RoboteQ AX500 manual PID tuning in Speed Mode

PID tuning in Speed Mode

	Proportional
	Gain
Desired Speed	E= Error
-	dt
	dE

x

xΣ Output

Tachometer A/D

or

Optical Encoder

Measured Speed

Integral Gain

dE

dt

x

Differential

Gain

FIGURE 45. PID algorithm used in Speed mode

PID tuning in Speed Mode

As discussed above, three parameters - Proportional Gain, Integral Gain, and Differential Gain - can be adjusted to tune the Closed Loop Speed control algorithm. The ultimate goal in a well tuned PID is a motor that reaches the desired speed quickly without overshoot or oscillation.

Because many mechanical parameters such as motor power, gear ratio, load and inertia are difficult to model, tuning the PID is essentially a manual process that takes experimenta- tion.

The Roborun PC utility makes this experimentation easy by providing one screen for chang- ing the Proportional, Integral and Differential gains and another screen for running and monitoring the motors. First, run the motor with the preset values. Then experiment with different values until a satisfactory behavior is found.

In Speed Mode, the Integral component of the PID is the most important and must be set first. The Proportional and Differential component will help improve the response time and loop stability.

In the case where the load moved by the motor is not fixed, tune the PID with the mini- mum expected load and tune it again with the maximum expected load. Then try to find values that will work in both conditions. If the disparity between minimal and maximal pos- sible loads is large, it may not be possible to find satisfactory tuning values.

Note that the AX500 uses one set of Proportional Integral and Differential Gains for both motors and therefore assumes that similar motors, mechanical assemblies and loads are present at each channel.

AX500 Motor Controller User’s Manual 77