Hytec Electronics Ltd

Data Acquisition and Control

Stepper Motor Control and Drive Overview

The aim of this document is to show you how Hytec’s Stepper Motor Control and Drive system is put together, how it works and how it differs from similar systems. 

The system consists of two main parts. The controller is housed in an Industry Pack, either on a VME64x carrier card (8002) or mounted inside a 9010 IOC unit. Outside the VME64x crate or 9010, a standard SCSI-2 cable connects to a separate rack-mounting enclosure housing the driver system.
Looking at each part in more detail:

The CONTROLLER (Hytec 8601) has four independent channels of stepper control; each has four outputs and eight inputs. The outputs are STEP, DIRECTION and two Auxiliaries, which can be used, for example, to control motor current. The inputs are three limit switches including HOME; quadrature encoder signals(phase A, phase B and INDEX), drive system fault plus two spares.

Each channel of the controller features programmable START/STOP speed, HIGH speed and RAMP RATE. Each has a 32-bit step register for the current move and a 32-bit accumulator, which follows all movements. Moves can be either fully programmed, i.e. move the specified number of steps, or JOG, where the channel steps until the control bit is reset. Soft stop and hard abort are supported, along with stop on limit and stop at HOME. The accumulator can count step pulses issued or pulses from an incremental encoder.

The control bits for all channels are directly mapped into registers accessible by the host. A COMMON START facility is also included so you always have direct control over when a given channel or channels will start.

This controller then connects to the outside of the system via a ‘straight-through’ transition card and then to the INTERFACE ELECTRONICS mounted in the back of the driver system This performs basic signal conditioning and buffering of all inputs and outputs of the controller card, including RS422 level conversion for encoder signals if needed. It is fully opto-isolated in both directions. This interface then connects to the driver system motherboard directly and to auxiliary signals, such as encoders, through 15-way Cannon connectors.

The DRIVER (SMDS4) is a separate 3U high rack mounting unit. The driver houses four drive cards and a common logic card. The unit can use UNIPOLAR or L/R drive cards where the current limit is provided by external series resistors or BIPOLAR drive cards, where current control is by pulse width modulation. Both of these types are for use with standard four-phase hybrid steppers with four, 6 or 8 leads in full or half-step mode. Phase current can be up to 4 amps and is programmed by switches on each chopped drive card. We also have drive cards for three-phase and five-phase motors (Oriental Motor Company).

Any mixture of drive cards can be accommodated.

For standard power chopped-drive systems, the 24-volt PSU is integral. For higher power L/R systems it is normally external.

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Information in this document is subject to change without notice.
Other products and companies referred to herein are trademarks or registered trademarks of their respective companies or mark holders.
Our policy is one of continuous product development and the right is reserved to supply equipment which may vary slightly from that described.

Last modified: October 29, 2008