Modular conveyor system having multiple moving elements under independent control

Abstract

The modular conveyor system comprises N interconnected track sections, forming a continuous track, wherein each track section features a plurality of individually controlled coils stretching along the length thereof. Plural pallets, each having thrust producing magnets, travel independently alone the track. The track also comprises multiple linear encoder readers spaced at fixed positions therealong, and each pallet includes a linear encoder strip having a length R greater than the spacing E between the readers. Track section controllers associate the encoder strips with only one reader at any time in order to resolve the position of the pallets based on the fixed position of the readers and the relative positions of the strips in relation thereto. The section controllers also regulate and commutate the coils of the corresponding track sections in order to independently control each pallet. Communication links interface adjacent section controllers situated in adjacent track sections. The electromagnetic structure and distributed control architecture of the conveyor system enable it to independently control multiple practical pallets yet be constructed out of modular track sections, with little practical restriction on the length of the conveyor system or the number of pallets controlled thereby.

Description

FIELD OF INVENTION[0001]The invention generally relates to conveyor systems, and more specifically to conveyor systems in the form of modular linear motors having multiple moving elements under independent control.BACKGROUND OF INVENTION[0002]There are a number of fundamental limitations with well-known conventional conveyor systems which employ a belt for transporting pallets between processing stations. First, the speed of the belt is typically quite limited. This is largely due to the fact that the pallets are typically stopped, e.g., in order to be processed at a processing station, by mechanical stop mechanisms. Thus, if the belt conveyor is operated at a high speed, the strong impact between a pallet and mechanical stop is likely to jar whatever parts the pallet may be carrying for processing. Second, it is generally not possible to vary the acceleration and velocity profiles for individual pallets. For instance, if a first pallet is empty and a second pallet is loaded with de...

AI Technical Summary

Benefits of technology

The invention provides a conveyor system with multiple moving elements that can be controlled independently. The system has multiple track sections that can be joined together to form a continuous track. Each track section has a stator armature with individually controllable coils. Each moving element has a plurality of thrust producing magnets arranged in alternating North and South sequence and disposed face to face with the stator armature. The system also includes a servocontrol system for regulating and commutating the coils to produce a separate moving magnetic force for each moving element. The system can be modular, with interconnected track sections forming a continuous track. The invention also provides a modular linear motor with individually controllable coils and a plurality of linear encoder readers for detecting the position of moving elements. The system also includes communication means for interfacing the section controllers of adjacent track sections. The technical effects of the invention include improved control over the movement of multiple elements, increased flexibility, and reduced limitations on the length of the conveyor system.

Problems solved by technology

There are a number of fundamental limitations with well-known conventional conveyor systems which employ a belt for transporting pallets between processing stations.

First, the speed of the belt is typically quite limited.

Thus, if the belt conveyor is operated at a high speed, the strong impact between a pallet and mechanical stop is likely to jar whatever parts the pallet may be carrying for processing.

Second, it is generally not possible to vary the acceleration and velocity profiles for individual pallets.

For instance, if a first pallet is empty and a second pallet is loaded with delicate parts, it is generally not possible to aggressively accelerate the first pallet to a high speed while controlling the second pallet using more gentle acceleration and velocity profiles.

This limitation affects the latency and possibly the throughput of the manufacturing line.

Third, belt conveyor is typically not bidirectional, which may result in a suboptimal design of the manufacturing line.

Fourth, the belt conveyor typically provides limited flexibility or programmability, such as being able to very quickly change the positions of processing stations.

Finally, the data acquisition capabilities provided by the belt conveyor are typically quite limited.

For example, it is typically not possible to know where the pallets and their constituent loads are located along the conveyor at all times. Thus, for instance, it may be difficult to know how many pallets are queued at a particular processing station.

Conveyor systems having multiple pallets under substantially independent control are known in the art, but suffer from a variety of limitations.

This makes changing the location of a station a troublesome endeavour.

In addition, the system is not capable of pinpointing the location of a moving pallet at any time.

In view of these limitations, the Takeuchi et al. system does not feature truly independent and total control of multiple moving elements.

First, due to the fact that a separate track of position / commutation sensors is required for each moving element, the system can only accommodate a relatively small number of moving elements.

Second, the length of the linear motor is limited by a servocontrol mechanism, described as a single microcomputer, which can only process and accommodate a limited number of the position / commutation sensors and associated electric current generating control circuitry.

Third, use of the magnetic position-detecting elements provides a relatively poor resolution for measuring the position of the moving element.

Fourth, the winding arrangement of the stator armature is essentially that of a linear stepper motor, which presents an uneven magnetic reluctance along the stator armature resulting in relatively noticeable cogging effects and a jerky thrust production.

Finally, the, coreless design of the stator armature also results in a relatively low average thrust production which may not be suitable for typical conveyor system applications.

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