Research On AC Servo With Feedforward Control Based On Adaptive Sensor

With the rapid development of aerospace, high precision medical machine, intelligent robot, vehicle and precision NC machine tools, the requirements for the indexes of servo technology are increasing. In order to realize high-performance servo control technology, the servo system needs to have a good response characteristic and the ability of inhibition for the disturbance. An advanced feasible control method needs to be researched, and a control system with high precision, high response and good robustness should be developed which provide guarantee for NC equipment industry and military capabilities is an urgent affair.In order to meet high response and high precision control requirement, the essential characteristic of the system which be researched is needed. Mathematical model of permanent magnet synchronous motor has been built at beginning of the dissertation, then the response characteristic of ac servo system will be analyzed theoretically to prepare for further research. Through theoretical analysis, the harmful effects to the system’s response characteristic from the lag of feedback loop will be proven, the factors which affect the system’s response characteristic of current loop and mechanical loop will be researched to lay a foundation of improvement for system’s response characteristic.The precision and real-time performance of feedback loop is the base of high precision and high response control. For realizing the high precision feedback of the angle value from magnetism encoder, an adaptive characteristic magnetism encoder has been researched, and a method based on arctangent trans-interval tabulation will be designed in this dissertation. In order to eliminate the error of angle value caused by the temperature drift from magnetism encoder, a kind of neurons adaptive algorithm for compensating the temperature drift of magnetism encoder will be proposed, and the high precision angle value detection of servo system will be achieved. In order to meet the needs of current value’s high precision detection, the time sequence of current calculation will be analyzed, a current bipolar state observer will be put forward which eliminates current detection delay.The current loop is the inner loop of AC servo control system, and the core section for realizing the high precision AC servo control. In order to achieve the high precision current control, this dissertation analyze the control characteristic of traditional single-interrupt current loop control structure, consider its deficiency and put forward the feedforward control method with high frequency angle error compensation, eliminate the deviation from angle value transmission, decrease the oscillation amplitude of phase current caused by pulse width modulation, realize the high precision control for current loop. Improving the frequency of PWM will worsen the harmful effects which caused by dead-time. In order to eliminate that, a dead zone compensation feedforward control method based on dead zone characteristic of power module will be proposed, and the dead-time error compensation will be realized. In order to improve the response speed of current loop, a method of feedforward control method with harmonic injection which using table lookup will be put forward based on the method of voltage regulation scaling, so that the utilization rate of system’s bus voltage and the precision of voltage vector’s calculation will be increased, the current’s high precision, high response control will be actualized.The mechanical loop’s high precision, high response control and the external disturbance inhibiting ability are the necessary condition for achiev ing the accurate tracking of speed and position, based on the feedforward control structure and feedback structure with state observer to realize two-degree-freedom motion control. In order to improve the system’s response speed further, based on current feedforward structure design the speed feedforward controller which realize the closed loop control of the feedforward controller, and a gain self-adjusting controller based on this structure will be proposed for improving the system’s external disturbance inhibiting ability, then the high response of mechanical loop and good inhibition to external disturbance will be actualized. For getting the value of speed, position and non-electric physical accurately and adaptability under variable parameter condition, an optimization method of neurons rotational inertia based on position loop’s state observer will be proposed in this dissertation, the system rotational inertia’s adaptive correction will be realized, and the accurate observation of speed and position’s value will be achieved which improve the adaptability and control precision of the system under variable parameter condition.Based on the adaptive characteristic magnetism encoder which be proposed in this dissertation, a high response AC servo control s ystem will be developed, and the combination of servo control system hardware and software will be completed. Base on this, the experimental verification of the control calculation which be proposed will be done. The result shows that the current loop’s control strategy which be proposed has a good response characteristic; the mechanical loop’s control structure could track the speed command and position command accurately, a good external disturbance inhibiting ability has also been proved.