Autonomous Vehicle Braking Control via Wheel Pulse Counting
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Solution Overview
Problem
Current motor vehicle systems face challenges in accurately determining speed and acceleration at low speeds for fully automated parking and maneuvering functions, as rotational speed sensors provide insufficient signal pulses, leading to unreliable movement tracking and potential overshooting of the destination.
Innovation Solution
The method utilizes rotational speed sensor signal pulses to control the braking system, reducing braking force until a first pulse is detected, then holding it constant and increasing it based on counted pulses to precisely track and complete short path driving maneuvers, such as parking, by converting pulse numbers into traveled distance and adjusting torque to prevent rolling back on inclines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rotational speed sensors are used to determine speed and acceleration at low speeds, then the system can provide speed and acceleration signals for autonomous driving functions, but the number of signal pulses is insufficient leading to unreliable movement tracking
Solution Approach 1:
The patent introduces an intermediary calculation method that uses the known distance between signal pulses (1-2 cm) as a reference unit. By counting pulses and multiplying by this known distance, the system indirectly determines traveled path, speed, and acceleration without directly measuring them, thereby achieving reliable tracking even with few pulses
Solution Approach 2:
The patent replaces traditional mechanical speed and acceleration sensors with a pulse-counting-based calculation system. Instead of using dedicated speed/acceleration sensors that require multiple pulses for accurate measurement, the system substitutes a microcontroller-based calculation that derives these parameters from position pulse data
2Speed
If the number of signal pulses is small at low speeds, then the system can operate at low speeds for parking maneuvers, but reliable speed determination requires a long traveled path which causes travel past the destination
Solution Approach 1:
The patent implements continuous feedback by counting each signal pulse and comparing the cumulative traveled path against the target destination. The microcontroller monitors the pulse count in real-time and can trigger braking when the calculated path approaches the destination, preventing overshooting even at very low speeds where traditional methods would require excessive distance for accurate measurement
3Speed
If braking force is held constant after the first signal pulse, then the vehicle can maintain low speed for precise positioning, but the vehicle may roll back on inclines
Solution Approach 1:
The patent applies preliminary action by pre-calculating and applying an increased braking force before the vehicle begins moving on inclines. The system detects the incline condition in advance and compensates by increasing brake force, preventing rollback before it occurs rather than reacting after the vehicle starts moving
Solution Approach 2:
The patent dynamically changes the braking force parameter based on detected incline conditions. When an incline is detected, the system increases the braking force parameter beyond the standard holding force to compensate for gravitational effects, thereby maintaining position stability while still allowing low-speed operation
Data Source
AI summary
A method for operating a motor vehicle having partial/full autonomous driving, having a plurality of wheels, a drive system for producing a drive torque at at least one of the wheels, and a brake system for producing at least one holding force for holding still at least one of the wheels, a rotational speed sensor being allocated to at least one of the wheels, which sensor produces a respective signal pulse for each of a plurality of positions of angular rotation of the associated wheel, a specifiable driving maneuver being performed as a function of the produced signal pulses. For a short path driving process starting from a standstill, the brake force is reduced until the rotational speed sensor produces a first signal pulse, and is then held at least temporarily constant until a specified number of signal pulses is produced, and subsequently is increased up to the holding force.