Grips for off-road vehicles, such as this handle designed for agricultural use, combine ergonomic shape, specific button/switch placement and multifunction switches to maximize both utility and comfort.
Depending on the vehicle type and the number of tasks it performs, a joystick grip for off-road vehicle operation can come in all shapes, sizes, and levels of functionality.
This multifunction joystick grip model mounts into the armrest of an off-road vehicle, providing significant ergonomic benefits to the operator. Functions can be grouped according to the frequency with which tasks are performed and to minimize hand movement.
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For eight hours or more a day, combine operators sit in their cabs performing numerous tasks with the pull of a handle, the flick of a switch, or the press of a button. Depending on the type of the equipment they use, operators need only a single, multi-function joystick grip to accomplish many of these tasks. Innovations in joystick design for combines and other off-road vehicles have dramatically increased their versatility, with as many as 20 functions possible from a single device.
The repetitive actions common to joystick grip control combined with the long hours of continuous use take their toll on the operator. In the past several years, off-road vehicle manufacturers have received steadily increasing feedback from their customers about the importance of ergonomics. That feedback has helped multifunction-grip designers develop new models that maintain or increase functionality while reducing the hand motion required to operate the device, which makes it more comfortable to use.
Peter Leuty, Product Manager, Control Assembly, and Ron Celander, Product Development Engineer, Control Assembly, both of ITT Industries, Cannon Switch Products, recently discussed the evolution of joystick grip design in off-road vehicles.
Sculpting blocks of plastic—When joystick grips were first introduced for use in off-road vehicles, they were designed for basic functionality. The grip's shape was a secondary concern.
"The older designs were somewhat blocky," said Leuty. "They made performing tasks more convenient, but there wasn't much ergonomic consideration to the way they were shaped."
From its origins as a chunky block of plastic, the grip has evolved into a comfortable instrument that can be contoured to fit the right or left hand of an operator. ITT has integrated a palm rest into the design, angled in a way that favors the hand in use. Exactly how many left- or right-handed models are produced is driven by market demand. Future designs in development at the company will allow the grip to be used easily by either hand.
Integrating a palm rest into the joystick grip design helps the vehicle operator stave off fatigue. However, not everyone's hand is the same size; a "one size fits all" grip does not completely accomplish the goal of improved ergonomic design. Grip designers have addressed this problem by making the size and length of the device adjustable, so operators can fit it to their own hand. Grips can also be designed at an angle so the operator's hand rests comfortably alongside the instrument while performing tasks. Another factor determining the size of a joystick grip is the number of functions that off-road vehicle customers want to have integrated into the device.
"There can be some manufacturing limitations that come into consideration when you increase the functionality of these grips," said Celander. "Some of the shapes of grips that our customers request are shapes that simply cannot be manufactured. In other cases we can build the grip to their specifications, but we run into issues where the parting lines of the two halves of the grip meet. In those cases, we try to avoid designs where the two halves come together near any critical area of the grip, where the operator's hand or fingers might be affected."
The finer points of fingertip control—The latest advancements in grip design allow designers to build many functions into a joystick grip while preserving its ergonomic features. A lot of time, thought, and testing has gone into the successful combination of form and function.
According to Celander, "Too many functions could affect the ergonomic design of the grip. Fortunately, we haven't run into any problems like these yet."
"The maximum number of functions we can build into a grip is driven by accessibility to the operator and space limitations," said Leuty. "Using multifunctional switches, we can create a grip that can accomplish up to 20 functions. Any number higher than that, and operators have to switch their concentration from the task they are performing to the grip itself, so they can search to find the buttons."
Whether or not the operator can keep their eyes on the task at hand and off the grip is also greatly affected by where those switches are placed. Grip designers arrange the switches and buttons according to the frequency of their use, placing the most frequently used in proximity to where operators would place the thumb and index finger. They also pay close attention to the spacing of the switches to avoid situations where an operator presses the wrong control.
"Spacing between adjacent switches must take into account several considerations," said Leuty. "You do not want to cause any unnatural movement of the actuating finger or thumb, or place a switch out of the reach of the operator."
Another concern affecting switch placement is the environment in which the grip will be used. For example, if operators have to wear gloves to complete tasks, their ability to work efficiently can be diminished by switches placed too closely together. According to Celander, typical spacing is about 20 mm (0.8 in).
Once the operator determines where the buttons and switches are and what they do, and has no trouble distinguishing between each one's location on the grip, it helps even more if they are easy to actuate. To address this concern, grip designers consider several factors regarding the size and shape of buttons, including:
- Where the button or switch is positioned on the grip
- The type of switch actuation
- Whether graphics or illumination are required
- The proximity of adjacent switches.
"One must also avoid any sharp edges or high pressure points that will cause discomfort to the operator," said Celander. "Switches that require more finger movement by the operator are typically placed higher on the grip than those that require very little movement. This helps minimize any unnatural movement of the actuating finger or thumb."
Once a button has been properly sized and shaped, it must also be easy to actuate. "Actuation forces in the range of 5 N (1 lb) are preferred with a switch travel of 1 mm (0.04 in)," said Leuty. "This provides the operator with 'tactile feedback' that they have actuated the switch. Such tactile feedback is especially important in high-vibration or noisy operating conditions." To avoid fatigue, a lower force may be preferred in applications requiring frequent actuation.
Additional features—Joystick grip designers have been adding several other ergonomic features to help improve the productivity and efficiency of off-road vehicle operators. These include:
- Soft-touch over-molding for a more comfortable grip
- Backlighting on the grip to make the buttons easier to see
- Function activation indication to let the operator know that the proper function is enabled
- Texturing of the grip surface to make it easier to grip the device with or without a glove.
"The more feedback we receive from our customers about the ergonomics issues that matter to them, the better," said Leuty. "These customers don't just want to go to a supplier and buy a stock unit off the shelf. They want equipment that maximizes comfort while improving productivity."
For more information from ITT Cannon, visit www.ittcannon.com or circle 410.
SAE Off-Highway Engineering April 2000
