A control method for a low-speed direct-drive AC servo system

Abstract

The invention discloses a method for controlling a low-speed direct drive type alternating-current servo system. A structure for controlling the low-speed direct drive type alternating-current servo system comprises a position closed loop, a speed closed loop, a quadrature-axis current closed loop and a direct-axis current closed loop. A method for indirectly observing the rotation angle and the rotation speed of an alternating-current servo motor is used for improving the detection precision of the rotation angle and the rotation speed. A rotation angle observation value obtained through indirect observation is used for rotation transformation and position feedback, and a speed observation value is used for speed feedback. Through detection of a winding current of the alternating-current servo motor and rotation transformation of the alternating-current servo motor, a quadrature-axis current feedback signal and a direct-axis current feedback signal are obtained respectively. A torque dither signal is introduced, so that the alternating-current servo motor is in the micro-dither state when the alternating-current servo motor rotates at a low speed or is static, and the low-speed dead zone and the hysteresis characteristic are eliminated. According to the method for controlling the low-speed direct drive type alternating-current servo system, high-precision low-speed direct drive can be achieved just through an ordinary alternating-current servo motor and an ordinary incremental photoelectric pulse coder.

Description

technical field [0001] The invention relates to an AC servo system in the industrial field, in particular to a control method for a low-speed direct-drive AC servo system for realizing high-precision position control. Background technique [0002] The AC servo system is driven by a rare earth permanent magnet synchronous motor (PMSM). The AC servo system is the basic component of automation and informatization in the manufacturing industry. It is mostly used in the technical field involving contour trajectory tracking control. Its work at low speeds Performance is one of the most important performance. A conventional AC servo system must be connected to a mechanical load through a reduction mechanism. The direct-drive AC servo system is referred to as the direct-drive AC servo system. It can be directly coupled with the mechanical load without using a deceleration mechanism. The benefits of direct drive are obvious. Since the transmission deceleration mechanism is omitted, ...

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Problems solved by technology

[0026] Although the M / T method takes into account the speed measurement accuracy of the high-speed section and the low-speed section, it also has defects. The speed measurement time Td is not fixed. When the motor speed is very low, the speed measurement time Td may still be longer and the speed measurement bandwidth is relatively low.

[0027] The above three methods directly use the output signal of the photoelectric pulse encoder to detect the speed of the AC servo motor. When the servo AC servo motor is running at low speed, due to the limitation of the precision of the ordinary photoelectric pulse encoder, a large quantization error will inevitably occur. It affects the speed control accuracy, manifested in the poor stability of the speed when running at low speed, and the output torque is obviously reduced, which does not meet the requirements of the direct drive AC servo system

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