ME 449 Robotic Manipulation (Archive Fall 2016)

Fall Quarter 2016

• Instructor: Prof. Kevin Lynch
• Office hours: Tech B222, 2-3 PM Tuesday and 3-4 PM Wednesday (during finals week: Tues 2:30-3:30, Thurs 11-12)
• Meeting: 12:30-1:50 TTh, Tech M345
• course website: http://hades.mech.northwestern.edu/index.php/ME_449_Robotic_Manipulation

Course Summary

Mechanics of robotic manipulation, computer representations and algorithms for manipulation planning, and applications to industrial automation, parts feeding, grasping, fixturing, and assembly.

Grading

Grading for the course will be based on problem sets and a final project. There will be no exams. All assignments, including the final project, have equal weight, and your lowest assignment grade will be dropped in calculating your final grade.

Course Text and Software

Go here to get the final version of the public book. (No changes relevant to the final project from the previous version.)

Download this software (dated Nov 29) for your final project. Contains a few bug fixes.

Introduction to V-REP, which we will be using to simulate robots.

How to obtain MATLAB.

Reading

This supersedes the approximate syllabus below.

• Chapter 2
• Chapter 3
• Chapter 4 (4.2 can be skimmed)
• Chapter 5
• Chapter 6 (6.1 can be skipped)
• Chapter 8 (8.4 can be skipped; 8.8-8.9 are for reference only for those interested)
• Chapter 9 (9.1 and 9.4 only)
• Chapter 11, stopping before the Force Control section
• Chapter 13 (skip 13.3)

Assignments

Assignments are graded based on correctness, how well you organize your homework (it should be easy to understand your thinking and easy to find your responses), and how well you follow the submission instructions below. You will lose points if you don't follow these instructions.

If you ever think a problem is stated incorrectly, not enough information is given, or it is impossible to solve, don't panic! Simply make a reasonable assumption that will allow you to solve the problem (but clearly state what this assumption is), or indicate why it is not possible to solve the problem.

Instructions for uploading assignments to Canvas:

0. Upload on time! Late submissions are not accepted. The cutoff time is at the beginning of class on the day the assignment is due.

1. Only upload one zip file or rar file for each assignment;

2. In your zip file or rar file, include all source codes in their original form, such as .cpp, .m, .py, .nb.

3. If there is a demo, combine the screen shots into one SEPARATE pdf file, OR, show the results in one SEPARATE .txt file (DON'T show them in your source code file format, e.g. .nb file), and include it in the zip file (or rar file).

4. Always include output of your code running on the exercises, particularly in case the grader has problems running your code. Also, always create a script (for example, titled ex6-9 or something) that the grader can easily invoke for each exercise. Don't expect the grader to search through your code to find sample code to cut-and-paste. Make it as easy as possible for the grader (you can include a "README" in your solutions, for example).

5. Please name the upload file in the following format: LastName_FirstName.zip.

Assignments

• Assignment 1, due on Canvas before the beginning of class on Thurs Oct 6: Chapter 2, Exercises 1, 3, 5, 16, 17, 28, 29; Chapter 3, Exercises 1, 2, 6, 16, 26, 27, 28, 31, 47.
• Assignment 2, due on Canvas before the beginning of class on Thurs Oct 20: Chapter 4, Exercises 1, 2, and 7; Chapter 5, Exercises 2, 3, 8, 24, 25, and 28
• Assignment 3, due on Canvas at 12:30 PM Friday Nov 4 before the beginning of class on Thurs Nov 3: Chapter 6, Exercise 7, 8, and 9, plus a programming assignment: You will write a program for trajectory generation for the UR5 robot, as described in Chapter 4. For simplicity, the {b} frame is always aligned with the {s} frame in this trajectory. Your program accepts a start point for {b} and a goal point, each expressed as (x, y, z) of the {b} frame relative to {s}. Call these points (xstart, ystart, zstart) and (xend, yend, zend). Your program will solve the numerical inverse kinematics at 101 points: the 1st point, at (xstart, ystart, zstart), the 101th point, at (xend, yend, zend), and at 99 points spaced equally in between. For your initial guess at the 1st point, you can use all joint angles equal to zero. (If this results in convergence problems, you can choose a different guess.) At subsequent points, you should use the solution to the previous point as your initial guess. Your program will then write out a comma separated values (csv) text file with rows such as 0, 0, 0, 0, 0, 0 and 0.12, 0.37, -0.54, 0.01, 0.02, -0.31, where each row corresponds to the joint angles that solve the inverse kinematics problem for the given (x, y, z) point, from the 1st to the 101st. So your csv file will have 101 rows. Then you will use the V-REP simulator, scene 2, to "play" the trajectory in your CSV file to see the motion of the robot. You will make a video of the motion. You will turn in (1) your working, commented code and (2) your video. For the video, the start position is (0.7 m, 0, 0.1 m) and the end position is (0, -0.3 m, 0.5 m).
• Assignment 4, due on Canvas before the beginning of class on Tues Nov 22: Chapter 8 exercises 2, 11, 14, and 17 (in the book after Nov 16, these same problems are numbered 2, 10, 13, and 16). Chapter 9 exercises 21, 22, and 23. Additionally:

(a) Write the spatial inertia matrix in the link center-of-mass body frame for each of the six links of the UR5, given the center of mass frames and mass and inertia specified in the UR5 URDF.

(b) Assume gravity is 9.81 m/s^2 acting in the negative z direction of the space frame. Write code that uses ForwardDynamicsTrajectory to simulate the robot falling in gravity for 3 seconds. The robot starts at rest from the zero configuration, and all joint torques are zero. Use dt = 0.01 seconds and intRes = 10 (10 Euler integration steps per dt). Your code should create a csv file of the configurations at 0.01 second intervals (you should get ~300 configurations, since you are simulating for 3 seconds with dt = 0.01) and use that to create a V-REP video of the robot falling. Turn in your code that uses ForwardDynamicsTrajectory, the input you used to your code, and your movie. Note: You are responsible for a correct dynamic simulation. If you discover a problem with the code ForwardDynamicsTrajectory, you are responsible for fixing it so you get a proper simulation. Get started early!

• Assignment 5, due on Canvas Friday Dec 9 by 9:00 AM. Make sure to download the updated version of the book, dated November 24. Chapter 13 Exercise 33, including videos for parts (d) and (e). This exercise uses the KUKA youBot mobile manipulator scenes on the V-REP page. The gains corresponding to the linear and angular components of the P and I errors can have different values, accounting for the different units of linear and angular error.

Approximate Syllabus

Configuration Space

reading: Chapter 2

• degrees of freedom, Grubler's formula, parameterizations, holonomic and nonholonomic constraints

Rigid-Body Motions

reading: Chapter 3

• rotation matrices, angular velocity, and exponential coordinates
• transformation matrices, twists, and exponential coordinates
• wrenches

Forward Kinematics

reading: Chapter 4

• product of exponentials formula in base frame and end-effector frame
• the URDF

Velocity Kinematics and Statics

reading: Chapter 5

• Jacobians: space, body, and other notions (e.g., velocity as time derivative of configuration variables)
• statics of open chains
• singularities, manipulability

Inverse Kinematics

reading: Chapter 6, but you may skip 6.1

• numerical inverse kinematics

Dynamics of Open Chains

reading: Chapter 8 (not 8.4)

• Lagrangian formulation,
• dynamics of a single rigid body
• Newton-Euler inverse and forward dynamics of open chains
• constrained dynamics
• actuation, gearing, and friction

Trajectory Generation

reading: Chapter 9, but you may skip 9.2 and 9.3

• definitions and time-optimal time scaling

Motion Planning

reading: Chapter 10 through 10.5.1

• overview, foundations, and complete path planners
• grid methods and the RRT sampling method

Robot Control

reading: Chapter 11

• motion control and force control

Grasping and Manipulation

reading: Chapter 12

• contact kinematics, planar graphical methods, and form closure
• contact forces, planar graphical methods, and force closure, Chapter 12.2
• other manipulation, Chapter 12.3

Wheeled Mobile Robots

reading: Chapter 13

• modeling, motion planning, and control for omnidirectional and nonholonomic mobile robots
• it is highly unlikely we will get here!