Our E3K IMU Sensor is a 9 DOF inertial measurement unit based on Hillcrestlabs’ BNO085. The sensor integrates a triaxial accelerometer, triaxial gyroscope, magnetometer, and a 32-bit ARM® Cortex™-M0+ microcontroller. The firmware of the sensor includes Hillcrestlabs’ MotionEngine software, which pre-processes the data. The sensor can be programmed to output individual sensor data or a rotation vector (quaternion data). The sensor supports three communication protocols, namely, I2C, SPI and UART, for which breakout pins are provided on the board. Two QWIIC connectors are also provided, which can be used to connect multiple IMUs with the E3K DCPU.

What is an IMU?

An inertial measurement unit (IMU) is used to measure specific force, angular rate and orientation of the body. The IMUs can have 6 Degrees of Freedom (DOF) containing 3 axis accelerometer and 3 axis gyroscope or 9 DoF containing an extra magnetometer. Usually, we combine the data collected from these individual sensors and calculate rotation along 3 orthogonal axes, commonly named as pitch, roll and yaw. An IMU has a wide range of applications especially in Inertial navigation systems for mobile robots: like unmanned aerial or ground vehicles, satellites etc. IMUs are also used in smartphones and Virtual Reality headsets in order to detect heading and adjust the virtual environment accordingly.

Project Aim

Another application of IMU is motion tracking of the human body. The IMUs can be used to provide feedback to exoskeletons or quantity limb motion during a physical therapy session.

With the following example, we will use the E3K IMU sensor to detect motion of the wrist with respect to the forearm.

Add Connection diagram image

Procedure:

1. The E3K IMU sensor can communicate via I2C, SPI or UART. The sensor can be easily connected to E3K DCPU for communication via I2C as shown in the figure above.
2. Configure the sensor to output rotation vectors (quaternion data).
3. Send the data to the PC where a 3D model of a a forearm and fist will move according to the motion of the sensor.
4. Further, E3K IMU comes with qwiick connector so you can attach multiple IMUs on each of the limbs in order to track whole-body movement.

Expanded example: By combining the E3K EMG sensor with an IMU sensor, you can make a health monitoring device and track the efficiency of exercise, physiotherapy sessions and much more.

References

• https://en.wikipedia.org/wiki/Inertial_measurement_unit
• http://www.chrobotics.com/library/understanding-quaternions
• https://en.wikipedia.org/wiki/Conversion_between_quaternions_and_Euler_angles