Frein utilisant la lubrification active pour la conception de dispositifs haptiques

A multitude of actuators for vibrotactile rendering exist, typically covering a large portion or the entirety of the haptic bandwidth while remaining safe, compact, and cost-effective. Numerous devices also render force and torque. However, only a few can simultaneously render both vibrotactile and kinaesthetic feedback. All these systems are active devices that can compromise user safety without proper mechatronic and control system design to prevent instabilities. Moreover, to render both types of feedback, devices often employ multiple actuators to address different portions of haptic bandwidth, thus increasing complexity, size, and cost. This thesis investigates the creation of a novel passive actuator that is intrinsically safe and capable of rendering both types of feedback while addressing constraints such as weight, size, control simplicity, and cost. The proposed design is a brake based on active lubrication—a phenomenon that reduces friction between contacting parts through high-frequency vibrations. Controlling these vibrations, and thus the friction, can facilitate or impede part motion, thereby creating passive force feedback. While active lubrication has been explored for actuators, it is rarely used to create brakes, and existing implementations have not explored longitudinal vibrations nor the creation of vibrotactile feedback with the same brake. The brake has a very short response time, allowing to modulate friction up to 500 Hz, thus rendering vibrotactile feedback. The contributions of this thesis include: the novel concept and characterization of an active lubrication brake, capable of generating both force and vibrotactile feedback, its implementation in various haptic devices, and its evaluation with end-users in two use cases. First, we experimentally characterized the brake output (force and vibration) under several parameters: applied normal load, moving part speed, applied voltage, and haptic vibration frequency. Results demonstrated that this design can create modular and tunable force feedback over a range of up to 90% of the maximal force (e.g., between 0.3 N and 3 N), and perceptible vibrotactile feedback between 0 and 333 Hz with an amplitude of at least 0.1 N. Additionally, models of active lubrication for friction force prediction were compared to experimental data to evaluate their applicability. Second, we developed linear and rotary versions of the brake and implemented them into buttons, sliders, and knobs as proof-of-concept prototypes. We then implemented our brakes in more complex devices and evaluated them for specific use cases. The first device was a grounded medical drilling training system capable of producing force between 0 and 4.5 N and vibrations. Two user studies involving 14 participants and 6 surgeons demonstrated the potential applicability of our brake for this application and that providing both force and vibrotactile feedback, rather than either alone, was the optimal compromise between realism, user preference, and performance. The second device was a hand-wearable system. The first prototype, mounted on the index finger, enabled force up to 3.15 N and tunable vibrotactile feedback from 1 Hz to 100 Hz. A user study with 12 participants proved that three absolute force levels were easily identified and that different vibrotactile patterns could be recognized. Subsequent prototypes for multiple fingers, with and without additional actuators, were created. A complete version was showcased at the Tech & Fest event and received positive user feedback from 80 people through a survey. Future work includes upgrading the medical device from a grounded to a hand-held configuration, investigating the design of alternative brakes to expand the range of achievable force, exploring other models for force and vibration prediction, evaluating the wearable for manipulation tasks in virtual reality, and implementing our brake in other relevant applications.