I thought I would begin this series of articles on racing motion simulation as I, myself have been researching simulators for some time now. I’ve learned quite a bit along the way. So I thought I would share what I’ve learned in hopes that it may help you in search of adding motion to your immersive racing or flying experience.
First things first; So what exactly is a motion simulator?
While there are a lot of types of motion simulators at present, and more being developed every day, we’ll focus on motion platforms in this article. You can think of a motion platform as simply a table in essence. This table can tilt, slide back and forth or move up and down, or in combinations of these motions. You would secure a seat, racing cockpit or flight simulation cockpit to this platform. For more information on what a cockpit is, you can find an excellent article on this site which goes into more detail on these cockpits. The motion simulator moves in certain ways to represent the motions you would experience in a game or simulation. So if you are piloting an airplane or driving a car, the motion simulator would move to represent what the airplane or car is doing.
What is DOF?
when looking at motion simulators, one of the first things you’ll notice is numbers of DOF. What does this mean? DOF stands for Degrees of Freedom. This is how many ways that a particular motion sim can move. So when you see 1 DOF, the sim can move back and forth in one direction or around one axis. If you see 2 DOF, then the sim you’re looking at has 2 degrees of freedom and can move in two different ways.
Let’s look at this a little more. The maximum degrees of freedom of a current motion simulator is 6 DOF. This means that a sim with 6 degrees of freedom can represent all movements in 3D space. So it would be able to move you forward and backward, side to side, up and down and rotate you a certain amount around three different axes.
These axes are pitch, roll and yaw. For those familiar with flight simulators, you may already be familiar with this type of angular description and motion. For those interested in racing, what are these axes and how do they fit in?
Pitch
The first axis of rotation we’ll discuss is called pitch. Simply put, pitch is perceived when you lean forward or backward. You would experience pitch when driving a car over a rise or down a hill, for example. So if you are seated in a motion simulator, you would feel pitch when the front of the platform moves down and the back moves up. The opposite is also true. If the back of the platform moves down and the front moves up, then that also represents pitch. So when looking at the information on a given motion simulator, you might see this shown as + / – 10 degrees. This means that the sim can rotate on this axis in a range of 20 degrees; 10 degrees down and 10 degrees up. So if the front of the platform moves down as much as it can, it will have rotated down by 10 degrees. The back of the platform will have moved up by that much. So this simulator would be able to represent motion on the pitch axis in a range between 10 degrees up and 10 degrees down. This may not sound like a lot, but if you think of how it would feel to have the floor of the room you are in now, tilting up or down in front of you, even a little bit, you would surely notice it. 🙂
Roll
Roll is another axis that a motion simulator may represent. You can feel the roll motion when you lean from side to side. So in a motion sim, it would either move the left side down and the right side up, or vice versa. You may feel this type of motion when traveling around a turn in a car. The simulator may lean toward the outside of a turn to let you feel the added G-forces throughout the turn, similar to what you would feel in a real car. The sim may also lean left or right to simulate the banking of a track surface. As above, you may see this motion represented with a range like 20 degrees or + /- 10 degrees. Both these measurements mean that one side of the platform is capable of moving up a total of 10 degrees or down a total of ten degrees, and the other side of the platform would move accordingly.
Yaw
Yaw is a bit more complicated when it comes to motion simulation. To put it simply though, you can feel yaw when you turn in place. So if you are standing, facing north, and you turn in place so that you are now facing west, that is yaw. In a motion sim, you would feel this sensation as you rotate left or right. In a car, you may feel yaw as you turn, spin or as the back of the car slides left or right as you lose traction. Motion simulators designed for flight simulation and racing simulation may have different ways of giving you the sensation of yaw. For flight sims, the pivot point in the simulator might be more toward the middle of the motion platform or close to where you are sitting. For racing sims, the pivot point for the yaw motion may be toward the front of the motion platform, or closer to where your feet are. So while all of these different scenarios will give you the sensation of yaw, you may feel it in different ways, to represent the way different vehicles behave. A plane will move differently than a car would. As we mentioned, one way you can feel yaw is when the rear of your car loses traction. So this is why some motion simulators designed for racing will have a pivot point for this angle toward the front of the motion platform. This can more accurately represent the way you would feel the car behave in real life. So if a particular motion simulator is capable of yaw, You may see this called traction loss in the information on that simulator.
So let’s focus on racing now for just a minute because there are some specific terms you may see if you are looking at racing simulators. Remember that above we mentioned that some of the motions that a sim can do are to move you back and forth, up and down etc? These motions have names in regard to racing simulation.
The motion of you moving straight forward and backward is called surge. You would feel surge when you press the accelerator to speed up or start your car moving forward from a stop. Simulators also may use this forward and back motion to represent shifting gears or the car slowing down when you brake. Some simulators also represent this motion using pitch. So the platform may tilt forward or backward to simulate the G-forces you would feel as you accelerate or decelerate. You may also feel a quick surge motion if you impact an obstacle as you drive or race.
The motion of sliding side to side is called sway. Some simulators use this motion to exaggerate the sensation of your car turning. So you may feel the sim moving to the outside of a turn as you travel through it. Some sims also use roll to simulate the sway motion. You may also feel an abrupt sway motion if you contact an obstacle at the side of your car.
Lastly, we have the straight up and down motion. In racing motion simulation, this is called heave. Heave can represent crests, bumps or dips on a track or even catching air as you drive your car over a rise.
So to sum up everything we’ve been talking about in this article, and hopefully make some sense of all this, let’s look at what you may see as you look at racing simulators in the wild. If you see a sim that says that it has 3 DOF, with pitch, roll and heave, we now know exactly how this sim can move and what it may be capable of representing to us as we drive. This sim would most likely be able to represent driving up or down hills, the car accelerating or decelerating, turning, swaying and traveling over bumps or catching air. Now how much does this sim move? Well, if we see that it has a range of 25 degrees, we can tell that it can most likely move up or down by 12.5 degrees in pitch or roll. If we see that this sim has a range of + / – 55 mm, we have a good idea that this refers to the heave distance that the sim can perform, or how far the platform can move up or down.
Unfortunately, seeing just a number of DOF on its own will not necessarily tell us how a particular sim can move. It is still necessary to read a bit more on which degrees of freedom that that sim may actually have. One motion simulator may be able to simulate pitch, roll and yaw, for example and another may have pitch, roll and heave. Both of these sims would have 3 DOF but their degrees of freedom are different. So sometimes you may need to read a bit more information on a motion sim so you know exactly what it can do for you.
Though some of this may sound a bit complex, , I hope this article has given you a bit more information to help you on your way to better understanding motion simulation. There are many ways to add motion to your experience of racing and flying. I hope this article will help to get you started in your explorations so that you can have a truly fun and moving experience! 🙂