Modeling A Double-Tuning-Fork MEMS Gyroscope
When most people think of a tuning fork, music involves thoughts, since the device’s resonant frequency is used to tune devices. As a MEMS practitioner, you’re extra probably to consider a miniature gyroscope that can be formed by joining two tuning fork constructions. Mass-produced MEMS gyroscopes provide reasonably priced choices for measuring angular velocity in functions akin to yaw-fee sensors for skid control in car techniques. We can take a look at these designs and optimize their setup for mechanical programs using simulation.
The MEMS Gyroscope
The MEMS system below consideration is essentially made up of two tuning forks working collectively to act as a fee gyroscope. These two parts are composed of piezoelectric materials. In the case of the mannequin discussed here, the material is quartz.
A rate gyroscope senses the rotational movement and angular velocity of a system. On this piezoelectric price gyroscope, the tuning forks’ resonant modes are used to produce the measurement signal.
Two resonant modes are used:
1. Drive mode 2. Sense mode
These two modes serve because the driving and sensing facets of the gyroscope. In operation, the tuning fork is driven at the resonant frequency of the drive mode through an electric discipline applied by electrodes deposited on the surfaces of the drive tines. The drive tines vibrate in the tuning fork plane, the xy-airplane. Within imu ins , the sense tines vibrate out of the tuning fork airplane and alongside the z-axis as an alternative. This displacement is proven within the set of images beneath.
The route of displacement of the tuning fork prongs in drive mode (left) and sense mode (proper).
The out-of-aircraft sense mode movement is caused by the impact of the Coriolis power as the gyroscope rotates around the y-axis. The reverse piezoelectric impact is used to drive the in-aircraft mode, while the out-of-aircraft movement is sensed by the direct piezoelectric impact.
Basically, these completely different components work to help the system detect a skewed orientation in addition to self-appropriate to a stable or balanced orientation. Stability helps to make sure safety and keep away from harm in select mechanical techniques, while achieving correct orientation in others. This ability is the explanation MEMS gyroscopes are utilized in some skid control techniques, in addition to in rollover detection.
Organising the COMSOL Multiphysics® Model
As talked about above, a piezoelectric rate gyroscope senses when a system is rotating. On this model, we simulate how the system operates by a simplified evaluation.
When modeling a piezoelectric charge gyroscope within the COMSOL Multiphysics® software, adding a rotating body of reference accounts for the actual rotating physique with which the machine is mounted. This is completed by including the Rotating Body node. Once you’ve established the properties for the body of reference, you have the option to account for the Coriolis pressure by selecting the respective test field. The Coriolis power causes the tuning fork to vibrate in the out-of-aircraft motion of the sense mode.
The electrodes on the tuning fork have to be patterned in particular methods with respect to the crystalline axes of the device’s piezoelectric material, quartz. That is vital so that the drive tines are bent in the appropriate instructions and the sense signals are remoted and extracted cleanly from the sense tines.
The Electrostatics physics interface gives the drive voltages and picks up the sense voltages via the electrodes. The electrodes create electric fields that drive the in-airplane bending movement of the tuning forks’ tines. Within the sense tines, the electrode sample detects the out-of-aircraft motion of the sense mode. The structural mechanics and electrostatics are coupled by the Piezoelectric Effect multiphysics node.
Tip: When creating your mannequin, it's generally advantageous to initially use a coarser mesh so that you get results quickly. You'll be able to then go back and create a finer mesh to generate extra accurate results. When working with a coarse mesh, it helps to assemble the geometry in a symmetrical fashion and use copy and paste functionalities to assemble a symmetrical mesh, so that the symmetry of the physics is preserved numerically.
Outcomes and Discussion
The results present how much the sense voltage modifications for a given angular velocity as a function of the drive frequency, as nicely as the sense voltage at a hard and fast drive frequency as a perform of the angular velocity.
Left: Sense voltage vs. drive frequency. Right: Sense voltage vs. angular velocity.
Simulation allows you to seek out the optimum design extra efficiently, as you can modify for any goal without the usage of a prototype. With COMSOL Multiphysics, you'll be able to simulate actual-life uses to test particular designs and optimize them for your specific system.