Use of MEMS gyroscopes in active vibration damping for HSM-driven positioning systems

Hybrid Stepper Motors (HSM) are the workhorses in many low-end motion control systems, given their low cost and high reliability. The resolution of the positioning systems using this type of motors has been increased with the introduction of the microstepping driving technique, even if, being operated in open loop, HSM cannot provide the actual control of the load position. Recently, the authors have proposed an innovative control scheme, based on the use of a load side acceleration sensor, that implements the active damping of a HSM-driven mechanical load, in presence of a flexible mechanical transmission between motor and load. This is a typical industrial scenario, in which the problem of the oscillations arising from the excitation of the mechanical resonance by various disturbances (including torque ripple) is usually addressed by severely limiting the overall dynamic performance. In this paper, we propose the extension of the proposed technique, with the use of a MEMS gyroscope to implement an active damping control strategy, which allows for the improvement of the dynamic response and an excellent rejection of the oscillations caused by the torque ripple. The proposed technique does not require the re-design of the existing equipments, since it is based on the real time modulation of the orientation of the stator flux, aimed at producing a compensating torque and, in turn, damping the oscillatory modes. Experimental results, obtained with a HSM-driven camera positioning unit, confirm the effectiveness of the proposed solution.