Chapter 2 - Robot Classifications

Question 1

How are robots classified?

Answer 1

Generally by motion. But depending on the programmers focus they can be classified by control systems, drives, degree of autonomy and use case

Question 2

What are the types of movement?

Answer 2

Pick and place, point to point and continuous path.

Question 3

What are the three main subsystems of a robot?

Answer 3

Kinematics - Manipulator
Control Systems - Controller
Drive Systems - Power Supply

Question 4

What is kinematics?

Answer 4

Describes the spatial arrangement of the axes of movement in relation to one another

Question 5

What are the 4 basic classifications of movement?

Answer 5

Cartesian, Cylindrical, Spherical and Jointed-Arm.

Question 6

What is the gross work envelope?

Answer 6

It basically describes how far the robot can reach with its wrist. The area that can be reach is the robots work envelope.

Question 7

What are the major axes?

Answer 7

The first three joints of a robot, this determines the position of the wrist.

Question 8

What are the minor axes?

Answer 8

The remaining joints are the first three, they determine the orientation of the tool.

Question 9

What is a revolute joint?

Answer 9

Most common type of joint in industrial robotics. Exhibits rotary motion about an axis. Generally, the more revolute joints, the more complex the arm.

Question 10

What is rotary motion?

Answer 10

Turning around in a circle ex: wheel turning (angular)

Question 11

What is a prismatic joint?

Answer 11

Second most common type of joint. Exhibits sliding or linear motion along an axis.

Question 12

What is linear motion?

Answer 12

Moving in a straight line ex: paper trimmer

Question 13

What is lateral motion?

Answer 13

X-axis, side to side motion ex: a robots base

Question 14

What is longitudinal motion?

Answer 14

Y-axis, parallel to the axis, relating to length ex: robot arm moving forwards and backwards to the workspace

Question 15

What is vertical motion?

Answer 15

Z-axis, references the depth, similar to horizontal except it is not constant and is effected by gravity. Ex: robot column moving up and down.

Question 16

What is a Cartesian coordinate robot?

Answer 16

Robot consisting of a base, column and arm. It has 3 prismatic joints. The base (x-axis) moves from side to side. The column (z-axis) moves up and down. The arm (y-axis) moves forwards and backwards (to and from) the work area. Use case: arc welding.

Question 17

What is a Cylindrical coordinate robot?

Answer 17

Has 1 revolute and 2 prismatic joints. The base (x-axis) is stationary. The column (z-axis) rotates. The arm (y-axis) moves up and down the column and can extend in and out towards the work area. Use cases: Assembly, handling machine tools

Question 18

What is a Spherical coordinate robot?

Answer 18

Has 2 revolute joints and 1 prismatic. The base (x-axis) is stationary. The column (z-axis) is thick like a hose and can telescope and boom, allowing it to bend forwards/backwards, and giving it an elevation pivot. The arm (y-axis) extends forwards/backwards towards the work area. Use case: spot welding

Question 19

What is a Jointed-Arm coordinate robot?

Answer 19

Has 3 revolute joints. Resembles the human arm. Mounted on a rotating base (x-axis), articulating at a joint just above the base called the shoulder. Also contains wrist and elbow joints. Use cases: painting and welding.

Question 20

What is a controller?

Answer 20

A device that completes the control loop by accepting the feedback signal from input devices and then generating as an output, the control signal required for the output device to perform its function.

Question 21

What are the two main sections of the controller?

Answer 21

Measurement and control

Question 22

What is the function of the measurement section?

Answer 22

To measure the value of the incoming signal from a sensor (ex. transducer) and compares it with the value of the set point signal.

Question 23

What is the function of the control section?

Answer 23

Acts upon an error between the two signals (incoming and set-point) by sending an output signal to the final control element, which acts to eliminate the error.

Question 24

What is a multi-controller (hybrid-control) system?

Answer 24

A system where the kinematic and robot program functions are controlled by separate microprocessors that communicate via Ethernet.

Question 25

What is a servo-control system?

Answer 25

A robot driven by a servomechanism, in which feedback positional data is compared to command data. Involves the use of feedback devices and microprocessors.

Question 26

What is a non-servo control system?

Answer 26

One that does not require feedback devices or a microprocessor.

Question 27

What is a pick and place robot?

Answer 27

Has a limited degree of mobility, and little to no trajectory control.

Functions to transfer objects from one place to another.

Non-servo control system, used in applications involving high repetition.

Ex: bang-bang control applies on or off outputs to attempt to maintain control ex: thermostat

Question 28

What is point to point control?

Answer 28

Uses a servo system that records where a robot picks up a part and where it drops it off. Once the points are recorded, it calculates the most efficient path to take between the points.

Used in loading and unloading applications, where the path between the end points aren’t important.

Robot cannot stop at arbitrary points not previously designated.

Question 29

What is a teach pendant?

Answer 29

Used to program a robot to move from one point to another.

Question 30

What is Continuous-Path control?

Answer 30

Uses a trajectory tracking system to follow an irregular path with a high degree of accuracy.

Can stop at arbitrary points along a path

Used in painting and welding applications

If the speed of each joint can be controlled independently, than the robot manipulator it capable of CP control.

Question 31

Types of drive systems?

Answer 31

Electric, hydraulic and pneumatic

Question 32

Characteristics of electric drive systems?

Answer 32

Uses DC servomotors, DC brushless motors, DC stepper motors.

Brushless dc motors are cleaner, require little maintenance and are used in painting and solvent applications that pose fire hazards due to its brushless arcing.

However the require separate transmission mechanisms, adding weight, cost and loss of precision.

Question 33

Characteristics of hydraulic drive systems?

Answer 33

Preferred in applications requiring high speed manipulation of heavy loads.

Have more speed and strength but require more floor space and are messier.

Question 34

Characteristics of pneumatic drive systems?

Answer 34

Non-servo controlled.

Used for limited sequence robots, like pick and place, where speed and precision aren’t essential.

The air flow is usually controlled by solenoid valves.

Considered safe, used in explosive atmospheres

Only good for lighter loads, heavy loads require large amounts of air.

End effectors of all drive types are usually pneumatic, makes gripping more delicate

Question 35

What is the TCP?

Answer 35

The tool center point is the tip of an end effector. Programmers use its coordinates in space (x,y,z) to program the tool to perform a function. Ex. Welding.

Question 36

Types of line tracking robots?

Answer 36

Moving-base line tracking (MBLT): robot mounted on a transport that moves parallel to the line at line speed.

Stationary-base line tracking (SBLT): robot is fixed relative to the line. Allowing it to work at the front, middle and rear of a moving part, allowing it to access areas not possible with a stationary part.

Question 37

What is the tracking window?

Answer 37

Defines in memory, the two limits in the tracking direction beyond which the robot will not attempt to reach.

Abort branches occur when the robot coordinates coincide with the limits of the tracking window.

Utility branches occur when there is a malfunction in peripheral equipment.

Question 38

Brush vs Brushless motors?

Answer 38

Brush motors makes rubbing contact with a rotating commutator to conduct current to and from an outside circuit. Brushless motors use an electronic commutator instead.

Question 39

What is Roll?

Answer 39

The circular motion of an axis

Question 40

What is Yaw?

Answer 40

The angular displacement of a moving body about an axis perpendicular to the line of motion and to the top side of the body

Question 41

What is Pitch?

Answer 41

The up and down motion at an axis