A micro-platform with integrated multi-axis actuation and position sensing capabilities for in-situ calibration of long-term scale-factor drifts in the output signals of micromachined inertial measurement units, has been developed at the University of Michigan. The use of micromachined inertial measurement units, such as MEMS accelerometers and gyroscopes, in high accuracy strategic and navigation applications is limited by long-term drifts in their scale-factor(gain) and bias. The in-situ microplatform designed at the University of Michigan aims to overcome the challenges associated with calibrating such scale-factor drifts.
The proposed in-situ calibration platform consists of a piezoelectric actuation stage that provides periodic vibratory excitations as reference stimuli for calibration of inertial sensors. The piezoelectric stage also compensates for any undesired off-axis motion due to environmental vibration or any misalignment and process tolerance during fabrication. Capacitive sensors integrated into the micro-platform precisely determine the applied physical stimulus. For high accuracy detection of the applied rate, the electrodes of the capacitive sensors are arranged in a specific geometry to provide a combination of analog and threshold position sensing outputs. In addition to analog and threshold capacitive sensors, piezoelectric signals from the actuator legs can also be used to improve the sensing precision. Further, a feedback control system with a variation of the Kalman filter is used to improve position estimation.
When the platform is not being used for calibration, the capacitive sensing electrodes can be utilized for electrostatic pull-down and position lock-down of the motion-stage to protect against environmental vibration and shocks. Since the calibration platform can be operated along multiple axes, it can be integrated with, and test, a multi-axis inertial sensing unit (IMU) within the same device package. Further, the system can be utilized to investigate the effect of cross-axis coupling, excitation frequency, and linear acceleration on the output of a gyroscope. Overall, the system demonstrates low power consumption, provides a simple electrical signal transfer interface, and provides dithering actuation ranges in multiple degrees-of-freedom in a single, compact device.
- On-chip physical stimuli to MEMS inertial sensors for on-chip scale factor calibration
- MEMS inertial sensor operation in mechanically harsh environments
- Micro-gripper manipulation in micro robotics and assembly
- Vibration damping for image stabilization
- Disk-drive protection
- Probe-based microscopy
- Optical steering of laser beams for projection displays
- Endoscopic image acquisition
- Low power consumption
- Simple electrical transfer interface
- Single-device design
- Low area overhead