Digital motor controller

Apparatus for controlling a brushless motor having a rotor, stator windings and sensing means for providing analog position signals indicative of the position of said rotor with respect to said stator windings, comprising:

• digitizing means, responsive to said sensing means, for digitizing said analog position signals;
• digital signal processing means for selecting said windings to be energized, said digital signal processing means is responsive to said digitizing means, for processing said digitizing signals into digital position signals including a speed feedback means, responsive to said digitizing means, for determining speed feedback of said a motor,
• commutation means, responsive to said digital position signals, for generating commutation commands;
• and
• inverter means, responsive to said commutation commands, for energizing the windings selected by said digital signal processing means whereby said digitized signals from each sensor form envelopes;
• wherein said speed feedback means includes selecting means, responsive to said digital position signals, for selecting an envelope having a non-zero slope;
• difference means, responsive to said selecting means, for taking difference of successive digitized signals from said selected envelope;
• and dividing means, responsive to said difference means, for dividing said difference by a sampling time, an output of said dividing means providing a signal indicating said speed feedback.

Apparatus for controlling a motor having a rotor and first, second and third stator windings, comprising:

• first, second and third sensing means, responsive to said rotor, for providing analog signals indicating the proximity of said rotor to said first, second and third windings, respectively;
• sampling means, responsive to outputs of said first, second and third position sensors, for sampling said analog signals at selected times;
• analog to digital converter means, responsive to said sampling means, for converting said sampled analog signals to digitized signals;
• digital signal processor means, responsive to said digitized signals, for providing first, second and third position signals, wherein said first position signal goes high when the value sampled from said first sensing means is greater than the value sampled from said second sensing means, said second position signal goes high when the value sampled from said second sensing means is greater than the value sampled from said third sensing means;
• and said third position signal goes high when the value sampled from said third sensing means is greater than the value sampled from said first sensing means;
• commutation means, responsive to said first, second and third position signals, for generating commutation commands;
• and
• inverter means, responsive to outputs of said commutation means, for energizing the windings in response to said commutation commands.

A method for controlling a brushless motor having a rotor, a stator, sensor means for providing analog signals indicating the position of said rotor relative to windings of said stator and inverter means for energizing selected stator windings in response to commutation commands, said method comprising the steps of:

• (a) sampling said analog signals;
• (b) digitizing said sampled analog signals;
• (c) generating digital position signals for each winding, said digital position signals being set at a first state when said rotor is closer in proximity to a corresponding winding than the next winding, said digital position signal being set at a second state when rotor is closer in proximity to the next winding than to a corresponding winding;
• (d) decoding said position digital signals into said commutation commands;
• (e) decoding said digital position signals to determine which envelope of a corresponding winding has a non-zero slope;
• (f) taking the difference of successive samples of said winding having the non-zero slope;
• and
• (g) dividing said difference by sampling time to yield motor speed.