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Mid-Semester Examination for CS551/CS651: Dependable Computing - Fall 2004 - Prof. John Kn, Exams of Computer Science

University of Virginia (UVA)Computer Science
Prof. John Knight

A mid-semester examination for the dependable computing course offered by the computer science department at the university of virginia in fall 2004. The examination consists of multiple-choice questions related to the robosurg system, a machine tool designed for use in operating rooms to assist surgeons in joint replacement surgery. A system description, a figure illustrating the system design, and a series of questions covering topics such as hazards and accidents, reliability, fault trees, and state schemas.

Typology: Exams

Pre 2010

Uploaded on 03/19/2009

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. This is a closed book, closed notes examination.
. Write your answers on the examination paper in ink or legible pencil.
.If your answer cannot be read or understood, or if your answer is vague or confused, it will be
marked wrong.
. In any question, make any assumptions that you need to but document your assumptions.
. The number in parentheses after each question is the number of points allocated to that ques-
tion.
NAME (Print Legibly. All Capitals):
PLEDGE (Write Out In Full And Sign):
Graduate Students (CS651) Sections A and B
Undergraduate Students (CS551) Section A
CS 551/CS651
DEPENDABLE COMPUTING
MID-SEMESTER EXAMINATION
FALL 2004
Time Limit - 75 Minutes
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Download Mid-Semester Examination for CS551/CS651: Dependable Computing - Fall 2004 - Prof. John Kn and more Exams Computer Science in PDF only on Docsity!

. This is a closed book, closed notes examination. . Write your answers on the examination paper in ink or legible pencil. . If your answer cannot be read or understood , or if your answer is vague or confused, it will be marked wrong. . In any question, make any assumptions that you need to but document your assumptions. . The number in parentheses after each question is the number of points allocated to that ques- tion.

NAME ( Print Legibly. All Capitals ):

PLEDGE ( Write Out In Full And Sign ):

Graduate Students (CS651) Sections A and B

Undergraduate Students (CS551) Section A

CS 551/CS

DEPENDABLE C OMPUTING

MID-S EMESTER EXAMINATION

FALL 2004

Time Limit - 75 Minutes

The following system description is used in some of the questions in this examination:

The Robosurg system is a machine tool designed for use in an operating room to assist surgeons in joint replacement surgery. It operates by cutting bone to a specific shape that accepts a joint-replacement implant. Robosurg is much more precise than human surgeons and the benefits to the patient of robotic surgery are tremendous. Needless to say, the cutting process is complex and computer controlled. The cutting tool moves in an elaborate pattern to shape the bone. The location of the patient and all the Robosurg equipment is determined precisely by a 3D tracking system. Obviously the concern that Robosurg’s developers have is the possibility of it cutting something that it should not, for example if the software calculated the wrong direction or distance for the cut. In an effort to prevent this, the cutting edge of the tool is monitored by a second computer system that computes the tool’s planned track separately. The primary computer and the tracking computer have to agree in order for Robosurg to proceed. The following figure illustrates the system design:

Monitor Computer

Cross Check

Control Computer

Tracking System

Cutting Tool

Patient

Page score

  1. Generally, it is considered desirable for the input to the top element of a fault tree to come from an AND gate. Explain why this is the case. (10)
  2. In general, degradation faults are easier to tolerate than design faults. Explain why this is the case. (10)
  3. Draw the top two levels of the fault tree for the Robosurg system. The top level is to be the hazard you identified in the question above and the second level is to have the appropriate event content. Make any assumptions that you need to about how the system works. (20)

Page score

  1. The software controlling the Robosurg cutting mechanism receives a three dimensional target coordinate to which the cutting head is to be moved from the system’s guidance software. Each value in the coordinate is an integer measuring millimeters within an established frame of reference. Write a Z state schema that could be used to specify a target coordinate including invariants that require each new location to be less than limit millimeters from the head’s cur- rent location. The cutting head starts a sequence of moves at the origin. (30)
  2. The Robosurg cutting head uses three drive motors to position the head in the X, Y, and Z directions. Draw the FMECA table for the failure of the X drive motor in the cutting head. Assume the motor failure modes are: (1) fails by continuing to run after being commanded to stop; and (2) fails by stopping when it should be running. (30)