AL-Qadisiya Journal For Engineering Sciences ,Vol. 6.No 3 Year 2013 803 AN ACTIVE SELF-TUNING SUSPENION SYSTEM TO IMPROVE DRIVER COMFORT Dr. Salim Y. Kasim Salim56y@yahoo.com Mech. Eng. Department, College of Eng., Tikrit University ABSTRACT This paper presents the simulation of two dimension a half-vehicle self –tuning active suspension system to simultaneously improve vehicle ride comfort. A validated 4-DOF of vehicle linear model was used to study the performance of passive suspension system and compared with the developed active suspension system. The governing equations of motion for the self- tuning active suspension was derived and used to reduce the effect of disturbances to the dynamics performance of the vehicle, which appear when the vehicle excited by a semi-circular sinusoidal bump road of a (0.1 m) height. The performance of passive suspension and the self-tuning active suspension are demonstrated by simulations and specially the vertical acceleration and the vertical root mean square (RMS) acceleration to observe the effect of the proposed system to the ride comfort. The active suspension system introduced in this work show good results for improving the ride comfort. Keywords: Self-tuning active suspension, ride comfort. نظام تعليق ذو تضبيط ذاتي فعال لتحسين راحة السائق د. سالم يحيى قاسم تكريت/ كلية الهندسة/ قسم الهندسة الميكانيكيةجامعة الخالصة: فعال نظاِم تعليقِ تحتوي على مركبةِ ِنْصف لموديل ثنائي البعد خطي ذو اربع درجات من الحرية لمحاكاَة في هذا البحث نموذج عمُل لِدراَسة أداِء نظاِم التعليِق السلبيِ خطي َكاَن ُيستَ استند البحث على نموذج بشكل آني. كباالر َتْضبيط ذاتِي لَتحسين راحِة ذو تأثير واستخدمت بتقليل التعليَق النشيَط لنظام المعادالت الَحاِكمة للحركِة تم اشتقاق بنظاِم التعليِق النشيِط المطوِر. للمقارنة هشكل نصف دائري لموجية جيبي بصدمة طريق على العربَة عندما تثار، الذي َيْظهُر مركبةأداِء ديناميكا العلى االضطرابات بالمحاكاِة وخصوصًا التعجيِل العموديِ تم عرضه. إّن أداَء التعليِق السلبِي وتعليِق الَتْضبيط الذاتِي النشيِط متر 0.1 بارتفاع AL-Qadisiya Journal For Engineering Sciences ,Vol. 6.No 3 Year 2013 803 نظام التعليِق تظهران وقد وجد انه هناك نتائج كب .الراراحِة علىلُمالَحَظة تأثيِر النظاِم الُمقَتَرِح ومعدل مربع الجذر للتعجيل الراكب.نتائج جيدة لَتحسين راحِة قد اعطى البحثِ في هذا المقدم النشيِط NOMENCLATURE Ms Sprung mass Mu Un sprung mass. Vertical acceleration of sprung mass. Vertical velocity of sprung mass. Vertical displacement of sprung mass Main suspension coefficient of damping. Main suspension stiffness. The centre of tyer (wheel) vertical displacement. The centre of tyer (wheel) vertical velocity. The sprung mass CG Vertical acceleration. The centre of tyer (wheel) vertical acceleration. Road profile vertical amplitude. Ca Self-tuning Damper coefficient of damping. The force frequency. C.G The sprung mass center of gravity. INTRODUCTION: Ride quality and handling performance of road vehicles are very much affected by the design of the vehicle suspension systems. Good ride quality requires high damping setting at low frequencies to stifle bounce, roll and pitch, and lower damping settings at higher frequencies to avoid ride harshness. Unlike passive systems, which can only store or dissipate energy, active suspensions can continuously change the energy flow to or from the system when required, recently, the subject of active suspension design has been intensively reviewed by Jean-Gabriel Roumy [1], M .Frechin [2], and Mario Milanese and Carlo Novara [3], a simulation procedures by Jean-Gabriel Roumy [4], and Pakharuddin Mohd Samin, Hishamuddin Jamaluddin [5] . An optimization of active suspensions by applying methods of modern control theory has been reported by Bassam A. [6]. The vehicle suspension provides a means of isolating the vehicle’s body from the road inputs. Several aspects of vehicle dynamics put different demands on the various suspension components. Occupant comfort requires the minimization of sprung mass accelerations, while lateral dynamic performance requires good road holding giving rise to a need for consistent normal forces at the tire AL-Qadisiya Journal For Engineering Sciences ,Vol. 6.No 3 Year 2013 810 interface. This all has to work within suspension rattle space and tire deflection limitations. In a passive suspension each improvement comes at the expense of performance in another area [10].In this work, it is proposed to develop an analytical self-tuning active suspension to effectively reduce the vehicle body acceleration for ride comfort, dynamic tyers deflections and body attitude for ride handling and suspension deflections for the purpose of packaging by means of active suspensions governing equations of motion. The objectives include: (1) Development of a half car model, which is adequate for understanding the effect of road disturbances on the ride and handling characteristics of the vehicle; (2) Deriving the optimal governing equations of motions of a self -tuning active system (3) Investigating the possibilities of performance improvements using the passive and active developed system for a simulation to see the vibration response of wheel center behavior and the C.G acceleration to study its effects on ride comfort. ANALYTICAL FORMULATION: 1. Model of Vehicle Ride Dynamics: The two dimensional 4-DOF half vehicle model as shown in figure 1 is based on a passive FEM vehicle model being validated by simulation results by Salim Y. Kasim [7], So in this work the passive suspension is replaced with an self-tuning active suspension which is represented parallel damper to the passive one, vertical motion in the z- direction, pitch motions about the pitch pole. It also consist two unsprung masses which are free to bounce vertically with respect to the sprung mass. The vehicle model parameters data used for the simulation were taken from [9] as shown in table (1). 2. Vehicle Model Governing Equations: The equations governing the dynamic motion of the vehicle model equipped with self-tuning active and passive suspension systems can be expressed in the following state form: ) ( ) (1) ) ( ) (2) Where: ): Self-tuning Damper force. And the amplitude of vibration for both sprung and un sprung masses can be written as follows: The vertical amplitude of vibration of the vehicle sprung mass is: (3) And the vertical amplitude of vibration of the un sprung mass is: (4) The displacements, velocity, and acceleration with respect to time can be obtained. 3. Vehicle and Bump Road Input: The input excitation to the vehicle model is assumed to be the apparent vertical roadway motion, caused by the vehicle’s forward speed along a road having a semi-circular sinusoidal profile of 0.1 meter amplitude and 0.6 meter length as shown in figure 8. The vehicle excitation model can be obtained in the shape of vertical elevation and horizontal distance as tabulated input. AL-Qadisiya Journal For Engineering Sciences ,Vol. 6.No 3 Year 2013 811 RESULTS AND DISCUSSIONS: A new approach of an active suspension self- tuning damper has been achieved, according to the results it clear that from the observation of the front and rear road wheels vertical displacement shown in figure (2), that the amplitude have been reduced to about the half . also in figure (4) it is clear that the in addition to a code contact between the road wheel and the terrain the vertical spring mass C.G's amplitude is reduced from which one can deduced the results shown in figure (3) with high response and low settling time. The root mean square (RMS) acceleration is one of a ride comfort criteria which is shown in figure (5) for a smooth low values in active compared to that in the passive one. In the low speed of the vehicle in both case active and passive there are deference in the response can be observed the reason is that a good contact were exist between the road profile and the tyre, but the deferent is appear small when the speed is increased, except at some speeds mainly at 40 km/h which is seem to be the critical speed, these facts can be observed in figures (5) and (7). And in this case a sudden shock can be avoided when the speed of the vehicle has increased. The proposed system show a good time response if we checked the simulation time and the length of the road bump which is 0.6 meter and the critical time need from the system to reply is about two second in this case we need a high response system and it is clear from the results shown in figures (2 through 7) that the system has managed to do. And the reduction of the vertical acceleration is about 2 times. It means that the proposed system has achieved the objects CONCLUSION: A self- tuning suspension simulation system based on an additional damper added to the passive one in a 2-D half vehicle 4 DOF model the new damper has the ability to modified itself according to the irregular road profile after it received a signal from the detector where it can be achieved on reading the input tabulated data before the first wheel reach it, and adjust itself to maintained a suitable damping help for overcome the non-uniformly road to make the ride comfort be better. The results have shown that the proposed system has achieved the aim. REFRANCES: 1. Jean-Gabriel Roumy, Benoit Boulet and Dany Dionne (Active control of vibrations transmitted through a car suspension), Int. J. Vehicle Autonomous Systems, Vol. 2, Nos. 3/4, 2004. 2. M Frechin1, S B Arin˜o and J Fontain (ACTISEAT: active vehicle seat for acceleration Compensation), IMechE 2004 3. Mario Milanese and Carlo Novara (Experimental modeling of vertical dynamics of vehicles with controlled suspension), 2004 SAE International. 4. Jean-Gabriel Roumy*, Benoit Boulet and Dany Dionne (Active control of vibrations transmitted through a car suspension), 2004 Inderscience Enterprises Ltd. 5. Pakharuddin Mohd Samin, Hishamuddin Jamaluddin (SEMI-ACTIVE SUSPENSION FOR RIDE IMPROVEMENT USING STABILITY AUGMENTATION SYSTEM CONTROL ALGORITHM), Jurnal Mekanikal December 2008, No. 26, 86 – 95 6. Bassam A. AlBassam , Ahmad A. Fayed, and Mohamed M. ElMadany (Optimal linear preview control of slow- active suspension systems) Proceedings of the 7th Saudi Engineering Conference (SEC7) 7. Salim Y. Kasim ' Ride Analysis for Suspension System of Off-Road Tracked Vehicles' PhD thesis 1990-1991 AL-Qadisiya Journal For Engineering Sciences ,Vol. 6.No 3 Year 2013 813 8. Judi-Chun Chang (Analysis of series type and parallel type active Suspension systems), Hsinchu, Taiwan, November, 7, 2007 9.Vehicle Suspension Modeling MECE 4333 - Vehicle Systems Modeling and Control The University of Texas - Pan American August 7, 2006 10. D. Geoff Rideout ,and Keith J. Wakeham ( Model complexity requirements in design of half car active suspension controllers) Proc. ASME Dynamic Systems and Controls Conference, Arlington, VA Oct. 31-Nov.2, 2011 Figure(2) comparison of unsprung Mass Displacement Vs Time At 20 km/h Figure (1) 2-D Half car model with self -tuning suspension. Tuning AL-Qadisiya Journal For Engineering Sciences ,Vol. 6.No 3 Year 2013 818 Fig (3) Sprung Mass C.G Vertical Acceleration Vs Time At 20 Km/h Fig( 4) Front wheel , sprung mass C.G displacements , and road test bump profile Vs Time at low speed (Active). Fig (5) Sprung Mass C.G root mean square Vs vehicle speeds Fig (6) Sprung Mass C.G Pitch angle Vs Time At 20 Km/h AL-Qadisiya Journal For Engineering Sciences ,Vol. 6.No 3 Year 2013 813 Fig (7) Sprung Mass C.G maximum acceleration Vs vehicle speeds. Figure(8) The test bump road used in this study.