Brake control method based on a linear transfer function reference model
First Claim
1. A brake control method for a vehicle comprising the steps of:
- measuring a longitudinal speed and steering angle of the vehicle;
determining an un-damped natural frequency, a damping ratio and zeros for first and second transfer functions respectively describing ratios of vehicle yaw rate and lateral velocity to vehicle steering angle as a function of vehicle speed for linear operation of the vehicle;
computing a desired yaw rate as a function of the measured longitudinal speed and steering angle, and the determined un-damped natural frequency, damping ratio, and the zero of the first transfer function;
computing a desired lateral velocity as a function of the measured longitudinal speed and steering angle, and the determined undamped natural frequency, damping ratio, and the zero of the second transfer function;
computing a desired lateral acceleration based on said desired lateral velocity and yaw rate and said measured vehicle speed;
measuring a lateral acceleration and yaw rate of said vehicle, and forming a yaw rate command for said vehicle based at least in part on a first deviation between said desired and measured yaw rates, and a second deviation between said desired and measured lateral accelerations; and
differentially braking wheels of said vehicle to impart a yaw moment corresponding to said yaw rate command.
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Accused Products
Abstract
An active brake control method including an improved method of developing the desired state variables, enabling the system designer to specify the damping ratio and the un-damped natural frequency of desired vehicle performance. The desired state variables are determined by converting a linear time domain model into a transfer function model and solving for the lateral velocity and yaw rate as a function of the driver steering angle, the damping ratio, the un-damped natural frequency of the vehicle, and the transfer function zeros. The damping ratio, the un-damped natural frequency of the vehicle, and the transfer function zeros may either be computed or specified in a look-up table as a function of vehicle speed. This allows the system designer to provide increased damping at high vehicle speeds, for example.
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Citations
8 Claims
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1. A brake control method for a vehicle comprising the steps of:
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measuring a longitudinal speed and steering angle of the vehicle; determining an un-damped natural frequency, a damping ratio and zeros for first and second transfer functions respectively describing ratios of vehicle yaw rate and lateral velocity to vehicle steering angle as a function of vehicle speed for linear operation of the vehicle; computing a desired yaw rate as a function of the measured longitudinal speed and steering angle, and the determined un-damped natural frequency, damping ratio, and the zero of the first transfer function; computing a desired lateral velocity as a function of the measured longitudinal speed and steering angle, and the determined undamped natural frequency, damping ratio, and the zero of the second transfer function; computing a desired lateral acceleration based on said desired lateral velocity and yaw rate and said measured vehicle speed; measuring a lateral acceleration and yaw rate of said vehicle, and forming a yaw rate command for said vehicle based at least in part on a first deviation between said desired and measured yaw rates, and a second deviation between said desired and measured lateral accelerations; and differentially braking wheels of said vehicle to impart a yaw moment corresponding to said yaw rate command. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A brake control method for a vehicle comprising the steps of:
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measuring a longitudinal speed and steering angle of the vehicle; determining an un-damped natural frequency, a damping ratio and zeros for first and second transfer functions respectively describing ratios of vehicle yaw rate and lateral velocity to vehicle steering angle as a function of vehicle speed for linear operation of the vehicle; computing a desired yaw rate as a function of the measured longitudinal speed and steering angle, and the determined un-damped natural frequency, damping ratio, and the zero of the first transfer function; computing a desired lateral velocity and the vehicle side slip angle as a function of the measured longitudinal speed and steering angle, and the determined un-damped natural frequency, damping ratio, and the zero of the second transfer function; computing a desired lateral acceleration based on said desired lateral velocity and yaw rate and said measured vehicle speed; measuring a lateral acceleration and yaw rate of said vehicle, and forming a yaw rate command for said vehicle based at least in part on a first deviation between said desired and measured yaw rates, and a second deviation between said desired and measured lateral accelerations; estimating the actual vehicle side slip angle, and forming a slip angle command for said vehicle based on the deviation between the desired and estimated slip angle; and differentially braking wheels of said vehicle to impart a yaw moment corresponding to a weighted sum of said yaw rate and slip angle commands.
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Specification