OPTIMAL CONTROL SYSTEM FOR AN ELECTRIC MOTOR DRIVEN VEHICLE

• US 3,630,304 A
• Filed: 11/28/1969
• Issued: 12/28/1971
• Est. Priority Date: 11/28/1969
• Status: Expired due to Term

• Current Assignee: Yilmaz E. Sahinkaya
• Original Assignee: Yilmaz E. Sahinkaya
• Inventors: Sahinkaya, Yilmaz E.
• Application Number:
  US04/880,831
• Time in Patent Office: 760 Days
• US Class Current: 180/179
• CPC Class Codes: B60L 15/2009 for braking
• CPC Class Codes: B60L 7/12 for vehicles propelled by dc motors
• CPC Class Codes: H02P 7/2913 whereby the speed is regulated by measuring the motor speed and comparing it with a given physical value
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility
• CPC Class Codes: Y10S 388/915 Sawtooth or ramp waveform generator

Abstract

Operating conditions experienced by a battery-operated vehicle driven by one or more permanent magnet or separately excited DC motors are sensed and converted into a control signal. The control signal is applied to a pulse width modulator which controls the conduction periods of SCR'"'"''"'"'s in such a way that the average motor armature voltage is proportional to the control signal. In a motoring mode the pulse width modulator operates SCR'"'"''"'"'s to supply current from the battery to the motor armature circuit. This mode usually occurs when the vehicle is moving uphill or accelerating on a level terrain. In a generating mode the pulse width modulator operates SCR'"'"''"'"'s to supply current from the motor armature circuit to the battery. This occurs when the vehicle is moving downhill or is decelerating on a level terrain. The required mode of operation is accomplished automatically by the action of a motor armature current direction sensing circuit.

Claims

1. In a vehicle driven over terrain by an electrical motor which receives power from a battery under control of a throttle, the improvement comprising:

means for establishing a throttle voltage in response to the setting of the throttle representative of the desired vehicle speed, tachometer means driven by said electrical motor for generating a tachometer voltage representative of the actual speed of said vehicle, slope sensing means for establishing a terrain voltage representative of the terrain slope, means to which said throttle, tachometer and terrain voltages are applied for establishing a control voltage representative of the control effect required to attain the speed specified by said throttle setting, means for comparing said control voltage with said tachometer voltage for establishing a motor drive signal when said control voltage exceeds said tachometer voltage and for producing a regenerative sigNal when said tachometer voltage exceeds said control voltage, means enabled responsive to said motor drive signal for applying current from said battery to said electric motor in an amount determined by said control signal, and means enabled responsive to said regenerative signal for applying charging voltage from said electric motor to said battery in an amount determined by said control signal.

2. In a vehicle as recited in claim 1 wherein said means for establishing a control voltage comprises means for comparing said throttle and tachometer voltages to derive a difference voltage representing the difference thereof and to establish an acceleration signal when said throttle voltage exceeds said tachometer voltage and a deceleration signal when said tachometer voltage exceeds said throttle voltage, means responsive to said deceleration signal for subtracting said difference voltage from said tachometer voltage to provide a first resultant voltage, means for combining said terrain voltage with said first resultant voltage to provide a deceleration mode control voltage, means responsive to said acceleration signal for adding said difference voltage with said tachometer voltage to provide a second resultant voltage, and means for combining said terrain voltage with said second resultant voltage to produce an accelerate mode control voltage.

3. In a vehicle as recited in claim 1 wherein said means enabled responsive to said motor drive signal for applying current to said motor in an amount determined by said control signal comprises a first circuit means for generating a first pulse followed after an interval determined by the amplitude of said control voltage by a second pulse, first silicon control rectifier means coupling said battery to said electric motor, and means to which said first and second pulses are applied for enabling said first silicon control rectifier means to conduct over the interval between said first and second pulses, said means enabled responsive to said regenerative signal for applying charging voltage from said electric motor to said battery in an amount determined by said control voltage comprises:

a second circuit means for generating a third pulse followed after an interval determined by the amplitude of said control voltage by a fourth pulse, a step-up transformer having an input and output, second silicon control rectifier means coupling said electric motor to said step-up transformer input, rectifier means coupling said step-up transformer output to said battery, means to which said third and fourth pulses are applied for enabling said second rectifier means to conduct over the interval between said third and fourth pulses.

4. In a vehicle as recited in claim 3 wherein said first circuit means for generating a first pulse followed after an interval determined by the amplitude of said control voltage by a second pulse comprises a first sawtooth waveform generator, a first and a second Schmitt trigger circuit each having a set and reset state circuit means to which said control voltage and the output of said sawtooth waveform generator are applied for driving said first Schmitt trigger circuit from its reset to its set state only while said sawtooth waveform voltage exceeds said control voltage, means for driving said second Schmitt trigger circuit from its reset to its set state responsive to the output of said first Schmitt trigger circuit going from its set to its reset state, and first and second transformer means respectively coupling said first and second Schmitt trigger circuits to said first silicon control rectifier means.

5. In a vehicle as recited in claim 3 wherein said second circuit means for generating a third pulse followed after an interval determined by the amplitude of said control voltage by a fourth pulse comprises:

a second sawtooth generator, a third and fourth Schmitt trigger circuit each having a sEt and a reset state, circuit means to which the control voltage and the output of said sawtooth waveform generator are applied for driving said third Schmitt trigger circuit from its reset to its set state only while said sawtooth waveform exceeds said control voltage, means for driving said fourth Schmitt trigger circuit from its reset to its set state responsive to the output of said third Schmitt trigger circuit going from its set to its reset state, and third and fourth transformer means respectively coupling said third and fourth Schmitt trigger circuits to said second silicon control rectifier means.

6. In a vehicle drive system wherein an electrical motor is driven from a battery under the control of a throttle for driving said vehicle over terrain, the improvement comprising:

means for establishing a voltage in response to the setting of the throttle representative of a desired speed, tachometer means driven by said motor for generating a voltage representative of the actual speed of said motor, slope sensing means for establishing a voltage representative of the terrain slope, combining means to which said slope sensing means throttle and tachometer means voltages are applied for establishing a control voltage representative of the control effect required to attain the speed specified by the setting of said throttle, comparator means to which said control voltage and said tachometer means voltage are applied for producing a motor drive indicating signal when said control voltage exceeds said speed tachometer means voltage and for producing a regenerative signal when said tachometer means voltage exceeds said control voltage, first pulse width modulating means energized response to said motor drive signal and to which said control voltage is applied for producing a succession of first and second pulses wherein the interval between a first and a succeeding second pulse is varied in response to said control signal, second pulse width modulating means energized responsive to said regenerative signal and to which said control signal is applied for producing a succession of first and second pulses wherein the interval a first and a succeeding second pulse is varied in response to said control signal, first silicon control rectifier means coupling said battery to said motor, means for applying said pulse width modulated means output to said first silicon control rectifier means for enabling current flow therethrough during the interval between each first and succeeding second pulse, second silicon-controlled rectifier means coupling said motor to said battery, and means for applying said second pulse width modulated means output to said second silicon control rectifier means for enabling it to apply voltage received from said motor to said battery during the interval between each second and succeeding first pulse.

7. Apparatus as recited in claim 6 wherein said combining means includes:

a first Schmitt trigger circuit, means for establishing a difference signal representative of the difference between said tachometer means voltage and said throttle setting voltage, means responsive to said difference signal indicating that said tachometer means voltage exceeds the amplitude of said throttle setting voltage for driving said first Schmitt trigger circuit to its set state, first transistor means enabled responsive to the set state output of said first Schmitt trigger circuit, means for applying said tachometer means voltage to said first transistor means, means for applying said difference voltage to said first transistor means for reducing the throttle speed means voltage amplitude in response thereto, means for combining said terrain slope voltage with the output of said first transistor means to provide a control signal representative of deceleration.

8. Apparatus as recited in claim 7 wherein there is included a second Schmitt trigger cIrcuit, means responsive to said difference signal voltage indicating that the throttle setting representative voltage amplitude exceeds the tachometer means voltage amplitude for driving said second Schmitt trigger circuit to its set state, a second transistor means enabled responsive to said set state output of said second Schmitt trigger circuit, means for applying said difference voltage to said second transistor means, means for adding the output of said second transistor means to said speed representative voltage, and means for combining the output of said second transistor means with said terrain slope voltage to provide a control voltage indicative of the requirement for an acceleration.

9. Apparatus as recited in claim 6 wherein said means to which said tachometer means voltage and said control voltage are applied for generating a motor signal or a regenerative signal includes a second difference circuit, means for applying said tachometer means voltage and said control voltage to said second difference circuit for producing a voltage representative of the difference therebetween, a third Schmitt trigger circuit and a fourth Schmitt trigger circuit, means responsive to the output of said second difference circuit indicating that said control voltage amplitude is larger than said tachometer means voltage amplitude for driving said third Schmitt trigger circuit to its set state whereby the output of said third Schmitt trigger circuit in its set state represents a motor drive indicating signal, and means for applying the output of said difference circuit to said fourth Schmitt trigger circuit for driving it to its set state when said difference circuit output represents that the amplitude of said tachometer means voltage exceeds the amplitude of said control voltage whereby the output of said fourth Schmitt trigger circuit in its set state represents a regenerative signal.

10. Apparatus as recited in claim 6 wherein said first pulse width modulator means comprises a first sawtooth generator, a fifth Schmitt trigger circuit, a sixth Schmitt trigger circuit, means to which said control voltage and said first sawtooth waveform generator output are applied for driving said fifth Schmitt trigger circuit to its set state over the interval during which said sawtooth waveform generator output amplitude exceeds the amplitude of said control signal, whereby said fifth Schmitt trigger circuit produces a first pulse, and means for driving said sixth Schmitt trigger circuit from the reset output of said fifth Schmitt trigger circuit whereby said sixth Schmitt trigger circuit produces a second output pulse.

11. Apparatus as recited in claim 10 wherein said first silicon-controlled rectifier means includes a first silicon control rectifier, first transformer means for applying said fifth Schmitt trigger first output pulse to said first silicon control rectifier for causing it to become conductive whereby current is applied from said battery to said motor, and second transformer means to which said fifth Schmitt trigger circuit second output pulse is applied for disenabling said first silicon control rectifier whereby current flow from the battery to the motor is terminated.

12. Apparatus as recited in claim 6 wherein said second pulse width modulator means comprises:

a second sawtooth waveform generator, a seventh and an eighth Schmitt trigger circuit, means to which said control voltage and said second sawtooth waveform generator voltage are applied for driving said seventh Schmitt trigger circuit to its set state responsive to said sawtooth waveform voltage amplitude exceeding said control voltage amplitude, whereby a said seventh Schmitt trigger circuit is driven to its set state to produce a third output pulse, means responsive to said seventh Schmitt trigger circuit returning from its set to its reset state for driving said eighth Schmitt trigger circuit to its set state whereby a fourth output pulse is generated.

13. Apparatus as recited in claim 12 wherein said second silicon control rectifier means includes a second silicon control rectifier, step-up transformer means coupling said second silicon control rectifier to said battery, means coupling said motor to said second silicon control rectifier, means for applying said third output pulse to said second silicon control rectifier to enable it to apply current from said motor to said step up transformer, and means responsive to said fourth output pulse for rendering said second silicon control rectifier inoperative.

14. The method of controlling a vehicle speed moving over a terrain wherein the vehicle drive system includes an electrical motor driven from a battery at a speed determined by a throttle setting comprising:

establishing a tachometer voltage representative of said vehicle speed, establishing a throttle voltage representative of a throttle setting, establishing a terrain voltage representative of terrain slope, combining said tachometer, throttle and terrain voltages to provide a control voltage, comparing said control voltage with said tachometer voltage to establish either a motoring mode signal or a regenerative mode signal, applying current from said battery to said motor responsive to said motoring mode signal in an amount determined by said control signal, and applying voltage from said motor to said battery responsive to said regenerative mode signal in an amount determined by said control signal.