Disturbance rejection control of a light armoured vehicle using stability augmentation based active suspension system
Khisbullah Hudha* Autotronics Lab – Department of Automotive, Faculty of Mechanical Engineering, Universiti Teknikal Malaysia Malacca (UTeM), Karung Berkunci 1200, Ayer Keroh 75450, Malacca, Malaysia E-mail: [email protected] *Corresponding author
Hishamuddin Jamaluddin
and Pakharuddin Mohd. Samin Faculty of Mechanical Engineering, Universiti Teknologi Malaysia (UTM), 81310 UTM Skudai, Johor, Malaysia E-mail: [email protected] E-mail: [email protected]
Abstract: This paper introduces the mathematical model of 12 Degrees of Freedom (DOF) light armoured vehicle, which consists of eight DOF in vertical motion of eight tyres, three DOF in vertical, roll and pitch motions of vehicle body and one DOF in angular motion of gun turret relative to weapon platform. Two sources of disturbance considered in this study are road irregularities and reaction force at the weapon platform. The results of the study show that the stability augmentation based active suspension system is able to significantly improve the dynamic performance of the light armoured vehicle compared with the passive system.
Reference to this paper should be made as follows: Hudha, K., Jamaluddin, H. and Samin, P.M. (2008) ‘Disturbance rejection control of a light armoured vehicle using stability augmentation based active suspension system’, Int. J. Heavy Vehicle Systems, Vol. 15, Nos. 2/3/4, pp.152–169.
Biographical notes: Khisbullah Hudha received his BEng in Mechanical Design from the Bandung Institute of Technology (ITB) of Indonesia, his MSc from the Department of Engineering Production Design, Technische Hoogeschool Utrecht, The Netherlands, and his PhD on intelligent vehicle dynamics control using magnetorheological damper from the Universiti Teknologi Malaysia (UTM). His research interests include modelling, identification and force tracking control of magnetorheological damper, evaluation of vehicle ride and handling, electronic chassis control system design and intelligent control.
Disturbance rejection control of a light armoured vehicle 153
Hishamuddin Jamaluddin received his BSc, MSc and PhD from the Department of Control Engineering, Sheffield University, UK. He is currently a Professor in the Department of Applied Mechanics, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Johor, Malaysia. His research interests include non-linear system modelling, system identification, neural networks, adaptive fuzzy models, genetic algorithm, neuro-fuzzy and active force control.
Pakharuddin Mohd. Samin received his BSc and MSc from the Department of Mechanical Engineering, Texas A&M University, USA. From 1994–1996, he worked at Bath University, UK, on the design of an active roll control suspension system for passenger vehicles. He is currently a PhD student in the Department of Aeronautics and Automotive Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Johor, Malaysia. His research interests include continuously variable damper, ride and handling of vehicle and vehicle dynamics control.
1 Introduction
Multi-wheeled and tracked military vehicles, such as light armoured vehicles, tanks or armoured personnel carriers, which traverse over rough off-road terrain, demand strong driving force, manoeuvrability, stability and ride comfort. Stability and ride comfort in multi-wheeled and tracked military vehicles depend on a combination of vertical motion and angular motions of pitch and roll. Since multi-wheeled and tracked military vehicles are intended to deliver accurate firing attack, stability and ride comfort for the military vehicles is a must. This study focuses on the enhancement of stability and ride comfort of a class of multi-wheeled vehicles namely light armoured vehicle using an active suspension system.
Early works on the development of advanced suspension system for military vehicles have been done using the electromagnetic suspension system (Maclaurin, 1983; Weeks et al., 1999), hydraulically actuated active suspension system (Wendel et al., 1994; Kanagawa et al., 1995, 1996; Hoogterp et al., 1996; Beno et al., 1997) and semi-active suspension system (Miller and Nobbles, 1988). Although most of the early works have investigated the dynamics performance of military vehicles on a simple vehicle model such as the one with single and two Degrees of Freedom (DOF), the advanced suspension systems are found to be able to increase the suspension performance of military vehicles.
Recent attempts to improve the dynamics performance of military vehicles have been made by Buckner et al. (2001) on an active suspension system of a quarter car model using an adaptive neural network based intelligent feedback linearisation technique. Choi et al. (2002) proposed a fuzzy sky-ground hook in controlling a 16 DOF tracked military vehicle featuring a semi-active electro-rheological suspension system. An active suspension system for a 2.5 ton military truck has been designed and tested in Hayes et al. (2005). The performances of control algorithms for a half tracked vehicle have been evaluated with a semi-active suspension system (Youn et al., 2001) and with an active suspension system using optimal preview control (Youn et al., 2006). All the recent works have claimed to have significant performance improvement when compared with the passive system.
In this paper, a 12 DOF light armoured vehicle model is introduced. An active suspension system is designed for the light armoured vehicle from the viewpoint of
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improvement in ride comfort and stability. This is to ensure a satisfactory driving environment and to protect the weapon system from inaccurate attack due to the large oscillation of the vehicle body. The control algorithm considered in this study is Stability Augmentation System (SAS), with and without the ride controller loop. The main aim of designing the active control of the light military vehicle is to reduce unwanted body bounce, body pitch and body roll generated by road irregularities or the reaction force at the weapon platform due to the effect of firing a large-calibre missile from turret gun.
This paper is organised as follows: The first section contains the introduction and a review of some relevant preliminary works, followed by a mathematical model of a 12 DOF light military vehicle in the second section. The third section introduces the disturbance model of the light military vehicle. The fourth section presents the controller structure of the active suspension system. Furthermore, the results of study are presented in the fifth section. The last section contains some conclusions and suggestions for future work.
2 Twelve DOF light armoured vehicle model
The light armoured vehicle considered in this study is based on a class of mobile gun systems which has eight wheels and is capable of firing 105 mm projectiles from the gun turret, as shown in Figure 1 (Pike, 2006a, 2006b). The full-vehicle model of the light armoured vehicle is shown in Figure 2, which consists of a single sprung mass (vehicle body) connected to eight unsprung masses and is represented as a 12 DOF system. The sprung mass is represented as a plane and is allowed to heave, pitch and roll, while the unsprung masses are allowed to bounce vertically with respect to the sprung mass.
Figure 1 A 3D view of a light armoured vehicle for a class of mobile gun system
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Figure 2 Twelve DOF light armoured vehicle with active suspension system
2.1 Modelling assumptions
Some of the modelling assumptions considered in this study are as follows: the turret gun has only one DOF in rotational motion along the horizontal plane or vertical axis of the weapon platform, the effect of yaw motion due to the reaction force of weapon platform during firing a large-calibre projectile from gun turret is neglected, each wheel is connected to the body using an independent suspension system and has only one DOF in the vertical direction, only external forces from road irregularities and reaction force at the weapon platform due to the effect of firing a large-calibre projectile from gun turret are taken into account in the equations of motion and the roll centre is coincident with the pitch centre and located at the body centre of gravity. The suspensions between the sprung mass and unsprung masses are modelled as passive viscous dampers and spring elements, while, the tyres are modelled as simple linear springs without damping.
2.2 Equations of motion of 12 DOF armoured vehicle model
In this section, the equations of motion of the light armoured vehicle with an active suspension system are derived. Equations of motion for passive system can be obtained by simply replacing the actuator forces at the left and right sides of point A, B, C and D with the relevant damper forces. Referring to Figure 2, the force balance on the sprung mass in the vertical direction is given as
,Al ,Al ,Ar ,Ar ,Bl ,Bl ,Br ,Br ,Cl
,Cl ,Cr ,Cr ,Dl ,Dl ,Dr ,Dr
s s s a s a s a s a s
a s a s a s a
M Z F F F F F F F F FF F F F F F F
= + + + + + + + +
+ + + + + + +
(1)
where Fs,Al: Spring forces at the left side of point A = ,Al ,Al ,Al( )s u sK Z Z−
Fs,Ar: Spring forces at the right side of point A = ,Ar ,Ar ,Ar( )s u sK Z Z−
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Fs,Bl: Spring forces at the left side of point B = ,Bl ,Bl ,Bl( )s u sK Z Z−
Fs,Br: Spring forces at the right side of point B = ,Br ,Br ,Br( )s u sK Z Z−
Fs,Cl: Spring forces at the left side of point C = ,Cl ,Cl ,Cl( )s u sK Z Z−
Fs,Cr: Spring forces at the right side of point C = ,Cr ,Cr ,Cr( )s u sK Z Z−
Fs,Dl: Spring forces at the left side of point D = ,Dl ,Dl ,Dl( )s u sK Z Z−
Fs,Dr: Spring forces at the right side of point D = ,Dr ,Dr ,Dr( )s u sK Z Z−
Ms: Sprung mass Zs: Vertical displacement of sprung mass at the body centre of gravity
Fa,Al, Fa,Ar, Fa,Bl, Fa,Br Fa,Cl, Fa,Cr, Fa,Dl, Fa,Dr: Hydraulic actuator forces at the left and right sides of point A, B, C and D, respectively, produced by active suspension system
Ks,Al, Ks,Ar, Ks,Bl, Ks,Br, Ks,Cl, Ks,Cr, Ks,Dl, Ks,Dr: Spring stiffness at the left and right sides of point A, B, C and D, respectively
,Al ,Ar ,Bl ,Br ,Cl ,Cr ,Dl ,Dr, , , , , , , :u u u u u u u uZ Z Z Z Z Z Z Z Unsprung masses displacement at the left and right sides of point A, B, C and D, respectively
,Al ,Ar ,Bl ,Br ,Cl ,Cr ,Dl ,Dr, , , , , , , :s s s s s s s sZ Z Z Z Z Z Z Z Sprung masses displacement at the left and right sides of point A, B, C and D, respectively.
Similarly, moment balance equations are derived for pitch ϕ and roll θ are given as
yy ,Cl ,Cl ,Cr ,Cr ,Dl ,Dl ,Dr
,Dr ,Al ,Al ,Ar ,Ar
,Bl ,Bl ,Br ,Br
( )( ) (
)( ) ( )( )( )( ) sin
a s a s a s a
s a s a s
a s a s e
I F F F F b g F F F
F c b g F F F F a gF F F F g eF
ϕ
β
= + + + − + + +
+ + − − + + + +
− + + + −
(2)
xx ,Al ,Al ,Bl ,Bl ,Cl ,Cl ,Dl ,Dl
,Ar ,Ar ,Br ,Br ,Cr ,Cr ,Dr ,Dr
( )( / 2) ( )( / 2) cos
a s a s a s a s
a s a s a s a s
e
I F F F F F F F Fd F F F F F F F Fd eF
θ
β
= + + + + + + +
× − + + + + + + +
× −
(3)
where
θ : Roll acceleration at body centre of gravity ϕ : Pitch acceleration at body centre of gravity Ixx: Roll axis moment of inertia Iyy: Pitch axis moment of inertia d: Track width of sprung mass Fe: External force due to the effect of firing a large-calibre missile from gun turret β: Angle of fire a: Distance from point A to B
Disturbance rejection control of a light armoured vehicle 157
b: Distance from point B to C c: Distance from C to D e: Distance from the centre of the turret gun to the body centre of gravity g: Distance from point B to the body centre of gravity.
By performing force balance analysis at the eight wheels, the following equations are obtained
,Al ,Al ,Al ,Alu u t a sM Z F F F= − − (4)
,Ar ,Ar ,Ar ,Aru u t a sM Z F F F= − − (5)
,Bl ,Bl ,Bl ,Blu u t a sM Z F F F= − − (6)
,Br ,Br ,Br ,Bru u t a sM Z F F F= − − (7)
,Cl ,Cl ,Cl ,Clu u t a sM Z F F F= − − (8)
,Cr ,Cr ,Cr ,Cru u t a sM Z F F F= − − (9)
,Dl ,Dl ,Dl ,Dlu u t a sM Z F F F= − − (10)
,Dr ,Dr ,Dr ,Dru u t a sM Z F F F= − − (11)
where Ft,Al: Tyre forces at the left side of point A = ,Al ,Al ,Al( )t r uK Z Z−
Ft,Ar: Tyre forces at the right side of point A = ,Ar ,Ar ,Ar( )t r uK Z Z−
Ft,Bl: Tyre forces at the left side of point B = ,Bl ,Bl ,Bl( )t r uK Z Z−
Ft,Br: Tyre forces at the right side of point B = ,Br ,Br ,Br( )t r uK Z Z−
Ft,Cl: Tyre forces at the left side of point C = ,Cl ,Cl ,Cl( )t r uK Z Z−
Ft,Cr: Tyre forces at the right side of point C = ,Cr ,Cr ,Cr( )t r uK Z Z−
Ft,Dl: Tyre forces at the left side of point D = ,Dl ,Dl ,Dl( )t r uK Z Z−
Ft,Dr: Tyre forces at the right side of point D = ,Dr ,Dr ,Dr( )t r uK Z Z−
,Al ,Ar ,Bl ,Br ,Cl ,Cr ,Dl ,Dr, , , , , , ,r r r r r r r rZ Z Z Z Z Z Z Z : Road profile inputs at the left and right sides of point A, B, C and D, respectively.
Displacement of the sprung masses at the left and right sides of point A, B, C and D depend on the sprung mass displacement at the body centre of gravity (Zs), pitch angle (ϕ) and roll angle (θ). The sprung mass displacement at point A, B, C and D are defined as the following:
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,Al ( )sin sin2s sdZ Z a g ϕ θ= − + + (12)
,Ar ( )sin sin2s sdZ Z a g ϕ θ= − + − (13)
,Bl sin sin2s sdZ Z g ϕ θ= − + (14)
,Br sin sin2s sdZ Z g ϕ θ= − − (15)
,Cl ( )sin sin2s sdZ Z b g ϕ θ= + − + (16)
,Cr ( )sin sin2s sdZ Z b g ϕ θ= + − − (17)
,Dl ( )sin sin2s sdZ Z c b g ϕ θ= + + − + (18)
,Dr ( )sin sin .2s sdZ Z c b g ϕ θ= + + − − (19)
3 Disturbance models
To study the performance of the controller, two types of disturbances are considered in this study, namely, the external force acting at the weapon platform while firing a large-calibre projectile from gun turret and the vertical force acting on the eight tyres. The external force acting at the weapon platform can be derived from Impulse – Momentum theorem. Impulse is the concept used to describe the effect of force acting on an object for a finite amount of time. Impulse is a measure of the change in linear momentum of the object affected by the force. Linear momentum is defined as the product of mass and velocity of an object.
Due to the energy from the burning gunpowder, the projectile is pushed out of the case and up the barrel. The characteristics of propellant powder are such that the peak gas pressures are generated almost immediately as the projectile begins its trip up the barrel. As the projectile accelerates up the barrel, it makes space for the gas to expand rapidly. This expansion, coupled with the friction between the projectile and the barrel, results in a final boost to the projectile so that its maximum velocity is attained just beyond the muzzle. The relationship between the impulse and momentum of the projectile leaving a muzzle comes from Newton's second law and is described as follow:
Fe = Mpap (20)
0( )p fe
M V VF
t−
=∆
(21)
Disturbance rejection control of a light armoured vehicle 159
where Fe: Force acting at the weapon platform Mp: Projectile mass ap: Acceleration of projectile Vf: Speed of projectile leaving the muzzle V0: Initial speed of the projectile ∆t: The time needed by the projectile to reach its maximum speed at the muzzle.
From Figure 1, the components of the external force acting at the weapon platform in the x and y directions depend on the angle of fire (β). The component of external force in x-direction generates unwanted pitch motion, whereas the component of external force in y-direction generates unwanted roll motion. It is assumed that the gun turret can only rotate in the horizontal plane of the weapon platform.
The second disturbance comes from road irregularities acting at the eight tyres of the light armoured vehicle. In this study, road profiles are assumed to be sinusoidal functions. The performances of the controller are evaluated using two types of road bump inputs, namely, roll mode bump and pitch mode bump. In roll mode bump, the sinusoidal road profiles between the left tyres and the right tyres of points A, B, C and D are set to be different in phase, whereas the amplitude and frequency of the sinusoidal functions are set the same. In pitch mode bump, left and right tyres have exactly the same sinusoidal road profile, but the sinusoidal road profiles acting on the pair of tyres at points A, B, C and D are set to be different in phase. Details of the sinusoidal road profile for roll mode and pitch mode bumps, including the parameters, can be seen in Section 5.
4 Controller structure of active suspension system for light armoured vehicle
The controller structure of the active suspension system for a light armoured vehicle is given in Figure 3. The controller structure is adopted from Campos et al. (1999) and Ikenaga et al. (2000), and is known as the SAS. The controller structure consists of inner loop controllers to reject the effect of road disturbances and outer loop controllers to stabilise heave, pitch and roll responses due to road disturbances or due to the effect of firing a large-calibre projectile from the gun turret. An input decoupling transformation is placed between the inner and outer loop controllers that blend the inner loop and outer loop controller. The inner loop controller provides the ride control that isolates the vehicle body from wheel vibrations induced by road irregularities and the outer loop controller provides the attitude control that maintains load-levelling and load distribution during vehicle manoeuvres.
The outputs of the outer loop controller are vertical forces to stabilise body bounce (Mz), moment to stabilise body pitch (Mϕ) and moment to stabilise roll (Mθ). Those forces and moments are then distributed into the target forces of the eight hydraulic actuators produced by the outer loop controller. Distribution of the force and moments into target forces of the eight hydraulic actuators is performed using a decoupling transformation subsystem. The outputs of the decoupling transformation subsystem, namely, the target forces of the eight hydraulic actuators are then subtracted from the relevant outputs of the inner loop controller to produce ideal target forces
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of the eight hydraulic actuators. Decoupling transformation subsystem requires an understanding of the system dynamics in the previous section. From equations (1)–(3), equivalent forces for heave, pitch and roll can be defined by
,Al ,Ar ,Bl ,Br ,Cl ,Cr ,Dl ,Drz a a a a a a a aF F F F F F F F F= + + + + + + + (22)
,Al ,Ar ,Bl ,Br
,Cl ,Cr ,Dl ,Dr
( ) ( ) ( ) ( )
( ) ( ) ( ) ( )a a a a
a a a a
M F a g F a g F g F g
F b g F b g F c b g F c b gϕ = − + − + − −
+ − + − + + − + + − (23)
,Al ,Ar ,Bl ,Br
,Cl ,Cr ,Dl ,Dr
2 2 2 2
.2 2 2 2
a a a a
a a a a
d d d dM F F F F
d d d dF F F F
θ = − + −
+ − + − (24)
Equations (22)–(24) can be rearranged in matrix format as follows
,Al
,Ar
,Bl
,Br
,Cl
,Cr
,Dl
,Dr
1 1 1 1 1 1 1 1( ) ( ) .
2 2 2 2 2 2 2 2
a
a
az
a
a
a
a
a
FFF
FF
M a g a g g g b g b g c b g c b gF
M d d d d d d d dFFF
ϕ
θ
= − + − + − − − − + − + − − − − −
(25)
For a linear system of equations y = Cx, if C ∈ ℜm × n has full row rank, and there exists a right inverse C–1 such that C–1C = I m × m. The right inverse can be computed using C–1 = CT(CCT)–1. Thus, the inverse relationship of equation (25) can be expressed as
,Al
,Ar
,Bl
,Br
,Cl
,Cr
,Dl
,Dr
1 1 12
1 102
11 0
1 2 12 4 4 ( 4 )
1 02 2
1 1 12
1 0
1 1 12
a
a
a
a
a
a
a
a
ga a d
dF gF a aF a g aF a g a g d a gF gF g b g bF gF b b d
b gc c
g bc c d
− − − − + + − + + + = − − − −
− − − − −
.zF
MM
ϕ
θ
(26)
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Figure 3 Controller structure of the light armoured vehicle with active suspension system
5 The results of simulation studies on the controller performance
This section describes the results of a simulation study of the performance of a stability augmentation based active suspension system for light armoured vehicle. The performance of a light armoured vehicle with a passive system is used as a basic benchmark. To investigate the advantage of additional ride controller to the SAS, the performance of the controller is also compared with SAS without the ride controller loop. This section begins by introducing all the parameters used in this simulation study, followed by a presentation of the controller performance in attenuating the effects of firing large-calibre projectiles from the turret gun, pitch mode road disturbance and roll mode road disturbance, respectively. The stability augmentation based active suspension system control is evaluated for its performance in controlling the dynamics of a light armoured vehicle according to the performance criteria of body acceleration or body displacement, body pitch rate, body pitch angle, body roll rate and body roll angle.
5.1 Simulation parameters
The simulation was performed for a period of 8 s using the Heun solver with a fixed step size of 0.01 s. The numerical values of the 12 DOF light armoured vehicle model parameters are set based on Pike (2006a, 2006b) and some of the values of parameters are assumed. These parameters are given in Table 1.
The light armoured vehicles of the mobile gun system considered in this study employ 105 mm tactical High Explosive Anti-Tank (HEAT) ammunition (Pike, 2006a), namely, 105 mm HEAT-MP-T. The parameters of 105 mm HEAT-MP-T (Anonymous, 2007), along with the angle of fire and the time needed by the projectile to reach its maximum speed at the muzzle, are as follows:
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Mp = 9.6 kg
Vf = 1330 m/s
β = π/3 rad
∆t = 0.25 s.
Road disturbances are modelled as sinusoidal functions with amplitudes of 0.1 m and frequency of 3 rad/s. The equations representing the road profiles in each tyre for roll and pitch mode bumps are given in Table 2.
Table 1 The numerical values of the light armoured vehicle model parameters
Vehicle parameters Suspension damper
parameters Suspension spring
parameters Tyre parameters Ms = 17,300 kg Mu,Al = 120 kg Cs,Al = 3000 Ns/m Ks,Al = 3000 Ns/m Kt,Al = 240,000 N/m a = 1.3 m Mu,Ar = 120 kg Cs,Ar = 3000 Ns/m Ks,Ar = 3000 Ns/m Kt,Ar = 240,000 N/m b = 1 m Mu,Bl = 120 kg Cs,Bl = 3000 Ns/m Ks,Bl = 3000 Ns/m Kt,Bl = 240,000 N/m c = 1.3 m Mu,Br = 120 kg Cs,Br = 3000 Ns/m Ks,Br = 3000 Ns/m Kt,Br = 240,000 N/m d = 2 m Mu,Cl = 12 kg Cs,Cl = 3000 Ns/m Ks,Cl = 3000 Ns/m Kt,Cl = 240,000 N/m e = 1 m Mu,Cr = 120 kg Cs,Cr = 3000 Ns/m Ks,Cr = 3000 Ns/m Kt,Cr = 240,000 N/m g = 0.75 m Mu,Dl = 120 kg Cs,Dl = 3000 Ns/m Ks,Dl = 3000 Ns/m Kt,Dl = 240,000 N/m Ixx = 1900 kg/m2 Mu,Dr = 120 kg Cs,Dr = 3000 Ns/m Ks,Dr = 3000 Ns/m Kt,Dr = 240,000 N/m Iyy = 5600 kg/m2
Table 2 Sinusoidal road profiles for each tyre
Roll mode bump Pitch mode bump
Left tyres Right tyres Left tyres Right tyres
Zr,Al = 0.1 sin 3t Zr,Ar = 0.1 sin (3t + π/2) Zr,Al = 0.1 sin 3t Zr,Ar = 0.1 sin 3t
Zr,Bl = 0.1 sin 3t Zr,Br = 0.1 sin (3t + π/2) Zr,Bl = 0.1 sin (3t + π/2) Zr,Br = 0.1 sin (3t + π/2) Zr,Cl = 0.1 sin 3t Zr,Cr = 0.1 sin (3t + π/2) Zr,Cl = 0.1 sin (3t + π) Zr,Cr = 0.1 sin (3t + π) Zr,Dl = 0.1 sin 3t Zr,Dr = 0.1 sin (3t + π/2) Zr,Dl = 0.1 sin (3t + 3π/2) Zr,Dr = 0.1 sin (3t + 3π/2)
In the design of the SAS controller, all the references are set to zero. The controller parameters for outer and inner loop controller are selected as follows:
Kx = 10,000 KAl = 6500 KDl = 6500 Bcl = 1200
Bx = 10,000 KAr = 6500 KDr = 6500 BCr = 1200
Kϕ = 10,000 KBl = 6500 BAl = 1200 BDl = 1200
Bϕ = 10,000 KBr = 6500 BAr = 1200 BDr = 1200
Kθ = 20,000 KCl = 6500 BBl = 1200
Bθ = 35,000 KCr = 6500 BBr = 1200
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5.2 Controller performance in attenuating the effects of firing a large-calibre projectile from gun turret
The simulation results of the controller performance in attenuating the effects of firing a large-calibre projectile from gun turret are shown in Figures 4–8. The body displacement performance of SAS with ride control is compared to the SAS without ride control along with the passive system, as shown in Figure 4. From the figure, it is clear that the active control with SAS is able to significantly reduce both the amplitude and the settling time of unwanted body motions in the forms of body displacement as compared with the passive system. It can also be noted that the additional ride controller loop to the SAS is able to slightly improve the performance of SAS.
Figure 4 Body displacement response due to firing a 105 mm calibre projectile
Figure 5 Pitch angle response due to firing a 105 mm calibre projectile
Figure 6 Pitch rate response due to firing a 105 mm calibre projectile
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Figure 7 Roll angle response due to firing a 105 mm calibre projectile
Figure 8 Roll rate response due to firing a 105 mm calibre projectile
The effects of roll and pitch motions while firing a large-calibre projectile from the gun turret can be reduced significantly by using a stability augmentation based active suspension system as shown in Figures 5–8. Again, an additional ride controller loop to the SAS is capable of further reducing unwanted motions of pitch and roll while firing 105 mm calibre projectiles. Since the light armoured vehicle is designed to be able to fire 18 rounds of 105 mm main gun ammunition in a certain short period, improvement of the dynamics performance in the first fire will enhance the accuracy and precision of firing and reduce human error in the subsequent firings. Reducing the settling time will also increase the speed of engagement and target acquisition.
5.3 Controller performance in attenuating the effects of pitch-mode road disturbance
The simulation results of body vertical acceleration and body displacement at the body centre of gravity on pitch mode bump road disturbance are shown in Figures 9 and 10 respectively. It can be seen that the performance of SAS with ride control is significantly better than the passive system and slightly better than SAS without ride control. It is also noted that the body acceleration performance of the SAS without ride control introduces spikes particularly during transient response. This is due to the fact that, without ride control, wheels oscillations are not properly damped out.
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Figure 9 Body acceleration response due to pitch mode road disturbance
Figure 10 Body displacement response due to pitch mode road disturbance
Similarly, in terms of pitch angle and pitch rate at the body centre of gravity, the performances of the active SAS with and without ride control are significantly better than passive system as shown in Figures 11 and 12, respectively. Again, the SAS system with ride control is able to slightly improve the pitch motion performance without allowing spikes and oscillations at the transient response, due to the unwanted motions transferred from the wheels. Improvement in pitch motion can enhance the accuracy and precision of firing in longitudinal direction.
Figure 11 Pitch angle response due to pitch mode road disturbance
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Figure 12 Pitch rate response due to pitch mode road disturbance
5.4 Controller performance in attenuating the effects of roll-mode road disturbance
The simulation result of the body’s vertical acceleration and body’s displacement at the body centre of gravity on pitch mode road disturbance are shown in Figures 13 and 14, respectively. Approximately, the amplitude of the body’s acceleration and body’s displacement of the passive system can be reduced by about half by using the active suspension system. It can be seen that the performance of the SAS with ride control is significantly better than the passive system and slightly better than SAS without ride control. It is also noted that the body acceleration performance of the SAS without ride control introduces excessive spikes particularly during transient response due to the poor damping.
The amplitudes of roll angle and roll rate at the body centre of gravity cannot significantly be reduced using active SAS with and without ride control for roll mode road disturbance as shown in Figures 15 and 16, respectively. But it can be noted that the active suspension system is able to remove excessive motion during transient response as it happened with the passive system. Again, the SAS with ride control is able to slightly improve the roll motion performance without allowing spikes and oscillations at the transient response due to the unwanted motions transferred from the wheels. Improvement in roll motion can enhance the accuracy and precision of firing in the lateral direction.
Figure 13 Body acceleration response due to roll mode road disturbance
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Figure 14 Body displacement response due to roll mode road disturbance
Figure 15 Roll angle response due to roll mode road disturbance
Figure 16 Roll rate response due to roll mode road disturbance
6 Conclusions
A 12 DOF model of a light armoured vehicle has been developed and derived mathematically in this study. A controller structure, namely, SAS, which has two controller loops of attitude control and ride control has been implemented in controlling the active suspension system for the light armoured vehicle. Simulation studies have been performed by considering two sources of disturbances, namely, external force acting on the weapon platform due to firing a large calibre gun and external force due to road irregularities. The performance of the proposed SAS with ride controller loop is compared with the passive system, along with SAS, without the ride controller loop.
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From the simulation results, it is clear that active suspension control using SAS with and without the ride controller loop are able to significantly reduce both the amplitude and the settling time of unwanted body motions in the form of body displacement, body acceleration, roll angle, roll rate, pitch angle and pitch rate as compared with the passive system. It can also be noted that the additional ride controller loop to the SAS is able to improve the performance of SAS slightly. Reduction of unwanted motions and settling time of the light armoured vehicle in the presence of disturbances indicate that the accuracy and precision of firing in both longitudinal and lateral directions can be enhanced using the active control suspension system. Reducing the settling time also indicates that the speed of engagement and target acquisition can be increased using an active control suspension system.
7 Suggestion for future works
The paper presents a mathematical model that incorporates the angular motion of the weapon station and predicts the vehicle responses under both road and firing inputs. The model is used to develop and verify the control algorithms based upon SAS, with the purpose of reducing the unwanted sprung mass motions resulting from firing loads and road irregularities. It is necessary to validate the behaviour of the proposed model with the behaviour of the real LAV system. An instrumented experimental LAV system needs to be developed for validation purposes. More realistic external disturbances, such as random road profile and firing loads, can be implemented on both the 12 DOF LAV model and the instrumented experimental vehicle to verify the accuracy of the proposed LAV model.
References Anonymous (2007) Large Calibre Ammunition: 105 mm HEAT-MP-T, Retrieved January, from
http://www.atk.com Beno, J.H., Weeks, D., Bresie, D., Ingram, K. and Guenin, A. (1997) Control System for Single
Wheel Station Heavy Tracked Vehicle Active Electromagnetic Suspension, SAE Technical Paper in International Congress & Exposition on Commercial Applications for Military Technologies, February, Detroit, MI, USA.
Buckner, G.D., Schuetze, K.T. and Beno, J.H. (2001) ‘Intelligent feedback linearization for active vehicle suspension control’, Journal of Dynamic Systems, Measurement, and Control. Vol. 123, No. 4, pp.727–733.
Campos, J., Davis, L., Lewis, F.L., Ikenaga, S., Scully, S. and Evans, M. (1999) ‘Active suspension control of ground vehicle heave and pitch motions’, Proceedings of the 27th IEEE Mediterranean Conference on Control and Automation, June, Haifa, Israel, pp.222–233.
Choi, S.B., Park, D.W. and Suh, M.S. (2002) ‘Fuzzy sky-ground hook control of a tracked vehicle featuring semi-active electrorheological suspension units’, Journal of Dynamic Systems, Measurement, and Control, Vol. 124, No. 1, pp.150–157.
Hayes, R.J., Beno, J.H., Weeks, D.A., Guenin, A.M., Mock, J.R., Worthington, M.S., Triche, E.J., Chojecki, D. and Lippert, D. (2005) Design and Testing of an Active Suspension System for a 2-1/2 Ton Military Truck, SAE Technical Paper in World Congress & Exhibition on Steering and Suspension Technology, April, Detroit, MI, USA.
Hoogterp, F.B., Eiler, M.K. and Mackie, W.J. (1996) Active Suspension in the Automotive Industry and the Military, SAE Technical Paper Series, Paper No. 961037.
Disturbance rejection control of a light armoured vehicle 169
Ikenaga, S., Lewis, F.L., Campos, J. and Davis, L. (2000) ‘Active suspension control of ground vehicle based on a full vehicle model’, Proceedings of the 2000 American Control Conference, 28–30 June, Vol. 6, Illinois, Chicago, pp.4019–4024.
Kanagawa, K., Nowada, S., Inoue, Y., Okazawa, T. and Hashimoto, M. (1995) ‘Active suspension of heavy tracked vehicle – Part 1: bench test’, JSAE Review, Vol. 16, No. 3, pp.323–333.
Kanagawa, K., Mori, T., Inoue, Y., Okazawa, T., Hashimoto, M. and Nowada, S. (1996) ‘Active suspension of heavy tracked vehicle – Part 2: vehicle test’, JSAE Review, Vol. 17, No. 4, pp.433–444.
Maclaurin, B. (1983) Progress in British Tracked Vehicle Suspension Systems, SAE Technical Paper Series, Paper No. 830442.
Miller, L.R. and Nobles, C.M. (1988) The Design and Development of a Semi-Active Suspension for a Military Tank, SAE Technical Paper Series, Paper No. 881133.
Pike, J. (2006a) M1128 Stryker Mobile Gun System, Retrieved October, from http:// www.globalsecurity.org/military/systems/ground/iav-mgs.htm
Pike, J. (2006b) Stryker Armoured Vehicle, Retrieved October, from http://www.globalsecurity.org/ military/systems/ground/iav.htm
Wendel, G.R., Steiber, J. and Stecklein, G.L. (1994) Regenerative Active Suspension on Rough Terrain Vehicles, SAE Technical Paper Series, Paper No. 940984.
Weeks, D., Bresie, D., Guenin, A. and Beno, J.H. (1999) The Design of an Electromagnetic Linear Actuator for an Active Suspension, SAE Technical Paper in International Congress & Exposition on Steering & Suspension Technology, March, Detroit, MI, USA.
Youn, I., Im, J., Shin, H., Lee, J. and Shin, M. (2001) ‘Performance evaluation of control algorithms for 1/2 tracked vehicle with semi-active suspension system’, Journal Korean Society Automotive Engineers, Vol. 9, No. 4, pp.139−147.
Youn, I., Lee, S. and Tomizuka, M. (2006) ‘Optimal preview control of tracked vehicle suspension system’, International Journal of Automotive Technology, Vol. 7, No. 4, pp.469–475.
