Design of an ergonomic control lever for wheel loader attachments

6 Analysis
This chapter contains a deeper analysis of the human-machine system, the users and the tasks in order to
understand how wheel loader tasks affect the user. A physical ergonomic analysis was performed, using
an anthropometric analysis, ergonomic simulation and subjective analysis, to analyze the current linear
control levers and to find a basis of recommendations to use when designing the single lever. A cognitive
ergonomics analysis was performed to get a deeper understanding of the context of wheel loader usage,
defining the human senses and multimodality and analyze the mental model of machine operators.
6.1 Human-machine system description
The wheel loader and operator are most often a part of a team that interacts with other
parts. These parts, or components, are working together to accomplish a common goal.
This is in line of the system theory (chapter 3.2.3). Therefore a system description is used
as graphical instrument in this project, to summon the important system boundaries, the
components and the communication between included elements.
The wheel loader and the human
The reason wheel loaders exist is to perform a main process and fulfill a certain goal. In
this case that is regarded to be excavating, and transferring of, rather heavy matter. This
is only possible when a human operator interact with the wheel loader, makes decisions,
communicates with co-users and also the opposite; this is only possible for the human by
using the machine.
The wheel loader and human operate in an environment, that exists outside the drawn
system boundaries (Sanders & Maccormic, 1993), (figure 6.1). As the environment only
shares relations of input and output with the system, the system in this case is defined as
an Open System according to Flood & Carson (1993). The environment is, in a common
application, the world outside a gravel pit business. This outer part of the system
described is the work organization with staff management that commands tasks to be
performed. The narrower system of interest where the human interacts with a machine is
the users work situation in the wheel loader. The operator is essentially in control of all
available functions of the wheel loader, can be considered a Mechanical System (Sanders
& Maccormic, 1993).
The user receives a task or order to be performed from the staff management. Often the
user communicates with a co-user by audial or visual means and uses instruments and
controls in the machine to perform the task. The physical barrier and interface are the
windshield and the instrument panel for visual information, audial communication
equipment, the control levers for controlling hydraulic functions, and various buttons
among other things that the user needs for perceiving and acting in the situation. The
user’s body will also receive and percept information through the machine itself, carried
by vibrations and sound.
Conclusion system description
Commonly there are physical factors that affect or interfere the operator’s use
performance and relation to the control levers and other interface. Such factors can be
large full body vibrations disrupting e.g. the visual perception and affects the motoric
control. Sitting in a seat for long working sessions, and the frequent use of joystick or
levers, cause static workload.
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