Motion Controllers Information
Motion controllers are components that range from ON/OFF devices with simple linear controllers to complex, user programmable modules that act as controllers within complex integrated multi-axis motion systems. Applications include all types of industrial processing, packaging, and machining / forming operations. Performance, configuration, motor drive style, feedback type, and other I/O are important parameters to consider when searching for motion controllers.
How to Choose the Right One
Important performance specifications to consider when searching for motion controllers include number of axes, update time, D/A resolution, and type of motion supported. The number of axes controlled usually correlates to number of motor outputs; include all master and/or slave axes. Update time is the time between position, speed or other feedback updates. D/A resolution represents the "fineness" of the analog drive signal as converted from the digital command signal. The type of motion supported describes the ability for coordinated/interpolated motion of multiple axes. They include simple, linear and/or circular, complex, and user defined. Important configuration parameters to consider include form factor and computer interface. The form factor for motion controllers can be stand alone or board or module. A stand alone controller can be run independently of a host computer. A board or module plugs into a computer, a rack, or a backplane. Computer interface choices include PCI, PC / 104, ISA or EISA, STD bus, Multibus, VME, VXI or MXI, PXI bus, parallel port, and GPIB or IEEE-488 or HPIB.
Matching the Parts
Choices for motor drive style for motion controllers include DC brush servo, DC brushless servo, AC servo, stepper, and hydraulic or pneumatic. A motor or amplifier drive acts as an interface between a controller and the motor. The drive must match the control signals (voltage and power levels) and signal type (analog or digital). The drive produces power conversion, amplification, and sequencing of waveform signals. Choices for feedback control include incremental encoder, absolute encoder, resolver or synchro, magnetostrictive, Hall effect potentiometer, and auxiliary position input. Other input and output choices include tachometer input, limit or home or abort switch input, joystick input, auxiliary discrete I/O, and auxiliary analog I/O.