Evaluating the Efficiency of Voice Control as Human Machine Interface in Production

Cars, mobile phones, and smart home devices already provide automatic speech recognition (ASR) by default. However, human machine interfaces (HMI) in industrial settings, as opposed to consumer settings, operate under different conditions and thus, present different design challenges. Voice control, arguably the most natural form of communication, has the potential to shorten complex command sequences and menu structures in order to directly execute a final command. Therefore, this contribution explored how differing HMI scenarios could possibly be optimized, by either replacing or complementing existing touch control interactions with voice control. Typical commands from CNC milling machines and industrial robots were categorized by their complexity, quantified by menu level and the necessary number of interactions. The collected interaction data showed that voice control can already provide a time efficiency advantage at either one additional menu level or three touchscreen interactions. For complex commands, such as those needing five menu levels and seven interactions on the touchscreen, the time efficiency advantage of voice control can reach up to 67 %. Furthermore, the study shows the possibility of reducing machine operator training times when using voice control by significantly lower interaction times for the first repetition of the participants. Note to Practitioners—Several publications investigate the ergonomics, usability, and cognitive load of classic mouse and keyboard control, button control, touch control, gesture control, gaze control, or voice control in specific interaction scenarios. All publications state that these factors need to be considered for the development of modern human machine interfaces (HMI). Due by the complexity of these factors, it is difficult to develop general guidelines to build efficient HMIs independent from the machine or process. A lack of efficiency guidelines potentially hampers the development of new HMIs, currently necessary to address the new challenges in the digital production hall like increasingly complex machines, processes that become more individual as well as multiple machine operation. In order to inform HMI development, voice and touch control alternatives were empirically measured. Based on the collected data complexity time equivalents for each menu level and number of interactions were calculated. These time equivalents provide the opportunity for machine and programmable logic controller (PLC) manufacturers to evaluate their production processes and the related interaction processes regarding the potential efficiency benefits of voice control as a complement or substitute for the conventional HMI system. Using this model, the efficiency advantage of voice control can be estimated without implementing and testing a voice control on a real production machine. Thus, the potential benefit of implementing voice control can be assessed directly, avoiding expensive test runs.