Abstract:
A voice warning system for an automobile vehicle provided with an automatic speed control device, by which the driver is informed of the vehicle speed, in voice form, when operating a set switch for controlling the vehicle with the device. The volume level of the voice form signal is determined in accordance with a volume setting of a radio in the vehicle. The voice warning system comprises a vehicle speed sensor, a component for generating a signal representative of the volume of the radio, an interface, a voice synthesizing system, and an electronic volume control for the synthesized message, in addition to the automatic speed control device and a set switch therefor.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to a voice warning system for an automotive vehicle provided with an automatic speed control device, and more particularly to a voice warning system which informs the driver of the vehicle speed, in voice form, when the vehicle is set to travel at a desired set speed under control of the automatic speed control device. 
     2. Description of the Prior Art 
     There has been used an automotive vehicle in which an automatic speed control device (hereinafter referred to as simply ASCD) is provided to keep the vehicle speed automatically at a desired set speed within a vehicle speed range of for example 60 to 100 km/h. 
     With the ASCD, the driver can set the vehicle to travel at a desired vehicle speed by operating a switch provided on top of a lever mounted on the steering column, whenever the car is traveling at a speed from 60 to 100 km/h, and the vehicle will then travel at the set speed without the driver operating the accelerator pedal. 
     In such devices, however, the driver must look at the speedometer in order to know the speed at which the vehicle is actually traveling, and it may sometimes be troublesome for the driver to check the speed on the speedometer. 
     BRIEF SUMMARY OF THE INVENTION 
     With these problems in mind, therefore, it is the primary object of the present invention to provide a voice warning system for an automotive vehicle provided with an automatic speed control device, by which the driver is informed of the vehicle speed, in voice form, after having set the vehicle to travel at a constant speed under control of the automatic speed control device. 
     To achieve the above object, the voice warning system of the present invention comprises a vehicle speed sensor, an interface, and a voice synthesizing system including a memory unit, a voice synthesizer, and a control unit, in addition to an automatic speed control device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features and advantage of the voice warning system of the present invention will be more clearly appreciated from the following description taken in conjunction with the accompanying drawings in which like reference numerals designate corresponding elements, and in which: 
     FIG. 1 is a schematic block diagram of an embodiment of the present invention; 
     FIG. 2 is a schematic block diagram of assistance in explaining the theory of operation of a voice synthesizer using a linear prediction coding system (LPC), and 
     FIG. 3 is an example flowchart of a program used with the embodiment of FIG. 1. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference is now made to the figures, and more specifically to FIG. 1, wherein a preferred embodiment of the present invention is illustrated. 
     In FIG. 1, the numeral 1 denotes an interface including a waveform shaper, a multiplexer and so on, to which are input various signals such as a vehicle speed signal S p  with a frequency corresponding to the vehicle speed detected by a speed sensor 20, an on/off signal S s  from a set switch 21 provided for the ASCD, an on/off signal R from a repeat switch 22, and a sound volume signal S VR  indicating a sound volume value as set by a volume control 4 (variable resistor) provided in a car radio 7. In this case, the car radio 7 comprises a tuner 2, a preamplifier 3, a volume control 4, an amplifier 5, and a speaker 6. 
     The vehicle speed signal S p  is shaped to a rectangular pulse signal through the waveform shaper in the interface 1, and other signals S s , R, and S VR  are also converted to digital signals through the waveform shaper so as to be suitable for input to a microcomputer provided in a control unit 9 of the voice synthesizing system 8 explained below. 
     The numeral 8 denotes a voice synthesizing system of a linear prediction coding (LPC) type including three LSI units: a memory unit (ROM) 10, a voice synthesizer unit 11 (oscillators, filters, and D-A converters), and a control unit (microcomputer) 9. This control unit 9 is a microcomputer comprising a CPU for controlling all the operations, a memory (ROM) for storing programs and fixed data, a memory (RAM) for storing input/output data, a clock oscillator and so on, by which the above-mentioned signals input through the interface 1 are processed in accordance with a program explained later, and various voiced messages are synthesized to inform the driver of the vehicle speed, using time sharing. 
     As is well known in the art, a voice synthesizer based on a LPC system has recently been put on the market at a reasonable price by Texas Instruments Incorporated of the USA. FIG. 2 shows schematically the principle of this voice synthesizer. 
     In this synthesizer, pseudo-random noise signals generated from a first sound source oscillator (white noise generator) 14 are selected by a switch 16 in the case of voiceless sounds; periodic impulse signals generated from a second source oscillator (impulse generator) 15 are selected by the switch 16 in the case of voiced sounds. After being amplified by an amplifier 17, the noise and pulse signals are formed into a voice sound by a grid-type filter 18 where the resonance characteristics of a human vocal tract (vocal organs such as tongue and lips located above the vocal chords) in speaking are modeled, and are output as a synthesized voice signal after conversion to an analog signal through a D-A converter 19. 
     The different values of constants such as the pitch of the periodic impulse signal, the difference between voiced sound and voiceless sound, the amplification ratio of the amplifier 17, and the filter constant of the grid-type filter 18, and so on are stored in the memory unit (ROM) 10 of FIG. 1. 
     The synthesizer 11 comprises various circuits which correspond to the first sound source oscillator 14, second sound source oscillator 15, switch 16, amplifier 17, grid-type filter 18, and D-A converter 19 so that the synthesized voice sound signal V s  necessary for the warning message can be output after being controlled according to the output signal selected by the control unit 9. 
     Thus, the necessary synthesized voice signal V s  is output from the voice synthesizer 11, according to the vehicle speed detected by the speed sensor, under control of the signal from the control unit 9. The signal V s  is next adjusted by an electronic volume control 12 of a voltage control type, amplified by an amplifier 13, and output through the speaker 6 of the car radio 7. 
     Further, in this case, the microcomputer in the control unit 9 determines the voice volume according to a car-radio sound volume as adjusted by driver preference (determined by the signal S VR  from the variable resistor 4 of the car radio 7) and outputs a voice volume control signal C v  to the electronic volume control 12 through the interface 1. 
     FIG. 3 shows an example of a flowchart used with the microcomputer in the control unit 9. 
     In this flowchart, first the program determines whether or not the ASCD set switch is on (block 1). If off, the system stands by; if on, the program proceeds. It is possible to design the microcomputer so as to execute another program for controlling processes other than for the present invention while the set switch is off. 
     When the set switch is on, the multiplexer in the interface 1 reads a vehicle speed signal S p  through the speed sensor (block 2) and counts pulses of the signal with a frequency corresponding to the vehicle speed for a given period of time, so that information pertaining to the vehicle speed for the ASCD is obtained. 
     Next, in accordance with the vehicle speed information, a voice form message is determined such as, for example, &#34;Set speed is now 70 km per hour&#34; (block 3). 
     This voice output is temporarily stored in the RAM of the microcomputer (block 4). A sound volume value as set by the volume control 4 in the car radio 7 is taken as a signal S VR  to determine the voice volume depending on driver preference (block 5), and the electronic volume control 12 is adjusted by the signal C v  sent from the interface 1 (block 9). 
     Next, the memory unit 10 and the voice synthesizer 11 are controlled in accordance with the voice output stored temporarily in the RAM of the microcomputer; synthesized voice signals V s  are produced and output through the electronic volume control 12, the amplifier 13 and the speaker 6 to inform the driver of the vehicle speed (block 6). 
     Next, the program checks whether the repeat switch is operable, that is, whether a particular interval (e.g. two minutes) has elapsed. Unless the repeat switch is turned on within this period, the program ends (block 7). If the repeat switch is turned on within this period, the program repeats the steps beginning from block 2 again to repeat the message to the driver in voice form. This repeat switch is useful when the driver fails to hear the voice information. 
     In addition, in this embodiment, although an LPC type voice synthesizing system has been explained as the device for outputting a voice message concerning the vehicle speed for the ASCD, it is possible to use a synthesizer of another type such as a voice reproducing device using a magnetic recording medium, as will be understood by practitioners in the art. 
     As described above, according to the present invention, since vehicle speed obtained from the speed sensor is indicated to the driver the voice form when the driver turns on the set switch for an automatic speed control device, the driver can know the accurate vehicle speed, even when the speed changes abruptly, without looking at the speedometer. 
     It will be understood by those skilled in the art that the foregoing description is in terms of preferred embodiments of the present invention wherein various changes and modifications may be made without departing from the spirit and scope of the invention, which is to be defined by the appended claims.