EC2300 Control Systems Lab 4 – Steady-State Performance
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Lab 4r4.doc, 5 April 2006
Lab 4: STEADY-STATE PERFORMANCE
Section 1 -- Background Information
The steady-state error is the difference between the output (actual state) and the input (commanded state)
after the transient response has passed. The primary source of steady-state error is due simply to the type
of input (step, ramp, or parabola) that stimulates the control plant. Another cause is attributed to the system
type as defined by the form of the transfer function G(s). The effects of these error sources will be
observed during this lab procedure.
Section 2 – Procedure
2.1 Steady-State Error of the Control Plant with Step Input
For the first part of this lab, the control plant will be excited with a step input, and the steady-state error
determined.
2.1.1 Setup the Control Plant. The torsion system will be set up with two (2 each) weights loaded on the
bottom disk only. The weights are secured 180 degrees apart from each other such that the outside edge of
each weight is tangent to the 9-cm radius line (last line on the disk).
2.1.2 Start the ECP software program.
2.1.3 Record the ECP Station Number, as each ECP station will have slightly different system
characteristics.
2.1.4 Energize the control system by pushing the “ON” button on the ECP controller.
WARNING
The system is now energized and will rotate at potentially high speeds when a
control voltage is applied to the motor of the torsional system. At any point the
motion of the system can be stopped by pressing the OFF (red) button on the ECP
controller box.
2.1.5 Setup the ECP Program
a. Set the system units to degrees: SetupàUser Units, select degrees
b. Select SetupàControl Algorithm.
• Select Continuous, then PI with Velocity Feedback
• Click on Setup Algorithm. In the new window, enter the following:
o Kp = 0.2
o Kd = 0.02
o Ki = 0
o Feedback – Encoder 1
• Implement Algorithm, then click OK
c. Select Dataà Setup Data Acquisition
• Sample Period (servo cycles) = 2
• Selected Items should be Commanded Position and Encoder 1 Position
d. Select CommandàTrajectory
• Select Impulse and Unidirectional moves. Click Setup.
• Select Closed Loop Impulse and set
o Amplitude (degrees)=180
o Pulse width (msec) = 3000
o Reps = 1
o Dwell Time (msec)= 0;
