Torque Distribution Control for Four-Wheel Drive Vehicles
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Solution Overview
Problem
The existing electrically-controlled torque distribution systems in four-wheel drive vehicles exhibit hysteresis characteristics, leading to variations in torque transmission capacity when the input current is maintained at a constant value, affecting the accuracy of torque distribution between front and rear wheels.
Innovation Solution
A method and apparatus that temporarily increase and then return the input current to the torque distribution device to match the target torque distribution amount, repeating this process at intervals, to correct for hysteresis and maintain accurate torque distribution based on the vehicle's running state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an electrically-controlled torque distribution device is used to control torque distribution between front and rear wheels, then the torque distribution can be adjusted according to running state, but hysteresis occurs in the torque transmission capacity when input current is maintained at the same value
Solution Approach 1:
The patent applies periodic action by repeatedly increasing the input current to the torque distribution device at predetermined intervals. This periodic current increase compensates for the hysteresis effect in the electromagnetic coupling, ensuring that the torque transmission capacity remains stable and predictable despite the inherent hysteresis characteristics of the device.
2Reliability
If the input current to the torque distribution device is increased to compensate for hysteresis, then the torque transmission capacity becomes more stable, but the control precision for maintaining target torque distribution is reduced
Solution Approach 1:
The patent employs feedback control by continuously monitoring the actual torque distribution and comparing it with the target torque distribution. Based on this feedback, the control device adjusts the input current to the torque distribution device, including periodic increases to compensate for hysteresis, thereby maintaining both stability and precision in torque distribution control.
3Speed
If the torque distribution device uses electromagnetic coupling for electrical control, then the system response speed is improved, but hysteresis characteristics cause variations in torque transmission capacity
Solution Approach 1:
The patent applies preliminary action by proactively increasing the input current at predetermined intervals before hysteresis causes significant torque transmission variations. This preventive measure ensures that the electromagnetic coupling maintains consistent torque transmission capacity throughout operation, compensating for hysteresis effects before they manifest as performance degradation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively suppresses the hysteresis effect, enhancing the accuracy of torque distribution and improving vehicle performance, stability, and fuel economy by ensuring optimal torque distribution according to the vehicle's speed, steering angle, and wheel slip state.
Implementation Method 1
a torque distribution device composed, for example, of an electromagnetic coupling disposed in a driving force transmission path for transmitting torque to the secondary driven wheels therethrough and adapted to be electrically controlled
Implementation Method 2
a characteristic of torque transmission capacity with respect to input current applied thereto is different between when a current value of the input current is increasing as indicated by the curve A and when the current value is decreasing as indicated by the curve B, i.e., a so-called hysteresis occurs
Data Source
AI summary
Discloses is a method of controlling a four-wheel drive vehicle equipped with a torque distribution device capable of changing a torque distribution amount for secondary driven wheels according to an input current to be applied thereto. This method comprises the steps of: applying, to the torque distribution device, a current value corresponding to a target torque distribution amount; and, performing a current changing control for increasing and reducing the input current to the torque distribution device. The step of performing a current changing control includes causing the input current to the torque distribution device to be temporarily increased to a value greater than the current value corresponding to the target torque distribution amount, and then returned to the current value corresponding to the target torque distribution amount, and repeating the temporary increasing of the input current at least at intervals of a predetermined time.