374 IEEE/ASME TRANSACTIONS ON MECHATRONICS, VOL. 19, NO. 1, FEBRUARY 2014 Uninterrupted Shift and Its Shift Characteristics Kegang Zhao, Yanwei Liu, Xiangdong Huang, Rongshan Yang, and Jianjun Wei

Abstract—A novel transmission concept, the uninterrupted shift but suffers from bad shift quality due to the shift torque in- transmission (UST), is introduced in this paper, which retains most terruption [4], [5]. DCT concept could be predigested as the of the components common or similar to normal automated trans- combination of two AMTs working in turns [6]. Thus, DCT has missions such as automated or dual clutch transmission, but offers an uninterrupted torque from engine to two alternating power routes from the engine to wheels, making wheels during the shifting process with the so-called multimode it possible to achieve no or shorter torque interruption during controllable shifters. An UST dynamic model is established to ana- gearshifts [6], [7]. lyze UST’s shift characteristics. The special control logic involving In a long time, AT has been the dominator in the world for the engine, clutch and transmission are put forward to improve its smooth shift quality, and AMT has gained some ground in UST’s shift quality, and are applied in the simulation model us- ing MATLAB/Simulink tools. To validate the simulation model the market of commercial vehicles for its low cost and high and the control logic, a proto test bench has been designed and efficiency. In recent years, DCT functioning as a no torque built with corresponding data acquisition system and controlling interrupt type of AMT has started to be applied in compact and equipment. Finally UST’s torque uninterrupted functionality dur- midsize cars in Europe primarily and then in Asia. ing shift, effectiveness of the proposed control logic and validity of AT and DCT can achieve smooth drivability without or with the proposed dynamic model have all been verified experimentally. shorter torque interruption during gearshifts, which is real- Index Terms—Control logic, one-way clutch, shift quality, unin- ized mainly by clutchÐclutch overlapping control [8]Ð[10]. The terrupted shift transmission. smooth clutchÐclutch overlapping control needs the proper and accurate control processes, otherwise it will cause undesirable I. INTRODUCTION torque interruption or oscillations [11], [12]. So the higher con- HE transmission is a speed ratio switching device between trol precision makes the real cost significantly increased, and T engine and wheels. The manual transmission (MT) is the the abrasion of clutches would lower the shift reliability. most efficient transmission available, with 97% efficiency over If a transmission could embody the merits of AMT, DCT, and a representative drive cycle [1]. Its main weakness is requiring AT without their demerits, it would be a tempting option for much attention and work of the driver for shifts for operat- both passenger and commercial vehicles. ing the clutch on each shift. The The UST (uninterrupted shift transmission) [13], [14] seems operates shifts automatically with the choices of deter- a potential one, which retains most of the components common mined by a transmission control unit (TCU) to maximize fuel or similar to AMT/DCT for low cost, and could achieve com- economy, drivability and shift quality, as well as reduce en- parable shift quality with AT/DCT for its uninterrupted shift gine emission [2]. Automatic transmissions in the market today characteristics. One of its distinct breakthroughs is to realize mainly include planetary-automatic transmission (AT), auto- ON/OFF control gearshift instead of clutchÐclutch overlapping mated manual transmission (AMT) and dual clutch transmission control gearshift as in AT and DCT. (DCT). With planetary train, wet clutches and , This paper is organized as follows. In Section II, the UST AT is relatively complicated, expensive and less efficient [3]. concept and its key component’s working characteristics are in- AMT is easy to manufacture and as highly efficient as MT, troduced, and its gearshift principle is also explained. In Section III, the modeling of UST driveline is presented, which is to be Manuscript received July 16, 2011; revised November 11, 2011, June 29, used to study control logic and shift characteristics. In Section 2012, and September 20, 2012; accepted November 4, 2012. Date of publica- IV, the UST shift process is analyzed and the control logic of tion January 30, 2013; date of current version January 17, 2014. Recommended engine, clutch and transmission is proposed. In Section V, based by Technical Editor J. Wang. This work was supported by the National Natural Science Foundation of China under Grant 50805049. on the MATLAB/Simulink software platform, the simulation K. Zhao and Y. Liu are with the Guangdong Key Laboratory of Vehicle En- model is built and shift processes are simulated to evaluate the gineering, South China University of Technology, Guangzhou 510640, China. control logic developed. In Section VI, the validation experi- (e-mail: [email protected]; [email protected]). X. Huang (corresponding author) is with the Guangdong Key Laboratory mental bench is described and experimental results are shown of Vehicle Engineering, South China University of Technology, Guangzhou and analyzed. Conclusions that synthesize the results of this 510640, China, and also with the Automotive Engineering Institute, Guangzhou paper are reported in Section VII. Automobile Group Company, Ltd., Guangzhou 510640, China (e-mail: [email protected]). R. Yang and J. Wei are with the Automotive Engineering Institute, Guangzhou II. UST CONCEPT Automobile Group Company, Ltd., Guangzhou 510640, China (e-mail: yangrs@ gaei.cn; [email protected]). A. Uninterrupted Shift Transmission Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. The structural layout of uninterrupted shift transmission Digital Object Identifier 10.1109/TMECH.2012.2235183 (UST) could be similar to that of AMT or DCT. In the

1083-4435 © 2013 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications standards/publications/rights/index.html for more information. ZHAO et al.: UNINTERRUPTED SHIFT TRANSMISSION AND ITS SHIFT CHARACTERISTICS 375

Fig. 1. Schematic layout of a four-speed AMT-like UST.

Fig. 3. Roller-type controllable one-way clutch. (a) Structure of COWC. (b) COWC in the enabled mode. (c) COWC in the disabled mode.

ωo i which is the relative rotate speed of the outer race and the Fig. 2. SpringÐdamper model of an OWC. inner race, and is given as t AMT-like UST for example, the conventional frictional clutch, Toc = nk ωo i dt + ncωo i (1) 0 parallel shafts, gearsets, etc. are retained, but synchronizers of the forward gears are replaced by the so-called multimode con- where n is the number of wedging components, k is the spring trollable shifters (MCSs), as a four-speed UST schematically constant, and c is the damper coefficient. shown in Fig. 1. Engine torque transmitted by the clutch flows The controllable OWC (COWC) is the OWC that can be alternatively into the MCSs that are connected correspondingly controlled to work in two modes: the enabled mode and the to the driving gear of the forward gear pairs. disabled mode. When enabled, COWC functions as a normal The shift of reverse gear is realized by a synchronizer in OWC, which wedges in one direction and freewheels in the this case. And the shifts between forward gears are realized by other direction. When disabled, it freewheels in both directions. MCSs, while the torque intervention assistance is performed COWCs also exist in various types. A roller-type COWC is through engine and clutch control by the control unit. shown in Fig. 3, with (a) showing its components, (b) showing its enabled mode, and (c) showing its disabled mode. It consists of an outer race, an inner race, several rollers, a control ring and B. Multimode Controllable Shifter a group of claws. The control ring is operated by a fork, just In fact, the multimode controllable shifter (MCS) is a special like the synchronizer in AMT. Axial movement of the control type of bidirectionally controllable one-way clutch (COWC), or ring determines the relative location of the rollers and claws to the combination of two normal COWCs in opposite directions. realize the enabled or disabled mode. Concretely, in the enabled OWCs are applied widely to selectively transmit power from mode, the rollers are not restricted by the claws and run into the one race to the other race [15]Ð[17]. According to the relative narrow location shown in Fig. 3(b), so that the COWC functions rotating direction of the inner race and the outer race, OWC has as a normal OWC. In the disabled mode, the rollers are restricted two states of operation: the wedged state and the freewheel state. in the wide location shown in Fig. 3(c) by the claws, so that the OWC transmits torque in one direction of the relative rotation COWC freewheels in both directions. of one race to the other in the wedged state. When the relative The COWC operation is shown in Fig. 4. The real line in- rotation direction of the two races reverses, OWC is released dicates the enabled mode, and the broken line indicates the from the wedged state and runs into the freewheel state. OWCs disabled mode. The spindle of control ring penetrates guide slot exist in various types, such as roller-type, sprag-type and ratchet- in claw and guide slot in inner race, so the axial movement of the type [17], with all types having an inner race and an outer race, control ring changes the relative location of claw and inner race. and the same functions. The relative rotation between the claw and inner race changes In the wedged state, OWC can be modeled as a springÐdamper location of rollers, as shown in Fig. 3(a) and (b), thus the COWC system, as Fig. 2 shows. Its output torque Toc is the function of mode switches. 376 IEEE/ASME TRANSACTIONS ON MECHATRONICS, VOL. 19, NO. 1, FEBRUARY 2014

Fig. 4. Schematic of the COWC operation.

TABLE I EQUIVALENT MODES OF MCS AND COWCS

Fig. 5. Simplified two-speed UST and its shift process. (a) Power flow in first gear. (b) Power flow in shifting process. (c) Power flow in second gear. As said, an MCS functions as the combination of the two COWCs in the opposite directions, can transmit torque or free- wheel in one or both directions, and can be controlled to work As shown in Fig. 5(a), when the transmission is at first gear, in the followings four operation modes: the disabled C2 freewheels, while the enabled C1 wedges. Power Mode 1 (M1): one-way clutch in one direction; flows from the input shaft to C1, then the first gearset and then Mode 2 (M2): one-way clutch in the other direction; the output shaft. As for the disabled C2, it is idly freewheeling Mode 3 (M3): freewheel in both directions; with its inner race speed higher than its outer race’s. When up- Mode 4 (M4): engaged in both directions (locked). shift is required, C2 is enabled to work. C2 wedges immediately The four modes of MCS are equivalent to the mode com- to synchronize its outer race with the inner one and to transmit binations of two COWCs, as shown in Table I, where COWC power. Meanwhile, because of the aforementioned specific re- (A) and COWC (B) stands for the two COWCs in the opposite lationship, C1 automatically turns to freewheel with its outer directions. race speed higher than the inner race’s, even without any actual The shift between gears in the UST is realized through mode mode-change of C1. In this way, engine torque has been handed changes of MCSs, and the key difference from AT and DCT is over from the first gearset to the second gearset in no time, as the ON/OFF controlled mode-change of MCS, which is much shown in Fig. 5(b), i.e., upshift has been accomplished with no easier to realize and costs less compared with clutchÐclutch power flow interruption. Fig. 5(c) shows the power route of the overlapping control [18], [19]. second gear. The downshift process is almost the inversed upshift one in C. Shift Principle this case, just to disable C2 is enough. By this kind of ON/OFF control, uninterrupted upshift and downshift can be thus reliably In the driving state, the MCSs can be further simplified as performed. Of course, the four-mode MCS offers also other COWCs in the positive direction, and each COWC is controlled functionalities necessary for vehicle application, such as engine to switch between enabled mode and disabled mode. Let us take brake, runaway prevention, etc. an upshift process as an example to explain the shift principle The mode-change or shift operations between first and second of UST in detail. gears, or low and high gears, are shown in Table II, in which S Fig. 5 shows a simplified two-speed transmission with two stands for MCS, M stands for mode of MCS. COWCs (C1, C2) in the positive direction. The driving gears Z1 and Z2 are connected with the outer races of COWCs; and the D. Engineering Case input shaft is connected with the inner races separately. Since the driven gears (Z1,Z2) rotate at the same speed, the rotating Fig. 6 shows the 3-D layout of a two-speed UST engineered speed of the first driving gear Z1 is always higher than that of with both positive and negative COWCs. It is especially suitable the second driving gear Z2. Please keep in mind this specific to replace the double clutch and actuator assembly in a DCT relationship. to form the DCT-like UST, with the two nested output shafts ZHAO et al.: UNINTERRUPTED SHIFT TRANSMISSION AND ITS SHIFT CHARACTERISTICS 377

TABLE II TABLE III SHIFT OPERATION SEQUENCE (FIRST AND SECOND GEARS) RANGES AND INTERVALS FOR ENGINE TESTS

Fig. 7. Engine torque map. Fig. 6. 3-D layout of a two-speed UST with both positive and negative COWCs. connecting odd gearsets and even gearsets, respectively. The relative speed relationship between the two gear pairs in Fig. 6 varies by turns with the switch between the odd gearsets and even gearsets [20]Ð[22]. In Fig. 6, COWCs (A) are in the positive direction, and COWCs (B) are in the negative direction. Each COWC is con- trolled by a fork. The fork-set of first COWC (A) and second COWC (B) are actuated by the fork shaft (A), and the fork-set of first COWC (A) and second COWC (B) are actuated by the fork Fig. 8. UST-based driveline dynamic model. shaft (B). Since the synchronizers of the odd and even gears are pre-selectively engaged, the ON/OFF control on the two fork engine works frequently under dynamic conditions, so the dy- shafts can certainly realize torque uninterrupted gearshifts. namic engine torque Te is given as

Te = Tes − λω˙ e . (3) III. SYSTEM MODELING Here, λ is the torque correcting coefficient. In order to study the shift characteristics of the novel UST, an engine math model and a UST-based driveline dynamic model B. Driveline Dynamic Model are set up. In the following, the models are described concisely. The driveline dynamic model is shown in Fig. 8. The ma- A. Engine Model jor submodels include clutch model, MCS models and vehicle model. Engine torque model is given as Dynamic differential equations during the shift (first and sec-

Tes = f(α, ωe ) (2) ond gear) process are

dωe where α is the throttle opening and ωe is the engine speed. Te − Tcf = Je (4) The model is built based on the engine test results. The tests dt are carried out according to the ranges and intervals listed in dωc T − (T + T )=J (5) Table III. c 13f 24f c dt Engine torque map representing (2) is shown in Fig. 7, which dω T − T = J o (6) is obtained through bench tests under steady conditions. Since o f v dt 378 IEEE/ASME TRANSACTIONS ON MECHATRONICS, VOL. 19, NO. 1, FEBRUARY 2014

C A clutch control could be an effective way [20]Ð[23]. It is needless T = r Gf + D v2 (7) f 21.15 to disengage the clutch during the gearshift, but is possible to limit the instant torque fluctuation by controlling the torque v = rωo (8) transmitting capacities of the frictional clutch, so as to buffer μc Fn Rc ωe − ωc =0 the sudden change of engine speed and torque in the manner of Tc = dω (9) transforming the system inertial energy into friction work, and T − J e ω − ω =0 e e dt e c attenuate the impact on the engine and the vehicle.

T13(ωc ,ω13,N13) Supposing environment conditions and vehicle speed are un- ⎧ changed at the shift moment, the change of clutch transmitted − ≥ ⎪ T13f i1 ,ωc ω13 0 torque ΔT in the 1Ð2 gear shift process can be deducted as ⎪ ,N=1 c ⎪ 0,ω− ω < 0 13 ⎪ c 13 dω dω i − i ⎨ ΔT = T − J e − i i J W 1 2 T i ,ω− ω ≤ 0 c e e R 1 c = 13f 1 c 13 (10) dt dt i2 ⎪ ,N13 =2 ⎪ 0,ωc − ω13 > 0 ⎪ − − dωW ⎪ 0,N=3 iR (i1 i2 ) Jc . (13) ⎩⎪ 13 dt T13f i1 ,N13 =4 According to (13), the value of torque change at the shift point can be predicted, consequently, the torque capacity of the T24(ωc ,ω24,N24) clutch can be controlled in advance to reduce or eliminate torque ⎧ − ≥ ⎪ T24f i2 ,ωc ω24 0 ⎪ ,N=1 sudden change in UST driveline system. ⎪ − 24 ⎪ 0,ωc ω24 < 0 Being different from the power recovery in AMT gearshift ⎨⎪ T24f i2 ,ωc − ω24 ≤ 0 or the torque switch in AT or DCT gearshift, the slip-friction = ,N=2 (11) ⎪ − 24 process of the clutch in UST gearshift is for dissipating inertial ⎪ 0,ωc ω24 > 0 ⎪ energy of the multi moment-of-inertia system. And this process ⎪ 0,N24 =3 ⎩ finishes when the engine speed is synchronized with speed of T24f i2 ,N24 =4 the clutch’s driven plate. In slipping process, the clutch is in To =[T13(ωc ,ω13,N13)+T24(ωc ,ω24,N24)] iR (12) the dynamic friction state, and the clutch and vehicle torque is mainly determined by the clutch compressing force Fn accord- where Te is the engine dynamic torque, Tf is the equivalent ing to (9). When engine and clutch speeds are synchronized, drag torque, Je is the moment of inertia of engine and clutch the clutch goes into the static friction state, where the vehicle driving plate, Jc is the moment of inertia of clutch driven plate torque is mainly determined by the engine torque. So there will and transmission input shaft, Jv is the moment of inertia of be a torque gap when the clutch slip finishes if the clutch com- transmission output shaft and converted vehicle mass, ωe is the pressing force Fn holds unchanged in the slipping process. The engine speed, ωc is the clutch driven plate speed, ω13 is the first torque gap Tg is given as follows:

(third) driving gear speed, ω24 is the second (fourth) driving gear dω speed, T is the resistant torque on engine, T is the clutch output T = μ F R − T − (J + J ) e . (14) cf c g c n c e e c dt torque, T13f and T24f are the resistant torques to the clutch, T13 is the first (third) gear output torque, T24 is the second (fourth) This torque gap means sudden change of vehicle acceleration gear output torque, To is the output torque to drive the vehicle, or strong jerk, thus lowering the shift quality. The clutch torque N13 is the state parameter for MCS1 or MCS3, N24 is the state capacity control should be done correspondingly to erase the parameter for MCS2 or MCS4, i1 and i3 are the first and third torque gap at the slip ending moment. Once the clutch slip ends speed ratio (defined as the ratio of input speed to output one, and the whole shift process is completed, the clutch should be similarly hereinafter), i2 and i4 are the second and fourth speed immediately resumed to full engagement, ensuring full torque ratio respectively, iR is the final drive reduction ratio, μc is the capacity. clutch friction coefficient, Fn is the clutch compressing force, Evaluating shift quality generally includes two aspects: in- Rc is the clutch friction radius, r is the effective wheel radius, fluence on the vehicle and influence on the passengers. Usually G is the vehicle weight, f is the rolling coefficient, CD is the the parameter for evaluating the shift quality is vehicle jerk, air drag coefficient, A is the frontal area, and v is the vehicle which is used to indicate the shift comfort and clutch slip fric- velocity. tional work; the latter is used to evaluate clutch abrasion and life-span [24], [25]. The better shift quality means lower jerk and shorter slipping IV. ANALYSIS AND DESIGN OF CONTROL LOGIC time. For reducing the torque shocks, the clutch control logic has UST’s up and down shifts are realized by ON/OFF control of been analyzed previously. In the following, the engine control the MCSs, but the sudden change of speed ratio would cause the logic is to be discussed. engine speed to vary sharply, which may lead to serious torque The shift process of AMT could be considered as a torque impact on the driveline and result in passengers’ discomfort. interrupt and recovery process, and the shift processes of AT and For reducing the torque shocks at shift point, engine torque DCT could be considered as the torque handover processes. And control is ineffective due to its relatively slow response, while in all these shift processes, the precise control of engine speed ZHAO et al.: UNINTERRUPTED SHIFT TRANSMISSION AND ITS SHIFT CHARACTERISTICS 379

TABLE IV PARAMETER VALUES OF THE SEDAN

Fig. 9. Upshift control logic. is essential. Engine control is not essential for UST to realize torque uninterrupted shift, but is still important for shortening the clutch slipping process. Fig. 10. Control logic of throttle opening and clutch torque capacity. Once the clutch begins to slip, the engine throttle opening α should be rapidly decreased, close to the idle state, for assisting the synchronization of the engine and the clutch. And the throttle Compared with traditional test methods, the self-acting op- opening α should be resumed instantly to its original value timization algorithm could accelerate the parameter obtaining when the clutch slip finishes. If α resumed too early, the slip process and cut down test cost. time would be extended, causing additional clutch abrasion and efficiency loss, if resumed too late, the vehicle speed would V. S IMULATION RESULTS be dragged down by the engine, causing the recoil jerk and performance deterioration. Based on the engine model, the UST driveline dynamic The upshift control flow chart is shown in Fig. 9, where v12 model, and the control logic, a UST driveline simulation model st nd is the vehicle speed for the 1 to 2 gear upshift, F12 is the is built using MATLAB/Simulink tools. The vehicle parameters target compressing force on clutch in the upshift. Since the used in the model are from a domestic sedan, and the values are upshift and downshift control flow are similar, only the upshift listed in Table IV. is shown here. Since the upshift characteristics in the accelerating state are In fact, the shift quality is influenced by many factors that similar to the downshift ones in the decelerating state, only the always interact with each other in the shift process, while ve- upshift process is discussed in this paper. hicle environment varies continuously. Therefore it is difficult The shift processes of first gear up to second gear and second to control shift quality through real-time online analysis and gear up to third gear are simulated. Fig. 10 shows the con- prediction. The method for shift quality optimization in real ve- trol strategy of throttle opening and clutch torque capacity, and hicles is to lookup data tables in which parameters are obtained Fig. 11 shows the simulation results as time histories. in simulation, bench, and on-road tests. As analyzed previously, The vehicle runs at first gear initially, the shift order sends the UST shift quality is primarily influenced by the starting and out at 3.75 s, and activates the clutch control. Once the clutch ending time of throttle opening recovery, and the optimal values begins to slip, the engine throttle opening is restricted to lower for the simulation are obtained automatically by using genetic the clutch slip friction work. It has been seen in Fig. 11(a) algorithm to solve a multi-dimensional extreme value problem, that the vehicle torque (on wheels) has been handed over to with the extremum P given in (15) [26]: the second gear with neither interruption nor concussion, as the ⎫ clutch torque capacity decreases the vehicle torque reduces. At ts 2 ⎬ about 4.3 s, the engine resumes to the former lever. At about g = 0 J dt g w (15) 4.4 s, the slip finishes and the clutch resumes to full engagement. P = q + q ⎭ 1 max(g) 2 max(w) The whole shift process lasts less than 1 s. The similar process is obtained for second to third gearshift. where J is the vehicle jerk, ts is the shift time, w is the slip fric- The simulation results reveal that by using the proposed clutch tion work, q1 and q2 are the weighting coefficients of evaluating and engine control logic, this UST could achieve a good shift indices, and max(g) and max(w) are the maximum allowable quality with uninterrupted and smooth vehicle torque and speed values. variation, moderate jerks, and brief clutch slipping process. 380 IEEE/ASME TRANSACTIONS ON MECHATRONICS, VOL. 19, NO. 1, FEBRUARY 2014

and driven side of the bench is about half of the real sedan, so that the torque shocks and the friction slip of the real sedan in the same working conditions will be smaller and shorter, compared with the bench test results. Photos of the experimental bench are shown in Fig. 13, and the main parameters of the bench are shown in Table V. The data acquisition system is implemented using an AD- VANTECH IPC610 industrial personal computer (IPC) with a PCI-1612 4-port communication card and a PCI-1710 multi- channel sampling card.

B. Experiment Results To validate the proposed clutch control logic in shift process, four shift tests have been carried out: the uncontrolled clutch test, the clutch torque intervention test at shift point, the clutch torque intervention test in shift process, and the motor and clutch synergetic control test in shift process. The uncontrolled clutch test is carried out with the clutch fully engaged during the whole shift process, the results are shown in Fig. 14. It can be seen that the UST has realized torque uninterrupted shift. However, as analyzed earlier, the sudden switch of speed ratio causes the sharp and succedent shocks of the output torque. The clutch torque intervention test at shift point is carried out with the clutch torque capacity controlled in advance of the shift. The used clutch torque capacity control logic is shown in Fig. 15, the torque curves are shown in Fig. 16(a) and speed curves are shown in Fig. 16(b). Compared with Fig. 14(a), the torques in Fig. 16(a) keep uninterrupted and become smoother at the shift point. As shown in Fig. 16(b), when the speed ratio switches, the clutch begins to slip to synchronize the motor and the clutch speed. However, when the clutch slip finishes, the output torque shocks still exist due to the torque gap. However, it is obvious that there are still some vibrations of motor torque after shifting in Fig. 16(b). Since the control scheme for COWC is ON/OFF control architecture, this type Fig. 11. Simulation results. (a) Torque of engine and vehicle. (b) Speed of engine, clutch, and vehicle. (c) Vehicle jerk. (d) Slip friction work. of controllers may lead to residual vibrations. The equivalent inertia of the test bench is a mass flywheel in fact, since its inertia is much greater than the inertia before the clutch, just VI. EXPERIMENTAL VERIFICATIONS like in the real vehicle, it functions as a damper of the driveline in some way, so the vibrations of output torque after shifting do A. Experimental Bench not show as obviously as motor torque in Fig. 16(b). An experimental bench is set up, with which UST’s shift The clutch torque intervention test in shift process is carried characteristics and the proposed clutch control logic tests are out with the clutch torque capacity controlled in advance of the performed. Fig. 12 shows the schematic sketch of the bench that shift and in the subsequent clutch slipping process, as shown consists of an ac motor, its inverter, an electrically controlled in Fig. 17, and Fig. 18(a) shows that the output torque keeps clutch, its programmable power supply, a two-speed simplified smooth not only at the shift point, but also in the whole shift UST proto and an equivalent inertia disk. The ac motor taking process. It is obvious that the UST has obtained uninterrupted a role of automotive engine is controlled by the inverter. The and smooth output torque with the help of adequate control. electrically controlled clutch imitating an automotive dry clutch To evaluate the experimental results quantitatively, the an- is controlled by the programmable power supply. Two torque gular jerk, which is the derivative of angular acceleration with measuring sensors are installed on the clutch input shaft and the respect to time, is calculated. The curves of angular jerk of transmission output shaft, and one photoelectric speed sensor is aforementioned three tests are shown in Fig. 19, and their peak installed on the clutch output shaft. The equivalent inertia disk values and variations are listed in Table VI. It is clear that, with is used to reproduce the typical vehicle mass. It must be pointed the clutch controlled in advance of the shift and continually in out that the proportion of the inertia between the clutch driving the clutch slipping process, the peak value of the angular jerk is ZHAO et al.: UNINTERRUPTED SHIFT TRANSMISSION AND ITS SHIFT CHARACTERISTICS 381

Fig. 12. Sketch of the experimental bench.

Fig. 15. Control logic of clutch torque intervention at shift point.

Fig. 13. Photos of the experimental bench.

Fig. 14. Experiment results of clutch torque intervention at shift point. (a) Motor and output torques. (b) Motor, clutch, and output speeds.

TABLE V PARAMETER VALUES OF THE EXPERIMENTAL BENCH

Fig. 16. Experiment results of clutch torque intervention at shift point. (a) Motor and output torques. (b) Motor, clutch, and output speeds.

the synergetic control logic of motor driving torque and clutch 9.44 rad/s3 , having 93.3% reduction compared with the clutch torque capacity shown in Fig. 20. The experiment results are uncontrolled state and 86.7% reduction compared with the state shown in Fig. 21. The output torque shown in Fig. 21(a) keeps of torque intervention at shift point. continuous and smooth over the whole shift process. What is To further shorten the slipping process, motor control is added more as shown in Fig. 21(b), the slipping process is shortened on the basis of clutch torque intervention in shift process, with to about 0.4 s with the slip friction work calculated as 1.8 kJ. 382 IEEE/ASME TRANSACTIONS ON MECHATRONICS, VOL. 19, NO. 1, FEBRUARY 2014

Fig. 17. Control logic of clutch torque intervention in shift process. Fig. 20. Motor driving torque and clutch torque capacity control logic.

Fig. 21. Experiment results of motor and clutch synergetic control. (a) Motor Fig. 18. Experiment results of clutch torque intervention in shift process. driving torque and clutch torque capacity. (b) Motor, clutch, and output speeds. (a) Motor and output torques. (b) Motor, clutch, and output speeds. VII. CONCLUSION The aforementioned analyses, discussions, and experiment validations on the UST can be summed up as follows. 1) UST is capable of realizing torque uninterrupted gearshift with the ON/OFF feature. 2) The torque shocks or jerks during UST’s torque uninter- rupted gearshift can be remarkably attenuated by clutch torque intervention in shift process. The clutch slipping process can also be remarkably shortened by assistant torque control of the driving source. The proposed UST Fig. 19. Angular jerks of the three tests. control logic is valid for improving shift quality. 3) The models presented in this paper can be used to perform TABLE VI effective analyses of the UST shift characteristics. ANGULAR JERK PEAK VALUES As a novel mechatronic transmission, the UST is with good potentiality to inherit comprehensively the merits of AMT, DCT, and AT but not their demerits, and is worthy of further research and development.

REFERENCES Compared with the slipping process without motor control [1] M. Kluger and D. Long, “An overview of current automatic, manual and shown in Fig. 18(b), the slipping time has been shortened for continuously variable transmission efficiencies and their projected future improvements,” SAE Tech. Paper 1999-01-1259, 1999. about 0.5 s, and the slip friction work has been reduced for about [2] G. Wagner, “Application of transmission systems for different driveline 0.8 kJ. configurations in passenger cars,” SAE Tech. Paper 2001-01-0882, 2001. ZHAO et al.: UNINTERRUPTED SHIFT TRANSMISSION AND ITS SHIFT CHARACTERISTICS 383

[3] Z. Sun and K. V. Hebbale, “Challenges and opportunities in automotive Kegang Zhao received the B.S. degree in automotive transmission control,” in Proc. Amer. Control Conf., Portland, OR, Jun. engineering and the Ph.D. degree in vehicle engineer- 8Ð10, 2005, pp. 3284Ð3289. ing from the South China University of Technology, [4] M. Yamasaki, H. Konno, H. Kuroiwa, and N. Ozaki, “Automated manual Guangzhou, China, in 1999 and 2005, respectively. transmission with torque assist mechanism for reducing shift shock,” SAE Since 2005, he has been with the School of Me- Tech. Paper 2005-01-1021, 2005. chanical and Automotive Engineering, South China [5] L. Glielmo, L. Iannelli, V. Vacca, and F. Vasca, “Gearshift control for au- University of Technology, where he is currently an tomated manual transmission,” IEEE/ASME Trans. Mechatronics, vol. 11, Associate Professor of vehicle engineering. His cur- no. 1, pp. 17Ð26, Feb. 2006. rent research interests include the design and con- [6] B. Matthes, “Dual clutch transmissions-lessons learned and future poten- trol of advanced transmission and hybrid electric tial,” SAE Tech. Paper: 2005-01-1021, 2005. vehicles. [7] J. Kim and S. B Choi, “Design and modeling of a clutch actuator sys- tem with self-energizing mechanism,” IEEE/ASME Trans. Mechatronnics, vol. 16, no. 5, pp. 953Ð966, Oct. 2011. [8] B. Z. Gao, H. Chen, K. Sanada, and Y. Hu, “Design of clutch-slip Yanwei Liu received the B.S. degree from Jilin Uni- controller for automatic transmission using backstepping,” IEEE/ASME versity, Changchun, China, in 2003, and the Ph.D. Trans. Mechatronnics, vol. 16, no. 3, pp. 498Ð508, Jun. 2011. degree from the South China University of Technol- [9] J. E. Marano, S. P. Moorman, M. D. Whitton, and R. L. Williams, “Clutch ogy, Guangzhou, China, in 2012, both in vehicle en- to clutch transmission control strategy,” SAE Tech. Paper 2007-01-1313, gineering. 2007. He is currently an Analyst with the Research In- [10] S. Bai, R. L. Moses, T. Schanz, and M. J. Gorman, “Development of a stitute Dept. of Ping An Securities Company Ltd., new clutch-to-clutch shift control technology,” SAE Tech. Paper 2002- Shenzhen, China. His research interests include ve- 01-1252, 2002. hicle powertrain control and vehicle stability control. [11] Y.Zhang, X. Chen, X. Zhang, H. Jiang, and W.Tobler, “Dynamic modeling and simulation of a dual-clutch automated lay-shaft transmission,” ASME J. Mech. Des., vol. 127, no. 2, pp. 302Ð307, Mar. 2005. [12] X. Y. Song and Z. X. Sun, “Pressure-based clutch control for automo- tive transmissions using a sliding-mode controller,” IEEE/ASME Trans. Mechatronnics, vol. 17, no. 3, pp. 534Ð546, Jun. 2012. Xiangdong Huang received the B.S. degree in [13] X. D. Huang, K. G. Zhao, Y. W. Liu, Y. T. Luo, H. Huang, and Z. R. Yuan, mechanical engineering from Wuhan University, “An original automated mechanism transmission with no torque interrupt,” Wuhan, China, in 1982, and the Ph.D. degree in auto- China Patent 201010158023.7, Apr. 27, 2010. motive engineering from Turin Polytechnic Univer- [14] K. G. Zhao, X. D. Huang, and Y. W. Liu, “Automatic transmission,” China sity, Turin, Italy. Patent 201210024895.3, Feb. 6, 2012. He is currently the Vice President of the [15] J. M. Kremer and P. Altidis, “Roller one-way clutch system resonance,” Guangzhou Automobile Group, and also the Presi- SAE Tech. Paper 981093, 1998. dent of GAC Engineering. He is also a Professor and [16] W. Xue and R. Pyle, “Optimal design of roller one way cutch for starter Doctoral Mentor with the South China University of drives,” SAE Tech. Paper 2004-01-1151, 2004. Technology, Guangzhou, China. [17] G. M. Roach and L. L. Howell, “Evaluation and comparison of alternative His current research interests include aerodynam- compliant overrunning clutch designs,” J. Mech. Des., vol. 124, no. 9, ics, body engineering, suspension, chassis, transmissions, vehicle integration, pp. 485Ð491, 2002. and new energy vehicles. [18] A. Grancharova and T. A. Johansen, “Design and comparison of explicit model predictive controllers for an electropneumatic clutch actuator using on/off valves,” IEEE/ASME Trans. Mechatronnics, vol. 16, no. 4, pp. 665Ð 673, Jun. 2011. Rongshan Yang [19] H. Langjord and T. A. Johansen, “Dual-mode switched control of an elec- received the B.S. degree from Jilin tropneumatic clutch actuator,” IEEE/ASME Trans. Mechatronnics, vol. 15, University, Changchun, Jilin, China, in 2001, and no. 6, pp. 969Ð981, Jun. 2011. the Ph.D. degree from the South China University [20] M. Kulkarni, T. Shim, and Y. Zhang, “Shift dynamics and control of dual of Technology, Guangzhou, China, in 2009, both in clutch transmissions,” Mech. Mach. Theory, vol. 42, no. 2, pp. 168Ð182, vehicle engineering. 2007. He is currently with the Automotive Engineering [21] A. C. Van Der Heijden, A. F. A. Serrarens, M. K. Camlibel, and Institute, Guangzhou Automobile Group Company, H. Nijmeijer, “Hybrid optimal control of dry clutch engagement,” Int. Ltd., Guangzhou, China, where he is in charge of J. Control, vol. 80, no. 11, pp. 1717Ð1728, 2007. CAE in vehicle development, including vehicle dy- [22] Y. G. Liu, D. T. Qin, H. Jiang, C. Liu, and Y. Zhang, “Clutch torque namics, crash, and durability analysis. formulation and calibration for dry dual clutch transmissions,” Mech. Mach. Theory, vol. 46, no. 2, pp. 218Ð227, Feb. 2011. [23] S. E. Moon, M. S. Kim, H. Yeo, H. S. Kim, S. H. Hwang, H. L. Song, and K. S. Han, “Design and implementation of clutch-by-wire system for automated manual transmissions,” Int. J. Veh. Des., vol. 36, no. 1, Jianjun Wei received the B.S. degree from the Dalian pp. 83Ð100, 2004. University of Technology, Dalian, China, in 2004, and [24] Q. Huang and H. Y. Wang, “Fundamental study of jerk: evaluation of shift the M.S. degree from the South China University of quality and ride comfort,” SAE Tech. Paper 2004-01-2065, 2004. Technology, Guangzhou, China, in 2007, both in ve- [25] F. Vasca, L. Iannelli, A. Senatore, and G. Reale, “Torque transmissibility hicle engineering. assessment for automotive dry-clutch engagement,” IEEE/ASME Trans. He is currently an Engineer with the Guangzhou Mechatronnics, vol. 16, no. 3, pp. 564Ð573, Jun. 2011. Automobile Group Company, Ltd., Guangzhou, [26] W. B. Yang, G. Q. Wu, and D. T. Qing, “Driveline system modeling and China. shift characteristic of dual clutch transmission powertrain,” Chin. J. Mech. Eng., vol. 43, no. 7, pp. 188Ð194, Jul. 2007. 本文献由“学霸图书馆-文献云下载”收集自网络，仅供学习交流使用。

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