Face of Dipl.-Inform. Alexander Hoffmann

Dipl.-Inform. Alexander Hoffmann

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Haptic Interface:


TypeRight: a Keyboard with Tactile Error Prevention



TYPERIGHT is a new tactile input device for text entry. It combines the advantages of tactile feedback with error prevention methods of word processors. TYPERIGHT extends the standard keyboard so that the resistance to press each key becomes dynamically adjustable through software. Before each keystroke, the resistance of keys that would lead to a typing error according to dictionary and grammar rules is increased momentarily to make them harder to press, thus avoiding typing errors rather than indicating them after the fact. Two user studies showed that TYPERIGHT decreases error correction rates by an average of 46%.

Haptic Keyboard Prototype for Data Entry (DEKtf)



Haptic input devices provide the user a tactile feedback. In virtual reality, medical testing scenarios, and games, tactile feedback is used to provide the user a more authentic experience. While the user is operating the system, the tactile feedback provides him additional information so that errors during the interaction with the system can be corrected. In word processing several error correction methods occur. Most methods intervene when the error was already done. Prevention methods limit the users' interaction and are only useful for special applications like the city selection menu in navigation systems. DEKtf (Data Entry on a Keypad with tactile feedback) bridges the gap between tactile feedback and data entry error prevention methods.

This thesis introduces an approach that utilizes tactile feedback to prevent errors during data entry. We have built a fully functional keypad that provides tactile feedback. Magnets control the pressure resistance of each key. The concept of DEKtf is to block the keys that would provoke a typing error or a misspelling. Depending on the system state, several blocking algorithms determine the blocking of a key. While a key is blocked, the user needs to apply more strength to overcome the resistance. That way the user feels the tactile feedback, can reconsider his action, and maybe prevent an error. A graphical user interface that reproduces the input and the blocking algorithms are provided by the DEKtf software, which is programmed with Swing, a widget toolkit for Java.

Aside from designing the prototype and implementing the corresponding software, we have ran several DIA (Design - Implementation - Analyze) cycles to improve our system. Furthermore, this thesis contains conduction and evaluation of three user tests. The results of the user studies showed that DEKtf can prevent about 30% of typing erros made by the participants. In date entry applications DEKtf bisected the task completion time of some users.

DEKtf can support beginners and advanced typists as well as elder and disabled users with an impairment of the motor nerves. The tactile feedback prevents the user from inadvertent pressing of neighboring or wrong keys.



  • Alexander Mertens, Chat Wacharamanotham, Jan Hurtmanns, Martin Kronenbuerger, Peter H. Kraus, Arndt Hoffmann, Christopher Schlick and Jan Borchers. Model Based Processing of Swabbing Movements on Touch Screens to Improve Accuracy and Efficacy for Information Input of Individuals Suffering from Kinetic Tremor.  In Human -- Computer Systems Interaction: Backgrounds and Applications 2, Advances in Intelligent and Soft Computing, pages 503–522, Springer Berlin Heidelberg, August 2012.
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  • 2009

  • Alexander Hoffmann, Daniel Spelmezan and Jan Borchers. TypeRight: a Keyboard with Tactile Error Prevention.  In Proceedings of the CHI 2009 Conference on Human Factors in Computing Systems, pages 2265–2268, ACM Press, New York, NY, USA, April 2009.
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  • 2008

  • Alexander Hoffmann. Haptic Keyboard Prototype for Data Entry. Master's Thesis, RWTH Aachen University,May 2008.
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