Robotics Process

Asimov proposed three “Laws of Robotics”

  • • Law 1: A robot may not injure a human being or through inaction, allow a human being to come to harm.
  • • Law 2: A robot must obey orders given to it by human beings, except where such orders would conflict with the first law.
  • • Law 3: A robot must protect its own existence as long as such protection does not conflict with the first law.

Kinematics and dynamics

• Degrees of freedom—number of independent motions

• Translation --3 independent directions

• Rotation -- 3 independent axes

• 2D motion = 3 degrees of freedom: 2 translation, 1 rotation

• 3D motion = 6 degrees of freedom: 3 translation, 3 rotation

Robots Configurations

• Cartesian/Rectangular Gantry (3P) : These Robots are made of 3 Linear joints that orient the end effector, which are usually followed by additional revolute joints.

• Cylindrical (R2P): Cylindrical coordinate Robots have 2 prismatic joints and one revolute joint.

• Spherical joint (2RP): They follow a spherical coordinate system.

• Articulated/anthropomorphic(3R) :An articulated robot’s joints are all revolute, similar to a human’s arm.

• Selective Compliance Assembly Robot Arm (SCARA) (2R1P): They have two revolute joints that are parallel and allow the Robot to move in a horizontal plane, plus an additional prismatic joint that moves vertically.

Wrist Configuration

• Typically has 3 degrees of freedom

• Roll involves rotating the wrist about the arm axis

• Pitch up-down rotation of the wrist

• Yaw left-right rotation of the wrist

• End effector is mounted on the wrist

Control Methods

• Non Servo Control

• implemented by setting limits or mechanical stops for each joint and sequencing the actuation of each joint to accomplish the cycle

• end point robot, limited sequence robot, bang-bang robot

• No control over the motion at the intermediate points, only end points are known

• Servo Control

• Point to point Control

• Continuous Path Control

• Closed Loop control used to monitor position, velocity (other variables) of each joint

Point-to-Point Control

• Only the end points are programmed, the path used to connect the end points are computed by the controller

• user can control velocity, and may permit linear or piece wise linear motion

• Feedback control is used during motion to ascertain that individual joints have achieved desired location

Programming Languages

• Motivation

• need to interface robot control system to external sensors, to provide “real time” changes based on sensory equipment

• computing based on geometry of environment

• ability to interface with CAD/CAM systems

• meaningful task descriptions

• off-line programming capability

• Large number of robot languages available

• AML, VAL, AL, RAIL, RobotStudio, etc. (200+)

• Each robot manufacturer has their own robot programming language

• No standards exist

• Portability of programs virtually non-existent