Motor Output Control for Vehicle Turning Drivability
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Solution Overview
Problem
Existing vehicle systems experience deteriorated drivability during turns, especially when the energy storage device is at low capacity, leading to excessive discharging and potential damage, and compromised turning performance.
Innovation Solution
A vehicle system where left and right motors are controlled to maintain a maximum differential torque, with the motor control device limiting the difference between their motive forces based on the energy storage device's temperature or maximum output power, ensuring the sum of their forces remains zero to prevent excessive discharging and optimize turning performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If zero power control during turning is implemented to protect the energy storage device, then the energy storage device is protected from excessive discharging, but drivability during turning is deteriorated due to constant deceleration motive force
Solution Approach 1:
The control method dynamically adjusts the power distribution between left and right motors based on real-time vehicle state (turning direction, acceleration demand, energy storage capacity). Instead of fixed zero power control, the system adaptively modulates motor output to balance battery protection with driving performance requirements.
Solution Approach 2:
The system changes operational parameters (motor torque, power output) based on detected vehicle conditions. When energy storage capacity is sufficient, the system allows greater power differential for better drivability; when capacity is low, it restricts power differential to protect the battery, thus dynamically optimizing both protection and performance.
2Loss of energy
If maximum differential torque is controlled to protect the energy storage device, then excessive discharging is prevented, but turning performance is compromised
Solution Approach 1:
The system applies partial differential torque control rather than complete torque restriction. By allowing controlled differential torque within safe limits, the system achieves sufficient turning performance without causing excessive energy discharge that would damage the battery.
3Loss of energy
If the sum of left and right motor forces is controlled to zero, then energy storage device discharge is minimized, but acceleration capability during turning is reduced
Solution Approach 1:
The control system dynamically adjusts the sum of motor forces based on acceleration demands and battery state. When acceleration is needed and battery capacity allows, the system permits positive sum torque for acceleration; when battery is low on capacity, it restricts sum torque to minimal levels, thus dynamically balancing energy conservation with acceleration capability.
Data Source
AI summary
Provided is a vehicle in which overdischarge of a battery is protected and turning drivability of the vehicle is improved when there is even a little remaining capacity. An ECU controls the left motive force and the right motive force of the left electric motor and the right electric motor so as not to exceed a differential torque upper limit value, which is the maximum value of the difference between the left motive force and the right motive force established on the basis of the temperature or discharge limit power of the battery. When the battery is at a low temperature or the like and the discharge power is limited, the difference between the left motive force and the right motive force is controlled on the basis of the discharge limit power, whereby the turnability of the vehicle is improved while preventing the risk of damage to the battery.