Editing Servo tuning basics
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− | + | Driving a servo motor is much like driving a car. Driving a car has many similarities including the key concepts of torque, velocity and position control. Most of this happens in the driver's head the same way than a servo drive does with a motor. | |
− | + | ==Driving (a.k.a servoing) a car== | |
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− | ==Driving (a.k.a servoing) a car== | + | |
Driving a car to a destination is much like driving a servo motor to it's destination position. The analogies in between are: | Driving a car to a destination is much like driving a servo motor to it's destination position. The analogies in between are: | ||
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*Controls car's velocity based on the speed meter value and speed limit | *Controls car's velocity based on the speed meter value and speed limit | ||
*Controls car's position based on trip meter's reading or by observing location trough the windshield | *Controls car's position based on trip meter's reading or by observing location trough the windshield | ||
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− | == | + | ==Driver as a controller== |
− | === | + | ===What is a controller gain and a PI controller=== |
Controller gain means '''sensitivity to change output''' due to ''tracking error'' (the difference between setpoint and feedback). | Controller gain means '''sensitivity to change output''' due to ''tracking error'' (the difference between setpoint and feedback). | ||
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In servo drive case, this means that each motor type and mechanical axis need to be tuned separately. However, if axis and motors are identical, then the same gains should work equally. | In servo drive case, this means that each motor type and mechanical axis need to be tuned separately. However, if axis and motors are identical, then the same gains should work equally. | ||
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==Gain tuning (car) example== | ==Gain tuning (car) example== | ||
The following series of images illustrate an imaginary car driving scenario where the driver acts as velocity controller of the car. The magnitude of PI gain values equal the driver's aggressivity of controlling the pedal to reach the desired speed. | The following series of images illustrate an imaginary car driving scenario where the driver acts as velocity controller of the car. The magnitude of PI gain values equal the driver's aggressivity of controlling the pedal to reach the desired speed. | ||
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The response can be improved further by introducing a limit to the slew rate of setpoint signal. The controller behaves optimally when the system is able to follow the setpoint continuously with little tracking error. In this case the gains could be same as before, P=50 I=25. | The response can be improved further by introducing a limit to the slew rate of setpoint signal. The controller behaves optimally when the system is able to follow the setpoint continuously with little tracking error. In this case the gains could be same as before, P=50 I=25. | ||
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