DN Staff

June 3, 2009

2 Min Read
Leveraging Adaptive Control

Adaptive control algorithms are continuing to advance the state-of-the-artin digital servo drives. In May, we reported on "ServoDrives Utilizing Adaptive Control for Advanced Algorithms." But now we'refinding additional innovative products that are using real-time autotuning andsophisticated electronic nameplates on motors to extend the performance ofadaptive tuning in servo drives.

TheMR-J3 drive from Mitsubishi Electricuses a combination of a 900Hz frequency response and 18-bit encoder resolutionto implement robust, real-time autotuning.Beyond adaptive tuning, the drives offer other servo tuning features thatsimplify eliminating machine vibrations and resonances.

One control function, Vibration Suppression Tuning, automaticallydetermines vibration suppression parameters and makes it feasible to achieve higherresponse for low stiffness machines. Theamplifier has load model blocks that stimulate a machine structure, and describethe structural relation between the motor and load. The tuning section then estimatesthe frequency of load vibration from the encoder position signal and calculatesthe structural parameters and optimized feedback gains.

"Features like this are possible because ofthe adaptive tuning capabilities in the drive which provides real-time, dynamicautotuning of the system," says Sunny Ainapure, product manager for Servos andMotion at Mitsubishi. He also says an adaptive filter algorithm provides software to deal with machine resonancesthat can be difficult to resolve using traditional architectures.

A RobustDisturbance Compensation algorithm is effective for an axis where the loadinertia is bigger than the motor inertia like the roller axis in a printingpress. Synchronizing the motor that hasa bigger inertia mismatch with smaller motors in the system is often aproblem. The algorithm monitors the lowfrequencies on the machine and matches the gains to what is required for thesmaller size motors, so all three motors can be effectively synchronized.

With new Siemens S110 and S120 drives,adaptive tuning algorithms offer improved performance by incorporating "electronicnameplate" parameters along with factory measurements not typically found on anameplate.

"The DRIVE-CLiQ interface between SINAMICSS110 drive and motor not only supplies the motor feedback to the drive(including temperature) but also the electronic nameplate information," saysCraig Nelson, product marketing manager for SINAMICS Drives at Siemens Energy& Automation.

Nelson says thisalleviates the need to parameterize motor data in the drive, forming a plug-and-play servo system as this information is automatically read up into thedrive. The performance of the drive isalso increased since auto-tuning algorithms have access to factory measurementsof the motor and important functions such as the resistance and inductance of thestator and rotor.

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