More than 5000 participants from 42 countries attended the recent Society for Laboratory Automation and Screening (SLAS) annual conference and exhibition in Washington D.C. SLAS is the premier show for laboratory automation, with a strong focus on the drug discovery market place.
Inspired by the awards season, our SLAS show recap will take on an "awards show" format. The two-part series will focus on supporting and leading roles in the two categories of motion control and industry trends. Our goal is to capture the biggest takeaways from this year's show and to highlight the technology trends that are driving changes.
In this blog, we will cover our awards in the motion control category.
The award goes to closed loop steppers. The trends we are seeing in diagnostics are carrying over to lab automation and screening, where there is a desire to have deterministic motion. This need to have up-to-date knowledge of exactly where samples and specimens are at all times is driving more axes to have encoder feedback.
The technology is also allowing some users to better optimize their designs because control algorithms and advanced features allow for stall detection and resonance reduction, so stepper motors can be pushed to their max output thus reducing the need for oversizing the motor.
Through the addition of an innovative closed loop control algorithm, true closed loop steppers systems maintain the inherent advantages of stepper control (high torque, stiffness, responsiveness, stability, no dither, and simplicity) while eliminating common disadvantages of open loop stepping (stalling, energy usage, motor temp, high speed operation, positional accuracy).
Unlike traditional closed loop servo systems, state of the art closed loop steppers require no tuning. Gains have been optimized for the motor/drive combination to ensure smooth and stable motion. Once the closed loop stepper reaches its target position, the rotor locks into place at a perfect standstill. Traditional servo motors typically hunt between encoder pulses at standstill, which could adversely affect applications requiring zero vibration.
Synchronization errors and motor stalling that plague traditional stepper systems are eliminated with advanced closed loop control algorithms allowing for higher torque and speed performance. Many closed loop steppers also incorporate a “peak torque boost” feature that increases available torque for starting and stopping by as much as 50%.
The award goes to direct drive servo technology. Although, stepper technology continues to outpace servo technology from an axis count basis, servo technology continues to gain ground with each new instrument release.
At the instrument level, the two biggest launches at the show were the Prime from HighRes Biosolutions and the Biomek i7 from Beckman Coulter. Both of these new releases feature direct drive linear servo motors for higher throughput and higher reliability, similar to what we have seen from other high performance industry players like Dynamic Devices.
There were indications that companies are leveraging integration of direct drive rotary servo kit motors into their Z axis designs to optimize the size and performance characteristics of those axis of motion.
Direct drive servo motors are available as conventional rotary motors in a kit form as well as linear servo motors. Rotary kit servo motors are modular stator and rotor components that are designed to be integrated into instruments allowing for lower cost, more compact overall designs.
Linear servo motor kits are the just like rotary kits that have been rolled out flat. Generally, servo motor technology offers the advantages of more torque, higher speeds, and greater precision as compared to stepper motor technology in a similar size range. These advantages are leading growing numbers of instrument builders to favor servo motors to boost their instrument performance.
Direct drive technology, as the name implies, creates direct coupling between the motor and the drive train. In the case of direct drive rotary kit motors, the motor is typically directly coupled to the ball screw, lead screw, or belt pulley, thus reducing the overall component count and design complexity.
Direct drive linear servo motors are directly coupled to the payload without the use of any mechanical reduction or drivetrain. The major drawback—or in some applications, the major advantage—is its lack of mechanical advantage. Any force or torque required by the application must be directly generated by the motor, which might require using larger motors and larger overall current draw.
Another historical disadvantage to servo technology, and linear servo technology, has been the total system cost. Much of this is driven by the cost of the encoder feedback, but with advances in magnetic encoders, the cost premium continues to reduce.
Despite these perceived cost issues, linear motor technology offers many advantages, including dynamic performance, precision, stiffness, and the smallest form factors available.
Watch for the second part of our SLAS 2017 recap where we cover our awards for best supporting and leading roles in industry trends.
In the meantime, you can view the products we featured at this year’s conference.
Article contributed by Brian Handerhan, business development manager, Electromechanical and Drives Division North America, Parker Hannifin Corporation.