Systems, Man & Cybernetics - April 2016 - 35

Web Camera
3-D Camera
Mounting Plate
and Electronics
yg
Retractable
White Cane

Battery

USB Cables

Encoder
Motor

Gyro
zg

Input Gear
Flange

Electromagnetic
Clutch
Output
Shaft

Active
Roller Tip

Rolling Tip
Section View of the Active Rolling Tip
Figure 1. the CrC.

compliant with the cane's motion,
location information and to register
the CRC's gyro-measured angular
the camera's 3-D points into a 3-D
An EWC is a
velocity ~ g must agree with its
map. The Gumstix reads data from
the camera and gyro and relays the
encoder-measured angular ve handheld device that
data via Wi-Fi to a backend comlocity ~ c = rDa/CLDt cos i. If the
detects obstacle(s) in
puter for pose-estimation and
user swings the cane in the active
its vicinity.
object-recognition computation.
mode, substantial slip at the rollThe results are sent back to the
ing tip will be produced. The slip
Gumstix for nav igation. This
is given by S = ~ c - ~ g . If S is
arrangement is due to the Gumabove a t h reshold, a mot ion
stix's limited computing power and the intent to save
incompliance, indicating the user's intent of using the
power. The CRC has an active rolling tip (ART) that can
CRC in the passive mode, is then detected, and the CRC
steer itself to the desired direction of travel. A speech interis switched to the passive mode. The CRC is switched
face using a Bluetooth headset and a keypad (on the cane's
back to the active mode once a motion compliance is
grip) is being developed for human-device interaction.
detected. The HIDI also detects motion incompliance
The CRC has two navigation modes-robot cane
when the roller tip slips on loose ground due to insuffi(active) mode and white cane (passive) mode-that are
cient traction. This indicates that it is unsuitable to use
selectable to the user by controlling the ART. The ART
the active mode. In this case, the CRC also switches
comprises a rolling tip, a servo motor assembly with an
itself into the passive mode until sufficient traction is
encoder, and an electromagnetic clutch. The rolling tip
produced. The user may override the auto-switch funcis connected to the motor through the clutch. A disention by manually selecting a mode through the keypad.
gaged clutch sets the CRC to its passive mode. In this
Figure 3 depicts the first CRC prototype we have fabrimode, the rolling tip rotates freely just like a convencated. A SwissRanger SR4000 is used for 3-D perception.
tional white cane when the user swings the CRC. In this
The ART (bottom image) is an assembly of motor, encodcase, the speech interface provides the desired travel
er, gear head, and electromagnetic clutch that is connectdirection and object/obstacle information to the user.
ed to a ball-bearing-supported rolling tip by a flexible
An engaged clutch sets the CRC to the active mode,
coupling. A servo controller and a microcontroller boards
allowing the motor to drive the rolling tip and steer the
(Teensy++ 2.0) are used to control the motor and the
CRC to the desired direction of travel. The CRC is a
robot in this mode. Assuming that the CRC is swung
from A to B with no slip (see Figure 2), the yaw angle
∆β = ωc ∆t
change of the device is D} = Dar/CL cos i, where Da is
the motor's rotation angle, C is the gearhead reduction
∆β
ratio, r is the rolling tip's radius, and L is the cane's
A
length. This means that the cane's turn angle can be
R
accurately controlled by the motor.
∆Ψ
Mode selection is made by using the keypad or an
θ
intuitive human intent detection interface (HIDI). The
R
HIDI measures the user's compliance with the cane's
B
motion by analyzing the data from the encoder and
the three-axis gyro (see Figure 1). When the user is
Figure 2. the CrC swings from A to B.
Ap ri l 2016

IEEE SyStEmS, man, & CybErnEtICS magazInE

Table of Contents for the Digital Edition of Systems, Man & Cybernetics - April 2016