Obstacle Avoidance with Ultrasonic Sensors
JOHANN BORENSTEIN AND YORAM KOREN
Abstract-
A mobile robot system, capable of performing various tasks
for the physically disabled, has been developed. To avoid collision with
unexpected obstacles, the mobile robot uses ultrasonic range finders for
detection and mapping. The obstacle avoidance strategy used for this
robot is described. Since this strategy depends heavily on the performance
of the ultrasonic range finders, these sensors and the effect of their
limitations on the obstacle avoidance algorithm are discussed in detail.
unexpected obstacles, the mobile robot uses ultrasonic range finders for
detection and mapping. The obstacle avoidance strategy used for this
robot is described. Since this strategy depends heavily on the performance
of the ultrasonic range finders, these sensors and the effect of their
limitations on the obstacle avoidance algorithm are discussed in detail.
I. INTRODUCTION
This communication describes some features of a mobile nursing
robot system, which is produced as an aid for bedridden who acquire
constant assistance for the most elementary needs. Such a device, it is
hoped, will return a measure of independence to many bedridden
persons as well as reducing the number of those in need of
hospitalization and constant attendance [22], [23]. The workspace of
the nursing robot would be usually confined to one room, either in a
hospital or in the user's home. This limitation is important since the
constant presence of the disabled person as a supervisor for the
robot's activities greatly facilitates the design of our system and
makes it more economic compared with other similar mobile robots.
Our system is composed of three major subsystems: a mobile
carriage, a robot mounted on it, and a computerized post next to the
disabled person's bed. To interact intelligently with its environment,
the robot utilizes the following sensors:
1) two ultrasonic range finders mounted on the vehicle to detect
obstacles and provide information to detour the obstacle;
2) microswitches attached to the vehicle bumpers to detect
collisions with obstacles that were not found out by the range
finders;
3) incremental encoders attached to the wheels to monitor the
incremental position of the vehicle;
4) light sources attached to the walls and a rotating light-detecting
sensor located on the vehicle to update the absolute position of
the vehicle in the room;
5) force sensors integrated into the robot's gripper to ensure
proper handling of various objects;
6) a video camera attached to the arm to permit the detection and
acquisition of objects;
7) a speech recognition unit to translate verbal instructions into
computer commands.
The prototype of the mobile robot is shown in Fig. 1. It comprises
the carriage which houses the computers and the electronic hardware
and a commercially available five-degrees-of-freedom (DOF) manipulator.
The two ultrasonic transceivers and the light-detecting sensor
are attached to joint 1 of the manipulator such that they can rotate
about the vertical axis. Fig. 1 also shows the multipurpose gripper
with its integrated three-DOF force sensor as well as the floor-level
bumper with the microswitches.
robot system, which is produced as an aid for bedridden who acquire
constant assistance for the most elementary needs. Such a device, it is
hoped, will return a measure of independence to many bedridden
persons as well as reducing the number of those in need of
hospitalization and constant attendance [22], [23]. The workspace of
the nursing robot would be usually confined to one room, either in a
hospital or in the user's home. This limitation is important since the
constant presence of the disabled person as a supervisor for the
robot's activities greatly facilitates the design of our system and
makes it more economic compared with other similar mobile robots.
Our system is composed of three major subsystems: a mobile
carriage, a robot mounted on it, and a computerized post next to the
disabled person's bed. To interact intelligently with its environment,
the robot utilizes the following sensors:
1) two ultrasonic range finders mounted on the vehicle to detect
obstacles and provide information to detour the obstacle;
2) microswitches attached to the vehicle bumpers to detect
collisions with obstacles that were not found out by the range
finders;
3) incremental encoders attached to the wheels to monitor the
incremental position of the vehicle;
4) light sources attached to the walls and a rotating light-detecting
sensor located on the vehicle to update the absolute position of
the vehicle in the room;
5) force sensors integrated into the robot's gripper to ensure
proper handling of various objects;
6) a video camera attached to the arm to permit the detection and
acquisition of objects;
7) a speech recognition unit to translate verbal instructions into
computer commands.
The prototype of the mobile robot is shown in Fig. 1. It comprises
the carriage which houses the computers and the electronic hardware
and a commercially available five-degrees-of-freedom (DOF) manipulator.
The two ultrasonic transceivers and the light-detecting sensor
are attached to joint 1 of the manipulator such that they can rotate
about the vertical axis. Fig. 1 also shows the multipurpose gripper
with its integrated three-DOF force sensor as well as the floor-level
bumper with the microswitches.
according to the following strategy. At first, the carriage
rotates about its center until the robot faces exactly into the direction
of B (pure rotation). Then the robot moves straight forward until it
reaches point B (pure translation), followed by another pure.rotation
about its center until the carriage has the required final orientation
[4].
Any motion between two given locations is performed in this
sequence. The peculiarity of this approach is that it actually uses only
two distinct kinds of motion, either a motion in a straight line, where
both wheels run at the same angular speed in the same direction, or a
rotation about the carriage's center, where both wheels run at the
same angular speed but in opposite directions. This strategy offers
numerous advantages: it is relatively simple yet provides an effective
control system; it avoids slippage of the wheels; the carriage path is
always predictable; and the carriage always travels through the
shortest possible distance (straight line or rotation "on the spot") [2].
rotates about its center until the robot faces exactly into the direction
of B (pure rotation). Then the robot moves straight forward until it
reaches point B (pure translation), followed by another pure.rotation
about its center until the carriage has the required final orientation
[4].
Any motion between two given locations is performed in this
sequence. The peculiarity of this approach is that it actually uses only
two distinct kinds of motion, either a motion in a straight line, where
both wheels run at the same angular speed in the same direction, or a
rotation about the carriage's center, where both wheels run at the
same angular speed but in opposite directions. This strategy offers
numerous advantages: it is relatively simple yet provides an effective
control system; it avoids slippage of the wheels; the carriage path is
always predictable; and the carriage always travels through the
shortest possible distance (straight line or rotation "on the spot") [2].
II. LIMITATIONS OF ULTRASONIC RANGE FINDERS
Ultrasonic range measurements suffer from some fundamental
drawbacks which limit the usefulness of these devices in mapping or
in any other task requiring high accuracy in a domestic environment.
These drawbacks are not related to the product of a specific...... .....
drawbacks which limit the usefulness of these devices in mapping or
in any other task requiring high accuracy in a domestic environment.
These drawbacks are not related to the product of a specific...... .....
PROBLEM IN FIGURE ATTACHMENT SO
DOWNLOAD ITif u like the post just say thank u in comment box.
No comments:
Post a Comment
its cool