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Abstract
Recently a great deal of interest has been focused on the stepper motors applicationsespecially in electromechanical equipments. The main usage of stepper motors is inrobotic applications. Stepper motors were previously controlled using special digital controllers that satisfy special applications. The constant speed is obtained from steppermotors by open loop control with constant frequency sequencersThe main advantage of stepper motors is they are various reliable in operation with openloop control techniques. In open loop control, the unknown load torque / time relation reduces average motor speed resulted from taking into account the worst loading conditions during design to avoid losing of motor synchronization. Open loop control is sub-optimal when dealing with different loading conditions. Closed loop control overcomes this disadvantage by varying the excited coils at a certain rotor position to avoid synchronization lose; therefore the motor performance can be optimized for all loading conditions As a result of wide variation in stepper motors, the designer changes their manufacture techniques to increase both accuracy and torques production to be compatible with modern application In this thesis a more general digital closed loop controller is adopted with phase locked loop frequency multiplication technique. The adopted controller satisfies closed loop lead excitation angle control process for a claw teeth permanent magnet stepper motor The proposed controller is designed, implemented, tested and put in working order to produce different lead excitation angles. Also an experimentally proposed controller controls the lead excitation angle to obtain maximum motor speed at different loading conditions. The proposed controller has been built using both of sequential and combinational logic circuits to deal with different loading conditions. The proposed controller is applied on a claw-teeth permanent magnet stepper motor with 7.5 mechanical degree step angle The motor under consideration is simulated mathematically depending on the experimentally measured stator flux current curves at different rotor angles. Moreover a complete motor system model is taken into consideration to verify the experimental results.