Trunk Bending Apparatus

Trunk stiffness and stability can be related to the posture and alignment of the human body. This project continues on the evolution of the Twister, a Trunk Stiffness Bending Device, that is intended to measure and acquire data of axial and torsional stiffness in core muscles. Then, postural performance can be linked to measured torso stiffness to examine muscle reaction patterns with the consideration of age, height, weight, and other factors.

Background
In the 1980's, Dr. Victor Gurfinkel, medical researcher at Oregon Health & Science University, developed the Twister to measure torsional muscle tone as well as muscular responses as the apparatus twisted the subject. The body sections considered by the Twister are the neck, trunk, and waist. Then, Dr. Gurfinkel devoted the apparatus to Dr. Rajal Cohen at University of Idaho, Psychology & Communication Studies Department, upon his retirement.

The developers of the Twister seek to study the psychological mechanism caused by the change in length of muscles crossing the selected region as a result of the device twisting that region. The resulting resistive torque is determined to calibrate the tonic control of all muscles subjected to changes in length. Based on peek-to-peek magnitude, phase of resistive torque, and tonic electromyogram modulation, the results being acquired show magnitude and dynamic control of muscle activity. Moreover, Fay Horak, another developer of the Twister at Oregon Health & Science University, believes that the Twister will help answering how the brain control normal postural tone, and how abnormal tone can be improved with treatment [].

Problem Definition
The previous team assembled and modified the structure to be relevant for the trunk bending experiments. They created an interface software to collect data, upgraded the hardware, and built harnesses. The objective is to bring the machine. into an operational state by using higher quality parts, completing circuitry, making the machine more user-friendly, adding safety features, and testing and collecting data from the final product

Initial Project State & Goals
Proceeding the project from the point reached by the previous team:
 * New string potentiometers are needed to withstand the weight applied and be durable. As new potentiometers are going to be used, the circuitry to the power supply and computer needs to be set up differently and the software interface created last year needs to be reprogrammed.
 * Strain gauges need to be programmed through the torque sensor.
 * New timing belt and pulleys are to be replaced for the bottom potentiometer.
 * The wiring of power supply seems to be done incorrectly therefore, the power supply has to be rewired correctly to the computer and all sensors.
 * The current neck bar has only one universal joint and as a result, the subjects neck has to bend along with the movement of the neck bar. To allow movement while the subject's neck is still perpendicular to the ground, two universal joints are to be installed so that one cancels the bending angle of the other.
 * Torque sensors need to be reconnected correctly to the power supply then, the its sensor has to be reprogrammed to the software interface created last year.
 * The current attachment bar system is not practical and can hardly be placed accurately. Therefore, a roller system is going to be added to the lateral bars so that the bars remain horizontal and can be slid up and down easily.
 * The DC motor has to be connected to the circuit and programmed with the software interface.
 * An emergency stop is to be added to the system for safety.
 * The current system does not have a physical safety stop when the platform rotates. Therefore, a physical stop is to be added to the system to have the platform stops at a certain degree while still achieving maximum rotation required.