High-Precision Control Strategy for Ultra-Low Speed and Variable Speed Motion of Satellite Platform Pointing Mechanisms

Satellite pointing mechanisms for earth observation require ultra-low speed scanning (approximately 70″/s) and precise variable-speed compensation. However, traditional Field-Oriented Control (FOC) suffers from significant velocity bias and instability under these conditions. To address these issues, this paper proposes a position-loop-based speed control scheme integrated with a variable structure control strategy. By substituting the speed command with a position loop, the proposed method effectively suppresses steady-state velocity bias, while the variable structure strategy mitigates fluctuations during variable-speed motion. Experimental results indicate that, compared to traditional FOC, the proposed method reduces velocity bias error by over 30% during uniform tracking and decreases the amplitude of velocity fluctuations by more than 40% in variable-speed scenarios. This strategy significantly enhances the control precision of satellite pointing mechanisms and improves on-orbit imaging compensation accuracy.