PC control and industrial networks have changed the way engineers design motion-control systems. Twenty years ago, control-component design generally started with a clean sheet of paper. Today, most engineers build motion systems out of readily available building blocks. One such building block, the PC-bus motion card, connects to the PC's physical backplane, and off loads the real-time, multi-axis motion algorithms from the host processor. Sharing memory with a host running SoftLogic software, motion cards allow tight integration of motion control with sequential functions, communications, and HMI (human machine interface).
These PC-bus motion-control cards, once available from a limited number of suppliers, are now widely available and have extremely advanced features. So who makes them and what makes their products unique? To answer those questions, Design News talked to 8 major suppliers of motion controllers for high-volume OEM applications that are designed to be fully integrated by the customer. We present some technology insights from an industry analyst, writeups from each company describing what's unique about its products, and a comprehensive table listing who makes what.
Oregon Micro Systems' PC68
Expandable up to 8 axis, the PC68's optional optically coupled I/O board is expandable to 144 I/O points. Controller highlights:
Conforms to the PC/104 specification (IEEE P996.1)
Controls 4 axes of servo or stepper, or a combination of both (expandable to 8)
Offers plus or minus 10V and 0-10V servo output signal support
Stepper-control signals include TTL-level step and direction with step rates of 1,044,000 pulses per second at a resolution of 0.01%
Encoder-feedback support for differential quadrature signals at a 4x resolution and at a rate of up to 4MHz
Includes 8 general-purpose I/Os, configurable as inputs or outputs (expandable up to a total of 168)
Up to 4 Mbit flash memory available for firmware storage and user program upload
Shielded input/output connectors or companion connection module (the IO68) with screw terminals are avail-able for wiring to motors, sensors, and encoders
Stepper models use a single +5V supply, at less than 1A typical, and the servo models use an additional plus or minus 12V supply at less than 0.5A typical.
Motion Engineering Inc.'s XMP Series
Software tools set the XMP apart by providing system developers with complete accessibility and control. Not a traditional CNC controller, the XMP Series is targeted at high-volume applications in the semiconductor equipment, industrial robotics, and electronic assembly industries.
XMP programming uses the MPI (Motion Programming Interface), an object-oriented, C/C++ programming interface. The MPI lets system developers build motion code the same way they build the machine: by creating individual software objects that reflect the components and actions of the hardware. The MPI supports Windows NT, Windows 95/98, and VenturCom real-time extensions. Depending on application requirements, MPI programs can execute on the host, the XMP, or be divided between both.
|MEI's XMP hardware architecture centers around the 32-bit floating-point SHARC DSP (150 MFLOPS). The SHARC gives the XMP the power to update 8 axes at speeds up to 10 kHz.|
Development utilities provide access to XMP hardware without programming. These include Motion Console, a graphical program for configuration and tuning and Motion Scope, a flexible graphing tool that allows developers to monitor MPI application status in real time. Both programs can access an XMP from a remote host over a TCP/IP link. Along with offering either PID or PIV control algorithms for each axis, the XMP includes a filter design toolkit to implement notch and low-pass filters to improve move times and system stability. Other XMP features include:
Optional scale interpolation to increase scale resolution 1,0243.
Position capture and position compare with latency under 2msec
On-the-fly trajectory modification
On-board sinusoidal commutation for up to 16 axes
2D compensation tables
|The flexibility of National Instruments' FlexMotion controllers results from an advanced architecture based on a Motorola 32-bit CPU, combined with an Analog Devices DSP and powerful FPGAs (field programmable gate arrays).|
National Instruments' FlexMotion
FlexMotion high-performance servo and stepper motor controllers, are used in PCI and ISA bus computers. Its multitasking, dual processor design accomplishes simple point-to-point and advanced trajectory profiles. Standard features include program memory, user variables, real-time multitasking, uncommitted digital I/O, and analog inputs.
Motion operation modes include linear vector interpolation, point-to-point, circular interpolation, helical, spherical, blended 3-axis motion contouring, and electronic gearing. On-board programs provide fully integrated I/O processing with motion sequenced to both digital and analog I/O as well as motion-parameter-based sequencing.
|Galil offers a 100+ price guarantee on its Optima Series controllers that assure the lowest price in the market in quantities of 100 or more. Typical pricing in quantities of 1000 is $100 per axis.|
The design leverages the broadly accepted Windows-based PC platforms in diverse networked automation, lab, and industrial applications. Designed for system throughput enhancement in measurement and automation applications, FlexMotion is compatible with standard software and user interface packages and is designed to interoperate with machine vision, data acquisition, and control products.
The programming tools portfolio includes standard drivers and function libraries for C, Visual Basic, DLLs, LabVIEW VIs, LabWindows/CVI, and a Windows configuration software package called FlexCommander. It is a free motion-builder application that provides out-of-the-box system setup, initialization, and operation. Fully functional interactive windows in FlexCommander allow for easy motion parameter setting, including position, velocity, acceleration, and more. Just click on a start-motion button and you can monitor status and feedback data interactively on-screen.
Galil Motion Control's Optima Series
The Optima Series, designed for OEM applications, is Galil's 4th generation of motion controllers. Standard features include high-speed communications with FIFO (first-in, first-out) and DMA channels, non-volatile program memory with multitasking, enhanced modes of motion (coordinated motion on multiple planes), higher encoder speeds, faster command processing, sinusoidal commutation, expanded I/O, and high-density 100-pin shielded cabling for noise immunity.
|Because most PCI motherboards are limited to 2-3 card slots in their backplanes, Tech 80's mezzanine-style Model 5845 PCI carrier combines data acquisition, I/O, networking or other motion functions in a single PCI slot.|
System setup and programming is facilitated by enhanced software tools such as WSDK for tuning and analysis, ActiveX Tool Kit for interface to Visual Basic, and a C-Programmers Tool Kit. Optima Series options include ISA, CompactPCI, and PC/104 bus cards. Or, users can choose a compact, rugged enclosure for stand-alone operation. The DMC-2000 stand-alone controller offers both a USB port and two RS232/RS422 ports for serial communications. Units come in 1- through 8-axis configurations and allow step or servo motors to be used on any combination of axes.
Precision MicroDynamics' MC8-DSP uses a powerful DSP, and has a number
of digital and analog I/O. The board's greatest asset is the depth at
which firmware and DSP
software can be modified.
Technology 80's Model 5845 PCI carrier
The Model 5845 PCI carrier is Technology 80's (Tech 80's) latest addition to its Modular Motion SystemTM (MMS). Its mezzanine-style design integrates industry-standard carrier boards and IP modules from the company and more than 50 international third-party vendors. Modules can be inexpensively replaced as application requirements change.
MMS offers design engineers flexibility and high function density for board-level controls, especially for PCI-based applications. For example, if a manufacturer of IC testing equipment needs to integrate servo and stepper control with bar-code reading and electrical and temperature testing within its PCI-based application, it could easily fit this entire application within one PCI slot.
The OEM could place on one carrier a servo and a stepper IP module from Tech 80 and, from third-party vendors, a CANbus module for interfacing with the barcode scanner, a GPIB module for electrical testing, and an A/D module for temperature analysis. Using the Model 5845 in this application would free up the remaining slots for additional needs or future expansion.
Precision MicroDynamics' MC8-DSP
A multi-axis, PC-based motion controller, the MC8-DSP offers firmware and software advances over the firm's existing products. Base hardware includes a 120MFLOP floating-point DSP, SRAM, 128 digital I/O, 16 DACs, 8 ADCs, and several timers. Also available are a variety of aPROMs that configure board firmware to provide a mixture of encoder inputs, Temposonic inputs, PWM outputs and stepper-motor outputs.
Additional PROMs, obtained for a nominal fee, let OEM customers specify custom firmware. Examples include: PROM-E24ST that provides eight 24-bit quadrature encoder inputs and eight 16-bit stepper-motor outputs; PROM-DXDT that provides eight 24-bit encoder inputs with special firmware for computing velocity estimates from quadrature encoder pulses; and other PROM options for Temposonic inputs, position registration, and PWM outputs.
Software support for the MC8-DSP is offered in various forms such as CMC-Soft-LIBTM, a motion control suite that offers standard routines for PID feedback, synchronized point-to-point moves, linear interpolation, circular interpolation, and electronic gearing. Programming is accomplished with standard Microsoft Visual C++ tools.
|Engineers using Acroloop's ACR8010 can use traditional serial communications or choose FireWire to simplify interconnection schemes and increase communication performance.|
For adaptive feedback control, in-verse kinematics, real-time signal analysis or other advanced processes, programming access to the board's floating point DSP is facilitated through Precision MicroDynamics' full-featured, real-time kernel for the ADSP-2106X SHARC, LIBeRTyTM. By using LIBeRTy, user tasks can be integrated with CMC-Soft-LIB modules at the DSP-level for optimal machine control and process analysis.
Delta Tau Data System's Turbo PMAC2-PC Ultralite
The Turbo PMAC2-PC Ultralite controller combines three technologies ona single-slot PC expansion board for power, flexibility, ease of use, and cost effectiveness. First, the Turbo PMAC CPU uses Motorola's 56300 family of DSP ICs. This CPU can control 32 axes simultaneously in up to 16 independent coordinate systems. It also executes advanced algorithms such as "multiple-move look-a-head" for ac-celeration control, and inverse kine-matics, that have until now been available only in high-end dedicated CNC and robotic controllers. Cost per axis comparable with simple low-end con-trol boards.
Second, it has the PMAC2 family's capability to perform motor phase-commutation and digital current-loop calculations, outputting phase voltage PWM commands to simple "power-block" amplifiers. By combining these calculations with the traditional trajectory and servo calculations in the controller, setup is simplified (there are no settings in the amplifier) and performance is increased (delays are minimized, permitting higher gains).
Finally, it uses the 125 Mbit/sec MACRO ring interface to communicate with the actual interface circuitry. Only two conductors, either fiber optic or RJ-45 twisted pair, leave the PC. The interface circuitry can be placed anywhere on the machine where it is most convenient. It can either be built into an amplifier with its own MACRO interface, or on Delta Tau's "Compact MACRO Station." The station pro-vides interface circuitry for multiple axes (just like on a traditional PMAC or PMAC2 controller), permitting connection to standard analog or digital amplifiers, sensors, flags, and general-purpose I/O.
Acroloop Motion Control Systems' ACR8010
Acroloop's latest generation, the ACR8010 motion controller, is capable of handling 1-8 axes per board. Features include:
32/64 bit floating point DSP
Flexible open architecture and command set
On-board operating system independent of the PC ensures real time execution and safe control even if the PC crashes
Calculates new multi-axis trajectory every interrupt to 5,000 points/sec
Controller can interrupt the host and handle simultaneous binary and ASCII communication for streamlined data transfer and sharing of control
Simultaneous PC-bus and serial communications for diagnostics and trouble shooting to reduce development time
Over 15,000 pre-programmed hardware registers for access to all motion-control parameters and flags for use in on-board motion and PLC or PC programs
All Acroloop products have identi-cal hardware register memory maps to reduce trouble-shooting time and devel-opment time, as well as to allow consistent field service
Built-in encoder-loss detection for hardware protection in machine run-away and insures fail-safe conditions
Built-in watchdog relay for embedded-amplifier enable and emergency-stop routines
Built-in PLC that is multi-tasked and compiled on-the-fly for independent machine logic control with a 2-5 millisec scan rate
All digital I/O is completely programmable and is 24V-dc and optically isolated with an isolated on-board circuit for industrial use and noise immunity
Free diagnostic and development tools including Visual Basic and Visual C++ ActiveX tools and multi-threaded drivers for Windows NT
Free applications support, including troubleshooting and board-level program development
PC-bus boards: technology in transition
By Sal Spada, Senior Analyst ARC Advisory Group, Dedham, MA
The move toward Windows NT in industrial automation continues. As it becomes increasingly robust in terms of performance and reliability, users select NT-based solutions to coordinate different manufacturing processes such as logic control, motion control, HMI (human machine interface) and enterprise-level integration.
Suppliers respond with tightly-integrated, NT-based solutions through Microsoft's DCOM (Distributed Component Object Model) technologies. While Microsoft provides the base technology platform, it relies on third-party partners to develop applications specific to manufacturing. For example, new technologies from Venturcom, Nematron and Radysis offer real-time, multitasking, and determinism that have been key to advancing widespread adoption of PC control.
Motion control is at the forefront of technologies being integrated into PC-based open-architecture systems. PC-based control, in conjunction with the proliferation of industrial device and motion-control networks, changes the way users purchase these components today. Experienced users, OEMs, and SoftLogic suppliers leverage PC-based technology by integrating board-level motion controllers with off-the-shelf industrial software. PC-bus motion-control boards are widely available, and are used in a wide range of applications that include computer numerical controls, robotics, material handling, and packaging.
These boards also have extremely advanced features. Multi-axis coordination, circular interpolation, electronic gearing, and S-curve acceleration, for example, are now standard. As a result, there is performance parity in board-level motion-control, while the average selling price of the boards continues to spiral downward. Lower prices enable many suppliers and integrators to achieve system costs that are well below the hurdles for many new projects.
SoftLogic suppliers provide the integration resources between board-level motion-control suppliers and the user. Seamless integration of SoftLogic and PC-bus motion cards challenge proprietary solutions by providing a single configuration, commissioning, and programming environment in conjunction with the benefit of easily accessing process data.
Motion cards used in these PC-based systems today function only as an interim solution. Automation solutions move toward software-based solutions today, where motion control, logic control, and HMI will be delivered as a shrink-wrapped solution. One could speculate that the Intel and Analog Devices announcement to jointly develop a DSP core architecture will result in this technology being directly integrated on a Pentium processor. Consequently, board-level motion control may experience a rapid evolution toward software-only solutions that will surpass the performance of today's solutions.
This isn't to say that design engineers today should wait until something better comes along. Today's cards are extremely good technologies with advanced features and are a proven solution. What engineers should think about, however, is the investment in software they'll need to make and how future technologies will be integrated into existing designs.
|Clearly, PC-bus boards are coming on strong, mostly at the expense of standalone controllers and intelligent drives. But the announcement by Intel and Analog Devices to jointly develop a DSP core could accelerate the market for PC soft motion beyond current predictions.|