HapSticks: A novel method to present vertical forces in tool-mediated interactions by a non-grounded rotation mechanism

Force feedback in tool-mediated interactions with the environment is important for successful performance of complex tasks in our daily life as well as in specialized fields like medicine. Stylus-based haptic devices are studied and used extensively, and most of these devices require either grounding or attachment to the body of the user. Recently, non-grounded haptic devices are getting an increasing attention. In this paper, we propose a novel method to represent the vertical forces that are applied on the tip of a tool: a non-grounded rotation mechanism that mimics the cutaneous sensation that is caused by these tool-tip forces. To evaluate this method, we developed a novel ungrounded haptic device - HapSticks - that renders the sensation of manipulating objects using chopsticks. First, we present the novel mechanism, and test the pressure that it applies on the hand of the user when rendering a force at the tip of the tool in comparison to applying a real force at the tip of the tool. Next, we used the mechanism to build the HapSticks device as an example of an application of the proposed method, and present a psychophysical evaluation of this device in a virtual weight discrimination task.