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Welcome to Kollmorgen's Blog in Motion. We have been adding information and knowledge to the great web based world for many years - through white papers, technical documents, and even webinars. Kollmorgen enjoys sharing our knowledge with you, as well as identifying other motion related tidbits through our Twitter, Facebook, LinkedIn and YouTube feeds. Our newest source is Blog in Motion, covering a wide range of topics, as well as some interesting contributing authors with lots of Motion experience. If Motion Matters to you, stop by, follow, like, and sign up so you can stay tuned for what Kollmorgen has in store for you!
This blog was originally posted back on June 18, 2012 - I wanted to update this with some new activities regarding our work with Universities since that date...
There has been a long standing cooperation between Industry and Academics throughout the recent centuries. Just look at the companies that pop up near Universities - like the Route 128 corridor near MIT, or Silicon Valley's influence by Stanford, UCB and UCSF. Every major research university houses a "technology park" filled with start-ups incubating their new ideas and inventions. But it's not just the entrepreneurs that latch on to collaboration with academics. Established firms also find it beneficial to work with universities on various projects of interest, especially where an emerging industry may be getting ready to take off.
Among the simplest and least expensive feedback devices are Hall-effect sensors. These are digital on-off devices that detect the presence of magnetic fields. Made of semiconductor material, they are rugged, can be operated at very high frequencies (equating to tens of thousands of motor rpm), and are commonly used to provide six-step commutation of brushless motors.
Most machine builders are familiar with modern touch screen HMI's. They have all but replaced older style toggle switch panels. It has also enabled machine builders give operators much more information on the process going on in a machine. HMI's can look at a multitude of machine variables and they can be presented in a more relatable graphical format than digital readout or analog meters. For instance, instead of a tank volume number, you visually show the operator much fluid is in the tank. HMI's however can go even beyond these operator related touch-screen graphics. Some of the more sophisticated features can really benefit machine builders and end-users of machines. Here are a few capabilities you might not have known about modern HMI's.
There are a number of situations that call for crossing
over and replacing an existing motor with a newer servo. These can include:
product obsolescence, cost savings, lead time issues, or upgrading to newer technology.
The specifics of each application could lead to an endless number of important
factors to consider. In this post I will try to (briefly) identify those that
are most common and their correct order of concern.
Do you remember the 1966 movie Fantastic Voyage? What about Innerspace? Both of these movies feature stories about a small vessel working inside of the human body. At the time these movies seemed impossible because there were microscopic humans operating the ships. Of course now it is 2014 and surely you've heard of Arthroscopy. In my last blog post, I discussed drive-by-wire in a car. Essentially, the mechanical linkage between you and the steering wheel clutched in your white-knuckled fists is going away-replaced by sensors on the steering wheel that tell an actuator motor which way, how hard, and how far to turn the car's wheels based on how far and how hard you are turning the steering wheel.
Machine builders focus on functionality and reliability when first designing a new machine. Ideas are put on paper and components are strung together in block diagrams with thin lines to show the association of all the pieces. It is the most creative time in the cycle. Things can be moved and shifted with ease because everything is on a whiteboard. Even if you are far enough in the cycle to work in a CAD model, changes require no physical effort and the task of putting it together is still just an idea.
Coating and lamination applications demand
precise speed regulation in order to avoid velocity ripple that causes uneven
coating and undesirable horizontal bars across the substrate. The key to
achieving the most uniform coating is minimizing the variations in velocity as
well as in metering of the coating material.
A specification will often state the required stroke for the application. What is frequently seen is that units are damaged by not following a simple requirement stated in the Installation Manual. Best practices dictate the utilization of End of Travel (EOT) sensors used with actuators and drives. This is done to prevent the actuators from striking the mechanical stops at each end, and typically a manual will clearly show where these sensors should be placed on the device. Actuators do have built in "bumpers" to help absorb energy when the mechanical stops are struck, but they are not designed to provide unlimited protection against repeated strikes.
Frequently, servo motors are returned where the brakes are worn. This is almost always due to the brake being applied repeatedly while the motor/load is moving. The application of a motor brake in a "dynamic / moving" scenario will result in dramatic wear of the brake mechanism.
Cogging and Torque Ripple questions are common and many times, difficult to answer.
Cogging torque is defined as the attraction/interaction of the magnetic poles to the teeth (steel structure) of the laminations within an un-energized motor.
Torque ripple is defined as the variance of the torque of the energized motor with a constant current. They are related in position independent of magnitude or direction, but cogging torque is generally not presented as a specification for servo motors.
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