Mitsubishi Heavy Industries Technical Review Vol. 48 No. 4 (December 2011)70

Development of the Anti Rolling Gyro 375T
(Rolling Stabilizer for Yachts)
Using Space Control Technology

HIROSHI TAKEUCHI*1

KATSUYA UMEMURA*2

SADAHIRO MAEDA*1

The ARG is a roll reduction device for vessels that utilizes gyro torque stabilization. It can
reduce roll, even at zero speed. To date, Mitsubishi Heavy Industries (MHI), Ltd., has developedand sold two types of ARGs, and has now developed a new system, the ARG375T(*), which has a50% increase in capacity as compared to previous models. During development of the ARG375T,
sea trials were conducted in Japan and Europe to evaluate its anti rolling performance, handlingcharacteristics, and safety envelope, along with bench-testing to evaluate its performance andstrength. The development is now complete, and the device has been brought to market. MHI
introduces the ARG375T in this document.
(*)
In the name ARG375T, “375T” refers to the torque (375  100 Nm).

|1. Introduction
The ARG is a roll reduction device for vessels based upon the gyroscope principle. It wasdeveloped by applying one of MHI’s space-control technologies, the Control Moment Gyro, to thefield of motor yachts, and can reduce the rolling motion improve the ride quality. One of theARG’s advantages is its ability to reduce roll even at zero speed, which cannot be achieved using afin stabilizer that exploits the lift force generated during cruising. As the device uses gyro torque, it
can be effective regardless of its location in the hull, and can be retrofitted on existing vessels.
From 1990, MHI has considered applying gyro technology to anti roll products to be used insystems, including ski gondola cabins and lifted loads,1 prior to bringing anti rolling devices forsmall boats and commercial vessels to market in Japan. In 2004, MHI formed an exclusive
agreement for the sale of anti roll devices for vessels with an Italian yacht manufacturer, and hassince produced and sold them in Japan, the US, and Asian markets, in addition to the main
European market. Sales temporarily fell due to the financial crisis, but have since recovered alongwith the recovery of the motor yacht market.
The Italian yacht manufacturer, an important client of MHI, has expanded their sales byemploying the MHI-branded ARG device. This both differentiates them from their competitors andbenefits MHI by selling the ARG as standard yachting equipment. In this way, the two companies
have established a win–win relationship.
Some of the vessel manufacturer’s yachts previously employed both of the existing ARG
models, i.e., two ARG devices in total. The manufacturer wished to start using a single new model
instead, and the ARG375T was designed in response to this demand. The width of the new model
was tailored to the keel width of the yacht on which it is to be employed, and its weight is less thanthat of previous models. In the design process, MHI paid particular attention to safety during
development, via the installation of new safety devices and through the implementation ofdestructive tests based upon assumed failure modes. In terms of the applicable market, the newARG can be utilized on larger vessels, having displacement of approximately 250 tons, to which
previous models were not suited; this expansion of the market was achieved since the newly
introduced ARG has a work capacity of half as much again as the previous model.
*1Guidance & Propulsion Division, Aerospace Systems*2

Engineering Manager, Guidance & Propulsion Division, Aerospace Systems

Mitsubishi Heavy Industries Technical Review Vol. 48 No. 4 (December 2011)
71|2. Overview and Features of the ARG
The ARG has a high-speed spinning flywheel that is supported by a gimbal. When thegimbal is rolled (i.e., an angular velocity is applied to the gimbal), the flywheel generates a gyro
force in the direction perpendicular to the angular velocity.
The output torque of the ARG, TARG, is obtained． from the cross product of the ARG angularmomentum, H, and the gimbal angular velocity, Θ. The ARG uses this torque in the direction
counter to the roll of the hull, with a resultant net reduction in rolling. Figure 1 illustrates theoperating principle.

Figure 1

ARG operating principle

The ARG is a passive device; the functional block diagram is shown in Figure 2. As apassive device, it detects the rolling angular velocity of the vessel using the gyro effect, andcontrols the gimbal angular velocity using an energy absorber (i.e., a damper). Thus, it does notneed a sensor or a gimbal controller for active detection of the hull attitude, simplifying the system
and improving its reliability and safety.
ArticleFunctional block
diagram

Performance
SystemSafetyFigure 2

Passive type

Active type

Damping enhancement

Suitable for a wide range of frequencies, due
to variable damping and stiffness
No controller needed, simple construction
A sensor and controller are needed; theconstruction is complex
No controller, no possibility to magnify the Failure of the controller may lead toroll of the vessel
magnifying the roll of the vessel

ARG functional block diagram

Furthermore, the motor and bearings are air-cooled, meaning that the ARG does not need
auxiliary cooling equipment required by other cooling systems such as water cooling, thus
installation of piping etc. is not required. This contributes to its maintainability. Figure 3 shows anexample of ARG installation.
The ARG system configuration is shown in Figure 4. It consists of an electric power source,a motor driver, and an ARG unit. Electric power is supplied to the motor driver from an on-board
generator, through a breaker switch, and is used to drive a flywheel inside the ARG. This motor
driver employs an inverter and exclusively serves the ARG unit.

Mitsubishi Heavy Industries Technical Review Vol. 48 No. 4 (December 2011)72

Figure 3 Example ofARG installation

Figure 4 ARG system configuration diagram

A remote switch is available, enabling start up or shut down of the ARG from a remotelocation, such as the cockpit. The start check lamp and the rotation rate check lamp, which lights
upon attainment of steady rotation, are connected, enabling check of the ARG operation status. Themotor driver is equipped with a variety of protective functions that are configured to shut down theARG if abnormal operation is detected. The ARG375T is newly equipped with a safety device,
which shuts down the ARG when a temperature sensor, installed on the damper of the ARG,
detects temperatures over the specified working range. For operational details, refer to Section 3.
The ARG product range is shown in Table 1. As described previously, the numeric value(125, 250, or 375) of the name refers to the output torque, i.e., the product of the flywheel angularmomentum and the gimbal angular velocity. For instance, the ARG375T outputs up to 37,500 Nmtorque. These ARG's names consisting of their output torque represent that they are characterized
by larger output gyro torque with respect to angular momentum due to larger gimbal rolling angle
range of +/- 90 degrees.
Table 1Name
Model

ARG125T
MSM-12500T-A1

ARG product range
ARG250T
MSM-25000T-A1

ARG375T
MSM-37500T-A1External view

Angular2,500 Nms
5,000 Nms
7,500 Nms
momentumOutput torque
12,500 Nm
25,000 Nm
37,500 Nm
Dimensions
930 mm × 590 mm × 570 mm 1,000 mm × 700 mm × 720 mm 1,120 mm × 780 mm × 830 mm(W  H  L)
PowerSingle phase: 3.8 kW / 3.4 kW Single phase: 4.8 kW / 3.5 kW Single phase: 5.5 kW / 4.5 kW
consumption
Three phase: 3.4 kW / 3.0 kW Three phase: 4.3 kW / 3.0 kW Three phase: 5.2 kW / 4.3 kW(maximum / rated)
Weight300 kg
700 kg
910 kgVesselVesselspecificationsLength: 14.15 m
Beam: 4.34 m
Displacement: 18.2 t

Length: 20.63 m
Length: 22.50 m
Beam: 5.63 m
Beam: 5.50 m
Displacement: 45.0 t
Displacement: 56.9 t
Note: Yacht photographs provided by Ferrett Gr.

Mitsubishi Heavy Industries Technical Review Vol. 48 No. 4 (December 2011)73|3. Development of the ARG375T
Three prototypes were fabricated, enabling various experiments to be conducted in parallel.
This allowed the development of the ARG375T to be completed in 1.5 years – from the beginningof the design process to completion of the development tests followed by commercial production,
as shown in Table 2. The bench-test evaluated the strength, effects of the operating environment(with respect to temperature), and durability over a five-month test period. The sea trial evaluatedthe anti rolling performance, handling, and safety on an actual vessel over a three-month testperiod.
Table 2

ARG375T Development test schedule

Details of the tests implemented during development of the ARG375T are shown in Table 3.
The results of the gimbal-rolling test, one of the functional tests, are shown in Figure 5. This
test evaluated the ARG output torque by measuring the angular velocity of the gimbal, spun whenthe mounting base of the ARG was rolled in a sinusoidal fashion. As shown in Figure 5, themeasured results conform to simulation data, verifying that the ARG generated the specifiedtorque.
Table 3
Test article
Functional test
Strength anddestructive test
Environmental test
Durability test
Sea trial

Figure 5

Details of the ARG375T development tests

Test details
Check the basic characteristics, such as start up, shut down, rated operation features, etc.
Check the output with respect to the predicted maximum load.
Check the output by applying a load exceeding the predictions.
Check the basic characteristics under the predicted high-temperature ambient condition.
Check the durability during long continued operation.
Check the anti roll performance, handling, and safety on an actual vessel.

Measured results of the gimbal rolling test

Mitsubishi Heavy Industries Technical Review Vol. 48 No. 4 (December 2011)74

As the ARG has a high-speed spinning flywheel, there is the potential for a severe accident tooccur if the ARG unit was to break. Thus, as a measure to address product liability, a destructive
test simulating a failure mode was conducted. This test was carried out by simulating a reduction in
the damping force of both of the gimbal angular velocity control dampers. As a result, although thegimbal continued rotating with an angular velocity higher than the specified limit, no abnormality
occurred within the major components, such as the flywheel, etc., and the test verified that no
critical breakage would occur. The test is detailed in Figure 6.
The new safety device functions by shutting down the power supply to the ARG if the user
overloads the unit (by, for example, using it during high-wave conditions), if the damper forcontrolling the gimbal angular velocity fails, or if the temperature limit specified for the device isexceeded as a result of temperature rise inside the room where the ARG is installed. This device
enhances safety and has also been added to the existing ARG model range.
In the development phase, a risk assessment based on the MIL-STD-882 and BS8800 (2004)
was carried out to identify hazard sources. The results of the assessment are reflected in the designof the device, the instruction manual, and the warning labels. For example, a protection device wasadded to the motor driver so that it would not easily fail due to wiring faults.
One of the important factors during the development of the ARG was the requirement tocomply with the European registration, evaluation, authorization, and restriction of chemicals(REACH) regulations. To achieve this, MHI now manages information about the chemicals used in
the components in collaboration with its partners in the supply chain, established during productionof previous ARG models. This information is used for parts selection and compliance checking.

Figure 6

Destructive testing|4. Sea trial
Specifications of the Japanese vessel and the European mega yacht on which anti roll effectof the ARG375T was evaluated are shown in Table 4. These were each equipped with one
ARG375T and four ARG375Ts, respectively. For the Japanese vessel, rolling angles with andwithout the ARG enabled were measured three times for different wave heights. The results of thefirst measurement are shown in Figure 7. At zero speed, an anti roll rate of 70% was achieved.
Table 4

Specifications of the vessel and yacht used
to evaluate the anti rolling effect

ArticleLengthBeam
Displacement
MetacentricheightNatural period
Number ofARGs

Japanese vessel
specifications
17.2 mApprox. 3.9 m
22.0 tEuropean mega yacht
specifications
Approx. 31.5 m
Approx. 6.7 m
Approx. 177 t

Approx. 1.3 m

Approx. 1.6 m

Approx. 2.5 s

Approx. 4.8 s

ARG375 T: 1

ARG375T: 4Figure 7
Measurement results ofARG roll reduction performanceon Japanese vesselMitsubishi Heavy Industries Technical Review Vol. 48 No. 4 (December 2011)75

The evaluation results of the four ARGs installed in the European mega yacht are shown in
Figure 8. This yacht also demonstrated a favorable anti roll effect, which was appreciated by theuser. As shown in Figure 9, the predicted anti roll rate, obtained by simulation using the vessel’s
specified displacement, metacentric height, and natural period of rolling, conformed to the actual
results measured on the yacht.

Figure 8

Measurement results of ARG roll reduction performance on European yacht

Figure 9Comparison between simulated and measured results taken on actual vessel|5. Conclusion
The ARG can be used for zero-speed anti rolling in yachts, as well as for seasickness
prevention and improving the ride quality of general marine leisure boats and fishing boats. It canalso be utilized in workboats, survey boats, and patrol boats, providing improved work efficiency
and deck work conditions during mooring and touchdown work, along with superior vessel
maneuverability and reduced crew fatigue.
Competing products, such as a gyro anti rolling device similar to the ARG and a zero-speed
fin stabilizer anti rolling device, have appeared. MHI will continue to improve the existing ARG,
enhancing the product range, and will work on marketing in Brazil and Asia in order to continue tomeet the anti roll needs of various users around the globe.

Reference
1.

Hoshio, A. et al., Stabilizer by Control Moment Gyro, Mitsubishi Juko Giho Vol. 31 No. 3 (1994)
pp.213-216