The ADL Force 5 configured for knee testing

DescriptionThe AMTI Force 5 is a versatile simulator that

can be configured for a variety of single and multi-axis tests, such as joint simulation, product testing, materials evaluation, and cadaver-

based studies. It features a single testing station, which is typically configured for hip, knee, or spine simu-lation.

The Force 5 can replicate the load-ing and full range of multi-axis motion associated with ac-tivities of daily living

(ADLs), like getting out of a bathtub, walking up or down stairs, squatting to pick something up, and running. Up to twelve individual physiologi-cal motions can be sequenced together to define a particular ADL, providing a true-to-life system for evaluating the materials and component designs of prosthetic implants.

The AMTI Force 5 simulator provides un-paralleled test accuracy through its Virtual Soft Tissue (VST) control, which couples force control with a software model that ac-counts for the constraining influence of the tissue structure surrounding the knee. The VST model provides an accurate representa-tion of soft tissue behavior, including non-linear and asymmetric force displacement characteristics.

The Force 5 simulator also provides a breakthrough in ease of use and accuracy through Adaptive Control Technology (ACT). Tuning time for force control simulators has traditionally been a major burden, often tak-ing days of tweaking by an expert to get a single set of prosthetic specimens ready for testing. AMTI’s ACT control system is en-abled with a single click and tunes the machine’s performance within about 30 cycles to levels of accuracy not ob-tainable with manual tuning.

The combination of VST and ACT

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control technologies allow for unprece-dented simulator tracking performance in both force control and displacement con-trol modes of operation. In most scenarios, the RMS error is less than 5 percent.

The machine also provides a microsepa-ration feature that simulates laxity in the constraining tissue of the hip during the swing phase of gait. The amount of distrac-tion is easily adjusted and is measured by vertical position sensors.

Four servo-hydraulic actuators drive the Force 5’s base motions, and an optional abduction head adds a fifth controlled de-gree of freedom (through an electric mo-tor) to facilitate hip and spine simulation. The test station is oriented in the physi-ologically correct position with the contact areas immersed in a sealed, temperature-controlled fluid bath. A low-noise hydraulic power supply is integrated into the base of the machine for convenient, standalone in-stallation.

The simulator can be operated in both force and displacement control modes, and a six-component load cell inside the test station allows for continuous or periodic measurement of the forces and moments of the x, y, and z axes. It comes complete with an adjustable load frame for single-axis tests.

The AMTI Force 5 simulator includes a complete data acquisition and control sys-tem, which utilizes an internal digital signal processor (DSP) to perform time-critical tasks. The DSP provides up to eight chan-nels of waveform generation, implements eight channels of PID (proportional, inte-gral, and derivative) control to drive the machine’s actuators, and manages data ac-quisition by multiplexing between 18 chan-nels of analog signals and measurements. The DSP assembles the data and transfers it through an Ethernet cable to the super-visory PC, which uses AMTI’s NetControl software to provide a complete operating interface for the machine.

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Possesses the full range of motion needed to replicate hip, knee, and spine movement during ac-• tivities of daily living (ADLs)

Virtual Soft Tissue control – software model that accurately incorporates the influence of the soft • tissue surrounding the knee

Adaptive Control Technology – breakthrough software that uses a feedback loop to automatically • tune the machine’s performance to new levels of accuracy

Can be operated by either force or displacement control•

Provides adjustable microseparation of the joint during the swing phase of gait •

Integrated, six-component load cell for measuring the forces and moments of Fx, Fy, Fz, Mx, My, • and Mz.

NetControl software provides a complete operating interface through an Ethernet cable-linked • computer.

Capable of testing to ISO and ASTM standards for hip, knee and spine implants, including ISO-• 14242-1, ASTM-WK451, ASTM-F1612-95, ISO/DIS-7206-4, ISO-14243-1, ISO-14243-3, ASTM-F1715-00, ASTM-F1800-04, ASTM-F1223-05, ASTM-F2423-05, ISO/DIS-12189, ISO/DIS-18192-1, and ASTM-F1717-04.

Temperature-controlled fluid reservoir and peristaltic pump for optional lubricated testing •

High-load actuators have hydrostatic bearings, which glide on a film of oil to avoid the wear associ-• ated with metal-on-metal contact.

All motions are servo-hydraulically generated with long-life, laminar seal actuators ( >10• 8 cycles).

The machine has a variable operating speed up to 2 Hz, allowing for the completion of up to • 172,000 cycles per 24-hour period.

Feature highlights

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