Failure detection method for electric vehicles and fail-safe control method using this method
First Claim
1. An electric vehicle equipped with a battery for supplying electric power, a PWM inverter for converting DC current of that battery into AC power of variable voltage and variable frequency, a three phase AC motor for driving the vehicle, current sensors for detecting the current flowing through that three phase AC motor, a three phase AC current reference generation means that generates a three phase AC current reference for controlling the phase current that flows through the winding of that three phase AC motor, and a signal generation means that generates the signal which is applied to the gate of the PWM inverter based on the three phase AC current reference and the current of the three phase AC motor, wherein a failure detection method for the electric vehicle comprises the step of using at least two phase currents that are detected directly by the current sensors in determining disorder in that current sensors.
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Abstract
An object of the present invention is to secure safe driving of electric vehicles by enabling torque control regardless of sensor disorder. In the present invention, the mode of current sensor disorder is detected by a sensor disorder detection means. If it is found as a result that only 1 out of 3 current sensors is failing, the current of the failing current sensor is estimated by 2 normal current sensors and the torque control of the motor is continued by the ordinary torque control system. If 2 or more current sensors are found to be failing, a torque control system based on an AC current reference operation means is formed to control the motor torque based on the AC current reference. If a sensor failure detection means determines that only 1 phase is failing in the speed sensor, the motor torque is controlled by using the remaining 1 phase to detect the rotating angular speed of the motor. If all speed sensors are failing but the current sensors are normal, the motor torque is controlled by estimating the motor torque from the 3 phase AC current. If both the current sensors and the speed sensors are found to be failing, the motor torque is controlled based on the estimated torque control and rotating angular speed to continue the driving that is needed to avoid dangerous situations.
83 Citations
24 Claims
- 1. An electric vehicle equipped with a battery for supplying electric power, a PWM inverter for converting DC current of that battery into AC power of variable voltage and variable frequency, a three phase AC motor for driving the vehicle, current sensors for detecting the current flowing through that three phase AC motor, a three phase AC current reference generation means that generates a three phase AC current reference for controlling the phase current that flows through the winding of that three phase AC motor, and a signal generation means that generates the signal which is applied to the gate of the PWM inverter based on the three phase AC current reference and the current of the three phase AC motor, wherein a failure detection method for the electric vehicle comprises the step of using at least two phase currents that are detected directly by the current sensors in determining disorder in that current sensors.
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5. An electric vehicle which is comprised of a battery for supplying electric power, a PWM inverter for converting DC current of that battery into AC power of variable voltage and variable frequency, a three phase AC motor, a speed sensor installed to accommodate the shaft of that three phase AC motor, a drive system comprised of several current sensors for detecting the current flowing through the winding of that three phase AC motor, a torque reference operation means that determines the torque reference of the three phase AC motor according to accelerator opening, an AC current reference operation means that determines the amplitude and phase of the AC current reference that flows through the winding of the three phase AC motor based on that torque reference and the rotating angular speed, a current control means that determines a three phase AC voltage reference in such a way that said three phase AC current will follow that AC current reference, and a PWM signal generation means that determines the gate signal which is applied to said PWM inverter based on that three phase AC voltage reference,
wherein a fail-safe control method of this electric vehicle comprises the steps of switching said AC current reference operation means and the current control means to an AC voltage reference operation means when the failure of one of said current sensors is identified, said AC voltage reference operation means obtains said AC voltage reference utilizing the torque reference obtained from said torque reference operation means and the rotating angular speed of the three phase AC motor obtained from said speed sensor, thereby determining the gate signal which is applied to said PWM inverter based on an AC voltage reference which was obtained from said AC voltage reference operation means.
- 18. An electric vehicle equipped with a battery for supplying electric power, a PWM inverter for converting DC current of that battery into AC power of variable voltage and variable frequency, a three phase AC motor for driving the vehicle, a speed sensor for generating several signals that have frequencies that are proportionate to the rotating angular speed of that three phase AC motor, current sensors for detecting the current flowing through that three phase AC motor, a three phase AC current reference generation means that generates a three phase AC current reference for controlling the phase current that flows through the winding of that three phase AC motor, and a signal generation means that generates signal which is applied to the gate of the PWM inverter based on the three phase AC current reference and the current of the three phase AC motor, wherein a failure detection method for the electric vehicle comprises the step of using at least two phase currents that are detected directly from said current sensors in determining disorder in said current sensors.
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22. An electric vehicle which is comprised of a battery for supplying electric power, a PWM inverter for converting DC current of that battery into AC power of variable voltage and variable frequency, a three phase AC motor, a speed sensor installed to accommodate the shaft of that three phase AC motor, a drive system comprised of several current sensors equipped on the winding of that three phase AC motor, a torque reference operation means that determines the torque reference of the three phase AC motor according to accelerator opening, an AC current reference operation means that determines the amplitude and phase of the AC current reference that flows through the winding of said three phase AC motor based on that torque reference and the rotating angular speed, a current control means that determines a three phase AC voltage reference in such a way that the three phase AC current will follow that AC current reference, and a PWM signal generation means that determines the gate signal which is applied to said PWM inverter based on that three phase AC voltage reference,
wherein the electric vehicle includes a fail-safe control means having a three phase AC voltage reference operation means, a switching means for switching said AC current reference operation means and the current control means to said AC voltage reference operation mean when the failure of one of said current sensors is identified, said AC voltage reference operation mean obtains said AC voltage reference utilizing the torque reference obtained from said torque reference operation means and the rotating angular speed of said three phase AC motor obtained from said speed sensor, thereby determining the gate signal which is applied to said PWM inverter based on an AC voltage reference which was obtained from said three phase AC voltage reference operation means.
Specification