Rolling Road Calibration Fixture

This project was conceptualized after the need for an absolute method for calibration was identified for the force measuring hub restraint system. Prior to this, a vehicle of known drag was used to approximate the accuracy of the Rolling Road's force measurement system. The system is comprised of three instrumented vehicle restraint towers, which make use of 1-D load cells and encoders to determine the force vector acting through the tower. The force vectors from each of the three towers is then resolved into side force and drag force.

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This Calibration Fixture was designed in conjunction with two loading systems, side force and drag force, to apply a known amount of traction in each axis. This allows for a single axis loading and combined loading for calibration. Each loading system applies a force through an electric linear actuator, which has a single 1-D load cell for comparing applied load to resolved force. The loading systems applied load through a thin wire which acts through the centroid of the Calibration Fixture. Attention was given to each system's rigidity. This is to protect against unwanted deflections of the Calibration Fixture and therefore maintain kinematic relationships between the fixture and the force measuring hub restraint system.

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Each of the three system designs, the Calibration Fixture, Side Load Beam and Rear Load Beam, are construction from structural steel and 304SS mounting plates. The systems were welded and powdered coated prior to final machining operations, revealing the 304SS mounting surfaces. All mounting surfaces have dowel pins accurately located on their face, allowing for the future expansion of calibration and testing capabilities. The 304SS mounting surfaces ensure longevity of the calibration system, seeing as rust is a constant battle in our climate.