Aspects of dexterity and ergonomics have a significant influence on the design of assembly workstations. However, dexterity is usually only included in the process design when there are high fine motor requirements and is often neglected in the positioning of components, the design of control panels or the use of tools. An influence on the physical strain and an increased risk of accidents for left-handed people using a right-handed workstation has not yet been scientifically investigated. In the context of workplace design, a precise assessment of the strain on both hands when carrying out manual tasks using the key characteristic method is recommended.

However, methods that enable optimization for different manual skills have not yet been demonstrated. Human-robot collaboration is a pioneering technology that makes it possible to improve the ergonomics of manual assembly activities. Initial applications can demonstrate the potential for improving the ergonomics of lifting and holding activities, but do not take human dexterity into account either. Here, adaptive assembly processes offer the opportunity to make workflows more efficient and less stressful thanks to simple and intuitive robot programming options.

Handedness and collaborative working

With the aim of systematically investigating the factors influencing dexterity in human-robot collaboration, assembly tests were carried out with 50 test subjects at the Bremen Institute of Structural Mechanics and Production Systems (bime). In the experiments, which were designed according to scientific standards, the focus was on interaction with a collaborative robot during the execution of an assembly process. An assembly process is carried out in three variants. Variant A depicts a purely manual assembly, variant B primarily supports the right hand of the test participants and variant C, as a mirrored setup, primarily supports the left hand.

In order to optimally record the experiments, the results are recorded in the form of an observation sheet and the test subjects are asked to provide their subjective assessments via a questionnaire. In addition, images are recorded and analyzed using hand tracking and eye tracking systems.

Consideration for handedness increases added value

The evaluation of the tests shows that the number of non-value-adding handling activities can be significantly reduced if the test setup is adapted to the participants' handedness. In the test variants with robot support, a significant reduction in hand changes was achieved if the robot programming was optimized for the respective handedness.

Small components in particular are gripped preferentially with the dominant hand, while handedness is not decisive for gross motor processes. This effect can be observed equally in left-handed and right-handed test participants. If employees are supported in the process by a collaborative robot, this can also have a negative impact on ergonomics if assembly processes are optimized for the wrong handedness.

Both the participants' self-assessment and the evaluation of the test data from hand and eye tracking show a deterioration in ergonomics for people with a dominant right hand at a workstation optimized for left-handedness.

Ergonomics for the well-being of employees

In summary, it can be said that taking hand position into account can have a positive effect on the ergonomics of assembly workstations and the well-being of employees. Particularly in the area of collaborative assembly, where humans and robots work on an assembly object at the same time, taking handedness into account can be crucial. Adaptive robot programming can prevent collisions, reaching or working in non-ergonomic postures.