Motor control device and electric power steering system using said motor drive circuit
AssigneeHitachi Automotive Systems, Ltd.
InventorsNobuyasu Kanekawa, Ryoichi Kobayashi, Tomonobu Koseki, Takuro Kanazawa
Life of this patent
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Abstract
The purpose of the present invention is not only to reduce ripple current but also to improve operation efficiency by reducing heat generation. When n is defined as an integer of 2 or more, a motor control device of the present invention drives n sets of windings by n sets of inverters. The motor control device is characterized in that when said n sets of inverters output high power, at least one or more of said n sets of inverters are set to have an output duty cycle of 100%.
Claims11
A motor control device for a motor, comprising:
- a set of n coils driven by a set of n inverters, n being defined as an integer of 2 or more;
- and
- two redundant control devices, each of the redundant control devices being configured to individually control the motor, such that upon failure of one of the two redundant control devices, the other of the two redundant control devices is configured to continue controlling the motor, wherein
- at least one inverter in the set of n inverters has an output duty cycle of 100% when output of the set of n inverters is higher than a given value, the at least one inverter switching another inverter of the set of n inverters with a predetermined frequency, and
- the motor device is configured to operate at a given cycle, the given cycle being 1/(the predetermined frequency), the given cycle is less than a thermal time constant of each of the at least one inverter and the another inverter.
An electric power steering system comprising:
- a set of n coils driven by a set of n inverters, n being defined as an integer of 2 or more;
- a steering wheel;
- a rotation shaft attached to the steering wheel;
- a torque sensor attached to the rotation shaft;
- a steering mechanism;
- a motor;
- and
- two redundant control devices, each of the redundant control devices being configured to individually control the motor, such that upon failure of one of the two redundant control devices, the other of the two redundant control devices is configured to continue controlling the motor, wherein
- the steering mechanism is steered by the rotation shaft,
- the steering mechanism or the rotation shaft has steering force assisted by the motor,
- the motor control device controls the motor,
- at least one inverter in the set of n inverters has an output duty cycle of 100% when output of the set of n inverters is higher than a given value, the at least one inverter switching another inverter of the set of n inverters with a predetermined frequency,
- the motor device is configured to operate at a given cycle, the given cycle being 1/(the predetermined frequency), the given cycle is less than a thermal time constant of each of the at least one inverter and the another inverter.
Dependencies are inferred from the claim text.