Control method and system for four-wheel steering mechanism of fire fighting truck

Abstract

A control method and system for a four-wheel steering mechanism of a fire fighting truck comprises the steps that S1, the rotation angle of a steering wheel is received and converted into an input signal; s2, a steering wheel rotation angle signal is converted into a steering driving signal through a PID controller according to the input signal; s3, dynamic characteristic difference compensation is conducted on the steering driving signal through a mechanical transfer function model, and the rotation angle of the motor in the state that the motor is not controlled by the steering ratio is obtained; s4, comparing the rotating angle of the motor in the state of not being controlled by the steering ratio with the rotating angle of the steering wheel, and if the two rotating angles are equal or are within the allowable error range + / -5%, judging that the motor is qualified and entering the next step for processing; on the contrary, error calculation needs to be carried out on the input steering wheel rotation angle, and the steps S2-S4 are repeated; s5, steering ratio control is conducted according to the input steering wheel rotation angle, and the actual rotation angle of the motor is output; and S6, according to the received actual rotation angle of the motor, a four-wheel steering mechanism is used for conducting steering control over wheels.

Description

Technical Field

[0001] The present invention relates to the technical field of steering control of fire trucks, and more specifically, to a control method and system for a four-wheel steering mechanism of a fire truck. Background Art

[0002] As an important tool for emergency rescue, a fire truck must have high mobility, flexibility, and the ability to pass through complex urban environments. Most traditional fire trucks adopt a front-wheel steering design. Although this design is sufficient for most ordinary roads, in narrow and long streets, narrow streets in old urban areas, or in urban tunnel environments, its turning radius is large and the maneuverability is poor, which affects the rapid response and rescue efficiency of the fire truck.

[0003] In order to improve the mobility of fire trucks in narrow spaces and complex environments, four-wheel steering technology has been gradually introduced into the field of fire trucks. Four-wheel steering technology can significantly reduce the turning radius, improve the maneuverability and stability through the coordinated control of four wheels. However, traditional four-wheel steering systems generally have problems such as complex structure, high cost, heavy system weight, and inaccurate operation. And it also requires complex hardware and multiple motor drives to meet the requirements of different wheel steering angles. This not only increases the complexity of the system, but also increases the cost and weight. For a fire truck that has high requirements for speed and flexibility, it may not be the best choice. Especially in some special occasions, such as narrow spaces or areas with dense obstacles, the response speed and accuracy of the four-wheel steering system directly affect the performance of the fire truck.

[0004] Secondly, existing control methods mostly rely on simple closed-loop control strategies and lack intelligent adjustment for different environments and working conditions. For example, when a fire truck is driving in special environments such as complex urban streets or mountain roads, existing control algorithms may not be able to automatically optimize control parameters according to real-time situations, resulting in an unsmooth control experience and even oversteering or understeering phenomena. Therefore, how to improve the intelligence, precision, and adaptability of the four-wheel steering system is an urgent problem to be solved in the current technical field.

[0005] Therefore, in view of the problems existing in the prior art, the present invention proposes a control method for a four-wheel steering mechanism of a fire truck based on PID control and single-motor drive, aiming to improve the response speed, precision, and overall control performance of the four-wheel steering system to better meet the needs of fire trucks in emergency rescue. Summary of the Invention

[0006] The present invention aims to overcome at least one defect (shortcoming) of the above-mentioned prior art, and provides a control method and system for a four-wheel steering mechanism of a fire truck, which improves the response speed, accuracy and overall control performance of the four-wheel steering system, can adjust the steering angle in real time, avoid over-steering or under-steering, and can better meet the needs of fire trucks in emergency rescue.

[0007] The technical solution adopted by the present invention is a control method for a four-wheel steering mechanism of a fire truck, and the method includes the following steps:

[0008] S1: Receive the steering wheel rotation angle and convert it into an input signal;

[0009] S2: Use a PID controller according to the input signal to convert the steering wheel rotation angle signal into a steering drive signal;

[0010] S3: Use a mechanical transfer function model to compensate for the dynamic characteristic differences of the steering drive signal, and obtain the rotation angle of the motor in the state without being controlled by the steering ratio;

[0011] S4: Compare the rotation angle of the motor in the state without being controlled by the steering ratio with the steering wheel rotation angle. If the two are equal or within the error tolerance range of ±5%, it is judged as qualified and proceed to the next step for processing; if the two are not equal and not within the error tolerance range of ±5%, it is judged as unqualified, and it is necessary to calculate the error of the input steering wheel rotation angle and repeat steps S2 - S4;

[0012] S5: Perform steering ratio control according to the input steering wheel rotation angle and output the actual rotation angle of the motor;

[0013] S6: According to the received actual rotation angle of the motor, use the four-wheel steering mechanism to control the steering of the wheels.

[0014] In this application, through the setting of the PID control algorithm and the mechanical transfer function model, the input signal of the steering wheel is converted into the control signal of a single motor, and then the four wheels are driven to rotate according to the preset steering angles, which can dynamically adjust the steering strategy according to the real-time road conditions to ensure the steering accuracy and stability of the fire truck in complex environments. This method not only simplifies the control system of four-wheel steering but also improves the steering accuracy and response speed, enabling the fire truck to drive flexibly in narrow spaces or complex road conditions. The synchronous coordination of the four-wheel steering mechanism also significantly improves the steering ability of the vehicle. Especially when parking, turning around, and driving on narrow roads, it can significantly improve the maneuverability, reduce the turning radius of the vehicle, thus saving operation time and improving the emergency response efficiency. And through relevant processing by the PID control algorithm and the mechanical transfer function model, the rotation angle of the motor in the state without being controlled by the steering ratio is obtained and compared with the rotation angle of the steering wheel, so as to judge whether the input rotation angle of the steering wheel is qualified. If it is qualified, subsequent processing can be carried out to obtain the actual rotation angle of the motor to control the steering of the fire truck. If it is unqualified, error calculation is performed to obtain the qualified rotation angle of the steering wheel, which can realize real-time monitoring of the input signal of the steering wheel, enabling the fire truck to adjust the steering angle in real time and avoid oversteering or understeering.

[0015] Preferably, in the PID controller in step S2, the PID control algorithm is used to adjust the signal, and the formula of the PID control algorithm is as follows:

[0016]

[0017] where, K p is the proportional gain, K i is the integral gain, K d is the derivative gain, and s is the complex frequency variable in the Laplace transform.

[0018] By using the PID control algorithm to adjust the signal, the automatic control of the four-wheel steering mechanism is realized, and the steering angles of the four wheels can be adjusted in real time to ensure the accuracy and stability of steering. The PID controller can effectively suppress unstable phenomena such as overshoot and oscillation that may occur during the steering process, thereby improving the driving safety and stability of the fire truck in complex environments.

[0019] Preferably, in step S3, the construction of the mechanical transfer function model is included, and the steps are as follows:

[0020] S31: Use a second-order differential equation to describe the mechanical motion, perform Laplace transform on it, and introduce the natural frequency and damping coefficient to describe the dynamic characteristics of the mechanical motion to obtain the standard mechanical transfer function model;

[0021] S32: Introduce the transfer coefficient and damping frequency to expand the mechanical transfer function model, thereby constructing the final mechanical transfer function model.

[0022] In the mechanical transfer function model described in this application, the transfer coefficient and damping frequency are also introduced to further expand the model, thereby further adjusting the dynamic characteristics of the mechanical system, compensating for the dynamic characteristic differences of the actuator, optimizing the steering performance, improving the mobility, and making the four-wheel steering system of the fire truck more stable.

[0023] Preferably, in the step S32, the formula of the mechanical transfer function model is:

[0024]

[0025] where K is the transfer coefficient, representing the gain of the system; is the transfer damping coefficient; w n is the transfer natural frequency; is the transfer damping coefficient; w d is the damping frequency, and s is the complex frequency variable in the Laplace transform.

[0026] Preferably, the four-wheel steering mechanism is a single-motor-driven steering mechanism, including:

[0027] A frame for supporting the entire steering mechanism;

[0028] A steering drive module: driven by a single motor, used to provide the driving force for steering;

[0029] A steering control module: connected to the steering drive module, used to convert the driving force into the swing of the Ackermann steering mechanism;

[0030] An Ackermann steering module: including a front-wheel steering component and a rear-wheel steering component, used to control the steering angle of the inner wheel to be greater than that of the outer wheel, where the front-wheel steering component is connected to the steering control module;

[0031] A steering transfer module: connecting the front-wheel steering component and the rear-wheel steering component, used to transfer the steering action of the front wheels to the rear wheels.

[0032] In this application, only one steering motor is used to provide the power source, which simplifies the complexity of the drive system, reduces the costs of the mechanical structure and control system, and at the same time reduces the maintenance difficulty and failure rate, greatly reducing the operation and maintenance costs of the fire truck during long-term operation.

[0033] Preferably, in step S5, the steering ratio is the ratio of the steering angle of the steering wheel to the actual rotation angle of the motor, and the ratio range is set to 12:1 to 18:1.

[0034] By performing steering ratio control, the steering wheel rotation angle is converted into the actual rotation angle of the motor, ensuring the accuracy and stability of steering, improving the steering performance, operation convenience and safety of the fire truck, and providing effective technical support for the intelligence, automation and efficient operation of the fire truck.

[0035] Preferably, the method further includes using Simulink for simulation verification, and optimizing the parameters of the transfer function of the PID controller and the mechanical transfer function model according to the simulation results.

[0036] In order to further verify the reliability and effectiveness of steering, in this application, Simulink is also used for simulation verification, and the parameters of the transfer function of the PID controller and the mechanical transfer function model are optimized according to the simulation results, so that the steering accuracy is higher, and the reliability and effectiveness of the steering system are further improved.

[0037] On the other hand, this application also provides a control system for a four-wheel steering mechanism of a fire truck, and the system includes:

[0038] Input module: used to receive the steering wheel rotation angle and convert it into an input signal;

[0039] PID controller module: used to convert the steering wheel rotation angle signal into a steering drive signal;

[0040] Steering main control module: used to compensate for the dynamic characteristic differences of the steering drive signal by using a mechanical transfer function model to obtain the rotation angle of the motor in the state without steering ratio control;

[0041] Comparison module: used to compare the rotation angle of the motor in the state without steering ratio control with the steering wheel rotation angle. If it is qualified, it enters the steering ratio control module for processing. If it is unqualified, the correction angle is transmitted to the error calculation module through the feedback path for error calculation;

[0042] Error calculation module: used to receive the correction angle transmitted by the feedback path and correct the input steering wheel rotation angle according to the correction angle;

[0043] Steering ratio control module: used to perform steering ratio control according to the input steering wheel rotation angle and output the actual rotation angle of the motor;

[0044] Steering execution module: used to perform steering control on the wheels by using a four-wheel steering mechanism according to the received actual rotation angle of the motor.

[0045] In this system, through the mutual cooperation of different modules, the automatic adjustment and real-time feedback of the four-wheel steering mechanism are realized, enabling the real-time adjustment of the steering angle, avoiding oversteering or understeering, reducing the driver's manual intervention during operation, lowering the operation difficulty, and particularly enhancing the driver's control over the vehicle in emergency situations, allowing the driver to focus more on other important tasks; enhancing the emergency response ability. When the fire truck is performing an emergency task, the rapid steering response and high-precision control contribute to improving the flexibility of the fire truck in urban blocks or complex scenarios. By precisely controlling the four-wheel steering angle, it can help the fire truck quickly change its driving direction, rapidly respond to emergencies, and maximize the operation efficiency.

[0046] Preferably, in the PID controller module, a PID control algorithm is adopted to adjust the signal, and the formula of the PID control algorithm is as follows:

[0047]

[0048] where, K p is the proportional gain, K i is the integral gain, K d is the derivative gain, and s is the complex frequency variable in the Laplace transform.

[0049] In this module, by adopting the PID control algorithm to automatically control the four-wheel steering mechanism, the steering angles of the four wheels can be adjusted in real time, ensuring the accuracy and stability of steering. The PID controller can effectively suppress unstable phenomena such as overshoot and oscillation that may occur during the steering process, thereby enhancing the driving safety and stability of the fire truck in complex environments.

[0050] Preferably, in the steering main control module, a mechanical transfer function is also constructed. By using a second-order differential equation to describe the mechanical motion and performing the Laplace transform on it, and introducing the natural frequency and damping coefficient to describe the dynamic characteristics of the mechanical motion, and then introducing the transfer coefficient and damping frequency to expand the mechanical transfer function model, the final mechanical transfer function model is constructed;

[0051] where, the formula of the mechanical transfer function model is as follows:

[0052]

[0053] where, K is the transfer coefficient, representing the gain of the system; is the transfer damping coefficient; w n is the transfer natural frequency; is the transfer damping coefficient; w d is the damping frequency, and s is the complex frequency variable in the Laplace transform.

[0054] In this module, a mechanical transfer function model is used to optimize the dynamic characteristics of the system, making the steering more accurate and further improving the system performance.

[0055] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0056] 1. Improve steering accuracy and stability: By adopting the PID control algorithm to automatically control the four-wheel steering mechanism, the steering angles of the four wheels can be adjusted in real time, ensuring the accuracy, response speed and stability of steering; the PID controller can effectively suppress unstable phenomena such as overshoot and oscillation that may occur during the steering process, thereby enhancing the driving safety and stability of the fire truck in complex environments.

[0057] 2. Optimize steering performance and enhance maneuverability: This control method enables the fire truck to drive flexibly in narrow spaces or complex road conditions. The synchronous coordination of the four-wheel steering mechanism can greatly improve the steering ability of the vehicle. Especially when parking, turning around and driving on narrow roads, it can significantly improve maneuverability, reduce the turning radius of the vehicle, thereby saving operation time and improving the emergency response efficiency.

[0058] 3. Simplify the drive system: Different from the traditional four-wheel independent drive mode, the present invention provides a power source through a steering motor, simplifies the complexity of the drive system, reduces the costs of the mechanical structure and the control system, and at the same time reduces the maintenance difficulty and failure rate. This design greatly reduces the operation and maintenance costs of the fire truck during long-term operation.

[0059] 4. Automatic control and reduce human intervention: By introducing the PID control algorithm, the present invention can realize the automatic adjustment and real-time feedback of the four-wheel steering mechanism, thereby adjusting the steering angle in real time, avoiding over-steering or under-steering, reducing the human intervention of the driver during operation, reducing the operation difficulty. Especially in emergency situations, it can improve the driver's control of the vehicle and make the driver more focused on other important tasks.

[0060] 5. Enhance the emergency response ability: When the fire truck is performing an emergency task, dynamically adjusting the steering strategy according to the real-time road conditions and making a quick steering response and high-precision control contribute to improving the flexibility of the fire truck in urban blocks or complex scenarios. By precisely controlling the four-wheel steering angles, the present invention can help the fire truck quickly change the driving direction, quickly respond to emergencies, and maximize the operation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] Figure 1 is a flowchart of the method of the present invention.

[0062] Figure 2 is a schematic structural diagram of the four-wheel steering mechanism of the present invention.

[0063] Figure 3Schematic diagram of the Simulink simulation structure of the present invention.

[0064] Figure 4 Simulation result diagram of the present invention.

[0065] Figure 5 Schematic diagram of the system structure of the present invention.

[0066] Description of the drawings: Frame 10; Steering drive module 20; Steering control module 30; Ackermann steering module 40; Front-wheel steering assembly 41; Rear-wheel steering assembly 42; Steering transmission module 50; Telescopic rod assembly 51. Detailed implementation manners

[0067] The drawings of the present invention are only for illustrative purposes and should not be construed as a limitation to the present invention. To better illustrate the following embodiments, some components in the drawings may be omitted, enlarged or reduced, which do not represent the dimensions of the actual products; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0068] Embodiment 1

[0069] In the environment of narrow streets, narrow roads or urban tunnels, the mobility and flexibility of fire trucks are crucial. Traditional fire trucks usually adopt a front-wheel steering design, with a large turning radius, making it difficult to quickly turn in narrow spaces, which affects the rescue efficiency. Taking the urban tunnel environment as an example, assume that a fire truck needs to carry out an emergency rescue in a narrow and curved tunnel. The space in the tunnel is extremely limited. A traditional fire truck may not be able to quickly complete a turn and may even need to reverse multiple times to adjust the direction, wasting precious rescue time. After adopting the four-wheel steering device and control method of this patent, the fire truck can achieve efficient steering through the following steps:

[0070] As Figure 1 shown, this embodiment provides a control method for a four-wheel steering mechanism of a fire truck, and the method includes:

[0071] Step S1: Receive the steering wheel rotation angle and convert it into an input signal; in this embodiment, the range of the steering wheel rotation angle is set to -30° to +30°, and the angular velocity is ±1.5 rad / s;

[0072] Step S2: Use a PID controller to convert the steering wheel rotation angle signal into a steering drive signal according to the input signal;

[0073] Preferably, in the PID controller in step S2, a PID control algorithm is used to adjust the signal, and the formula of the PID control algorithm is:

[0074]

[0075] Among them, K p is the proportional gain, K i is the integral gain, K d is the derivative gain, and s is the complex frequency variable in the Laplace transform.

[0076] Specifically, the derivation process of the formula of the PID control algorithm is as follows:

[0077] (1) Proportional link (P):

[0078] The role of the proportional link is to directly output a control quantity proportional to the error according to the error between the input signal and the target signal.

[0079] Its mathematical expression is: u p (t) = K p ·e(t), where e(t) is the error signal.

[0080] In the frequency domain, the transfer function of the proportional link is: G p (s) = K p .

[0081] (2) Integral link (I):

[0082] The role of the integral link is to eliminate the steady-state error of the system and adjust the output by accumulating the error.

[0083] Its mathematical expression is:

[0084] In the frequency domain, the transfer function of the integral link is:

[0085] (3) Derivative link (D):

[0086] The role of the derivative link is to suppress the overshoot and oscillation of the system and adjust the output by predicting the change trend of the error.

[0087] Its mathematical expression is:

[0088] In the frequency domain, the transfer function of the derivative link is: G d (s) = K d s.

[0089] Thus, the overall transfer function of the PID controller is obtained as:

[0090] Adding the transfer functions of the proportional, integral, and derivative links, the overall transfer function of the PID controller is obtained:

[0091]

[0092] Among them, Kp K is the proportional gain, which is used to quickly respond to changes in the input signal and reduce the steady-state error of the system. It is designed according to the steering ratio of the front and rear wheels and is set to 8 to 12; i K is the integral gain, which is used to eliminate the steady-state error of the system and ensure that the system can maintain precise control after long-term operation. It is set to 0.1~0.3 according to the integral response characteristics of the system; d It is the differential gain, which is used to suppress the overshoot and oscillation of the system and improve the stability of the system. In order to suppress the vibration of the system, it is set to 0.5~1.0.

[0093] By using a PID control algorithm to convert the steering wheel angle signal into a steering drive signal, the system ensures steering accuracy and stability. It also automatically controls the four-wheel steering mechanism, adjusting the steering angle in real time to prevent oversteering or understeering. The PID controller effectively suppresses instabilities such as overshoot and oscillation that may occur during steering, thereby improving the safety and stability of fire trucks in complex environments.

[0094] Step S3: using a mechanical transfer function model to compensate for the dynamic characteristic difference of the steering drive signal to obtain the rotation angle of the motor when it is not controlled by the steering ratio;

[0095] The dynamic characteristics include:

[0096] Inertia: Each component in a mechanical system (such as connecting rods, wheels, etc.) has mass, so it will generate inertial forces during movement.

[0097] Damping: The friction and resistance between moving parts in a mechanical system consume the energy of the system and manifest as damping characteristics.

[0098] Elasticity: The connecting rods and connectors in a mechanical system have a certain degree of elasticity and will deform when subjected to force, which manifests as elastic properties.

[0099] Preferably, step S3 includes constructing a mechanical transfer function model, which comprises the following steps:

[0100] Step S31: using a second-order differential equation to describe the mechanical motion, performing Laplace transform on it, and introducing the natural frequency and damping coefficient to describe the dynamic characteristics of the mechanical motion, thereby obtaining a standard mechanical transfer function model;

[0101] Step S32: introducing the transfer coefficient and the damping frequency to expand the mechanical transfer function model, thereby constructing a final mechanical transfer function model.

[0102] Specifically:

[0103] It is assumed that the motion of the mechanical system can be described by a second-order differential equation:

[0104]

[0105] where m is the equivalent mass of the system; c is the equivalent damping coefficient of the system; k is the equivalent elastic coefficient of the system; F(t) is the input force (i.e., the driving force of the motor); x is the output displacement of the system (i.e., the steering angle of the wheel).

[0106] Taking the Laplace transform of the above differential equation, we get:

[0107] ms 2 X(s) + csX(s) + kX(s) = F(s)

[0108] where X(s) is the Laplace transform of the output displacement; F(s) is the Laplace transform of the input force.

[0109] Rearranging the above equation into the form of a transfer function:

[0110]

[0111] To describe the dynamic characteristics of the system, the natural frequency ω n and the damping coefficient

[0112]

[0113] Substituting the natural frequency and the damping coefficient into the transfer function, we get the transfer function of the second-order system in standard form:

[0114]

[0115] To more accurately describe the dynamic characteristics of the four-wheel steering mechanism, the transfer coefficient K and the damping frequency ω d are introduced to expand the mechanical transfer function model, thus obtaining the following formula:

[0116]

[0117] where: K is the transfer coefficient, representing the gain of the system. and ω d are the transfer damping coefficient and the damping frequency respectively, which are used to further adjust the dynamic characteristics of the system.

[0118] Since the dynamic characteristics of the four-wheel steering mechanism can be described by the transfer function of a second-order system, the formula for the final mechanical transfer function model can be obtained as:

[0119]

[0120] Among them, K is the transfer coefficient, representing the gain of the system, which is usually set to 0.8 - 1.0 according to the rigidity and flexibility design of the mechanical transmission mechanism; is the transfer damping coefficient, set to 0.3 - 0.6; w n is the transfer natural frequency, which is usually set to 0.5 - 0.8 radians per second according to the material and size design of the mechanical transmission mechanism; is the transfer damping coefficient, set to 0.1 - 0.3; w d is the damping frequency, which is usually set to 0.1 - 0.5 radians per second according to the material and size design of the mechanical transmission mechanism; s is the complex frequency variable in the Laplace transform.

[0121] Thus, in the mechanical transfer function model described in this embodiment, by introducing the transfer coefficient and the damping frequency, the model is further expanded, thereby further adjusting the dynamic characteristics of the mechanical system, compensating for the dynamic characteristic differences of the actuator, optimizing the steering performance, enhancing the maneuverability, ensuring that the rotation angle of the motor in the state without steering ratio control is consistent with the rotation angle of the steering wheel, and making the four-wheel steering system of the fire truck more stable.

[0122] Step S4: Compare the rotation angle of the motor in the state without steering ratio control with the rotation angle of the steering wheel. If the two are equal or within the error allowable range of ±5%, it is judged as qualified and proceed to the next step for processing; if the two are not equal and not within the error allowable range of ±5%, it is judged as unqualified, and the error of the input steering wheel rotation angle needs to be calculated and steps S2 - S4 are repeated;

[0123] By comparing the rotation angle of the motor in the state without steering ratio control with the rotation angle of the steering wheel, when the comparison result is qualified, the steering ratio control can be performed on the input steering wheel rotation angle to obtain the actual rotation angle of the motor, and when the comparison result is unqualified, the error calculation is performed to obtain the qualified steering wheel rotation angle, thereby realizing the real-time monitoring of the input signal of the steering wheel, effectively improving the steering accuracy, enabling the fire truck to adjust the steering angle in real time, avoiding oversteering or understeering, ensuring that the fire truck can drive flexibly in narrow spaces or complex road conditions, helping the fire truck quickly change the driving direction, quickly respond to emergencies, and maximizing the operation efficiency.

[0124] Step S5: Perform steering ratio control according to the input steering wheel rotation angle and output the actual rotation angle of the motor;

[0125] Preferably, the steering ratio is the ratio of the steering wheel rotation angle to the actual rotation angle of the motor. In this embodiment, the ratio range of the steering ratio is set to 12:1 to 18:1.

[0126] Steering ratio control is performed according to the steering angle of the steering wheel, and the actual rotation angle of the output motor is output, ensuring the accuracy and stability of steering, ensuring that the front and rear wheels of the fire truck can steer in coordination, the steering angle of the inner wheels is greater than that of the outer wheels, ensuring that the steering angles of all wheels conform to the Ackermann steering theory, enabling the fire truck to turn flexibly in a narrow tunnel, significantly reducing the turning radius, effectively improving the steering performance, operation convenience and safety of the fire truck, and providing effective technical support for the intelligentization, automation and efficient operation of the fire truck.

[0127] Step S6: According to the actual rotation angle of the received motor, use the four-wheel steering mechanism to control the steering of the wheels.

[0128] Preferably, as Figure 2 shown, the four-wheel steering mechanism is a single-motor-driven steering mechanism, including:

[0129] Frame 10, used to support the entire steering mechanism;

[0130] Steering drive module 20: Driven by a single motor, used to provide the driving force for steering;

[0131] Steering control module 30: Connected to the steering drive module 20, used to convert the driving force into the swing of the Ackermann steering mechanism 40;

[0132] Ackermann steering module 40: Includes a front-wheel steering component 41 and a rear-wheel steering component 42, used to control the steering angle of the inner wheels to be greater than that of the outer wheels, where the front-wheel steering component 41 is connected to the steering control module 30;

[0133] Steering transmission module 50: Connects the front-wheel steering component 41 and the rear-wheel steering component 42, used to transmit the steering action of the front wheels to the rear wheels.

[0134] In this embodiment, only one steering motor needs to be equipped in the steering drive module of the fire truck to meet the power source required for vehicle steering. An Ackermann steering module is also equipped, including steering components for the front and rear wheels. The steering action of the front wheels can be transmitted to the rear wheels through the steering transmission module. When the driver turns the steering wheel, the actual rotation angle of the motor obtained after being processed by the PID controller and the mechanical transfer function model is transmitted to the steering drive mechanism to steer the fire truck. The steering drive module 20 provides the driving force, thereby converting the rotational motion of the motor into the steering action of the wheels, enabling the steering control module 30 to drive the front wheels to steer. At the same time, the steering power is transmitted to the rear wheels through the steering transmission module 50 to achieve four-wheel synchronous steering. This structural design significantly reduces the turning radius, enabling the fire truck to turn flexibly in a narrow tunnel and even perform a U-turn in place. At the same time, it simplifies the complexity of the drive system, reduces the costs of the mechanical structure and control system, lowers the maintenance difficulty and failure rate, and greatly reduces the operation and maintenance costs of the fire truck during long-term operation.

[0135] In addition, the steering transmission module 50 further includes a telescopic rod assembly 51. The telescopic rod assembly 51 can achieve dynamic telescoping during the steering process, thereby being able to dynamically adjust the steering force according to the weight of the fire truck and the road conditions, ensuring the effective transmission of the load during the steering process, increasing the strength, and ensuring that the steering motion can be correctly and stably transmitted to the rear wheel steering component 42, thereby ensuring the stability and reliability of the steering motion.

[0136] Further preferably, the method further includes using Simulink for simulation verification. Among them, the schematic diagram of the Simulink simulation structure is as Figure 3 shown. The method is simulated and verified according to this structure to obtain the simulation results, and the parameters of the transfer function of the PID controller and the mechanical transfer function model are optimized according to the results, as Figure 4 shown. The stability of the steering mechanism is verified through simulation, ensuring that there are no obvious oscillations or out-of-control phenomena during the rotation of the steering wheel, and meeting the requirements of the fire truck's emergency steering. In addition, the four-wheel steering mechanism can accurately transmit the steering action of the front wheels to the rear wheels, ensuring the smoothness and flexibility of four-wheel steering.

[0137] To further verify the reliability and effectiveness of the steering, in this embodiment, Simulink is used for simulation verification. The parameters of the transfer function of the PID controller and the mechanical transfer function model are optimized according to the simulation results, making the steering more accurate and further improving the reliability and effectiveness of the steering system.

[0138] The method provided in this embodiment converts the input signal of the steering wheel into the control signal of a single motor through the setting of the PID control algorithm and the mechanical transfer function model, and then drives the four wheels to rotate according to the preset steering angles. This method not only simplifies the control system of four-wheel steering, but also improves the steering accuracy and response speed, enabling the fire truck to drive flexibly in narrow spaces or complex road conditions. The synchronous coordination of the four-wheel steering mechanism can greatly improve the steering ability of the vehicle, especially when parking, turning around, and driving on narrow roads, it can significantly improve the maneuverability, reduce the turning radius of the vehicle, thereby saving operation time and improving the emergency response efficiency.

[0139] Embodiment 2

[0140] This embodiment provides a control system for a four-wheel steering mechanism of a fire truck, as Figure 5 shown. In this system, the input module is sequentially connected to the error calculation module, the PID controller module, the steering main control module, the comparison module, the steering ratio control module, and the steering execution module. The comparison module and the error calculation module are also connected through a feedback path; where:

[0141] Input module: It is used to receive the steering angle of the steering wheel and convert it into an input signal;

[0142] PID controller module: It is used to convert the steering angle signal of the steering wheel into a steering drive signal;

[0143] Steering main control module: It is used to compensate for the dynamic characteristic differences of the steering drive signal by using the mechanical transfer function model to obtain the rotation angle of the motor in the state without being controlled by the steering ratio;

[0144] Comparison module: It is used to compare the rotation angle of the motor in the state without being controlled by the steering ratio with the steering angle of the steering wheel. If it is qualified, it will enter the steering ratio control module for processing. If it is unqualified, the correction angle will be transmitted to the error calculation module through the feedback path for error calculation;

[0145] Error calculation module: It is used to receive the correction angle transmitted by the feedback path and correct the input steering angle of the steering wheel according to the correction angle;

[0146] Steering ratio control module: It is used to perform steering ratio control according to the input steering angle of the steering wheel and output the actual rotation angle of the motor;

[0147] Steering execution module: It is used to perform steering control on the wheels by using the four-wheel steering mechanism according to the received actual rotation angle of the motor;

[0148] In this system, the automatic adjustment and real-time feedback of the four-wheel steering mechanism are achieved through the mutual cooperation of different modules, reducing the human intervention of the driver during operation, lowering the operation difficulty. Especially in emergency situations, it can improve the driver's control over the vehicle, enabling the driver to focus more on other important tasks; enhancing the emergency response ability. When the fire truck is performing an emergency task, it can dynamically adjust the steering strategy according to the real-time road conditions, ensuring the steering accuracy and stability of the fire truck in complex environments, enabling rapid steering response and high-precision control, which helps to improve the flexibility of the fire truck in urban blocks or complex scenarios. By precisely controlling the four-wheel steering angles, it can help the fire truck quickly change its driving direction, rapidly respond to emergencies, and maximize the operation efficiency.

[0149] Preferably, in the PID controller module, a PID control algorithm is adopted to adjust the signal, where the formula of the PID control algorithm is:

[0150]

[0151] where, K p is the proportional gain, K i is the integral gain, K d is the derivative gain, and s is the complex frequency variable in the Laplace transform.

[0152] In this module, by adopting the PID control algorithm to automatically control the four-wheel steering mechanism, it can adjust the steering angles of the four wheels in real time, ensuring the accuracy and stability of steering. The PID controller can effectively suppress unstable phenomena such as overshoot and oscillation that may occur during the steering process, thereby enhancing the driving safety and stability of the fire truck in complex environments.

[0153] Preferably, in the steering main control module, a mechanical transfer function is also constructed. By using a second-order differential equation to describe the mechanical motion and performing Laplace transform on it, and introducing the natural frequency and damping coefficient to describe the dynamic characteristics of the mechanical motion, and then introducing the transfer coefficient and damping frequency to expand the mechanical transfer function model, thus obtaining the final mechanical transfer function model;

[0154] where, the formula of the mechanical transfer function model is:

[0155]

[0156] where, K is the transfer coefficient, representing the gain of the system; is the transfer damping coefficient; w n is the transfer natural frequency; is the transfer damping coefficient; w d is the damping frequency, and s is the complex frequency variable in the Laplace transform.

[0157] In this module, a mechanical transfer function model is used to optimize the dynamic characteristics of the system, making the steering accuracy higher and further improving the system performance. The rotation angle of the motor in the state without steering ratio control is obtained through the mechanical transfer function model, and it is compared with the steering wheel rotation angle in the steering ratio control module to determine whether the input steering wheel rotation angle is qualified. If it is qualified, subsequent processing can be carried out to obtain the actual rotation angle of the motor to control the steering of the fire truck. If it is unqualified, the correction angle is input into the error calculation module for error calculation to obtain a qualified steering wheel rotation angle, thereby realizing real-time monitoring of the input signal of the steering wheel, enabling the fire truck to adjust the steering angle in real time, and avoiding over-steering or under-steering. Finally, the actual rotation angle of the motor obtained is used by the steering execution module to execute the steering of the fire truck through a four-wheel steering mechanism, so that the turning radius of the fire truck in narrow sections such as tunnels is greatly reduced, and it can quickly complete the steering operation in a very limited space, effectively improving the driving safety and stability of the fire truck in complex environments and enhancing the rescue efficiency.

[0158] Preferably, a simulation verification module is also included in this system, and simulation verification is carried out through Simulink of Matlab. Among them, the schematic diagram of the simulink simulation structure is as Figure 3 shown. First, the input module is connected to the comparison and error calculation module. Then, the proportional gain K p , integral gain K i , and derivative gain K d are input into the PID controller module for processing, and then connected to the steering main control module for optimization. At the same time, the steering main control module receives the parameter data of the transfer coefficient K, transfer damping coefficient transfer natural frequency w n , transfer damping coefficient , and transfer damping frequency w d . Among them, in the simulation, the transfer coefficient K is taken as 0.95. Then, it is respectively connected to the comparison and error calculation module and the steering ratio control module to compare the rotation angle of the motor in the state without steering ratio control with the steering wheel rotation angle. Then, according to the comparison result, it is judged whether error calculation is needed, and then the steering ratio control module is used for steering ratio control, so that the obtained actual rotation angle of the motor is input into the steering execution module for steering processing. At the same time, the simulation result schematic diagram as Figure 4 is output. It can be seen from the figure that there is no obvious oscillation or out-of-control phenomenon in the system during the rotation of the steering wheel. The stability of this system is high, which can meet the requirements of the fire truck's emergency steering, and the system can accurately transfer the steering action of the front wheels to the rear wheels to ensure the smoothness and flexibility of four-wheel steering.

[0159] Obviously, the above-mentioned embodiments of the present invention are merely examples for clearly illustrating the technical solutions of the present invention, rather than limitations on the specific implementation manners of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the claims of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A control method for a four-wheel steering mechanism of a fire truck, characterized in that, The method includes the following steps: S1: Receive the steering wheel rotation angle and convert it into an input signal; S2: Use a PID controller according to the input signal to convert the steering wheel rotation angle signal into a steering drive signal; S3: Use a mechanical transfer function model to compensate for the dynamic characteristic differences of the steering drive signal and obtain the rotation angle of the motor in the state without steering ratio control; S4: Compare the rotation angle of the motor in the state without steering ratio control with the steering wheel rotation angle. If the two are equal or within the error tolerance range of ±5%, it is judged as qualified and proceed to the next step for processing; if the two are not equal and not within the error tolerance range of ±5%, it is judged as unqualified, and the error of the input steering wheel rotation angle needs to be calculated and steps S2 - S4 are repeated; S5: Perform steering ratio control according to the input steering wheel rotation angle and output the actual rotation angle of the motor; S6: According to the actual rotation angle of the received motor, use a four-wheel steering mechanism to control the steering of the wheels.

2. The control method of a four-wheel steering mechanism of a fire truck according to claim 1, characterized in that, In the PID controller described in step S2, it includes using a PID control algorithm to adjust the signal, and the formula of the PID control algorithm is: Among them, K p is the proportional gain, K i is the integral gain, K d is the derivative gain, and s is the complex frequency variable in the Laplace transform.

3. The control method of a four-wheel steering mechanism of a fire truck according to claim 1, characterized in that, In step S3, it includes the construction of a mechanical transfer function model, and the steps are as follows: S31: Use a second-order differential equation to describe the mechanical motion, perform Laplace transform on it, and introduce the natural frequency and damping coefficient to describe the dynamic characteristics of the mechanical motion to obtain a standard mechanical transfer function model; S32: Introduce the transfer coefficient and damping frequency to expand the mechanical transfer function model, thereby constructing the final mechanical transfer function model.

4. The control method of a four-wheel steering mechanism of a fire truck according to claim 3, characterized in that, In step S32, the formula of the mechanical transfer function model is: Among them, K is the transfer coefficient, representing the gain of the system; ζ is the transfer damping coefficient; w n is the transfer natural frequency; ζ n is the transfer damping coefficient; w d is the damping frequency, and s is the complex frequency variable in the Laplace transform.

5. The control method of a four-wheel steering mechanism of a fire truck according to claim 1, characterized in that, The four-wheel steering mechanism is a single-motor-driven steering mechanism, including: A frame for supporting the entire steering mechanism; A steering drive module: driven by a single motor, used to provide the driving force for steering; A steering control module: connected to the steering drive module, used to convert the driving force into the swing of an Ackermann steering mechanism; An Ackermann steering module: including a front-wheel steering component and a rear-wheel steering component, used to control the steering angle of the inner wheel to be greater than that of the outer wheel, and the front-wheel steering component is connected to the steering control module; A steering transfer module: connecting the front-wheel steering component and the rear-wheel steering component, used to transfer the steering action of the front wheels to the rear wheels.

6. A control method for a four-wheel steering mechanism of a fire truck according to any one of claims 1-5, characterized in that, In step S5, the steering ratio is the ratio of the steering wheel rotation angle to the actual rotation angle of the motor, and its ratio range is from 12:1 to 18:

1.

7. A control method for a four-wheel steering mechanism of a fire truck according to any one of claims 1-5, characterized in that, The method further includes using Simulink for simulation verification and optimizing the parameters of the transfer function of the PID controller and the mechanical transfer function model according to the simulation results.

8. A control system for a four-wheel steering mechanism of a fire truck, characterized in that, The system includes: An input module: used to receive the steering wheel rotation angle and convert it into an input signal; A PID controller module: used to convert the steering wheel rotation angle signal into a steering drive signal; A steering main control module: used to use a mechanical transfer function model to compensate for the dynamic characteristic differences of the steering drive signal and obtain the rotation angle of the motor in the state without steering ratio control; Comparison module: used to compare the rotation angle of the motor in the state without steering ratio control with the steering wheel rotation angle. If qualified, it enters the steering ratio control module for processing. If unqualified, the correction angle is transmitted to the error calculation module through the feedback path for error calculation; Error calculation module: used to receive the correction angle transmitted by the feedback path and correct the input steering wheel rotation angle according to the correction angle; Steering ratio control module: used to perform steering ratio control according to the input steering wheel rotation angle and output the actual rotation angle of the motor; Steering execution module: used to perform steering control on the wheels by using a four-wheel steering mechanism according to the received actual rotation angle of the motor.

9. The control system of a four-wheel steering mechanism for a fire truck according to claim 8, characterized in that, In the PID controller module, a PID control algorithm is used to adjust the signal, and the formula of the PID control algorithm is: Among them, K p is the proportional gain, K i is the integral gain, K d is the derivative gain, and s is the complex frequency variable in the Laplace transform.

10. The control system of a four-wheel steering mechanism for a fire truck according to claim 8, characterized in that, In the steering main control module, a mechanical transfer function is also constructed. The mechanical motion is described by using a second-order differential equation and Laplace transformed. At the same time, the natural frequency and damping coefficient are introduced to describe the dynamic characteristics of the mechanical motion. Then, the transfer coefficient and damping frequency are introduced to expand the mechanical transfer function model, so as to construct the final mechanical transfer function model; Among them, the formula of the mechanical transfer function model is: Among them, K is the transfer coefficient, representing the gain of the system; ζ is the transfer damping coefficient; w n is the transfer natural frequency; ζ n is the transfer damping coefficient; w d is the damping frequency, and s is the complex frequency variable in the Laplace transform.

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