Time is lacking to maintain this page properly. It is left "as is" for the time being, pretty much untouched since 2005. On the other hand, the publication page is always refreshed with up-to-date information.
Some devices designed and built at the Haptics Laboratory
Center for Intelligent Machines, McGill University, Canada
Jump to (Click on thumbnails for more pictures)
|6DOF Tactile Stimulator||Decoupled Elastic Hand Controller||Friction Force Scanner|
|Freedom 7-DOF Haptic Device||MicroTactus Tactile System||Morpheotron Haptic Shape Display|
|Pantograph 2-DOF Haptic Device||Hydraulic Manipulator Shoulder||High Strain SMA Actuator|
|Spherical Transport of Acoustic Stimulus||STReSS Tactile Display||VR/TX Gestural Tactile Feedback|
The MicroTactus Tactile Enhancement System.
The MicroTactus is a family of instruments that we have designed to detect signals arising from the interaction of a tip with soft or hard objects and to magnify them for haptic and auditory reproduction; all in a hand-held single-unit system. To date the MicroTactus principle was tested in the form of an enhanced arthroscopic surgical probe used to detect small cuts in cartilage-like materials and other tissue anomalies. Related publications are available
102C as well as a
project web page.
The Morpheotron Haptic Shape Display.
The Morpheotron is a 2-DOF, servo controlled, spherical mechanism. It functions by rolling a plate around a center of rotation that is located inside of the operators fingerpad, causing local deformation at the contact area to mimick the deforming action that is normally present during the exploration of a physical surface. This has been shown to result in a strong sensation of experiencing shape. The Morpheotron may be mounted on top of a lightweight gantry allowing it to be rolled on a table under the control of the operator along the x and y directions thereby providing an additional two degrees of freedom. More information is available in related publications
89C, and in a special web site.
STReSS Tactile Display.
The Stimulator of Tactile Receptors by Skin Stretch (STReSS) stimulates the fingertipby lateral skin stretch. It is a miniature array of 100 (prototype #1) or 50 (prototype #2) bending actuators that create time-varying programmable strain fields at the fingertip to convey tactile information such as texture or small-scale shapes. Tactile signals are generated on a personal computer and then fed to the display via a universal serial bus (USB). In one application, we are presently working on using variants of the STReSS system to display Braille
STReSS is the successor of an earlier system
Related publications can be found in
105C, 106C, 107C,
81C, 82C, and
There is also a special
web site as well as related research on
2DOF Haptic Devices: The Pantograph.
Various versions have been used in the rehabilitation of visually handicapped persons, micro-gravity experiments, etc... The pantograph has one prominent characteristic: the surface which is being touched neither needs to be grasped not does it need to brace a finger (from an ecological view point, people very seldom use styluses or thimbles to explore objects. Using the pantograph resembles exploring surfaces though a small plate, which is closer to normality). Another feature is very high fidelity: irregularities in the frequency response start at 400Hz and it has 3 orders of magnitude of dynamic range. It has negligible friction and very low inertia which give the illusion (when no force signal is applied) of gliding over an icy surface. A new digital version is being developed as we speak and the blue prints will be put in the public domain. Related publications can be found in
The Freedom-7: a 7DOF Haptic Device.
This haptic device, intented for applications where high fidelity matters,
was subsequently commercialized by
to give rise to the Freedon6S. This is an integrated design which includes notable features that make this device quite unique, in addition to the fact that the response is equally crisp and clean in translation as well as in rotation.
These features concern (1) static, (2) kinematic, (3) dynamic, and (4) structural optimized properties (as outlined in publication
They also concern the sensing and drive mechanisms. The reader is refered to publication
for design description and to publication
for additional discussion as well as a description of the transition to the commercial version.
High Strain Shape Memory Alloy Actuators.
They consist of thin NiTi fibers woven in a counter-rotating helical pattern around supporting disks. This structure accomplishes a highly efficient transformation between force and displacement overcoming the main mechanical drawback of shape memory alloys, that of limited strain. They are as fast as the fibers are thin, while preserving the humph due to the many fibers in parallel. Because fibers can be made very thin indeed, they can twitch and relax in milliseconds. Various variable structure controllers were successful at controlling position, force and acceleration for vibration control. Thus we have high strain, high speed, high precision Shape Memory Actuators amazingly simple to build and to control. Related publications can be found in
45J, 43C, 42C,
The Friction Force Scanner.
We built an instrument called a friction force scanner (FFS) able to perform calibrated measurements of the behaviour of mechanical junctions with more than four orders of magnitude of resolution for both displacement
and force. It is essentially a fiber-suspended parallel mechanism that provides exactly two degrees of freedom of motion. Interferometry and a novel differential electrostatic actuator with linear response was used to precisely determine the force experienced by a mechanical junction. The single-stage design is easily calibrated and can be used for force measurement and scanning, allowing the study of friction at multiple length scales. Additional details are available in publication
VR/TX Gestural Tactile Feedback.
An acronym for "virtual texture" (pronounced "vortex", VR/TX is a tactile feedback system to be primarily used in conjunction with open-air computer music performance devices. VR/TX provides tactile feedback using transducers placed at convenient anatomical locations (hands, feets, pockets) in order to minimize interference during on-stage performance while playing open-air controllers (or playing any instrument for that matter). Informal experiments show that the VR/TX vibrotactile signals provide perceptually-significant feedback during performance. A typology of tactile sound events (TSE) was also developed and is further described in described in this article
Spherical Transport of Acoustic Stimulus: STAS.
The STAS was build specifically for testing the psychophysical response of subjects to moving sound sources. Its basic function is to move silently and at high speed (but safely) a speaker at a constant distance from the head of a subject within a large fraction of his/her auditory space. It is a basic spherical parallel five-bar linkage within two grounded actuators which are heavilly enclosed DC motors with timing belt reduction so they are very quiet. With the STAS the auditory motion after effect was discovered (see
59J). Subsequently, Dong,
Swindale and Cynader discovered several other auditory related perceptual effects that were published in the journal Nature.
Hydraulic Manipulator Shoulder.
This was part of the "LightArm" project aimed at building a manipulator arm which would be capable of manipulating several time its own weight. Preliminary tests showed that the arm, once finished, could have been capable of accelerations of 130 m/s2 at the wrist. It could also apply 200 N on static loads at "arm length". The
shoulder joint weighted less than 3 kg (excluding the base) and ran on low hydraulic pressure (500 psi).
This kind of performance, as well as a large singularity free worskspace with parallel kinematics, was made possible by the use of actuator redundancy. Sensing redundancy also made self-calibration and self-test possible. Related publications:
The shoulder was built by
Sarcos Research Inc.
6-DOF Tactile Stimulator.
This machine (never named) was built in 1991 out of scavenged disk drive actuators (thanks Hewlett Packard for a large box of out-of-specs drives!) capable of creating 6 DOF tactile stimuli to the fingers of a subject from DC to 500 Hz. The basic design idea is the handle held inside a cage that allows 12 tendons to act on it in a "cubic" configuration and which has the intertial tensor of a sphere. Thus, the response is guaranteed to be the same along and around all axes. The tendons were made of Spectra(TM) which provided large bandwidth response (results were obtained from experimentation with it, but none are published).
Decoupled Elastic Hand Controller.
This passive hand controller has the property that if one translates the handle, then it creates no torques and hence translates parallel to itself. Conversely, if one rotates it about the center of the handle then it creates no force and hence rotates without translation. It's a standard isostatic platform with six spring loaded legs but with a special geometry. This hand controller is for controlling robots or virtual proxies in rate mode. For details, see publication 19J.