GB2207782A

GB2207782A - Programmable speed select apparatus for automatic cruise control

Info

Publication number: GB2207782A
Application number: GB08817936A
Authority: GB
Inventors: Charles Franklin Burney
Original assignee: Reeves Brothers Inc
Current assignee: Reeves Brothers Inc
Priority date: 1987-08-07
Filing date: 1988-07-27
Publication date: 1989-02-08
Also published as: GB8817936D0; DE3825376A1; KR890003573A; JPS6485840A; AU1842288A

Description

PROGRAMMABLE SPEED SELECT APPARATUS FOR AUTOMATIC CRUISE CONTROL 21-% r; L

U / v 8 121, The present invention relates to an apparatus for use in an automotive cruise control system. After the device has chosen the desired speed, the invention allows that speed to be stored in a nonvolatile memory and recalled anytime the driver wishes. The desired speed is then used as a setpoint by the automotive cruise control system.

Prior automotive cruise control systems, whether they operate electrically or otherwise, have been of the type which uses the present speed of the automobile at the time the system is activated as a setpoint. This means that the driver must accelerate the vehicle to the desired speed and then engage the cruise control system. The system then operates to maintain that particular speed of the vehicle. This must be done each time the.driver wishes to use the cruise control system after it is deactivated as prior systems have no means for storing a particular setpoint in a memory. Under most conditions, this is an acceptable mode of operation from both the standpoint of safety and convenience. There are times, however, when it would be desirable for a cruise control system to have a setpoint stored in its memory which the driver could then recall anytime that particular speed is desired. For example, there are occasions when the driver may wish to activate the cruise control system,_ but it would be hazardous for him to divert his attention away from the road or other vehicles in order to check the speedometer prior to activating the cruise control. At other times, a driver may wish for the cruise control system to accelerate the vehicle to a predetermined speed simply for reasons of convenience. It would be advantageous, therefore, for a cruise control system to provide a means for storing and recalling a predetermined setpoint. It would be further advantageous if the cruise control system provided a convenient means for changing this predetermined setpoint to whatever value is desired. A still further advantage would be obtained if the cruise control system were able to be operated with the predetermined setpoint or, alternatively, operated in the manner of the systems of the prior art with the current speed of the vehicle taken as a setpoint without disturbing the previously stored predetermined setpoint. It is toward these objects that the present invention is directed.

The invention therefore provides an apparatus for use in conjunction with a vehicular speed control system which provides an electrical signal proportional to the present speed of the vehicle as well as an electrical signal proportional to the setpoint speed of the vehicle wherein the setpoint speed can be selected to be either the present speed of the vehicle or a previously determined past speed of the vehicle, comprising:

a means for converting the present speed of the h 1 vehicle into an electrical signal proportional to the speed; an analog to digital converter means for converting the electrical signal proportional to the speed of the vehicle to digital form; a nonvolatile storing means for storing the digital form of the electrical signal proportional to the speed of the vehicle; and a digital to analog converter means for converting the digital form of the electrical signal proportional to a past speed of the vehicle stored in said storing means into an electrical signal representing the setpoint speed.

The present invention thus discloses an electronic apparatus for use in conjunction with an automotive cruise control system which allows the operator to program a setpoint speed into the system which is permanently stored in the nonvolatile memory. The stored setpoint may be recalled at anytime after programming and the cruise control system will.operate so as to reach and maintain that setpoint speed. Having a programmable setpoint stored in a nonvolatile memory presents a number of advantages over conventional cruise control systems without such capability. When the system is activated and the stored setpoint is recalled, the operator does not have to manually accelerate or decelerate the vehicle as the cruise control system does this itself. The apparatus also contains a second memory independent of the nonvolatile memory which allows the operator to operate the cruise control system in a conventional manner by first accelerating or decelerating the vehicle to the desired speed and then engaging the cruise control system. When the latter mode of operation is utilized, the previously stored setpoint speed is left undisturbed.

The present invention, as represented by the preferred embodiment, accomplishes these objects by using a counter for the nonvolatile memory which is continuously connected to power source such that the state of its latches will remain the same even when power is shut off to the rest of the system. The second memory is also a counter and, in the preferred embodiment, it is nbt connected to the power source so as to be volatile although in an alternative embodiment, it certainly could be. Both counters are part of counting type analog to digital converters which convert a voltage signal proportional to the speed of the vehicle to digital form. A ladder type digital to analog converter is used to output the contents of each counter in analog form for use by the cruise control system. In the preferred embodiment, a transduction means which converts the speed of the vehicle to a D.C. voltage is utilized to both program the counters and provide the cruise control system with a representation of the controlled variable.

A latching circuit which is controllable by manual push buttons is used to select the mode of operation.

The - i 1 outputs of the latching circuit select which memory is to be used by controlling transistor switches. The state of the latching circuit also determines whether the counter is to be programmed or its contents retrieved for use by the cruise control system.

There will now be described an example of apparatus according to the invention. The description, which is intended to be read with reference to the drawing, is given by way of example only and not by way of limitation.

The drawing is an electrical schematic diagram showing the component parts and their interconnections which make up the preferred embodiment of the present invention.

It will be appreciated that some of the functional groups of components could be designed as signal integrated circuit chips or the entire circuit could be a single integrated circuit chip.

Referring to the drawing, switch S3 is the power switch which enables power to flow from battery Bl to the rest of the circuit. The terminals marked with a plus sign are connected via switch S3 with the positive terminal of car battery Bl. The terminals marked with a ground sign are connected to chassis of the automobile as is the negative terminal of battery Bl.

Counters U6 and U5 make up the nonvolatile and volatile memories, respectively, of the apparatus. Both U6 and U5 are series-in, parallelout counters which receive their inputs at the port of each labeled CLOCK.

-6 As each counter receives pulses through the CLOCK input port, a binary number corresponding to the number of pulses received is generated and output through the ports labeled OUT on each register. Each output port can be high or low and represents a single digit of the generated binary number. Each output port is connected to a ladder network of resistors. The resistance of the resistors making up the ladder network form a ladder-type digital-toanalog converter which produces a DC voltage at its output proportional to the binary number at its inputs. The DC output of U5 and U6 are then fed to the collectors of transistors Q2 and Q1, respectively. Both counters U5 and U6 also have power input ports labeled P and reset ports labeled RESET. If either counter receives a pulse at its reset port, that counter will clear the binary number at its output ports to zero.

Magnetic assembly M1 is connected to the drive shaft of the vehicle in such a manner as to be rotated at a rate proportional to the speed of the vehicle. The magnetic field of M1 is coupled to inductor Ll. As the magnetic flux through L1 changes, owing to the rotation of M1, voltage pulses are generated across L1 at a frequency proportional to the speed of the vehicles. These pulses are then input to amplifier Ul. Amplifier U1 has a feedback capacitor connected between its inverting input and output so as to perform as an integrator. Additionally, a feedback resistance is also connected to

C h allow the capacitor to discharge between pulses. Amplifier U1 thus produces at its output a voltage proportional to the frequency of the pulses received at its input. This voltage is labelled V1 and represents the present speed of the vehicle. The voltage V1 is then input to comparator U2 as well as fed to a part of the cruise control system not described here to effect the cruise control function.

Comparator U2 is connected in such a way that when the voltage applied from U1 to its inverting input is higher than the voltage applied to its noninverting input, the output of U2 will be low. If the opposite condition exists, the output of U2 will go high. The output of U2 is connected to the inputs of both gates U4 and U7. Both U4 and U7 are multiple input NOR gates, each of which produces a high output only when all of its inputs are low and a low output otherwise. The outputs of U4 and U7 are then connected to the input ports of counters U5 and U6, respectively.

Amplifier U3 is configured in such a way so as to form a high-frequency oscillator or CLOCK. The pulse train at the output of CLOCK U3 is fed to one of the inputs of both gates U4 and U7.

Gates U9A and U9B are NAND gates which together form latch U9. Each of the two inputs to latch U9 is connected to the positive terminal of the power supply through resistor R9A or R9B and to ground through switch S1 or S2. The operation of switches S1 and S2 is effected by the push buttons labeled SET and MEMORY, respectively. Each of the two outputs of latch U9 is connected to the base of either transistor Q1 or Q2. The operation of the latch is such that when both inputs are high, one of the outputs will be low and the other will be high. Which particular output will be high or low depends on the previous state of the latch. The outputs of latch U9 are connected so that if switch S1 is closed, transistor Q2 will be cut off while transistor Q1 will be turned on. Subsequent opening of switch S1 will not disturb the output state of the latch. Closure of switch S2, on the other hand, saturates transistor Q2 while cutting off transistor Q1. Transistors Q1 and Q2 are connected to the DC outputs of counters U6 and U5, respectively. Additionally, capacitor C4 is connected from resistor R9B to ground. Capacitor C4 acts to ensure that upon an initial power up condition, or when both switches S1 and S2 are closed and then simultaneously opened, the state of latch U9 will be such that transistor Q1 is cut off while transistor Q2 is saturated.

As aforesaid, the DC outputs of counters U5 and U6 are connected to the collectors of transistors Q2 and QI respectively. The collectors of transistors Q2 and Q1 are also connected through diodes D3 and D4, respectively, to resistor R5. and thence to ground. The voltage across R5 is labeled V2 and represents the setpoint or desired speed- of the vehicle. The voltage V2 is used in conjunction with the voltage V1, which is the actual speed of the vehicle, by a part of the control system not described here to regulate the speed of the automobile. The voltage V2 is also fed to the noninverting input of comparator U2 for a purpose described below. Owing to blocking diodes D3 and D4, the voltage V2 will equal whichever DC output of counter US or U6 is higher. That, in turn, will depend upon which if transistors Q1 and Q2 is conducting and which is cut off. If, for example, transistor Q1 is conducting, its collector is shorted to ground. This means that the DC output of counter U6 is dropped to zero across resistor Rl. If transistor 02 is cut off, V2 will then equal the DC output of counter US. If the respective states of transistors 01 and Q2 are reversed, the voltage V2 will equal the DC output of counter U6. Thus, by controlling the states of transistors Q1 and Q2, the state of latch U9 determines which of the DC outputs of counters US or U6 will be chosen to produce voltage V2.

As noted earlier, counters US and U6 make up the volatile and nonvolatile memories, respectively, of the present invention. The power input port of counter US is connected to the power supply through switch S3 as is the rests of the apparatus. When power is shut off, the contents of counter US is not able to be maintained. Upon returning power to the circuit, current flows through capacitor Cl and resistor R3 which produces a reset pulse v at the reset input of counter US which clears the counter. Register U6, on the other hand, receives enough power through resistor R4 to maintain its contents even if a switch S3 is open.

There now follows a description of the operation of the preferred embodiment o the present invention as part of an automotive cruise control system. It is to be assumed that the operator of the automobile simply engages the cruise control system before pushing either the SET or MEMORY buttons. Upon first applying power to the circuit of the drawing, the state of latch U9 causes voltage V2 to be produced by the contents of counter U6, the nonvolatile memory. Therefore, whatever was previously stored in counter U6 will be used by the cruise control system as a setpoint.

Assume now that the operator wishes the cruise control system to operate with a different setpoint but does not wish to disturb the previously stored setpoint speed residing in counter U6. The operator first accelerates or decelerates the vehicle to the new desired speed. The SET button is then pushed which grounds one of the inputs to latch U9. This causes the output line from latch U9 connected to the base of transistor 02 to go low which cuts off transistor Q2. The other output line of latch U9 goes high which saturates transistor Q1. This causes the output of counter US to produce voltage V2 and electrically isolates the output of counter U6 owing to the reverse biasing of diode D3. The high output of latch U9 is also connected via capacitor C2 to the reset input of counter US. As that output goes high, a voltage pulse is produced across resistor R3 which clears the contents of counter US to zero. When the SET button is depressed, one of the four inputs to gate U4 is grounded. Another of the inputs to gate U4 comes from the output of latch U9 which is connected to the base of transistor 02 which is also low. Since the contents of counter US is now zero, V2 is also low. Assuming that the vehicle is travelling at some rate of speed, this means that V1 is greater than V2 which makes the output of comparator U2 low. When the output of CLOCK U3 goes low, all of the inputs of gate U4 are low which makes the output of gate U4 high. Thus, while the SET button is depressed, counter US receives and counts pulses at its input. This continues until V2, the analog output of counter US equals V1, the analog voltage proportional to the speed of the vehicle. The CLOCK frequency is great enough that the SET button must remain depressed for only a second or so before all of this occurs. The end result is the selection of counter US to produce setpoint voltage V2 and the contents of US being equal to the speed of the vehicle at the time the SET button is depressed.

Next, assume that the operator is using the cruise control system as above with the volatile memory of counter US providing the setpoint voltage and wishes to change that setpoint. First, the vehicle is accelerated or decelerated to a new speed. The MEMORY button is then depressed which causes the outputs of latch U9 to change their states such that counter U6 is selected as the operative memory. This causes the output of latch U9 connected to capacitor C2 to go low. After releasing the MEMORY button, the SET button is depressed which causes a voltage pulse through capacitor C2 which resets the contents of counter U5 to zero. The identical events described in the preceding paragraph then occur which cause counter U5 to produce setpoint voltage V2 and its contents to equal to the speed of the vehicle at the time the SET button was depressed.

Finally, assume that the operator wishes to change the contents of counter U6, the nonvolatile memory. First, the vehicle is accelerated or decelerated to the speed desired as the new nonvolatile setpoint. The MEMORY button and the MEMORY-SET buttons are depressed simultaneously. The depression of the MEMORY button, as before, causes the output line of latch U9 connected to the base of transistor QI to go low. This line is also connected to the input of NOR gate U8. The other two inputs to gate U8 are connected to switches S2 and S4, opened and closed by the MEMORY and MEMORY-SET buttons, respectively. Thus, when both the MEMORY and MEMORY-SET buttons are depressed, all three inputs to NOR gate U8 are low, making its output high. This causes a voltage pulse across resistor R3 via capacitor C3 which is input to the 1 reset port of counter U6, clearing its contents to zero. Switch S4 is also connected to the input of gate U7 as are switch S2 and the output line of latch U9 Whi ch goes low when counter U6 is connected. The other inputs to gate U7 are from CLOCK U3 and comparator U2. Thus, in the same manner as the programming of counte r U5, CLOCK pulses are gated to counter U6 through gate U7 until the analog output of counter U6 equals V1. In this way, the nonvolatile setpoint becomes equal to the present speed of the vehicle.

Various modifications may be made within the scope of the invention as defined in the following claims.

Claims

What is claimed is: 1. An apparatus for use in conjunction with a

vehicular speed control system which provides an electrical signal proportional to the present speed of the vehicle as well as an electrical signal proportional to the setpoint speed of the vehicle wherein the setpoint speed can be selected to be either the present speed of the vehicle or a previously determined past speed of the vehicle, comprising: a means for converting the present speed of the vehicle into an electrical signal proportional to the speed; an analog to digital converter means for converting the electrical signal proportional to the speed of the vehicle to digital form; a nonvolatile storing means for storing the digital form of the electrical signal proportional to the speed of the vehicle; and a digital to analog converter means for converting the digital form of the electrical signal proportional to a past speed of the vehicle stored in said storing means into an electrical signal representing the setpoint speed.
2. Apparatus according to Claim 1, wherein there is further provided: a second storing means for storing the digital form of the electrical signal proportional to the present speed of the vehicle; -is- 1 a means for alternatively operatively connecting either said nonvolatile storing means or said second storing means to said analog to digital converter means for storing the digital form of the electrical signal proportional to the present speed of the vehicle; a means for alternately enabling either said nonvolatile storing means or said second storing means to generate an electrical signal proportional to a selected speed and which speed can be used by the vehicular speed control system as a setpoint speed.
3. Apparatus according to Claim 2 wherein said means for alternately operatively connecting either said nonvolatile storing means or said second storing means to said analog to digital converter means further comprises a latch means having manually operable inputs and having outputs which enable or disable gating means which operatively connect each of said nonvolatile storing means and said second storing means to said analog to digital converter means.
4. Apparatus according to Claim 3 wherein said means for alternately enabling either said second storing means or said nonvolatile storing means to generate an electrical signal proportional to a speed to be used by the vehicular speed control system as a setpoint speed also further comprises said latch means and wherein the outputs of said latch means are also operatively connected to a switching means for enabling or disabling the outputs of said storing means for use by the vehicular control system.
5. Apparatus according to Claim 4 wherein there is further provided a means for enabling said nonvolatile storing means to generate the electrical signal proportional to a speed to be used by the vehicular speed control system as a setpoint speed upon the initial activation of the apparatus.
6. Apparatus for use in conjunction with a vehicular speed control system, constructed and arranged substantially as hereinbefore described with reference to and as shown in the drawing.

Published 1988 at The Patent Office. State House. 66 71 High Holborn. London WC1R 4T.D. Purther copies may be obtained from The Patent Office, Sales Branch. St Mary Cray, Orpington. Kent BR5 3RD. Printed by Multiplex techniques ltd. St Mary Cray, Kent. Con. 187