Vehicle Driving Force Control for Smooth Hill Starts
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Solution Overview
Problem
Vehicles equipped with mechanisms to hold braking force before starting may experience sudden starting when the order of range switching and accelerator pedal operation is reversed, leading to concerns about insufficient driving force for starting on slopes and potential backward movement on uphill roads.
Innovation Solution
A driving force control method that includes a control unit to limit the upper limit of the driving force to a value larger than the holding threshold but smaller than the required driving force when switching from the stopping range to the starting range, using a holding device to manage braking force and prevent sudden starts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the holding threshold value is decreased to allow vehicle starting, then the vehicle can start on slopes, but the vehicle may move backward on uphill roads due to insufficient driving force
Solution Approach 1:
The patent applies dynamics by making the holding threshold value variable rather than fixed. The control unit dynamically adjusts the holding threshold based on detected vehicle states (accelerator pedal position, vehicle speed, brake operation) to match the actual driving conditions. This allows the threshold to be lowered for starting on slopes while maintaining higher thresholds for uphill driving, resolving the contradiction between starting reliability and preventing backward movement.
Solution Approach 2:
The patent changes the parameter of the holding threshold value based on different operating conditions. By detecting accelerator pedal position, vehicle speed, and brake operation state, the system adjusts the holding threshold parameter to appropriate levels - lower when starting is needed, higher when uphill driving is detected - thus resolving the contradiction between needing low threshold for starting and high threshold for preventing rollback.
2Ease of operation
If the driving force is limited to prevent sudden starting, then sudden acceleration is suppressed, but the driving force may be insufficient to release the holding braking force and start the vehicle
Solution Approach 1:
The patent applies dynamics by dynamically adjusting the driving force limitation based on the accelerator pedal position and vehicle state. When the accelerator pedal is fully depressed and starting conditions are met, the system temporarily increases the driving force beyond the normal limitation to ensure the holding brake is released. After brake release, the normal limitation is reapplied to maintain smooth operation. This dynamic adjustment resolves the contradiction between smooth operation and sufficient starting power.
3Reliability
If the holding device releases braking force when driving force exceeds threshold, then vehicle starting is enabled, but sudden starting occurs when range switching and accelerator operation order is reversed
Solution Approach 1:
The patent applies preliminary action by having the control unit detect and identify abnormal operation patterns (reversed order of range switching and accelerator depression) before the vehicle actually starts. When such abnormal operation is detected, the system preemptively applies driving force limitation to prevent sudden acceleration. This preliminary detection and prevention resolves the contradiction between reliable brake release and preventing sudden starting.
Solution Approach 2:
The patent uses feedback by continuously monitoring the sequence of driver operations (range switching timing relative to accelerator depression) and using this information to adjust the driving force control strategy. When abnormal operation sequence is detected through feedback, the system activates limitation control; when normal sequence is detected, full driving force is permitted. This feedback mechanism resolves the contradiction between brake release reliability and sudden starting prevention.
Data Source
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AI summary
When an accelerator pedal operation amount is large enough to generate a driving force after switching from a stopping range to a starting range is performed, in order to prevent a sudden starting immediately after the range switching, an upper limit of the driving force of a driving source is limited to a driving force larger than a holding threshold value for releasing holding of a stopping state of a vehicle and smaller than a required driving force based on the accelerator pedal operation amount.