Spice modeling of a stepper motor with its control, drive and load

SPICE MODELING OF A STEPPER MOTOR WITH ITS CONTROL, DRIVE, AND LOAD.
JESS CHEN, Dept.. 62-33 Bldg. 150 DOMINIC GAEIRO, Dept.62-33 Bldg 150 ED STOECKERT, Dept 62-14 Bldg 551
Lockheed Missiles and Space Co. Inc. 1111 Lockheed Way Sunnyvale, Ca 94086 hm resistors simply prevent SPICE topological errors. Multipliers determine the desired oscillation frequency by controlling the coupling between C1 and C3. The additional VCO in Figure 3 adds detent torque. Detent required an additional VCO because each stable rotor position corresponds to a positive-to-negative zero crossing in the angle versus detent torque curve. Assigning a stable equilibrium (detent) to each pole face required computing sin(2*8*P/2) where P is the number of poles and 8 = Ut =rotor angle . To include detents between pole faces, the model computed sin(4*8*P/2). The extra VCO generated sin(4*8*P/ 2) by running at four times the mechanical angular velocity. Figure 4 compares rotor positions with and without the detent torque as the system responds to a slew command. Without detent , load momentum moved the rotor between drive pulses such that subsequent pulses moved the rotor backwards. Because the detent torque passed through several cycles per step, numerical errors accumulated from step to step and slowly discharged the detent VCO cosine capacitor until the detent torque became negligible. Because the VCO is a modified &oscillator, amplitude depended only on initial conditions. We tried three ways of maintaining the detent torque amplitude:

ABSTRACT This paper describes SPICE modeling of a complete stepper motor system. Using a voltage controlled oscillator to track sine and cosine of rotor angle, and an electrical analog of the mechanical assembly, SPICE simulated interactions between electrical and mechanical subsystems. The simulations confirmed the effectiveness of preloading against gear backlash and dead-beating against excitation of mechanical resonances. A method for extracting frequency