The basic idea of a force-feedback joystick (also known as a haptic-feedback joystick) is to associate the movement of the joystick with action on the screen. For example, if you're firing a machine gun in a combat game, the joystick will vibrate in your hand. Or, if your plane crashes in a flying game, the joystick will thrust back violently.
The force-feedback joystick has most of the same components as a normal joystick, with a few important additions: an onboard microprocessor, a couple of electric motors, and a gear train or belt drive. The figure below shows a simple design.
The X- and Y-direction axes connected to the joystick are both coupled to pulleys. The other end of the belt for each axis is coupled to the rotating shaft of an electric motor. In this mechanism, rotating the motor shaft moves the belt, which turns the directional shaft; rotating the directional shaft also moves the belt, which rotates the motor shaft. The belt serves to transmit and amplify the force from the motor to the directional shaft.
Electrical signals generated by both the on-board processor and the physical movement of the joystick cause the motor shaft to rotate. This allows you to move the joystick even as the motor moves the joystick.
At the other end of the motor, its shaft is connected to the joystick's position sensor (such as a voltage divider or optical sensor). The sensor detects the position of the joystick whenever it moves, whether that movement is caused by the motor or by the gamer.
The joystick has a built-in ROM chip that is used to store various motor action sequences. For example, there might be a machine-gun sequence that requires the motor to make a quick change of direction, or a bazooka sequence that requires the motor to suddenly move the joystick back and forth. The game software requests a particular sequence, the computer transmits the request to the joystick's on-board processor, which then reads the appropriate data from its own memory. This approach reduces the workload on the computer and facilitates faster response times.
As joystick technology continues to evolve, manufacturers will gradually take force feedback to a whole new level. This is certainly exciting news for gaming enthusiasts, but of course, it could have a big impact on other people's lives as well. Force feedback controller technology will revolutionize industrial machinery, wheelchairs and other disability equipment, and even medical care. Researchers are also developing force-feedback controllers so that people can feel the power of the Internet while surfing the web.
The possibilities for force-feedback technology are endless! In the future, joysticks will be as ubiquitous as computer keyboards are today.