Vehicle Driving Force Control for Turning Radius Stability
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Solution Overview
Problem
Existing driving force control systems for vehicles fail to reliably maintain a target turning radius, leading to inadequate turning performance due to changes in vehicle orientation and understeer, which prevents the actual yaw rate from aligning with the target yaw rate.
Innovation Solution
A driving force control apparatus that includes a turning radius estimating unit, a target slip angle computing unit, and a driving force control unit, which computes target rotational speeds for the wheels based on the estimated turning radius and vehicle speed, allowing independent control of driving forces to the right and left wheels to achieve the target rotational speeds, thereby stabilizing the turning performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If control is executed by causing the actual yaw rate to approach the target yaw rate, then the turning performance can be improved by transmitting higher driving force to outer wheels, but the actual yaw rate coincides with target yaw rate only when vehicle orientation changes, preventing reliable turning radius control
Solution Approach 1:
The patent changes the control parameter from yaw rate to rotational speed of wheels. By computing target rotational speeds based on steering angle and vehicle speed, and controlling actual rotational speeds to match targets, the system achieves reliable turning radius control that is not affected by vehicle orientation changes. This parameter transformation resolves the contradiction by providing stable, predictable control behavior.
2Reliability
If feedback control is used to cause actual yaw rate to approach target yaw rate, then turning performance is improved, but the control cannot execute when understeer occurs and turning radius deviates from target
Solution Approach 1:
The patent computes target rotational speeds in advance based on steering angle and vehicle speed before executing control. By determining the desired rotational speeds beforehand and controlling actual speeds to match these pre-computed targets, the system ensures accurate turning radius control even during understeer conditions where yaw rate feedback would fail.
3Reliability
If independent control of driving forces to right and left wheels is implemented, then turning performance is enhanced, but device complexity increases with additional clutch mechanisms
Solution Approach 1:
The patent employs feedback control by computing the difference between target rotational speeds and actual rotational speeds of wheels, then adjusting driving forces to eliminate this difference. This feedback mechanism enables precise independent control of wheel driving forces without requiring complex mechanical adjustment mechanisms, resolving the contradiction between control precision and device complexity.
Data Source
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AI summary
A driving force control apparatus includes: a turning radius estimating unit that estimates a turning radius of a four-wheel-drive vehicle; a target slip angle computing unit that computes a target slip angle at the time of turning of the four-wheel-drive vehicle, on the basis of the estimated turning radius; a target rotational speed computing unit that computes target rotational speeds of right and left rear wheels of the four-wheel-drive vehicle, on the basis of the estimated turning radius, the computed target slip angle, and a vehicle speed; and a driving force control unit that controls driving forces that are transmitted to the right and left rear wheels such that actual rotational speeds of the right and left rear wheels approach the computed target rotational speeds.