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Test System for Orthopedic Medical Devices Using LabVIEW

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Original Authors: Todd VanGilder, Genuen

Edited by Cyth Systems

Orthopedic Medical Device
Orthopedic Medical Device

The Challenge

Creating a flexible and scalable life cycle and functionality test system capable of performing tests on a wide range of medical products for design development and verification testing.

The Solution

Designing a high-channel-count, universal test-stand platform with a versatile software communications framework that allows additional hardware components to be easily added and controlled by the main operator interface.

Stryker Instruments is one of the world’s leading manufacturers of medical technology. It offers a diverse array of reconstructive, medical, surgical, and neurotechnology and spine products. As part of its research and development efforts, the company uses a series of test systems for life-cycle and durability testing during early product development. However, their existing platform was not architected to accommodate the company’s new goals, and the hardware system design had limited channel count that limited the bandwidth of the test department. Stryker realized it was time to replace these test systems with a next-generation testing platform for both the development and verification phases of new products. The company wanted to realize its new goal, increase testing efficiency, by maximizing software reconfiguration without the need for programming, enhanced test automation, and hardware expandability. The system needed to be easily adaptable to a wide range of products and test requirements.

Stryker Instruments “System 8” orthopedic surgical instruments and tools.
Stryker Instruments “System 8” orthopedic surgical instruments and tools.

Michael Trumm is a Software Sr. Staff Engineer at Stryker Instruments who developed their original generic test platforms using scripts with NI LabVIEW system design software and DAQ tools. As a result of NI’s continued advancements in both hardware and software, the flexibility of its tools, and the acceptance of these tools in the marketplace as the benchmark products for DAQ and test systems, Stryker made a long-term strategic decision to standardize on the NI platform. However, due to a need for additional engineering resources and the increased complexity of the proposed design , Stryker decided to consider a third-party systems integrator to assist it the development of a next generation generic test platform. Stryker chose NI Partner Genuen (formerly known as Wineman Technology) because of the company’s extensive experience creating state-of-the-art test systems, as well as its engineers’ in-depth familiarity with NI products.

Building a Universal Tester Platform for Life-Cycle and Durability Testing

NI Partner Genuen was contracted to design and build five “Totally Reconfigurable Universal System Tester” (TRUST) machines for Stryker Instruments Division’s Test Lab. Built with LabVIEW system design software and the NI CompactDAQ modular data acquisition platform, these Windows PC-based test stands provided general data acquisition of sensors as well as pneumatic and electromechanical control using scripts. Key features included:

  • 100 channels of analog and digital I/O, including thermocouple inputs, pneumatic actuators, and power relays

  • Sample rates from 1 to 60,000 samples per minute or more, depending on how many channels were selected

  • User-defined data recording with time stamp, using Technical Data Management Streaming (TDMS) file format or comma delimited text format

  • Automated characterization of measurement equipment

The previous system was designed to run off detailed step sequences called scripts written using customized forms in Microsoft Excel, but it could run only five scripts at a time. Genuen used object-oriented programming (OOP) in LabVIEW capable of executing an unlimited number of scripts as long as the hardware could handle it. During a preliminary benchmarking test, the TRUST box easily handled 100 simple scripts running in parallel. This parallelism has provided Stryker the option to run two units under test (UUTs) from a single TRUST box, each independently, to provide a 100 percent throughput increase. An important design paradigm for the TRUST platform was to ensure that software did not limit performance. This way, the hardware could always be upgraded with more RAM and processing power if more scripts were needed.

Designing a Software Framework for Enhanced Test Platform Integration

While Genuen was working on the preliminary design of originally contacted for creating the TRUST platform, Michael Trumm approached the company about a software architecture idea he had. The majority of Stryker Instrument’s test systems communicated with their tester hardware components using standard driver architectures, which was not a scalable design. Michael’s concept involved using a main software program to read scripts and dynamically send commands to secondary software applications that controlled the systems hardware functions via a standardized Ethernet protocol. By separating the user interface from the specific hardware control and data acquisition functions, additional hardware components could easily be integrated into the system later. This decoupling approach would provide a more distributed, modular, and flexible software framework that resulted in less time and effort to develop specific test solutions and would promote reuse of existing LabVIEW code. It is estimated that generating a standardized user-interface and allowing hardware control of the software to be developed around common communications architecture could reduce the software development time for future test systems by more than 50 percent. Genuen agreed, and the “Test Regulation Over Networks” framework was born.

Built on LabVIEW, the Test Regulation Over Networks framework consists of three parts:

  • The Main Control Program (MCP) is the primary user interface that handles scripts and generates data files

  • The Remote Access Manager (RAM) monitors the network traffic and coordinates communications between the MCP and IO Portal programs

  • The IO Portal translates the MCP’s commands via a set of hardware drivers to control any hardware component of the test system

The user interface and individual test equipment communicate over Ethernet; thus, to add any new hardware component, an IO Portal application is created to enable the equipment to talk over Ethernet even if it is not natively supported. For example, the MCP can request to read a certain channel or power cycle of the unit under test over Ethernet, and the IO Portal translates and executes that instruction to the NI CompactDAQ hardware or other appropriate device. Using this design model, the Test Regulation Over Networks framework was successfully implemented and deployed in the first TRUST box.

The Benefits of the TRUST Test System

With a high channel count and the ability to easily modify a test sequence using scripting, the TRUST platform is ideal for medical device design and development testing because it can adapt to the iterative changes associated with the typical product design process. TRUST is running more scripts and monitoring more channels than the previous system, provides more test feedback to the design engineers. Trust also can accomplish similar testing approximately 20 percent faster due to an enhanced script engine at a much higher data acquisition rate. Additionally, end users of the system appreciate the ability to define custom channel names versus generic channel numbers used by the previous system.

The Test Regulation Over Networks framework also provides a more elegant and stable software solution that is scalable for incorporating new hardware components in the future. This methodology has allowed Stryker to reduce test system expenditures by 50 percent while increasing system effectiveness with added functionality. Furthermore, the technicians and engineers that create the tests use the same environment for script creation, eliminating the need for additional training.

Original Authors:

Todd VanGilder, Genuen

Edited by Cyth Systems

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