Motion platform
From Wikipedia, the free encyclopedia
A motion platform is a type of amusement ride with a seating platform remaining parallel to the ground while being moved in a circular motion along a vertical plane. Motion platforms found in a traveling carnival include the "Yellow Submarine." Larger scale motion platforms include "Air Time" at Carowinds, "Corkscrew Hill" at Busch Gardens Williamsburg, "The Amazing Adventures of Spider-Man" at Islands of Adventure, Star Tours at Disney MGM Studios and Mission: Space at Epcot Center.
A motion platform can also be called a motion base, a motion seat, or a motion simulator among other things. The primary function of a motion platform is to provide realistic physical movement for one or more occupants. The movement is synchronous with visual display and is designed to add a tactile, or sense of touch, element to video gaming, simulation, and virtual reality. When motion is applied and synchronized to audio and video signals, the result is a combination of sight, sound, and touch. Such a combination is typically found in a flight or racing simulator. Motion, some claim, is the most significant factor affecting the realism of a simulation.
Motion and simulation, traditionally applied to racing sim and flight sim, have long been associated with one another. Motion is being applied to an increasing variety of video gaming applications however. Visit any modern video game arcade and one can plainly see that gaming in motion is everywhere. Motion applications have moved beyond auto racing and flight sim to include boats, motorcycles, rollercoasters, tanks, ATVs, and spaceships among many other craft types.
Motion platforms can provide movement on up to six (6) degrees of freedom. The six (6) possible degrees of freedom are broken into two categories of motion – rotational motion and linear, or translational, motion.
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[edit] What Impact Does Motion Have on Simulation and Gaming?
The use of physical motion applied in flight simulators has been a debated and researched topic. The Engineering department at the University of Victoria, conducted a series of tests in the 1980s, to quantify the perceptions of airline pilots in flight simulation and the impact of motion on the simulation environment. In the end, it was found that there was a definite positive effect on how the pilots perceived the simulation environment when motion was present and there was almost unanimous dislike for the simulation environment that lacked motion.
The aspects of game play can be associated with your basic human senses – traditionally sight and sound. The video game makes a sound, and the sound is heard. The game shows a racecar hugging a curve on the video output screen and the user sees the car taking the curve. A few recent years ago, a couple of small lopsided motors were inserted into the common game controller. The idea was to add a feel sense to the sight and sound of game playing. When the car crashes into the wall, the controller motors spin and the “driver” of the car, in this case the game player, feels vibration in response to the car crashing. This vibration coupled with the sight and sounds of the car crashing was designed to enhance the user experience by allowing the gamer to feel the game. A motion platform takes the next step by providing the player a full body touch sensation. Plug in your racing game, sit in a motion gaming chair, and you will see, hear, and feel like you are driving a virtual car. The motion chair can roll you left and right as you turn corners and pitch you forward and backward as you accelerate and decelerate. Motion platforms provide for a much more realistic gaming experience, a virtual gaming simulation, and allow for even greater physical complementation to sight and sound game play.
A conclusion that could be drawn on the findings of the University of Victoria study is that the realism of the simulation is in direct relationship to the accuracy, or realism, of the simulation on the pilot. When applied to video gaming and evaluated within our own gaming experiences, realism can be directly related to the enjoyment of a game by the game player. In other words – motion enabled gaming is more real, therefore it is more fun.
[edit] Different Types of Motion Platforms
Motion platforms historically have spanned a broad spectrum in scale and cost. Those in the category of amusement park rides and commercial and military aircraft simulators are at the high end of this spectrum with arcade style amusement devices falling into the middle of the spectrum while small and affordable home based motion platforms comprise the low end.
The high-end motion platform has been used in conjunction with military and commercial flight instruction and training applications. However, today you will find multiple occupant entertainment applications in theme parks throughout the world. The systems used in these applications are very large, weighing several tons typically housed in facilities designed expressly for them. As a result of the force required to move the weight of these larger simulator systems and one or more occupants, the motion platform must be controlled by expensive hydraulic or electromagnetic cylinders. The cost of this type of motion platform exceeds $100,000 US dollars, and often goes well into the millions for a multi-occupant system found at major theme park attractions. The complexity of these systems require an extensive amount of programming and maintenance, which further extends the cost associated with this type of motion platform.
The middle of the spectrum includes a number of disclosures involving powered motion platforms aimed at arcade style amusement games, rides, and other arrangements. These systems fall into a price range from $10,000 to $99,000 USD. Typically the space requirements for such a platform are modest requiring only a portion of an arcade room and the motion is provided via similar, less expensive, control systems than the high-end platforms.
The low end system includes home-based motion platforms, which have recently become a more common device used to enhance video games, simulation, and virtual reality. These systems fall into a price range from $1,000 to $9,000 USD. Within the past ten years, several individuals and business entities have developed these smaller, more affordable motion systems. Most of these systems were developed mainly by flight simulation enthusiasts, were sold as "Do-It-Yourself" projects, and could be assembled in the home from common components for around one thousand US dollars ($1,000). Recently, there has been increased market interest in motion platforms for more personal, in-home, use. The application of these motion systems extends beyond just flight simulation into a larger market comprised of a more generalized "Craft-Oriented" video game type. SimCraft, an Atlanta Georgia based company, envisions that motion platform devices will eventually become a common component to the enthusiastic gamers system.
[edit] How Human Physiology Processes & Responds to Motion
The way we perceive our body and our surroundings is a function of the way our brain interprets signals from our various sensory systems, such as sight, sound, and touch. Special sensory pick-up units (or sensory "pads") called receptors, translate stimuli into sensory signals. External receptors (exteroceptors) respond to stimuli that arise outside the body, such as the light that stimulates the eyes, sound pressure that stimulates the ear, pressure and temperature that stimulates the skin and chemical substances that stimulate the nose and mouth. Internal receptors (enteroceptors) respond to stimuli that arise from within blood vessels.
Postural stability is maintained through the vestibular reflexes acting on the neck and limbs. These reflexes, which are key to successful motion synchronization, are under the control of three classes of sensory input:
- Proprioceptors
- Vestibular System
- Visual Inputs
[edit] Proprioceptors
Proprioceptors are receptors located in your muscles, tendons, joints and the inner ear, which send signals to the brain regarding the body's position. An example of a "popular" proprioceptor often mentioned by aircraft pilots, is the "seat of the pants". Proprioceptors respond to stimuli generated by muscle movement and muscle tension. Signals generated by exteroceptors and proprioceptors are carried by sensory neurons or nerves and are called electrochemical signals. When a neuron receives such a signal, it sends it on to an adjacent neuron through a bridge called a synapse. A synapse "sparks" the impulse between neurons through electrical and chemical means. These sensory signals are processed by the brain and spinal cord, which then respond with motor signals that travel along motor nerves. Motor neurons, with their special fibres, carry these signals to muscles, which are instructed to either contract or relax.
In other words, these sensors present a picture to your brain as to where you are in space as external forces act on your body. For example, picture yourself sitting at a red traffic light in your car. The light changes to green and your foot presses the accelerator. As you accelerate away from the traffic light, you will "feel" yourself being pushed back in to the seat. That experience is transmitted to your brain via the proprioceptors, in particular, through the sensors in your backside and back. The brain interprets this information as an acceleration in the forward sense. If you now slam on the brakes to stop suddenly, you will find different proprioceptors at work. The deceleration will be felt through your hands and feet and your backside will now be trying to slide forward in the seat. This information is again presented to your brain and thus it interprets the deceleration taking place. In turn, the brain now signals the muscles in your arms and legs to contract and stop you from sliding forward in the seat. A similar sensation will take place when you turn a corner. If you turn left, your body will slide across the seat toward the right and vice versa for a turn to the right.
The downfall with our internal motion sensors is that once a constant speed or velocity is reached, these sensors stop reacting. Your brain now has to rely on visual cues until another movement takes place and the resultant force is felt. In motion simulation, when our internal motion sensors can no longer detect motion, a “washout” of the motion system may occur. A washout allows the motion platform occupant to think they are making a continuous movement when actually the motion has stopped. Since there are restrictions on the range of motion for any motion platform, there are some movements which it cannot physically complete. When the craft is turning around completely, for instance, the motion system completes the first part of the turn and then slides the platform back into the neutral platform position. The old position data is thus "washed out". In other words, washout is where the simulator actually returns to a central, home, or reference position in anticipation of the next movement. This movement back to neutral must occur without the occupant actually realising what is happening. This is an important aspect in motion simulators as the human feel sensations must be as close to real as possible.
[edit] Vestibular System
The Vestibular System is the balancing and equilibrium system of the body that includes the vestibular organs, ocular system, and muscular system. The vestibular system is contained in the inner ear. It consists of three semicircular canals, or tubes, arranged at right angles to one another. In space, there are three planes that we can move through, forward/backward (longitudinally), left/right (laterally), and up/down (vertically), and there is one canal assigned to detect movement in each plane. Each canal is partially filled with fluid and has a series of hair follicles which stand vertically inside each tube. The fluid indicates rotation in the yaw, pitch, and roll axes. When acceleration takes place in a particular direction, the fluid in the appropriate canal is displaced which in turn causes the hair follicles to move. The movement of the hairs is interpreted by the brain as an acceleration. Three semicircular canals are orthogonal and deal with angular turns. The saccule with vertical linear movement, the utricle with horizontal movement.
There is however a short coming to this clever piece of biological engineering. If sustained acceleration (10 - 20 seconds) takes place in one direction, the fluid in the appropriate canal also remains continually displaced. As a result, the hair follicles will eventually return to the vertical position and the brain will perceive that the acceleration has stopped. In addition, there is a fixed acceleration threshold when the semicircular canals cannot sense any motion at all. During rotational motion, spatial disorientation can occur, (also referred to as “the leans”), when movement is below the threshold of sensitivity for the semicircular canal. This threshold of sensitivty is approximately 2 degrees per second. In other words, slow and gradual enough motion below the threshold will not affect the vestibular system. This fact allows the washout movement to be effective, as the vestibular system is unable to interpret continued or sustained acceleration. As long as the simulator moves at a speed below the threshold at which the human body can sense motion, the occupant will be totally unaware that this washout movement has taken place. During washout movements, our human sense of sight takes over and interprets the games visual output into the body and craft position.
[edit] Visual Inputs
Our eyes are the most important source of information in motion simulation. They send pictures to the brain about the craft's position, velocity, and attitude relative to the ground. As a result, it is equally important that the motion works in direct synchronization to what is happening on the video output screen.
When you roll the control to the left, your craft relative to the scenery displayed on the visual projector, also rolls left. Simultaneously you must also feel yourself, through the body's proprioceptors and vestibular system, turn to the left. If this doesn't occur in real time, motion sickness can occur.
[edit] Sources
- Moorabbin Flying Services – http://mfs.com.au
- .Response of Airline Pilots to Variations in Flight Simulator Motion Algorithms by Lloyd D. Reid and Meyer Nahon, AIAA Journal of Aircraft, Vol. 25, No.7, pp. 639-646, 1988.
