Prescott, Arizona Campus
Department of Electrical and Computer Engineering
EE 402 Control Systems Laboratory
Fall Semester 2014
Lab Section 51: Thurs 9:10 – 11:50 am
Lab Section 50: Thurs 1:25 – 4:05 p.m.
in KEC 122
Lab Instructor:
Dr. Stephen Bruder
Lab 08
Control System Specifications - Part I
Date Experiment Performed:
Thursday, Nov 06, 2014
Date Report Submitted:
??, 2014
Group Members:
Student # 1 Name & Email
Student # 2 Name & Email

Instructor’s Comments:
Comment #1

Comment #2
Grade:
EE 402 Control Systems Lab
Fall 2014
1. INSTRUCTIONS
A 10 min in-class presentation will be required for this lab (no report).
 Tentative presentation dates: Mon, Nov 10 and Wed, Nov 12
Presentation Format:
1. Introduction and Background (1-2 slides)
 What system did you choose (CL speed or pos)?
 Top level – What are you trying to accomplish?
 Motivation for your design?
2. Design Specifications (1-2 slides)
 Time/Freq domain specs?
 Steady-state specs?
 Sensitivity analysis?
 Other?
3. Preliminary Design (2-3 slides)
 Lead/Lag controller?
 PID controller
 Simple gain?
 Analytical design (solve for controller parameters)
 Circuit design (if necessary, e.g., Lead/Lag)?
4. Simulation Results (2-3 slides)
 Use MATLAB and/or Simulink to model the system
 Show predicted performance (anticipated results)
 Root-locus, Bode plots, time domain response, sensitivity, …
5. Conclusion/Summary (1 slide)
 What challenges do you anticipate during implementation?
 How will you implement your design (a top-level block diagram of your
solution?)?
 Any other closing remarks
2. BACKGROUND
The goal of this experiment is to write a specification for the system whose performance we
characterized over the last few weeks. After the specification is written and approved by your
instructor, you will spend the next couple of weeks designing, implementing and demonstrating a
controller that meets your specification (to include a presentation).
The first question that comes to most students’ minds when presented with the task of writing
a specification is what are the control systems characteristics that I can use for specifications?
The first characteristic that most systems require is that the system is stable. For a bounded input
to the system, the output should also be bounded.
Names of Students in the Group
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EE 402 Control Systems Lab
Fall 2014
If the system is stable then the next question is how does the system respond to the input?
Since the exact input may not be known, the accepted procedure is to specify how the system
will respond to standard inputs. The most common standard inputs are the step, ramp, and
parabolic inputs. Since control systems respond in the time domain, specifications are frequently
given as time domain responses to these standard inputs. For example, for a first order system
the system time constant or system rise time may be used to describe how fast the system must
respond to a step input. For second order systems, rise time, settling time, percent overshoot
and/or damping ratio may be used to characterize the performance of the system’s response to a
step input. Systems whose order is greater than two may also be characterized by these same
characteristics to the extent that their responses resemble the lower order systems. These
specifications deal with the system’s transient response. Next we look at a system’s steady-state
response.
When a system’s output does not match its input a steady-state error results. In some
applications it is necessary to minimize these errors. The usual approach is to specify the
allowed steady-state error to one of the standard inputs. A very common specification is that
there is zero steady-state error to a step input.
Besides the desired inputs, there are undesired inputs. These undesired inputs, called
disturbances, generally increase the steady-state error. A good control design can eliminate or
substantially reduce the impact of disturbances. A specification might be that the system follows
the input within a certain percentage error even if a certain magnitude disturbance is present.
Another possible system specification deals with the uncertainty in the model of the physical
system and the nature of the system’s change (age) over time. Both lead to a requirement to
design controllers that achieve the design goals in spite of deviations between the model and the
physical system. The closed-loop physical system’s performance should be insensitive to these
deviations. This suggests that a specification on the sensitivity of the closed-loop system to
changes in the physical system is required. A deep space probe is an example of a system whose
guidance control must operate for many years in a hostile environment that can change the space
vehicle in unknown ways. Requiring such a specification is one way of trying to minimize the
impact of those changes.
Names of Students in the Group
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EE 402 Control Systems Lab
Fall 2014
Most of the system specifications so far have been in the time domain. Systems can also be
characterized in the frequency domain. There are advantages and disadvantages to designing
controllers in the frequency domain over a time domain design. For example, in the time
domain, it is easy to characterize the transient response of the system. However, an accurate
transfer function is necessary to complete the design of the controller. Using frequency-response
methods, a controller can be designed without ever needing to derive a transfer function. This is
an advantage if you cannot get inside the system but can only make external measurements since
a few sinusoids applied to the input and compared to the output can produce a Bode plot.
Generally time and frequency methods complement each other. In the frequency domain, the
most common system characteristics are bandwidth, gain and phase margins, dc and loop gain,
and peak in the closed-loop frequency response. Steady-state accuracy, transient response,
stability, sensitivity and disturbance rejection can all be analyzed in terms of these characteristics
of the frequency response.
Whether the specification is in the time or frequency domain, cost and simplicity of the design
are frequently overriding considerations. If a competitor can produce a cheaper product of equal
quality then your design will have a short life. A related consideration is that your design may
have to use products that are on hand in your employer’s warehouse rather than purchase new
products.
3. PRELAB ASSIGNMENT
Select either closed-loop speed or closed-loop position as your system. Propose an initial
design objective and a list of early specifications which might be pursued. No two student groups
will be allowed to pursue the identical (discretion of the instructor) design specs.
4. EXPERIMENT 8
In consultation with your lab instructor, develop a set of more detailed specifications that the
controller, to be implemented in the next lab, will meet.
Names of Students in the Group
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