Reducing pendulum movement of the load is a control engineering task. Many attempts have been presented. Mechanical dampeners, camera based solutions, mathematical control algorithms based on assumptions of rope length and mass — to name some examples.
Anti-sway solutions can be considered a supporting control device — something similar to what anti-lock brake systems (ABS) or electronic stability control systems (ESC) present today’s cars. However, anti-sway systems are not widely used in standard cranes.
Complicated installations
Many solutions require special components and installation may be complicated. As safety requirements are increasing, there is a growing interest to take the advantage of supported anti-sway control.
NoSwing NS100 is a novel anti-sway system for electronic overhead travelling cranes, which have X, Y and Z movements. The solution is being developed by NoSwing Ltd, a small Finland-based startup specialising on anti-sway control systems.
The NS100 system is based on a gyroscopic sensor and it works as a supporting control device connected to frequency converter. The control measures the inclination of the rope and feeds corrected control signals to motors. The system measures both X and Y dimensions and can control both hoist movement directions.
NoSwing operates by continuously measuring the angle of the hoisting ropes/ cables. Processing this data, it controls the crane’s frequency converters operating the hoist motors. The swing motion is avoided by keeping the ropes continually upright and vertical. This applies also when lifting a long object straight up from one end. NS100 sensor is mounted on the fixed part of the lifting rope.
The sensor requires 24V and Modbus field bus connection. This is wired to a frequency converter and parameterised as external control device. No cabling to pendant or operator panel is requried. NS100 is compatible with ABB ACS800, ACS355 and ACS880 series frequency converters and other manufacturer models are being developed. There are several parameters to adjust the anti-sway control logic.
Tailored special software applications may be developed for customer specific solutions as the system is programmable. External PLC and other automation systems may be connected to NS100 system as well. Same Modbus interface can be used and automation desingers may take the benefit of ready CodeSys building blocks.
The software of NS100 supports special functions for both start control and moving speed control. On start control model, the controller ensures that the crane will start and stop with minimal swing and respond to the operator actions on pendant as soon as possible.
Reducing swing
The software monitors the angle and an algorithm corrects the motor’s speed and start command.
A moving speed control model reads the rope angle values from the gyroscopic sensor and adjusts the motor speed accordingly. This reduces swing caused by external forces such as initial swing, wind, operator mistakes and obstacles.
The key benefits to users is improving the speed considerably and improving efficiency, especially with inexperienced operators. This can be achieved while reducing risks caused due to swinging load. Additionally, wear of ropes/cables can be reduced, which saves in maintenance and repair expenses.
As technology is developing, using electronic anti-sway systems becomes increasingly attractive for smaller cranes and applications beyond large harbour cranes. In the future, all EOT cranes will have such functionality, as today’s cars are equipped with ABS and ESC.
