US-12617398-B2 - Vehicle deceleration control

US12617398B2US 12617398 B2US12617398 B2US 12617398B2US-12617398-B2

Abstract

A system includes a computer including a processor and a memory. The computer is programmed to determine a target location for a vehicle; based on a vehicle speed and a distance to the target location, determine a tunable acceleration parameter; determine a constraint, based on the tunable acceleration parameter, for a control barrier function to that outputs an acceleration to stop the vehicle at the target location; and upon solving the control barrier function to satisfy the constraint, actuate the vehicle to decelerate based on the acceleration output from the control barrier function.

Inventors

William Creighton
Michael Hafner
Andrew Fallon
Timothy Zwicky
Abhishek Sharma

Assignees

FORD GLOBAL TECHNOLOGIES, LLC

Dates

Publication Date: 20260505
Application Date: 20221219

Claims (20)

1 . A system comprising a computer including a processor and a memory, the memory storing instructions executable by the processor such that the computer is programmed to: determine a target location for a vehicle; based on a vehicle speed and a distance to the target location, determine a unitless tunable acceleration parameter; determine an acceleration constraint, based on the unitless tunable acceleration parameter, for a control barrier function that outputs an acceleration to stop the vehicle at the target location; and upon solving the control barrier function to satisfy the acceleration constraint, actuate the vehicle to decelerate based on the acceleration output from the control barrier function.
2 . The system of claim 1 , wherein the acceleration output specifies a negative acceleration.
3 . The system of claim 1 , wherein actuating the vehicle to decelerate includes one of actuating vehicle braking or vehicle propulsion.
4 . The system of claim 1 , wherein the constraint is further determined based on the vehicle speed and the distance to the target location.
5 . The system of claim 1 , wherein the instructions further include instructions to, after actuating the vehicle to decelerate based on the acceleration output from the control barrier function: determine a second vehicle speed and a second distance to the target location; determine a second constraint; compute a second acceleration output from the control barrier function to satisfy the second constraint; and actuate the vehicle to decelerate based on the second acceleration output from the control barrier function.
6 . The system of claim 1 , wherein the instructions further include instructions to actuate the vehicle to decelerate based on the acceleration output from the control barrier function only if actuating the vehicle is needed for the constraint to be satisfied.
7 . The system of claim 4 , wherein the instructions further include instructions to, after determining that actuating the vehicle is not needed for the constraint to be satisfied: determine a second vehicle speed and a second distance to the target location; determine a second tunable acceleration parameter based on the second vehicle speed and the second distance to the target location; determine a second constraint based on the second tunable acceleration parameter; compute a second acceleration output from the control barrier function to satisfy the second constraint; determine that actuating the vehicle to decelerate is needed for the second constraint to be satisfied; and actuate the vehicle to decelerate based on the second acceleration output from the control barrier function.
8 . The system of claim 1 , wherein the control barrier function includes the distance of the vehicle from the target location at a current time.
9 . The system of claim 8 , wherein the control barrier function includes a velocity of the vehicle at the current time.
10 . The system of claim 1 , wherein the control barrier function includes a maximum deceleration parameter.
11 . The system of claim 1 , wherein the control barrier function includes a buffer parameter.
12 . The system of claim 1 , wherein the target location is determined based on map data.
13 . The system of claim 1 , wherein the target location is determined based on vehicle sensor data.
14 . The system of claim 1 , wherein the instructions further include instructions to enter a standby mode of the system upon determining that the vehicle has stopped at the target location and then moved from the target location.
15 . A method, comprising: determining a target location for a vehicle; based on a vehicle speed and a distance to the target location, determining a unitless tunable acceleration parameter; determining an acceleration constraint, based on the unitless tunable acceleration parameter, for a control barrier function that outputs an acceleration to stop the vehicle at the target location; and upon solving the control barrier function to satisfy the acceleration constraint, actuating the vehicle to decelerate based on the acceleration output from the control barrier function.
16 . The method of claim 15 , further comprising, after actuating the vehicle to decelerate based on the acceleration output from the control barrier function: determining a second vehicle speed and a second distance to the target location; determining a second constraint; computing a second acceleration output from the control barrier function to satisfy the second constraint; and actuating the vehicle to decelerate based on the second acceleration output from the control barrier function.
17 . The method of claim 15 , further comprising actuating the vehicle to decelerate based on the acceleration output from the control barrier function only if actuating the vehicle is needed for the constraint to be satisfied.
18 . The method of claim 17 , further comprising, after determining that actuating the vehicle is not needed for the constraint to be satisfied: determining a second vehicle speed and a second distance to the target location; determining a second tunable acceleration parameter based on the second vehicle speed and the second distance to the target location; determining a second constraint based on the second tunable acceleration parameter; computing a second acceleration output from the control barrier function to satisfy the second constraint; determining that actuating the vehicle to decelerate is needed for the second constraint to be satisfied; and actuating the vehicle to decelerate based on the second acceleration output from the control barrier function.
19 . The method of claim 15 , wherein the control barrier function includes (a) the distance of the vehicle from the target location at a current time, and/or (b) a velocity of the vehicle at the current time.
20 . The method of claim 15 , wherein the control barrier function includes a maximum deceleration parameter.

Description

BACKGROUND Vehicles can operate in various autonomous or semi-autonomous modes in which one or more components such as a propulsion, a brake system, and/or a steering system of the vehicle are controlled by a vehicle computer. Various existing systems that can operate vehicle components include systems such as adaptive cruise control, which can control speed of a vehicle in certain situations, including by adapting the speed of the ego vehicle to one or more other vehicles; lane-centering, in which vehicle steering is controlled to maintain a lateral position of a vehicle in the lane of travel; and lane-changing, in which a vehicle steering, acceleration, and/or braking can be controlled to move a vehicle from one lane of travel to another. Such systems may be referred to as Advanced Driver Assistance Systems (ADAS). In some examples, an ADAS system can perform vehicle braking. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of an example vehicle system. FIG. 2 is a schematic diagram of an example traffic scene. FIG. 3 illustrates an example process for controlling vehicle deceleration. DESCRIPTION Referring initially to FIGS. 1 and 2, the present disclosure describes implementing a control barrier function (CBF) to control deceleration and/or stopping of a host vehicle 102 traveling on a roadway 205 toward a target location 220. A CBF is a statement of a mathematical relationship that includes one or more constraints to be satisfied. A CBF can be useful for determining an input to a control system when it is desired to constrain the input so that outputs from the control system will be appropriately limited. For example, as described herein, a CBF can be defined that models vehicle motion, including velocity, acceleration, and distance from a location such as a target location 220, and includes constraints related to deceleration requests input to a vehicle computer 104 to slow a vehicle as it moves toward, and stops at, a target location 220. Thus, the present implementation of a CBF advantageously controls vehicle deceleration so that deceleration is commanded in a manner that is effective to stop the vehicle 102 at a target location 220 and is designed to be efficient and comfortable for vehicle users. In short, implementation of a CBF as described herein can provide good vehicle operation, including control of vehicle acceleration and/or braking. (Note that herein, “acceleration” can mean positive acceleration, i.e., increasing velocity, or negative acceleration, i.e., decreasing velocity, also referred to as “deceleration.”). The present disclosure includes a system comprising a computer including a processor and a memory, the memory storing instructions executable by the processor such that the computer is programmed to: determine a target location for a vehicle; based on a vehicle speed and a distance to the target location, determine a tunable acceleration parameter; determine a constraint, based on the tunable acceleration parameter, for a control barrier function to that outputs an acceleration to stop the vehicle at the target location; and on solving the control barrier function to satisfy the constraint, actuate the vehicle to decelerate based on the acceleration output from the control barrier function. The acceleration output can specify a negative acceleration. Actuating the vehicle to decelerate can include one of actuating vehicle braking or vehicle propulsion. The constraint can be further determined based on the vehicle speed and the distance to the target location. The instructions can include instructions to, after actuating the vehicle to decelerate based on the acceleration output from the control barrier function: determine a second vehicle speed and a second distance to the target location; determine second constraint; compute a second acceleration output from the control barrier function to satisfy the second constraint; and actuate the vehicle to decelerate based on the second acceleration output from the control barrier function. The instructions can include instructions to actuate the vehicle to decelerate based on the acceleration output from the control barrier function only if actuating the vehicle is needed for the constraint to be satisfied. The instructions can further include instructions to, after determining that actuating the vehicle is not needed for the constraint to be satisfied, determine a second vehicle speed and a second distance to the target location; determine a second tunable acceleration parameter based on the second vehicle speed and the second distance to the target location; determine second constraint based on the second tunable acceleration parameter; compute a second acceleration output from the control barrier function to satisfy the second constraint; determine that actuating the vehicle to decelerate is needed for the second constraint to be satisfied; and actuate the vehicle to decelerate based on the second acceleration output from