A control method and system for a fire truck four-wheel steering mechanism

Abstract

A control method and system of a fire truck four-wheel steering mechanism, comprising: S1: receiving the steering wheel rotation angle and converting it into an input signal; S2: using a PID controller to convert the steering wheel rotation angle signal into a steering drive signal according to the input signal; S3: using a mechanical transfer function model to compensate for the dynamic characteristic difference of the steering drive signal, obtaining the rotation angle of the motor under the state of not being controlled by the steering ratio; S4: comparing the rotation angle of the motor under the state of not being controlled by the steering ratio with the steering wheel rotation angle, if they are equal or within the error allowable interval ±5%, it is judged to be qualified to enter the next step for processing; otherwise, the input steering wheel rotation angle needs to be calculated for error and steps S2-S4 are repeated; S5: controlling the steering ratio according to the input steering wheel rotation angle, and outputting the actual rotation angle of the motor; S6: using the four-wheel steering mechanism to control the steering of the wheels according to the received actual rotation angle of the motor.

Description

Technical Field

[0001] This invention relates to the field of fire truck steering control technology, and more specifically, to a control method and system for a four-wheel steering mechanism of a fire truck. Background Technology

[0002] As an essential tool for emergency rescue, fire trucks must possess high mobility, flexibility, and the ability to navigate complex urban environments. Most traditional fire trucks employ a front-wheel steering design. While this design is sufficient for most ordinary roads, its large turning radius and poor maneuverability in narrow streets, long and narrow alleys in old urban areas, or in urban tunnels, negatively impact the fire truck's rapid response and rescue efficiency.

[0003] To improve the maneuverability of fire trucks in confined spaces and complex environments, four-wheel steering technology has been gradually introduced into the fire truck field. Four-wheel steering, through the coordinated control of all four wheels, can significantly reduce the turning radius and improve handling and stability. However, traditional four-wheel steering systems generally suffer from problems such as complex structure, high cost, heavy system weight, and insufficient operational precision. Furthermore, they require complex hardware and multiple motor drives to meet the needs of different wheel steering angles. This not only increases the system's complexity but also raises costs and weight, which may not be the optimal choice for vehicles like fire trucks that require high speed and agility. Especially in special situations, such as confined 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 largely rely on simple closed-loop control strategies, lacking intelligent adjustments for different environments and operating conditions. For example, when fire trucks are driving in complex urban streets or mountainous environments, existing control algorithms may not be able to automatically optimize control parameters based on real-time conditions, resulting in a less smooth driving experience and even oversteering or understeering. Therefore, improving the intelligence, precision, and adaptability of four-wheel steering systems is a pressing challenge in this technological field.

[0005] Therefore, in view of the problems existing in the prior art, this invention proposes a control method for the four-wheel steering mechanism of a fire truck based on PID control and single motor drive, which aims to improve the response speed, accuracy and overall control performance of the four-wheel steering system, so as 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 of the defects (deficiencies) of the prior art and provide 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 oversteering or understeering, and can better meet the needs of fire trucks in emergency rescue.

[0007] The technical solution adopted in this invention is a control method for a four-wheel steering mechanism of a fire truck, the method comprising the following steps:

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

[0009] S2: A PID controller is used to convert the steering wheel rotation angle signal into a steering drive signal based on the input signal;

[0010] S3: The mechanical transfer function model is used to compensate for the dynamic characteristic difference of the steering drive signal to obtain the rotation angle of the motor when it is not under steering ratio control.

[0011] 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%, the motor is deemed qualified and proceeds to the next step. If the two are not equal and are not within the error allowable range of ±5%, the motor is deemed unqualified and the error of the input steering wheel rotation angle needs to be calculated and steps S2-S4 are repeated.

[0012] S5: Controls the steering ratio based on the input steering wheel rotation angle and outputs the actual rotation angle of the motor;

[0013] S6: Based on the actual rotation angle of the motor received, the four-wheel steering mechanism is used to control the steering of the wheels.

[0014] In this application, by setting a PID control algorithm and a mechanical transfer function model, the input signal of the steering wheel is converted into a control signal of a single motor, which in turn drives the four wheels to rotate at a preset steering angle. This allows for dynamic adjustment of the steering strategy based on real-time road conditions, ensuring the steering accuracy and stability of the fire truck in complex environments. This method not only simplifies the four-wheel steering control system but also improves steering accuracy and response speed, enabling fire trucks to maneuver flexibly in narrow spaces or complex road conditions. The synchronous coordination of the four-wheel steering mechanism also significantly improves the vehicle's steering ability, especially when parking, making U-turns, and driving on narrow roads, significantly improving maneuverability, reducing the vehicle's turning radius, thereby saving operation time and improving emergency response efficiency. Furthermore, by using PID control algorithms and mechanical transfer function models, the method obtains the motor's rotation angle in the uncontrolled steering ratio state and compares it with the steering wheel rotation angle to determine whether the input steering wheel rotation angle is qualified. If qualified, subsequent processing can be performed to obtain the motor's actual rotation angle to control the fire truck's steering; if unqualified, error calculation is performed to obtain the qualified steering wheel rotation angle. This allows for real-time monitoring of the steering wheel input signal, enabling the fire truck to adjust the steering angle in real time and avoid oversteering or understeering.

[0015] Preferably, the PID controller in step S2 includes using a PID control algorithm to adjust the signal, wherein the formula of the PID control algorithm is:

[0016]

[0017] in, For proportional gain, For integral gain, For differential gain, is the complex frequency variable in the Laplace transform.

[0018] By employing a PID control algorithm to adjust signals, the four-wheel steering mechanism is automatically controlled, enabling real-time adjustment of the steering angles of all four wheels to ensure steering accuracy and stability. The PID controller effectively suppresses instability phenomena such as overshoot and oscillation that may occur during steering, thereby improving the safety and stability of fire trucks in complex environments.

[0019] Preferably, step S3 includes constructing a mechanical transfer function model, the steps of which are as follows:

[0020] S31: The mechanical motion is described by a second-order differential equation and subjected to a Laplace transform. Natural frequency and damping coefficient are introduced to describe the dynamic characteristics of the mechanical motion, resulting in a standard mechanical transfer function model.

[0021] S32: The mechanical transfer function model is extended by introducing the transfer coefficient and damping frequency, thereby constructing the final mechanical transfer function model.

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

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

[0024]

[0025] in, The transfer coefficient represents the system gain; The damping coefficient; To transmit natural frequencies; The transmission damping coefficient; For the damping frequency, is the complex frequency variable in the Laplace transform.

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

[0027] The chassis supports the entire steering mechanism;

[0028] Steering drive module: Driven by a single motor, it provides the driving force for steering;

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

[0030] Ackermann steering module: includes a front wheel steering assembly and a rear wheel steering assembly, used to control the steering angle of the inner wheel to be greater than that of the outer wheel, wherein the front wheel steering assembly is connected to the steering control module;

[0031] Steering transmission module: Connects the front wheel steering assembly and the rear wheel steering assembly, and is used to transmit the steering action of the front wheels to the rear wheels.

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

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

[0034] By controlling the steering ratio, 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, ease of operation and safety of the fire truck, and providing effective technical support for the intelligent, automated and efficient operation of the fire truck.

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

[0036] To further verify the reliability and effectiveness of the steering, Simulink was also used for simulation verification in this application. Based on the simulation results, the parameters of the PID controller transfer function and the mechanical transfer function model were optimized, resulting in higher steering accuracy and further improving the reliability and effectiveness of the steering system.

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

[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 dynamic characteristic differences in steering drive signals using a mechanical transfer function model, and to obtain the rotation angle of the motor when it is not under steering ratio control;

[0041] Comparison module: Used to compare the rotation angle of the motor without steering ratio control with the rotation angle of the steering wheel. If they are compatible, the motor will be processed in the steering ratio control module. If they are not compatible, the correction angle will be 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 to correct the input steering wheel rotation angle according to the correction angle;

[0043] Steering ratio control module: used to control the steering ratio based on the input steering wheel rotation angle, and outputs the actual rotation angle of the motor;

[0044] Steering execution module: Used to control the steering of the wheels using the four-wheel steering mechanism based on the actual rotation angle of the motor received.

[0045] This system achieves automatic adjustment and real-time feedback of the four-wheel steering mechanism through the cooperation of different modules. This allows for real-time adjustment of the steering angle, preventing oversteering or understeering, reducing driver intervention, and lowering operational difficulty. Especially in emergency situations, it enhances driver control, allowing them to focus more on other important tasks. It also strengthens emergency response capabilities; when fire trucks are performing emergency missions, rapid steering response and high-precision control improve their maneuverability in urban areas or complex scenarios. Precise control of the four-wheel steering angle helps fire trucks quickly change direction, respond swiftly to emergencies, and maximize operational efficiency.

[0046] Preferably, the PID controller module includes a PID control algorithm for signal adjustment, wherein the formula of the PID control algorithm is:

[0047]

[0048] in, For proportional gain, For integral gain, For differential gain, is the complex frequency variable in the Laplace transform.

[0049] In this module, a PID control algorithm is used to automatically control the four-wheel steering mechanism, enabling real-time adjustment of the steering angles of all four wheels to ensure steering accuracy and stability. The PID controller effectively suppresses instability phenomena such as overshoot and oscillation that may occur during steering, thereby improving the driving safety and stability of the fire truck in complex environments.

[0050] Preferably, the steering main control module further includes constructing a mechanical transfer function model, which describes the mechanical motion by using a second-order differential equation and performing a Laplace transform on it, while 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 extend the mechanical transfer function model, thereby constructing the final mechanical transfer function model.

[0051] The formula for the mechanical transfer function model is as follows:

[0052]

[0053] in, The transfer coefficient represents the system gain; The damping coefficient; To transmit natural frequencies; The transmission damping coefficient; For the damping frequency, is the complex frequency variable in the Laplace transform.

[0054] In this module, the mechanical transfer function model is used to optimize the dynamic characteristics of the system, resulting in higher steering accuracy and further improving system performance.

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

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

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

[0058] 3. Simplified Drive System: Unlike traditional four-wheel independent drive systems, this invention uses a single steering motor as the power source, simplifying the drive system's complexity, reducing the cost of mechanical structures and control systems, and lowering maintenance difficulty and failure rate. This design significantly reduces the long-term operation and maintenance costs of fire trucks.

[0059] 4. Automated control, reducing human intervention: By introducing the PID control algorithm, this invention can realize automatic adjustment and real-time feedback of the four-wheel steering mechanism, thereby adjusting the steering angle in real time, avoiding oversteering or understeering, reducing human intervention by the driver during operation, reducing the difficulty of operation, and especially improving the driver's control over the vehicle in emergency situations, allowing him to focus more on other important tasks.

[0060] 5. Enhanced Emergency Response Capabilities: When fire trucks are performing emergency missions, dynamically adjusting steering strategies based on real-time road conditions and providing rapid steering response and high-precision control helps improve the fire truck's maneuverability in urban areas or complex scenarios. By precisely controlling the four-wheel steering angle, this invention can help fire trucks quickly change direction, respond swiftly to emergencies, and maximize operational efficiency. Attached Figure Description

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

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

[0063] Figure 3 This is a schematic diagram of the Simulink simulation structure of the present invention.

[0064] Figure 4 The figure shows the simulation results of this invention.

[0065] Figure 5 This is a schematic diagram of the system structure of the present invention.

[0066] Figure descriptions: 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

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

[0068] Example 1

[0069] In narrow streets, confined spaces, or urban tunnels, the maneuverability and flexibility of fire trucks are crucial. Traditional fire trucks typically employ front-wheel steering, resulting in a large turning radius that makes it difficult to maneuver quickly in confined spaces, impacting rescue efficiency. Take an urban tunnel environment as an example: suppose a fire truck needs to conduct an emergency rescue in a narrow and winding tunnel. The space inside the tunnel is extremely limited, and traditional fire trucks may not be able to complete turns quickly, even requiring multiple reversing maneuvers to adjust direction, wasting valuable rescue time. However, with the four-wheel steering device and control method of this patent, the fire truck can achieve efficient steering through the following steps:

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

[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: Based on the input signal, a PID controller is used to convert the steering wheel rotation angle signal into a steering drive signal;

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

[0074]

[0075] in, For proportional gain, For integral gain, For differential gain, is the complex frequency variable in the Laplace transform.

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

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

[0078] The function of the proportional element is to directly output a control quantity that is proportional to the error between the input signal and the target signal.

[0079] Its mathematical expression is: ,in It is an error signal.

[0080] In the frequency domain, the transfer function of the proportional element is: .

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

[0082] The role of the integrator 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 integrator is: .

[0085] (3) Differential element (D):

[0086] The role of the differential element is to suppress system overshoot and oscillation, and to adjust the output by predicting the trend of error changes.

[0087] Its mathematical expression is: .

[0088] In the frequency domain, the transfer function of the differentiating element is: .

[0089] Therefore, the overall transfer function of the PID controller is:

[0090] Adding the transfer functions of the proportional, integral, and derivative components together, we obtain the overall transfer function of the PID controller:

[0091]

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

[0093] By employing a PID control algorithm, the steering wheel angle signal is converted into a steering drive signal, ensuring steering accuracy and stability. Simultaneously, it can automatically control the four-wheel steering mechanism, adjusting the steering angle of each wheel in real time to prevent oversteering or understeering. The PID controller effectively suppresses instability phenomena 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: Use the mechanical transfer function model to compensate for the dynamic characteristic difference of the steering drive signal, and obtain the rotation angle of the motor in the state without steering ratio control.

[0095] The dynamic characteristics include:

[0096] Inertia: The components in a mechanical system (such as connecting rods, wheels, etc.) have mass, and therefore generate inertial forces during motion.

[0097] Damping: Friction and resistance exist between moving parts in a mechanical system. These resistances consume the system's energy and are manifested as damping characteristics.

[0098] Elasticity: Links and connecting parts in a mechanical system have a certain degree of elasticity and will deform when subjected to force, exhibiting elastic characteristics.

[0099] Preferably, step S3 includes constructing a mechanical transfer function model, the steps of which are as follows:

[0100] Step S31: Use second-order differential equations to describe mechanical motion and perform Laplace transform on them. At the same time, introduce natural frequency and damping coefficient to describe the dynamic characteristics of mechanical motion to obtain a standard mechanical transfer function model.

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

[0102] Specifically:

[0103] Suppose the motion of the mechanical system can be described by a second-order differential equation:

[0104] in, For the equivalent quality of the system; The equivalent damping coefficient of the system; The equivalent elastic coefficient of the system; This is the input force (i.e., the driving force of the motor). This is the system's output displacement (i.e., the steering angle of the wheels).

[0105] Taking the Laplace transform of the above differential equation, we get:

[0106] in, The Laplace transform of the output displacement; The Laplace transform of the input force.

[0107] Rearranging the above equations into the form of a transfer function:

[0108]

[0109] To describe the dynamic characteristics of the system, a natural frequency is introduced. and damping coefficient :

[0110]

[0111]

[0112] Substituting the natural frequency and damping coefficient into the transfer function, we obtain the standard form of the second-order system transfer function:

[0113] To more accurately describe the dynamic characteristics of a four-wheel steering mechanism, a transmission coefficient is introduced. and damping frequency By extending the mechanical transfer function model, we obtain the following formula:

[0114]

[0115] in: is the transfer coefficient, representing the system gain. and These are the transmission damping coefficient and damping frequency, respectively, used to further adjust the dynamic characteristics of the system.

[0116] Since the dynamic characteristics of a 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 follows:

[0117]

[0118] in, The transfer factor represents the system gain, and is typically set to 0.8~1.0 depending on the rigidity and flexibility design of the mechanical transmission mechanism. The damping coefficient is set to 0.3~0.6; To transmit natural frequencies, the frequency is typically set to 0.5 to 0.8 radians per second, depending on the material and size design of the mechanical transmission mechanism. The transmission damping coefficient is set to 0.1~0.3; The damping frequency is typically set to 0.1~0.5 radians / second, depending on the material and dimensions of the mechanical transmission mechanism. is the complex frequency variable in the Laplace transform.

[0119] Therefore, in the mechanical transfer function model described in this embodiment, the model is further extended by introducing the transfer coefficient and damping frequency, thereby further adjusting the dynamic characteristics of the mechanical system, compensating for the differences in the dynamic characteristics of the actuator, optimizing the steering performance, improving maneuverability, and 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, making the four-wheel steering system of the fire truck more stable.

[0120] 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%, the motor is deemed qualified and proceeds to the next step. If the two are not equal and are not within the error allowable range of ±5%, the motor is deemed unqualified and the input steering wheel rotation angle needs to be calculated for error and steps S2-S4 need to be repeated.

[0121] By comparing the motor's rotation angle without steering ratio control with the steering wheel's rotation angle, steering ratio control is applied to the input steering wheel rotation angle only when the comparison result is satisfactory to obtain the motor's actual rotation angle. If the comparison result is unsatisfactory, error calculation is performed to obtain the satisfactory steering wheel rotation angle. This enables real-time monitoring of the steering wheel's input signal, effectively improving steering accuracy. This allows fire trucks to adjust their steering angle in real time, avoiding oversteering or understeering, ensuring that fire trucks can maneuver flexibly in narrow spaces or complex road conditions. It also helps fire trucks quickly change direction, respond swiftly to emergencies, and maximize operational efficiency.

[0122] Step S5: Control the steering ratio based on the input steering wheel rotation angle, and output the actual rotation angle of the motor;

[0123] 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 steering ratio is set to a range of 12:1 to 18:1.

[0124] Steering ratio control based on steering wheel rotation angle outputs the actual rotation angle of the motor, ensuring steering accuracy and stability. This ensures that the front and rear wheels of the fire truck can steer in coordination, with the inner wheel's steering angle being greater than the outer wheel's. This guarantees that the steering angle of all wheels conforms to Ackermann steering theory, enabling the fire truck to turn flexibly in narrow tunnels, significantly reducing the turning radius. This effectively improves the fire truck's steering performance, ease of operation, and safety, providing effective technical support for the intelligent, automated, and efficient operation of fire trucks.

[0125] Step S6: Based on the received actual rotation angle of the motor, use the four-wheel steering mechanism to control the steering of the wheels.

[0126] Preferably, such as Figure 2 As shown, the four-wheel steering mechanism is a single-motor driven steering mechanism, comprising:

[0127] The frame 10 supports the entire steering mechanism;

[0128] Steering drive module 20: Driven by a single motor, it provides steering force;

[0129] Steering control module 30: connected to the steering drive module 20, used to convert the driving force into the oscillation of the Ackermann steering mechanism 40;

[0130] Ackermann steering module 40: includes a front wheel steering assembly 41 and a rear wheel steering assembly 42, used to control the steering angle of the inner wheel to be greater than that of the outer wheel, wherein the front wheel steering assembly 41 is connected to the steering control module 30;

[0131] Steering transmission module 50: connects the front wheel steering assembly 41 and the rear wheel steering assembly 42, and is used to transmit the steering action of the front wheels to the rear wheels.

[0132] In this embodiment, the fire truck's steering drive module only needs to be equipped with a single steering motor to provide the power source required for vehicle steering. It also includes an Ackermann steering module, comprising steering components for the front and rear wheels. The steering transmission module transmits the steering motion of the front wheels to the rear wheels. When the driver turns the steering wheel, the actual rotation angle of the motor is obtained after processing by the PID controller and mechanical transfer function model, and then transmitted to the steering drive mechanism to steer the fire truck. The steering drive module 20 provides the driving force, converting the motor's rotational motion into wheel steering motion. This allows the steering control module 30 to drive the front wheels to steer, while the steering transmission module 50 transmits the steering power to the rear wheels, achieving synchronized four-wheel steering. This structural design significantly reduces the turning radius, enabling the fire truck to turn flexibly in narrow tunnels and even make U-turns. It also simplifies the complexity of the drive system, reduces the cost of the mechanical structure and control system, lowers maintenance difficulty and failure rate, and greatly reduces the long-term operation and maintenance costs of the fire truck.

[0133] In addition, the steering transmission module 50 also includes a telescopic rod assembly 51, which can dynamically extend and retract during the steering process, thereby dynamically adjusting the steering force according to the weight of the fire truck and road conditions, ensuring effective load transmission during the steering process, increasing strength, and ensuring that the steering motion can be correctly and stably transmitted to the rear wheel steering assembly 42, thereby ensuring the stability and reliability of the steering motion.

[0134] More preferably, the method further includes simulation verification using Simulink, wherein a schematic diagram of the Simulink simulation structure is shown below. Figure 3 As shown, the method is simulated and verified based on this structure to obtain simulation results. Based on these results, the parameters of the PID controller transfer function and mechanical transfer function models are optimized, as follows: Figure 4 As shown, the stability of the steering mechanism was verified through simulation, ensuring that there was no obvious oscillation or loss of control during the steering wheel rotation, and meeting the emergency steering requirements of fire trucks. 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.

[0135] To further verify the reliability and effectiveness of the steering, this embodiment uses Simulink for simulation verification. Based on the simulation results, the parameters of the PID controller transfer function and the mechanical transfer function model are optimized, resulting in higher steering accuracy and further improving the reliability and effectiveness of the steering system.

[0136] The method provided in this embodiment converts the input signal from the steering wheel into a control signal for a single motor through a PID control algorithm and a mechanical transfer function model, thereby driving the four wheels to rotate at a preset steering angle. This method not only simplifies the four-wheel steering control system but also improves steering accuracy and response speed, enabling fire trucks to maneuver flexibly in narrow spaces or complex road conditions. The synchronous coordination of the four-wheel steering mechanism significantly improves the vehicle's steering ability, especially when parking, making U-turns, and driving on narrow roads, significantly improving maneuverability, reducing the vehicle's turning radius, thereby saving operation time and improving emergency response efficiency.

[0137] Example 2

[0138] This embodiment provides a control system for a four-wheel steering mechanism of a fire truck, such as... Figure 5 As shown, in the system, the input module is sequentially connected to the error calculation module, the PID controller module, the steering master 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; wherein:

[0139] Input module: Used to receive the steering wheel rotation angle and convert it into an input signal;

[0140] PID controller module: used to convert the steering wheel rotation angle signal into a steering drive signal;

[0141] Steering main control module: used to compensate for dynamic characteristic differences in steering drive signals using a mechanical transfer function model, and to obtain the rotation angle of the motor when it is not under steering ratio control;

[0142] Comparison module: Used to compare the rotation angle of the motor without steering ratio control with the rotation angle of the steering wheel. If they are compatible, the motor will be processed in the steering ratio control module. If they are not compatible, the correction angle will be transmitted to the error calculation module through the feedback path for error calculation.

[0143] Error calculation module: used to receive the correction angle transmitted by the feedback path, and to correct the input steering wheel rotation angle according to the correction angle;

[0144] Steering ratio control module: used to control the steering ratio based on the input steering wheel rotation angle, and outputs the actual rotation angle of the motor;

[0145] Steering execution module: Used to control the steering of the wheels using the four-wheel steering mechanism based on the actual rotation angle of the received motor.

[0146] This system achieves automatic adjustment and real-time feedback of the four-wheel steering mechanism through the cooperation of different modules. This reduces driver intervention and simplifies operation, especially in emergency situations, enhancing driver control and allowing them to focus on other important tasks. It also strengthens emergency response capabilities, dynamically adjusting steering strategies based on real-time road conditions when fire trucks are on emergency missions. This ensures steering accuracy and stability in complex environments, enabling rapid steering response and high-precision control, thus improving the fire truck's maneuverability in urban areas or complex scenarios. Precise control of the four-wheel steering angle allows fire trucks to quickly change direction, respond swiftly to emergencies, and maximize operational efficiency.

[0147] Preferably, the PID controller module includes a PID control algorithm for signal adjustment, wherein the formula of the PID control algorithm is:

[0148]

[0149] in, For proportional gain, For integral gain, For differential gain, is the complex frequency variable in the Laplace transform.

[0150] In this module, a PID control algorithm is used to automatically control the four-wheel steering mechanism, enabling real-time adjustment of the steering angles of all four wheels to ensure steering accuracy and stability. The PID controller effectively suppresses instability phenomena such as overshoot and oscillation that may occur during steering, thereby improving the driving safety and stability of the fire truck in complex environments.

[0151] Preferably, the steering main control module further includes constructing a mechanical transfer function model, which describes the mechanical motion by using a second-order differential equation and performing a Laplace transform on it, while 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 extend the mechanical transfer function model, thereby constructing the final mechanical transfer function model.

[0152] The formula for the mechanical transfer function model is as follows:

[0153]

[0154] in, The transfer coefficient represents the system gain; The damping coefficient; To transmit natural frequencies; The transmission damping coefficient; For the damping frequency, is the complex frequency variable in the Laplace transform.

[0155] In this module, a mechanical transfer function model is used to optimize the system's dynamic characteristics, resulting in higher steering accuracy and further improving system performance. The mechanical transfer function model is used to obtain the motor's rotation angle without steering ratio control. This angle is then compared with the steering wheel rotation angle in the steering ratio control module to determine if the input steering wheel rotation angle is acceptable. If acceptable, subsequent processing is performed to obtain the actual motor rotation angle for controlling the fire truck's steering. If unacceptable, a correction angle is input to the error calculation module for error calculation to obtain the acceptable steering wheel rotation angle. This enables real-time monitoring of the steering wheel input signal, allowing the fire truck to adjust its steering angle in real time, avoiding oversteering or understeering. Finally, the steering execution module uses the actual motor rotation angle obtained from the four-wheel steering mechanism to steer the fire truck. This significantly reduces the turning radius of the fire truck in narrow sections such as tunnels, enabling rapid steering operations in extremely limited spaces. This effectively improves the safety and stability of the fire truck in complex environments, increasing rescue efficiency.

[0156] Preferably, this system also includes a simulation verification module, which performs simulation verification using Matlab's Simulink. A schematic diagram of the Simulink simulation structure is shown below. Figure 3 As shown, the input module and the comparison and error calculation module are connected first, and then the proportional gain is... Integral gain Differential gain The input is processed by the PID controller module, and then connected to the steering master control module for optimization. Simultaneously, the steering master control module receives the transmission coefficients. Damping coefficient Transmitting natural frequencies Transmission damping coefficient and transmission damping frequency The parameter data, wherein the transfer coefficients mentioned in the simulation. The value is set to 0.95. Next, it is connected to the comparison and error calculation module and the steering ratio control module respectively to compare the motor's rotation angle without steering ratio control with the steering wheel's rotation angle. Based on the comparison result, it is determined whether error calculation is needed. Then, the steering ratio control module is used to perform steering ratio control, thereby inputting the obtained actual motor rotation angle into the steering execution module for steering processing. Simultaneously, the output is as follows: Figure 4The simulation results shown in the figure demonstrate that the system exhibits no obvious oscillations or loss of control during steering wheel rotation. This system demonstrates high stability, meeting the emergency steering requirements of fire trucks. Furthermore, the system accurately transmits steering motions from the front wheels to the rear wheels, ensuring smooth and flexible four-wheel steering.

[0157] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention should 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: Receives the steering wheel rotation angle and converts it into an input signal; S2: A PID controller is used to convert the steering wheel rotation angle signal into a steering drive signal based on the input signal; S3: The mechanical transfer function model is used to compensate for the dynamic characteristic difference of the steering drive signal to obtain the rotation angle of the motor when it is not under steering ratio control. 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%, the motor is deemed qualified and proceeds to the next step. If the two are not equal and are not within the error allowable range of ±5%, the motor is deemed unqualified and the error of the input steering wheel rotation angle needs to be calculated and steps S2-S4 are repeated. S5: Controls the steering ratio based on the input steering wheel rotation angle and outputs the actual rotation angle of the motor. S6: Based on the actual rotation angle of the motor received, the four-wheel steering mechanism is used to control the steering of the wheels.

2. The control method for a four-wheel steering mechanism of a fire truck according to claim 1, characterized in that, The PID controller in step S2 includes using a PID control algorithm to adjust the signal, wherein the formula of the PID control algorithm is: in, For proportional gain, For integral gain, For differential gain, is the complex frequency variable in the Laplace transform.

3. The control method for a four-wheel steering mechanism of a fire truck according to claim 1, characterized in that, Step S3 includes the construction of the mechanical transfer function model, the steps of which are as follows: S31: The mechanical motion is described by a second-order differential equation and subjected to a Laplace transform. Natural frequency and damping coefficient are introduced to describe the dynamic characteristics of the mechanical motion, resulting in a standard mechanical transfer function model. S32: The mechanical transfer function model is extended by introducing the transfer coefficient and damping frequency, thereby constructing the final mechanical transfer function model.

4. The control method for a four-wheel steering mechanism of a fire truck according to claim 3, characterized in that, In step S32, the formula for the mechanical transfer function model is: in, The transfer coefficient represents the system gain; The damping coefficient; To transmit natural frequencies; The transmission damping coefficient; For the damping frequency, is the complex frequency variable in the Laplace transform.

5. The control method for 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: The chassis supports the entire steering mechanism; Steering drive module: Driven by a single motor, it provides the driving force for steering; Steering control module: connected to the steering drive module, used to convert the driving force into the oscillation of the Ackermann steering mechanism; Ackermann steering module: includes a front wheel steering assembly and a rear wheel steering assembly, used to control the steering angle of the inner wheel to be greater than that of the outer wheel, wherein the front wheel steering assembly is connected to the steering control module; Steering transmission module: Connects the front wheel steering assembly and the rear wheel steering assembly, and is used to transmit 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 the ratio ranges 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 also includes using Simulink for simulation verification, and optimizing the parameters of the PID controller transfer function and mechanical transfer function model based on the simulation results.

8. A control system for a four-wheel steering mechanism of a fire truck, characterized in that, The system includes: Input module: Used to receive the steering wheel rotation angle and convert it into an input signal; PID controller module: used to convert the steering wheel rotation angle signal into a steering drive signal; Steering main control module: used to compensate for dynamic characteristic differences in steering drive signals using a mechanical transfer function model, and to obtain the rotation angle of the motor when it is not under steering ratio control; Comparison module: Used to compare the rotation angle of the motor without steering ratio control with the rotation angle of the steering wheel. If they are compatible, the motor will be processed in the steering ratio control module. If they are not compatible, the correction angle will be 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 to correct the input steering wheel rotation angle according to the correction angle; Steering ratio control module: used to control the steering ratio based on the input steering wheel rotation angle, and outputs the actual rotation angle of the motor; Steering execution module: Used to control the steering of the wheels using the four-wheel steering mechanism based on the actual rotation angle of the motor received.

9. The control system for a four-wheel steering mechanism of a fire truck according to claim 8, characterized in that, The PID controller module includes a PID control algorithm to regulate the signal, wherein the formula for the PID control algorithm is: in, For proportional gain, For integral gain, For differential gain, is the complex frequency variable in the Laplace transform.

10. The control system for a four-wheel steering mechanism of a fire truck according to claim 8, characterized in that, The steering main control module also includes constructing a mechanical transfer function model. It uses a second-order differential equation to describe the mechanical motion and performs a Laplace transform on it. At the same time, it introduces the natural frequency and damping coefficient to describe the dynamic characteristics of the mechanical motion. Then, it introduces the transfer coefficient and damping frequency to extend the mechanical transfer function model, thereby constructing the final mechanical transfer function model. The formula for the mechanical transfer function model is as follows: in, The transfer coefficient represents the system gain; The damping coefficient; To transmit natural frequencies; The transmission damping coefficient; For the damping frequency, is the complex frequency variable in the Laplace transform.

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