Here are some examples of variable tuning, in which we intend to give an idea of ​​some procedures to follow to make the system work optimally controlled.

MANUAL TUNING WITH A MULTIMETER

Initial Tuning System Manual in General

1. Set the integral gain (kJ) to 0.

2. Adjust the differential gain (kD) to 0.

3. Set the proportional gain (kp) in 20% of its maximum value.

4. Enable the control and run at constant load. Adjust the reference value to the midpoint of their rotation.

5. Note the feedback signal with a multimeter.

6. Increase (kp) slowly until the feedback process begins to increase. The goal is to reach the feedback ½ full range of its full scale. If oscillations occur, reduce a little (kp) and continue the next step.

7. Change the reference value in about 20%, and observe the process feedback signal (or the engine, if appropriate).

8. If the response has been steady, increase (kp) until the feedback process to be swinging a little step 7. Then slowly decrease (kp) until the feedback process is stable. This parameter is defined.

NOTE: While operating with constant load, the feedback value will not equal the reference value. This will be tuned later. See Figure 2-26.

9. Enable the control and run with a constant load. Adjust the reference signal to half its maximum value. Maneuver (kI) to a small value, eg 0.1 Hz Note the feedback signal of the process, which should increase slowly over a period of several seconds to reach exactly the reference value. Increase (KI) to reduce the time it takes to eliminate the steady-state error. If the system starts to oscillate or become unstable, slow (kI). An integral gain is too high process easily create instability in almost any system. Use the minimum gain value necessary to achieve proper operation. See Figure 2-27.

10. If the system is unstable or unresponsive, check the sizing of the motor and control over the load. Also check if the parameter Maximum speed is high enough. In some cases this parameter can be the limiting factor, or perhaps the motor assembly and control is too small for the application.

MANUAL TUNING WITH AN OSCILLOSCOPE

An increase in the proportional gain (kp) will result in a rapid response, and cause excessive proportional gain overshoot (overshoot or overshoot) and transient oscillations (ringing). By decreasing the proportional gain will result in a slower response, and reduced the overshoot and transient oscillations caused by an excessive proportional gain. If the proportional gain and integral gain are set with values ​​that are too close to each other, can also occur a condition of overshoot.

The Hz value of the integral gain can be defined as any size from 0 to 10Hz. The definition (k) 0, integral compensation is eliminated, resulting in a proportional rate loop.

This selection is ideal for systems where overshoot must be avoided and do not require a substantial degree of "rigidity" (the ability to maintain unity despite reference speed variable torque loads).

By increasing the value of the integral gain increases the low frequency gain and stiffness of the unit, an integral gain will produce excessive overshoot transient speed to control and can result in oscillations. The typical setting is 1 to 4 Hz.

To manually tune the speed control proceed as follows, noting the signal oscilloscope measured variable:

1. The integral gain should be at least (It defines "0" as no integral gain and "10" as the maximum integral gain).

2. The differential gain to a minimum.

3. Set the parameter (kp) to achieve an adequate response to the staggered control reference value.

4. Increase (k) to increase the rigidity of the unit.

It is convenient to monitor the response of the feedback step using a storage oscilloscope. The following figures will illustrate how an oscilloscope feedback response under various settings of the profits. These waveforms show the response for a control set point step from zero to 4 / 5 of full scale.

Figure 2-28 shows the response of a proportional rate loop when the integral gain is set to 0 Hz value of the proportional gain is, however, too low.

Figure 2-29 is an example of a proportional gain too: note the transients in the response of the feedback process.

Figure 2-30 shows the optimal response for this particular system (process proportional gain = 100, and integral gain = 2.00 Hz).

In Figure 2-31 the integral gain was set too high (2.00 Hz) for the value of the proportional gain (10). As a result, there are transients and excessive overshoot. Therefore the proportional gain should be increased or reduced process integral to the process gain.