Source : Mouser Electronics

My childhood was a long time ago. No handheld electronics, no video games, no portable devices. Instead, it was a time of Play-Doh, Silly Putty, Magic 8-Ball, Frisbee, and the Slinky. One toy I remember fondly is the Mattel Wiz-z-zer. It is essentially a gyrostat, a rotating wheel inside a case, a toy that introduced the spinning top to modern children (Figure 1). The twist was using a super-spinning, high-tech bearing that allowed the top to spin at a very high speed so it could remain standing for an extended period of time. I can still hear the sound it would make as I revved it up for high-speed spinning before releasing it to spin freely across the floor.

Figure 1: A spinning top. (Source: RODRIGO SAINZ/Shutterstock.com)

This gyrostat top is a modified gyroscope. A gyroscope remains upright while spinning because of the conservation of its angular momentum (Newton (1687), Laplace (1799), Foucault (1852), Rankine (1858), others). Because of this phenomenon, gyroscopes can be employed for measuring or maintaining orientation and angular velocity.

MEMS

Today’s modern electronics designs have adopted this mechanical knowledge and made it into a sensor. Such a sensor can be manufactured by employing microelectromechanical systems (MEMS). MEMS sensor technology enables sensor fusion whereby multiple sensors and software solutions are packaged as an integrated whole. Thus, it helps provide solutions in various large industries, including information and communications technology (ICT), the Internet of Things (IoT), and automotive. The semiconductor manufacturer calibrates these integrated solutions and utilizes embedded compensation and sensor processing, plus a simple programmable interface.

At the forefront of humanizing MEMS sensor technology is TDK InvenSense. InvenSense is part of the Sensor System Business Company within TDK. It is the industry leader in MEMS Motion, Audio, and Pressure Solutions for the consumer, industrial, automotive, and IoT market segments. With a robust portfolio of MEMS 3/6/7/9 axis motion sensors, accompanied by the highest performing MEMS audio microphones and pressure sensors, TDK continues to push the boundaries of performance and quality, setting new standards of innovation across multiple industries. Let’s examine how MEMS inertial measurement units (IMUs) from TDK InvenSense help design engineers keep straight on where things are positioned.

IMUs

MEMS technology allows for multi-axis combinations of precision gyroscopes, accelerometers, magnetometers, and pressure sensors to be assembled into one device. Integrated devices employing these types of sensors are often called inertial measurement units (IMUs). IMUs are electronic devices that measure and report a body’s specific force, angular rate, and often the body’s orientation. Isaac Newton (1642–1726/27) described inertia as the first of the Laws of Motion (Mathematical Principles of Natural Philosophy, 1687) by defining it this way: “Every body perseveres in its state of rest, or of uniform motion in a straight line unless it is compelled to change that state by forces impressed thereon.” MEMS technology reliably senses and processes multiple degrees of freedom (DoF), even in highly complex applications and under dynamic conditions.

Multiple Degrees of Freedom

One vital criterion in IMU selection is the degrees of freedom. IMUs are commonly available with specifications from two to 10 degrees of freedom.

The word freedom means different things in different contexts. In this case, we are not talking about freedom of personal choice or political freedom, but rather in the context of physics, specifically mechanics. In mechanics, degrees of freedom correspond to translation components and rotation that define its configuration or state. For example, for a rigid body in space, both translation and rotation have three components, yielding a total of six degrees of freedom (Figure 2).