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Add a 5th Axis to 4-axis Medical Sample Delivery System

~ Motion Control Expert

Are you struggling with how to add an end effector solution to your multi-axis motion control application? This use case explains how you can add an additional axis to a multi-axis 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 4-axis motion control board. How do you quickly add a single axis machine controller that is flexible, inexpensive, and can be programmed by your existing software team? Read on for more insight.

Application Considerations

Feature / Function


Motor Type

Brushless DC (36V, 4.5 Amps)

Control Signals

3 TTL digital inputs
1 +/- 10V analog input from rangefinder

Command/Status Communications

RS232 serial


Medical Sample Delivery Machine End Effector Solution Note Application Solution Diagram

Figure 1: Medical Sample Delivery Machine with End Effector


Motion Control Solution

In this application, an ION Digital Drive from Performance Motion Devices 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, implement the profile generation requirements, and perform the overall axis behavior required 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 Digital Drive (using the C-Motion software) 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 serial port is programmed to receive one of four commands from the four axis motion control board:

  • Initialize
  • SamplePickup
  • SampleDropoff
  • Abort

The ION code processes each command and sends back an 'ActionComplete' response, or a 'ActionError' command.

Using our C-Motion Development Software tools, the code is prototyped and executed from a PC. This special "code emulation mode" of the ION motion controller 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 digital drive for execution from within the unit.

Going Further

The ION 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 DrivesION Digital Drives provide high-performance motion control supporting multiple motor types, including DC Brush, Brushless DC, step, and microstepping motors, and are based on Performance Motion Devices Magellan® Motion Control ICs, which provide user-selectable profile modes, including S-curve, trapezoidal, velocity contouring, and electronic gearing. 

Want to learn more? Contact our customer support team today for more information, including details on Developer Kits and application support. We would like to assist you in improving your motion system.


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