ROLLOVER PREVENTION BY MAXIMUM LATERAL FORCE BASED ON THE DETECTION OF THREE-DIMENSIONAL CENTER OF GRAVITY

Abstract

The center of gravity (COG) height is an important factor affecting rollover. Earlier studies by the authors assessed the theory of Detection of Three-Dimensional Center of Gravity (D3DCG), which provides an innovative and accurate method for COG height detection. This report describes development of D3DCG, which can be used to prevent rollover accidents by calculating the maximum height of COG and the maximum lateral force that can exist without causing rollover.
 For a fixed total weight of a vehicle, the COG height has an upper limit. Based on the law of energy conservation, if the COG height is lower than that upper limit, then the vehicle has potential energy against rollover. When the vehicle is running, road disturbances make its body shake. Some potential energy transfers to the spring energy to provide a restorative force and to make the COG return to its original position. Therefore, when the COG height reaches its maximum value, the potential energy disappears, causing rollover. The highest COG can be expressed according to the principle of the balance of rotational torque. To verify this theory, a COG adjustable experiment is designed with a table-top D3DCG device and a tower object. The total object weight does not change, but its COG height increases until the object cannot maintain stability on the device anymore. Comparison of the real COG and the highest COG confirmed that only when the COG is lower than the highest COG, the object will not roll over.
 If a lateral force is acting on a moving object such as a vehicle, then the object will tilt. At the same time, the restoring moment will resist the rolling moment. According to the theory of D3DCG, the lateral force has relation with the rolling angle. When the vehicle starts to roll over, based on the physical structure of moving vehicle, the critical lateral force can be represented by the rolling angle. Therefore, by eliminating the rolling angle as an unknown variable, the maximum lateral force can be expressed by two known variables: the actual COG height and the maximum height of COG. To verify this theory, a remotely controlled truck is made to rotate in a random rotation radius. Then its speed increases gradually until it rolls over. The real-time lateral force is recorded and compared with the calculated maximum lateral force. Results indicate that rollover occurs when the real-time lateral force reaches the maximum lateral force.
 This study examines a novel method of rollover prevention without knowing either the total weight, the vehicle speed or turning radius. The accuracy of this theory was well confirmed by comparing the real-time lateral force and the calculated maximum lateral force based on D3DCG.