SimCENTER Hungary

This document describes the principles and engineering reasoning of the 301 platform as are related to high performance driving simulation. Other simulation venues or entertainment/arcade utilization have similar, but not identical, issues.

• The Force Dynamics 301 and 401 series are small, high performance motion simulators used mainly for event marketing, LBE and training.
• The platforms' provide motion via pitch, roll, yaw, heave and - depending on configuration - surge and sway. Motion range and capability can be specified based on configuration, platform load and software setup.
• The 301 and 401 series system may be customized to meet client specification for payload, size and so forth, without changes to the basic motion system itself.

In three dimensions, the six DOFs of a rigid body are described using these nautical names:

1. Moving up and down (heaving);
2. Moving left and right (swaying);
3. Moving forward and backward (surging);
4. Tilting forward and backward (pitching);
5. Turning left and right (yawing);
6. Tilting side to side (rolling).

source: wikipedia - http://en.wikipedia.org/wiki/Degrees_of_freedom_(mechanics)

The 301 uses motion simulation techniques that have been well-known for many years. There exist many commercial platforms which can provide the physical cues that the 301 can. Why is it special? The 301 can deliver those cues with a much smaller hardware package at a much smaller price. The 301 driving experience has been compared favorably at trade shows with competing equipment weighing – and costing – ten times as much. Force Dynamics was able to provide this increase in performance by designing the 301 platform specifically for its task, rather than adapting existing technology meant to move larger masses in a different way.

Usually, the phrase 'motion simulator' brings to mind giant aircraft training systems used by airlines and the military. In the past decade, motion simulators have started to creep in to entertainment, too - most theme parks worth their salt have a 'motion theater' or two, multi-person 'pods' have popped up at fairs and promotional events, and in the past few years, motion arcades like Silicon Motorspeedway have appeared, along with NASCAR chassis-on-a-platforms following the Nextel Cup circuit.

The first part of motion simulation involves your inner ear, that is, the vestibular system. To put it simply, our inner ears are filled with fluid. Our brains interpret the orientation of that fluid within our ears to decipher the rotation or acceleration we're experiencing.

The trick is that our brains, in the absence of external visual input, can't tell if we're lying on our backs, or accelerating forward at 1g. So, a motion simulator works by replacing "real" acceleration with the force you feel from gravity:

The second essential element of what we do at Force Dynamics involves the platform itself: How it performs, how it’s built, and how those aspects of it differ from the competition.

To provide any motion cues, the platform has to move. To accomplish this, three Force Dynamics-built ball-screw based linear actuators are driven by a networked 3-axis digital servo drive. The actuator motors provide 3hp peak and 500lbs of peak thrust each; each actuator has 18” of travel.
The trapezoidal strut shape, unique in the industry (Is this true?), provides bracing, bridge-style, against the large lateral loads experienced during fast moves, allowing the machine to move faster and more reliably over time than comparable machines with standard tubular struts.

Once the actuators move the platform, it has to move in a convincing and comfortable way. The 301’s raised center of rotation provides superior onset cueing compared to existing motion systems, and reduces parasitic forces that cause motion sickness. Informally observed, fewer than 1% of riders experience motion discomfort in the 301.

A secondary characteristic of the 301’s ‘sunken seat’ design is small size and ease of entry: Other platforms with the 301’s range of motion are nearly twice as tall, and require ladders or platforms for entrance and egress. To get into the 301, you sit down.

Now that the platform is moving in a convincing manner, it has to be in tune with the software simulation that provides the environment for the rider. In the 301, Ethernet-based servo system provides near instant reaction to in-game events, and allow for extremely high small-excursion bandwidth.

Rather than having the super-soft ‘Magic Carpet’ ride common with other small motion systems, the 301 can physically recreate engine vibrations, pavement texture, and high frequency suspension vibrations with appropriate software. This small ‘texture’ of the simulation is at least as important for rider experience as the overall feel of things. Imagine watching a movie badly focused: You can tell what’s happening, but it’s not a very compelling experience. The 301’s tight response results in a tightly focused, immersive simulation.

Competing small systems from arcade manufacturers, based on hydraulics or slow servo drives, can take up to half a second to respond to input, and overshoot commanded positions, resulting in what is best described as a ‘muddy’ or distorted ride, the motion platform equivalent of speakers being played far too loudly. The 301 goes where it is told immediately, and stops when it gets there, resulting in a clear, clean, and engaging rider experience.

Now that the platform is working well, it needs to be told what to do. Force Dynamics’ Windowsbased control software requires only Ethernet (no PCI add-on cards) and updates are available online. Its easy-to-use interface allows precise control of simulator characteristics, including scaling of output, softening filters, and per-game settings.

Additionally, the 301’s open support API allows for the easy addition of software support; the machine is not dependant on one piece of soon-to-be obsolete software. The ease with which additional software can be programmed to support the platform means that the system can simulate boats as easily as cars, planes as easily as boats, and large, heavily armed walking robots as easily as planes.

This wraps back around to what the 301 is, finally, in one sentence: The 301 is a high fidelity, low-cost machine that brings the user inside whatever arcade game or simulation is running by making the simulated forces and impacts real.

"The maximum static load is 475 kg per machine including the rider. The dynamic loads can reach 500 kg over a 1 to 3 Hz bandwidth. We estimated the dynamic loads from observing the deflections of the isolation mounts during operation. The dynamic loads can occur on any of the four feet and can shift rapidly between them. The response of the isolator is lenear and has a rate of 270 kg/cm if you wish to confirm our estimates."