Method and apparatus for detecting velocity profiles of a spinning rotor of a polyphase DC motor

A circuit for operating a polyphase dc motor having a plurality of driving coils that are commutatively energized in a predetermined sequence to rotate a rotor, comprising:

• a commutation sequence generator for generating commutation sequence signals for controlling which of said plurality of driving coils are energized a delayed time after a back emf of a floating one of said coils crosses zero;
• a period counter, an acceleration counter, and a delay counter, said period counter being an up counter, and said acceleration and delay counters being down counters;
• a source of clock pulses connected to clock said period and acceleration counters;
• a programmable clock pulse divider connected to receive and divide said clock pulses to provide clock pulses at a selectively divided frequency to said delay counter;
• and a circuit operative when said zero crossing is detected to load a count from said period counter into said delay and acceleration counters and then to reset said period counter;
• an output from said acceleration counter being connected to programmably determine the frequency of clock pulses provided by said programmable clock pulse divider to said delay counter.

A circuit for operating a polyphase dc motor having a plurality of driving coils that are commutatively energized in a predetermined sequence to produce rotation of a rotor, comprising:

• a commutation sequence generator for generating commutation sequence signals for controlling which of said plurality of driving coils are energized;
• circuitry for receiving a back emf of at least one of said driving coils when said at least one of said driving coils is in a floating state;
• rotor position determining circuitry for determining when the back emf received by said circuitry for receiving the back emf crosses a reference voltage;
• commutation delay circuitry for determining a delay after an occurrence of the back emf crossing the reference voltage, for initiating a next commutation sequence;
• a circuit for measuring times between successive occurrences of the back emf crossing the reference voltage, whereby a change in time between successive occurrences of the back emf crossing indicates an acceleration of the rotor;
• a circuit connected to adjust the delay of said commutation delay circuit in response to the circuit for measuring times between successive occurrences of the back emf crossing the reference voltage indicating an acceleration of the rotor;
• wherein said circuit connected to adjust the delay of said commutation delay circuit, comprises:
• an up counter and first and second down counters;
• a source of clock pulses connected to clock said up and said second down counters;
• a first programmable clock pulse divider connected to receive and programmably divide said clock pulses to provide clock pulses at a selectively divided frequency to said first down counter;
• means operative when said reference voltage crossing detector detects a reference voltage crossing to load a count from said up counter into said first and second down counters and then to reset said up counter;
• an output from said second down counter being connected to programmably determine the frequency of clock pulses provided by said first programmable clock pulse divider;
• whereby said first counter determines a commutation switching time of said commutation sequence and said second counter determines a acceleration of said rotor.

A method for operating a polyphase dc motor, comprising:

• determining an acceleration of a rotor of the motor, and
• adjusting a commutation delay in response to the determined acceleration by provided a look-up table of desired commutation delays of corresponding acceleration values;
• retrieving a commutation delay for each acceleration value determined;
• operating the motor in accordance with the retrieved commutation delays.