Definition of robot 

• “A robot is a reprogrammable, multifunctional manipulator designed to move material, parts, tools, or specialized devices through variable programmed motions for the performance of a variety of tasks.” (Robot Institute of America) 

Alternate definition of robot

• “A robot is a one-armed, blind idiot with limited memory and which cannot speak, see, or hear.” 
• MIT’s Kismet: a robot which exhibits expressions, e.g., happy, sad, surprise, disgust. 
• A SCARA robot (Selective Compliant Articulated Robot Arm): A pick-and-place robot with angular 
• x-y-z positioning (Adept Technology) 
• A six-axis industrial robot ($60K)(Fanuc Robotics), but an additional $200K is often spent for tooling and programming. 

Ideal Tasks of robots

• Tasks which are: 
• Dangerous 
• Space exploration 
• chemical spill cleanup 
• disarming bombs 
• disaster cleanup 
• Boring and/or repetitive 
• Welding car frames 
• part pick and place 
• manufacturing parts. 
• High precision or high speed 
• Electronics testing 
• Surgery 
• precision machining. 

Automation vs. robots

• Automation –Machinery designed to carry out a specific task 
• Bottling machine 
• Dishwasher 
• Paint sprayer 
• Robots – machinery designed 
• to carry out a variety of tasks 
• Pick and place arms 
• Mobile robots 
• Computer Numerical Control 
• machines 

Types of robots

• Pick and place 
• Moves items between points 
• Continuous path control 
• Moves along a programmable path 
• Sensory 
• Employs sensors for feedback 

Pick and Place robots

• Moves items from one point to another 
• Does not need to follow a specific path between points 
• Uses include loading and unloading machines, placing components on circuit boards, and moving parts off conveyor belts. 

Continuous path control in robots 

• Moves along a specific path 
• Uses include welding, cutting, machining parts. 

Measures of performance in robots

• Working volume 
• The space within which the robot operates. 
• Larger volume costs more but can increase the capabilities of a robot 
• Speed and acceleration 
• Faster speed often reduces resolution or increases cost 
• Varies depending on position, load. 
• Speed can be limited by the task the robot performs (welding, cutting) 
• Resolution 
• Often a speed tradeoff 
• The smallest step the robot can take 
• Accuracy 
• The difference between the actual position of the robot and the programmed position 
• Repeatability 
• Will the robot always return to the same point under the same control conditions? 
• Increased cost 
• Varies depending on position, load 

Control robots

• Open loop, i.e., no feedback, deterministic 
• Closed loop, i.e., feedback, maybe a sense of touch and/or vision 

Kinematics and dynamics in robots

• 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 
• Actions 
• Simple joints 
• prismatic—sliding joint, e.g., square cylinder in square tube revolute—hinge joint 
• Compound joints 
• ball and socket = 3 revolute joints 
• round cylinder in tube = 1 prismatic, 1 revolute 
• Mobility 
• Wheels 
• multipedal (multi-legged with a sequence of actions) 
• Work areas 
• rectangular (x,y,z) 
• cylindrical (r,θ,z) 
• spherical (r,θ,ϕ) 
• Coordinates 
• World coordinate frame 
• End effector frame 
• How to get from coordinate system x” to x’ to x 

Dynamics

• Velocity, acceleration of end actuator 
• power transmission 
• actuator 
• solenoid –two positions , e.g., in, out 
• motor+gears, belts, screws, levers—continuum of positions 
• stepper motor—range of positions in discrete increments 

Problems in robotics

• Joint play, compounded through N joints 
• Accelerating masses produce vibration, elastic deformations in links 
• Torques, stresses transmitted depending on end actuator loads 

Control and Programming

• Position of end actuator 
• multiple solutions 
• Trajectory of end actuator—how to get end actuator from point A to B 
• programming for coordinated motion of each link 
• problem—sometimes no closed-form solution 

Feedback control in robotics

• Rotation encoders 
• Cameras 
• Pressure sensors 
• Temperature sensors 
• Limit switches 
• Optical sensors 
• Sonar

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