Four wheel steering angle constraints
AssigneeZoox, Inc.
InventorsZachary Stuart Churukian, David Evan Zlotnik, Joseph Funke
Life of this patent
Estimating the term…
Abstract
Four-wheel steering of a vehicle, e.g., in which leading wheels and trailing wheels are steered independently of each other, can provide improved maneuverability and stability. Steering angle constraints may be used to limit or prevent saturation of steering by only one set of wheels as well as to reduce sideslip. The steering angle constraints are vehicle independent and applicable across a fleet of different vehicles based on vehicle speed. For instance, the steering angle constraints establish angle limits that dynamically adjust based on vehicle speed to ensure vehicle velocity and acceleration remain within predefined limits as established by autonomous vehicle system design.
Claims20
An autonomous vehicle, comprising:
- one or more processors;
- and
- memory storing instructions that, when executed by the one or more processors, cause the autonomous vehicle to perform actions comprising:
- determining a first curvature function defining a path curvature of the autonomous vehicle as a function of a speed for the autonomous vehicle based on an operational domain;
- determining a first curvature rate function defining an allowable change in curvature as a function of speed for the autonomous vehicle based on the operational domain;
- determining a second curvature function by reducing a limit of the first curvature function, the limit of the first curvature function being reduced at least in part in response to determining that a slope of the first curvature function at a first speed of the autonomous vehicle exceeds a value of the first curvature rate function at the first speed of the autonomous vehicle;
- generating steering limit data for the autonomous vehicle at least in part by:
- determining an angle limit for a steering angle based at least in part on the second curvature function;
- and
- controlling, based at least in part on the steering limit data, the autonomous vehicle.
A method, comprising:
- determining a first curvature function defining a path curvature of a moving vehicle as a function of a speed for the moving vehicle;
- determining a first curvature rate function defining a first curvature rate as a change in curvature as a function of speed for the moving vehicle;
- determining a second curvature function by reducing a limit of the first curvature function, the limit of the first curvature function being reduced at least in part in response to determining that a slope of the first curvature function at a first speed of the moving vehicle exceeds a value of the first curvature rate function at the first speed of the moving vehicle;
- generating steering limit data for the moving vehicle by at least:
- determining an angle limit for a steering angle based at least in part on the first curvature function;
- and
- controlling, based at least in part on the steering limit data, at least one of leading wheels of the moving vehicle or trailing wheels of the moving vehicle.
A non-transitory computer-readable medium storing instructions that, when executed by one or more processors, cause the one or more processors to perform actions comprising:
- determining a first curvature function defining a path curvature of a moving vehicle as a function of a speed for the moving vehicle;
- determining a first curvature rate function defining a first curvature rate as a change in curvature as a function of speed for the moving vehicle;
- determining a second curvature function by reducing a limit of the first curvature function, the limit of the first curvature function being reduced at least in part in response to determining that a slope of the first curvature function at a first speed of the moving vehicle exceeds a value of the first curvature rate function at the first speed of the moving vehicle;
- generating steering limit data for the moving vehicle by at least:
- determining an angle limit for a steering angle based at least in part on the first curvature function;
- and
- controlling, based at least in part on the steering limit data, at least one of leading wheels of the moving vehicle or trailing wheels of the moving vehicle.
Dependencies are inferred from the claim text.