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Motion Control Mode Switching “on the fly” is Easy and Powerful

by Matt Cole

Applied Motion Products has always prided itself in developing easy-to-use products, including both hardware and software. Programmable drives can turn what would otherwise be a basic stepper or servo drive into a very smart independent controller that will auto-execute a customized Q program upon power up and react to numerous input conditions, including digital inputs and motor position feedback. This type of technology has been around for years here at Applied Motion. But did you know that these same drives can also accept “streaming” commands that can completely change the motion control mode in an instant?

Applied Motion’s Streaming Command Language (SCL) is an ASCII-based, simple to use communication protocol that allows for mode switching to be done with a single command sent over a serial or Ethernet connection. This can be done from any kind of host device, such as a PLC, programmable HMI, PC running LabVIEW or Matlab, or even a custom-written app for a tablet or smart phone. Sending these SCL commands to our servo drives, stepper drives, and integrated stepper motors unlocks a plethora of possibilities. Look for a ‘Q’ in the part number for Q programming with Streaming Commands, or an ‘S’ in the part number to indicate Streaming Commands only without Q programming. Also, adapted to popular fieldbus protocols, such as EtherNet/IP, Modbus RTU and soon, Modbus TCP/IP, the Applied Motion SCL command set rises to meet the challenge of the most demanding centralized or de-centralized network application.

So, how can this on-the-fly mode switching be used, you might ask. Let’s say you need to position with a servo motor and then switch into torque mode to apply the precise torque necessary to complete a manufacturing process such as valve pressure control or clamp force control in a closed-loop system. Well, that’s as easy as sending a ‘CM1’ message, which is the Control Mode command with the parameter to switch to torque mode. To switch back, send ‘CM21’ for point-to-point positioning mode. Another powerful command for automated processes that require speed matching is ‘FE’ which tells the drive to Follow Encoder signals coming from another axis of motion. This is an especially powerful command that closely related to Step Pulse & Direction input and often used in labeling, packaging, and assembly applications. These are just a couple of examples illustrating the ease and power of mode switching. For more information on SCL and eSCL (Streaming Command Language over Ethernet), see our Host Command Reference manual and SCL Utility software page. Also, take a look at our Application Notes page for setup instructions and sample code that can be used in popular PLC and HMI brands.

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