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DJOTM Knee Cycle Tester
DJOTM Knee Cycle Tester
The Executive Summary can be found here: Executive Summary
The primary objective of this project is to design a Knee Cycle Tester (KCT) that accurately replicates the architecture and motion of the human leg. The mechanism design must not allow the soft braces to collapse into a mechanical joint. A typical fatigue test should run for the expected period of use for a typical bracing product which is about 1,000,000 to 1,500,000 cycles. A cycle is defined as one rotation of the knee joint, forward and back. While performing the fatigue test the KCT should operate at a typical human walking/jogging frequency of about 1-1.5Hz. In addition the KCT must allow for three primary ranges of motion to test; 0-45 degrees, 0-90 degrees and 0-135 degrees. The 0 degree position is defined as the leg fully straightened. While the fatigue test is being performed, the KCT should also monitor the performance of the brace through either a torque or force measurement and count cycles so that if a failure occurs the time of failure can be noted.Final Design:
The final design of the Knee Brace Cycle Tester features a slider crank actuation to achieve the proper knee rotation. In order to test the different ranges of motion a variable crank system allowing it to reach all the desired test ranges of motion. A force sensor measured the brace resistive force, while an Arduino microcontroller regulated the speed and cycles as well as recording the brace resistive force. The design is also modular, in that it can be applied to other joint structures if DJO requires. The cycle tester successfully detected a performance decrease in a soft knee brace while testing at 1Hz in the 0-90 test rotation.
The Knee Brace Cycle Tester
Background:
Background:
DJOTM Global, Inc. is a leading global provider of high-quality, orthopedic devices, with a broad range of products used for rehabilitation, pain management and physical therapy. DJO markets a wide variety of soft and hard joint bracing products. The soft braces use the structure of the knee and leg to provide tension in the brace and, hence, support the knee. However, some of the materials that the braces are composed of would fail sooner than DJO expected during use due to material fatigue. In order to avoid this problem in the future DJOTM Global has requested a cycle tester be designed and manufactured that will perform fatigue testing on both soft and rigid bracing devices.
DJOTM Global, Inc. is a leading global provider of high-quality, orthopedic devices, with a broad range of products used for rehabilitation, pain management and physical therapy. DJO markets a wide variety of soft and hard joint bracing products. The soft braces use the structure of the knee and leg to provide tension in the brace and, hence, support the knee. However, some of the materials that the braces are composed of would fail sooner than DJO expected during use due to material fatigue. In order to avoid this problem in the future DJOTM Global has requested a cycle tester be designed and manufactured that will perform fatigue testing on both soft and rigid bracing devices.
Objectives:
Objectives:
The Cycle Tester in Action 0-90 degrees
In order to properly support the braces a leg shaped covering was designed. This covering attaches directly to the links in the slider crank system as shown in the figure below. The covering was 3D printed and can be easily fabricated by DJO on site.
The Leg Covering
An encasing framework was assembled from t-slotted extruded aluminum in in order to both support the structure and to keep the moving components safely contained. All electronics are safely and conveniently located in an acrylic box in the center of the cycle tester.
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