Systems and methods of electric motor control

An electromotive force (EMF) detection circuit that provides an indication of a position of a rotor in an electric motor with at least a first bipolar winding and a second bipolar winding, the EMF detection circuit comprising:

• a first sense circuit connected in series with a first transistor of a first leg of a first H-bridge, where the first H-bridge energizes the first bipolar winding of the electric motor, and where the first sense circuit is configured to detect a first EMF associated with the first bipolar winding when the first leg of the first H-bridge is active;
• a second sense circuit connected in series with a second transistor of a second leg of the first H-bridge, where the second sense circuit is in-phase with the first sense circuit, where the second sense circuit is configured to detect the first EMF associated with the first bipolar winding when the second leg of the first H-bridge is active, and where the second sense circuit generates approximately equal output as the first sense circuit in response to an approximately equal amount of EMF detected;
• a third sense circuit connected in series with a third transistor of a third leg of a second H-bridge, where the second H-bridge energizes the second bipolar winding of the electric motor, where the third sense circuit is configured to detect a second EMF associated with the second bipolar winding when the third leg is active, where the third sense circuit is out-of-phase with respect to the first sense circuit, and where the third sense circuit generates approximately equal output as the first sense circuit in response to an approximately equal amount of EMF detected between the first EMF and the second EMF;
• a fourth sense circuit connected in series with a fourth transistor of a fourth leg of the second H-bridge, where the fourth sense circuit is out-of-phase with respect to the first sense circuit, where the fourth sense circuit is configured to detect the second EMF associated with the second bipolar winding when the fourth leg of the second H-bridge is active, and where the fourth sense circuit generates approximately equal output as the first sense circuit in response to an approximately equal amount of EMF detected;
• a combiner circuit adapted to generate an output responsive to a difference in the first EMF and the second EMF, where the first EMF is detected by summing outputs of the first sense circuit and the second sense circuit, and the second EMF is detected summing outputs of the third sense circuit and the fourth sense circuit;
• and
• a comparator circuit coupled to the output of the combiner circuit, the comparator circuit configured to generate a PWM commutation signal when the electric motor is operated in a PWM mode and to generate a commutation signal corresponding to a first EMF phase when the electric motor is operated in a non-PWM mode, where the comparator circuit is further configured to provide a filtered signal that provides an output that is approximately proportional to displacement of the rotor, rather than to the EMF phase.

A method of generating a sense signal for an electric motor with a first bipolar winding and a second bipolar winding, the method comprising:

• detecting a first electromotive force (EMF) from the first bipolar winding by monitoring current flowing through a first leg of a first H-bridge, where the first H-bridge activates the first bipolar winding and by monitoring current flowing through a second leg of the first H-bridge;
• detecting a second EMF from the second bipolar winding by monitoring current flowing through a third leg of a second H-bridge, and by monitoring current flowing through a fourth leg of a second H-bridge;
• where the second H-bridge activates the second bipolar winding;
• and
• combining the first EMF with the second EMF to generate the sense signal, where such combining combines the second EMF out-of-phase with respect to the first EMF.

A method of controlling hunting in an electric motor, comprising:

• sequencing the motor by applying a voltage to at least one winding;
• sensing a commutation of the motor in response to the voltage applied to the at least one winding;
• determining a current time interval between the sequencing and the commutation;
• comparing the current time interval with a previous time interval between a previous sequencing and a previous commutation to determine a time interval difference;
• and
• applying the interval difference as feedback to a motor control circuit, the motor control circuit responsive to the time interval difference to reduce hunting of the motor.

A method of controlling the power applied to an electric motor, comprising:

• sequencing the motor by applying a voltage to at least one winding;
• sensing a commutation of the motor in response to the voltage applied to the at least one winding;
• determining a time interval between the sequencing and the commutation;
• and
• adjusting the voltage in response to the time interval.

A method of commutating an electric motor while pulse width modulating a drive to the motor, the method further comprising:

• determining from a monitored time whether to activate a sequencing of the motor, where the monitored time is allocated to an “on” time and an “off” time, where the “on” time corresponds to a first period of time when sequencing of the motor is enabled and where the “off” time corresponds to a second period of time when sequencing of the motor is disabled;
• receiving a commutation signal;
• setting a set commutation signal in response to the receiving of the commutation signal just before the monitored time corresponds to the “off” time;
• waiting for the monitored time to correspond to the “off” time when the commutation signal is received when the monitored time corresponds to the “on” time;
• waiting for a setting of the set commutation signal;
• waiting for a pulse in response to the setting of the set commutation signal;
• providing the sequencing signal in response to receiving the pulse;
• sequencing the motor in response to the sequencing signal and to the monitored time;
• and
• activating a pulse timer in response to the sequencing signal.

A method of controlling an output power of an electric motor comprising:

• computing a desired commutation time, where the desired commutation time approximately corresponds to a time when a first EMF phase signal is desired to be detected;
• waiting for an activation of a commutation signal, where the commutation signal corresponds to the first EMF phase;
• receiving the activation of the commutation signal;
• measuring an actual time of the activation of the commutation signal;
• storing the actual time;
• comparing the desired commutation time to the actual time;
• waiting for a timing pulse, where the timing pulse is related to a desired speed of the motor;
• sequencing the motor in response to receiving the timing pulse;
• and
• adjusting a direct current power supply to the motor in response to the comparison between the desired commutation time and the actual time.

A method of controlling hunting in an electric motor, the method comprising:

• waiting for an activation of a commutation signal, where the commutation signal corresponds to a predetermined EMF phase;
• receiving the activation of the commutation signal;
• removing power applied to windings of the electric motor in response to the activation of the commutation signal;
• waiting for a timing pulse, where the timing pulse is related to a desired speed of the motor;
• applying power to the motor by sequencing the motor in response to receiving the timing pulse;
• and
• activating a pulse timer in response to sequencing the motor.

A method of controlling hunting in an electric motor, the method comprising:

• waiting for an activation of a commutation signal, where the commutation signal corresponds to a predetermined EMF phase;
• receiving the activation of the commutation signal;
• measuring a commutation time, where the commutation time is a time from sequencing to the activation of the commutation signal;
• adding an offset to the commutation time;
• storing the commutation time into an anti-hunt timer;
• activating the anti-hunt timer;
• waiting for a time-out of the anti-hunt timer;
• waiting for a timing pulse, where the timing pulse is related to a desired speed of the motor;
• applying power to the motor by sequencing the motor in response to receiving the timing pulse;
• activating a pulse timer in response to sequencing the motor;
• and
• subtracting the commutation time from a time of the sequence, and storing the result of the subtraction to the offset.

A method of controlling hunting in an electric motor, the method comprising:

• maintaining a clock time;
• waiting for an activation of a commutation signal, where the commutation signal corresponds to a predetermined EMF phase;
• receiving the activation of the commutation signal;
• storing the clock time as a commutation time in response to the activation of the commutation signal;
• computing a sequence-to-commutation time, where the sequence-to-commutation time is the commutation time minus a prior sequence time;
• computing a rate, where the rate is the sequence-to-commutation time minus a last commutation time;
• adding the rate to a pulse timer if the rate is negative;
• storing the sequence-to-commutation time to the last commutation time;
• waiting for a timing pulse, where the timing pulse is generated in response to a time-out of the pulse timer;
• sequencing the motor in response to receiving the timing pulse;
• activating a pulse timer in response to sequencing the motor;
• and
• storing the clock time as the sequence time in response to sequencing the motor.

A method of detecting an out of synchronization condition in an electric motor, the method comprising:

• waiting for an activation of a commutation signal, where the commutation signal corresponds to a predetermined EMF phase;
• receiving the activation of the commutation signal;
• waiting for a timing pulse, where the timing pulse is related to a desired speed of the motor;
• storing a value of a sync register, where the sync register stores an indication of a difference between a first number of activations of the commutation signal detected and a second number of timing pulses detected from a time of a prior sequencing;
• sequencing the motor in response to receiving the timing pulse;
• activating a pulse timer in response to sequencing the motor;
• determining a time from a prior sequencing;
• and
• providing an alert of the out of synchronization condition when the sync register does not correspond to a reset value, and resetting the sync register to the reset value after providing the alert.

A method of synchronizing a plurality of electric motors that are not mechanically coupled, the method comprising:

• detecting that a first commutation signal has been activated from each of the plurality of synchronized motors, where the activation of the first commutation signal corresponds to a first predetermined EMF phase;
• waiting for a pulse timer to time out after the first commutation signal has been detected for each of the plurality of synchronized motors;
• sequencing each of the plurality of motors in response to the time-out of the pulse timer;
• and
• activating the pulse timer in response to the sequencing of the plurality of motors.

A method of synchronizing a plurality of electric motors that are not mechanically coupled, the plurality of electric motors including a master motor and at least one slave motor, the method comprising:

• sequencing the master motor at least partially in response to a commutation signal from the master motor;
• counting the sequencing of the master motor in a first count;
• counting a sequencing of the slave motor in a second count;
• comparing the first count to the second count;
• and
• sequencing the slave motor at least partially in response to a commutation signal from the slave motor and a comparison between the first count and the second count.

A process for automatically starting an electric motor comprising:

• preparing the motor to be sequenced with a first starting sequence;
• sequencing the motor in accordance with the first starting sequence;
• preparing the motor to be sequenced with a second starting sequence;
• loading a pulse timer with a first predetermined time;
• activating the pulse timer;
• waiting for a time-out of the pulse timer;
• sequencing the motor in accordance with the second starting sequence in response to the time-out of the pulse timer;
• preparing the motor to be sequenced with a third starting sequence;
• activating the pulse timer;
• waiting for the time-out of the pulse timer;
• sequencing the motor in accordance with the third starting sequence in response to the time-out of the pulse timer;
• preparing the motor to be sequenced with a fourth starting sequence;
• loading a pulse timer with a second predetermined time;
• sequencing the motor in accordance with the fourth starting sequence in response to the time-out of the pulse timer;
• preparing the motor to be sequenced with a fifth starting sequence;
• waiting for an activation of a subsequent commutation signal, where the commutation signal corresponds to a predetermined EMF phase;
• measuring an elapsed time between the sequencing of the motor in accordance with the fourth starting sequence and the activation of the subsequent commutation signal;
• ending the starting process when the elapsed time is less than a third predetermined time;
• and
• restarting the starting process with a new value for the first predetermined time when the elapsed time is greater than or equal to the third predetermined time.

A process of detecting an error in stopping an electric motor comprising:

• (a) sequencing the motor, where the sequencing corresponds to a last sequencing commanded by a motor controller to stop the motor;
• (b) detecting a first activation of a commutation signal, where the commutation signal corresponds to a predetermined EMF phase;
• (c) measuring a first elapsed time, where the first elapsed time is from a time of the sequencing of the motor to a time of the detection of the first activation of the commutation signal;
• (d) detecting a new activation of the commutation signal;
• (e) measuring a second elapsed time, where the second elapsed time is from a time of a preceding activation of the commutation signal to a time of the new activation of the commutation signal;
• (f) comparing the first elapsed time to the second elapsed time;
• and
• (g) providing an error indicating that the motor is not holding to a detent position when the second elapsed time is less than a predetermined multiple of the first elapsed time.

A process of detent-zero positioning a motor with substantially reduced ringing, the method comprising:

• (a) sequencing the motor;
• (b) waiting for an activation of a first commutation signal;
• (c) determining whether a modified commutation mode is enabled;
• (d) preparing the motor for sequencing with a forward sequence phase if the modified commutation mode is enabled;
• (e) preparing the motor for sequencing with a reverse sequence phase if the modified commutation mode is not enabled;
• (f) sequencing the motor;
• (g) comparing a rate of the activations of the first commutation signal to a predetermined rate;
• (h) waiting a first elapsed time if the rate of the activations of the commutation signal is lower than the predetermined rate;
• (i) preparing the motor for sequencing with a stop phase;
• (j) sequencing the motor
• (k) ending the process where the rate of the activations exceeds the predetermined rate;
• (l) waiting for a second elapsed time;
• and
• (m) returning to (b).

A method of detent-zero positioning with substantially reduced ringing, the method comprising:

• (a) sequencing the motor;
• (b) converting a commutation signal from analog to digital to detect a first commutation signal;
• (c) waiting for an activation of the first commutation signal;
• (d) determining whether the first commutation signal is detected higher than a predetermined level;
• (e) preparing the motor for sequencing with a forward sequence phase when the first commutation signal is detected higher than the predetermined level;
• (f) preparing the motor for sequencing with a reverse sequence phase when the first commutation signal is not detected higher than the predetermined level;
• (g) sequencing the motor;
• (h) waiting a first elapsed time;
• (i) preparing the motor for sequencing with a stop phase;
• (j) sequencing the motor
• (k) waiting for a second elapsed time;
• and
• (l) returning to (c).

An electromotive force (EMF) detection circuit that generates a sense signal for an electric motor with a first unipolar winding and a second unipolar winding, the EMF detection circuit comprising:

• means for detecting a first EMF from the first unipolar winding by monitoring current flowing through the first unipolar winding;
• means for detecting a second EMF from the second unipolar winding by monitoring current flowing the second unipolar winding;
• and
• means for combining the first EMF with the second EMF to generate the sense signal, where such combining combines the second EMF out-of-phase with respect to the first EMF.

An electromotive force (EMF) detection circuit that generates a sense signal for an electric motor with a first bipolar winding and a second bipolar winding, the EMF detection circuit comprising:

• means for detecting a first EMF from the first bipolar winding by monitoring current flowing through a first leg of a first H-bridge, where the first H-bridge activates the first bipolar winding and by monitoring current flowing through a second leg of the first H-bridge;
• means for detecting a second EMF from the second bipolar winding by monitoring current flowing through a third leg of a second H-bridge, and by monitoring current flowing through a fourth leg of a second H-bridge;
• where the second H-bridge activates the second bipolar winding;
• and
• means for combining the first EMF with the second EMF to generate the sense signal, where such combining combines the second EMF out-of-phase with respect to the first EMF.