By Josh Cosford, Contributing Editor
A joystick is a type of lever used to control multiple valves or functions with a single control. It can be tilted fore and aft, and also left and right, but is often also equipped with electric or electronic buttons, switches or proportional rollers. So how do you choose a joystick for your mobile machine?
You must first understand your machine and whether it has the capacity to use cable, hydraulic, electric or a combination type of control. Each choice depends on the nature of your machine or the scope of complexity you’re planning to build.
The most basic form of joystick controller uses cable and spring mechanisms connected to the bottom of the stick. The cables are aircraft wire surrounded by hard plastic covers, allowing the cable to slide to and fro inside the protective cover. The opposing ends of the cables are fed through or around the body of the machine to a directional control valve, with each cable terminating at the valve spool in place of levers.
As the joystick is tilted forward, for example, it will pull a cable which in turn pulls on the valve spool, shifting to control the valve’s function, most often a boom, bucket, tilt or swing on an excavator, but can be any function requiring remote, repeated manual control. Cable operated joysticks are the most economical and are best suited to small machines or implements, such as backhoe attachments for a tractor. They’re also a solid choice if you’re adding a joystick control to an existing machine since the cable operators can be added to the current valve, as all the major valve manufacturers offer cable operator attachments.
The next option for hydraulic control, especially for large OEMs with advanced hydraulic componentry is the pilot operated hydraulic control. A pilot pump supplies medium pressure hydraulic energy into one or more joysticks inside the cab of the machine. The joysticks are essentially spool pilot valves, where their work port energy is fed to the opposing sides of the main stage valves of the primary machine functions, such as the boom, arm and bucket.
Hydraulic joystick control makes sense for large machinery, especially with high flow and pressure. Cables would be difficult to operate with such high flow forces inside the main function valves, so pilot energy more easily moves the main stage valves in these large machines. The downside is their complexity, which is why only larger, more complex machines tend to use them. However, even though hydraulic pilot joysticks are powerful, smooth and effective, they are losing ground to electronic control.
Electronic joysticks create analog electrical outputs, such as 4-20 mA or 0-5 V, for example, which is fed to either a proportional valve controller or the primary machine controller. The controller uses a PWM output to control proportional valves directly or via proportional pilot valves, which in turn control the major functions of the machine.
Advanced electronic machine control now operates through Controller Area Network (CAN) systems, and the joystick is just a node of many, where they use one of the various standards such as SAE J-1939 to join all components to the primary machine controller, or one of many smaller units. CAN systems allow the use of just four wires to transmit control signals throughout the entire machine, reducing cost and complexity.
In reality, some joysticks will use a combination of controls, such as a hydraulic pilot control of an excavator, but with an electronic proportional roller switch for controlling an optional function, such as a thumb attachment to the excavator’s boom. However, with the reduced cost of electronic control, it’s now easy for even small manufacturers to offer fully electro-proportional control of machine functions, with economical choices of electronic joysticks.