Microchip: Inductive position sensors measure movements

Controlling an earthmoving machine to perform a task requires knowing exactly where its bucket or blade contacts the dirt. Therefore, in addition to knowing the machine’s position, it is necessary to model, in real-time, the rotation at each pivot point and apply some mathematics and trigonometry.

Microchip makes an integrated circuit, known as an inductive position sensor, that is very well suited for machine control because it is not affected by the harsh conditions on most construction sites — temperature extremes, water, dust and dirt — and the vibrations caused by the machine itself. Additionally, it is not affected by the stray magnetic fields generated by electric motors, which are increasingly common on those machines.

Inductive position sensors are used in many automotive systems. (Photo: Microchip)

“We use our inductive position sensing to measure the angle or the linear movement of some sort of target to get a machine to perform its task,” said Mark Smith, product line manager for many different mixed signal products at Microchip. “For example, to control a blade on an earthmoving machine to do something, you need to have feedback about its current angle.”

Microchip also makes sensors for human interfaces, such as accelerator pedals in cars, which no longer have cables that run up to the motor. “Any sort of movement, such as the angles of rotation of a robotic arm, must be monitored and measured. Inductive position sensing is one of the up-and-coming ways to do it,” said Smith.

To direct a task, a central processing unit must then analyze and integrate the data from the sensors. For that, Microchip makes many types of computing elements — including mini-computers and microcontrollers.

“One of the things that’s coming up with many of these vehicles is ambient magnetic noise in the system,” said Smith, “because you’re next to electric motors these days. You want sensors that are immune to stray magnetic fields. We started with automotive, but we’re also seeing it now in industrial environments, including earthmoving vehicles.” Inductive position sensors, Smith said, are simpler, cheaper, lighter, and better able to withstand extreme temperatures than what they are replacing. “Also, because they are non-contact, the circuit board can be environmentally protected.”

Vibrations also are a concern. “There is an air gap between the target and the sensor itself,” Smith said. “We have an automatic gain control at the sensing side that is constantly adjusting the gain to get the maximum signal strength. This is a fast-moving control algorithm that can adjust the gain to ensure that the vibration does not affect the performance. When everything is operating at its maximum torque, this starts to matter.”