Thermal actuation based 3-DoF non-resonant microgyroscope using MetalMUMPs

High force, large displacement and low voltage consumption are a primary
concern for microgyroscopes. The chevron-shaped thermal actuators are unique in terms of
high force generation combined with the large displacements at a low operating voltage in
comparison with traditional electrostatic actuators. A Nickel based 3-DoF micromachined
gyroscope comprising 2-DoF drive mode and 1-DoF sense mode oscillator utilizing the
chevron-shaped thermal actuators is presented here. Analytical derivations and finite
element simulations are carried out to predict the performance of the proposed device using
the thermo-physical properties of electroplated nickel. The device sensitivity is improved
by utilizing the dynamical amplification of the oscillation in 2-DoF drive mode using an
active-passive mass configuration. A comprehensive theoretical description, dynamics and
mechanical design considerations of the proposed gyroscopes model are discussed in
detail. Parametric optimization of gyroscope, its prototype modeling and fabrication using
MetalMUMPs has also been investigated. Dynamic transient simulation results predicted that the sense mass of the proposed device achieved a drive displacement of 4.1μm when a
sinusoidal voltage of 0.5V is applied at 1.77 kHz exhibiting a mechanical sensitivity of
1.7μm /o/s in vacuum. The wide bandwidth frequency response of the 2-DoF drive mode
oscillator consists of two resonant peaks and a flat region of 2.11 kHz between the peaks
defining the operational frequency region. The sense mode resonant frequency can lie
anywhere within this region and therefore the amplitude of the response is insensitive to
structural parameter variations, enhancing device robustness against such variations. The
proposed device has a size of 2.2 x 2.6 mm2, almost one third in comparison with existing
M-DoF vibratory gyroscope with an estimated power consumption of 0.26 Watts. These
predicted results illustrate that the chevron-shaped thermal actuator has a large voltagestroke
ratio shifting the paradigm in MEMS gyroscope design from the traditional
interdigitated comb drive electrostatic actuator. These actuators have low damping
compared to electrostatic comb drive actuators which may result in high quality factor
microgyroscopes operating at atmospheric pressure.