer-loop control, and adopt the fuzzy logic algorithm of a fuzzy PID controller for inner-loop closed-loop control. Optimize the PID parameters in real time according to fuzzy rules until the ideal control effect is achieved. At the same time, compare the real-time suspension output active force with the model-calculated tension force, perform fuzzy reasoning according to the deviation and its change rate, obtain the correction amounts of parameters P and I, then obtain the suspension output active force compensation amount, further obtain the servo valve output current compensation amount, and thus achieve the function of real-time adjusting the active force.

3. The control method according to claim 2, wherein The vehicle dynamics differential equation in the vertical direction of the unsprung mass is specifically: where m b is the unsprung mass, k s is the suspension stiffness, x b is the unsprung displacement, x w is the sprung displacement, C s is the suspension damping coefficient, U a is the active control force for suppressing the vertical vibration of the car body. Since the ride comfort of the vehicle is evaluated by the vibration acceleration of the car body, the smaller the acceleration, the better the ride comfort of the vehicle. Therefore, let be 0, then the formula (1) is transformed into: To maintain vehicle ride comfort, i.e., the acceleration of the sprung mass is 0, the magnitude of the target output force of the active suspension is the spring force k of the suspension s (x b -x w ) plus the damping force of the suspension where (x b -x w ) is the suspension displacement, is the suspension speed, and the positive direction is vertically upward.

4. The control method according to claim 2 or 3, characterized in that, The real-time optimization of the PID parameters according to the fuzzy rules is specifically as follows: When the deviation between the suspended output driving force and the model calculated tension force is large, in order to shorten the system response time and avoid overshoot, make K P take a large value, and K I is set to 0; when the deviation is small, in order to further reduce the deviation, prevent overshoot and deterioration of stability, reduce the value of K P ; when the deviation is very small, in order to further eliminate the static error, prevent overshoot and ensure the quick stabilization of the suspended driving force, K I is set to a smaller value; when the deviation is extremely small, to further eliminate the static error, prevent overshoot and ensure the quick stabilization of the suspended driving force, K P is set to continue to decrease, and K I is set to remain unchanged or slightly increase.

5. The control method according to claim 2 or 3, characterized in that, The real-time optimization of the PID parameters according to the fuzzy rules is specifically as follows: When the deviation between the hanging output driving force and the model-calculated tension force and the change rate of the deviation are of the same sign, it indicates that the difference between the current track tension force and the reference track tension force is increasing. To eliminate the tension force deviation as soon as possible, the K P value takes the maximum; When the deviation between the suspended output driving force and the model-calculated tension force and the change rate of the deviation have different signs, the K P value gradually decreases as the deviation decreases.

Images