Method and apparatus for controlling torque and torque ripple in a variable reluctance motor

A method for controlling torque and torque ripple in a variable reluctance motor having at least one phase and including a stator and a rotor arranged for movement about a common axis and relative to one another, said method comprising the steps of:

• sensing the angular position of the rotor relative to the stator;
• supplying a torque command signal representative of a desired torque to be developed by the motor;
• generating a plurality of torque waveforms for each phase of the number of phases associated with the motor, said generated torque waveforms corresponding to the actual torque developed by the motor when excited by an electrical current having a predetermined, constant magnitude;
• producing from said generated torque waveforms a table of values representative of the magnitude of electrical current at each sensed angular position and corresponding to the actual torque developed by the motor when the motor is excited by an electrical current having that value;
• storing each value contained in the table of values at an addressable storage location in a memory device, each of said storage locations being defined by the intersection of a given torque value and a given rotor position, said values being stored for each of said phases associated with the motor;
• accessing and retrieving from each storage location associated with each phase a value of current stored at the location and corresponding to the desired torque at the given rotor position;
• generating an electrical current having a magnitude equal to the value of electrical current accessed and retrieved from the storage location defined by the sensed angular position and the torque command signal, and
• supplying the generated electrical current to the motor to cause the motor to develop a torque substantially equal to the desired torque at each of said sensed angular positions so that the developed torque has a substantially flat and ripple free response characteristic.