Sensorless motor control using the rate of change of the inductive rise time
AssigneeTexas Instruments Incorporated
InventorTriet M. Tieu
Life of this patent
Estimating the term…
Abstract
A conventional method used for a startup mode for a brushless direct current (DC) motor employed complementary inductive rise times. Specifically, inductive rise times rise times for a driving state and its complementary state were compared to one another such that when the inductive rise times cross a switching point had been reached. This methodology, however, significantly affects the efficiency of the driving torque and power consumption. Here, however, a derivative of the inductive rise time is employed, which can determine the switching event without the need for a use of a complementary state, improving motor performance.
Claims21
A method comprising:
- determining a current commutation state of a brushless direct current (DC) motor, wherein the current commutation state is one of a plurality of commutation states;
- calculating a derivative of an inductive rise time for the brushless DC motor based at least in part on a measurement of the inductive rise time;
- and
- advancing the brushless DC motor to a next commutation state based at least in part on the magnitude of the derivative,
- wherein the inductive rise time further comprises a first inductive rise time and a second inductive rise time, and wherein step of calculating further comprises:
- determining the first inductive rise time for a first interval;
- determining the second inductive rise time for a second interval, wherein each of the first and second intervals have a predetermined duration;
- calculating a difference between the first and second inductive rise times;
- and
- dividing the difference between the first and second inductive rise times by the predetermined duration.
A method comprising:
- determining first and second inductive rise times for each of a pair of interval during a first commutation state of a brushless DC motor, wherein each interval has a predetermined duration;
- calculating the rate of change between the first and second inductive rise times;
- and
- advancing the brushless DC motor to a second commutation state based at least in part on the magnitude of the rate of change.
An apparatus comprising:
- a drive circuit that is configured to drive a brushless DC motor;
- a sense circuit that is coupled to drive circuit, wherein sense circuit is adapted to measure a first and second coil currents for a pair of intervals during a first commutation state of the brushless DC motor, and wherein each interval has a predetermined duration;
- control circuitry that is coupled to the sense circuit and the drive circuit, wherein the control circuitry is configured to determines first and second inductive rise times from first and second coil currents, and wherein the control circuitry is configured to calculate the rate of change between the first and second inductive rise times, and wherein the control circuit is configured to provide a signal to the drive circuit to advance the brushless DC motor to a second commutation state based at least in part on the magnitude of the rate of change.
Dependencies are inferred from the claim text.