Aerodynamic control of a delta-wing using MEMS sensors and actuators

The Caltech Micromachining Lab has been developing fluid-mechanics MEMS for many years. What is presented here are two basic devices and their applications for delta-wing control. The first device is a surface shear-stress sensor that is small, sensitive, fast and arrayable. The device has a structure of a polysilicon resistor on a 1.2 μm thick silicon-nitride diaphragm (200×200 μm²) which is on top of a vacuum cavity. The device has a shear-stress sensitivity of 120 mV/Pa and a constant-temperature bandwidth of 10 kHz at a power of 5 mW. The second device is an electromagnetic flap that is strong, fast and also arrayable. The actuator has a flap structure hinged with silicon-nitride beams and the flap size is either 1×1 mm² or 2×2 mm². The actuators can provide an out-of-plane motion with an actuating torque resulting from an on-flap magnetic moment (from permalloy and/or electrical coils) interacting with an external magnetic field. The out-of-plane force from the flap can be as high as 100 μN and the flap rotational angle up to 80°. In the delta-wing control project, an array of shear-stress sensors are made on a flexible skin and used at the leading edge of the wing to detect flow separation. Then, an array of microactuators are placed right in front of the separation to produce maximum control moments. To date, a rolling moment of 50% that of the lifting torque has been produced using MEMS devices. This result has proven the feasibility of an aircraft controlled by microactuators