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Monday - August 16, 2021

Custom Linear Stepping Motors for Adaptive Headlights

Adaptive headlights make nighttime driving safer by throwing light where the driver needs it. For maximum effectiveness they must move quickly, precisely and repeatably, and that’s where stepper motors come in.

A stepper motor, or stepping motor, (the terms are used interchangeably,) provides precise rotation that can be used to drive linear motion. NMB Technologies produces stepping motor packages and can customize their control systems to give the precision and response needed in every application. Here’s an introduction to linear stepping motors and an explanation of how they help improve road safety.

One Axis or Two

Imagine cresting a hill late at night. Your car’s headlights are pointing into space while what you want to see is where the road goes. A linear stepper motor integrated with the headlamp package for up-down motion, (what’s called, “leveling”), would quickly lower the beam to help.

Or consider this scenario: it’s dark and you’re taking a sweeping corner on an unlit road. Again, your headlights don’t point where you need them. In this case, stepper motors providing left-right movement, (“bending”), would pull the beams round so they light the road and not the trees or hedgerows.

Linear Stepping Motor Technology

In a stepper motor electromagnets arranged in a fixed ring interact with permanent magnets mounted in a central rotor. Switching the outer magnets on and off generates attractive and repulsive forces that make the rotor “step” around.

At the center of the motor, and mounted co-axially, there’s a threaded nut. One end of a rod is screwed into the nut and the other end is attached to the headlight pivot mechanism. As alternating magnetic fields turn the rotor the rod moves in or out to change the headlamp angle. The term “linear” refers to the linear relationship between motor rotation and axial movement of the rod.

 

Switching is performed by an electronic driver that responds to inputs from a controller. In essence, the controller decides the number of steps needed and their direction, and the driver switches the current to the electromagnets in the sequence and at the rate needed.

A particular feature of the permanent magnet stepping motor is its ability to hold a fixed position. If the magnetic field doesn’t change the motor won’t turn. In fact holding torque can be surprisingly high. And when it does turn a permanent magnet stepper motor generates more torque for its size than other motor designs can achieve.

When in motion the permanent magnet stepper motor is fast-acting, precise and very repeatable. At the same time, it’s design avoids the cost and complexity of closed-loop feedback systems.

Controller and Driver Customization

The motor controller needs inputs that let it determine how the headlights should be moved. NMB Technologies can customize this controller to handle the specified inputs and the outputs required. Braking, acceleration and steering angle are just three examples.

Likewise, NMB Technologies can tailor driver characteristics to give exactly the movement required. Motor acceleration, peak velocity and dwell times for example.

Data moves through the linear stepper motor on the Local Interconnect Network (LIN) communication bus using a custom ASIC. This too is readily customized to meet specific requirements. In short, NMB Technologies can create a smart headlamp actuator uniquely tailored to the needs of each vehicle platform.

Helping Keep Drivers Safe

Driving safely at night depends on being able to see what’s ahead and where the road leads. Adaptive headlights let drivers see further down the road, and that gives them more time to react to hazards.

The key to this improvement in automotive safety is the headlamp actuation mechanism. Linear stepping motor technology is fast-acting and dependable, and NMB Technologies can customize systems to give exactly the response and performance desired. Contact us to learn more.

Kotaro Torii
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