There are a couple of big problems with the conventional analog joystick system. First of all, the crude analog-to-digital conversion process isn't very accurate, since the system doesn't have a true analog-to-digital converter. This compromises the joystick's sensitivity somewhat.
Second, the host computer has to dedicate a lot of processing power to regularly "poll" the joystick system to determine the position of the stick. This takes a lot of power away from other operations.
Next, let's take a look at how designers have addressed these problems to date.

New Additions

Joystick manufacturers have addressed these problems in a couple of different ways. One solution is to add a sensitive analog-to-digital converter chip in a specialized game adapter card or in the joystick itself. In this system, the converter spits out digital information directly to the computer, which improves the accuracy of the stick and reduces the work load on the host processor. These new joystick models can usually connect to USB ports, which also improves speed and reliability (see How USB Ports Work for details).
Another solution is to skip the analog potentiometer technology all together. Many newer controllers use optical sensors to read stick movement digitally. The diagram below shows one common system.

In this system, the two shafts are connected to two slotted wheels. Each wheel is positioned between two light-emitting diodes (LEDs) and two photocells (the graphic only shows one photocell, LED pair for simplicity's sake). When light from each LED shines through one of the slots, it causes the photocell on the other side of the wheel to generate a small amount of current. When the wheel rotates slightly, it blocks the light and the photocell doesn't generate current (or it generates less, anyway).
When the shaft pivots, it spins the wheel, and the moving slots repeatedly break the light beam shining on the photocell. This causes the photocell to generate rapid pulses of current. Based on the number of pulses that the photocells have generated, the processor knows how far the stick has moved. By comparing the patterns coming from both photocells monitoring one wheel, the processor can figure out which way the stick is moving. This is the same basic system used in many computer mice. (Check out Electronics Circuits Reference Archive for more information.)
One of the biggest additions to the world of joysticks is force feedback technology. In the next section, we'll find out how these joysticks let you experience the game on a new level.


Force Feedback

The basic idea of a force feedback joystick (also called a haptic feedback joystick) is to move the stick in conjunction with onscreen action. For example, if you're shooting a machine gun in an action game, the stick would vibrate in your hands. Or if you crashed your plane in a flight simulator, the stick would push back suddenly.
Force feedback joysticks have most of the same components as ordinary joysticks, with a few important additions -- an onboard microprocessor, a couple of electrical motors and either a gear train or belt system. The diagram below shows one simple design.

The X-axis and Y-axis shafts connected to the stick both engage a belt pulley. The other end of the belt for each axis engages a motor's axle. In this setup, rotating the motor axle will move the belt to pivot the shaft, and pivoting the shaft will move the belt to rotate the motor axle. The belt's function is to transmit and amplify the force from the motor to the shaft.
Both an electrical signal from the onboard processor and the physical movement of the joystick will rotate the motor axle. In this way, you can still move the joystick even when the motor is moving it.
On the opposite end of the motor, the axle is connected to the joystick's position sensors (its potentiometers or optical sensors, for example). Whenever the stick moves, whether due to the motor or the player, the sensors detect its position.
The joystick has a built-in ROM chip that stores various sequences of motor movement. For example, it might have a machine gun sequence that instructs the motors to rapidly change direction, or a bazooka sequence that instructs the motor to shift the joystick backward suddenly and then forward again. The game software requests a particular sequence, and the computer transmits the request to the joystick's onboard processor, which brings up the appropriate data from its own memory. This reduces the work load on the computer and makes for faster reaction times.
As joysticks continue to evolve, manufacturers will take force feedback technology to whole new levels. This is great for avid gamers, of course, but it could also have a big effect on the rest of the population. Force feedback controller technology could lead to significant changes in industrial machinery, wheelchairs and other equipment for handicapped people, and even medical care. Researchers are also developing force feedback controllers to let people "feel" the Internet as they surf.
The possible applications are endless! In the future, joysticks could be as ubiquitous as computer keyboards are today.