Experiment II: Introduction to Robot Manipulators - Mentor and 5150 | Lab Reports Electrical and Electronics Engineering

ECE 4330, 7330 LAB EXPERIMENT II Fall, 2004

INTRODUCTION TO ROBOT MANIPULATORS: PARAMETERS

AND BASIC OPERATION

This experiment will utilize the Mentor and the 5150 robot manipulators, the

laboratory computer, and special software to achieve the following objectives.

1. Measure, record, and verify the basic kinematic parameters for the Mentor and the

5150 robot manipulators, including joint and link parameters.

2. Demonstrate the basic operation of each of these robots in terms of the motions of

the three major axes, the two minor axes, and the gripper using appropriate control

modes.

3. Investigate the range of motions for various joints, the workspace and other

fundamental characteristics of these robots

Introduction

In the previous experiment, a conveyor belt, along with various sensors, including a

vertical height device, a reflective light sensor, and a metallic detector, was employed to

achieve a specific goal in a block sorting problem. That experience provides an

introduction to a common industrial problem – using a conveyor belt and sensors for

sorting. It also provides experience with a special “work cell” language (Walli); at a

later point, the conveyor belt and sensors will be combined with the robot motions to

achieve more complex work cell objectives.

The LabVolt 5150 robot is a revolute robot manipulator with 5 revolute axes or joints.

The three major axes are 1) waist or base, 2) shoulder, and 3) forearm (or elbow), while

the two minor joints are pitch and roll (no yaw axis). Each joint is driven by a stepper

motor; the waist axis is direct driven, while the other axes are belt driven. One additional

stepper motor is employed to closed a spring-loaded two-finger gripper (end-effector)

using a cable. The advantage of a stepper motor for position control is that it does not

require feedback for accurate positioning; each time that such a motor is pulsed, the

armature moves through a fixed incremental angle, say 3.75 degrees (96 steps per

revolution). Furthermore, the joints are driven by speed reducing gears or pulleys, so that

each actual increment (step angle) can correspond to less than one degree in angle. The

disadvantage of this type of drive (prime mover) is that the values of the controlled joint

angles are always defined relative to the previous values. That is, the correct positioning

of a joint angle at any time requires a knowledge of the (stored) previous angle. For this

reason, such a robot manipulator uses a “home” position as a starting position. The 5150

is controlled through the parallel port of the computer using a special language called

“Robutus”; this robot is also capable of being controlled using “C” programming.

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ECE 4330, 7330 LAB EXPERIMENT II Fall, 2004 INTRODUCTION TO ROBOT MANIPULATORS: PARAMETERS AND BASIC OPERATION This experiment will utilize the Mentor and the 5150 robot manipulators, the laboratory computer, and special software to achieve the following objectives.

Measure, record, and verify the basic kinematic parameters for the Mentor and the 5150 robot manipulators, including joint and link parameters.
Demonstrate the basic operation of each of these robots in terms of the motions of the three major axes, the two minor axes, and the gripper using appropriate control modes.
Investigate the range of motions for various joints, the workspace and other fundamental characteristics of these robots Introduction In the previous experiment, a conveyor belt, along with various sensors, including a vertical height device, a reflective light sensor, and a metallic detector, was employed to achieve a specific goal in a block sorting problem. That experience provides an introduction to a common industrial problem – using a conveyor belt and sensors for sorting. It also provides experience with a special “work cell” language (Walli); at a later point, the conveyor belt and sensors will be combined with the robot motions to achieve more complex work cell objectives. The LabVolt 5150 robot is a revolute robot manipulator with 5 revolute axes or joints. The three major axes are 1) waist or base, 2) shoulder, and 3) forearm (or elbow), while the two minor joints are pitch and roll (no yaw axis). Each joint is driven by a stepper motor; the waist axis is direct driven, while the other axes are belt driven. One additional stepper motor is employed to closed a spring-loaded two-finger gripper (end-effector) using a cable. The advantage of a stepper motor for position control is that it does not require feedback for accurate positioning; each time that such a motor is pulsed, the armature moves through a fixed incremental angle, say 3.75 degrees (96 steps per revolution). Furthermore, the joints are driven by speed reducing gears or pulleys, so that each actual increment (step angle) can correspond to less than one degree in angle. The disadvantage of this type of drive (prime mover) is that the values of the controlled joint angles are always defined relative to the previous values. That is, the correct positioning of a joint angle at any time requires a knowledge of the (stored) previous angle. For this reason, such a robot manipulator uses a “home” position as a starting position. The 5150 is controlled through the parallel port of the computer using a special language called “Robutus”; this robot is also capable of being controlled using “C” programming.

The joints for the Mentor robot manipulator are driven by closed-loop servo-motors; each loop consists of a servo-motor and a feedback potentiometer at each joint. The Mentor has five joint axes: 1) waist or base, 2) shoulder, 3) elbow or forearm, 4) pitch, and 5) roll. There is also a two-finger gripper. This is a very common configuration. This manipulator utilizes direct drive to move the joints, in contrast with using cables or belts, as on other robot manipulators. This robot is controlled from a special back-plane control card in the PC. It can be controlled in several ways (modes) and has been designed to be integrated into a work cell. When constructing a program to control the Mentor using Walli, the angle for each joint is determined by entering a number between 0 and 255, which is equivalent to 8 bits of resolution. The relationship between this numerical entry and the corresponding angle in degrees for each joint is given below. Waist Angle Implementation: Decimal Entry = 127 - [255/210] x (given waist angle) Note: if the waist angle is + 105 degrees, Decimal Entry should be 0 If the waist angle is - 105 degrees , Decimal Entry should be 255 Home Position: Decimal Entry = 127 or 128. Note: if the waist angle for the home position is not 127 or 128, then replace the constant term in Decimal Entry expression above with the actual value. Shoulder Angle Implementation: Decimal Entry = 28 + [255/180] x (given shoulder angle ) Note: if the shoulder angle is 90 degrees, Decimal Entry should be 155 If the shoulder angle is -20 degrees, Decimal Entry should be 0 Home Position: Decimal Entry = 28 Note: if the shoulder angle for the home position is not 28 as implied in the Decimal Entry expression above, replace the 28 constant term with the actual value. Elbow Angle Implementation: Decimal Entry = 127 + [255/230)] x (given elbow angle) Note: if the elbow angle is 115 degrees, Decimal Entry should be 255 If the elbow angle is –115 degrees, Decimal Entry should be 0.

Refer to the notes on robotics for the Mentor robot and to the topics related to Windows Programming of the Mentor robot manipulator and other elements in a work cell. These notes are available from the Engineering Copy Center in the form of “Lab Manuals”. In these manuals, in addition to the general introduction and using Walli, there is a discussion of the modes of operation of the Mentor and “Student Notes on Robotics”, which overlaps with the lecture notes in content. 5150 Robot The Student Manual for the LabVolt 5150 robot is now available from the bookstore; In addition, there are notes, Computer-Controlled Robot System Model 5150 available from the Engineering Copy Center. These notes describe how to use “Robotus”, a special simulation language that simulates the operation of the 5150 robot. Prelab:

1. Read/study about the first 10 pages in the notes, “Student Notes on Robotics”, which begins on page 21 of Lab Manual B. 2. Read/study about one-half of the notes from Lab Manual A” , starting from page 8. 3. Read/study the Student Manual, Introduction to Robotics, Exercise 1, pages 1- 1  1-8. 4. Read/Study pages 1-1  1-3, 2-1  2-3, and 3-2  3-12 in Computer- Controlled Robot System Model 5150. Lab Procedure: 1. For the Mentor robot, investigate and record the limits on each of the major **joint angles as the corresponding bit range changes from 0 to 255 (keyboard mode). Note and record a convenient value for each joint angle that could be used to establish a “home” position. For each major joint angle, verify the decimal entry / joint relationship previously given.

For the Mentor robot, include observations and recordings of the orientation defined by pitch and roll angles.** Limit the movement of these two joints to equivalent decimal representations between 50 and 180. Also observe and record the opening and closing of the gripper.

3. Using a meter stick, verify at least 3 positions and orientations of the Mentor robot for specific, selected decimal entry values, each corresponding to an **angle as displayed in the Windows representation.

Investigate and describe the size and shape of objects that can be effectively** **handled by the gripper. What about handling blocks and cylinders.
Using the LabVolt 5150 robot, investigate the simulation capabilities of** **“Robotus” for simulation.
Using the set of commands provided by the lab instructor, exercise the major** **joints of the 5150 robot in terms of limits.
Referring to step 6, also include the motions for the pitch and roll axes.
Demonstrate the “home” position for the 5150 robot.
Repeat step 4 for the 5150 robot.**

Experiment II: Introduction to Robot Manipulators - Mentor and 5150, Lab Reports of Electrical and Electronics Engineering

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