General Catalog - Galil - #9

Galil Controllers

il Description

Servo Motor Compensation Features

Galil controllers provide a compensation filter,which includes a PID (Proportional-Integral-Derivative) filter followed by a notch filter and a low-pass filter.The compensation also includes velocity and acceleration feedforward.All filter parameters are adjustable,allowing servo system tuning for best performance. Dual loop control is provided for reducing the effect of backlash.

The dual-loop (DV) feature enables the controller to compensate for mechanical backlash.Typically,dual-loop systems use a rotary encoder on the motor and a linear encoder on the load (most Galil controllers accept inputs from two encoders per axis as a standard feature). Dual-loop control changes the standard PID control and closes the position loop with the load encoder ("PI") and derives the damping terms ("D") from the motor encoder.This method provides smooth and accurate control along the motion path regardless of backlash.

Most Galil controllers also include a sinusoidal commutation feature that allows designers to use lower-cost servo drives. This feature assures smooth motion and reduces torque ripple when using brushless motors. Each axis of sinusoidal commutated motion requires two DAC outputs that are phase shifted by 120°.The servo amplifier generates the third commutation signal.The commutation can be initialized with or with­out hall sensors.Two controller axes are required for each brushless motor. For example, a two-axis controller is required to drive one brush-less motor with sinusoidal commutation.

Command Language

Galil's Command Language is comprised of intuitive, two-letter, English-like ASCII commands that make programming quick and easy. For example,the "BG"command begins motion while the "SP 2000, 4000"command sets the speed of the X-axis as "2000"and the Y-axis to "4000". Commands are included for system set-up,tuning, prescribing motion, error handling and application programming. Custom commands can be created upon request.

One of the more powerful features of all Galil controllers is their ability to store and execute complex application programs designed by the user. Application programs can be downloaded directly to the con­troller and executed without host intervention.The main benefit is that this frees the PC for system-level tasks. In fact,Galil controllers permit multitasking,which allows up to eight programs to execute simultane­ously. Also, special commands are available for application programming including event triggers, IF/THEN/ELSE statements,conditional jumps, subroutines, symbolic variables and arrays.

www.galilmc.com / Galil Motion Control, Inc.