Performance Evaluation Of Tilt Input For Mobile Devices

Inertial sensors built in mobile devices(e.g.,mobile phones and tablets)can sense the motion state and spatial posture of the device,which affords an independent tilt input channel for the devices.In this paper,we evaluated the human performance of tilt input on pointing and steering tasks through two experiments.In the first experiment,12 participants performed pointing tasks using tilt input.Three visual feedback levels,i.e.,fully visual feedback(FV),partially visual feedback(PV),and no visual feedback(NV),were investigated.Under the NV condition,the participants performed the tasks using an eyes-free method.Based on the performance of the participants,we systematically investigated human ability in controlling tilt input of a mobile phone at different levels of visual feedback.The results revealed that trials were performed the fastest but were the most error-prone under the NV condition.The participants could easily distinguish 4 tilt orientation levels(TOLs)and 2 tilt magnitude levels(TMLs)or 8 TOLs and 2 TMLs under the NV condition with tolerance of an error rate 10% or 15%,respectively.PV had no help to tilt input in terms of speed and accuracy.The participants' abilities to control tilt input were related to tilt orientation.In the second experiment,we evaluated the human performance of steering tasks using the tilt input of a tablet.Participants used four levels of tilt gain(10,25,50 and 100)to perform steering tasks with tablet direct feedback and desktop display remote feedback,respectively.The results showed that the tilt input had a fairly high degree of feasibility for steering interactions with both kinds of feedback;and with tilt gains between 25 and 50,tilt input had optimal performance for both task completion speed and throughput of a typical steering interaction.Tilt,as an input primitive of mobile devices,was shown to conform to the steering law,and its throughput ranges from 1.3 to 11.8 bits/s depending on the difficulty of the steering task.