Switched reluctance motor controller with sensorless rotor position detection

A method of sensing a position of a rotor of a switched reluctance motor and for appropriately commutating the motor in response to the position of the rotor, the method comprising:

• a) applying a first voltage pulse to a first phase of the motor;
• b) storing a value representative of a current produced in response to the first voltage pulse thereby forming a stored value;
• c) after the step of storing, applying a first series of one or more additional voltage pulses to the first phase of the motor for producing a first series of values representative of corresponding current pulses;
• d) comparing each of the first series of values to a predetermined threshold;
• e) after one of the first series of values exceeds the predetermined threshold, applying a second series of one or more additional voltage pulses to the first phase of the motor for producing a second series of values representative of corresponding current pulses;
• f) comparing each of the second series of values to the stored value;
• and
• g) after one of the second series of values is below the stored value by at least an offset, providing a commutation signal.

An apparatus for driving a switched reluctance motor, the apparatus comprising:

• a) a sensing circuit for forming sensing signals, one sensing, signal corresponding to each phase of the motor, wherein each of the sensing signals is representative of an inductance of the corresponding phase at selected intervals;
• b) a selecting circuit coupled to the sensing circuit, the selecting circuit for selecting one of the sensing signals wherein the inductance of the phase corresponding to the selected one of the sensing signals has an initial value after a first commutation of the motor, falls to a minimum value and then rises again;
• c) a storing circuit coupled to the selecting circuit, the storing circuit for storing the initial value, thereby forming a stored value;
• and
• d) a determining circuit coupled to the storing circuit, the determining circuit for determining when the inductance rises to a value that is approximately equal to the stored value less an offset after having reached the minimum value and when the inductance rises to the value that is approximately equal to the stored value less the offset, initiating a second commutation of the motor.

An apparatus for driving a switched reluctance motor, the apparatus comprising:

• a) a sensing circuit for sensing a current in each phase of the motor;
• b) a finite state machine for providing a signal indicative of a phase of the motor to be sensed;
• c) a selecting circuit for selecting a phase to be sensed by the sensing circuit, wherein the selecting circuit is coupled to the sensing circuit and to the finite state machine;
• d) a storage circuit for storing a first value representative of an inductance of the phase to be sensed during a first interval, the storage circuit coupled to the selecting circuit;
• e) a first comparing circuit for comparing a threshold to a second value representative of an inductance of the phase to be sensed during a second interval, the first comparing circuit coupled to the selecting circuit;
• and
• f) a second comparing circuit for comparing the first value to a third value representative of an inductance of the phase to be sensed during a third interval wherein the second comparing circuit is coupled to the selecting circuit and wherein the second comparing circuit is enabled by the first comparing circuit and wherein the second comparing circuit enables the finite state machine for indicating a next phase of the motor to be sensed.

The apparatus for sensing a position of a rotor of a switched reluctance motor and for appropriately commutating the motor in response thereto, the apparatus comprising:

• a) a plurality of coils, each having an inductance;
• b) means for selectively and sequentially driving the coils for turning the rotor;
• c) means for sensing the inductance of a coil that is not being driven;
• and
• d) means for commutating from driving one coil to another upon sensing a predetermined change in the inductance.

A method of sensing a position of a rotor of a switched reluctance motor and for appropriately commutating the motor in response to the position of the rotor, the method comprising:

• a) applying a first voltage pulse to a first phase of the motor;
• b) storing a value representative of a current produced in response to the first voltage pulse thereby forming a stored value;
• c) after the step of storing, applying a series of one or more additional voltage pulses to the first phase of the motor for producing a series of values representative of corresponding current pulses;
• d) comparing each of the series of values to the stored value;
• and
• e) after one of the series of values is below the stored value, providing a commutation signal.

A method of sensing a position of a rotor of a switched reluctance motor and for appropriately commutating the motor in response to the position of the rotor, the method comprising:

• a) applying a first voltage pulse to a first phase of the motor;
• b) storing a value representative of a current produced in response to the first voltage pulse thereby forming a stored value;
• c) after the step of storing, applying a first series of one or more additional voltage pulses to the first phase of the motor for producing a first series of values representative of corresponding current pulses;
• d) comparing each of the first series of values to a predetermined threshold;
• e) after one of the first series of values exceeds the predetermined threshold, applying a second series of one or more additional voltage pulses to the first phase of the motor for producing a second series of values representative of corresponding current pulses;
• f) comparing each of the second series of values to the stored value;
• and
• g) after one of the second series of values is below the stored value, providing a commutation signal.