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Purpose This paper intends to lay a background knowledge towards the feasibility of developing a bottom-drive variable capacitance micromotor (VCM) using a surface micromachining process (SMP). The purpose of this paper is to determine the possibility of neglecting the bending of the rotor plates caused by the electrostatic normal forces when deploying a set of mechanical supports. Design/methodology/approach A multiphysics simulation approach is considered in order to analyse the coupled electromechanical effects in a steady state and to evaluate if the proposed geometries are useful to reduce the bending of the plates. Findings A surfaced micromachined bottom-drive VCM requires mechanical reinforcement in order to eliminate the risk of an electrical short circuit caused by the deformation in the rotor plates. The combination of an external supporting ring and anchored structural ribs on top of the rotor poles is sufficient to neglect the deformation in the poles of the rotor. Originality/value An original analysis with the objective of setting a background in the development of a bottom-drive electrostatic micromotor using a SMP is presented.

This paper presents the design of a biaxial capacitive accelerometer that takes advantages of a single-mass configuration to provide two orthogonal axes of sensitivity. The accelerometer structure is based on the SUMMiT V fabrication process. A set of fixed electrodes provides reliable measurements of capacitance in the two orthogonal directions. An analytical model based on the Euler-Bernoulli stress theory is introduced for variable cross-sectional area beams and is validated with a finite element analysis. In order to avoid a short circuit between fixed and movable electrodes, four displacement limiters were designed. The displacement limiters prevent out-of-plane displacement of the seismic mass and can withstand an impact of 250,000 G. A two-dimensional transient analysis of the seismic mass was carried out to confirm a linear oscillation behavior for either direction on the operation plane. The natural frequencies in the vibration modes of the two axes of interest are 462.5 and 463.2 Hz. It is also shown that the principal stresses in the beams are smaller than the fracture strength of polysilicon.

A New Adaptive Self-Tuning Fourier Coefficients Algorithm for Periodic Torque Ripple Minimization in Permanent Magnet Synchronous Motors (PMSM) Torque ripple occurs in Permanent Magnet Synchronous Motors (PMSMs) due to the non-sinusoidal flux density distribution around the air-gap and variable magnetic reluctance of the air-gap due to the stator slots distribution. These torque ripples change periodically with rotor position and are apparent as speed variations, which degrade the PMSM drive performance, particularly at low speeds, because of low inertial filtering. In this paper, a new self-tuning algorithm is developed for determining the Fourier Series Controller coefficients with the aim of reducing the torque ripple in a PMSM, thus allowing for a smoother operation. This algorithm adjusts the controller parameters based on the component’s harmonic distortion in time domain of the compensation signal. Experimental evaluation is performed on a DSP-controlled PMSM evaluation platform. Test results obtained validate the effectiveness of the proposed self-tuning algorithm, with the Fourier series expansion scheme, in reducing the torque ripple.