Comparison of active and semi active suspension systems using robust controller

e-ISSN: 2582-5208
International Research Journal of Modernization in Engineering Technology and Science
Volume:02/Issue:03/March-2020 www.irjmets.com
www.irjmets.com @International Research Journal of Modernization in Engineering, Technology and Science
[136]
COMPARISON OF ACTIVE AND SEMI-ACTIVE SUSPENSION SYSTEMS
USING ROBUST CONTROLLER
Mustefa Jibril*1
, Eliyas Alemayehu Tadese*2
*1
Dept. of Electrical & Computer Engineering, Dire Dawa Institute of Technology, Dire Dawa, Ethiopia,
*2
Faculty of Electrical & Computer Engineering, Jimma Institute of Technology, Jimma, Ethiopia
ABSTRACT
Suspension system is used to fulfil the criteria of ride comfort and road handling. In this paper, a quarter car active
& semi-active suspension systems are designed using Matlab/Script software. Comparison of active & semi-active
suspension systems are done using robust control theory for the control targets suspension deflection, body
acceleration and body travel. H infinity controller is selected to compare the two suspensions using time domain
analysis. Finally the simulation result prove the effectiveness of the active suspension system by decreasing the body
acceleration & sustaining the suspension deflection and body travel outputs.
Keywords- Active suspension system, semi-active suspension system, H infinity controller
I. INTRODUCTION
Semi-active suspension is one of the suspension that elastic parameter stiffness and shock absorber damping can
adjust according to the need for adjustment and control. Skyhook semi-active suspension concept was proposed
in1974. The spring stiffness tuning is very difficult, so semi-active suspension mainly by adjusting the shock
absorber damping.
Semi-active suspension system has no specifically dynamic control components. It passed the velocity sensors data
to the instrument ECU supervisor to calculate the required control force, and then adjust the shock absorber damping
to attenuate shock of the automobile body. The study of semi-active suspensions are also focused on two aspects,
one is on the designing of actuator, which is the damping adjustable shock absorbers; the other hand, the control
methodology. Magneto rheological damper is the semi-active suspension latest technology and lots of researcher’s
exhibition great interests on this new technology. It has a fast response, which is lower than 1ms. Semi-active
suspension also has its own advantages, such as its scheme amount and prix is greatly lower than the active
suspension system.
The automotive active suspension, according to progress conditions and automobile load, controls their own
operations status. Active suspension need to take effective control strategy to make the suspension to achieve the
achievement required to achieve, therefore, the picks of control strategy for controllable suspension has a great
demeanor of performance.
II. MATHEMATICAL MODELS
2.1 Active Suspension System Mathematical Model
Active suspension systems with hydraulic actuators to the passive components of suspension system as shown in
Figure 1.
Figure 1: Quarter model of active suspension system.

e-ISSN: 2582-5208
[137]
The equations of motion are written as
     0 1s s s s us a s us aM z k z z c z z U       
       0 2us us us s a us s t us r aM z z z c z z k z z U         
Where uais the control force from the hydraulic actuator. It can be noted that if the control force ua= 0.
2.2 Semi-active Suspension System Mathematical Model
The design of the quarter car semi-active suspension system diagram is shown in Figure 2 below.
Figure 2: Quarter model of semi-active suspension system.
     3s us s a us s s sK Z Z C Z Z M Z     
       4s us s a us s t r us us usK Z Z C Z Z K Z Z M Z        
Where Zs is the position of the sprung mass, Zus is the position of the unsprung mass and Zr is the road
displacement. These equations are solved numerically using MATLAB’s dynamic system simulation software,
SIMULINK
III. ROAD PROFILES
3.1 Random Road Profile
The random road disturbance input has a maximum peak of 15 cm and minimum peak of -15 cm as shown in Fig 3.
Figure 3: Random road profile

e-ISSN: 2582-5208
[138]
3.2 Sine Road Profile
The sine road disturbance input has a maximum peak of 10 cm and minimum peak of -10 cm as shown in Figure 4.
Figure 4: Random road profile
IV. THE PROPOSED CONTROLLER DESIGN
4.1 Active Suspension Design
The active suspension system with Hcontroller witha third order hydraulic actuator system block diagram is
shown in Figure 5.
Figure 5: Active suspension system with Hcontroller system block diagram
The hydraulic actuator model is a third order transfer function defined as:
 3 2
2
5
5 6
2
4
1
actuator
s
s s
s s
 

  
4.2 Semi-active Suspension Design
The semi-active suspension system with H controllersystem block diagram is shown in Figure 6.
Figure 6: Semi-active suspension system with Hcontroller system block diagram

e-ISSN: 2582-5208
[139]
V. RESULT AND DISCUSSION
The quarter car active and semi-active suspension system parameter values are shown in Table 1.
Table 1: Parameters of quarter vehicle model
Model parameters symbol symbol Values
Vehicle body mass
sM 415 Kg
Wheel assembly mass
usM 53 Kg
Suspension stiffness
sk 10,500 N/m
Tire stiffness
tk 130,000 N/m
Suspension damping
ac 900 N-s/m
5.1 Control Targets Output Specifications
The control targets output specifications of the quarter car active & semi-active suspension system is shown in Table
2 below.
Table 2. Control targets output specifications
No Control Targets Output
1 Body travel Minimum
2 Body acceleration Minimum
3 Suspension
deflection
Same as Road
Profile
5.2 Simulation of a Random Road Disturbance
The body travel, body acceleration and suspension deflection simulation result of the active and semi-active
suspension system with Hcontroller for a random road disturbance is shown in Figure 7, Figure 8 and Figure 9
respectively.
Figure 7: Body travel for random road disturbance

e-ISSN: 2582-5208
[140]
Figure 8: Body acceleration for random road disturbance
Figure 9: Suspension deflection for random road disturbance
5.3 Simulation of a Sine Input Road Disturbance
The body travel, body acceleration and suspension deflection simulation result of the active and semi-active
suspension system with Hcontroller for a sine road disturbance is shown in Figure 10, Figure 11 and Figure 12
respectively.
Figure 10: Body travel for sine road disturbance

e-ISSN: 2582-5208
[141]
Figure 11: Body acceleration for sine road disturbance
Figure 12: Suspension deflection for sine road disturbance
5.3 Numerical Values of the Simulation Outputs
The numerical result of the simulation of body travel, body acceleration and suspension deflection is shown in Table
3, Table 4 and Table 5 bellow.
Table 3: Numerical values of the body travel simulation result
No Systems Random Sine
1 Road Profile 0.15m 0.1m
2 Semi-active 0.09m 0.01m
3 Active 0.01m 0.01m
Table 2 shows us the active suspension system with Hcontroller have the minimum body travel amplitude in the
random road profile and equal amplitude in the sine road profile.

e-ISSN: 2582-5208
[142]
Table 4: Numerical values of the body acceleration simulation output
1 Road Profile 5 m/ s 2 2 m/ s 2
2 Semi-active 80 m/ s 2 45 m/ s 2
3 Active 20 m/ s 2 18 m/ s 2
Table 3 shows us the active suspension system with Hcontroller have the minimum body acceleration amplitude
in the random and sine road profile.
Table 5: Numerical values of the suspension deflection simulation output
1 Road Profile 0.14m 0.1m
2 Semi-active 0.05m 0.1m
3 Active 0.14m 0.1m
Table 4 shows us the active suspension system with Hcontroller have the suspension deflection amplitude the
same as the road profile input in the random and sine road profiles.
VI. CONCLUSION
The methodology was developed to design an active suspension for a passenger car by designing a controller, which
improves performance of the system with respect to design goals compared to semi-active suspension system.
Mathematical modelling has been performed using a two degree-of-freedom model of the quarter car model for
active and semi-active suspension system considering the three control targets to evaluate the performance of
suspension with respect to various contradicting design goals. H infinity controller design approach has been
examined for the comparison of the active & semi-active suspension systems. The potential for improved ride
comfort and better road handling using H infinity controller for the design of the active & semi-active suspension
systems is examined. The objectives of this project have been achieved. Dynamic model for linear quarter car
suspensions systems has been formulated and derived only one type of controller is used to test the systems
performance which is H infinity controller. Finally the simulation result prove that the active suspension system has
better performance.
VII. REFERENCES
[1]. Mustefa. J “H ∞ and μ -synthesis Design of Quarter Car Active SuspensionSystem” International Journal of
Scientific Research and Engineering Development-– Volume 3 Issues 1 Jan- Feb, 2020.
[2]. Mustefa. J “Comparison of H∞ and μ-synthesis Control Design for QuarterCar Active Suspension System using
Simulink” International Journal of Scientific Research and Engineering Development-– Volume 3 Issues 1 Jan-
Feb, 2020.

e-ISSN: 2582-5208
[143]
[3]. Ahmed M.R et al. “Adjustable Valve Semi-active Suspension System for Passenger Car” International Journal
of Automotive and Mechanical Engineering, Vol. 16, No. 2, 2019.
[4]. Zhen-Ning et al. “Control of a ¼ MR Semi-active Suspension System using a RC Hysteresis Model for MR
Damper” Proceedings Volume 10595, Active and Passive Smart Structures and Integrated Systems XII, 2018.
[5]. Iftikhar Ahmed et al. “A Comparative Analysis of Linear and Nonlinear Semi-active Suspension System”
Mehran University Research Journal of Engineering and Technology, Vol. 37, No. 2, 2018.
[6]. Haifa souilem et al. “Sliding Mode Control of Half Car Active Suspension” International Journal of Computer
Applications, Vol. 155, 2016.

Comparison of active and semi active suspension systems using robust controller

More Related Content

What's hot (19)

Similar to Comparison of active and semi active suspension systems using robust controller (20)

More from Mustefa Jibril (20)

Recently uploaded (20)

Comparison of active and semi active suspension systems using robust controller