Add an axis to a medical sample delivery machine with minimal development time and cost

Application Challenge

A four axis medical sample delivery machine has a major specification change and now needs a fifth axis to control an end effector. The new axis goes through a fixed profile sequence indexed by 3 digital signals and an analog signal to control the profile as it approaches the target. There is no time to redesign the existing four axis control board. How do you quickly add a single axis controller that is flexible, inexpensive, and can be programmed by your existing software team?

Application Considerations

Figure 1: Medical Sample Delivery Machine with End Effector

Motion Control Solution

In this application, an ION/CME Digital Drive from PMD is used to control the end effector. This version of the ION family allows the user to download a user program into the ION, giving it the ability to operate fully standalone and implement the profile requirements and overall axis behavior needed in this application.

Because it is programmed in C, it is written in the same language as the microprocessor that controls the main four-axis motion control card, thereby eliminating the need to learn PLC type languages or vendor-specific motion languages.

As Figure 1 shows, the ION/CME acts as a complete standalone controller, inputting the 3 digital profile control signals as well as the sample distance reading contained in the analog signal. The code loaded into the ION uses high level library routines to set up and make on-the-fly changes to the profile moves, as well as to access the external digital and analog control signals. The resolution of the analog signal input is 16 bits.

Programming The Solution

The ION/CME's serial port is programmed to receive one of four commands from the four axis control card; Initialize, SamplePickup, SampleDropoff, and Abort. The ION/CME code processes each command and sends back an 'ActionComplete' response, or a 'ActionError' command.

Using PMD's C-Motion Development Environment, the code is prototyped and executed from a PC. This special 'code emulation mode' of the ION/CME allows software to be developed and executed from a PC even while controlling the actual motor axis and reading the actual digital and analog signals. Once development is complete, the same code is recompiled without source code changes and downloaded to the ION/CME for execution from within the unit.

Going Further

The ION/CME also provides an Ethernet port, which for this application could be used for easy local access by a field technician with a laptop, or remotely via the Internet (if the TCP/IP gateway has been set up that way) to check motion axis performance.

ION Digital Drives provide high performance motion control supporting multiple motor types including DC brush, brushless DC, step, and microstepping motors, and are based on PMD’s Magellan® Motion Processor , which provides user-selectable profile modes including S-curve, trapezoidal, velocity contouring, and electronic gearing.

Click to learn more about the PMD ION/CME Digital Drive.

Contact our customer support team at +1 781 674 9860 for more information including details on Developer’s Kits and application support. We would like to assist you in improving your motion system.