MEMS Gyroscope Time-Multiplexed Force Feedback
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Solution Overview
Problem
Existing closed-loop-force-feedback architectures for MEMS gyroscopes require high power consumption due to the need for high voltage drivers, and they lack stability due to environmental factors like temperature and strain, as well as aging, and do not allow for mode matching of drive and sense resonators or flexible calibration of bias and sensitivity.
Innovation Solution
A stable closed-loop-force-feedback architecture is developed using time-interleaving techniques where sense electrodes are used for both actuation and sensing, with time multiplexing to determine and apply charges to capacitive elements, allowing the proof mass to return to its initial position, reducing power consumption and enabling mode matching and flexible calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If closed-loop-force-feedback architecture is used to stabilize gyroscope operation, then stability is improved, but power consumption increases due to high voltage drivers
Solution Approach 1:
The patent implements periodic action by time-multiplexing the sense electrodes between sensing mode and actuation mode. The sense electrodes are activated periodically to sense proof mass position, then used periodically to apply feedback force, rather than continuously operating at high power. This periodic switching enables closed-loop stabilization while significantly reducing average power consumption compared to continuous high voltage driving.
Solution Approach 2:
The patent applies multi-functionality by making the sense electrodes serve dual purposes: first as sensing elements to detect proof mass displacement, then as actuation elements to apply feedback force. This universal use of the same electrodes for both sensing and actuation eliminates the need for separate high-power drive electrodes, thereby reducing overall power consumption while maintaining stability.
2Reliability
If traditional closed-loop architecture is used, then stability is improved, but device complexity increases due to separate drive and sense resonators
Solution Approach 1:
The patent merges the drive and sense resonators into a single integrated resonator structure. The sense electrodes are positioned to sense proof mass displacement, and the same electrodes are used to apply feedback force, combining what were traditionally separate drive and sense functions into one unified resonator system. This merging reduces device complexity while maintaining the stability benefits of closed-loop architecture.
Solution Approach 2:
The patent makes the sense electrodes universal by using them for both sensing and actuation functions. The electrodes first sense the proof mass position during the sensing phase, then apply the feedback force during the actuation phase. This multi-functional use eliminates the need for separate drive electrodes, simplifying the overall device structure while preserving stability.
3Use of energy by moving object
If sense electrodes are used for both actuation and sensing with time multiplexing, then power consumption is reduced, but measurement precision may be affected
Solution Approach 1:
The patent maintains measurement precision through periodic action by implementing well-defined sensing and actuation phases. During the sensing phase, the sense electrodes are activated to accurately measure proof mass position before any feedback force is applied. This temporal separation ensures that sensing occurs in a clean state, preserving measurement precision while enabling power reduction during the subsequent actuation phase.
Solution Approach 2:
The patent applies preliminary action by completing the sensing measurement before applying the feedback force. The sense electrodes first sense the proof mass position during the sensing phase, and only after this preliminary measurement is complete does the system apply the feedback force during the actuation phase. This sequencing ensures that the sensing operation is not interfered with by the feedback actuation, maintaining precision.
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
This approach stabilizes the gyroscope operation while minimizing power consumption, allowing for flexible calibration and mode matching of resonators, thereby improving the system's stability and efficiency.
Implementation Method 1
The capacitive elements are configured to change capacitive charge stored thereon in response to the proof mass moving from the first position to the second position
Implementation Method 2
The electrode circuitry applies the charge received from the force feedback circuitry to the capacitive elements to move the proof mass from the second position to another position
Implementation Method 3
The proof mass is configured to move from a first position to a second position in response to application of an external actuation, e.g., force, rotation, etc.
Data Source
AI summary
A device includes a proof mass of a sensor, capacitive elements, an electrode circuitry, a time multiplexing circuitry, a sense circuitry, and a force feedback circuitry. The proof mass moves from a first position to a second position responsive to an external actuation. The capacitive elements change capacitive charge in response thereto. The electrode circuitry coupled to the capacitive elements generates a charge signal. The time multiplexing circuitry pass the charge signal during a sensing time period and prevents the charge signal from passing through during a forcing time period. The sense circuitry generates a sensed signal from the charge signal. The force feedback circuitry applies a charge associated with the sensed signal to the electrode circuitry during the forcing time period. The electrode circuitry applies the charge received from the force feedback circuitry to the capacitive elements, moving the proof mass from the second position to another position.