Vehicle speed control system

To decrease the number of switches and their connections to a speed control system, only two manually operated switches are provided to, respectively, allow for "engage", "disable" and "resume" operations, the system further including a bistable circuit which is connected to one of the manually operated switches to provide the manually operated switch with a dual function.

Cross reference to related applications: U.S. Ser. No. 770,585, filed Feb. 
22, 1977, Fleischer U.S. Ser. No. 770,594, filed Feb. 22, 1977, Fleischer 
both assigned to the assignee of the present invention. 
The present invention relates to a vehicle speed control system and more 
particularly to such a system in which a signal is derived representative 
of actual vehicle speed which is compared with a signal entered into a 
memory to store a commanded speed value, and in which a comparison of the 
commanded and actual speeds is used to generate an error signal which 
controls the positioning element. 
Various vehicular speed control systems have been proposed; usually they 
require manually operated switches. One switch is used to connect the 
system, which may be termed a "engage" switch; a further switch is used to 
disconnect the system which may be termed a "disable"; and the third 
switch is used to store a value representative of a commanded, for example 
to set a memory upon simultaneous engagement of the system to store, in 
the memory, the then instantaneous speed. The system is not entirely 
appropriate to operating requirements and comfort; further, difficulties 
arise in locating the necessary switches close to the steering wheel, or 
in combination with a steering post switch, or switches mounted on the 
steering post, or a housing, or cowling therefor. 
It is an object of the present invention to provide a control system having 
a minimum of units or elements having control functions, so that the 
system will be simple, while still permitting comfortable and convenient 
operation of the speed control system, and which is so arranged that it 
can be made to form original equipment of the vehicle, as well as a 
subsequently added accessory. 
SUBJECT MATTER OF THE PRESENT INVENTION 
Briefly, the control unit for the speed control system has only two 
manually operated switches, preferably touch controlled switches, and 
further includes a bistable circuit connected to at least one of the 
switches so that one of the switches, at least, can function as a 
dual-mode operating switch. 
The number of manually operable switches, and thus the requirements for 
space as well as assembly, wiring, and the like can be reduced if at least 
one of the manually operated switches can be used to carry out more than 
one switching function, by alternative, or successive operation of the 
same switch. 
In accordance with a feature of the invention, one of the switches has 
associated therewith the function of setting a memory while simultaneously 
enabling the positioning system; the other switch has the sole function of 
engaging the positioning system, for example to resume a speed already set 
in the memory, as well as to disconnect the positioning system. 
The bistable circuit can be used in the form of a suitable stepping 
circuit, stepping from one position to another; in accordance with a 
feature of the invention, however, the bistable circuit is a T-flip-flop 
having a trigger input connected to the one, or both of the operating 
buttons which have to have a dual function and having another input 
connected to one of the other manually operated switches, unless the 
manually operated switches are both connected to the trigger input. This 
pure electronic arrangement is less subject to malfunction and error, as 
well as being considerably less expensive than a mechanical stepping 
network. 
It is a comparatively simple matter to integrate automatic disconnect 
functions in the system of the present invention. Thus, and in accordance 
with a feature thereof, suitable switching signals can be applied directly 
to an input of the T-flip-flop to disable automatic positioning. Applying 
disconnect signals directly to inputs of the flip-flop which act directly 
on the output has the advantage that these signals can be arranged to 
provide priority of function or operation, that is, overide the manually 
inserted information into the flip-flop. This is important to provide for 
reliability of disengagement of the automatic speed control system if, for 
example, the brake or the clutch of the vehicle is operated, so that the 
positioning system is reliably disconnected and remains disconnected upon 
brake or clutch operation, even if one or the other or both of the 
manually operated switches are operated by the driver. 
It has previously been proposed to disconnect the positioning system by 
interrupting power supply to the final stage. In accordance with a feature 
of the invention, the final stage is disabled by controlling an amplifier 
therefor, preferably through a controlled gate. This decreases costs of 
the system since the power to be switched is substantially less.

Block 10 (FIG. 1), in general includes the portions of the system to 
control the speed of the vehicle and therefore forms the speed command 
section thereof; block 16 is the actual engine control section which forms 
the positioning unit for the throttle of the engine, and block 30 is the 
control unit therefor. FIGS. 2 and 3 illustrate modification of the 
control unit, that is, of block 30, the remainder of the system being 
unchanged. 
The speed command section 10 (FIG. 1) has a tachometer generator 11 the 
output voltage of which is converted in a frequency-voltage converter to a 
dc voltage representative of vehicle speed. This voltage can be stored in 
a memory 14 upon closing of a relay switch contact 13 as a speed command 
value if relay 13 is closed when the vehicle has reached a desired speed. 
The output of the memory 14, forming a command signal, is compared with 
the instantaneous actual vehicle speed signal in a comparator 15 to 
provide an error positioning signal for the engine control section 16. 
The engine control section 16 includes an amplifier 17 in the form of an 
operational amplifier, the output of which is connected through an AND 
gate 18 to the power output stage 19. The output of the power stage 19 
controls a motor 20 which, in turn, is mechanically coupled to the engine 
throttle 21 controlling fuel flow to the engine. The engine throttle is 
coupled to the accelerator pedal of the vehicle. The actual position of 
the engine throttle 21 is sensed by a sensing potentiometer 22 which 
provides a voltage depending on the angle of the throttle position. This 
voltage is applied to the amplifier 17 as an actual throttle position 
signal, so that the engine control section operates as a closed loop servo 
system. 
The control unit 30 has two pushbutton or touch sensitive switches 31, 32, 
and a bistable network 33 constructed as a J-K flip-flop with a trigger 
input. The output of the flip-flop (FF) 33 is connected through an 
inverter 34 to terminal 36 of the control unit and then to an AND gate 18. 
The control unit has a speed set output terminal 35 which is connected to 
the switch 13. 
The T-FF is a JK-FF having "enable" inputs 40, 41 connected to the positive 
terminal of a source of voltage supply, for example a regulated voltage 
derived from the battery of the vehicle. The FF 33 additionally has two 
inputs 42, 43 which directly effect the output of the FF. These are the 
customary SET and RESET terminals 42, 43. The RESET input 43 is controled 
directly from a terminal 44 and then by an OR gate formed by diodes 144, 
244, 344 to have automatically derived disconnect signals applied thereto. 
The terminal 43 is an overide terminal, and enabling terminal 43 overides 
any other input signals. This is desirable because, if the brake of the 
vehicle is operated, or if the clutch is disengaged or the transmission is 
placed in neutral, the positioning system must be immediately disconnected 
so that it does not counteract action of the brake, or interfere with 
transmission changing due to excessive engine speed. The T-FF 33 has an 
additional trigger input 45 which in the example illustrated reacts to 
positive flanks of trigger pulses. 
The embodiment of FIG. 1 illustrates the arrangement in which the manually 
operable switch 31 provides for setting of the memory and simultaneous 
engagement of the positioning system; the manually operable switch 32 has 
a dual function which, alternatively, can effect disabling of the 
positioning system or resumption of automatic control by the positioning 
system. 
Operation: Let it be assumed that the system is not in operation, but that 
the vehicle with which it is associated is being driven along a highway. 
The driver accelerates the vehicle by depressing the accelerator pedal 
which changes the position of engine throttle 21. When the desired speed, 
as indicated by the speedometer has been reached, the driver operates 
switch 31. This operation need only be momentary. This causes response of 
the switch 13 and the voltage representing the then instantaneously 
existing speed will be stored in memory 14 by storing the dc voltage, as 
converted from the tachogenerator 11 by the voltage frequency converter 12 
in the memory circuit 14. Upon operation of switch 31, FF 33 is 
simultaneously SET. The voltage at the output 37 of the FF 33, taken at 
the inverting side, drops to a value near ground, or chassis potential. 
Inverter 34 raises the voltage to a predetermined level, responding to a 
binary ONE signal level, which appears at output 36, and thereby enables 
AND gate 18. Amplifier 19 is thereby enabled to control motor 20 to 
position the engine throttle, as indicated schematically by the broken 
line between motor 20 and throttle 21. The positioning system is in 
operation and will hold the vehicle at a constant speed. 
Operation of switch 32 applies a signal to trigger input terminal 45 which 
changes over the state of FF 33 to RESET state, so that the output 37 will 
have operating potential appear thereat. Due to the action of the inverter 
34, gate 18 is blocked and the positioning system disconnected. Subsequent 
operation of the switch 32, forming a "resume" operation again changes the 
state of FF 33 to SET state, again opening gate 18. Since, however, the 
stored speed command value has not changed, the vehicle will be 
accelerated to the previously commanded speed, or, respectively, no fuel 
will be supplied to permit engine braking to slow the vehicle. 
The switch 32 thus has a dual function; alternatively it enables and 
disables the power stage 19 and hence the positioning motor 20 for 
alternative ON and OFF operation of the positioning system with respect to 
a previously commanded speed. 
If switch 31 is operated while the positioning system is engaged, that is, 
gate 18 is open, no change will be effected by the FF 33; a new speed can 
be commanded, however, by storing a new speed in memory 14. 
If, at any time, during operation of the system the brake is operated, 
diode 144 will be rendered conductive and a signal will be applied to the 
override -- RESET terminal 43 which is directly transfered to the output 
37 of the FF 33. This signal, which is a priority signal, casuses 
immediate disconnection of the positioning portion of the engine control 
section, that is, disconnection of the input to the power stage 19 and 
hence disabling of the motor 20. No operation of any one of the switches 
31, 32 can override the RESET signal on terminal 43. If both terminals 42 
and 43 have a signal applied thereto, the terminal 43 has priority and a 
high, or ONE output will be obtained at terminal 37. 
Application of a signal to any one of the other diodes 244, 344, or further 
similarly connected diodes will, likewise, effect immediate disconnection 
of the power stage and hence of the positioning system. The power stage is 
disabled at its input, so that the switching power required is low. 
Embodiment of FIG. 2: The only difference in this system is the specific 
connection of the control unit 30', which has output terminals 
corresponding to those of control unit 30 and which therefore has been 
given the same numbers and are similarly connected to the remaining 
sections and elements of the system. Operation of switch 31' only enables 
the engine control section by providing a ONE signal at terminal 36, 
thereby enabling gate 18. Memory 14 is set upon operation of the switch 
32', which operates a dual function switch. Insurance must be provided 
that the memory can be set only if, simultaneously, the positioning system 
is in operation. This is obtained by controlling engagement of switch 13 
over an AND gate 50 which is controlled by the switch 32 only if, 
simultaneously, the output 36 has a ONE signal appear thereat. 
Embodiment of FIG. 3: Both momentary operating switches 31" and 32" are 
dual-function switches. The switch 31" alternatively sets the memory 14 
upon simultaneous connection of the positioning system and disabling the 
positioning system. The switch 32 alternatively connects or disconnects 
the positioning system. 
Various change and modifications may be made within the scope of the 
inventive concept.