White paper compares open-loop and closed-loop stepper control

22 March 2016

Mclennan Servo Supplies Ltdvisit website


White paper compares open-loop and closed-loop stepper controlApplied Motion Products Inc (AMP), represented by Mclennan, has published a new white paper on its innovative StepSERVO closed-loop stepper technology that is available in a wide range of competitively priced 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 free 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 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.

Cost comparison

Also covered are noise level reduction and 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 70V DC with a smaller NEMA size 11 on 30V DC. The all-in-one economic product 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 are also available on some models.

The Step-Servo closed-loop capability provides high-accuracy control of position and velocity for demanding applications with robust servo loops that tolerate wide fluctuations in load inertia and frictional loading. Highly precise positioning to within +/- one encoder count is achievable. Using a high-resolution encoder (20,000 counts/rev), this equates to 0.018deg. 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 per cent 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 per cent more torque for fast dynamic response – which is very useful for short and quick moves.

Follow the link to download a free copy of the white paper about StepSERVO closed-loop stepper technology.

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