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The area of motion simulation, especially that of flight simulators
(Figure 1), is currently the main commercial application of parallel mechanisms.
These simulators, albeit very popular and providing very realistic cues,
have several notable
disadvantages including a restricted workspace (mainly with respect to rotation), prohibitive
cost, limited operation and they require high maintenance. Moreover, the oils contained
in the actuators can be an environmental problem for some people.
Fig. 1: Flight simulator (courtesy of
CAE).
To eliminate these disadvantages, the laboratory has designed
a low-cost flight simulator having a limited number of degrees of freedom
and a simple architecture,
which is able to create motion cues realistic enough to allow it to be
used for the training of pilots (during the first phases of their training).
Several research studies were carried out during this project, including a comparison
of cues which can be created by various 3-DOF architectures so as to choose the most
suitable architecture. Then, a design of a mechanism was achieved
incorporating several innovative ideas, such as static balancing
and the use of rotoid electric actuators. The design is presented in
Figure 2 and a plastic prototype, reduced by a factor of 10, is shown in
Figure 3.
Fig. 2: Schematic representation of the flight simulator. |
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Fig. 3: Plastic prototype of the flight simulator. |
The model has 2 legs, of types RRU and RUS,
and one passive Hooke joint on which the
seat, controls and screen are mounted. The legs allow
rotations to be carried out around a cone, while a motor added to the platform allows the platform to
pivot in a plane normal to it. Thus a range of motion of
±60 degrees is possible.
Software and Material Architecture and Communications
A flight simulator is composed of several elements. In addition to motion systems,
there are the flight controls (sleeve, rudder, pedals), the visual system
and the computation system. A schematic of the sub-systems of a flight simulator is
available by clicking here.
Several componants were thus added to obtain a complete and functional
flight simulator. The main details are provided below:
- Standard componants, such as the sleeve, rudder and pedals were
bought for the control of the system. In addition, a spherical screen, 4 feet in diametre is
used as a projection screen.
- A commercial software, X-Plane,
is used to calculate the mathematical model of the airplane
and for the graphic representation of on-board instruments as well as
the outside environment.
- The X-Plane data are sent to two locations: to the controller to actuate the
motors and to a computer that calculates the spherical projection of the images and projects them
on the spherical screen.
- The controller sends the X-Plane data through a series of washout filters,
which modify some of the data according to the available workspace.
These filters were developed within this research project.
- Finally, the filtered data is sent to a control unit (control card,
amplifiers, encoders, etc.) which carries out the desired movements.
- The time required for the computation of the spherical projection is the same as that
required to filter the data and actuate the motors. The result is thus simultaneous.
The complete system is presented in Figures 4 and 5. All of the componants are
shown, with the exception of the motion system whose construction has not been completed.
- Workstation A, B and C: computers offering X-Plane used for calculation of the
dynamic model of the airplane (A) and the conducting of the spherical projection of the images (B). Post C
is an instructor post enabling the modification of the flight conditions (motor breakdown or
deteriorating weather conditions, for example).
- Workstation D: control computer, used to filter the data and carry out the
simulation in real-time. Communicates with the amplifiers which control
our small prototype.
- Workstation E: used for the post-treatment of control data.
Fig. 4: Computation system and controller.
Fig. 5: Audio-visual system.
Several tests were carried out with the plastic model, to test the
various sub-systems and to carry out real simulations; pilot inputs,
spherical projection and motor movements. The results are very promising.
The flight simulator developed in the laboratory offers numerous advantages. The small size
and low cost of this simulator make it a very good tool for the first steps in
pilot training, especially for small companies. Its large range of motion allows it to simulate
very agile airplanes (military airplanes) as well as commercial airplanes
(Boeing, Airbus, etc.). The realism of the spherical screen provide an excellent immersion
of the pilot in the simulation.
Poster
A poster describing the flight simulator was prepared in 2002 and can be
downloaded with the PDF below.
 Installation of Movements Simulation Balanced Statically (4.3 Mb)
Video Clips
The following video sequences show the flight simulator in operation.
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Flight simulator: workspace
Video clip showing the workspace of the mechanism as well as several feasible velocities and accelerations (slowly and rapidly).
Format: avi Length: 1:27 Size: 117.4 Mb
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Flight simulator: static balancing
Video clip showing forces needed at the actuators for a takeoff, with and without static balancing.
Format: avi Length: 0:25 Size: 32.2 Mb
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