Summary
We
present the design and an implementation for a portable, single
degree-of-freedom handheld haptic display.
Why a low-DOF handheld device?
- can be low-cost without compromising performance;
- ungrounded configuration allows user to work in non-desktop
environments, supporting new types of tasks
Our
implementation includes:
- actuated wheel
- two axes of force sensing
- I/O controller
- USB connectivity to host application server.
.
Design
Layout
- user rotates actuated wheel and receives haptic feedback
- pushing radially on wheel excites force sensor
- system reads force magnitude and infers identity of “active”
(pushed-from) face.
Each
face can control a different set of functions. Easily distinguished
surface textures allow user to identify them by feel.
Force
Sensing
 Force
is sensed on two axes by strain gage pairs mounted on facing
handle walls. Each pair is activated by pressing radially on
the thumbwheel.
A force applied on the wheel from the center of any face will
activate just one pair: for example, pressing from faces “A”
or “D” activates the x sensor.
 So,
which face was the wheel pressed from?
Step 1: If |xvalue| > |yvalue|, then either A or D was pressed.
Step 2: The sign of the larger value disambiguates the face:
If xvalue > 0, then A was pressed, not D - because the wheel
can be pushed radially but not pulled
Software
Architecture: USB Connectivity
This
application development platform had several requirements:
- “plug and play” connectivity of the display to range
of host computers
- haptic model computation on host, to facilitate model development
and coupling to controlled media local sampling and signal processing
of sensors
- embedded controller with >= 500 Hz communication to host, satisfied
marginally by USB 1.1 and comfortably by USB 2.0.
Microchip’s PIC line supports both USB and necessary I/O. The
result requires no specialized hardware in the host computer, and
is easily adapted to most operating systems.
So...What
is it good for?
We
are developing new media control applications including digital
video, audio and large-scale graphics (examples below).
A prerequisite in every case is a set of universal haptic behaviors
that make sense for different kinds of media streams.
For example, digital video comes in many forms. The same haptic
signals should work for them all, and for similar audio and graphic
streams.
How?
A few physical metaphors facilitate seamless, intuitive control
of functions like rate, jumps, volume, zoom.
The user:
- perceives system state through haptically displayed behaviors
- continuously modulates motion commands by varying wheel position
and pressure, and
- selects manipulation target or function via handle orientation.
Browsing
Video & Broadband Cable
You are watching TV from the living room couch - not a comfortable
place for a mouse. With handheld haptic control, you can move
through the video at smoothly changeable rates and mark / jump
to selected points; you can navigate flat or hierarchical collections
of streams such as cable TV channels.
Home Video Editing
Again from the couch, you compose a new segment of video by
combining clips from other sources. You can now browse within
the current segment; switch between segments; mark cut / insert
points; paste a source clip into the new segment; and apply
simple effects like fades and dissolves.
Audio File Navigation
From your large collection of audio files stored on a server
in your home you choose several and set them up to play while
you do something else. You access your multi-room audio system
from throughout the house. With force feedback and use of “haptic
icons”, you can not only switch CD trays, volume or channel,
but also access and manipulate individual tracks.
Control of Large-Scale Graphic Displays
Room-sized graphic displays are awkward to control with grounded
tools; ungrounded pointers are only good for pointing. With
handheld haptic display augmented with pointing capability,
you can click and drag and provide other mouse-like operations.
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