Linear Motion

Electric motors are generally rotating machines.  And over the roughly 100 years of electric motor history, incredible effort has been put into adapting the technology to do an almost infiinite array of tasks.  Which is why it’s kind of ironic that in the industrial world, a significant number of applications require the conversion of rotary motion to linear motion.  And, as with all things mechatronic, there are a variety of ways to solve the problem.

Most often, the first order of business is to couple the motor to a linear mechanism.  The two most common are screw type actuators and belt drives.  Both work well, both have relative strengths and weaknesses.  Screws are very smooth and provide mechanical advantage like a gear reducer, but can add inertia mass and have acceleration limits.  Belts are low mass and high speed but a stiff support system to permit proper tensioning.

Linear motion is generally about position, which is fundamentally a different behavior for electric motors. Most motors rotate at high speed, like an 1800 rpm ac motor.  So positioning implies a whole range of properties that are not easily achieved.  While we have achieved a wide variety of solutions for positioning, they are generally much more expensive and complex.  Stepping motors are the  only branch of electric motor technology where position is an inherent aspect of the motor’s operation.  And this fact has made them very popular, especially when linear motion is required.  A typical stepping motor solution is based on a 200 step per revolution motor and a 5:1 pitch lead screw.  This makes the linear motion .001″ of travel per step.  Simple, cost effective.

In many linear motion applications the top priority to is accuracy.  And when the accuracy requirement is higher precision than .001″ or the speeds required are beyond what stepping motors can produce, then other options must be explored.

Linear motors are outstanding in overall performance.  Acceleration, speed and accuracy are excellent and are the way to go where the costs are acceptable.  They use high resolution (generally millionths of an inch) tape scale linear position feedback to achieve the precise positioning required by semiconductor applications.  And this was the early field of use of linear motors.  Once considered an “exotic” solution and very expensive and difficult to apply, the last few years have seen cost improvement and a wider range of applications for the technology.

An emerging technology for linear motion is the piezoelectric motor.  Linear piezoelectric motors are available from a few suppliers and the simplicity and cost effective of this solution is making them an excellent choice for some linear motion requirements.

Most mechatronic solutions for linear motion depend on a feedback sensor to achieve position accuracy.  This makes the linear position sensor a critical component in the design of linear motion systems which I will address in the next post.  There are a number of options and some new technologies available to give designers more choices.

ARC Identifies HMI Software Market Drivers

The worldwide Human Machine Interface (HMI) software and services market, which totaled over $926 million in 2007, will reach over $1,430 billion in 2012, outperforming the industrial automation market overall and growing at a compounded annual growth rate of over 9.1 percent over the next five years, according to a new ARC Advisory Group study.

HMI software suppliers had their best regional development in Asia.  However, North America and EMEA also experienced strong growth. The market growth was led by services and supervisory software. “HMI software suppliers are continuing to add services at an accelerated rate, driven by the end users’ and OEMs’ need for technical support, because manufacturers no longer have the personnel internally to provide the services,” according to ARC Research Director Craig Resnick, the principal author of ARC’s “Human Machine Interface Software Worldwide Outlook”. “Also, Supervisory HMI software, which is used to support HMI software functionality, such as configuration, runtime, connectivity, control, and alarm management, had the fastest growth of any HMI software type. Growth in this segment indicates how HMI software suppliers are expanding their application space and it represents the direction that the HMI software market is heading over the next five years.”

Source: ARC

Use of Interns Rise in Automation, Controls, and Instrumentation Fields

 

The Fabricators & Manufacturers Association, International (FMA) conducted a recent survey that reported that one of biggest challenges facing manufacturers is the dwindling supply of skilled workers, cited by approximately 40 percent of those polled. The finding was corroborated by a Manpower Inc. survey on the 10 most difficult jobs to fill. The poll found engineers, machinists, and skilled trade workers are the most challenging positions to fill in 2008.

One resolution to the shortages, and to attract the next generation of workers, is the traditional concept of apprenticeship and internship. Their value has never been so significant; young people are exposed to challenging opportunities in manufacturing and employers can recruit, evaluate, and hire needed employees.

Some employers encourage apprenticeships to encourage prospective employees and young people to enter the field. Others issue signing bonuses and incentives to skilled workers trained in apprenticeship programs.

 

Source: Control Engineering

New Bosch Rexroth Facility Opens

Federal, state, and local government officials joined global factory automation supplier Bosch Rexroth in celebrating the opening of its new Tech Center East in Rochester Hills, Minn. At the opening, the company displayed state-of-the-art drive, motion and control concepts, and systems developed at the center, including hydraulic hybrid technology and automotive industry applications.
 
The facility will house 120 workers and bring together technical personnel from the company’s hydraulics, pneumatics, electric drives, and linear motion and assembly technologies groups.Tech Center East is deeply involved in the development of the hydraulic hybrid systems that are being tested to conserve energy and reduce the environmental impact of vehicles. The facility plays a major role in the development of Bosch Rexroth’s hydraulic regenerative braking system and innovative automation solutions for solar applications. It will focus on the most advanced hydraulics applications like hydraulic hybrid vehicle technology, compact construction machinery, hybrid hydraulic drives, alternate energy, and off-shore marine applications.

 

Source: ThomasNet.Com