COMP322/S2000/L31 Components of a Robotic System Robot: Articulated Mechanical System with Actuators Computer Task Environment Interaction Control Language (Program) Internal “sensed” Information e.g. force External “sensed” Information e.g. camera, sonar

COMP322/S2000/L32 Components of a Robotic System Robotic System is Task specific Sensory information (internal and External) provides intelligence to the system but generates many challenging research topics The Mechanical System with Actuators INTERACT with the Environment The Computer System CONTROLS the Robot

COMP322/S2000/L33 Classification of Robot Arms: by Drive Technology Hydraulic System –made up of an electric motor that pumps a non-compressible fluid into a system consisting of a reserve tank, control valves and actuators to transmit energy. –generally associated with larger robots –Advantages: greater power, i.e. can handle heavy load greater speed –Disadvantages: occupies large floor space tendency to leak oil => dirty noisy –Applications: for heavy “dirty” task, e.g. welding in automobile and aircraft industries

COMP322/S2000/L34 Classification of Robot Arms: by Drive Technology Hydraulic System Electric System –AC motor, DC servo or stepper motor –for small robots –Advantages: high accuracy high repeatability clean –Disadvantages: less power, i.e. less payload slower –Applications: assembly tasks that requires precision, e.g. circuit board.

COMP322/S2000/L35 Classification of Robot Arms: by Drive Technology Hydraulic System Electric System Pneumatic System –Uses compressed air –for smaller robots with fewer degrees of freedom –Advantages: readily installed since compressed air is readily available in factory floors and laboratories –Disadvantages: difficult to provide good precision due to the fact that air is compressible, easily affected by temp., humidity, etc. –Applications:control of grippers to provide compliance in grasping objects, e.g. SONY robots in the lab.

COMP322/S2000/L36 Classification of Robot Arms: by Drive Technology Hydraulic Power Supply Pneumatic Power Supply

COMP322/S2000/L37 Classification of Robot Arms: Work Envelope Geometry Kinematics of Robot Arms is defined as the Relationship between arm (link) parameters and the configuration (position and orientation) of the end-effector with respect to a reference point Arm parameters: motion of joints Prismatic (P) - Linear motion ALONG an axis Revolute (R) - Rotary motion ABOUT an axis

COMP322/S2000/L38 Classification of Robot Arms: by Work Envelope Geometry Definition: The Gross Work Envelope of a robot is defined as the LOCUS of points in the 3D space that can be reached by the “wrist” (end effector). Considering 3 major axes only: (5 types) Axis 1Axis 2Axis 3 CartesianPPP CylindricalRPP SphericalRRP SCARARRP ArticulatedRRR

COMP322/S2000/L39 Cartesian Rectangular-coordinates Robot 3 linear axes (P,P,P) Advantages: –Easy to visualize –Rigid structure –Easy to program off-line –Good repeatability and accuracy Disadvantages: –Requires large floor space for the large structure –Can only reach in front of itself –Restriction on the compatibility with other types of arms in a common work space

COMP322/S2000/L310 Examples of Cartesian Robots

COMP322/S2000/L311 Cylindrical Work space is the space between 2 concentric cylinders of the same height 2 Prismatic (linear) axes (P,P) and 1 Rotational axis (R) Advantages: –Rigid structure –Easy to program off-line –Good repeatability and accuracy Disadvantages: –Horizontal motion is circular only –Restriction on the compatibility with other types of arms in a common work space

COMP322/S2000/L312 Example of Cylindrical Robots

COMP322/S2000/L313 Spherical Polar-coordinates Robot 1 linear axis (P), 2 rotational axes (R) Work envelope is the volume of concentric spheres but truncated from above, below and behind (where the arm cannot reach) Advantages: –can be light in weight –Easy to program –Good precision Disadvantages: –Large and variable torques on joints 2,3 => the counter balance problem –Positional error is proportional to the radius at which the arm is operating

COMP322/S2000/L314 Example of Spherical Robots

COMP322/S2000/L315 Examples of Spherical Robots and the work envelope Range of motion of the 5 axes General View Working Volume

COMP322/S2000/L316 SCARA Selected Compliance Assembly Robot Arm 1 linear axis (P) and 2 rotational (R) axes Work envelope similar to the cylindrical one Advantages: –Relatively inexpensive –Height axis is rigid => good for insertion type of tasks –Good repeatability Disadvantages: –Difficult to program off-line

COMP322/S2000/L317 Example of SCARA Robots

COMP322/S2000/L318 Articulated Closely resembles a human arm 3 rotational axes (R,R,R) Advantages: –Most flexible –Most anthropomorphic –Compatible with other robots working in common work space Disadvantages: –Most difficult to control –Accuracy can be poor

COMP322/S2000/L319 Example of Articulated Robots

COMP322/S2000/L320 References Diagrams and figures are from the following references: James L. Fuller, Robotics - Introduction, Programming, and Projects, Prentice Hall, 2nd edition, (ISBN: ) Robert J. Schilling, Fundamentals of Robotics - Analysis & Control, Prentice Hall, (ISBN: )