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Comparing open loop and closed loop stepper systems

24 March 2016

Applied Motion Products (AMP), represented by Mclennan, has released a new white paper on its StepSERVO closed-loop stepper technology.

The technology is available in a wide range of integrated motors that combine NEMA 11, 17, 23 and 24 sized microstepping motors and drives with a feedback encoders and motion controllers and optional fieldbus communications. 

The 12-page resource, available as a download from Mclennan’s website, compares the technology with open loop stepper systems and demonstrates its capability for higher acceleration, faster machine cycles and greater productivity as well improved energy efficiency and quieter operation. 

The white paper, authored by Jeff Kordik, AMP’s CTO, principally poses the question - ‘What if…you could make a step motor faster? And quieter? While saving energy?’; and goes on to explore the benefits of StepSERVO by way of fully tested comparative torque curves, move profile and throughput rate graphs as well as motor heating, power consumption and positional accuracy illustrations. Also covered are noise level reduction as well as the all-important cost comparison between AMP’s technology and traditional open loop steppers. The comparison concludes that the StepSERVO is slightly more expensive, mainly due to the addition of the high resolution 20,000 count/rev encoder but this is more than made up by the benefits of higher performance and more efficient operation.

AMP’s StepSERVO series integrated motors are offered in three product types that operate on 70VDC with a smaller NEMA size 11 on 30VDC. The all-in-one economic solution has multi-function control capability that includes individual pulse or analogue control (for example from third party controllers), as well as a choice of built-in Modbus/RTU or CANopen multi-axis networking, or for pre-programmed stand-alone operation using AMP’s ‘Q’ motion software. EtherNet and EtherNet/IP is also available on some models.

The Step-Servo closed loop capability provides high accuracy position and velocity control for the most demanding applications with robust servo loops that tolerate wide fluctuation in load inertia and frictional loading. Highly precise positioning to within +/- one encoder count is achievable. Using a high resolution 20,000 counts/rev encoder, this equates to 0.018°. Highly developed servo control algorithms ensure the drive stage uses only the current required by the application for maximum efficiency. At stand-still, the current can reach almost zero for extremely low heat operation and because the StepSERVO operates in full servo mode, all the available torque can be used to provide as much as 50 percent more torque in many applications, often eliminating the need for gear reduction. A torque boost function is also available to deliver as much as 50 percent more torque for fast dynamic response – perfect for short and quick moves.

To read the whitepaper click here


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