Lab 05 (Servo)
Lab 05 (Servo)
Lab 05 (Servo)
Equipment
CE110 CE122 CE2000L : Servo Trainer Apparatus : I/O Digital Interface (Serially connected to a PC) : Digital Controller (Lite Software) Installed on a PC
2. Make the following connections between CE122 and CE110 while all equipments remain off:
Table 1
CE110 Output from Tachometer Output Shaft Position Indicator 10V Reference Set Potentiometer GND
3. On the desktop of your PC, start CE2000 Lite and open CE110 file as saved in the home directory of this software. Make the necessary connection as in Figure 1:
Figure 1.
4. After completing the necessary connections, run your circuit. 5. Slowly increase the fine potentiometer voltage until the motor just starts to turn. This is the size of the positive dead-zone for the motor drive amplifier; enter it into the first row of the Table 2 provided. Increase the potentiometer to 1V; record the corresponding motor speed from the speed display on the CE110 front panel.
1-4
6. Increase the coarse potentiometer voltage in 1V steps to 10V and record the corresponding speed in Table 2.
Table 2.
7. Repeat the above procedure with the clutch engaged, and complete Table 3. Avoid running the Servo Trainer at high speed for prolonged periods with the clutch engaged, as this may cause excessive wear of the gearbox.
Table 3.
Motor Drive Voltages (Positive) Dead-Zone Size=? 2 3 4 5 6 7 8 9 10 8. Plot the results from Table 2 and Table 3.
2. Readjust the previous connection as in Figure 2. 3. Set the target potentiometer to the speed sensor output (initially 1V) that you require then adjusts the coarse and fine potentiometers until the error bar graph is at a minimum. Enter the corresponding speed reading in Table 4. Repeat the process in steps of 1V for positive speed sensor readings. Plot your results.
Figure 2.
2-4
Table 4.
Figure 3.
Clutch engaged. Rear access panel firmly closed. Smallest inertial load installed.
3. Open and close the switches connected to the 'fast' and 'slow' potentiometers to turn the output shaft to the specified angles and enter the corresponding position sensor output in Table 5.
Table 5.
Indicated Angle () -150 -120 -90 -60 -30 0 30 60 90 120 150 4. Plot your results.
2. Make the necessary connection as in Figure 4 and then run your circuit. 3. Slowly increase the potentiometer output voltage to 4V, and observe the steady state error. (for Kp=1 this should be approximately 2V). Observe the error signal as integral action takes effect, as follows:- with Ki =0.1, press the integrator reset button and switch the integrator into the controller. (Note: it is most important to press the reset button each time an
3-4
integrator is switched into a circuit. Failure to do so can cause unpredictable results). Observe the speed slowly increase and the error signal slowly decrease to zero as the integrator output increases so as to cancel the error. Switch the integrator out of the circuit.
Figure 4.
4. Repeat the above procedure for Ki =0.5, 1, 2, 4, 6, and 10. Note that as Ki is increased the error is reduced to zero more rapidly until a point is reached when the error overshoots zero, and oscillates before settling to zero. The oscillations became more pronounced as the Ki is increased.
Figure 5.
2. The square wave generator signal provides a series of step changes in the reference signal, which can be used to investigate the step response of the servo-speed control system. Investigate the effect of proportional gain upon the control system step response by recording and printing the response for values of Kp =1, 0.1, and 0.01. Comment on the shape of the results in terms of speed of response and amount of overshoot. 3. Investigate the effect of integral gain upon the control system step response by setting Kp =1, and plotting the step response for values of Ki =0.5, 1, 5, and 10. Comment on the shape of the resulting step responses in terms of speed of response and amount of overshoot.
Conclusions
In completing this experiment you will have familiarized yourself with the Servo Trainer's main functions and measured their characteristics. You should comment on these characteristics (e.g. are they linear?) and discuss why the motor drive characteristic differs with the clutch engaged and disengaged. Discuss the effect of integral gain on steady state error. Discuss also the effect of changing proportional and integral gains on overall system response.
4-4