SIMOCRANE Sway Control System

The SIMOCRANE Sway Control System is based on calculations of a mathematical oscillation model. When a camera is used, the parameters hoisting height, swing angle and rotation angle are determined by means of optical contact-free measurement, and are incorporated in the calculation model. If the measuring signal of the camera fails, only the states of the model are used.

Damping of the load is performed by influencing the traversing speed for each axis individually. When using the position control the defined positions are automatically approached with sway control after enabling. The axis is controlled in such a way that the load sway is eliminated not only when the maximum speed is reached, but also at the target position. All swaying resulting from the travel motion is largely eliminated. If a camera is also used, swaying resulting from external forces – such as inclined lift or wind – can be almost completely compensated.

Operating modes

The following operating modes and functions are available for the general application areas:

• Manual mode (MAN)
• Positioning (POS)
• Sway neutralization
  • Load position (SNL¹⁾)
  • Trolley position (SND²⁾)
• Trim, list and skew control (TLS)
• Skew damping
• Semi‑automatic mode (SAM)

¹⁾ SNL: Sway neutralization load position

²⁾ SND: Sway neutralization trolley position

The mode is selected (depending on the functional scope) by the PLC by setting the appropriate operation mode bit.

Manual mode (MAN)

In the manual mode, the speed is specified manually from a higher-level controller. The trolley is accelerated or decelerated to the set speed in such a way that the load sway has been eliminated when the set speed is reached.

Sway control is active in manual mode either throughout the complete traverse, or only during a halt.

Positioning (POS)

In the positioning mode, the higher-level controller or the internal setpoint encoder can specify a target position for each individual axis. This position is approached automatically after enabling. The axes are controlled in such a way that the load sway is eliminated not only when the maximum speed is reached, but also at the target position. The direct path between the current position and the target position must be free of obstacles.

Sway neutralization (SNL/SND)

The sway neutralization mode (only for the version with camera) is used to eliminate swaying movements of the load from standstill.

Sway neutralization is linked to a positioning function. The target position is either the current trolley position (SND) or the load position (SNL) at the time the sway neutralization is activated.

Sway neutralization results in slight travel movements to both sides of the target position.

The position of the load is acquired by the camera measuring system.

Trim, list and skew control (TLS control)

TLS control controls the trim, list and skew positions of a spreader.

The TLS control function assumes that

• the length or
• the pivot points

of the 4 support cables of a spreader can be adjusted by hydraulic cylinders, or an additional electric drive with the aid of the camera.

Schematic diagram of TLS movements

Each cylinder can be traversed individually for calibration purposes. Through actuation of these hydraulic cylinders in pairs, the spreader can be tilted to the left or right (trim), inclined towards the waterside or landside (list) or rotated in a clockwise or counterclockwise direction (skew). All of these TLS movements can be carried out simultaneously. The current positions of all 4 cylinders can be saved as zero positions and approached again. For TLS positioning, either the last TLS setting or the TL setting with an externally definable rotational position can be approached.

The TLS control function is subdivided into two categories, each of which requires a separate license:

• TLS Basic modes
  • Cylinder inching
  • Approach zero position without skew damping
  • TLS inching without skew damping
• TLS Advanced modes
  • Cylinder inching
  • Approach zero position with skew damping
  • TLS inching with skew damping
  • TLS positioning with skew damping

Skew damping

Skew damping is an electronic anti‑sway function which eliminates the skewing motion of the spreader by means of the hydraulic cylinder control or an additional electric drive. The skewing motions are recorded by the camera. In the conventional mechanical design, TLS positioning as well as skew damping is performed via the hydraulic system. In a combined mechanical system using a hydraulic system and electrical system, TLS positioning is performed via the hydraulic system and only skew damping is performed by the electrical system. This ensures more efficient and more dynamic damping.

Semi‑automatic mode (SAM)

The semi‑automatic mode allows the system to be set up so that the load is traversed along a "path curve". The path curve is specified to ensure that the spreader or grab does not collide with the crane structure or with containers or other obstacles, and also reaches its target position accurately. This operating mode can be used for ship to shore cranes (STS) and ship unloaders (GSU).

The obstacles are stored in the system as blocked regions and traversing is only permitted outside these areas. Depending on the starting point and the target position, the fastest possible travel path is generated from the data about the blocked regions. Both axes (trolley and hoist) must be operated in the internal semi‑automatic mode.

The container stack can be specified externally by the crane controller or acquired internally (learnt).

The path curve is calculated on the basis of a layout of the working area in which blocked regions are defined. Blocked regions are individual or several combined obstacles or also areas which the crane must not enter for safety reasons to avoid collisions. A distinction is made between fixed and variable blocked regions.

A blocked region is described by two trolley positions and one hoisting position.

The types of blocked regions and their purposes are shown in the following graphic.

Layout of blocked regions

If a bay scanner is also used, the signal of the obstacle height is evaluated in addition to the traveled curve. The distance from the scanner to the surface of the container stack is measured (see graphic below, dashed lines).

This value must be converted to a laser value in the PLC which corresponds to the distance from floor = NULL to the top edge of the container stack at this point (see graphic below; converted laser value). The vertical distance between 2 valid measuring points is set to the height of the highest measuring point.

Measurement of the height of the container stack with the laser scanner

Additional functions in the grab crane application area

Position control with on‑the‑fly unloading

In the ship unloader application (GSU) on-the-fly unloading utilizes the swinging of a grab when unloading bulk goods and saves turnover time in this way. The trolley is decelerated before the target position while the grab is swinging to the target (e.g. hopper). During swinging over the target area the grab is opening for unloading. As soon as the grab reaches its target position, the trolley starts return travel. In this way the trolley shortens the travel distance and the grab remains longer in the hopper area.

Grab crane (GSU)

Additional functions for application OHBC, Gantry crane

This application includes overhead bridge cranes (OHBC) and gantry cranes, as well as RTGs and RMGs with two axes in the plane (trolley, gantry) and an additional axis (either slewing gear or hoisting gear).

Either manual mode (MAN: a speed setpoint is set on the master switch), or positioning mode (POS: a target position is set), can be selected. The operating mode of each axis can be switched over, e.g. from manual mode to positioning mode and vice versa, while the axis is moving.

Each axis moves independently from the other axes.

Note:

Various licenses which cover combinations of the operating modes described above are available for the sway control systems (see Selection and ordering data).