Motion control advancements drive flexibility, performance

Motion control is one of the fastest growing global automation technologies. With a compound annual growth rate of 6% expected in North America through 2010, motion control in the plant is becoming commonplace. Leading the way are vendors who now offer a wider variety of options that rely increasingly on electronic controllers to perform the intricate coordination of multiple axes of a machine.

By taking advantage of new motion control technologies, plant engineers are reaping a number of rewards including decreased downtime, gains in operational flexibility and enhanced productivity and performance. However, those who ignore new motion control options run the risk of falling behind in increasingly competitive international markets. They also may miss the experience needed to support new equipment with the latest motion control technology when it arrives on the plant floor.

Motion control in the plant

To understand the latest in motion control advances, it is important to first review a few motion control basics. Motion control is an industry term used to describe a range of applications that involve movement with varying degrees of precision. Motion control options include:

• Mechanics (different motor connection possibilities)

• A motor to the drive mechanics

• A drive to control the motor and movement

• A control to coordinate motion control functionality, such as positioning, gearbox, camming and interpolation as well as automation of the machine.

• Motion control functions include:

  • Single axis motion that involves controlling one rotational axis. Simple speed control is an example of a single axis function

  • Multi-axis control involves control of multiple rotational axes, each of which could be converted into linear motion. Some applications require the control of multiple axes, with each axis operating independently. Others require varying degrees of coordination for multiple axes, ranging from synchronizing the start of motion control for multiple axes to the highly coordinated multiple-axes control required for machine tool applications.

  • Many motion control applications require only that an object be moved from one place to another with limited concern for acceleration, deceleration or speed of motion. On the opposite extreme are machine tool and production machine applications that require the precise coordination of all aspects of motion, including a high degree of coordination for multiple, simultaneous movements.

    Machine tools are designed to perform a series of specific tasks including milling, drilling, grinding or turning that require a high degree of coordination over multiple axes. An example of a machine tool application is the in-and-out movement of a cutting tool on a lathe that must be simultaneously coordinated with the side-to-side movement of that tool. In more complex machine tool applications, many more axes of motion may need to be controlled in a coordinated fashion.

    The range of production machine motion applications is very specialized. Functions that motion control drives and their associated motors must be capable of include:

    • Zero-speed holding torque

    • Quick start/stop cycles

    • High accelerating torque

    • Repeatable velocity and torque profiles

    • Synchronization

    • Positioning capabilities

    • Precise speed control.

    • Advancements in motion control technology

      Plant engineers should be aware of five trends in motion control. Each trend works with the others to provide the greatest value to companies looking to reduce costs and increase productivity. The trends — mechatronics, industrial Ethernet, safety integrated into the motion control process, sophisticated programming languages and new hardware platforms — are time-proven technologies that are now available to manufacturers.

      Mechatronics

      Mechatronics is the synergistic combination of mechanical, electrical and software engineering that provides simpler, more reliable, more economical and more versatile motion control systems.

      With the merging of electronics and mechanics, there is more to consider as machines are designed. It is not always as simple as removing a mechanical line shaft and replacing it with a motor drive and motion controller. One must consider other aspects of the machine design. For example, one of the reasons to remove the line shaft is to increase throughput because of speed limitations from the mechanics. When these changes are made, one must also revisit the specifications of the remaining motor(s) and associated mechanical components (couplings) to ensure that they can handle the modifications properly.

      To get the most of a motion control system that combines mechanical, electrical and software packages into one solution, look for a vendor that offers comprehensive support. By working with a trusted partner, plant engineers can implement new machine concepts or improve an existing design by modeling and simulating mechanics and controls, tune and optimize the controllers and investigate the weak points or failures.

      Involve your vendor’s mechatronics support team during the design phase, where it is necessary to simulate mechanics and controls working together as well as anticipate limitations in dynamics and accuracy and estimate achievable performance.

      Industrial Ethernet

      Industrial Ethernet used for motion control applications provides a uniform network structure that reduces the number of interfaces, as well as enables simple, plant-wide engineering. Compared to traditional wiring, industrial Ethernet is a big advantage when deterministic procedures and speed are important. Industrial Ethernet provides real-time operation with simultaneous IT communications along one cable.

      Capable of TCP/IP engineering, today’s latest Ethernet technologies offer remote support and diagnostics and use the advantages of IT technology in the production environment.

      Safety integrated into the MC system

      Manufacturing plants throughout the U.S. and the world are taking advantage of new machine guarding technologies endorsed by international safety standards. From the most sophisticated motion control operation to the simplest relay-based system, end users now have economical and effective choices to enhance machine safety.

      Combining the functionality of a control system and safety operation integrated into motion control-drives allows manufacturers to greatly reduce life cycle costs on a machine. The integrated safety system allows all motion control data to flow to the operator for fast and easy troubleshooting. This approach simplifies machine control and safety system coordination — from design to installation to troubleshooting.

      Design and implementation are simplified by using the same programming environment for control and safety circuits. Wiring is simplified by using safety networks to monitor and/or control each device on the safety circuit. Troubleshooting is often cut by 60% to 80% because each networked device communicates via the same HMI. These advantages significantly reduce downtime and the costs associated with failures.

      Programming languages

      Any type of motion control requires some sort of programming method. The three most popular methods are:

      • Ladder — Primary language used in PLCs. Well known by plant engineers and electricians. Motion commands can be implemented using industry standard functions (IEC 61131-3 — PLCopen)

      • Graphic — Offers users a simple, visual way to design sequential motion control programs. They typically use a flow-chart-like format. Graphic languages are non-standard — each vendor develops their own version

      • Text — High-level programming languages like those used by computer programmers. Supports the development of high-level arithmetic functions and complex logic flows in a structured format.

      • Each one offers benefits to the user. Some vendors require only one while others allow the use of all three within the same programming to draw the strengths of each one.

        Hardware platforms

        Today’s motion controllers are available in many different varieties — ranging from controller, PC and drive-based technologies. Most vendors offer one platform to build their controllers around. However, some vendors offer a single motion control environment capable of residing on any of the three platforms.

        The benefit of this is that whichever solution is chosen for a machine, the same programming environment and structure are used. As a result, the software tools to troubleshoot remain the same, regardless of the hardware or if the machines came from multiple OEMS with different hardware platforms.

        Author Information

        Michael Perlman is the business development manager for Siemens Energy & Automation’s Production Machines products group in Norcross, GA. Perlman has more than 20 years of experience in plant and corporate automation engineering at a number of Fortune 100 manufacturers. He received a Bachelor’s in Electrical Engineering from the Georgia Institute of Technology and an MBA from SUNY Buffalo.

        The Bottom Line…

        Motion control is one of the fastest growing automation technologies.

        Plant engineers who recognize and prepare for the rapid growth of motion control automation establish themselves as industry leaders and provide valuable insight for their companies.

        Machine tool and production machine applications require the precise coordination of motion control.

        Mechatronics, industrial Ethernet and safety integrated into the motion control process, sophisticated programming languages and new hardware platforms combine to make a flexible motion control system.

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