Vehicle Travel Control Using Motor Torque for Low-Speed Wheel Estimation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing vehicle control systems struggle to accurately detect wheel speed at extremely low speeds, leading to inaccurate slip rate calculation and compromised control accuracy in slip control, crawl control, and reverse travel prevention, especially on low-friction surfaces.
Innovation Solution
A traveling control apparatus and program that estimates wheel speed using motor rotation speed and torque, calculating slip rate and friction coefficient to enhance control accuracy at low speeds, employing a wheel speed estimation unit, slip rate calculation unit, and friction coefficient estimation unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pulse-generated type wheel speed sensor is used to detect wheel speed, then wheel speed detection is possible at normal speeds, but detection fails at extremely low speeds around 1km/hour where traveling speed pulses are not generated
Solution Approach 1:
The patent introduces motor rotation speed as an intermediary parameter to estimate wheel speed when direct detection fails. The estimation unit uses the relationship between motor rotation speed and wheel speed, combined with torque information, to calculate wheel speed indirectly through this mediator parameter.
Solution Approach 2:
The patent replaces the mechanical pulse generation method with an estimation system based on motor control parameters. Instead of relying on mechanical pulse generation from wheel rotation, the system substitutes a calculation-based approach using motor rotation speed and torque to determine wheel speed.
2Measurement precision
If slip rate is calculated using the equation (vehicle body speed - wheel speed) / vehicle body speed, then slip rate can be calculated at normal speeds, but zero-division error occurs when vehicle body speed is substantially zero
Solution Approach 1:
The patent creates a copy of the wheel speed parameter through estimation rather than direct measurement. The estimation unit generates a virtual wheel speed value based on motor parameters that can be used in slip rate calculations, avoiding the zero-division problem by providing a valid denominator even when actual vehicle speed is near zero.
3Manufacturing precision
If fine slip control is performed to prevent tire slip during vehicle start, then control accuracy is improved, but accurate control cannot be achieved when wheel speed detection is inaccurate at extremely low speeds
Solution Approach 1:
The system uses self-service by utilizing motor rotation speed and torque information that are already available from the motor control system to estimate wheel speed. This eliminates the need for separate low-speed detection hardware, allowing the system to serve its own measurement needs using existing control parameters.
4Adaptability or versatility
If crawl control is performed to maintain constant extremely low speed on offroad, then vehicle control capability is improved, but control accuracy deteriorates when wheel speed is not detected accurately
Solution Approach 1:
The patent implements feedback control by continuously comparing the estimated wheel speed with the target crawl speed and adjusting motor torque accordingly. The estimation unit provides real-time feedback on actual wheel speed, enabling closed-loop control that maintains accurate constant speed operation on offroad surfaces.
5Reliability
If reverse travel prevention control is performed using regenerative braking, then vehicle safety is improved, but control accuracy deteriorates when wheel speed detection is inaccurate at low speeds
Solution Approach 1:
The patent uses motor rotation speed as an intermediary parameter to detect reverse motion. By monitoring changes in motor rotation speed and direction, the system can identify reverse travel attempts and apply regenerative braking control, providing accurate safety monitoring without relying on failed pulse-based wheel speed sensors.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A traveling control apparatus (10) of a vehicle (100) that travels by transmitting force of a driving motor (89, 90) to tires (111, 112, 121, 122) is provided, including: a rotation speed detection unit (91, 92) that detects a motor rotation speed of the driving motor; a torque calculation unit (11) that calculates a motor torque generated at the driving motor; and a wheel speed estimation unit (20) that estimates, based on the motor rotation speed detected by the rotation speed detection unit and the motor torque calculated by the torque calculation unit, a wheel speed which is a rotation speed of the tires.