TheCircuit

Have You Yet Reconsidered Your Motion Control?

What was Tesla’s birthday again? Are you going for your encyclopedia, are you asking Wikipedia now? Years ago this wasn't even a question.

Do you remember this myth - Bill Gates stated 640k would forever be a sufficient size of memory? Did he really say that? Give it a try and ask your paper lexicon… But this legend is describing very well, that it's sometimes hard to look ahead. And sometimes it's even harder to keep track of the current status of technological evolution.

Once somebody said during a short talk on an exhibition: "Stepper motors will always sound and feel like a worn out adult toy" and went away. Today, a tiny piece of silicon will decide on its own whether it's better to run PWM stealth mode or high-resolution micro-stepping, or if velocities are too high and a full-step mode is more suitable in order to allow a smooth and reliable run.

(Image source: Trinamic Motion Control)

Times change, technology changes even faster.

Things we can't imagine one day are a reality the next. And sometimes this may hit us on a personal level. We love to stick to things we know and that we are good at and train it to excellence. A diesel engine engineer is probably convinced of all advantages of this type of engine and will fight for a future with diesel engines in it. Advocates of hydrogen propulsion or electric drives might have a different point of view.

However, the best of us engineers drive technologies to the edge of the possible, or legal - with incredible results. Tomorrow, or next week, the excellence may fall behind the curtain of time.

Now, we could feel scared or cheated for our efforts and successes. We may doubt, or even fight, new developments. But…

Can we stop technical evolution?

Hopefully not!

So, what if we, instead of looking for points against new technologies, keep up and make use of it? Selfishly. Clinical. Open-minded.

Is this really solved?

Why should we put effort into something that's already solved? Okay, there are some obvious reasons. Perhaps we can do better or the solution is not fitting. However, we should do ourselves a favor and check if this thinking is still valid. There are so many dedicated, reliable, and powerful solutions for all kinds of technical matters available that we can make use of.

Examples from Trinamic’s motion control world: Integrated motion controllers will stoically generate smooth velocity profiles.

Fast and proven FOC controls in silicon are transferring this digital velocity information into a physical movement of a motor. All we have to do is to send one command via software. It requires no additional coding to make these complex algorithms happen that are necessary in order to run a system with today’s requirements.

(Image source: Trinamic Motion Control)

These reliable items might give you extra time to focus on getting the best out of your application. This gives us the freedom to take the next steps and do what has never been done before.

Am I on the right track?

Stepper motors are inefficient. Effective brushless DC (BLDC) motor control is expensive. DC motors are cheap and simple. True?

Nowadays stepper motors may be easily controlled using a closed loop. A stepper-optimized closed-loop algorithm allows you, compared to a conventional field oriented control (FOC), to use all stepper-motor advantages for low speeds especially in complete standstill. Starting at low RPM, the stepper will serve high torque without the need for a gearbox. An optimized current controller ensures a smooth as well as resonance-free and efficient running.

(Image source: Trinamic Motion Control)

In addition, closing the loop enables a highly dynamic behavior with the most efficient limits. With a low-cost magnetic encoder, we can establish a stepper servo behavior in order to easily run a standard and cost-efficient hybrid stepper with several thousand RPMs. A dedicated motion controller chip might take care of the closed-loop control and handle dynamics without the risk of losing steps or the need for time-consuming software development.

Are several thousand RPMs not enough? This sounds like an application for a BLDC drive. Cascaded control loops for position, velocity, and current are the absolute standard. All necessary algorithms are known very well. So why not integrate such a high performance cascaded FOC controller in a chip to increase reliability and performance over expensive software? Integrated FOC controllers, with their up to 200 kHz adjustable current control cycle, are the perfect ready-to-go controllers for any BLDC motor application and probably the best solution for ultra-low inductance drives.

(Image source: Trinamic Motion Control)

(Image source: CyberTech Media)

Whatever the mechanical performance envelope an electrical motor is capable of, it requires leading edge electronic controllers, which are capable of achieving given constraints on drive current and voltage.

Do you remember how DSL changed the concept of the bandwidth of telephone lines?  These used to be voice grade bandwidths.  Now, on the very same wires, they carry hundreds of megabits per second.

More features, more performance, but is it worth it?

The good thing about new technological developments is they don’t cost more. Ongoing optimizations and integration allow lower cost and fewer additional parts. This may reduce the BOM further, saving both space and money. The democratization of technology seems unstoppable.

However, if our performance-wise preferred solution is not the most cost-efficient we might need to explain ourselves. And the only question is:

Will this technology enhance my application in a relevant way?

If the answer is yes, it is unadvisable to fight for anything less than the best solution.

 

About the Author

Image of Thomas Ernst

Thomas Ernst, Field Applications Engineer based at TRINAMIC Motion Control’s headquarter in Hamburg, Germany, is responsible for supporting customers both remotely and on-site. After joining Trinamic in 2013, he developed the concept of the Evaluation System and continues to develop the hardware and software of the modular Evaluation System known as the Landungsbrücke and Eselsbrücke. Besides that, Thomas takes a particular interest in research projects by institutes and universities, offering technical support and consulting whenever he can.

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