Controller for electric vehicle
First Claim
1. A controller for a battery powered electric vehicle of the type in which a torque command signal corresponding to an extent of actuation of an accelerator input device controls a motor for driving the vehicle in response to the torque command signal, which controller comprises:
- a comparator coupled to receive and compare a terminal voltage of said battery and a preset first comparison voltage;
first clock means for measuring a first elapsed time during a period when said terminal voltage is smaller than the first comparison voltage, and for detecting when the first elapsed time exceeds a first preset time period;
calculation means for producing a torque limiting command signal having a value which decreases to a set lower limit value according to a predetermined pattern, starting at the time when said first clock means detects that said first elapsed time exceeds said first preset time period;
means for comparing said torque command signal with said torque limiting command signal and for selecting the smaller thereof; and
means for controlling operation of the vehicle motor in response to the selected signal.
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Accused Products
Abstract
The invention provides an electric vehicle controller in which the generated motor torque is limited when the voltage of the vehicle battery decreases during running, in order to suppress over-discharge of the battery. A high torque can be obtained for a short period, however, even in the torque limiting period, and over-discharge is prevented by stopping electric power converting means in a final stage of discharge voltage of the battery. According to the invention, during operation of the vehicle, the battery terminal voltage is monitored and compared with a first comparison value V1. If the battery voltage falls below V1, a first counter commences measurement of the time period during which this condition continues. If the time period measured by the first counter reaches a preset value t1, torque limitation is initiated. In the torque limitation state, a torque command signal, generated by the control to operate the vehicle motor, is compared with the signal generated by the vehicle accelerator, and the signal having the lower value is thereafter used to control operation of the vehicle motor. In order to provide the capability to generate higher levels of torque for brief periods during torque limitation, the torque limitation process is terminated if the accelerator pedal is released completely.
29 Citations
10 Claims
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1. A controller for a battery powered electric vehicle of the type in which a torque command signal corresponding to an extent of actuation of an accelerator input device controls a motor for driving the vehicle in response to the torque command signal, which controller comprises:
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a comparator coupled to receive and compare a terminal voltage of said battery and a preset first comparison voltage; first clock means for measuring a first elapsed time during a period when said terminal voltage is smaller than the first comparison voltage, and for detecting when the first elapsed time exceeds a first preset time period; calculation means for producing a torque limiting command signal having a value which decreases to a set lower limit value according to a predetermined pattern, starting at the time when said first clock means detects that said first elapsed time exceeds said first preset time period; means for comparing said torque command signal with said torque limiting command signal and for selecting the smaller thereof; and means for controlling operation of the vehicle motor in response to the selected signal. - View Dependent Claims (2, 3, 4, 5, 6)
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7. Method for controlling a battery powered motor vehicle having an accelerator input device, a vehicle battery, an electric motor, and an electric power converter for supplying electric power to the vehicle motor in response to a torque command signal, said method comprising the steps of:
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generating a desired torque command signal in response to an extent of actuation of said accelerator input device; comparing a terminal voltage of said vehicle battery with a preset first comparison voltage; measuring a first elapsed time during a period when said terminal voltage is smaller than the first comparison voltage; detecting when the first elapsed time exceeds a first preset time period; generating a torque limiting command signal having a value which decreases to a set lower limit according to a predetermined pattern, starting when the first elapsed time signal exceeds said first preset time period; comparing magnitude of said desired torque command signal and said torque limiting command signal; selecting a smaller of said desired torque command signal and said torque limiting command signal; and supplying said selected smaller signal as said torque command signal to control operation of said electric power converter. - View Dependent Claims (8, 9, 10)
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Specification