Anti-carsickness semi-active seat band elimination filtering control method

Abstract

The invention discloses an anti-carsickness semi-active seat band-stop filtering control method, which comprises the following steps of: firstly, establishing a two-degree-of-freedom model of a vehicle seat suspension system, and designing a seat suspension active control system to meet the following constraint conditions: the dynamic stroke of a seat suspension does not exceed the maximum allowable stroke; and the control force is smaller than the maximum output control force of the actuator. In order to effectively reduce the carsickness symptom caused by seat vibration, the invention also establishes a target function for inhibiting the vibration of the seat in a human body sensitive frequency range, designs a frequency weighted sliding mode control algorithm, accurately adjusts the damping coefficient of the magnetorheological damper through a control law, inhibits the low-frequency vibration in the frequency range of 0.1-0.5 Hz, and improves the safety of the seat. The riding comfort is improved, and the motion sickness is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of vehicle vibration control, and in particular to a method for controlling a semi-active seat with a band-stop filter to prevent motion sickness. Background Art

[0002] With the development of modern transportation, the automobile seat suspension system has become the key to improving passenger comfort. Traditional passive suspension, semi-active suspension and active suspension each have their own advantages and disadvantages. Semi-active suspension strikes a balance between energy consumption and performance and has become a research hotspot. Magnetorheological damper (MRD), as an intelligent material, can change the damping characteristics by adjusting the magnetic field intensity to improve suspension performance. However, the nonlinear and hysteresis characteristics of MRD make the traditional PID control effect limited. Sliding mode control (SMC), as a highly robust nonlinear control method, can effectively cope with system uncertainties and external disturbances, achieve precise control of MRD, and maintain the stable vibration reduction effect of seat suspension under complex road conditions.

[0003] Research on the problem of motion sickness in passengers shows that the main cause of motion sickness is that the vibration frequency in the car is close to the natural frequency of the human head and inner ear, which is usually concentrated in the low-frequency range of 0.1-0.5Hz. Therefore, when designing a seat suspension system, the key is to reduce the vibration in this frequency band. To this end, the control strategy can be optimized in combination with the idea of ​​band-stop filters. Band-stop filters are electronic filters specially designed to suppress signals within a specific frequency range. They are widely used in situations where specific frequency interference is removed, especially when dealing with low-frequency vibrations. Its working principle is to attenuate or eliminate signals within a specific frequency range by selecting a center frequency and setting the bandwidth, while having little effect on other frequency components. Band-stop filters form a "notch" in the spectrum, which significantly reduces the signal amplitude in the target frequency range, thereby effectively removing unwanted interference.

[0004] When designing a band-stop filter, you first need to determine the frequency to be suppressed, that is, set the center frequency, and select the appropriate bandwidth according to actual needs. The narrower the bandwidth, the stronger the filter's suppression effect on the center frequency, but the affected frequency band is smaller; the wider the bandwidth, the filter can suppress a wider frequency range, but it may have a certain impact on other frequency components. By precisely adjusting these parameters, the band-stop filter can effectively suppress vibrations of specific frequencies without interfering with other signal components. In the seat suspension system, combining sliding mode control with the idea of ​​band-stop filters, low-frequency vibrations can be accurately identified and suppressed by adjusting the damping characteristics in real time. The sliding mode controller not only has good robustness, but also can accurately control damping, thereby significantly reducing the vibration amplitude in a specific frequency band, optimizing the riding experience, and alleviating motion sickness symptoms.

[0005] The anti-motion sickness semi-active seat band-stop filter control method proposed in this patent can accurately suppress the uncomfortable frequency vibrations that cause motion sickness by combining the robustness of sliding mode control with the frequency selection characteristics of band-stop filtering. Summary of the invention

[0006] The present invention combines sliding mode control, band-stop filter and real-time adjustment technology of magnetorheological damper to accurately suppress low-frequency vibration of the seat suspension, thereby effectively reducing the incidence of motion sickness and improving riding comfort.

[0007] To achieve the above object, the present invention discloses a method for controlling a motion sickness-proof semi-active seat with a band-stop filter, comprising the following steps:

[0008] S1. According to the vehicle dynamics characteristics, a dynamic model of the seat suspension two-degree-of-freedom semi-active vibration system is established;

[0009] S2, determine the basic performance constraints of the suspension and take motion sickness index as another important part;

[0010] S3. Design a frequency-weighted sliding mode control system capable of suppressing 0.1-0.5 Hz vibrations to meet the specified performance requirements.

[0011] S4. Formulate a sliding mode control law including equivalent control and switching control parts to ensure that the system state can reach and remain on the sliding mode surface;

[0012] S5. Combine sensor detection, controller calculation and magnetorheological suspension damping force adjustment to achieve precise control of the seat suspension system.

[0013] Furthermore, step S1 is specifically as follows:

[0014] The motion differential equation of the seat suspension two-degree-of-freedom semi-active vibration system is as follows:

[0015]

[0016] Where: m 1 is the body mass, m 2 is the seat mass, c 1 is the damping of the seat cushion, k 1 is the stiffness of the cushion, c 2 is the damping of the magnetorheological damper, k 2 is the stiffness of the magnetorheological damper, x 1 is the vertical displacement of the human body, x 2 is the vertical displacement of the seat, is the vertical velocity of the human body, is the vertical velocity of the seat, is the vertical acceleration of the human body, is the vertical acceleration of the seat, x3 is the excitation of the body to the seat, F MRD is the damping force of the magnetorheological damper.

[0017] Introduce state variables:

[0018] z 1 =x 1 , z 3 =x 2 ,

[0019] Solve the system's differential equation of motion:

[0020]

[0021] Convert the differential equation of motion of the semi-active suspension system into the system state equation:

[0022]

[0023] in: U=[F MRD ];

[0024]

[0025] Furthermore, step S2 is specifically as follows:

[0026] S2.1 Establish basic suspension performance constraints

[0027] The relative displacement of the suspension system must be within a safe range, i.e. |x 3 -x 2 |≤X max , X max Indicates the maximum stroke of the magnetorheological damper to avoid collision or insufficient stroke; the control force should be less than the maximum damping force output by the magnetorheological damper, i.e. |F MRD |≤F max , F max Indicates the maximum damping force that the magnetorheological damper can output c 2 is the damping coefficient of the magnetorheological damper, k 2 is the stiffness of the magnetorheological damper, x r is the initial position of the damper.

[0028] S2.2 Establish an optimization objective function including anti-motion sickness indicators

[0029] The optimization objective function is as follows:

[0030]

[0031] Where: J is the optimization objective function, T is the evaluation time period, α s (t) is the vertical acceleration of the vehicle body, WAA(t) is the weighted vertical acceleration, Δz s (t) is the relative displacement between the body and the seat, F MRD (t) is the damping force, q 1 ,q 2 ,q 3 ,q 4 is the weight coefficient.

[0032] Furthermore, step S3 is specifically as follows:

[0033] S3.1 Design of sliding surface

[0034] The design of the sliding surface aims to achieve the desired dynamic performance of the system on the sliding surface by selecting an appropriate combination of state variables. For a two-degree-of-freedom suspension system, the sliding surface S can be defined as a linear combination of the relative displacement and relative velocity of the system:

[0035]

[0036] Where: α 1 and α 2 is the sliding surface parameter; W(ω) is the weighting function for the frequency range of 0.1-0.5 Hz,

[0037] ω is the bandwidth, ω=2πf, f is the vibration frequency, ω C is the center frequency, ω c =2π×0.3rad / s, ζ is the damping ratio.

[0038] S3.2 Establishing sliding mode dynamic equation

[0039] The core of sliding mode control is to ensure that the system state can slide along the sliding surface S = 0. To achieve this, it is necessary to design the control input U so that the derivative of the sliding surface S satisfies:

[0040]

[0041] Where: sat(·) is the saturation function, defined as sgn(S) is the sign function, defined as φ is the boundary layer thickness.

[0042] S3.3 Analysis of the stability of Lyapunov function

[0043] In order to ensure that the system state is finally stabilized on the sliding surface and remains stable, the Lyapunov function V(S) and its derivative are defined:

[0044]

[0045] Its time derivative is:

[0046]

[0047] Consider different situations:

[0048] 1. When |S|>φ:

[0049]

[0050] 2. When |S|≤φ:

[0051]

[0052] No matter what the situation of S is, the derivative of the Lyapunov function is always less than or equal to zero, ensuring that the system state eventually tends to the sliding surface S = 0 and remains stable.

[0053] S3.4 Select sliding mode control parameters

[0054] The performance of sliding mode control is highly dependent on the sliding surface parameter α 1 and α 2 , convergence speed parameter η and boundary layer thickness φ. The selection of parameters needs to comprehensively consider the dynamic response, steady-state error and chattering phenomenon of the system.

[0055] Furthermore, step S4 is specifically as follows:

[0056] S4.1. Design equivalent control part

[0057] The equivalent control part aims to ensure that the system state slides along the sliding surface S = 0, ignoring the uncertainty and disturbance of the system. Based on the system state space model, the equivalent control input U eq It can be obtained by the following method:

[0058] U eq =-(B T B) -1 B T (AZ)

[0059] U eq =-k 1 z 1 -c 1 z 2 +(k 1 +k 2 ) 3 +(c 1 +c 2 ) 4

[0060] S4.2. Design of switching control part

[0061]

[0062] Where: K is the switching gain, which must be satisfied To ensure the stability of the system.

[0063] S4.3. Obtaining the comprehensive control law

[0064] The final sliding mode control law U is a combination of the equivalent control part and the switching control part:

[0065] U=U eq +U sw

[0066] Through this control law, the damping coefficient c of the magnetorheological damper 2 It can be adjusted in real time according to the control input U to achieve active control of the vibration of the suspension system.

[0067] Furthermore, step S5 is specifically as follows:

[0068] High-precision acceleration sensors and displacement sensors are installed on the car seats and body, and the sampling frequency should be higher than 1kHz to ensure that fast-changing dynamic information is captured. The collected signals are processed by the analog-to-digital converter (ADC) and transmitted to the controller in real time. The controller adopts a frequency-weighted sliding mode control algorithm to specifically suppress low-frequency vibrations in the range of 0.1-0.5Hz to reduce the impact of low-frequency vibrations on passenger comfort. The system generates control signals and accurately adjusts the damping coefficient of the magnetorheological damper, thereby effectively reducing the vibration amplitude of the car seat and improving ride comfort. At the same time, the system can effectively reduce the occurrence of motion sickness and improve the passenger experience. Through intelligent algorithms and real-time control strategies, the system can quickly respond to different road conditions, maintain a stable vibration suppression effect, and achieve more efficient ride comfort and safety.

[0069] Compared with the prior art, the anti-motion sickness active seat band-stop filter control method of the present invention has the following beneficial effects:

[0070] (1) Considering that the frequency range in which occupants are prone to motion sickness is 0.1-0.5 Hz, this frequency range is taken as an important constraint condition of the semi-active suspension system, and a seat anti-motion sickness band-stop filter system based on sliding mode control is designed. The system suppresses low-frequency vibrations that cause occupants' motion sickness, thereby effectively improving riding comfort.

[0071] (2) The present invention adopts sliding mode control, which can guide the system state to the sliding surface within a limited time and maintain the expected dynamic characteristics on the sliding surface, so as to quickly respond and adjust the damping in time to cope with instantaneous vibration changes and improve the anti-motion sickness effect. At the same time, sliding mode control is highly compatible with magnetorheological dampers, and there is no need to make major modifications to the hardware, ensuring its feasibility and scalability in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 is a dynamic model of the semi-active seat suspension system of the present invention;

[0073] Figure 2 It is a technical roadmap of the anti-motion sickness active seat band-stop filter control method of the present invention; DETAILED DESCRIPTION

[0074] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0075] like Figure 1-2 As shown, a method for controlling a motion sickness-proof semi-active seat with a band-stop filter comprises the following steps:

[0076] S1. According to the vehicle dynamics characteristics, a dynamic model of the seat suspension two-degree-of-freedom semi-active vibration system is established;

[0077] The motion differential equation of the seat suspension two-degree-of-freedom semi-active vibration system is as follows:

[0078]

[0079] Where: m 1 is the body mass, m 2 is the mass of the seat, c 1 is the damping of the seat cushion, k 1 is the stiffness of the cushion, c 2 is the damping of the magnetorheological damper, k 2 is the stiffness of the magnetorheological damper, x 1 is the vertical displacement of the human body, x 2 is the vertical displacement of the seat, is the vertical velocity of the human body, is the vertical velocity of the seat, is the vertical acceleration of the human body, is the vertical acceleration of the seat, x 3 is the excitation of the body to the seat, F MRD is the damping force of the magnetorheological damper.

[0080] Introduce state variables:

[0081] z 1 =x 1, z 3 =x 2 ,

[0082] Solve the system's differential equation of motion:

[0083]

[0084] Convert the differential equation of motion of the semi-active suspension system into the system state equation:

[0085]

[0086] in: U=[F MRD ];

[0087]

[0088] S2. Determine the basic performance constraints of the suspension and take motion sickness indicators as another important part

[0089] S2.1 Establish basic suspension performance constraints

[0090] The relative displacement of the suspension system must be within a safe range, i.e. |x 3 -x 2 |≤X max , X max Indicates the maximum stroke of the magnetorheological damper to avoid collision or insufficient stroke; the control force should be less than the maximum damping force output by the magnetorheological damper, i.e. |F MRD |≤F max , F max Indicates the maximum damping force that the magnetorheological damper can output c 2 is the damping coefficient of the magnetorheological damper, k 2 is the stiffness of the magnetorheological damper, x r is the initial position of the damper.

[0091] S2.2 Establish an optimization objective function including anti-motion sickness indicators

[0092] It is crucial to effectively prevent passengers from motion sickness in the design of suspension systems. The objective function aims to minimize the degree of motion sickness of passengers while meeting the basic performance requirements of the suspension.

[0093] The optimization objective function is as follows:

[0094]

[0095] Where: J is the optimization objective function, T is the evaluation time period, α s(t) is the vertical acceleration of the vehicle body, WAA(t) is the weighted vertical acceleration, Δz s (t) is the relative displacement between the body and the seat, F MRD (t) is the damping force, q 1 ,q 2 ,q 3 ,q 4 is the weight coefficient.

[0096] S3. Design a frequency-weighted sliding mode control system capable of suppressing 0.1-0.5 Hz vibrations to meet the specified performance requirements.

[0097] S3.1 Design of sliding surface

[0098] The design of the sliding surface aims to achieve the desired dynamic performance of the system on the sliding surface by selecting an appropriate combination of state variables. For a two-degree-of-freedom suspension system, the sliding surface S can be defined as a linear combination of the relative displacement and relative velocity of the system:

[0099]

[0100] Where: α 1 and α 2 is the sliding surface parameter; W(ω) is the weighting function for the frequency range of 0.1-0.5 Hz,

[0101] ω is the bandwidth, ω=2πf, f is the vibration frequency, ω C is the center frequency, ω c =2π×0.3rad / s, ζ is the damping ratio.

[0102] S3.2 Establishing sliding mode dynamic equation

[0103] The core of sliding mode control is to ensure that the system state can slide along the sliding surface S = 0. To achieve this, it is necessary to design the control input U so that the derivative of the sliding surface S satisfies:

[0104]

[0105] Where: sat(·) is the saturation function, defined as sgn(S) is the sign function, defined as φ is the boundary layer thickness.

[0106] S3.3 Analysis of the stability of Lyapunov function

[0107] In order to ensure that the system state is finally stabilized on the sliding surface and remains stable, the Lyapunov function V(S) and its derivative are defined:

[0108]

[0109] Its time derivative is:

[0110]

[0111] Consider different situations:

[0112] 1. When |S|>φ:

[0113]

[0114] 2. When |S|≤φ:

[0115]

[0116] No matter what the situation of S is, the derivative of the Lyapunov function is always less than or equal to zero, ensuring that the system state eventually tends to the sliding surface S = 0 and remains stable.

[0117] S3.4 Select sliding mode control parameters

[0118] The performance of sliding mode control is highly dependent on the sliding surface parameter α 1 and α 2 , convergence speed parameter η and boundary layer thickness φ. The selection of parameters needs to comprehensively consider the dynamic response, steady-state error and chattering phenomenon of the system.

[0119] S4. Formulate a sliding mode control law including equivalent control and switching control parts to ensure that the system state can reach and remain on the sliding mode surface;

[0120] S4.1. Design equivalent control part

[0121] The equivalent control part aims to ensure that the system state slides along the sliding surface S = 0, ignoring the uncertainty and disturbance of the system. Based on the system state space model, the equivalent control input U eq It can be obtained by the following method:

[0122] U eq =-(B T B) -1 B T (AZ)

[0123] U eq =-k 1 z 1 -c 1 z 2 +(k 1 +k 2 ) 3 +(c 1 +c 2 ) 4

[0124] S4.2. Design of switching control part

[0125]

[0126] Where: K is the switching gain, which must be satisfied To ensure the stability of the system.

[0127] S4.3. Obtaining the comprehensive control law

[0128] The final sliding mode control law U is a combination of the equivalent control part and the switching control part:

[0129] U=U eq +U sw

[0130] Through this control law, the damping coefficient c of the magnetorheological damper 2 It can be adjusted in real time according to the control input U to achieve active control of the vibration of the suspension system.

[0131] S5. Combine sensor detection, controller calculation and magnetorheological suspension damping force adjustment to achieve precise control of the seat suspension system.

[0132] High-precision acceleration sensors and displacement sensors are installed on the car seats and body, and the sampling frequency should be higher than 1kHz to ensure that fast-changing dynamic information is captured. The collected signals are processed by the analog-to-digital converter (ADC) and transmitted to the controller in real time. The controller adopts a frequency-weighted sliding mode control algorithm to specifically suppress low-frequency vibrations in the range of 0.1-0.5Hz to reduce the impact of low-frequency vibrations on passenger comfort. The system generates control signals and accurately adjusts the damping coefficient of the magnetorheological damper, thereby effectively reducing the vibration amplitude of the car seat and improving ride comfort. At the same time, the system can effectively reduce the occurrence of motion sickness and improve the passenger experience. Through intelligent algorithms and real-time control strategies, the system can quickly respond to different road conditions, maintain a stable vibration suppression effect, and achieve more efficient ride comfort and safety.

[0133] The above are preferred embodiments of the present invention. A person skilled in the art may make various changes or improvements on this basis. Without departing from the general concept of the present invention, these changes or improvements should fall within the scope of protection required by the present invention.

Claims

1. A method for controlling a semi-active seat band-stop filter to prevent motion sickness, characterized in that: The steps include: S1. According to the vehicle dynamics characteristics, a dynamic model of the seat suspension two-degree-of-freedom semi-active vibration system is established; S2, determine the basic performance constraints of the suspension and take motion sickness index as another important part; S3. Design a frequency-weighted sliding mode control system capable of suppressing 0.1-0.5 Hz vibrations to meet the specified performance requirements. S4. Formulate a sliding mode control law including equivalent control and switching control parts to ensure that the system state can reach and remain on the sliding mode surface; S5. Combine sensor detection, controller calculation and magnetorheological suspension damping force adjustment to achieve precise control of the seat suspension system.

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