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Displacement Joystick/Thumb Wheel Switch Control Profile for Precision and Jerk Free Speed Control Application in Open Loop System
Abstract:
Displacement joystick controls are considered as most suitable for manual controls wherever proportional outputs are required for dynamic applications such as when variable speed sensitivity or position are required. These joysticks are being used widely in both open loop as well as in close loop controls. The operator applies force to either the joystick itself or to its proportional linear displacement thumb wheel switches. This movement is then detected by either resistive or Hall Effect sensors, placed right inside joystick, and converted into an electrical signal. These joysticks, along with proportional linear displacement thumb wheel switches, find a wide range of applications in off-road vehicles such construction and forestry vehicles, harvester machines, and etc. for applications like attachment speed controls, boom position control, rotation speed control, and etc. The higher the displacement of the joystick, or its linear displacement thumb wheel switches, the better will be the control over the control parameter.
When it comes to open loop attachment control systems, where joystick displacement is directly linked with speed, most times the displacement provided by joystick or linear displacement thumb wheel switches is just not enough to fine tune the control parameter. In such cases, a small variation in displacement results in a large change in output parameter. The operator needs to move the joystick very slowly and cautiously to ensure fine adjustments in the control parameters.
It takes a good amount of time to learn to achieve these fine adjustments using a joystick. In a shaky environment it becomes even more difficult to precisely control the parameters using a joystick. In these conditions, a small variation in joystick displacement, or linear displacement thumb wheel displacement, leads to either over or under adjustment of the control parameter. When working in tight places, where there is not much space available to move the vehicle or attachment, it is necessary to control the joystick displacement or linear displacement thumb wheel displacement precisely to ensure objects around vehicle or attachment are not damaged. Due to an operator's mistake, or due to jerks and vibrations to joystick or linear displacement thumb wheel switches, a large amount of change can occur in the control parameter, erroneously leading to accidents or damage to the environment around the machine.
For accident and worry free operation, with better efficiency, an operator controlling such attachments or vehicles requires a means to adjust the sensitivity of the joystick or linear displacement thumb wheel switches. There are many ways to achieve this. For example, a switch can be provided to set & lock the upper limit of the control parameter to a level lower than its usual maximum. Reducing the upper limit reduces the effective range. In this way, normal displacement of the joystick or linear displacement thumb wheel switch will be converted to a relatively lower range of the control parameter. This gives the effect of reduced sensitivity.