Research on the Coordination Control of Vehicle EPS and ABS

Transcription

1 Reseach on the Coodination Contol o Vehicle EPS and ABS Weihua Qin, Qidong Wang, Wuwei Chen, and Shenghui Pan School o Mechanical and Automotive Engineeing, Heei Univesity o Technology, Heei , China happy_qwh02@63.com Abstact. Based on the multibody dynamics model o Electic Powe Steeing System(EPS) and the lateal and longitudinal dynamics vehicle model, the EPS and Anti-lock Baking System (ABS) sub-contolles and the coodination contolle ae espectively designed accoding to the motion coupling elation between the steeing system and the baking system. The coodination contolle supevises and coodinates each sub-contolle as the uppe contolle. The simulation unde Matlab and the vehicle test with hadwae-in-the-loop(hil) based on LabVIEW have evaluated, tested and veiied the vehicle maneuveability and baking peomance unde coodination contol. The esults show that the coodination contol eectively impoved the compehensive peomance o vehicle, and the application o multibody dynamics model and hadwae-in-the-loop test wee convenient and easible in the coodination contol eseach o vehicle chassis. Keywods: Multibody dynamics,electic powe steeing system,anti-lock baking system, Coodination contol, Hadwae in the loop. Intoduction EPS and ABS o vehicles ae two impotant electic contol systems in the chassis. Howeve, unde the combined condition o steeing and baking, due to existence o the limit o tie iction, steeing system inteacts with the baking system. It can be known om the cuve diagam[] o elation between the tie-oad iction coeicient and the wheel slip ate at one slip angle in the vehicle theoy that: when the slip ate is small (less than about 0%), the vehicle s lateal iction coeicient is lage and the lateal stability is good, but the longitudinal iction coeicient is small and the baking peomance deceases; when the slip ate is inceased to about 0% 30%, the longitudinal iction coeicient inceases, but the lateal stability deceases; with the incease o the tie s slip angle, the slip ate coesponding to longitudinal peak iction coeicient also inceases. The dynamic chaacteistics o vehicle unde the combined conditions o steeing and baking wee eseached in the documents[2-3], and its inluence by steeing was also taken into account in some documents duing the design o ABS contol system[4], but its inluence by baking was less consideed duing the design o EPS contol system. In this thesis, the eseach on coodination contol o EPS and ABS is caied out, based on the stategy o the ule-based Y. Tan, Y. Shi, and K.C. Tan (Eds.): ICSI 200, Pat II, LNCS 646, pp , 200. Spinge-Velag Belin Heidelbeg 200

2 300 W. Qin et al. hieachical coodination contol. Such contol stuctue can shoten the contolle s development cycle and is easy to guaantee the contol eect; and multibody dynamics model o EPS is applied into the coodination contol eseach and a dynamical equations set is established though the constaint elation between the membes, which can embody the nonlinea elation between steeing input and steeing wheel output and descibe the inluence on the vehicle s steeing motion and the intenal stess o the steeing system moe accuately o the change o woking condition (tie-oad iction and vehicle speed, etc.). The hadwae-in-the-loop test is a test method which can connect the sotwae and actual hadwae like actuato to the system cicuit, and has become an impotant development appoach o the vehicle contol system, and has been widely used in the design o apid contol pototype[5-6]. LabVIEW is a sotwae platom based on gaphical pogamming language, which can conduct seamless integation with hadwae though the open sotwae envionment, so as to complete the simulation and ealization o the contol system. In this thesis, the eectiveness o contol stategy has been validated though the simulation and HIL test based on LabVIEW. 2 System Model 2. EPS Multibody Dynamics Model A multibody dynamics model o the steeing column assisted o ack-and-pinion electic powe assisted steeing system is established by the Catesian coodinates method. The dynamic equation[7] based on Catesian coodinates is Z Φ T q& q z = () Φq 0 σ γ Wheein: Φ Jacobian matix q σ Lagange multiplie matix Z Genealized mass matix γ Right items o the acceleation equations z Genealized oce matix. 2.2 Vehicle Model The longitudinal, lateal and yaw motion model is applied. The vehicle is egaded as a single mass igid body that conducts ee motion in the plane x y. The dynamic equation o the vehicle is established as Equation (). In the model, the genealized Catesian coodinates is: q = [ x y ψ] T The yaw velocityω = ψ&, in which the owad velocity along the diection o x is set as u and the lateal velocity along the diection o y is set as v. It is conveted by the coodinates to get: a = u& x v ω (2) ay = u ω + v&

3 Reseach on the Coodination Contol o Vehicle EPS and ABS 30 Foce element z = [ n] T, x y x = Fx cosδ + Fx 2 Fy sinδ. (3) y = Fy cosδ + Fy 2 + Fx sinδ. (4) n = l Fy cosδ l Fy 2 + l Fx sin δ (5) Wheein: F x, i F y Longitudinal and Lateal oce exeted to ont and ea i wheels( i =, 2) l, l Distance om ont and ea wheels to mass cente. 2.3 Baking System Model Equations o wheel olling motion: Iω& = FxR T. (6) b I 2ω& = Fx 2R2 Tb 2. (7) Wheein: I i Wheel mass otational inetia o ont and ea wheels( i =,2) ω, ω Angula velocity at ont and ea wheel R i Rolling adius o ont and ea wheel ( i =, 2) T bi Bake toque [8]. 2.4 Tye Model The PACEJKA nonlinea tie model unde the combined condition is applied. The equation can be seen in pape[9]. 3 Contolle Design Owing to the coupling elations between steeing and baking, each sub-contolle is designed with two woking modes accoding to the sequence o contol objectives unde dieent woking conditions. The coodination contolle has the ollowing unctions: giving the switching command between the two woking modes o the subsystems accoding to the identiication o the dive s intention and the vehicle s motion state and the supevision and detection to the subsystems, alteing the contol paametes o the sub-contolles, to guaantee the best oveall contol eect. 3. ABS Contolle () Nomal mode. In ode to guaantee the baking peomance, the contol stategy o sliding mode vaiable stuctue, based on the popotional switching unction, is applied. Take the dieence e between the actual slip ate λ and the expected slip λ and e& as input vaiable; and take the vaiation p o bake oil pessue as output ate 0 vaiable. The expected slip ate is taken as 0.2.

4 302 W. Qin et al. The switching unction is s = ce + e&, in which c is slope atio. By the contol method o popotional switching, the omula is p = ( α e + β e& )sgn( s). (8) Wheein, α and β ae the constants that ae lage than 0. (2) Steeing mode. Duing simultaneous steeing and baking, in ode to guaantee the compehensive peomance o the vehicle in tems o lateal and longitudinal dynamics, adjust the value o the expected slip ate λ 0 in eal time. 3.2 EPS Contolle ()Nomal mode. In ode to impove the steeing potability, the contol stategy o Fuzzy Neual Netwok is adopted. The vehicle speed and toque o steeing wheel ae uzziied by Gaussian membeship unction, and the uzzy ineence ule is Mamdani. The thee layes in the middle o the stuctue ae the BP neual netwok, and the Gadient- Descent method is applied to optimize the cental paametes and width paametes o the membeship unction and the weight o the neual netwok, so that the elation between the tained vehicle speed, toque and cuent appoaches the assistance chaacteistic cuve[0].finally, the Gavity method is used o deuzziication, to detemine the assisted taget cuent. (2) Baking mode. Duing simultaneous steeing and baking, in ode to ensue the baking peomance, the lateal iction coeicient always deceases, theeby causing the change in steeing moment, easy to weakening the oad eel, making the vehicle at an instable state. Then the nomal steeing assisted taget cuent value I o the EPS contolle is multiplied by a coection coeicient ε, so the taget cuent is I = I ε ( 0 < ε < ), and the assisted moment o the system shall be modeately educed to incease the steeing esponse and the handling stability o vehicle. 3.3 Coodination Contolle The ule-based uzzy contol method was adopted. The coodination contol block diagam is shown in Figue. Fig.. Coodination contol block diagam

5 Reseach on the Coodination Contol o Vehicle EPS and ABS 303 The coodination ules ae shown as ollows: () ABS system: Unde the linea baking condition, ABS contolle contols in the nomal mode; unde the condition o simultaneous steeing and baking, it contols in the steeing mode, and adjusts the expected slip ate λ 0 o the wheel accoding to the changes o vehicle speed, lateal acceleation and longitudinal acceleation in eal time, so that the compehensive peomance can be optimized. a y. g The eeence omula o the expected slip ate[4] is: λ 0 = k. (9) 2 a. u (2) EPS system: unde nomal steeing, EPS contols in the nomal mode; unde the condition o simultaneous steeing and baking, it contols in the baking mode and identiies the vehicle s steeing chaacteistic, based on the deviation e between the actual yaw velocity and the expected yaw velocity and the steeing angle δ o the steeing wheel, and detemines the cuent coection coeicient ε, theeby educing the tend o excess steeing and avoiding the instability o vehicle. u δ The eeence omula o the expected yaw velocity[] is: ω = (0) 2 L ( + K u ) Wheein, K Stability acto o vehicle L Axle base x 4 Simulation and Result Analysis The above systems have been subject to simulation in Matlab, The multibody dynamic equation is pogammed and solved by means o the Diect method in the numeical analysis. The main paametes o one eeence vehicle ae shown as ollows: m=360kg, l =.29 m, l =.252 m, I z =087.8 kg m 2, etc. Simulation conditions: The initial velocity is 40km/h, giving angle step input to the steeing wheel. Ate the vehicle is at a steady cicula state, apply emegency baking until the vehicle stops. The two chaacteistic quantities o yaw velocity and lateal acceleation ae selected to inspect the vehicle maneuveability;and the baking distance is selected to inspect the baking peomance. Fig. 2. Yaw velocity Fig. 3. Lateal acceleation Fig. 4. Baking distance

6 304 W. Qin et al. Figue 2and Figue 3 show the esponse cuve o the vehicle s yaw velocity and lateal acceleation unde coodination contol and sepaate contol (the contolle only contols in the nomal mode)ate the bake is applied. It can be seen that the yaw velocity alls slowly ate the coodination contol is applied, so that the vehicle s steeing capability is enhanced and the luctuation o lateal acceleation is small,so that the vehicle is not easy to have such phenomena as instability and lateal sliding, theeby eectively inceasing the vehicle maneuveability. Figue 4 is the compaison o the baking distance. It can be seen that the baking distance unde the coodination contol is inceased by 0.8m than that unde the sepaate contol; because the vehicle stability is ist guaanteed in contolle design, the baking distance is slightly inceased, but is still within an acceptable scope and then the compehensive peomance o vehicle is impoved. 5 Hadwae-in-the-Loop Test 5. Oveall Design o Test The test equipments include the tail vehicle equipped with EPS and ABS actuatos, NI PXI-896 embedded contolle, 6289 data acquisition cad, teminal box, selmade hadwae-diving cicuit boad, notebook PC, and gyoscope and so on. The test design is: Vehicle is the contol teminal o this system. Host compute (equipped with LabVIEW) caies out pogamming, pogam debugging, and data display. The slave compute (PXI embedded contolle) povides the sotwae unning envionment and it is a eal-time opeation system, which can eceive the vehicle status inomation, then analyze the inomation though the use-deined contol algoithm in the sotwae module and make the coesponding decision, and inally output the contol commands, so as to dive the hadwae cicuit and contol the action o actuatos. The host compute and the slave compute ae connected by netwok though TCP/IP potocol. The oveall layout o test is shown as Figue Sotwae Pogam Design Fig. 5. Test layout diagam The sotwae adopts modula pogamming, mainly include data acquisition and pocessing module, contol and debugging module etc. The LabVIEW pogam totally adopts thee theadings, namely EPS, ABS and coodination section. The thee theadings ae synchonous and associated. The coodination theading communicates with EPS and ABS theadings to coodinate the two subsystems.

7 Reseach on the Coodination Contol o Vehicle EPS and ABS 305 As a multi-theading language, LabVIEW can ealize concuent execution o multiple independent tasks. The synchonization among thee theadings can be ealized by the synchonization technique in LabVIEW language, and the pioity is set though timed loop. The communication among thee theadings is ealized though the queues technique. The queue stuctue is a FIFO stuctue which may be divided into thee steps o obtaining, opeation and elease. The contol stategies o each system unde two contol modes ae pogammed by utilizing the timed loop, CASE stuctue, omula node and uzzy contol toolbox etc. in LabVIEW sotwae. 5.3 Test Results The vehicle test conditions wee that the vehicle was in the steady cicula state at a initial speed o about 40km/h and a lateal acceleation o about 0.3g, and then was applied with emegency bake. Figues 6 and 7 show the eal-time voltage signals o the yaw velocity and lateal acceleation, and the hoizontal axis is the acquisition time. It can be seen om the signal chat, compaed with the sepaate contol, the yaw velocity and the lateal acceleation unde coodination contol all slowly, namely smalle slope o cuve, theeby inceasing the ability o the vehicle to keep steeing tavel,and the luctuation o cuve is smalle, theeby educing the eect o bake on the vehicle maneuveability. (a)sepaate contol {b)coodination contol Fig. 6. Voltage signal o the yaw velocity (a)sepaate contol (b)coodination contol Fig. 7. voltage signal o the lateal acceleation

8 306 W. Qin et al. The baking distance was measued by a photoelectic speed senso. It can be seen om the value o baking distance in Table, as the stability is guaanteed peeentially, the baking distance is inceased slightly, but the compehensive peomance o vehicle is impoved. Table. Baking distance Initial baking speed (km/h) Baking distance(m) Baking time(s) Sepaate contol Coodination contol Conclusion () A hieachical coodination contol eseach on two systems o EPS and ABS o vehicle chassis is caied out, and the multibody model o EPS system is applied. The simulation esults show that, coodination contol eectively impoves the compehensive peomance o vehicle. (2) The hadwae-in-the-loop test povides a new simulation analysis technique to solve vaious poblems in the contol systems o vehicle such as design, test and peomance optimum. The esults o hadwae-in-the-loop test based on LabVIEW veiy the eectiveness o coodination contol stategy in this thesis. (3) This thesis has cetain diective signiicance to multibody dynamics model and hadwae-in- the-loop test used in the eseach and development o electical contol system o vehicle. Reeences. Yu, F., Lin, Y.: Vehicle System Dynamics. China Mechanical Pess, Beijing (2005) 2. Tahei, S.: An investigation and design o slip contol baking systems integated with ou wheel steeing. In: Depatment o Mechanical Engineeing. Clemson Univesity (990) 3. Zhang, L.P.: An Analysis o Vehicle Peomance in Coneing with Baking & Anti-Lock Baking Contol Simulation Reseach. Yanshan Univesity, Qin huangdao (2004) 4. Li, J., Yu, F., Zhang, J.W., et al.: An Investigation into Optimal Taget Slip Ratio Contol o Simulation o an Anti-lock Baking System o Vehicles. Jounal o System Simulation 3(6), (200) 5. Chu, C.B., Chen, W.W., Liu, X.Y., et al.: Vehicle Expeiment o Hadwae-in-the-loop Based on LabVIEW. Jounal o Heei Univesity o Technology 32(), (2009) 6. Luo, Y.G., Yang, D.G., Li, M.H., et al.: Hadwae-in-the-loop Simulation on Dynamical Coodinated Contol Method in Paallel Hybid Electic Vehicle (PHEV). Chinese Jounal o Mechanical Engineeing 44(5), (2008) 7. Paviz, E.: Nikavesh: Compute-Aided analysis o mechanical systems. Pentice-Hall, Englewood Clis (988) 8. Chu, C.B., Chen, W.W.: Vehicle Chassis System Based on Layeed Coodinated Contol. Chinese Jounal o Mechanical Engineeing 44(2), (2008) 9. Bakke, E., Nybog, L., Pacejka, B.: Tye modeling o use in vehicle dynamics studies. SAE pape No.87042, pp (987) 0. Yang, X.J.: Dynamic Analysis and Contol Study o EPS System. Heei Univesity o Technology, Heei (2003)