Upshift logic

An improved control system and method for an automatic/semi-automatic transmission system (10) including an automatic change gear transmission (12) driven by a throttle (26) controlled engine (14) is provided. The control system includes a processing unit (42) for receiving inputs indicating at least throttle positon (THL) and vehicle speed (OS) and for determining vehicle acceleration (dOS/dt) and for processing these inputs in accordance with a program or logic rules to determine the selected engaged gear ratio and for issuing command signals to a transmission shifting mechanism (34). The processing unit operates according logic rules so that the control system will execute skip upshifts upon sensing certain predetermined conditions.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to vehicular automatic and semi-automatic 
transmission systems providing a plurality of gear reduction ratios, such 
as automatic mechanical transmissions, and to control systems therefor. In 
particular, the present invention relates to control systems and methods 
for vehicles with throttle controlled engines and automatic or 
semi-automatic transmissions wherein gear selection and shift decisions 
are made and executed based upon measured and/or calculated parameters 
such as transmission output shaft or vehicle speed, transmission input 
shaft and/or engine speed, throttle position, calculated engine speed in a 
potentially engagable ratio, and the like. More particularly, the present 
invention relates to automatic/semi-automatic transmission control systems 
of the type described above having at least one mode of operation in which 
upshifting by more than a single ratio step will be commanded if 
conditions indicative of vehicle acceleration sufficient to indicate that 
single upshifting will result in a rapid requirement for further 
upshifting are sensed. 
2. Description of the Prior Art 
The use of automatic transmissions of both the automatic mechanical type 
utilizing positive clutches and of the planetary gear type utilizing 
frictional clutches is well known in the prior art as are control systems 
therefor. Electronic control systems for automatic transmissions wherein 
gear selection and shift decisions are made based upon certain measured 
and/or calculated parameters such as vehicle speed, engine speed, rate of 
change of vehicle speed, rate of change of engine speed, throttle 
position, rate of change of throttle position, full depression of the 
throttle (i.e. "kickdown"), actuation of the braking mechanism, currently 
engaged gear ratio, and the like are known in the prior art. Examples of 
such automatic transmission control systems for vehicles may be seen by 
reference to U.S. Pat. Nos. 4,722,248; 4,569,225; 4,595,986; 4,361,060; 
4,073,203; 4,253,348; 4,038,889; 4,226,295; 3,776,048; 4,028,929; 
4,039,061; 3,974,720 and 3,942,393, the disclosures of all of which hereby 
incorporated by reference. 
Automated transmission systems having a selectable mode wherein skip 
downshifts, if allowable (i.e. engine speed in to be engaged ratio not 
greater than maximum allowable engine speed), assuming substantially 
constant vehicle speed, are selected are known in the prior art as may be 
seen by reference to U.S. Pat. No. 4,576,065, the disclosure of which is 
hereby incorporated by reference. 
While the above referenced automatic transmission control systems, and 
similar systems, are effective to control an automatic transmission by 
selecting a desired gear ratio which will tend to optimize the fuel 
economy and/or performance of the vehicle in view of the sensed parameters 
and then to command a shift into the selected gear ratio, such control 
systems were not totally acceptable as the predetermined programs utilized 
to generate shift decision data, such as a shift pattern or patterns (also 
commonly referred to as a shift point profile) or the like did not 
optimize vehicle performance when vehicle acceleration (usually sensed as 
rotational acceleration of the transmission output shaft) sufficient to 
cause undesirably frequent single upshifting is sensed. If vehicle 
acceleration is such that, if only a single upshift is commanded, an 
additional upshift will be required in less than a reference period of 
time, vehicle performance will be unsatisfactory as the frequent shifting 
will be a nuisance and, in a mechanical transmission, the overly frequent 
torque interruptions during shift transients is inefficient. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, the drawbacks of the prior art 
have been overcome or minimized by providing a control system and method, 
preferably an electronic control system, for automatic transmissions, such 
as automatic/semi-automatic mechanical transmissions, wherein gear 
selection and shift decisions are made and executed based upon measured 
and/or calculated parameters including current input shaft and/or engine 
speed, throttle position, output shaft or vehicle speed and/or the rate of 
change thereof and wherein the predetermined program by which shift 
commands are generated has at least one mode of operation wherein upshifts 
by more than one ratio (i.e. "skip upshifts") will be commanded if 
conditions indicative of rapid vehicle acceleration sufficient to cause 
undesirably rapid repeated single upshifts are sensed. 
The above is accomplished by providing an automatic/semi-automatic 
transmission control system including a central processing unit (CPU) 
generating shift commands based upon sensed or calculated parameters such 
as engine speed, currently engaged gear ratio, output shaft speed, and 
throttle position. The control system will automatically evaluate, 
initiate and complete an upshift through more than a single gear ratio to 
improve vehicle performance when the time required for an upshift from the 
next higher gear ratio, assuming acceleration to equal a value based upon 
existing acceleration, is less than a reference period of time. In this 
mode or modes of operation, upon reaching an engine speed at which an 
upshift is indicated, the control will calculate/sense the rate of vehicle 
acceleration and throttle position, and, if conditions warrant, command 
initiation of an upshift to the Nth (where N is a whole number greater 
than one (1), usually (2) or three (3)) higher ratio if the calculated 
expected engine speed at the end of the reference period of time, assuming 
substantially constant vehicle acceleration, in the next higher ratio 
exceeds the engine speed, assuming constant throttle position, at which an 
upshift is required. 
The control will thus initiate a skip upshift if sufficient vehicle 
acceleration is sensed and, preferably, will not complete the skip upshift 
unless the vehicle is accelerating sufficiently to avoid an immediate 
downshift. 
If a skip upshift is not allowable, a single upshift to the next higher 
ratio will be commanded. 
To avoid skip upshifting during a coasting condition, skip upshifts will 
only be performed if throttle position exceeds a predetermined minimal 
value. 
Accordingly, it is an object of the present invention to provide a new and 
improved control system and method for automatic/semi-automatic 
transmission systems which will sense vehicle operating conditions 
conducive to a skip upshift and which, in such conditions, will select 
allowable skip upshifts. 
This and other objects and advantages of the present invention will become 
apparent from a reading of the description of the preferred embodiment 
taken in connection with the attached drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 schematically illustrates an automatic mechanical transmission 
system 10 including an automatic multi-speed compound change gear 
transmission 12 driven by a fuel controlled engine 14, such as a well 
known diesel engine, through a coupling such as torque converter and/or 
master clutch 16. An engine brake such as an exhaust brake 17 for 
retarding the rotational speed of engine 14 and/or an input shaft brake 18 
which is effective to apply a retarding force to the transmission input 
shaft upon disengagement of master clutch 16 may be provided as is known 
in the prior art. The output of automatic transmission 12 is output shaft 
20 which is adapted for driving connection to an appropriate vehicle 
component such as the differential of a drive axle, a transfer case, or 
the like as is well known in the prior art. 
The above mentioned power train components are acted upon and monitored by 
several devices, each of which will be discussed below. These devices 
include a throttle pedal position or throttle opening monitor assembly 22 
which senses the position of the operator controlled throttle device 24, a 
fuel control device 26 for controlling the amount of fuel to be supplied 
to engine 14, an engine speed sensor 28 which senses the rotational speed 
of the engine, a clutch operator 30 which engages and disengages clutch 16 
and which also supplies information as to the status of the clutch, an 
input brake operator 31, a transmission input shaft speed sensor 32, a 
transmission operator 34 which is effective to shift the transmission 12 
into a selected gear ratio and to provide a signal indicative of the gear 
neutral condition and/or the currently engaged gear ratio, and a 
transmission output shaft speed sensor 36. A vehicle brake monitor 38 
senses actuation of the vehicle brake pedal 40. 
It is understood that clutch 16 could be replaced by a hydromechanical 
device, such as a torque converter, and that such torque converter could 
be equipped with by-pass, lock-up and/or disconnect devices. 
The above mentioned devices supply information to and/or accept commands 
from a central processing unit or control 42. The central processing unit 
42 may include analog and/or digital electronic calculation and logic 
circuitry, the specific configuration and structure of which forms no part 
of the present invention. The central processing unit also receives 
information from a shift control assembly 44 by which the vehicle operator 
may select a reverse (R), neutral (N), or forward drive (D) mode of 
operation of the vehicle. An electrical power source (not shown) and/or a 
source of pressurized fluid (not shown) provides electrical and/or 
pneumatic power to the various sensing, operating and/or processing units. 
A fault indicator or alarm 46 may display the identity of a specific fault 
or simply signal the existence of an unidentified fault. Drive train 
components and controls therefor of the type described above are known in 
the prior art and may be appreciated in greater detail by reference to 
above-mentioned U.S. Pat. Nos. 4,722,248; 4,595,986; 4,569,225; 4,576,065; 
4,445,393; 4,361,060; 3,776,048; 4,038,889 and 4,226,295. 
Sensors 22, 28, 32, 36, 38 and 40 may be of any known type or construction 
for generating analog or digital signals proportional to, or indicative 
of, the parameter monitored thereby. Similarly, operators 17, 18, 26, 30 
and 34 may be of any known electric, pneumatic or electro-pneumatic type 
for executing operations in response to command signals from the central 
processing unit 42 and/or for providing input signals thereto. Fuel 
control 26 will normally supply fuel to engine 14 in accordance with the 
operator setting of throttle pedal 24 but may supply a lessor (fuel 
dipped) or greater (fuel boost) amount of fuel in accordance with commands 
from the central processing unit 42. 
Clutch operator 30 is preferably controlled by the central processing unit 
42 and may engage and/or disengage master clutch 16 as described in 
above-mentioned U.S. Pat. No. 4,081,065. Of course, operator 30 could also 
be an operator for torque converter by-pass, lock-up and/or disconnect 
devices as illustrated in allowable U.S. application Ser. No. 006,303 
filed Jan. 15, 1987, now U.S. Pat. No. 4,784,019 the disclosure of which 
is hereby incorporated by reference. Transmission 12 may include 
synchronizing means, such as an accelerator and/or a brake mechanism as 
described in U.S. Pat. Nos. 3,478,851 and 4,676,115, the disclosures of 
both of which are hereby incorporated by reference. Transmission 12 is 
preferably, but not necessarily of the twin countershaft type as is seen 
in U.S. Pat. Nos. 3,105,395; 4,648,290 or 4,735,109. 
In addition to direct inputs, the central processing unit may be provided 
with circuitry for differentiating the input signals from sensors 28 
and/or 36 to provide a calculated signal indicative of the rate of 
acceleration of the engine and/or vehicle, respectively, means to compare 
the input signals from sensor 32 and 36 to calculate a current engaged 
gear ratio, circuit means to compare the current engaged gear ratio with 
the signal from sensor 36 to provide a calculated engine speed, means to 
sense full throttle, and means to calculate an expected engine speed in a 
given engaged ratio and at a given or sensed output shaft speed. 
The central processing unit is also provided with comparison means for 
comparing sensed or calculated signals to fixed or variable reference 
values. 
In the automatic mechanical transmission system illustrated in FIG. 1, a 
purpose of the central processing unit is to select, in accordance with 
predetermined logic rules and current or stored parameters, the optimum 
gear ratio at which the transmission should be operating and, if 
necessary, to command a gear change, or shift, into the selected optimal 
gear ratio based upon the current and/or stored information. FIG. 3 
illustrates the ratio of the input shaft speed to the output shaft speed 
in a 16-forward speed and 2-reverse drive ratio type of transmission 
typically utilized with heavy duty vehicles and suitable for use in the 
automatic mechanical transmission system 10 illustrated in FIG. 1. 
Although not necessary, it may be seen that the steps or splits between 
forward ratios are approximately twenty percent (20%). 
As indicated above, one of the principle functions of the control unit 42 
of the automated mechanical transmission system is to make decisions as to 
the proper gear ratio that should be selected and engaged in transmission 
12 based upon driver demands and vehicle operating conditions. Ideally, 
transmission system 10 utilizes an electronic control unit 42 preferably 
microprocessor based, which can be programmed to enhance specific vehicle 
characteristics. 
One method by which shift decisions are made is for the central processing 
unit program or logic rules to generate shift patterns, or shift point 
profiles, as seen in FIG. 2. The shift point profiles generated by the 
central processing unit will determine if the transmission should remain 
in the currently engaged gear ratio, should be upshifted to at least the 
next highest gear ratio or should be downshifted to at least the next 
lower gear ratio. The shift point profiles are determined by a 
predetermined program acting upon current or stored information and are 
usually selected to provide a compromise between operation at the most 
fuel efficient possible gear ratio and operation in a gear ratio providing 
optimal performance characteristics of the vehicle. Shift point profiles 
illustrated in FIG. 2 are a function of throttle position, expressed as a 
percentage of maximum throttling position, and of engine speed. The engine 
speed may be directly sensed or, preferably, is a calculated engine speed 
(i.e. based upon output shaft speed and engaged gear ratio) which will not 
vary during a shift transient as is known in the prior art. 
As used herein a "higher gear ratio" or "higher drive ratio" will refer to 
a gear or drive ratio having a lower ratio of input shaft speed to output 
shaft speed. For example, tenth (10th) gear is higher than ninth (9th) 
gear and the shift from ninth gear to tenth gear is an upshift. Similarly, 
a shift directly from eighth gear to tenth gear is a skip upshift wherein 
one ratio (i.e. 9th speed) is skipped. A shift directly to tenth speed 
from seventh speed is a skip upshift wherein two ratio steps are skipped. 
The control 42 may have a singular operating mode or may have two or more 
modes including an over-the-highway mode and an off-highway mode either of 
which may be selected by the operator. The skip upshift logic of the 
present invention may be utilized in all or just selected modes of 
operation. The shift point profile illustrated in FIG. 2 are based upon 
transmission control system having both an on-highway and off-the-road 
mode of operation. 
Both the on-highway (A-B-C-D and X-Y-Z) and off-road (E-F-G and U-V-W) 
shift profiles provide the basis for shifting the transmission 12 as a 
function of speed modulated by the driver controlled throttle position. 
Both sets of profiles are primarily derived the characteristics of the 
engine including the effects of all engine driven auxiliaries. The engine 
speed (ES) signal, shown in terms of engine RPM, is preferably derived by 
multiplying the transmission output shaft signal by the numeric value of 
the gear ratio (GR) of the drive ratio currently selected by the control 
electronics. Throttle position (THL) is shown as a percentage of full 
throttle from zero percent (0%) to one hundred percent (100%). 
The shift profiles include an on-highway upshift line A-B-C-D and an 
on-highway downshift line X-Y-Z. Briefly, for operating conditions within 
the space bounded by downshift line X-Y-Z and upshift line A-B-C-D, no 
gear change is required, for operating conditions at or to the right of 
upshift line A-B-C-D an upshift to at least the next highest gear ratio is 
required and for operating conditions within the area at or to the left of 
downshift line X-Y-Z, a downshift to at least the next lowest gear ratio 
is required. It is understood, of course, that a single shift point 
profile may be utilized for all gear ratios of a transmission or a 
separate shift profile may be generated for each currently engaged gear 
ratio. Generally, the greater the difference in ratio splits between the 
gears, the greater the desirability of separate shift point profiles for 
each currently engaged gear ratio. 
Other sensed or calculated monitored speeds, such as input shaft speed, 
output shaft speed, vehicle speed or the like may be substituted for 
engine speed in the shift point profiles illustrated in FIG. 2. Also, 
upshift and downshift lines are preferably not static but are dynamic. 
Dynamically moving shift point profile lines are known, and are discussed 
in greater detail in above-mentioned U.S. Pat. No. 4,361,060. Typically, 
the shift point lines are moved in response to current and/or stored 
information such as direction of a last shift, acceleration of the 
vehicle, acceleration of the engine, rate of change of throttle position, 
operation of the vehicle brake or the like. 
It is important to understand that the shift point profiles are dependent 
upon the throttle position as well as the engine speed. Other than 
selecting a reverse, neutral or a forward drive mode of operation of the 
vehicle by manipulation of selector 44, the operator's only input to the 
transmission is his manipulation of the throttle pedal or other fuel 
control as the case may be. Accordingly, by setting shift profiles and 
modifying same in partial response to throttle position, the operator's 
desires are accounted for at a central processing unit 42 in deciding the 
optimal gear ratio at which the transmission 12 is to operate. 
The shift point profiles also include an upshift limit (UL) at which the 
transmission must be upshifted to prevent impending speed related damage 
to the engine and a downshift enable limit (DE) above which the 
transmission must not be downshifted to prevent speed related damage to 
the engine. The upshift limit (UL) and downshift enable (DE) are not 
functions of throttle position. Line MAX indicates the engine speed in 
which engine damage is expected. Referring to the on-highway mode, 
upshifts occur as the operating point moves to the right of the A-B-C-D or 
UL profiles. Downshifts occur if the operating point moves to the left of 
the DE and the X-Y-Z profiles. All of these profiles, shown in the normal 
position, are subject to movement and response to various signals as 
discussed in greater detail in above-mentioned U.S. Pat. No. 4,361,060. 
With a step change transmission, the ratio of engine speeds between any two 
gears is fixed by the ratio step or split (ratio of gear ratios). With 
profiles located as previously described, each upshift would lead to an 
operating point located on or near the downshift lines for the next high 
gear and vice versa. Hunting between gears would be inevitable. Some 
additional separation between the upshift and downshift profiles is 
desirable and acceptable; however, sufficient separation to eliminate 
hunting can result in an undesirable reduction in fuel economy. To 
overcome this problem, the control moves the shift profiles as a 
consequence of a shift. For a limited period of time after an upshift, the 
downshift profile is moved towards lower engine speeds. For a limited 
period of time after a downshift, the upshift profiles are moved towards 
higher engine speeds. 
Preferably, as indicated above, the engine speed is a calculated rather 
than an actual engine speed, corresponding to the engine speed at drive 
train lock up conditions, which is determined by multiplying the output 
shaft speed by the appropriate gear ratio. The use of a calculated rather 
than an actual engine speed is preferred as actual engine speeds will vary 
during shift transients and the like. 
While operation of the transmission in accordance with the above procedure 
is satisfactory for most normal on-highway conditions, in road conditions 
wherein a grade must be descended by a vehicle and/or the vehicle is 
relatively lightly loaded, the vehicle performance in the above-described 
operation is often unsatisfactory. Under such conditions, a shift logic 
which upshifts by a single step only and/or which is based upon assumed 
constant vehicle speed may not provide acceptable operation as rapid 
repeated upshifts may be required which tend to be objectionable, the 
ratio of time in gear to time out of gear is lower than desired and/or the 
allowable ratio providing maximum acceleration may not be selected. 
To overcome this drawback (in at least the selectable performance modes of 
operation) the improved control system of the present invention operates 
on a program or procedure by which an upshift of N (N equalling a whole 
number greater than one, preferably two or three) steps is commanded when 
conditions indicating that a single upshift will result in an undesirably 
rapid requirement for a further upshift due to vehicle acceleration is 
sensed. 
Conditions conducive for skip upshifting exist if, when an upshift is 
indicated and the throttle setting (THL) exceeds a reference value 
(REF.sub.THL), assuming vehicle acceleration remains at a value determined 
by sensed vehicle acceleration, the calculated engine speed in the next 
higher gear ratio (GR+1) at the end of a reference period of time 
(REF.sub.T) exceeds the engine speeds at which upshifts are commanded from 
the next higher ratio, assuming substantially constant throttle position. 
In such situations, a shift to the Nth higher gear, N equalling two or 
three, is commanded. 
The value of the reference throttle value (REF.sub.THL) is relatively low 
as requiring THL to exceed REF.sub.THL is intended to prevent skip 
upshifting in coasting downhill conditions. The assumed vehicle 
acceleration is a function of, preferably equality, the sensed vehicle 
acceleration and may be sensed by the value of dOS/dt. The reference 
period of time (REF.sub.T) is selected in view of vehicle parameters, the 
rapidity of shifting perceived as undesirable and/or the maximum efficient 
ratio of out of gear-to-in gear time. The value of REF.sub.T may vary with 
vehicle speed, throttle setting (THL) and/or engaged gear ratio (GR). 
Preferably, just prior to completion of the upshift to the Nth higher gear 
ratio, that is prior to actual engagement of the Nth higher gear ratio, 
the central processing unit will again evaluate the expected engine speed 
at the then current vehicle speed and command completion of the initiated 
skip upshift only if calculated expected engine speed is not less than the 
engine speed at which downshifts are commanded from the Nth higher ratio 
at current throttle position. 
Symbolic illustration of the present invention, in flow chart format, may 
be seen by reference to FIG. 4. Starting at point S, the skip upshift 
logic subroutine 100 determines at 102 if an upshift is required, and, if 
not, the subroutine is exited at 104. Alternatively, the subroutine can be 
entered only upon a logic determination that a upshift is required. 
At 106 it is determined if THL is greater than the reference value 
REF.sub.THL, and, preferably, if the brakes are not applied. If either of 
these conditions are not true, a single upshift is commanded at 108. If 
THL is greater than the REF.sub.THL value, and the brakes are not applied, 
at 110 the value of vehicle acceleration, or a representative value such 
and dOS/dt is calculated. 
At 112, the reference time period (REF.sub.T) is determined and an expected 
engine speed in the next higher gear ratio (GR+1) at time equals REF.sub.T 
; ES.sub.E /GR+1; is calculated based upon a calculated vehicle 
acceleration [(dv/dt).sub.C ] which is a function of sensed vehicle 
acceleration dv/dt. 
At 114, the engine speed at which upshifts are commanded from the next 
higher ratio at substantially constant throttle position 
ES.sub.UP/GR+1/THL is determined. 
At 116, ES.sub.E/GR+1 is compared to ES.sub.UP/GR+1/THL. If expected engine 
speed does not exceed the upshift engine speed, a single upshift is 
commanded and the subroutine exited. If expected engine speed does exceed 
the upshift engine speed, a skip upshift to GR+N is commanded at 118. The 
subroutine is then exited. 
Alternatively, as a logic loop such as loop 100 requires only about fifty 
(50) milliseconds to complete, a loop which would continue to test for 
acceptable conditions in a progressively higher ratio, until unacceptable 
conditions were found, could be utilized. Upon finding unacceptable 
conditions, assuming the estimated acceleration, the logic would command a 
shift directly into the highest acceptable ratio assuming the estimated 
vehicle acceleration. 
Although the present invention has been set forth with a certain degree of 
particularity, it is understood that various modifications are possible 
without departing from the spirit and scope of the invention as 
hereinafter claimed.