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Position measuring devices with sinusoidal measuring signals are widely used in position-controlled servo drives in industrial automation, e.g., for machine tools or semiconductor production machines. Usually, the feedback signal for the speed or velocity controller is calculated from the measured position. Therefore, position measuring errors affect these control loops. This study presents an analytic error model that considers non-ideal sinusoidal measuring signals with basic deviations (amplitude differences, offset errors, and phase shift) as well as signal harmonics. The model was used to systematically investigate the influence of signal quality and the number of signal periods from position measuring devices on speed ripple, across a wide range of speeds. A test stand with a high-resolution reference angle measuring device was used to confirm the results.
A hybrid current and acceleration control is presented and shown to improve the load disturbance behavior of servo drives significantly without additional sensor effort. The feedback signal of the acceleration control loop is calculated from the position data of the motor encoder. Hence, position measuring errors influence this control loop and lead to speed ripple. Therefore, the presented design of the acceleration control loop considers both load sensitivity and position measuring errors.
In der vorliegenden Arbeit wird der Einfluss einer Beschleunigungsregelung auf das Regelverhalten von Servoantrieben untersucht. Auf einen Beschleunigungssensor wird verzichtet. Die Istbeschleunigung wird aus dem Positionsmesswert berechnet. Anhand eines verifizierten Modells für Positionsmessfehler wird der Einfluss der Positionsauflösung und der Messsignalqualität auf die berechnete Beschleunigung dargestellt. Basierend auf diesen Ergebnissen wird das Konzept einer kombinierten Strom- und Beschleunigungsregelung entwickelt und dessen Funktionalität nachgewiesen.
Increased productivity in industrial processes can be achieved by dynamic and accurate positioning of servo drives. Therefore, improvement of servo drive dynamics using latest technologies in the key components such as inverter, control system and position measuring device are investigated. Using Gallium Nitride (GaN) or Silicon Carbide (SiC) semiconductors for motor inverters enables energy efficient operation up to pulse width modulation (PWM) frequencies of 500 kHz. This allows motor filters with small component sizes. As a result, high motor efficiency, low torque ripple, high control bandwidth and almost ideal sinusoidal output voltages are achieved. Experiments on a 200 kHz Gallium Nitride inverter with sine wave motor filter show a current control loop bandwidth of 3.2 kHz and almost ideal sinusoidal phase voltages. The achieved bandwidths of the speed and position control loops are 318 Hz and 106 Hz, respectively.