INDUSTRIAL INDEXING SYSTEMS IIS MSC-250 2½-AXIS SERVO CONTROLLER

The Industrial Indexing Systems Motion Control System MSC-250 is a microprocessor

based, position-loop controller. It is a dual 32-bit technology, 2½-axis, closed-loop

controller that works with separate servo drives, motors, and encoder feedback devices to

accurately fix the position of the motor shafts.

The MSC-250 controller is part of the MSC family of controllers and peripheral equipment

produced by Industrial Indexing Systems. It uses the same Macroprogram control

language already familiar to users of the MSC-850 family of controllers and is fully

compatible with this family of controllers.

This manual describes proper installation, operation, and troubleshooting procedures for

the MSC-250 controller. The manual assumes no prior knowledge of Industrial Indexing

System equipment. It does assume knowledge of proper mechanical, electrical, and

electronic maintenance and safety procedures. If the equipment is used in a manner not

specified in this manual, the protection provided by the equipment may be impaired.

Information in this manual is subject to change without prior notification.

The objective of the indexing system is to accurately control the position and speed of

rotation of a motor shaft at any given time. This control may be used to move the load a

specific distance (index) or to a specific location (position). It also may be used to move

the load in a pattern duplicating the motion that would be produced by the action of

mechanical cam, remembering that motion can occur in both clockwise and

counterclockwise directions.

The components of the basic indexing drive system form two information loops. The

position loop is a closed-loop which consists of the controller, drive, motor, and feedback

device. The controller, continually compares motor position, derived from the feedback

pulses received from the drive, with the desired position calculated within the controller.

Any difference between calculated position and actual position results in a corrective

command signal being sent to the drive. The drive then corrects motor position by

adjusting its velocity loop. The objective of the position loop is to keep the actual position

equal to the commanded position.

The velocity loop is also a closed-loop system. The drive continually compares motor

velocity, derived from the feedback device, with the magnitude of the command signal

generated by the controller. Any difference causes the drive to alter the current to the

motor, which in turn changes the motor velocity. The objective of the velocity loop is to

keep actual velocity equal to commanded velocity.

The position loop and velocity loop are independent loops, but the controller uses the

velocity loop to achieve movement to the desired position. When data is received by the

controller specifying a movement, the controller calculates the time required to accelerate

to maximum speed and to decelerate from maximum speed. It then calculates the time at

maximum speed necessary to complete the movement. This information is then

transmitted to the drive by the controller.

SYSTEM FUNCTIONS

The MSC-250 servo controller can simultaneously and independently regulate two motion

axes. Programming of the motion control is supplied by a separate computer program or

by a pre-programmed PROM (Programmable Read-Only Memory). Once loaded, the

program is stored in non-volatile memory in the controller.

The controller uses two processors. One processor is labeled "Main Microprocessor" and

the other is labeled "Axis Microprocessor" (refer to "Section 1.3 - Components"). These

two processors communicate through two kilobytes of dual-port RAM (Random Access

Memory) for maximum processing and communication speed. (Dual-port RAM is memory

which is mapped in the same location on each processor and is simultaneously accessible

by both processors.) The main microprocessor processes information from the operating

program, communication ports, and I/O (Input/Output) modules. The axis microprocessor

processes information from the feedback devices and sends commands to the drives.

The MSC-250 can control one or two motion axes, providing precision position-loop control

to each axis. The controller can provide indexing, positioning, cam following, and profiling

control. It can also be used as a passive position sensing device. A third axis (referred to

as a half axis) can only monitor information received from a master axis or controller or

from the pseudo axis. It does not provide any control functions.