System and method for optimizing downshifting of a transmission during vehicle deceleration
First Claim
1. A method of selecting a gear ratio of a transmission in a motor vehicle to produce an increase in negative input torque, the transmission including a controller and N automatically selectable gear ratios, comprising:
- measuring a current road grade with a sensing device and communicating the current road grade measurement to the controller;
receiving by the controller a signal corresponding to a service brake input from the vehicle;
determining by the controller a desired maximum acceleration limit of the vehicle based on the current road grade and service brake input signal;
calculating by the controller a predicted vehicle acceleration based on the current road grade and an estimated vehicle mass;
determining by the controller a current vehicle acceleration, wherein the current vehicle acceleration is determined by calculating by the controller the current vehicle acceleration or by measuring by the controller a vehicle acceleration through a sensing device;
computing by the controller an estimated required tractive braking effort and estimated tractive braking effort for at least one of the N automatically selectable gear ratios of the transmission; and
selecting by the controller one gear ratio of the N automatically selectable gear ratios for operation of the transmission based on a comparison of the estimated required tractive braking effort and estimated tractive braking effort.
1 Assignment
0 Petitions
Accused Products
Abstract
A method of selecting a gear ratio of a transmission. The method includes measuring a current road grade with a sensing device and communicating the current road grade measurement to the controller. The controller receives a signal corresponding to a service brake input and determines a desired maximum acceleration limit of the vehicle. The method also includes calculating a predicted vehicle acceleration, measuring a current vehicle acceleration, and calculating an error value as a function of the predicted vehicle acceleration and measured vehicle acceleration. The method also computes an estimated required tractive braking effort and estimated tractive braking effort for at least one of N automatically selectable gear ratios of the transmission and selects one gear ratio of the N automatically selectable gear ratios for the operation of the transmission based on a comparison of the estimated required tractive braking effort and estimated tractive braking effort.
24 Citations
20 Claims
-
1. A method of selecting a gear ratio of a transmission in a motor vehicle to produce an increase in negative input torque, the transmission including a controller and N automatically selectable gear ratios, comprising:
-
measuring a current road grade with a sensing device and communicating the current road grade measurement to the controller; receiving by the controller a signal corresponding to a service brake input from the vehicle; determining by the controller a desired maximum acceleration limit of the vehicle based on the current road grade and service brake input signal; calculating by the controller a predicted vehicle acceleration based on the current road grade and an estimated vehicle mass; determining by the controller a current vehicle acceleration, wherein the current vehicle acceleration is determined by calculating by the controller the current vehicle acceleration or by measuring by the controller a vehicle acceleration through a sensing device; computing by the controller an estimated required tractive braking effort and estimated tractive braking effort for at least one of the N automatically selectable gear ratios of the transmission; and selecting by the controller one gear ratio of the N automatically selectable gear ratios for operation of the transmission based on a comparison of the estimated required tractive braking effort and estimated tractive braking effort. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
-
10. A system for selecting a gear ratio for operably decelerating a motor vehicle, comprising:
-
a transmission having a plurality of automatically selectable gear ratios; a transmission control circuit configured to control operation of the transmission; a sensing device electrically coupled to the transmission control circuit, the sensing device configured to measure road grade; an engine control circuit configured to control operation of an internal combustion engine operatively coupled to the transmission; and a data link established between the transmission control circuit and engine control circuit; wherein the transmission control circuit includes a memory having instructions stored therein that are executable by the transmission control circuit to enable an autobrake preselect logic, determine a desired maximum acceleration limit of the vehicle as a function of road grade, calculate a predicted vehicle acceleration as a function of road grade and an estimated vehicle mass, calculate a difference between the predicted vehicle acceleration and actual vehicle acceleration, compute an estimated required tractive braking effort and estimated tractive braking effort for at least one of the plurality of automatically selectable gear ratios and select a gear ratio from the plurality of gear ratios for operation of the transmission based on a comparison of the estimated required tractive braking effort and estimated tractive braking effort. - View Dependent Claims (11, 12, 13)
-
-
14. A method of controlling a transmission in a motor vehicle, comprising:
-
providing N automatically selectable gear ratios of the transmission, the N automatically selectable gear ratios including a minimum gear ratio RMin and a maximum gear ratio RMax, a transmission control circuit for operably controlling the transmission, an internal combustion engine operably producing input torque to the transmission, an engine control circuit for operably controlling the engine, a data link establishing electrical communication between the engine control circuit and the transmission control circuit, and an engine brake operably coupled to the engine; receiving by the transmission controller circuit a first signal from a throttle position sensor corresponding to a position of an accelerator pedal, a second signal from the engine brake corresponding to an engine brake status, and a third signal corresponding to a cruise control status; determining by the transmission controller circuit an autobrake preselect state as a function of a comparison of the first signal to a first threshold, the second signal to a second threshold, and the third signal to a third threshold; measuring grade with a sensing device and communicating the grade measurement to the transmission control circuit; receiving by the transmission controller circuit a fourth signal corresponding to a service brake input from the vehicle; determining by the transmission controller circuit a desired maximum acceleration limit of the vehicle based on the measured grade and fourth signal; calculating by the transmission controller circuit a predicted vehicle acceleration based on the grade and an estimated vehicle mass; measuring a current vehicle acceleration; calculating by the transmission controller circuit an acceleration difference between the predicted vehicle acceleration and the current vehicle acceleration; computing by the transmission controller circuit an estimated required tractive braking effort based on the estimated vehicle mass, the desired maximum acceleration limit, the grade measurement, and the acceleration difference; determining by the transmission controller circuit a current gear ratio, C, from the N automatically selectable gear ratios of the transmission; calculating by the transmission controller circuit an estimated tractive braking effort for each automatically selectable gear ratio from C to RMax until the estimated required tractive braking effort is approximately equal to or greater than the calculated estimated tractive braking effort; selecting by the transmission controller circuit a desired gear ratio between C and RMax that corresponds to the estimated required tractive braking effort being equal to or greater than the calculated estimated tractive braking effort; and controlling by the transmission controller circuit shifting from C to the desired gear ratio for the operation of the transmission if the desired gear ratio is different from C. - View Dependent Claims (15, 16, 17, 18, 19, 20)
-
Specification