Method for real-time mass estimation of a vehicle system

Abstract

A method for estimating the mass of a vehicle system includes a number of steps including a first step of providing a vehicle system having at least a powertrain and a vehicle control module. Three different mass estimates are assigned with the last mass estimate being the most accurate. The mass estimates are used in the vehicle control module calculations for vehicle control parameters in the event that the weight of the vehicle changes.

Claims

1. A method for estimating the mass of a vehicle system, the method comprising: providing a vehicle system having a vehicle control module and a powertrain having an ignition system; detecting if the ignition system is on; initializing an initial mass M.sub.0 representing a most recent estimated mass M.sub.est in a stored memory of the vehicle control module; detecting if the vehicle system is traveling in a straight line until the vehicle system is detected traveling in a straight line; estimating a first estimated mass M.sub.1; detecting an event in which a change in acceleration occurs, wherein the acceleration of the vehicle system changes from positive to negative or the acceleration of the vehicle system changes from negative to positive; recording a first and a second data points, wherein the first data point is when the velocity of the vehicle system is V.sub.x before the event in which a change in acceleration occurs and the second data point is when the velocity of the vehicle system is V.sub.x after the event in which a change in acceleration occurs; and using the first and second data points to calculate a second estimated mass M.sub.2.

2. The method for estimating the mass of a vehicle system of claim 1 further comprising setting a new estimated mass M.sub.est from the initial, first estimated and second estimated mass M.sub.0, M.sub.1, M.sub.2.

3. The method for estimating the mass of a vehicle system of claim 2 wherein setting a new estimated mass M.sub.est from the initial, first estimated and second estimated mass M.sub.0, M.sub.1, M.sub.2 further comprises setting a new estimated mass M.sub.est from the initial, first estimated and second estimated mass M.sub.0, M.sub.1, M.sub.2 wherein the new estimate mass M.sub.est=M.sub.2 if M.sub.2 has been calculated, the new estimated mass M.sub.est=M.sub.1 if M.sub.2 has not been calculated, and the new estimated mass M.sub.est=M.sub.0 if each of M.sub.1 and M.sub.2 have not been calculated.

4. The method for estimating the mass of a vehicle system of claim 2 further comprising communicating the new estimated mass M.sub.est to the vehicle control module.

5. The method for estimating the mass of a vehicle system of claim 1 wherein estimating a first estimated mass M.sub.1 further comprises estimating a second estimated mass M.sub.1 using the equation $M_1=\frac{F_d-K_b{P}_b-K_a{V}_x^2}{\left(a_x+g\right)}$ and wherein F.sub.d is a drive force, P.sub.b is a brake pressure, and K.sub.aV.sub.x.sup.2 is an aerodynamic force.

6. The method for estimating the mass of a vehicle system of claim 1 wherein using the first and second data points to calculate a third estimated mass M.sub.3 further comprises using the first and second data points to calculate a second estimated mass M.sub.2 using the equation $M_2=\frac{\left(F_{\mathrm{dB}}-F_{\mathrm{bB}}\right)-\left(F_{\mathrm{dA}}-F_{\mathrm{bA}}\right)}{\left(a_{\mathrm{xB}}-a_{\mathrm{xA}}\right)}$ and wherein F.sub.dA and F.sub.dB are drive forces, F.sub.bA and F.sub.bB are brake forces, and a.sub.xA and a.sub.xB are measured acceleration.

7. The method for estimating the mass of a vehicle system of claim 1 wherein using the first and second data points to calculate a third estimated mass M.sub.3 further comprises using the first and second data points to calculate a second estimated mass M.sub.2 using the equation $M_2=\frac{\left(F_{\mathrm{dB}}-F_{\mathrm{bB}}\right)-\left(F_{\mathrm{dA}}-F_{\mathrm{bA}}\right)}{\left(a_{\mathrm{xB}}-a_{\mathrm{xA}}\right)}$ and wherein F.sub.dA is the drive force at the first data point, F.sub.dB is the drive force a the second data point, F.sub.bA is the brake force at the first data point, F.sub.bB is the brake force at the second data points, and a.sub.xA and a.sub.xB are the measured acceleration at the first and second data points, respectively.

8. A method for estimating the mass of a vehicle system, the method comprising: providing a vehicle system having a vehicle control module and a powertrain having an ignition system detecting if the ignition of the vehicle system is on; initializing an initial mass M.sub.0 representing a most recent estimated mass M.sub.est in a stored memory of the vehicle control module; detecting if the vehicle system is traveling in a straight line until the vehicle system is detected to be traveling in a straight line; estimating a first estimated mass M.sub.2 using the equation $M_1=\frac{F_d-K_b{P}_b-K_a{V}_x^2}{\left(a_x+g\right)};$ detecting an event in which a change in acceleration occurs, wherein the acceleration of the vehicle system goes from positive to negative or the acceleration of the vehicle system goes from negative to positive; recording a first and a second data points, wherein the first data point is when the velocity of the vehicle system is V.sub.x before the event and the second data point is when the velocity of the vehicle system is V.sub.x after the event; estimating a second estimated mass M.sub.3 using the equation $M_2=\frac{\left(F_{\mathrm{dB}}-F_{\mathrm{bB}}\right)-\left(F_{\mathrm{dA}}-F_{\mathrm{bA}}\right)}{\left(a_{\mathrm{xB}}-a_{\mathrm{xA}}\right)};$ setting a new estimated mass M.sub.est from the initial, first estimated and second estimated mass M.sub.0, M.sub.1, M.sub.2, and communicating the new estimated mass M.sub.est to the vehicle control module.

9. The method for estimating the mass of a vehicle system of claim 8 wherein setting a new estimated mass M.sub.est from the initial, first estimated and second estimated mass M.sub.0, M.sub.1, M.sub.2 further comprises setting a new estimated mass M.sub.est from the initial, first estimated and second estimated mass M.sub.0, M.sub.1, M.sub.2 wherein the new estimate mass M.sub.est=M.sub.2 if M.sub.2 has been calculated, new estimate mass M.sub.est=M.sub.1 if M.sub.2 has not been calculated, and new estimate mass M.sub.est=M.sub.0 if each of M.sub.1 and M.sub.2 have not been calculated.

10. The method for estimating the mass of a vehicle system of claim 9 wherein estimating a first estimated mass M.sub.1 using the equation $M_1=\frac{F_d-K_b{P}_b-K_a{V}_x^2}{\left(a_x+g\right)}$ further comprises estimating a second estimated mass M.sub.2 using the equation $M_1=\frac{F_d-K_b{P}_b-K_a{V}_x^2}{\left(a_x+g\right)}$ and F.sub.d is a drive force, P.sub.b is a brake pressure, and K.sub.aV.sub.x.sup.2 is an aerodynamic force.

11. The method for estimating the mass of a vehicle system of claim 10 wherein estimating a third estimated mass M.sub.3 using the equation $M_2=\frac{\left(F_{\mathrm{dB}}-F_{\mathrm{bB}}\right)-\left(F_{\mathrm{dA}}-F_{\mathrm{bA}}\right)}{\left(a_{\mathrm{xB}}-a_{\mathrm{xA}}\right)}$ further comprises estimating a third estimated mass M.sub.3 using the equation $M_2=\frac{\left(F_{\mathrm{dB}}-F_{\mathrm{bB}}\right)-\left(F_{\mathrm{dA}}-F_{\mathrm{bA}}\right)}{\left(a_{\mathrm{xB}}-a_{\mathrm{xA}}\right)}$ and F.sub.dA and F.sub.dB are drive forces, F.sub.bA and F.sub.bB are brake forces, and a.sub.xA and a.sub.XB are acceleration.

12. The method for estimating the mass of a vehicle system of claim 11 wherein estimating a second estimated mass M.sub.3 using the equation $M_2=\frac{\left(F_{\mathrm{dB}}-F_{\mathrm{bB}}\right)-\left(F_{\mathrm{dA}}-F_{\mathrm{bA}}\right)}{\left(a_{\mathrm{xB}}-a_{\mathrm{xA}}\right)}$ further comprises estimating a third estimated mass M.sub.3 using the equation $M_2=\frac{\left(F_{\mathrm{dB}}-F_{\mathrm{bB}}\right)-\left(F_{\mathrm{dA}}-F_{\mathrm{bA}}\right)}{\left(a_{\mathrm{xB}}-a_{\mathrm{xA}}\right)}$ and wherein F.sub.dA is the drive force at the first data point, F.sub.dB is the drive force a the second data point, F.sub.bA is the brake force at the first data point, F.sub.bB is the brake force at the second data points, and a.sub.xA and a.sub.XB are the measured acceleration at the first and second data points respectively.

13. A vehicle system comprising: a vehicle body having a frontal area A having a constant K.sub.a; a powertrain disposed within the body of the vehicle system and having an ignition system, and wherein the powertrain selectively provides a drive force F.sub.d on the vehicle system; at least two wheels; a brake system disposed in the body and the at least two wheels, and wherein the brake system selectively provides a brake force F.sub.b on the vehicle system; a suspension system disposed between the at least two wheel and the body and powertrain, wherein the suspension supports the body and powertrain upon the at least two wheels; and a vehicle control module electronically connected to the vehicle system, the vehicle control module has control logic operable to control a plurality of dynamic driving parameters of the vehicle system, the control logic including: a first control logic for detecting if the ignition system is on and the powertrain is running; a second control logic initializes a variable M.sub.0 representing the most recent estimated mass M.sub.est in memory; a third control logic detects if the vehicle system is traveling in a straight line, and wherein if the vehicle system is not traveling in a straight line, the third control logic repeats until the vehicle system is traveling in a straight line; a fourth control logic estimates a first vehicle mass M.sub.1 using the equation
M.sub.1(a.sub.x+g)=F.sub.dK.sub.bP.sub.bK.sub.aV.sub.x.sup.2; a fifth control logic detects if the number of data points at the set velocity V.sub.x has exceeded 1, and wherein if the number of data points at the set velocity V.sub.x has not exceeded 1, the fifth control logic repeats until the number of data points at the set velocity V.sub.x has exceeded 1 and recording a first and a second data points, the first data point is recorded the at the first time the set velocity V.sub.x is reached, and the second data point is recorded at the second the set velocity V.sub.x is reached; and a sixth control logic estimates a second vehicle mass M.sub.2 using the equation
M.sub.2(a.sub.xBa.sub.xA)=(F.sub.dBF.sub.bB)(F.sub.dAF.sub.bA).

14. The vehicle system of claim 13 further comprising a seventh control logic sets a new estimated mass M.sub.est equal to one of the most recent estimated mass M.sub.0, the first vehicle mass M.sub.1, and the second vehicle mass M.sub.2 from each of the second control logic, the fourth control logic, and the sixth control logic each time the particular step is executed and the new mass estimate M.sub.est is calculated or initialized.

15. The vehicle system of claim 14 further comprising an eighth control logic that communicates the mass estimate M.sub.est of the seventh control logic to the vehicle control module.

16. The vehicle system of claim 15 further comprising a ninth control logic that upon an initial execution of the sixth control logic repeats the sixth control logic until the ignition of the vehicle system is turned off.

17. The vehicle system of claim 16 wherein the seventh control logic further comprises setting a new estimated mass M.sub.est equal to one of the most recent estimated mass M.sub.0, the first vehicle mass M.sub.1, and the second vehicle mass M.sub.2 wherein the new estimate mass M.sub.est=M.sub.2 if M.sub.2 has been calculated, the new estimate mass M.sub.est=M.sub.1 if M.sub.2 has not been calculated, and the new estimate mass M.sub.est=M.sub.0 if each of M.sub.1 and M.sub.2 have not been calculated.

18. The vehicle system of claim 17 wherein the sixth control logic of estimating the second vehicle mass M.sub.2 using the equation $M_2=\frac{\left(F_{\mathrm{dB}}-F_{\mathrm{bB}}\right)-\left(F_{\mathrm{dA}}-F_{\mathrm{bA}}\right)}{\left(a_{\mathrm{xB}}-a_{\mathrm{xA}}\right)},$ further comprises estimating the second vehicle mass M.sub.2 wherein F.sub.dA and F.sub.dB are the drive forces, F.sub.bA and F.sub.bB are the brake forces, and a.sub.xA and a.sub.xB are acceleration.

19. The vehicle system of claim 18 wherein the fourth control logic of estimating the first vehicle mass M.sub.1 using the equation $M_1=\frac{F_d-K_b{P}_b-K_a{V}_x^2}{\left(a_x+g\right)}$ further comprises estimating the first vehicle mass M.sub.1 wherein F.sub.d is a drive force, P.sub.b is a brake pressure, and K.sub.aV.sub.x.sup.2 is an aerodynamic force.

20. The vehicle system of claim 19 further comprising at least one of a passenger, a payload, and a trailer.

Description

DRAWINGS

(1) The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way;

(2) FIG. 1 is a schematic of a dynamic vehicle system according to the present disclosure;

(3) FIG. 2 is a graph detailing data collected during a dynamic event for a vehicle according to the present disclosure;

(4) FIG. 3 is a graph detailing data collected during a dynamic event for a vehicle according to the present disclosure;

(5) FIG. 4 is a graph comparing the accuracy of the mass estimation method of the present disclosure to the prior art mass estimation method, and

(6) FIG. 5 is a flowchart detailing the steps of a method for vehicle mass estimation according the present disclosure.

DETAILED DESCRIPTION

(7) The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses.

(8) With reference to FIG. 1, an exemplary schematic for a vehicle system, generally indicated by reference number 10, is depicted and will now be described. The vehicle system 10 in the present example is shown as a light duty pick-up truck having the capacity of transporting several occupants and several hundred pounds or kilograms in cargo in the truck bed. In one example of the present invention, a vehicle system 10 also includes a trailer (not shown) connected to the rear of the vehicle system 10 thus providing the capability of adding to the weight capacity of the vehicle system 10. In another example of the present invention, the vehicle system 10 primary purpose is for transporting passengers such as a school bus or a transit bus that is continuously picking up or dropping off passengers. Thus, the capability of the vehicle system to have up to several thousand pounds of additional weight adds to the complexity of operating the vehicle system when just a small amount of weight change can cause the vehicle system 10 to react differently to the same road conditions. Therefore, the importance of knowing the instantaneous mass M of the vehicle is increased. Estimating the mass M of the vehicle system 10 starts with the following equation:
F.sub.x=Ma.sub.x[1], or
M=F.sub.x/a.sub.x[2],
where F.sub.x is sum of the forces acting on the vehicle system and ax is the acceleration or gravity which also includes a road grade component.

(9) The vehicle system 10 includes a powertrain 12, a body 14, a suspension 16, wheels 18, a brake system 20, and a vehicle or powertrain control module 21. More particularly, the powertrain 12 provides torque to the wheels 18 through several components. In this example, the powertrain 18 includes an internal combustion engine 22, a transmission 24, a transfer case 26, a front and rear driveshafts 28, front and rear differentials (not shown), and front and rear axles (not shown). The engine 22 produces torque which is passed through the various gear ratios of the transmission 24 to the transfer case 26. The transfer case 26 selectively transfers torque to the front and rear differentials through the front and rear driveshafts 28. The differentials distribute the torque to the wheels 18. In another example, the powertrain 12 may produce torque through an electric motor or a combination of an electric motor and an internal combustion engine 22 without departing from the scope of the invention. The torque produced and distributed by the powertrain 12 applies a drive force F.sub.d on the vehicle system 10.

(10) The body 14 of the vehicle system 10 includes a passenger compartment 30, a payload bed 32, and has a frontal area A. The passenger compartment 30 and payload bed 32 are portions of the vehicle system 10 capable of carrying or offloading passengers and payloads 34. The frontal area A determines a major portion of an aerodynamic drag force F.sub.a, as defined in the following equation:

(11) $\begin{array}{cc}{F}_a=\frac{1}{2}{V}_x^2{C}_{d}A& \left[3\right]\end{array}$
where is air density, V.sub.x is vehicle system 10 velocity; C.sub.d is an aerodynamic drag coefficient. For the purposes of this invention, air density , and the aerodynamic drag coefficient C.sub.d will be combined to a constant X.sub.a to give the equation
F.sub.a=X.sub.aV.sub.x.sup.2A[4]
where the only variables are the velocity V.sub.x and the frontal area A of the vehicle system 10. However, in many calculations the frontal area A is considered constant even while adding to the frontal area of the vehicle system 10 in the form of a trailer. Thus, using the previous equation with the frontal area A as a constant and not including a measurement of the total frontal area A will be a source of error or inaccuracy. Therefore, for a given vehicle system 10 the equation for determining the aerodynamic force Fa is reduced to
F.sub.a=K.sub.aV.sub.x.sup.2[5]
where Ka is the constant including air density , the aerodynamic drag coefficient C.sub.d, and a constant frontal area A.

(12) The suspension 16 of the vehicle system 10 includes springs 36, shocks or dampers (not shown), and various other components making it possible to control the vehicle system 10 and carry passengers and payloads. The mass M of the vehicle system 10 includes sprung mass, unsprung mass, payload, and passengers. The sprung mass includes the mass of the vehicle system 10 that is supported by the springs 36 of the suspension 16. The unsprung mass includes the mass of the portion of the powertrain that is supported by the wheels 18 such as the front and rear differentials, axles, and a portion of the driveshafts 28.

(13) The brake system 20 of the vehicle system 10 provides the stopping power or brake force F.sub.b for slowing or causing the vehicle system 10 to decelerate. The brake force F.sub.b is found using the equation:
F.sub.b=K.sub.bP.sub.b[6],
where P.sub.b is the brake system pressure and K.sub.b is a constant.

(14) The wheels 18 of the vehicle system 10 include at least a hub 38 and a tire 40. The hub is fixed to the end of one of the axles of the powertrain 12. The tire 40 is mounted to the hub 38 and is the point of contact between the vehicle system 10 and the road surface. A road friction Fr component of the forces acting on the vehicle system 10 is due to the rolling resistance of the tires 40. Several factors affect rolling resistance including tire temperature, tire pressure, velocity, tire material and design, and tire slip. In general, a friction coefficient is used to calculate road friction Fr that represents the various factors. Thus, the equation for road friction is given as:
F.sub.r=M.sub.g[7],
where the friction coefficient is a constant and g is gravity.

(15) As a result, the total force F.sub.x acting on the vehicle system 10 is estimated using the following equations:
F.sub.x=F.sub.dF.sub.bF.sub.aF.sub.r[8], or
F.sub.x=F.sub.dK.sub.bP.sub.bK.sub.aV.sub.x.sup.2Mg[9] and
F.sub.x=Ma.sub.x[10].
Finding for the mass M of the vehicle system 10 results in the following equation:
M(a.sub.x+g)=F.sub.dK.sub.bP.sub.bK.sub.aV.sub.x.sup.2[11].

(16) However, a major shortfall with applying this equation directly to the estimation of the mass M of the vehicle system 10 is that the assumption of the terms K.sub.b, K.sub.a, and as being constant is not necessarily a good assumption. For example, the friction coefficient , as stated above, changes with tire pressure and temperature and with dynamic road conditions. The aerodynamic coefficient K.sub.a will change greatly with the addition of a trailer; especially if the trailer height or width creates a larger frontal area A. The brake coefficient K.sub.b can change as the brake hardware is worn or as the brake temperature changes. Furthermore, while the road grade term a.sub.x results from a sensor reading and not a constant, the road grade term a.sub.x may include an unknown pitch angle term brought on by deflection of the suspension 16.

(17) Turning now to FIGS. 2 and 3, a method of estimating the mass M of the vehicle system 10 is demonstrated using graphs. Each of the FIGS. 2 and 3 depict an event such as dynamic acceleration-to-deceleration event, acceleration-to-coasting event, or a deceleration-to-acceleration event. The top or first graph 50 of FIG. 2 shows the position of the throttle pedal 52 vs. time [s] 54, the position of the brake pedal 56 vs. time[s] 54, and the overall acceleration term a.sub.x[g] 58, shown on the y-axis 60, vs. time[s] 54 of the event. In particular, graph 50 depicts an acceleration-to-coasting event. Thus the event entails a throttle pedal position steadily increasing 62, then a lift-off the throttle pedal 64 without any depression of the brake pedal. During the acceleration portion 62, the acceleration term a.sub.x is between 0.01 g and 0.02 g. The coasting portion 64 results in acceleration of about 0.3 g to 0.05 g. The bottom or second graph 66 of FIG. 2 traces the actual velocity V.sub.a 68 in km/h (y-axis) 70 vs. time[s] 54 over the course of the event. The method either uses a preset velocity constant V.sub.k or selects a velocity V.sub.x using a routine. In whichever manner, a velocity V.sub.x is chosen to intersect with the actual velocity V.sub.a and two data points A and B are recorded.

(18) Applying the above equation to data point A and data point B results in the following equations:
M(a.sub.xA+g)=F.sub.dAK.sub.bP.sub.bAK.sub.aV.sub.xA.sup.2[12]
M(a.sub.xB+g)=F.sub.dBK.sub.bP.sub.bBK.sub.aV.sub.xB.sup.2[13].
Since V.sub.xA.sup.2=V.sub.xB.sup.2 due to the data points A and B taken at a constant Velocity Vx, the equations reduce to:
M(a.sub.xBa.sub.xA)=(F.sub.dBK.sub.bP.sub.bB)(F.sub.dAK.sub.bP.sub.bA)[14], or
M(a.sub.xBa.sub.xA)=(F.sub.dBF.sub.bB)(F.sub.dAF.sub.bA)[15].
Furthermore, since this particular event is an acceleration-to-coasting event, the brake forces F.sub.bA, F.sub.bB and drive force F.sub.dB are zero resulting in the following equation:
M(a.sub.xBa.sub.xA)=F.sub.dA[16].
When considering the other events such as the acceleration-to-deceleration event depicted in FIG. 3, the brake force F.sub.bA and the drive force F.sub.dB are zero, thus:
M(a.sub.xBa.sub.xA)=F.sub.bBF.sub.dA[17]

(19) Furthermore, when applying the equation to a deceleration-to-acceleration event, the brake force F.sub.bB and the drive force F.sub.dA are zero, providing:
M(a.sub.xBa.sub.xA)=F.sub.dB+F.sub.bA[18].

(20) The method as depicted in the graphs 50, 66 of FIGS. 2 and 3 require several inputs from existing sensors or hardware which with vehicles are already equipped. The inputs for the method include total axle drive torque, brake pressure (or regenerative brake torques if the vehicle system 10 is so equipped), longitudinal acceleration, throttle pedal position, brake pedal position, and straight line driving detection. For example, the total axle drive torque is used to calculate the drive force F.sub.d. Brake pressure for each wheel 18 is required to calculate brake force F.sub.b. Straight line detection is required to rule out other dynamic force variables in the mass estimation calculation.

(21) Referring now to FIG. 5, a flowchart depicts a method 70 of estimating the mass M.sub.est of the vehicle system 10 as featured in the graphs 50, 66 of FIGS. 2 and 3. The method 70 includes a first step 72 for detecting if the vehicle system 10 ignition is on and the engine is running. A second step 74 of the method 70 initializes a variable M.sub.0 representing the most recent estimated mass M.sub.est in memory. A third step 76 detects if the vehicle system 10 is traveling in a straight line. If the vehicle system 10 is not traveling in a straight line, the third step 76 repeats until the vehicle system 10 is traveling in a straight line. Once the vehicle system 10 detects that the vehicle system 10 is traveling in a straight line, a fourth step 78 estimates the vehicle mass M.sub.1 using the equation [11] from above:
M.sub.1(a.sub.x+g)=F.sub.dK.sub.bP.sub.bK.sub.aV.sub.x.sup.2[11].

(22) A fifth step 80 of the method 70 detects if the number or data points at the set velocity V.sub.x has exceeded 1. If the number or data points at the set velocity V.sub.x has not exceeded 1, the fifth step 80 repeats until the number or data points at the set velocity V.sub.x has exceeded 1. This effectively detects when one of the three events occurs; the acceleration-to-deceleration event, the acceleration-to-coasting event, or the deceleration-to-acceleration event. Once the number or data points at the set velocity V.sub.x have exceeded 1, a sixth step 82 estimates the vehicle mass M.sub.2 using the equation [15] from above:
M.sub.2(a.sub.xBa.sub.xA)=(F.sub.dBF.sub.bB)(F.sub.dAF.sub.bA)[15].
A seventh step 84 sets a new estimated mass M.sub.est from estimated mass M.sub.0, M.sub.1, M.sub.2 from each of the second step 72, the fourth step 76, and the sixth step 82 each time the particular step is executed and a mass estimate M.sub.0, M.sub.1, M.sub.2 is calculated or initialized. An eighth step 86 outputs the estimated mass M.sub.est from the seventh step 84 to the vehicle control module. Once the sixth step 82 is executed a first time, the sixth step 82 repeats until the ignition of the vehicle system is turned off.

(23) The vehicle control module 21 is electronically connected to at least the powertrain 12 and sensors throughout the vehicle system 10 is preferably an electronic control device having a preprogrammed digital computer or processor, control logic, memory used to store data, and at least one I/O peripheral. The control logic includes a plurality of logic routines for monitoring, manipulating, and generating data. The vehicle control module 21 controls the operation of the powertrain 12 and other actuatable mechanisms of the vehicle system 10. The control logic may be implemented in hardware, software, or a combination of hardware and software. For example, control logic may be in the form of program code that is stored on the electronic memory storage and executable by the processor. The vehicle control module 21 receives the output signals of several sensors throughout the transmission and engine, performs the control logic and sends command signals to the vehicle system 10. The vehicle system 10 receives command signals from the vehicle control module 21 and converts the command signals to control actions operable in the vehicle system 10. Some of the control actions include but are not limited to increasing engine 22 speed, changing air/fuel ratio, changing transmission 24 gear ratios, altering suspension 16 control parameters, etc., among many other control actions.

(24) For example, a control logic implemented in software program code that is executable by the processor of the vehicle control module 21 includes control logic for implementing a method of estimating the mass M.sub.est of the vehicle system 10 as featured in the graphs 50, 66 of FIGS. 2 and 3. The control logic includes a first control logic for detecting if the vehicle system 10 ignition is on and the engine is running. A second control logic initializes a variable M.sub.0 representing the most recent estimated mass M.sub.est in memory. The third control logic detects if the vehicle system 10 is traveling in a straight line. If the vehicle system 10 is not traveling in a straight line, the third control logic repeats until the vehicle system 10 is traveling in a straight line. Once the vehicle system 10 detects that the vehicle system 10 is traveling in a straight line, the fourth control logic estimates the vehicle mass M.sub.1 using the equation [11] from above:
M.sub.1(a.sub.x+g)=F.sub.dK.sub.bP.sub.bK.sub.aV.sub.x.sup.2[11].
The fifth control logic detects if the number or data points at the set velocity V.sub.x has exceeded 1. If the number or data points at the set velocity V.sub.x has not exceeded 1, the fifth control logic repeats until the number or data points at the set velocity V.sub.x has exceeded 1. Once the number or data points at the set velocity V.sub.x have exceeded 1, a sixth control logic estimates the vehicle mass M.sub.2 using the equation [15] from above:
M.sub.2(a.sub.xBa.sub.xA)=(F.sub.dBF.sub.bB)(F.sub.dAF.sub.bA)[15].
A seventh control logic sets a new estimated mass M.sub.est from estimated mass M.sub.0, M.sub.1, M.sub.2 from each of the second control logic, the fourth control logic, and the sixth control logic each time the particular step is executed and a mass estimate M.sub.0, M.sub.1, M.sub.2 is calculated or initialized. An eighth control logic outputs the estimated mass M.sub.est from the seventh control logic to the vehicle control module. Once the sixth control logic is executed a first time, the sixth control logic repeats until the ignition of the vehicle system is turned off.

(25) Turning now to FIG. 4, a graph 90 presents a data set as generated by the operation of the method 70 depicted in FIG. 5. The graph 90 includes an x-axis 92 representing time (s) beginning with ignition of the engine 22 of the vehicle system 10. The y-axis 94 represents the mass of the vehicle (kg) both actual and estimated M.sub.est. The actual mass 96 of the vehicle system 10 is constant in this example. During the first seconds of ignition, the estimated mass M.sub.est is set to M.sub.0 or the most recent estimated mass M.sub.est prior to shutdown of the vehicle system 10. For the next approximately 280 seconds of ignition, the estimated mass M.sub.est is set to M.sub.1 and is shown having an error of approximately 25%. At approximately 300 s after ignition, the estimated mass M.sub.est is set to M.sub.2 which is shown have a significantly reduced error at less than 5%.

(26) The description of the disclosure is merely exemplary in nature and variations that do not depart from the gist of the disclosure are intended to be within the scope of the disclosure. Such variations are not to be regarded as a departure from the spirit and scope of the disclosure.