What is in this article?:
- Joysticks Maintain Control of Brute Strength
- Non-contacting types
Continuing evolution keeps joysticks the most intuitive means to interface man with machine.
The advent of hydraulics allowed controlling much higher levels of power via valves. A hydraulic joystick connects directly to low-pressure ( pilot) hydraulic valves, allowing an operator to control the high-pressure "working side" of the hydraulic system. The benefits of hydraulic joysticks over mechanical linkage or cable systems include simpler installation for complex control applications, the ability to substantially increase power, and minimize maintenance. As with mechanical controls, another significant advantage is the ability of the operator to feel any force feedback through the joystick.
The disadvantages of pilot valve joysticks are the close proximity of pressurized hydraulic fluid to the operator, the temperature effect on hydraulic fluid performance, and the considerable cost of routing multiple hydraulic lines throughout the system.
Hydraulic pilot valve joysticks gained widespread use on construction equipment, aerial work platforms, and forklifts. When this was the state-of-the-art technology, hydraulic joysticks were used in most applications of this type, because the advantages over mechanical linkages were many.
As technology of other control alternatives has advanced, the hydraulic joystick still maintains a competitive position in smaller equipment where the compactness of the hydraulic system minimizes the cost of fluid power transmission. The first applications to venture into the newer technology of electric joysticks have been larger equipment with extensive hydraulic systems. With long hose and tube routings and operators at a considerable distance from the working end of the equipment, these applications have the most to gain from electric joystick technology.
Most electric joysticks operate on low-voltage DC circuits and can be located a long distance from the electrohydraulic valve they control. Wiring from the joystick to the valve is much easier and costs only a fraction of what would be required to route hoses and tubes from the joystick to the hydraulic valve. This allows the freedom to design a more ergonomic operator station without compromising the cost of the equipment. The primary disadvantage as compared to a manual or pilot-operated valve is the higher cost of the electrohydraulic valves.
Electric joystick types
Electric joysticks are manufactured in a wide variety of types, ranging from large hand-operated displacement and force controls to very small finger-operated devices. Each has its own niche application. Joysticks can be further classified into discrete control, which use switch contacts, or proportional control, which use potentiometers (pots), digital encoders, rotary variable differential transformers. Each has its own niche application. Joysticks can be further classified into discrete control, which use switch contacts, or proportional control, which use potentiometers (pots), digital encoders, rotary variable differential transformers (RVDTs), induction coils, or Halleffect devices. Force (nondisplacement) controls primarily use induction coils or strain gauges as output devices. Small finger-operated joysticks are also made in displacement and force types. Displacement joysticks in this category generally use potentiometers and Hall-effect devices for proportional output and microswitches for discrete output.
Switching-type joysticks use high current and voltage mainly on equipment that requires stepped, discrete control of a motor drive. At the other end of the spectrum are finger-operated joysticks that control microswitches. These are often used as simple discrete (bang-bang) controls — one switch closure in each direction — for single-speed directional control.
The most-common use of a joystick is for proportional control of machinery through an electric motor control, electrohydraulic valve, hydraulic pump or computer.
Encoders and RVDTs are highly reliable, non-contacting 