Motor; Amplifier (Driver); Encoder - Galil Motion Control DMC-18 2 Series User Manual

Computer

Motor

A motor converts current into torque which produces motion. Each axis of motion requires a motor
sized properly to move the load at the required speed and acceleration. (Galil's "Motion Component
Selector" software can help you with motor sizing). Contact Galil for more information.
The motor may be a step or servo motor and can be brush-type or brushless, rotary or linear. For step
motors, the controller is capable of controlling full-step, half-step, or microstep drives. An encoder is
not required when step motors are used.

Amplifier (Driver)

For each axis, the power amplifier converts a +/-10 Volt signal from the controller into current to
drive the motor. For stepper motors, the amplifier converts step and direction signals into current.
The amplifier should be sized properly to meet the power requirements of the motor. For brushless
motors, an amplifier that provides electronic commutation is required or the controller must be
configured to provide sinusoidal commutation. The amplifiers may be either pulse-width-modulated
(PWM) or linear. They may also be configured for operation with or without a tachometer. For
current amplifiers, the amplifier gain should be set such that a 10 Volt command generates the
maximum required current. For example, if the peak motor current is 10A, the amplifier gain should
be 1 A/V. For velocity mode amplifiers, a 10 volt command should run the motor at the maximum
speed.

Encoder

An encoder translates motion into electrical pulses which are fed back into the controller. The DMC-
18x2 accepts feedback from either a rotary or linear encoder. Typical encoders provide two channels in
quadrature, known as CHA and CHB. This type of encoder is known as a quadrature encoder.
Quadrature encoders may be either single-ended (CHA and CHB) or differential (CHA, CHA-, CHB,
CHB-). The DMC-18x2 decodes either type into quadrature states or four times the number of cycles.
Encoders may also have a third channel (or index) for synchronization.
For stepper motors, the DMC-18x2 can also interface to encoders with pulse and direction signals.
There is no limit on encoder line density; however, the input frequency to the controller must not
exceed 3,000,000 full encoder cycles/second (12,000,000 quadrature counts/sec). For example, if the
encoder line density is 10000 cycles per inch, the maximum speed is 300 inches/second. If higher
encoder frequency is required, please consult the factory.
4 ● Chapter 1 Overview
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DMC-18x2 Controller
Encoder
Figure 1.2 - Elements of Servo systems
Power Supply
Amplifier (Driver)
Motor
DMC-18x2