Low-inertia motion control system speeds barriers

PathMinder retracting security barriers for controlling pedestrian access to buildings use low-inertia Baldor servo motors with neodymium magnetics to achieve opening times of well under 500 millisecs

Low-inertia motion control system speeds intelligent security barriers.

Optical turnstiles achieve opening times of less than half a second.

PathMinder's latest retracting security barriers for controlling pedestrian access to buildings use low-inertia Baldor servo motors with neodymium magnetics to achieve opening times of well under 500 milliseconds.

In conjunction with fine control of the drive's control loops and dynamic motion facilitated by the Mint-based software, the barriers offer a combination of speed and smoothness that is setting new standards in the access control industry.

Intelligent sensing is a core driver for Ottawa-based PathMinder, and the OEM has developed a unique infrared beam and pattern recognition system that defeats attempts at unauthorized access such as 'side-by-side' passages (ie two people trying to walk through together).

But speed and smoothness of operation are equally critical, to optimise throughput and support productivity enhancements in access tokens such as proximity cards, and to instil confidence that encourages users to speed their passage.

These requirements place performance demands on the underlying motion system, and PathMinder selected a system based on two of the Baldor BSM N-series of brushless rotary servo motors to actuate the barriers, controlled by two of the Baldor Flex+Drive series of drives.

The motor rare-earth neodymium iron boron magnetics - with an inertia figure that is considerably less than standard servo motors using ferrite magnets - provide a responsiveness that speeds barrier actuation.

The magnetics additionally help to deliver higher than average torque for the size of motor, a feature that helped PathMinder to install a movement system within the small enclosure that houses the retracting barriers that is capable of supporting a 100% duty cycle.

The PathMinder need for compactness was aided by the selection of the Baldor Flex+Drive controls, which integrate all the normal features of a servo drive, with a programmable motion controller and I/O.

Smooth dynamic movement was simplified by the drives Mint motion control language which gave PathMinder high-level commands to optimise the movement profile for the application and fine-tune the drive's real-time current, speed and position parameters.

An additional attraction for PathMinder was the Mint ability to dynamically monitor drive current, and if necessary limit it on the fly, so that the parameter could be employed as part of the barriers' triple-redundant safety system that prevents closure on a person.

"The high native speed of the barrier actuation system gives us plenty of leeway at the system level to determine access control rights and open the barrier without slowing pedestrians," says Gennady Reshetnikov of PathMinder.

"Although performance was the key factor in designing this system, the production volumes in this business demand a competitive motion control architecture - a goal that's been greatly aided in this instance by the use of all-in-one intelligent drives - with their built in positioning capability", adds Kris Nair of the Baldor Ontario office, who provided applications support.

PathMinder turnstile designs offer a combination of speed, security and safety.

Fast barrier retraction contributes to a real-world traffic throughput of 30 people per minute - which helps avoid queuing.

Tall, heavy glass is typically used to offer a strong physical barrier which, combined with PathMinder optical detection matrix, offers excellent security.

Three independent safety sensors are utilised to stop the barrier before making contact with a person-a feat possible only with strong, precisely controlled motors.

Further information on PathMinder optical turnstiles with barriers - including a video of the barriers in action - can be found on the website.

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