Geometric Configurations for Robots

1. Geometric Configurations for
Robots
• Robots take a bewildering variety of
forms:
• arms of all shapes,
• vehicles with all possible arrangements of
wheels or legs,
• devices which although clearly robotic are
neither vehicles nor arms

2. • This Topic makes sense of this variety by
explaining how the functions required of a
robot can be met by combinations of
mechanical elements such as links and
joints.
• It concentrates on manipulation robots.

14. Definitions
• Robot: An electromechanical device with
multiple degrees-of-freedom (dof) that is
programmable to accomplish a variety of
tasks.
• Robotics: The science of robots. Humans
working in this area are called roboticists.
• Degrees-of-freedom (dof ): the number of
independent motions a device can make.
Also called mobility.

15. • How many dove does the human arm
have? The human leg?
• The human hand has 27 degrees of
freedom: 4 in each finger, 3 for extension
and flexion and one for abduction and
adduction; the thumb is more complicated
and has 5 DOF, leaving 6 DOF for the
rotation and translation of the wrist 1.

16. • From the perspective of biomechanics,
human leg has 30 DOF.
• Manipulator: Electromechanical device
capable of interacting with its environment.
• Anthropomorphic: Designed or appearing
like human beings.
• end-effector: The tool, gripper, or other
device mounted at the end of a manipulator,
for accomplishing useful tasks.

17. • Workspace : The volume in space that a
robot’s end-effector can reach, both in
position and orientation.
• Position: The translational (straight-line)
location of an object.
• Orientation: The rotational (angular) location
of an object. An airplane’s orientation is
measured by roll, pitch, and yaw angles.
•

18. • Pose: position and orientation taken together.
• Link: A rigid piece of material connecting
joints in a robot.
• Joint: The device which allows relative
motion between two links in a robot.
• Kinematics: The study of motion without
regard to forces/torques.
• Dynamics: The study of motion with regard
to forces/torques.

19. • Actuator: Provides force/torque for robot
motion.
• Sensor: Reads actual variables in robot
motion for use in control.
• Haptics: From the Greek, meaning to touch.
Haptic interfaces give human operators the
sense of touch and forces from the computer,
either in virtual or real, remote
environments. Also called force reflection in
telerobotics.

21. The distinction between arms and
vehicles
• If we wish to move an object about in space,
relative to something fixed such as the
ground,
• How many dimensions are needed?
6(six)
six dimensions are needed to specify situation:
• Three for its position 3
• Three for its orientation or attitude 3

22. • These must be controlled in some way, by
connecting the object to the ground with a
link allowing the transmission of the forces
and torques needed to support and move the
object.
• If the link is continuous and fixed to the
ground we have a manipulator; if it is made
by a self-contained device which propels
itself about on a surface or through a
medium we have a vehicle.