The Study of New Rods for Frame Devices in Vehicle Modality

Suspension parameter uncertainty describes the dynamic uncertainty and parameter uncertainty in the vehicle suspension model. Because the dynamic uncertainty is very complex and non-linear, it mainly discusses the sprung mass ms and suspension spring stiffness. Ksi and tire stiffness kt and other parameters of the uncertainty. All uncertain parameters can be written in the following linear fractional form by linear fractional transformation (LFT): 1ms=1ms(1+dmsδms)=1ms-dmsmsδms(1+dmsδms)-1=F1ms-dmsms1-dms, Δms=Fl(Mms, δms) ki=ki+kidkiδki=F1ki1dkiki0, δki=Fl(Mki, δki) (i=s1, s2, s3, s4, t) where: ms,ki basic value, ie, initial hypothesis The standard value of i, i = s1, s2, s3, s4, t; dms, dki scalar, said the parameter allows the percentage of changes around the basic value, i = s1, s2, s3, s4, t.

The parameters δms, δki (i = s1, s2, s3, s4, t) vary between them and determine the deviation of the actual parameters.

The lower linear fraction of the uncertain parameter, the LFT structure, is shown.

LFT Structure of Uncertain Parameters 3 Frequency augmentation of mixed uncertain system Description The uncertain variable parameters are substituted into the formula, and the state variable X = T is selected, which can be obtained in the state space equation of the entire vehicle suspension system: e unmodeled dynamic input; d unmodeled dynamic output; y δ perturbation output; f control input, f = T; w external input, w = T; u δ uncertain input, active suspension Uncertain system block diagram as shown, suspension mass, front and rear suspension The uncertainty transfer function of stiffness and front and rear tire stiffness is represented by Δr, and Δr includes |δms| in the diagonal form. Through the description of frequency-weighted augmentation of hybrid uncertain systems, the generalized structure of the active suspension hybrid closed-loop uncertain closed-loop system The controlled object is: G(s) = ΔWpIG0(s) WrWwI Augmented controlled object control system As shown, the channel Tde:e→d has an uncertain link Δ(s), which is related to the robust stability of the system. Measured by the H∞ norm; channel Tzw:w→z, reflecting the impact of road surface disturbances on dynamic performance, measured by the H2 norm.

Uncertain Active Suspension System Block Diagram Analysis of augmented controlled object frame simulation results In order to evaluate the influence of suspension parameter uncertainty, an H2/H∞ hybrid controller was designed to allow the system frequency domain under random road conditions for steering conditions. Response to analysis. See the relevant parameters of the simulation vehicle. Assume that the vehicle passes Class C road surface at a speed of 20m/s and the front wheel angle input is a 5° step signal. The road surface disturbance input at each wheel during steering is irrelevant. Under the environment of Matlab7.0, the active suspension is simulated and compared with the passive suspension, and the amplitude-frequency characteristics of the vehicle body centroid vertical acceleration, pitching acceleration, roll angle acceleration, and suspension dynamic deflection are plotted. As shown.

From a can be seen, with the active suspension controller, in the frequency range of 4 ~ 12.5Hz, the amplitude-frequency characteristics of the vertical acceleration at the center of mass of the vehicle body than the passive suspension has been reduced to a greater extent. From b and c, it can be seen that the amplitude and frequency characteristics of the pitch acceleration and roll angle acceleration of the active suspension have a certain decrease in the frequency range of 1 to 2 Hz. As can be seen from d, in the low frequency region below 1 Hz, the amplitude-frequency characteristics of dynamic suspension of active suspension are worse than those of passive suspension, and in other frequency ranges, the amplitude-frequency characteristics of dynamic deflection of active suspension are improved. Due to the inherent characteristics of the suspension system, there are constraints between the performance indicators. From the above simulation results, it can be seen that the use of robust control can improve the overall performance of the active suspension system.

(a) Vertical acceleration of the center of mass of the vehicle body (b) Acceleration amplitude and frequency characteristics of the pitching angle (c) Amplitude and frequency characteristics of the roll angle acceleration (d) Amplitude-frequency characteristics of the amplitude-frequency characteristics of the dynamic deformation of the left front suspension The conclusion is established using the linear fractional transformation theory. The active suspension hybrid uncertain model was used to design a robust controller for the active suspension. The amplitude-frequency characteristics of the system under the steering conditions were analyzed. The simulation results show that compared with the passive suspension, the active suspension with robust control has obvious suppression of the vertical velocity of the center of mass, the acceleration of the pitching angle and the acceleration of the roll angle, and the dynamic deflection of the suspension can also be obtained in the larger frequency range. The goal of control. The results show that the robust control method can improve the overall performance of the suspension.