Method for measuring total force in opposition to a moving vehicle
An apparatus is disclosed comprising a suite of sensors for measuring instant static and dynamic pressure and the speed and acceleration of a vehicle, such as a bicycle. A microprocessor receives data from the sensors and calculates power expended by the rider or other power source by finding the total of all forces impinging upon the vehicle and rider, thereafter multiplying by the speed of the ground vehicle. In some embodiments accuracy is improved by calibration techniques, user input of data, or temperature compensation of certain factors. Other data, such as wind speed, distance traveled, altitude, or surface grade may be presented to the user. In one embodiment data is stored for later analysis.
1. A method of calculating the total force impinging upon a vehicle, the method comprising the steps of:
calculating an aerodynamic force upon the vehicle;
calculating a gravity force upon the vehicle;
calculating a forward acceleration force due to movement of the vehicle;
and calculating a summation of said calculated forces plus a previously determined frictional force constant.
2. The method of claim 1 , wherein calculating the aerodynamic force upon the vehicle comprises the step of multiplying the dynamic pressure impinging upon the vehicle by a previously determined aerodynamic factor.
3. The method of claim 2 , wherein the previously determined aerodynamic factor is found by a coast down calibration procedure.
4. The method of claim 3 , wherein the coast down calibration procedure comprises the steps of:
(a.) accelerating the vehicle to a predetermined minimum speed;
(b.) removing all power applied to the vehicle;
(c.) recording sensor readings, including dynamic pressure;
(d.) comparing the vehicle speed to a predetermined minimum speed;
(e.) repeating step 11 ( c .) until said vehicle speed is less than the predetermined minimum speed; and
(f.) calculating the aerodynamic factor by curve fitting the recorded sensor readings.
5. The method of claim 1 , wherein the previously determined frictional force constant is found by a coast down calibration procedure.
6. The method of claim 5 , wherein the coast down calibration procedure comprises the steps of:
(a.) accelerating the vehicle to a predetermined minimum speed;
(b.) removing all power applied to the vehicle;
(c.) recording sensor readings, including dynamic pressure;
(d.) comparing the vehicle speed to a predetermined minimum speed;
(e.) repeating step 13 ( c .) until said vehicle speed is less than the predetermined minimum speed; and
(f.) calculating the frictional force constant factor by curve fitting the recorded sensor readings.
7. A method of calculating the power required in opposition to the total force impinging upon a vehicle, the method comprising the steps of:
calculating an aerodynamic force upon the vehicle;
calculating a gravity force upon the vehicle;
calculating a forward acceleration force due to movement of the vehicle;
and calculating a summation of said calculated forces plus a previously determined frictional force constant; and
multiplying said summation of calculated forces by the ground speed of said vehicle.