Electromechanical energy conversion system

• US 4,686,437 A
• Filed: 09/17/1986
• Issued: 08/11/1987
• Est. Priority Date: 06/20/1980
• Status: Expired due to Term

• Current Assignee: Kollmorgen Technologies Corporation
• Original Assignee: Kollmorgen Technologies Corporation
• Inventors: Kidd, H. Keith, Langley, Lawrence W.
• Primary Examiner(s): Dobeck, Benjamin
• Application Number:
  US06/909,031
• Time in Patent Office: 328 Days
• Field of Search: 318/138, 318/254, 318/254 A, 318/696
• US Class Current: 318/400.01
• CPC Class Codes: H02P 23/0077 Characterised by the use of a particular software algorithm
• CPC Class Codes: H02P 6/085 in a bridge configuration

Abstract

An electromechanical energy conversion system comprising a brushless motor and a stored program controller for controlling motor operation in a plurality of modes in accordance with internally generated and/or external commands.

Claims

1. A motor control system comprising:

a brushless electric machine having field and wound members movable relative to each other, said wound member having a plurality of energizable windings;

a position sensor associated with said motor to provide a position indication of relative position of said field and wound members;

switching means associated with said motor for measuring a controllable parameter of the motor operation;

a switching array including a plurality of solid state switching devices connected to selectively energize said windings;

a programmable microprocessor operatively connected to receive said position indications and said measured controllable parameter and to control said switching array; and

said microprocessor being programmed to determine the instantaneous on/off state for each of said switching devices

to energize said windings at a predetermined pulse energy level determined according to said measured controllable parameter, and

to commutate said winding energization according to said position indications.

2. A motor control system according to claim 1 wherein said programmable microprocessor is programmable to operate in at least two different active modes.

3. A motor control system according to claim 1 further including:

current sensing means for sensing the current flow to a winding being energized,

wherein said microprocessor is programmed to calculate a high value and a low value for current flow to said winding and

to turn on one of said switching devices when said sensed current flow is below said high value, and

to turn off said switching device in the "on" state when said sensed current flow falls below said low value.

4. A motor control system according to claim 1 wherein said position indications and said measured controllable parameter are derived from Hall sensors associated with said motor.

5. An electromechanical energy conversion system comprising:

a brushless motor having a rotor and a stator having a plurality of energizeable windings;

sensors associated with said motor for sensing the relative position of said rotor and stator and for producing a sector signal indicative of the sector in which a rotor pole is located and a sector change signal when a rotor pole moves from one sector to another;

switching circuitry connected to said windings for controlling the flow of current therethrough;

means for measuring the rotor velocity; and

control means connected to said sensors, said means for measuring rotor velocity and said switching circuitry, said control means comprising a current modulator for comparing the measured rotor velocity with a commanded rotor velocity and for producing a current command signal for energizing windings when winding currents fall below a first value and for deenergizing windings when winding currents exceed a second va1ue, and a logic array for controlling said switching circuitry in accordance with said sector and current command signals so as to maintain the measured rotor velocity approximately equal to the commanded rotor velocity.

6. An electromechanical energy conversion system according to claim 5 wherein said means for measuring the rotor velocity comprises means for counting sector change signals for a predetermined time.

7. An electromechanical energy conversion system according to claim 5 wherein said means for measuring the rotor velocity comprises means for counting clock pulses occurring between sector change signals.

8. An electromechanical conversion system comprising:

a brushless motor having a rotor and a stator having a plurality of energizeable windings;

sensors associated with said motor for sensing the relative position of said rotor and stator and for producing a sector signal indicative of the sector in which a rotor pole is located;

switching circuitry connected to said windings for controlling the flow of current therethrough;

means for measuring the rotor position; and

control means connected to said sensors, said means for measuring rotor position and said switching circuitry, said control means comprising a current modulator for comparing the measured rotor position with a commanded rotor position and for producing a current command signal for energizing windings when winding currents fall below a first value and for deenergizing windings when winding currents exceed a second value, and a logic array for controlling said switching circuitry in accordance with said sector and current command signals so as to maintain the actual rotor position approximately equal to the commanded rotor position.

9. An electromechanical energy conversion system according to claim 8 further comprising means for initially acquiring the position of said rotor.

10. An electromechanical energy conversion system according to claims 8 or 9 wherein said means for measuring the rotor position comprises:

means for predicting a future rotor position; and

means for comparing the present rotor position with said future rotor position and for producing a signal when the present rotor position reaches the future rotor position.

11. An electromechanical energy conversion system according to claim 8 wherein said sensors comprise Hall devices and wherein the present rotor position is indicated by quasilinear voltages produced by said Hall devices.

12. An electromechanical energy conversion system according to claim 10 further comprising:

means for producing a sector change signal when a rotor pole moves from one sector to another;

means responsive to said sector change signal for providing a signal indicative of rotor velocity; and

means for scaling the predicted rotor positions so that at low speeds the position increments are relatively small and at high speeds the position increments are relatively large.

13. An electromechanical energy conversion system comprising:

a brushless motor having a rotor and a stator having a plurality of energizeable windings;

sensors associated with said motor for sensing the relative position of said rotor and stator and for producing electrical signals indicative thereof;

switching circuitry connected to said windings for controlling the flow of current therethrough;

power measuring means for producing an electrical signal indicative of the power delivered by said motor; and

control means connected to said sensors, said switching circuitry and said power measuring means, said control means comprising a current modulator for producing a current command signal having a variable duty cycle, and a logic array for controlling said switching circuitry so as to maximize the power delivered by said motor.

14. An electromechanical energy conversion system according to claim 13 wherein said power measuring means produces a signal indicative of rotor velocity and said logic array controls said switching circuitry so as to maximize rotor velocity.

15. A method for controlling the conversion of energy by an electromechanical system employing a brushless motor having a rotor and a stator having a plurality of energizeable windings, comprising the steps of:

sensing the relative position of said rotor and stator;

producing a sector signal indicative of a sector in which a rotor pole is located;

energizing said windings in accordance with said sector signal;

sensing the current flowing through said windings;

producing a sector change signal when a rotor pole moves from one sector to another;

measuring the rotor velocity;

comparing said measured rotor velocity with a commanded rotor velocity; and

modulating the flow of current through said windings by energizing windings when winding currents fall below a first value and deenergizing windings when winding currents exceed a second value so as to maintain said measured velocity approximately equal to said commanded velocity.

16. A method according to claim 15 wherein said step of measuring the rotor velocity comprises the step of counting sector change signals over a predetermined period of time.

17. A method according to claim 15 wherein said step of measuring the rotor velocity comprises the step of counting clock pulses occurring between sector change signals.

18. A method according to claim 15 further including the step of producing a torque command signal for controlling the direction of rotor rotation.

19. A method for controlling the conversion of energy by an electromechanical system employing a brushless motor having a rotor and a stator having a plurality of windings, comprising the steps of:

sensing the relative position of said rotor and stator;

producing a sector signal indicative of a sector in which a rotor pole is located;

energizing said windings in accordance with said sector signal;

sensing the current flowing through said windings;

measuring the rotor position;

comparing said measured rotor position with a commanded rotor position; and

modulating the flow of current through said windings by energizing windings when winding currents fall below a first value and deenergizing windings when winding currents exceed a second value so as to maintain said measured position approximately equal to said commanded position.

20. A method for controlling the conversion of energy by an electromechanical system employing a brushless motor having a rotor and a stator having a plurality of windings, comprising the steps of:

sensing the relative position of said rotor and stator;

producing a sector signal indicative of a sector in which a rotor pole is located;

energizing said windings in accordance with said sector signal;

sensing the current flowing through said windings;

producing a sector change signal when a rotor pole moves from one sector to another;

measuring the rotor velocity;

measuring the rotor position;

comparing said measured velocity with a commanded velocity;

comparing said measured position with a commanded position; and

modulating the flow of current through said windings by energizing windings when winding currents fall below a first value and deenergizing windings when winding currents exceed a second value so as to initially maintain said measured rotor velocity approximately equal to said commanded rotor velocity and tc subsequently maintain said measured rotor position approximately equal to said commanded rotor position.

21. A method according to claim 20 further including the step of producing a torque command signal for controlling the direction of rotor rotation.

22. A method for controlling the conversion of energy by an electromechanical system employing a brushless motor having a rotor and a stator having a plurality of windings comprising the steps of:

sensing the relative position of said rotor and stator;

energizing said windings by switching the voltage applied thereto;

producing an indication of the power delivered by said motor; and

varying the duty cycle of said switching so as to maximize said indication of motor power.

23. A method according to claim 22 wherein said step of producing an indication of the power delivered by said motor comprises the step of measuring the rotor velocity.