CIM 3.3 - Robotic Systems Study Guide
SCARA robots: why are wrists needed/good, type of wrist joint
arm and wrist give the robot the required six deg of freedom to position a tool at many orientations - To orientate the tools, 3 additional joints are required: mounted at the end of the arm - called the wrist. - spherical wrist joint; mounted after the elbow
3 types of robotic drive systems
electromechanical (electric), pneumatic, hydraulic
which robots can do arc welding?
jointed arm robot, polar coordinate robot,
Tool Center Point (TCP)
the X,Y,Z coordinate of the end effector
what is Kinematics, give examples of robots
the spatial arrangement, according to sequence and structure, of the axes of movement (xyz) in relation to one another - Basic types of movement of an industrial robot Types: Cartesian coordinate robot, Cylindrical coordinate robot, Polar coordinate robot, Jointed arm robot, SCARA robot
the volume of space defined by the maximum reach of a robot arm in three dimensions.
work envelope
DC motors
rotary motor class
r axis is
rotation around z axis - base rotates
Drive systems determine what
speed of arm, strength of robot, dynamic performance, application type
Movement of a wrist joints is commonly referred to as ___
roll, pitch, and yaw
Incremental Encoder
- A uniform pattern on the disk provides a signal about a change in position relative to last known location - Accuracy depends upon the last known position -- power disruption --> robot forgets its position
Absolute Encoder works how?
- A unique pattern on the disk is interpreted as a known location at each position - Count remains absolute -- position known after power disconnection
Typical applications of Cartesian robot
- Arc welding - Handling machine tools - Most assembly operations - Application of sealant - Pick and place
Typical applications of polar coordinate robot
- Handling machine tools - Welding: spot welding, gas, arc - Handling diecast machines - Fettling machines (trims rough edges of metal/pottery)
Typical applications of Cylindrical Coordinate robot
- Most assembly operations - Handling machine tools - Spot welding - Handling diecasting machines
Typical applications of Jointed Arm Robot
- Most assembly operations - Handling diecast machines - Fettling machines - Gas welding, Arc welding - Spray painting
Typical applications of SCARA Robot
- Pick and place - Application of sealant - Most assembly operations - Handling at machine tools
Two basic types of robot control systems
- Point-to-Point - Continuous Path
Point-to-Point control system: how it works; when used
- Records beginning (pt) and ending (pt) positions - Determines best path to take between those 2 points - Used when greater repeatability is required, or when the specific path does not matter - won't run into anything -- basically linear
SCARA robots: stand for; describe, parts; work envelope type
- Selectively Compliant Articulated Robot Arm - have motions like a human body. - Incorporate a shoulder and elbow joint as well as a wrist axis and a vertical motion - Kidney shaped work envelope
Continuous Path
- The robot is programmed to follow an irregular path EXACTLY as recorded - The path is represented by many stored points close together --> curvy durvy - During the work cycle, the robot follows the points to reproduce a desired path
Stepper Motors produce highest what? They have ability to ______, which is not present in _____ motors. This allows them to do what?
- produce highest torque at low speeds - Have ability to hold torque, which is not present in DC motors. - Holding torque allows a stepper motor to hold its position firmly when not turning. - Useful for when the motor is starting and stopping while the force acting against motor remains present.
accuracy vs precision
Accuracy - indicates how close measurements are to the actual quantity being measured. - Ex. 50 pound weight on a scale --> scale accurate if it reports a weight of 50 pounds. Precision (Repeatability) - indicates how close together REPEATED measurements of the SAME quantity are to each other. (repeated, consistant) - A precise bathroom scale would give same weight each time you placed the same object on (even if it was not the true weight)
pneumatic drive systems advantages and disadvantages
Advantages: - Uses inexpensive compressed air to operate - Good for clamping work pieces Disadvantages: - Speed and position not easily controlled
hydraulic drive systems advantages and disadvantages
Advantages: - Compact - high levels of force and power with accurate control - Converts forces from a liquid into rotational or linear forces - Quickly being replaced by servo-driven ball screw type systems Disadvantages: messy; not environmentally friendly (toxic); may require costly clean up and disposal.
Electric drive systems advantages and disadvantages
Advantages: - Precise motion control - Greater strength Disadvantages: - Expensive and inefficient - High maintenance - Noisy
articulated robots category
All the joints between all the base members are revolute joints
what types of robots have a rectangular work envelope
Cartesian or Gantry robots
Cartesian Coordinate robot consists of______aka_____
Consists of a column and an arm - sometimes called an x-y-z robot (L-L-L)
Polar Coordinate Robot: consists of, work envelope type
Consists of a rotary base, an elevation pivot, a telescoping extension, and a retraction boom (R-R-L) - Spherical Work Envelope - note: picture is weird but shows correct axes
SCARA Robots are ideal for
Ideal for general purpose applications which require fast, repeatable, and articulate point-to-point movements - Ex. palletizing & de-palletizing, loading and unloading, and assembly. Because of their unique "elbow" motions, SCARA robots also ideal for applications that need constant acceleration through circular motions - Ex. dispensing and gasket forming in place.
Three main subsystems of an industrial robot
Kinematics, Control systems, Drive
A robot control system provides _________ how?
Provides a logical sequence for a robot to follow. - provides positional values required for each step of the process -- robot then continuously checks those pos. values to keep the system on course
Robot sensors functions
Robot sensors provide closed loop control Functions: - Detect positions; Orientate parts - Ensure consistent product quality - Read part characteristics - Identify obstacles - Determine, analyze system malfunctions
what is selectively compliant and why is it important?
Selectively Compliant - there are enough axes of freedom to give the joints flexibility when needed. - Necessary when the robots perform certain operations. -- Example: when the robot performs an insert, the axes of freedom allow the arm to "wiggle" to ensure that the two pieces fit.
Cylindrical Coordinate Robot: consists of; compare to cartesian; type of work envelope
Similar to the Cartesian robot. Contains a column and a base, but the column is able to rotate (L-R-L) - Cylindrical Work Envelope
industrial robot
a complex, technical system consisting of several subsystems operating together
Jointed Arm Robot: describe; parts; work envelope type
resembles a human arm. Usually stands on a rotating base and has an articulating shoulder and elbow joints (R-R-R) - spherical work envelope
_______ provide position information for a robot or machine. what are they? How do they do this?
robot Encoders (type of sensor) - As a robot/machine moves, encoder disk produces a signal