Page 82 - Handbook of Biomechatronics

Sensors and Transducers 77

through displacement using a capacitor sensor element. The displacement
measured through capacitance can be used to derive the acceleration
(ElProCus, n.d.).

4.4 Inclinometer
Inclinometers measure the angle of an object, or inclination with respect to
gravity. MEMS inclinometers consist of a MEMS accelerometer which is
small enough and sensitive enough to measure the change in the pull of
gravity of a mass based on the orientation of the sensor (Omega—
Accelerometers, n.d.).

4.5 Gyroscope

A MEMS gyroscope measures the angular velocity from the effect of the
Coriolis force applied to a vibrating element. The gyroscope has two vibrat-
ing legs and two sensing legs (Fig. 19). When the gyroscope is rotated, the
resultant Coriolis force causes an unbalanced force in the vibrating legs
which gets transmitted to the sensing legs. The motion of the sensing legs
is measured through a capacitance element (https://www.posital.com/
en/products/inclinometers/mems/MEMS-Technology.php, Accessed 22
August 2017).
You select an accelerometer, inclinometer, and gyroscope and design
them into the foot of Jacob’s prosthesis. From the accelerometer, you are
able to determine when the foot is moving and when it is stationary. From
the inclinometer, you can determine what type of terrain Jacob is traversing,
flat, downhill, or uphill. From the gyroscope, you can determine the foot
stability.
Based on the information from these three sensors, you develop an algo-
rithm which determines if Jacob is in the swing (foot not on the ground) or

Fig. 19 Schematic representation of a MEMS gyroscope. When not rotating, there is
constant capacitance measured across the top and bottom legs (left). When rotating,
the Coriolis effect causes the top and bottom legs to vibrate, varying the capacitance
distance on the top and bottom legs (right).