Electric Vehicle Torque Control for Battery Voltage Limiting
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Solution Overview
Problem
Existing control techniques for electric vehicle batteries fail to prevent battery deterioration due to voltage and current exceeding limit levels during motor operation changes, leading to overcharge or overdischarge issues.
Innovation Solution
A control apparatus for electric vehicles that includes a request torque calculating unit, a motor control unit, and a torque suppression unit, which calculates and adjusts the motor torque to maintain battery voltage and current within safe limits by using feed forward and feedback control based on stored values of torque and rotational speed when limits are reached.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the electric motor operation is changed when the charging rate or battery current is near the limit value, then the motor performance can be improved, but the battery voltage or current exceeds the limit level causing battery deterioration
Solution Approach 1:
The control apparatus performs preliminary action by calculating the integrated value of motor torque and rotational speed in advance, and comparing it with the integrated value at the battery limit state before the battery voltage or current exceeds the limit level. This allows the system to proactively adjust motor operation to prevent battery deterioration while maintaining motor performance.
Solution Approach 2:
The control apparatus uses feedback control by continuously monitoring the integrated value of motor torque and rotational speed, comparing it with the stored integrated value at the battery limit state, and adjusting the motor torque accordingly. This closed-loop feedback ensures the battery operates within safe limits while maximizing motor performance.
2Power
If the battery charging or discharging rate is increased to meet power demand, then the power supply capability is improved, but the battery voltage falls below or exceeds the usable range causing over discharge or over charge
Solution Approach 1:
The control apparatus changes the parameter control strategy by using integrated values of torque and rotational speed instead of directly controlling battery voltage or current. This parameter transformation allows the system to manage power supply capability while maintaining battery voltage within the usable range, preventing overcharge and overdischarge conditions.
3Power
If the battery current limit is set high to improve power output, then the motor power is improved, but the battery may be deteriorated due to excessive current
Solution Approach 1:
The control apparatus introduces an intermediary control mechanism by using the integrated value of motor torque and rotational speed as a mediator between motor power requirements and battery current limits. This intermediary parameter allows the system to achieve high motor power output while preventing excessive battery current that would cause deterioration.
Data Source
AI summary
A control apparatus of an electric vehicle, which is operable to be driven by supplying electric power from a battery to an electric motor to drive the electric motor and operable to perform regeneration charge, includes: a request torque calculating unit calculating a request torque of the electric motor; a motor control unit controlling the electric motor based on the request torque; and a torque suppression unit performing a feed forward control for setting the request torque based on a rotational angular speed of the electric motor so that an integrated value of a torque and a rotational angular speed of the electric motor at time when the electric motor is driven or the regeneration charge is performed is identical to an integrated value of the torque and the rotational angular speed stored at a point of time when the battery voltage or the battery current reaches the limit level.