Pressure Dummies

Measurement of the pressure distribution with load carriage systems

Different test methods are used to evaluate load-bearing systems. On the one hand, the simulators / test dummies in the laboratory are like "Beda" for determining the movement limitation and "Nick" for the study of the pressure distribution. On the other hand, there are also tools such as the trifliare pendulum for the determination of the center of gravity or a simulation model to determine the risk of injury, based on the measured values with the simulators.

Trifilar pendulum
The trifilar pendulum consists of a rotatably mounted plate attached to the ceiling with 3 ropes. Each rope contains a scale on which the weight can be read. In order to determine the center of gravity of a body, the test specimen is placed on the turntable in the desired position and shifted until all three scales display the same weight. The center of gravity is then in the center of the plate. In addition to the determination of the center of gravity, the moment of inertia about the center of gravity can also be determined.
https://sasp20.empa.ch/documents/56038/91259/TrifilarPendulum.jpg/fa21442e-6058-49d3-9be2-d67541f7f4f3?t=1480413121000
Trifilar pendulum
Movement limitations (Beda)
The test system for determining the movement limitation consists of a divided manikin, which can be moved over three degrees of freedom. The degrees of freedom are:
  • forward
  • sideward and
  • rotation
During the movement, the forces or torques in the three axes are measured. The greater the forces and moments, the bigger the restriction is in the direction of movement.
https://sasp20.empa.ch/documents/56038/91259/Beda.jpg/fad70772-b220-482c-9d72-40345ce9842b?t=1480413122000
Beda
Pressure distribution (Nick)

The most complex test system is "Nick" to determine the pressure distribution. The system consists of an instrumented dummy that simulates a walking movement in which it can move up and down.

In addition to the drive, several measuring systems are integrated: pressure sensors (Tekscan), relative movement (Polhemus), forces and torques (AMTI) as well as belt tension.

The pressure distribution is recorded with 6 Tekscan sensors. Each sensor has an active matrix area of ​​76.2 mm x 203.2 mm on the total of 96 single sensors.

To determine the relative movement we use the Polhemus Liberty system. It consists of a transmitter and up to 8 sensors which measure their position and orientation in the three-dimensional space.

To determine the forces and torques, 2 sensors are installed in the Manikin; So the total load and the load on the shoulder or upper body can be determined.

The detection of the belt tension is based on a sensor which registers the deformation of a cut tube piece. A strain gage was applied to the tube to detect the slightest deformation.

https://sasp20.empa.ch/documents/56038/91259/Nick.jpg/04734836-2c20-4b4f-a878-af1b8583dcca?t=1480413122000
Nick