Simplified Motion Control

AutomationDirect, Cumming, GA

Figure 1. Modern servo drives (amplifiers) such as the AutomationDirect SureServo2 shown here, are now available with easy-to-use integrated motion controllers, empowering users to create comprehensive motion control designs, without the need for traditional decentralized architectures and complexity. (Image: AutomationDirect)

Servo motion technology is known for its precision, high torque, and speed capabilities, yet traditionally it has often been deemed too costly for smaller or budget-sensitive applications. Recent electronics advancements in micro-PLCs with integrated motion control, and drives with an on-board controller, have significantly reduced the cost and complexity of high-performance servo motor motion control, making it feasible to implement sophisticated servo systems in a wider array of applications.

Servo motors are integral to numerous machinery and equipment operations, such as conveyor systems, and multi-motor setups for indexing, gripping, or executing various physical tasks. Their high performance with respect to torque and speed, coupled with precise closed-loop control, has made them a preferred solution for complex motion requirements. However, the high cost and complexity of implementing servo systems traditionally required multiple components: brushless servo motors with encoders, servo amplifiers or drives, standalone motion controllers, high-performance communication fieldbuses, and programmable logic controllers (PLCs) for additional sensor integration.

Recent innovations have led to more consolidated and economical solutions. Modern servo drives with integrated motion control capabilities (Figure 1), and advanced PLCs (even micro-PLCs) equipped with motion instructions, now offer streamlined and cost-effective alternatives to traditional systems. These new architectures reduce the need for multiple standalone components and complex wiring, while cutting costs substantially.

Motion control capabilities cover a range of functionalities, as explained below.

Basic motion control may be for a single servo motor, with the ability to join one or two additional axes for X-Y or X-Y-Z control. With fundamentals such as the ability to perform homing operations, velocity/position moves, and standard motion profiles, designers can address a wide range of application needs. A micro-PLC with hardwired I/O connections to servo drives is a capable and economical way to create these solutions.

Figure 2. With a built-in motion controller and intuitive configuration software, the AutomationDirect SureServo2 series servo drives support both basic, along with more enhanced motion applications, such as the rotary shear configuration represented here. (Image: AutomationDirect)

Enhanced motion control goes beyond basic applications in several ways. This can include internal indexing where pre-configured moves are stored in memory, and standardized modes for functionality such as gantry control, encoder following, flying shear operation, rotary indexing, and basic registration. Other requirements may include high-speed event-based logic, safe torque off (STO), and the availability of auto-tuning and an integrated diagnostic software oscilloscope (Figure 2).

At this level, most users would prefer to use digital Ethernet industrial communications protocols — such as Modbus TCP and EtherNet/IP — instead of hardwiring. For these types of applications, a servo drive with built-in controller and communication features is often the best solution.

Mid-tier motion control applications demand even greater functionality. This can include multi-axis control ranging up to 16 or more axes, exceptionally rapid response times, advanced electronic camming, sophisticated interpolation modes, and on-the-fly control mode changes. Native IEC 61158 Ethernet for Control Automation Technology (EtherCAT) communications provide the deterministic and time-synced performance essential for these applications. Motion-specialized PLCs or dedicated motion controllers are needed for these applications.

Servo motors driving equipment — directly or through gearboxes or other mechanisms — are a well-established motion control technology, albeit mostly reserved for higher-end applications in the past. But now, the capability of micro-PLCs with essential motion instructions, and combined servo drive/controllers, makes it possible for users to apply effective motion control for more applications than ever before, and at a favorable price/performance ratio.

This article was written by Chip McDaniel, who works in technical marketing and Joe Kimbrell, Product Manager for Motion Control Products, both at AutomationDirect (Cumming, GA). For more information, visit here .