In an effort to better understand the mechanics of head injury, two new measurement systems are developed. The rigid body kinematics transducer array, or RBKTA, is a derivative of an existing technology, the WSU 3-2-2-2 or nine accelerometer array. The RBKTA is designed to allow computation of the three dimensional kinematics of a rigid body undergoing impact. It consists of 24 linear accelerometers in a precise geometric array. The triaxial neutral density cranial accelerometer, or NDA, is a continuation of the currently developing neutral density technology. The NDA is a device designed to be implanted in cadaver brain and to be used to measure acceleration of a point in the brain tissue in three directions. Both systems are developed out of a need to improve upon existing measurement methods.

The RBKTA is designed to calculate angular acceleration of a rigid body using a linear regression scheme. The linear accelerations at the origin are found in a similar sense. Radially oriented accelerometers are used to calculate angular velocity. The NDA is a polyester resin shell containing three accelerometer dies. The shell is filled with polyurethane foam and coated with acrylic. The NDA has a volume of less than .2 ml and a density of 1.065 gm/ml. Both the RBKTA and the NDA use IC Sensors 8063-200 integrated accelerometer dies.

The RBKTA suffers no accelerometer positioning errors as each accelerometer’s sensitive axis is located directly in line with an axis of the fixture. The fixture itself is small enough to fit within the Hybrid Ill head, atop the 6 axis neck transducer, and is light enough to be fastened to a cadaver skull. The NDA is small enough that an array of the devices could be implanted in a single brain. It is anticipated that the RBKTA will be used to compare the motion of a point in space within the head that corresponds to the location of the NDA, to the output of the NDA which is to be implanted in the brain. It is in this fashion that the previously used 3-2-2-2 and the biaxial NDA were employed. Both the RBKTA and the triaxial NDA have yet to become fully functional, validated devices.

The following reviews some of the work of others in the areas of rigid body kinematics and cranial deformation measurement. The previous efforts, theory and background material that generated the RBKTA and triaxial NDA are also discussed. The design goals and fabrication concepts of each device are summarized and the final designs and considerations are presented for the RBKTA and the triaxial NDA. Final comments are made concerning the next stages to be approached, and the merits of the two designs.