Simulation Test

strategy of the LQG and wheelbase preview control was applied for the rear quarter suspension. The simulation test results verify the validity and practicability of the test method in the paper.
A Simulation Test Method for A Half Semi-active Vehicle Suspension Based on the Hierarchical Modeling Method
B.B. Peng, X.Q. Huang
Abstract-The hardware-in-the-loop simulation test is a substitute way for evaluating vibration control of a vehicle suspension. Due to a hierarchical modeling method that a whole wheelbase preview control is applied for the rear 2-DOF suspension. Thus, according to the results of the front 2-DOF suspension test, not only induced the control effects of the rear 2-DOF suspension, but also the vibration state of the half vehicle suspension will be simulated by employing the center control equations of the hierarchical modeling method so as to realize the evaluation of the whole control purpose II HIERARCHICAL MODELING METHOD
Index Terms-hardware-in-the-loop, hierarchical modeling,
adopted in the front quarter suspension. A complex control
A
Xc
X
cr
vehicle test. The hardware-in-the-loop simulation test based on computer software can revise some control strategies and algorithms according to the vehicle parameters and road excitation. It can decrease the experiment cost, short the study period and overstep the routine of "produce model machine test - modify - reproduce model machine". So this method is getting more attentions in recent years [1] Generally speaking, the hardware-in-the-loop simulation test based on a set of vibration table and actuator can only be
magneto-rheological damper, semi-active control, simulation test, vehicle suspension I. INTRODUCTION n order to evaluate the control strategy and actuators' Iperformance, the damping capacity tests can be carried out when the structural parameters of a vehicle controllable suspension are settled. As a result of high test fee, more modification restriction and long period of a real vehicle test, now the optimal scheme of the hardware-in-the-loop simulation test, which employs the computer software to
replace some control hardware, is substituted for the real
Ff
/f
F
applied for a quarter vehicle suspension testing, and hardly
Fig. 1 The fcrce analysis of the sprung mass There are twoons for forces and moments with regard to mass center point C m x F +F c c- f r (1)
suspensions,
tne atest asc
e
can
inotionly displayte
transducers, etc. The real time LQG control strategy was
executed by a computer software equipped with some facilities such as a vibration table, a magneto-rheological damper and
ever for evaluating a half or a whole vehicle suspension. In this paper, a hierarchical modeling method is put forward for a half vehicle suspension. It can be used to decompose a half vehicle suspension with 4-DOF to two quarter vehicle suspensions, which are restricted with center control. The LQG control strategy is adopted in the front 2-DOF suspension. A complex control strategy of the LQG and
IC0i = Frl-Fl
(2)
1-4244-0759-1/06/$20.OO ©2006 IEEE.
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0 c
combination of some vehicle suspension can be acted as a c f
quarter
controllability of a quarter vehicle suspension, but also evaluate the damping capacity of a half or whole suspension. In this paper, the semi-active control of a half vehicle suspension is
m (15) xui -Xi where the subscript i is f or r which denote the front M or rear suspension. Confirming the sampling time and (3) (mclrxG + defining AXU=xUf -xx and A.xurx*r -xur the unsprung = (m l.f c +IcOY )/l mass displacement variables Axuf and A xur can be (4) obtained as follows. Assumed xc = x +I1fO = xc, - IrO and substituted it into the equation (3) and (4), the displacements of the front and mv < - k/xSf mfxf mAxf -n13g. -k,xv (16) - k.rxr rear suspensions, Xcf and xcr can be obtained. = X -mL?,.r +, (17) mj3, +k, ax,u m, +k,, (5) mclfxcr + -Mcl/fIr )c -iF 0 where Xsf and xsr are the excitations of the front and rear road, respectively, m. kf and k., are the stiffness (6) Mc r - (ICMc IfIr jc -iFf -0 coefficients of the front and rear wheel, respectively, N I m. (5) + (6), we get mUf and mur are the front and rear unsprung masses, mcfxcf +mcr cr -Ff -1F =0 (7) respectively,kg. c7Zf and c 7,r are the damping coefficients xf Mcr (6) (5) I /I we haveof the front and rear suspension, respectively, N-s/m. Fmf (5) x x i~. 1, we have 4/i-(6) and Fr are the front and rear semi-active control forces, -F; ( -mcflfir)Uc =0 respectively, N . (8) mjrlr_X -mlcfIXf f +IfF in) The detailed process of the hierarchical modeling method Where is the center /1 IMcr Mcf/ic for a half vehicle suspension iS as follows. distance from the front wheel to the rear wheel. The two 1) The mathematical expectation of 3c and Oc by virtue equations above indicate that the sprung mass could be simplified into a igidpolewithtwoconcentratedmassatof the road excitation should be determined firstly. The r pole with two concentrated mass at itS simplified into a rigid gie rag of3 n chv hi rbblte o rc both ends. The equation (7) and (8) can be acted as the force to exceed 99.7 percent of the limited values o and and moment dynamic balance equations, respectively. The 7p , respectively. We require key of the hierarchical modeling method is how to distribute < < ,7p 3 (18) the sprung mass has been settled. Therefore, a half vehicle , suspension can be treated as a combination of two where of and (7 are the limited values of the body vertical and pitch accelerations and can be pr-estimated, independent 2-DOF suspensions. If If equals to 1,, a half vehicle suspension could be decomposed into front and rear respectively. 2-DOF suspensions without consideration. This is the concept (19) u -s O.6xs (t* /19 of mass partition coefficient presented by literature [5]. (20) Without the rear restriction, the concentrated mass of the (s.6 Xsr) U2l front suspension mcf would generate a displacement Axf. 2) The expectation values of fc and er can be Similarly, withoutthe front restriction, the concentrated mass of the rear suspension would generate a displacement calculated by Eq. (3), (4), (7) and (8). The expectation axt Defining Asxo mcf-xr and ax nx -x, the new values of Arf and AXr can be got by Eq. (11) and r r Xr equations of motion can be (12). Thus, the front and rear expectation -ilues of the decomposed sprung mass accelerations f and r AXf (9) mcfXf =Ff +imcf can be determined.