A yaw-rate sensor is a

gyroscopic A gyroscope (from Ancient Greek γῦρος ''gŷros'', "round" and σκοπέω ''skopéō'', "to look") is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rot ...

device that measures a vehicle's yaw rate, its angular velocity around its vertical axis. The angle between the vehicle's

heading Heading can refer to: * Heading (metalworking), a process which incorporates the extruding and upsetting processes * Headline, text at the top of a newspaper article * Heading (navigation), the direction a person or vehicle is facing, usually s ...

and

velocity Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity i ...

is called its

slip angle In vehicle dynamics, slip angle or sideslip angle is the angle between the direction in which a wheel is pointing and the direction in which it is actually traveling (i.e., the angle between the forward velocity vector v_x and the vector su ...

, which is related to the yaw rate.

Types

There are two types of yaw-rate sensors: the

piezoelectric Piezoelectricity (, ) is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied mechanical stress. The word '' ...

type and the micromechanical type. In the piezoelectric type, the sensor is a "

tuning fork A tuning fork is an acoustic resonator in the form of a two-pronged fork with the prongs ( tines) formed from a U-shaped bar of elastic metal (usually steel). It resonates at a specific constant pitch when set vibrating by striking it agains ...

"-shaped structure with four piezoelectric elements, two on top and two below. When the slip angle is zero (i.e., no slip), the upper elements produce no voltage as no Coriolis force acts on them. But when cornering, the rotational movement causes the upper part of the tuning fork to leave the oscillatory plane, creating an alternating

voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to ...

(and thus an

alternating current Alternating current (AC) is an electric current which periodically reverses direction and changes its magnitude continuously with time in contrast to direct current (DC) which flows only in one direction. Alternating current is the form in whic ...

) proportional to the yaw rate and oscillatory speed. The output signal's sign depends on the direction of rotation. In the micromechanical type, the Coriolis acceleration is measured by a micromechanical capacitive acceleration sensor placed on an oscillating element. This acceleration is proportional to the product of the yaw rate and oscillatory velocity, the latter of which is maintained electronically at a constant value.

Applications

Yaw rate sensors are used in aircraft and electronic stability control systems in cars.

Types

Applications

See also