Stress and load variation detector

A method for detecting variation in load in a load transmitting member which experiences a series of load producing events, said method comprising the steps of:

• obtaining a first signal related to, but not directly correlated with, stress in the member produced by a first at least one load producing event;
• obtaining a second signal related to, but not directly correlated with, stress in the member produced by a second at least one load producing event;
• and
• comparing said first signal to said second signal to detect the variation in load between different events, wherein
• the first signal is a deviation value which is representative of, and may be an approximation to, a statistical measure of variation such as a moving standard deviation of first subsignals, wherein such first subsignals are produced by load minima;
• the second signal is a deviation value which is representative of, and may be an approximation to, a statistical measure of variation such as a moving standard deviation of second subsignals, wherein such second subsignals are produced by load maxima;
• and wherein
• the signals and subsignals may occur in any temporal order.

A method for detecting load variation in a load transmitting member which experiences load variation, the method comprising the steps of:

• obtaining a first set of signals related to stress in the load transmitting member during a first time period;
• determining a first at least one value from said first set of signals;
• obtaining a second signal related to stress in the load transmitting member during a second time period wherein said second time period may comprise a portion of the first time period;
• computing a second at least one value, at least in part from the second signal;
• wherein said values are computed without directly computing the load;
• comparing the second at least one value to the first at least one value wherein said step of comparing may comprise, at least in part, the step of calculating a ratio of the second at least one value and the first at least one value;
• and
• thereby detecting load variation in the load transmitting member.

A method for detecting load variation in a load transmitting member which experiences load variation, said method comprising the steps of:

• obtaining a first set of signals related to the stress in the load transmitting member during a first time period;
• obtaining a second signal related to the stress in the load transmitting member during a second time period;
• calculating an expected value of the second signal from the first set of signals;
• calculating a standard deviation value which is representative of, and may be an approximation to, a moving standard deviation;
• dividing the difference between the expected value of the second signal and the second signal by the standard deviation value to obtain a ratio;
• and
• comparing the ratio to a threshold to detect load variation in the load transmitting member.