Force
5 Simulator
The 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 simulation.
The Force 5 can replicate the loading and full range of
multi-axis motion associated with activities 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 physiological 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 unparalleled test
accuracy through its Virtual Soft Tissue (VST) control, which couples force
control with a software model that accounts for the constraining influence of
the tissue structure surrounding the knee. The VST model provides an accurate
representation of soft tissue behavior, including nonlinear 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
taking days of tweaking by an expert to get a single set of prosthetic
specimens ready for testing. AMTI’s ACT control system is enabled 
with
a single click and tunes the machine’s performance within about 30 cycles to
levels of accuracy not obtainable with manual tuning.
The combination of VST and ACT control technologies allow
for unprecedented simulator tracking performance in both force control and
displacement control modes of operation. In most scenarios, the RMS error is
less than 5 percent.
The machine also provides a microseparation feature that
simulates laxity in the constraining tissue of the hip during the swing phase
of gait. The amount of distraction is easily adjustable 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 degree of
freedom (through an electric motor) to facilitate hip and spine simulation. The
test station is oriented in the physiologically 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 installation.
The
simulator can be operated in both force and displacement control modes, and a
six-component load cell inside the test station allows for the 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 system, which utilizes an internal digital signal
processor (DSP) to perform time-critical tasks. The DSP provides up to eight
channels of waveform generation, implements eight channels of PID
(proportional, integral, and derivative) control to drive the machine’s
actuators, and manages data acquisition by multiplexing between 18 channels of
analog signals and measurements. The DSP assembles the data and transfers it
through an Ethernet cable to the supervisory PC, which uses AMTI’s NetControl
software to provide a complete operating interface for the machine.
Feature
highlights
·
Possesses the
full range of motion needed to replicate hip, knee, and spine movement during
activities of daily living (ADLs)
·
Virtual Soft
Tissue control – software model that accurately accounts for 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 microseperation 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 associated with metal-on-metal contact.
·
All motions are
servo-hydraulically generated with long-life, laminar seal actuators ( >108
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.