Full Software AC Servo Controllers with Dynamic Pulse Width Modulation

Full software AC servo controllers have been developed with special real time software in the Windows NT operating system. The full software AC servo controllers are able to control multiple AC servomotors with the CPU of a personal computer. The controller handles 1 00s commutation and current feedback, 200s velocity feedback, and 1 ms position feedback. The full software AC servo controllers provide the ultimate flexibility, low cost, and powerful graphic user interface in Windows NT. They can also take advantage of all the Windows NT features, such as networking. The software alone performs all the calculations in the CPU of the host computer in the full software AC servo controller. The software control makes the implementation of any algorithm much easier. Advanced control algorithms, such as d-q axis control and decoupling control, are implemented utilizing the flexibility of the controllers. These control algorithms generate accurate torque current and less iron loss in the AC servomotors. They also cancel the nonlinear terms of the motor equations to make the motor dynamics steady with changing angular velocity by feed forward control. A new renovated pulse width modulation (PWM) method, called "Dynamic PWM" has been designed and formulated. The Dynamic PWM eliminates most of the delay problems associated with the current PWM. The effectiveness of the dynamic PWM was verified through simulation in the Matlab software. High frequency and instability analyses were done in the simulation. The dynamic PWM showed about one PWM period less phase lag than the regular PWM. It was also able to handle a much higher gain in the current feedback than the regular PWM. The future implementation algorithm and procedures using the full software AC servo controllers were also developed. Thesis Supervisor: Haruhiko Harry Asada Title: Professor of Mechanical Engineering