MEMS Gyroscope Hot Startup With Time-Based Biasing
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Solution Overview
Problem
MEMS gyroscopes experience performance issues during hot start-up, characterized by overshoot and prolonged instability due to residual oscillations after power-down, which are not efficiently addressed by existing solutions that require wait times or additional detection phases, leading to increased size, power consumption, and error risks.
Innovation Solution
A microelectromechanical gyroscope device with an integrated electronic circuit that includes a time counter to measure the duration since power-down, adjusting the start-up phase based on this interval to distinguish between cold and hot start-ups, thereby optimizing energy use and avoiding overshoots.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a wait time is implemented after power-down to allow residual oscillations to decay, then hot start-up stability is improved, but loss of time increases
Solution Approach 1:
The patent applies preliminary action by implementing a damping phase immediately after power-down that actively suppresses residual oscillations before a subsequent start-up occurs. The control circuit detects the presence of residual oscillations and applies a damping signal to reduce them, rather than waiting passively for natural decay. This preliminary damping action eliminates the need for extended wait times before hot start-up, resolving the contradiction between stability and time loss.
2Measurement precision
If additional detection phases are added to detect residual oscillations, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies universality by making the existing control circuit perform multiple functions: it continues to drive the mobile mass for normal operation, detects residual oscillations after power-down, and generates damping signals to suppress those oscillations. Rather than adding separate dedicated detection and damping circuits, the control circuit is configured to handle all these tasks, thereby improving measurement precision without significantly increasing device complexity.
3Productivity
If the mobile mass is driven at maximum energy during start-up, then productivity is improved, but loss of energy increases and overshoot occurs during hot start-up
Solution Approach 1:
The patent applies dynamics by making the driving energy variable rather than constant. During normal operation, the mobile mass is driven at maximum energy for fast response. However, during hot start-up conditions when residual oscillations are detected, the control circuit dynamically adjusts the driving energy to a lower level to avoid overshoot, and applies damping signals to suppress residual oscillations. This dynamic adjustment of energy levels improves productivity when needed while reducing energy loss and preventing overshoot during hot start-up.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces hot start-up times and oscillation amplitude instability without significant energy or resource consumption, ensuring reliable and prompt angular velocity detection.
Implementation Method 1
provide a bias signal to the detection structure to cause oscillation at a resonance frequency
Implementation Method 2
When a rotation at a certain angular velocity (the value whereof is to be detected) is applied to a mobile mass of the MEMS gyroscope, which is driven with a linear velocity, the mobile mass feels an apparent force, called Coriolis force
Implementation Method 3
The integrated electronic circuit includes a time counter stage (12) designed to measure a duration of a time interval from the previous power-down
Implementation Method 4
The displacement of the mobile mass may, for example, be detected in a capacitive manner, determining, in a resonance condition, the capacitance variations caused by the movement of movable detection electrodes
Data Source
AI summary
A microelectromechanical gyroscope device has: a detection structure, provided with a mobile mass; and an integrated electronic circuit, coupled to the detection structure and which provides a bias signal to the detection structure to cause its oscillation at a resonance frequency and acquires a detection signal from the detection structure indicative of a detected angular velocity. When the gyroscope device is powered, the integrated electronic circuit implements a start-up phase, following a previous power-down, wherein the mobile mass is biased to have an increase in the oscillation up to a target oscillation amplitude, followed by a maintenance phase at the target oscillation amplitude. The integrated electronic circuit is provided with a time counter stage for measuring a duration of a time interval from the previous power-down and adjusts the bias of the mobile mass during the start-up phase as a function of the measured duration of the time interval.