Self-synchronising actuators simplify the automation of large or awkward loads
16 November 2018
Balancing large or awkward loads can be a challenge for many industrial applications. Whether it is the hood of a construction vehicle, a large work platform, a solar panel or an industrial material handling system, movements that are imbalanced can impact performance, cause unnecessary wear and tear, and jeopardise worker safety.
Synchronising actuators has traditionally required complex integration of external devices and extensive configuration or programming, but the latest generation of smart linear actuators is easy to install and capable of synchronising automatically.
Why synchronise actuator operation?
A load that is heavier on one end could lead to potential damage to equipment or its components if not handled properly. While some imbalance is predictable, others are the result of unanticipated events such as sudden load shifts. Equipment designers account for imbalance by using multiple actuators, but unless all are synchronised closely, problems can emerge. Using a pair of actuators to assist in raising and lowering the hood of a large construction vehicle, for example, can result in bouncing, slow operation, or unnecessary wear and tear if the actuators are not operating in tandem.
The larger and more uneven the load, the greater the need to synchronise the actuators that move it. Stabilising up-and-down and side-to-side motion of a 20-metre platform supporting workers as they build a jumbo jet, for example, could require synchronising more than 10 actuators. Complicating the challenge is the potential for the load to vary considerably during operation as workers move around the platform, and the fact that the platform itself may not be uniform due to weld tolerances in joined segments.
When properly synchronised, multiple actuators can also work together to handle loads larger than any of them could handle individually. The likely effectiveness in synchronising large or awkward loads varies considerably depending on whether they are using hydraulic, electromechanical or smart electromechanical actuators with intrinsic synchronisation.
Synchronising hydraulic actuators
In the simplest applications involving hydraulic actuators, designers might deploy two units to balance a wider load such as the hood lift mentioned earlier. This would involve running fluid lines to each actuator and provide some degree of synchronisation, but the actuators would not be operating with sensitivity to each other’s position. There would be no easy way to compensate for significant load changes or wear and tear that may increase over time.
When comparing a hydraulic cylinder versus an electromechanical solution, one might consider intuitively the hydraulic cylinder to be a more cost-effective solution, but when considering all of the components that go into a hydraulic system (pump, reservoir, manifold, hoses, control, etc.), the electromechanical solution provides a significant reduction in overall material and installation cost. On top of that, an electromechanical system requires no maintenance and will provide a cleaner environment as compared to a hydraulic system, which has numerous leakage points for fluid, adding even more cost over its operational lifecycle.
Synchronising electric actuators
During the 1960s and 1970s, motion designers began to replace hydraulic actuators with electric actuators. These were cleaner and easier to synchronise than hydraulic actuators but still required attention. System designers would need to program external controllers or switches to read digital position from encoders. Based on that, the program would adjust the speed of each actuator as needed to balance the load.
Synchronising smart actuators
Embedding microcontrollers into electromechanical actuators has added significant synchronisation capabilities. Manufacturers embed logic control and switching directly into the actuator itself. They operate with only four wires, two of which supply power, while the other two enable exchange of data across a communications network, eliminating the need for an external controller. Because all actuators are on a common circuit, they can read each other’s speed and position and adjust accordingly – but they still require someone to program the feedback loop that tells them what to do and when.
The latest generation of smart actuators, however, are even smarter. Manufacturers such as Thomson Industries, Inc., now embed all of the tracking capabilities and synchronising logic within the actuator itself, making virtually any number of equipped actuators self-synchronising.
In a typical configuration, a user would simply connect one actuator in the system to the switching device (i.e. simple switch or PLC) via two low-current wires. Any actuator in the system can be selected. When powered, all actuators in the system will continuously communicate position and speed, regardless of load fluctuation. When the system detects any variation of position, a message is sent to each individual actuator to either speed up or slow down until equilibrium is reached. Adjusting in step is necessary in that it enables the system to compensate for inconsistencies in load or mounting.
Actuator synchronisation is valuable in large-load, heavy duty applications with potential for imbalanced operation. This new technology enables users to synchronise actuators each capable of handling up to 16kN loads and with stroke lengths of up 1 metre (up to 10kN). There is also virtually no limit to the number of actuators that can be synchronised. In addition to the hood lifts and work platforms already mentioned, actuator synchronisation can be valuable in the following applications:
• Automatic Guided Vehicles (AGVs), where synchronisation can enable handling of a broader range of materials without human intervention.
• Solar panels, where synchronisation can enable more robust operation of large panels as they track the sun’s position, minimising impact of wind shear and reducing the need for specialised supports
• Mobile lifting platforms, where synchronisation can improve handling of lift gates without the complexity and maintenance requirements of a traditional hydraulic solution.
• Assembly stations, where synchronisation can contribute to effective and ergonomic lift support for off-centre or awkward loads.
• Industrial logistics trains, where synchronisation can automatically correct imbalances between the front and backend loads.
• Doors on ovens and large processing equipment, where synchronisation can enable smoother, safer opening and closing.
• Ergonomic patient-handling equipment, where synchronisation can improve the quality of patient care by synchronising operation of equipment such as lift tables and lift columns.
• Marine applications, where synchronisation can lead to smoother, more responsive steering through improved operation of rudder assemblies.
• Structural engineering, where synchronisation can improve operation of automatic loading doors in factories and warehouses, and floodwater damage-prevention gates.
Actuator synchronisation optimised
The ability of multiple actuators to synchronise themselves moves the handling of large and awkward loads to a new level of capability. It results in improved and more reliable performance, and faster and safer operation as it provides more efficient and longer life of the actuators themselves. Moreover, if the need for synchronisation is recognised up front, installing self-synchronising actuators carries a low-cost installation, faster setup and minimal long-term maintenance requirements. As more industrial operations become digitised and connected, the need to synchronise operation of multiple actuators – and the related benefits of doing so – is likely to grow.
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