Saturday, August 24, 2013
ELECTRO HYDRAULIC STEERING GEAR
CONTROL SYSTEMS
(I) NON FOLLOW UP SYSTEMS
(II) FOLLOW UP SYSTEMS
With these systems the motor
runs continuously. Duplicate motors and duplicate feeders are normally provided
and in certain installations a change-over switch is provided so that each
motor may be supplied by either feeder.
Short circuit protection only
is provided in these feeder circuits, the normal overload protection being
replaced by an overload alarm.
CONTROL SYSTEMS
These are of three basic
types:-
(I) NON FOLLOW UP SYSTEMS
With these systems the gear
will run and the rudder will continue to turn while the steering wheel or other
controller is moved from its central position. Rudder movement is stopped only
when the steering control is centred once again (or when the rudder is brought
up against the stops).
It will be obvious that placing the filler amidships merely stops application of helm and does not remove it. Removal of helm must be effected by moving the tiller to the opposite side. Controllers with non follow up systems take the form of a wheel or a tiller lever or push buttons. A rudder indicator is fitted to indicate rudder movement.
It will be obvious that placing the filler amidships merely stops application of helm and does not remove it. Removal of helm must be effected by moving the tiller to the opposite side. Controllers with non follow up systems take the form of a wheel or a tiller lever or push buttons. A rudder indicator is fitted to indicate rudder movement.
(II) FOLLOW UP SYSTEMS
With these systems movement of
the rudder follows the movement of the steering controller e.g. if the
controller is moved to indicate a desired rudder position the rudder will turn
until the actual rudder angle is the same as the desired rudder angle shown on
the steering pedestal after which rudder movement will cease, the controller
remaining offset from its central position.
(III) AUTOMATIC SYSTEMS
With these systems the
steering control circuits are controlled by signals received from the master
compass, so that the ship is automatically held on to a selected course.
Primarily the system is so arranged that when the vessel is on course the rudder is amidships but as soon as the compass indicates an error the auto pilot applies an amount of rudder sufficient to bring the vessel back on course. By the time the vessel is on course again the applied correcting rudder has been removed.
With some systems, should it be required to alter the course being steered by the auto pilot by a few degree, this can be done by a Trim Switch and without necessarily reverting to hand steering.
Primarily the system is so arranged that when the vessel is on course the rudder is amidships but as soon as the compass indicates an error the auto pilot applies an amount of rudder sufficient to bring the vessel back on course. By the time the vessel is on course again the applied correcting rudder has been removed.
With some systems, should it be required to alter the course being steered by the auto pilot by a few degree, this can be done by a Trim Switch and without necessarily reverting to hand steering.
Any and all of the above
systems can be applied to both all electric or electro hydraulic steering
systems so that the following may be fitted:-
(i) Hand Electric (Follow Up)
(ii) Hand Electric (Non Follow Up)
(iii) Hand Hydraulic (“Telemotor Control”)
(iv) Automatic
(ii) Hand Electric (Non Follow Up)
(iii) Hand Hydraulic (“Telemotor Control”)
(iv) Automatic
and its normal practice to
fit at least two of the systems (i), (ii) and (iii).
Fig indicates Follow Up,
Non Follow Up and Auto Systems fitted to electro hydraulic power systems.
Thus it will be obvious that
an electric system of steering control consists essentially of:-
i)Steering pedestal or bridge unit. This produces electrical
impulses by operation of the steering control.
ii)Amplifier or control unit to transmit these impulses to the steering flat.
iii)After power unit to translate these impulses into mechanical movement of the power steering system.
ii)Amplifier or control unit to transmit these impulses to the steering flat.
iii)After power unit to translate these impulses into mechanical movement of the power steering system.
