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					Seoul 2000 FISITA World Automotive Congress                                                                        F2000A105
June 12-15, 2000, Seoul, Korea



      Engine Constant Speed Control in Starting and Shifting Process of
                Automated Mechanical Transmission (AMT)
                                            Anlin Ge* Hui Jin Yulong Lei

                            Jilin University of Technology, 142 People Street Changchun, China

The coordination of engine will influence the starting and shifting quality of AMT. Heretofore, the study on this aspect is
mainly limited to the engine torque control. But for the difficulty of installing torque sensor, just open loop control is
adopted, so that the effects don’t be satisfactory. This paper puts forward the strategy of engine constant speed control in
starting and shifting process, based on the view of kinematics and dynamics. The main idea is that the target speed of
engine is constituted according to the different throttle opening, and the deviation between the target speed and the actual
speed will be limited through clutch control and fuel injection control in starting and shifting process, which not only
greatly reduce the work of slipping and prolong the life of the clutch, but also reduce the fuel consumption and the noise,
improve the shift quality in starting and shifting process.

Keywords: Engine control, Automated Mechanical Transmission, Starting, Shift

                                                                      The expression of j is [2]
INTRODUCTION                                                                                            i g ( n )i0η T dx
                                                                                      j = 2 µ Rc k c                              (1)
                                                                                                          δ M a rr dt
Automated mechanical transmission (AMT) has been
developed due to the electronics progress. The aim of                 where,   µ -- friction coefficient of clutch;
AMT is to make the powertrain automatic. The control                            rr -- effective radius of tire;
system of AMT includes the engine, clutch and gearbox                           i g , i 0 -- ratio of gear box and final drive;
control. Clutch control plays an important role. Because it
directly affects the starting and shifting quality, the studies                  R c -- mean radius of clutch friction plate;
of AMT control mostly focus on the clutch control.
                                                                                 k c -- constant coefficient;
However the engine control is neglected usually. AMT
control is an integrated control system. Because the output                     η T -- transmission efficiency;
speed of engine will affect the difference of speed between
                                                                                δ -- correction coefficient         of rotating mass
driving and driven plates of clutch, it will affect the
                                                                                without engine inertia;
magnitude of the work of slipping. According to analysis
of the starting and shifting process, this paper puts forward                   M a -- total mass of vehicle;
a strategy of engine control. First, we set down a target                       dx
speed based on throttle opening and engine characteristic.                         -- clutch engaging speed.
Then the engine speed is controlled to approach the target                      dt
speed through controlling clutch engagement speed and                 That shows the jerk degree is decided not only by the
controlling fuel injection. Finally, this strategy is carried         vehicle characteristic but mainly by clutch engaging speed,
into execution in a Santana 2000 car successfully.                    so we can get more smooth starting and shifting progress
                                                                                             dx
PERFORMANCE INDEXES                                                   through controlling       rationally.
                                                                                             dt
JERK DEGREE j
                                                                      THE WORK OF SLIPPING Lc
In Jerk degree is the change rate of vehicle’s acceleration.
It can exclude the influence of bump acceleration due to              The   Lc means the work of slipping generated from the
road conditions and really reflect the degree of starting
                                                                      friction between clutch plates. Figure 1 illustrates the
jerk on human body.
                                                                      process of the clutch engagement in starting. From the
                                                                      figure, we can see the Lc can be described as:
 * e-mail: hmti@public.cc.jl.cn




                                                                  1
                                                                                                                                        M a δrr2             ωe

                                                     ωe
                                                                                                                                Lc =
                                                                                                                                       ηT i g ( n ) i0
                                                                                                                                            2        2   ∫   0
                                                                                                                                                                  (ω e − ω c ) dω c
                                                                                                                                                   ωe
                                                                                                                  M a δrr2                 ω c2      M a δ rr2 ω e2
          speed of revolution


                                ω es                                cs                                         =                 (ω eω c −      ) =
                                                                                                                 ηT i g ( n ) i0
                                                                                                                      2        2
                                                                                                                                            2 0     ηT i g ( n ) i0 2
                                                                                                                                                         2        2


                                                                                                                                                                   (5)
                                                          ωc
             (rpm)




                                                                                                        From above equation we can conclude that the work of
                                                                                                        slipping is mainly affected by the engine speed when a
                                                                                                        vehicle runs on a plain and smooth road. So if we can
                         0                t1                   t2           time t(s)                   control the engine speed at a lower and constant value
                                                                                                        (here is called target speed) in starting and shifting process,
                                                                                                        the work of slipping will be reduced greatly and the life of
    Figure 1 - The process of the clutch engagement in                                                  clutch will be prolonged.
                         starting
                            t1                       t2
        Lc = ∫ Tc ω e dt + ∫ Tc (ω e − ω c )dt                                                (2)       ENGINE CONTROL STRATEGY
                          0                          t1

where, Tc -- torque transmitted through clutch;
                                                                                                        Based on above analysis, here we put forward engine
                 ω e -- the speed of the driving plate of clutch,                                       control strategy of starting and shifting process.
                                   equaling to the engine speed;
                  ω c -- the speed of the driven plate of clutch;                                       STARTING STRATEGY                       &            ESTABLISHING
                                                                                                        TARGET SPEED
                  t1 -- the time from the plates touching to the
                 vehicle moving;
                                                                                                        The basic idea of starting control strategy is that, in
                 t 2 -- the time from the vehicle moving to                                             starting process, based on throttle opening ( α ) and engine
                  ω c equaling to ω e .                                                                 steady dynamic characteristic, a lower speed is deduced as
                                                                                                        target speed of the starting process, and the difference
According to vehicle dynamics equation, the torque
                                                                                                        between actual speed and target speed is reduced through
transmitted through clutch ( Tc ) can be described as                                                   controlling the clutch engaging and fuel injection.
following:

                                         [(sin θ + f ) ⋅ g + δ ⋅ a ]
                          M a rr                                                                        Now we take an example of Santana 2000 car to show how
        Tc =                                                                                  (3)       to establish target speed of starting process. Figure 2 (a)
                         ηT i g ( n ) i0
                                                                                                        illustrates the speed characteristic curve of the engine of
where, θ -- gradient of road;
                                                                                                        Santana 2000, the dots denote various speed ( ω e max                   α     )
        f -- coefficient of rolling resistance;
       g -- acceleration of gravity;                                                                    with maximum output torque under different throttle
                                                                                                        opening. For the purpose of making full use of power
                                                                           rr        dω c
           a -- acceleration of vehicle, a =                                              .             advantages, we take the           ω e max        α       as target speed
                                                                         ig ( n ) i0 dt
                                                                                                        ω ed       under various throttle opening, Which is also the
When vehicle runs on a plain road, θ and f are all very                                                        α

small and can be ignored [3], so we can get that:                                                       engine’s minimum steady running speed. Figure 2 (b)
                                                                                                        illustrates the relation between the throttle opening and the
                          M a δrr2            ω es
        Lc =
                         ηT ig ( n ) i0
                             2        2   ∫
                                          0
                                                     (ωe − ωc )dωc                            (4)
                                                                                                        target speed.


where,       ω es -- engine speed when the difference of                                                SHIFTING STRATEGY & ESTABLISHING TARGET
                                                                                                        SPEED
rotational speed between driving and driven plates is zero.

Now we hypothesis that the engine speed is constant in                                                  Due to clutch disengagement, the engine is in no load
starting and shifting process ( ω e = ω es ). From Figure 1,                                            condition. In order to avoid engine speed being sharply
                                                                                                        increased, we will control the engine speed approaching
we can see the region, which has oblique line, stands for
                                                                                                        the target speed to reduce the fluctuation of engine speed
the reduced work of slipping through the engine constant
                                                                                                        and make shifting process smooth.
speed control. We can deduce the expression of Lc as
that:


                                                                                                    2
                                        Figure 2 - The target speed of starting strategy

Now we suppose that before shifting the gear ratio, the                                   T     n
                                                                                                             Kd                        
engine speed and the vehicle speed individually is                    u e = K p  E (k ) +      ∑ E (k ) +      ( E ( k ) − E ( k − 1))
expressed as i ga , ne 0 and Va , the relation among them is:                             Ki   k =0         T                         
                                                                                                                                  10
                 0.377 ∗ r
            Va =            ∗ ne 0                       (6          where,   u e -- control parameter;
                  i ga ∗ i0
                                                                              E (k ) -- deviation between actual speed and target
After shifting the gear ratio, the engine speed and the                       speed;
vehicle speed individually is expressed as i gb , ned and Vb ,                 Kp        Ki       K d --proportional, integral and
the relation among them is:                                                   differential   coefficient        control      parameter
                 0.377 ∗ r
            Vb =            ∗ ned                        7
                                                                              individually;
                  i gb ∗ i0                                                   T -- sampling period.
Due to the fact that shifting time is very short (usually in
                                                                     In order to improve the response speed of engine speed
several seconds), vehicle inertia is great, and we assume
                                                                     control, the proportional coefficient K p ought to be
the vehicle speed is constant in shifting process ( Va = Vb ),
therefore, following formula can be deduced:                         increased, on the other hand it will cause over control and
                                                                     will bring great fluctuation of engine speed. So this paper
          0.377 ∗ r                0.377 ∗ r
   Va =              ∗ ne 0 = Vb =            ∗ ned      8           will adopt PID__Ping-Pang compound control algorithm.
           i ga ∗ i0                i gb ∗ i0
                                                                     Ping-Pang control is established based on performance
                      i gb
              ned =          ∗ ne 0                      9           index     of     the      shortest    control    time
                      i ga
                                                                          = ∫ dt = min(t f , t 0 ) ). The control function can be
                                                                              tf
                                                                     (y
                                                                              t0
ned is the target speed of engine in shifting process.
                                                                     described as:
ENGINE CONTROL                                                                 u i* (t ) = 1         i = 1, 2, 3,                 11
                                                                     It is an on-off control function, so for a N ranks control
In order to keep engine speed constant in starting and               system, if the shortest time control could be carried out, the
shifting process, here a PID controller is designed. Because         times of control action should be n-1 at most, therefore, the
of the time being short in starting and shifting process, the        shortest time control is realized as well as the control
rapid response speed of target speed controller is required.         precision is ensured.
PID control satisfying the requirement of the speed
controller of AMT, it not only has the merits of simple              PID__Ping-Pang compound control algorithm is that
structure and easily adjusted parameters, but can realize
effective control even in the condition where the math
                                                                        PID        control                      when E (k ) < ned
model is not definite. The PID control algorithm of target              Ping − Pang control                     when E (k ) ≥ ned
speed is described as following:
                                                                                                                                  12




                                                                 3
The engine speed will be above or under the target speed             main factor to affect jerk degree and it is also the important
 ned . When E (k ) ≥ ned , through the on-off fuel                   parameter to keep engine constant rotation. In the equation
                                                                                dω e
injection in shifting process, we can reduce or increase             (15), if         = 0 , we can get the following expression:
engine speed rapidly and keep the engine speed constant.                         dt
When     E (k ) ≤ ned , PID control will improve the control                    dx         1       ∂f (α , ω e ) dα
                                                                                    =            ⋅              ⋅              (16)
precision. The switch between PID and Ping-Pang control                         dt 2u c Rc k c         ∂α         dt
is related with the value of ned . If ned is small, the effect       Therefore, in order to keep engine constant speed rotation,
of Ping-Pang control is greater, system response speed will           dx
                                                                         must vary with the change of throttle opening.
be rapid and transition time will be shortened. However, it           dt
will cause a greater fluctuation. Vice versa.

CLUTCH CONTROL STRATEGY
                                                                     TESTING RESULT
THE CLUTCH ENGAGEMENT POSITION CONTROL
                                                                     In order to verify the effect of the control strategy
                                                                     introduced in this paper, tests were performed in a Santana
The relation between engine torque          Te and the torque        2000 car.
transmitted by the clutch    Tc can be described in the form
                                                                     Figure 3 illustrates a shifting process (from 1st gear to 2nd
of the following equation:
                                                                     gear) without constant speed control and Figure 4 illustrates
                                 dω e
              T e − Tc = J e ⋅                           (13)        the same process with constant speed control.
                                  dt
According to previous analysis, when engine speed
ω e equals to target speed ω ed , if we keep ω e constant,
             dω e
which means         is zero, the torque transmitted by the
               dt
clutch Tc should equal to the engine torque Te .
The relation between Tc and clutch displacement x can
be described as:
             Tc = 2u c Rc ( k c x + c c )                (14)
                                                                                   1—actual speed 2—target speed
where,   c c --constant coefficient.                                      Figure 3 - shift process without constant control

Because engine torque   Te is the function of throttle
opening α and the engine speed ω e . We can describe the
relation between them as Te = f (α , ω e ) . So the clutch
engagement position can be calculated by:
                    f (α , ω e ) c c
              x=                −                        (15)
                    2u c Rc k c k c

In order to make up for the control error, when
 E ( k ) ≥ n ed , we can increase the clutch load by                               1—actual speed 2—target speed
                                                                          Figure 4 - shift process without constant control
enlarging the clutch engagement displacement to make the
engine speed approach target speed. Vice versa.

                                                                     From Figure 3 we can see that the engine speed has a
THE CLUTCH ENGAGEMENT SPEED CONTROL                                  manifest fluctuation, that will not only cause the clutch
                                                                     wearing but also decrease the shifting smoothness and
 dx                                                                  generate engine noise. The main reason is as following:
     is the clutch engagement speed, it means to come at
 dt                                                                  1). In selecting and shifting process, the engine speed
the engagement displacement x in a given period. It is the                doesn’t be reduced enough so the transition time is

                                                                 4
      longer;                                                         [3] Ge Anlin, “ Automatic Clutch Control in the System of
2).   While clutch engaging, the time of fuel injection is            Automated Mechanical Transmission”, Proceedings of
      earlier and the cooperation with clutch engagement is           IPC-5, Vol.3, No. 891371, 1989, Beijing
      incoordinate, which cause engine speed fluctuation.
                                                                      [4] K. Kosuge, K.Furuta, T.YOkoyama, “ A Control
Figure 4 illustrates a shifting process with engine constant
                                                                      Architecture for Intelligent Mechanical System: Virtual
speed control, In which throttle opening is 27%. We make
                                                                      Internal Model Following Control”, 1987 IEEE
a target speed of 1500 rotation per minute based on it. We
                                                                      INTERNATIONAL SYMPOSIUM ON INTELLIGENT
adjust the actual speed approaching target speed through
                                                                      CONTROL, Philadelphia, Pennsylvania
cutting off fuel injection when the clutch beginning
disengaging and injecting fuel when the clutch beginning
engaging to make the fuel injection assorted with the
engaging process of the clutch. The result of constant
speed control strategy is showed in Figure 4. The
fluctuation of the engine speed is very small. The shifting
time is only 0.95 second and the time of power interrupting
is shortened, so a good shift quality is achieved.

CONCLUSION

The key conclusions derived from this research are:
1). The engine constant speed control can reduce the work
    of slipping greatly that generated in starting and shifting
    process, thus can prolong the life of clutch;
2). The engine working at such a little higher speed than
   the minimum steady running speed that the noise
   generated in starting and shifting process can been
   reduced significantly, also the fuel consumption is
   reduced;
3). Reducing the difference of rotational speed between
   clutch driving and driven plates makes the process of
   starting and shifting more smooth.
4). The result of the study in this paper is applicable not
   only to AMT but also to AT and CVT.




REFERENCES

[1] Ge Anlin, The Dynamically Synergetic Control in
Automatic Shift Process ,SAE 931965

[2] Lei Yulong, “ Study on Improving the Performance of
Automated Mechanical Transmission”, Ph. D.
Dissertation, JiLin University of Technology, 1999.1



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