Servo CDI Programmable Digital Ignition

The motor is used to provide the mechanical output of the system, and to move the potentiomer to close the loop. For high power servos three-phase motors can be used. Potentiometer: For standard industrial applications a simple potentiometer can be used to get the current position of the servo. For high accuracy CNC systems an encoder with high number of pulses
Servo CDI Programmable Digital Ignition - schematic

will be needed. Analog controllers usually are only a "P" controller, they work fine if the system can keep the current position when the motor is off, but they create a "position error" when a fixed strenght is applied to the servo, because the system needs a small error to get the necesary torque to keep its position. PID controller fix the "position error" with the "I" parameter, and also can increase the response speed for the target changes with the "D" parameter. The controller reads the current position from the potentiometer or encoder, and substracts from the target position and gets the "error" variable. This variable tells the controller how far is from the desired position. By using the "P", "I" and "D" coefficients the controller gets the "control action" to be sent to the motor driver. Motor Driver: As the motor needs to move in two directions usually a H-driver is used to reverse polarity. A PWM output is used to control the motor power. In addition with large motors a current limitation is needed inside the driver to prevent the MOSFETs/IGBTs to be damaged when starting, changing direction or appliying a load to the motor. Kp, this is the "proportional" coefficient of the controller. The servo can work by using only this value. The "error" variable is multiplied by this value to get the "control action". Small values will cause the system to move slowly to the target position. High values will cause the...

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